Terence Hughes and George Denton

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ORAL HISTORIES
Interviewed by
Will Thomas
Interview date
Location
University of Maine at Orono
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Interview of Terence Hughes & George Denton by Will Thomas on November 19, 2008,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/48408

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Abstract

This interview was conducted first solely with Terry Hughes, then a brief segment with both Hughes and George Denton, and finally a segment with only Denton. It is part of a series of interviews done documenting the history of scientific work on the West Antarctic Ice Sheet (WAIS), and it concentrates primarily on Hughes’s career. It briefly covers his upbringing in South Dakota and undergraduate education in metallurgy at the South Dakota School of Mines and Technology, and discusses his introduction into glaciology through Johannes Weertman, while doing graduate work in metallurgy at Northwestern University. The interview moves on to field work in Antarctica as a research associate under Colin Bull, subsequent employment at the Institute of Polar Studies at The Ohio State University, and production of his ISCAP Bulletins outlining the possibility that WAIS might disintegrate. Hughes’s move to the University of Maine as part of the CLIMAP project and his association with Denton and Hal Borns, are discussed. There is a focus on Hughes and Denton’s identification in The Last Great Ice Sheets of marine portions of ice sheets as playing a crucial role in the destruction of past ice sheets, as well as their identification of Pine Island and Thwaites Glaciers as a potential outlet for rapid ice loss from WAIS. There is also discussion of early attention to the WAIS disintegration problem circa 1980 and Hughes’s distance from subsequent research on ice streams. Denton describes field work in reconstructing past climate conditions, including the contributions of John Mercer.

Transcript

Thomas:

This is Will Thomas. I’m at the University of Maine at Orono. I’m speaking with Terry Hughes today about the history of the science and scientific assessments of the West Antarctic Ice Sheet. It’s November 19, 2008. So, why don’t we just begin by going over a little bit of your personal background: where you’re from, how you got interested in science in the first place, and then we can move on from there.

Hughes:

Well, I came into glaciology in an indirect way. I was raised on the Hughes’s cattle ranch in South Dakota, which my grandfather got started in 1880 when he went out there at age 19. Of course, it’s where Bad River comes into the Missouri River right in the middle of the state. The capital city, Pierre, appears directly across the Missouri River from Bad River as it passes through the little town of Fort Pierre, where I went to school. That spot had been a permanent Indian village that Lewis and Clark went through, and the Verendrye brothers in 1743 stopped there and buried a lead plaque on the hill that student classmates of my father found in the early 1900s, claiming all that for France. Bad River comes out of the South Dakota Badlands. Directly across the Missouri, as a boy I saw all these boulders scattered over the countryside, and we knew it was deposited by big ice sheets that had come down from Canada. So, that was my only exposure to glaciology when I was growing up.

I went to school at the South Dakota School of Mines and Technology and got a bachelor’s degree in metallurgy. Then I went to Northwestern and got master’s and doctoral degrees in materials science, which was metallurgy expanded to include ceramics and polymers. One of the professors there in the Materials Science Department was Hans Weertman, who, as a separate area of study of his, wrote a number of theoretical papers on glaciology. He didn’t teach a course in that while I was there. But I found a book called Those Astounding Ice Ages in the library, which is a short distance from the building housing our department, and read it. Kind of a crazy explanation for ices ages. I showed it to Weertman. It was a good read. He was a retired architect who spent three weeks up in Alaska on a glacier, came down like Moses from Sinai, thinking he had the answer to the riddle of the ice ages and couldn’t get it published, so he published it in the vanity press and sent copies around to various universities. Northwestern got one of them. I saw it collecting dust and I checked it out. I read it and showed it to Weertman, and he gave me some reprints of his papers, giving a more scientific explanation of how ice ages got started, with the big continental ice sheets. And then I took off—

Thomas:

Sorry, the theory, who was that?

Hughes:

Oh, Dolph Earl Hooker was the author of Those Astounding Ice Ages, and he was a retired architect at the time he wrote that. He thought that the Earth had originally an atmosphere like the outer planets that obscured the surface from the sun, and the major component of that atmosphere was ice crystals, and the rotation of the Earth causes slight polar flattening, so that would pull down these ice crystals that were arranged in belts like the gas belts around Saturn and Jupiter. So, with each belt that got pulled down you had an ice age, because it came down as ice crystals in high latitudes and rain in the middle latitudes. And of course, he tied up the Genesis flood with the last rain to come down. That was the last of these belts, and then it had the atmosphere it’s got today, and you can see the sun for the first time because it wasn’t a completely overcast sky. So, that was a scientific demonstration of God’s promise to Noah that he wouldn’t destroy the Earth by deluge again—couldn’t, there wasn’t that much water vapor up there anymore. So, it was off the wall, but it was a good read.

Thomas:

It reminds me of 18th-century natural philosophical cosmologists.

Hughes:

I think I took it to South Dakota this summer, but it’s a book I had up here for years in my collection. I wrote Hooker, and I asked him… couldn’t get it, you know, because it’s vanity press and it’s years earlier. But he sent me one. He probably had a garage full of these things, and so I had it. So, that’s how I got into glaciology. I took a trip around the world after that. Got my master’s and Ph.D. at Northwestern in materials science.

Thomas:

What sent you to Northwestern in the first place?

Hughes:

It was metallurgy at the South Dakota School of Mines, and I was thinking that a materials science department that uses basic physical laws that apply to crystalline materials in general, not just metals, was founded on the basis that those laws could be applied to any crystalline material including composite materials (that would be metals and ceramics and polymers and these sorts of things) would be a more broadly based background for practicing that kind of profession than just metallurgy. It had just gotten started. In fact, I was practically in the original class of graduate students. It was really just a graduate department. So, I applied to there and the University of Montana School of Mines. But I decided to go to Northwestern. I had been to the South Dakota School of Mines. I didn’t think Montana’s would be that much better, or different anyway, so I thought it’d be a good change of pace—you know, big city after being raised on a ranch. Northwestern is just north of Chicago. So, a number of reasons to go there. And it had a good reputation pretty much across the board, not just in science and engineering.

So, when I came back from that trip around the world, I had finished my doctorate. It’s over 500 pages. It’s an x-ray diffraction study of nickel-aluminum alloys. The master’s thesis measured thermal expansion of the same alloys. The alloys have a cesium-chloride structure, which has a cubic unit cell with aluminum in the middle and nickel on the corners, and it goes from 46 to 60% nickel. From 50 to 46, the composition is changed by removing the aluminum atoms, so we have 9% vacant lattice sites by the time it gets to the phase boundary at 46 nickel. But when you go in the other direction, from 50 to 60, we replace aluminum with nickel, so it’s a quite different way of changing the chemical composition. And it goes through quite a range of color changes from blue to silver to pink to gold through this range of compositions. The alloys have very high melting points, up to 1,650 centigrade, and are very oxidation resistant.

Thomas:

Did you just sort of land on this topic because it was available?

Hughes:

My advisor was a mechanical metallurgist, John Brittain, and he had a research contract to study these alloys. You see, they might have had applications for rocketry, because it was very oxidation-resistant and had a very high melting point. In fact, two of the job offers I got when I finished there was with Rocketdyne Corporation in California, which is a division of North American Aviation; and the other one was to set up a metallographic laboratory in Los Alamos laboratories in New Mexico. But a letter came from the Director of the Institute of Polar Studies at the Ohio State University, asking Weertman if he could recommend someone to be a field assistant on one of the Ohio State expeditions to Antarctica.

Thomas:

Sorry, I have your CV here, at least a truncated version of it, but just to put some dates on the recording, the BS in metallurgical engineering is 1960, and then the master’s is 1962, and the PhD is 1968.

Hughes:

Yes, that’s right. I took a year off… ’66 and ’67 I took a year off to go around the world.

Thomas:

Okay, that was just sort of a personal expedition?

Hughes:

Yes, I just wanted to see the world. I’d written my dissertation. I knew they weren’t going to read it any time soon because it had over 500 pages, and so I thought, well, I’ll give them a year to read the damn thing. [chuckles]

Thomas:

That is unusually long for a science and engineering dissertation.

Hughes:

Yeah, it is.

Thomas:

I’ve noticed that in your papers on the West Antarctic Ice Sheet from the 1970s, they’re also very long and very synthetic. Is it sort of the same…?

Hughes:

I never really mastered the art of brevity. I tell people that if I made that dissertation thick enough no one would read it, and so they never know whether it was any good. The committee members couldn’t admit they never read it, so they just have to give me the PhD anyway. And I don’t know if that isn’t what happened. I don’t know to this day. They’ll never admit they didn’t read it, but I did get the PhD, so go figure.

Anyhow, the fellow who sent that letter to Weertman was Colin Bull. He was the director of the Institute of Polar Studies at Ohio State that was founded shortly after the International Geophysical Year to archive all American glaciological work that was done during IGY and afterwards in Antarctica. It was originally an archive, but they continued to send expeditions down, and Ohio State was very prominent in that. And so, the Institute of Polar Studies was founded for that purpose by Richard Goldthwait, who was the chairman of the Geology Department there, and then he was its director for a few years. Then he hired Colin Bull from New Zealand to take over. Bull then set this letter to Weertman at Northwestern. And since I was the only student there who ever expressed any interest at all in glaciology, and only because by accident I’d seen that book by Dolph Earl Hooker, Those Astounding Ice Ages

Thomas:

Right, and his work on ice was sort of a side project to his work on dislocation theory?

Hughes:

It’s a side project, but all of his reprints are right there [pointing], so you know, they’re a stack about six inches thick.

Thomas:

I spoke with Hans Weertman for a couple hours back in August.

Hughes:

So, his side interest is a bigger contribution than most full-time glaciologists. And it’s major contributions; it’s not trivial stuff.

Thomas:

But he was involved with your dissertation work for metallurgy.

Hughes:

Yeah, he was on my committee, my master’s and my PhD committee. So, he showed me the letter from Colin Bull, and because I was the only one who expressed any interest in that — and Hans gave me some reprints of his, which I read — and I thought, well… and I had been around the world, not to Antarctica though, and I was still single, I haven’t accepted any jobs yet. Well, give it a fling. It’s just to go down there and be a field assistant on a glaciological project. This is in between one phase of my career and I haven’t really started the next, so this is a time I can do it. So, I said yes.

Weertman must have written a very nice letter of recommendation, because Bull sent me a letter offering me a full-time salaried position as a research associate. I was right out of graduate school. I didn’t know anything about glaciers. I’d been studying nickel-aluminum alloys. But he made the offer and I took it. Then I was in charge of drilling holes in Meserve Glacier, because Gerry Holdsworth, the graduate student who was going to do that as part of his doctoral dissertation, didn’t pass his physical exam; they found some spot in his chest x-ray, so they wouldn’t let him go down. There was nothing wrong with him. There was some kind of a glitch or something. He went down the next year, but for that particular year they wouldn’t let him go down. So, I had a PhD, which just gave me phony credentials for doing this—I’d never drilled anything before in my life, let alone through glaciers, and didn’t know anything about glaciers. Then, all of a sudden I was in charge of this thing simply because I had the PhD. And we went down there and we managed to do it. And I enjoyed it. It was a lot of fun. Then Colin Bull came down for a short time with John Nye, whom you could call the father of modern glaciology in the English-speaking world. So, I got a chance to get acquainted with them on a more personal basis.

Thomas:

Had you digested the theories of Weertman, Nye, Glen, and some of those?

Hughes:

Some of them. Not the whole thing; you know, it was too much to do in just the short time I had been there. Anyway, I told Colin Bull that I’d like to take a few months to see more of the world on the way back, because I’d just been around the world a year before, you know, and got kind of hooked on traveling like that, overland for the most part. I really originally only wanted to be a field assistant, and so it’s okay if you fire me, I said, I’ve got other job offers, and some of them are willing to wait until I come back, so it’s okay, I won’t mind. I wanted to go to Antarctica. I’ve been to Antarctica, and I enjoyed what I’m doing. I wouldn’t mind having this be my career, but it doesn’t have to be. If you get someone who’s more responsible it’s okay, I won’t mind.

Thomas:

How long were you there in Antarctica doing that drilling?

Hughes:

About three months, I think, on that particular project.

Thomas:

Where was this?

Hughes:

Meserve Glacier. It’s in the Dry Valleys just west of McMurdo Station, which was on Ross Island in the southwestern corner of the Ross Sea. Probably the part of Antarctica where most research has been done is in the Dry Valleys, so called because outlet glaciers from the East Antarctic Ice Sheet don’t enter them, so there’s little—

Thomas:

That’s where they come over the mountains?

Hughes:

Yeah, there’s too high of a ramp for the ice sheet to come in. It did in the past. There’s three or four of those dry valleys, and ice cut the valleys out, but at the present time East Antarctic ice isn’t high enough to get over this threshold of rock at the end of the valleys. So, there’s only little mountain glaciers coming down the sides of the valleys, and Meserve Glacier is one of them. So, we drilled holes through it to measure the temperature and inclination of the holes. As the ice flows, the hole bends and then you can measure the velocity vertically from top to bottom from the bending of the hole and measure the temperature. That was what the project was. So, you know, I came back to New Zealand and traveled around in Australia for a while, and then up to Singapore and through Southeast Asia, every country except Vietnam.

Thomas:

This is still a lot before 1970?

Hughes:

This would have been ’69, late winter and spring of ’69. And all across southern Asia all the way to Iraq, and then across North Africa to Gibraltar and up through Western Europe and Scandinavia, and then I took a fishing boat to Greenland, and ended up taking a pole flight across to Alaska and then came down the inside passage to Seattle, took a bus to San Francisco and then a train to the Grand Canyon, and went back to Columbus, Ohio. It took me six months, and the job was still waiting for me. So, I thought, gee [laughs], if I can keep a job doing that, and it’s work that I enjoy doing, I’d be crazy to take one of these other jobs where I wouldn’t approach that kind of freedom. I’ve got to tell you, in my glaciological career I’ve done that kind of thing a number of times. You know, coming back from Antarctica, and I’ve gone to Greenland a number of times, too, traveling around South America and other places. So, it’s been a marvelous career for me.

Well, in 1970—I went there in ’68—the American Geographical Society published a map called Antarctica, and it’s hanging on the wall in the next room in there, and it had all the tractor train traverse routes from IGY, International Geophysical Year, and afterward on it, and along those routes were the measurements of ice thickness and ice elevation and surface temperature and surface accumulation rates and wind patterns, and all these basic kinds of data. And ice elevations for the West Antarctic Ice Sheet, which is the part that’s in the western hemisphere, show that ice sheet has an overall concave profile, whereas equilibrium theory in the literature requires a convex profile for steady-state equilibrium. The East Antarctic and Greenland ice sheets are convex overall because they’re close to steady state everywhere, but may not be in any one place. But they’re pretty close to it—they don’t depart from it very much. Well, this is a major departure. In fact, a thought occurred to me that the West Antarctic Ice Sheet is collapsing, producing the Ross Ice Shelf, which is as big as Texas, and other ice shelves where it has collapsed almost to sea level. On the other side of West Antarctica, in the Weddell Sea, the Filchner and Ronne Ice Shelves are collapsed portions of the West Antarctic Ice Sheet, which was three times bigger at the Last Glacial Maximum than it is now. So, I composed a number of ISCAP (Ice Streamline Cooperative Antarctic Project) bulletins to argue that case. Here they are. There are four of them. I did two of them at Ohio State and two of them here, and they were circulated around privately by Ohio State University and the University of Maine. They all ask the same question: is the West Antarctic Ice Sheet disintegrating? And there’s the cover letter from when I was at Ohio State that accompanied these things.

Thomas:

So, what are these essentially? I’ve never seen the unpublished versions.

Hughes:

They were never published. They’re like monographs. But they all ended up in scientific journals about a year later, except for the second one. That was a chapter of my book, Ice Sheets, that Oxford University Press published for me in 1998. That bulletin ended up in a chapter of the book. All the rest of them, Journal of Geophysical Research published the first one, and the two others were in another major geophysical journal. Anyway, people saw them. The idea got out that… And I wasn’t the only one thinking along these lines, but I was the first one to try to put it together in some kind of a comprehensive way that built a case for an extensive research program to answer that question: is the West Antarctic Ice Sheet disintegrating?

By disintegrating I mean it has to occur in two stages. The first stage is gravitational collapse. The West Antarctic Ice Sheet is grounded mostly below sea level, so when it collapses gravitationally it becomes afloat, and two sectors have already collapsed since the Last Glacial Maximum to produce these floating ice shelves in the Ross and Weddell Sea embayments. So, that’s the first stage that’s necessary. The second stage is once it has collapsed and is afloat, then the floating ice shelves, as they’re called (a floating ice sheet is called an ice shelf), must disintegrate, break up into icebergs. So, this question, “Is the West Antarctic Ice Sheet disintegrating?” has a two-part answer. The first is to answer the question, is it continuing to gravitationally collapse? And the second is, once it does, will it disintegrate into icebergs? Will floating ice shelves disintegrate into icebergs? Once that happens, the West Antarctic Ice Sheet is removed from Earth’s climate machine. And that happened in the Northern Hemisphere. The big ice sheets on North America and Eurasia gravitationally collapsed and then disintegrated in the parts that were grounded below sea level and became floating ice shelves. For the Laurentide Ice Sheet, collapse began over Hudson Bay and Fox Basin, and areas between the Canadian Arctic Islands that were below sea level. For the Eurasian Ice Sheet, it would have been the Baltic Sea and the Barents Sea north of Scandinavia, and the Kara Sea east of the Barents Sea. These areas were all marine portions of those ice sheets. The weight of ice pushed the land down and increased the marine portion of all of these ice sheets. So, at some point during the Last Glacial Maximum, a critical threshold had been crossed so that what we call a marine ice instability kicked in and caused the rapid spreading out and lowering to produce the ice shelves, and then the leading edge of the ice shelves disintegrated into icebergs, and those two fronts, the grounding line of the ice shelf retreating into the ice sheet and the calving front of the ice shelf retreating into the ice shelf, were retreating together and resulted in complete disintegration of those ice sheets, so they were removed from Earth’s climate system.

Thomas:

When you say removed from Earth’s climate system, what exactly do you mean by that?

Hughes:

They are gone. There is no continental ice sheet over North America or over Eurasia, and when you remove ice sheets that big, climate has to change, and it did. It’s called a “termination.” Removal terminated the last glaciation cycle, and if you didn’t have that mechanism of the marine ice instability to collapse the ice sheet so that it’s thin enough to become afloat, so a calving bay could migrate into the heart of the ice sheet and carve out the center of those ice sheets, they would still be here today. They would not go away, because the solar insolation that we have today is as intense as it was at the Last Glacial Maximum 20,000 years ago, when those ice sheets were at their maximum extent. Since ice sheets can exist at that size with the solar insolation pattern we have right now, we need these inherent internal instability mechanisms independent of the rest of the climate machine to get rid of these ice sheets. That’s happening right now for the West Antarctic Ice Sheet. And there’s parts of the East Antarctic Ice Sheet that are grounded below sea level, too. It’s ten times bigger than the West Antarctic Ice Sheet and it’s not completely invulnerable to these processes. One of the things you’ll see in this paper on modeling of ice sheets from the bottom up that I gave you is I make the case for the marine ice instability that collapses and disintegrates the West Antarctic Ice Sheet and then migrates into the East Antarctic Ice Sheet through a gap in the Transantarctic Mountains called the Bottleneck. How much of the East Antarctic Ice Sheet might be vulnerable to collapse through this mechanism is an open question. My ISCAP bulletins, which first posed this question, were circulated in the early 1970s.

Thomas:

So, this is sort of a personal series that you have put out, or is it a larger project, these ISCAP bulletins?

Hughes:

It was just my own. I did it all myself.

Thomas:

Okay, so there aren’t other ISCAP bulletins that are written by someone else?

Hughes:

No, these were meant to focus attention on the inherent instability of the West Antarctic Ice Sheet, being a marine ice sheet, and explaining the existence of the big ice shelves in the Ross and Weddell Seas as caused by Holocene collapse of the West Antarctic Ice Sheet. It was three times bigger than it is now, and it may still be collapsing. That was the question: is the West Antarctic Ice Sheet disintegrating? And remember, following collapse, disintegration is the next step if you’re going to take the ice sheet out of the climate system. But you can’t have disintegration without collapse. You’re not going to get big icebergs calving off of the edge of an ice sheet that hasn’t collapsed because it’s going to be too thick; it would have crevasses unable to go through the thick ice. You need thin ice to produce icebergs. Once it thins down to become afloat, then you can do it. So, the collapse has to precede disintegration.

My ISCAP bulletins were sent by the Ohio State University Research Foundation to various universities around the country and overseas where there were glaciological programs, and one of them was here at the University of Maine. At that time in the 1970s there was something called The International Decade of Ocean Exploration from 1970 to 1980. And one of the projects being conducting at that time was called CLIMAP, which is an acronym for Climate: Long-Range Investigation, Mapping and Prediction. There were two CLIMAP experiments. One was at the Last Glacial Maximum, which the CLIMAP people pegged at 18,000 years ago. The other one was the Last Interglacial Maximum at 125,000 years ago. There were two experiments to run for CLIMAP at the two extremes of climate that Earth had during the Quaternary Period. It’s really the Quaternary ice age. You know, one is the glacial maximum part of the ice age and then the other is the interglacial. There’s been about nine or ten of these things, roughly 100,000 years apart during the Quaternary. The glacial times last about 90,000 years, the interglacial about 10,000 years on average. The assumption was that Earth’s climate is sort of encompassed within this envelope of maximum glaciation and minimum glaciation during the Quaternary ice age. So, if you studied these two extremes, you had bracketed the kind of climate systems that are possible for the Quaternary ice age. That was the idea. The interglacial maximum, 125,000 years ago, was a time when sea level was about six meters higher than today, and the prime candidate for that was the West Antarctic Ice Sheet, which we thought had about five meters of sea level locked up within it. Greenland has about seven. Well, they knew that the Greenland Ice Sheet had not vanished. They drilled through it at Camp Century earlier, and they got to the bottom. It was frozen to the bed, and you’re not going to get this kind of gravitational collapse with an ice sheet that is frozen to the bed. They drilled through West Antarctica just a few years later in 1968, the year I entered glaciology. The bed was wet, and basal water came up the hole and froze. With a wet bed, it already had reduced ice bed coupling, which is compatible with ongoing gravitational collapse. So, you know, a wet bed is a slippery bed compared to a dry frozen bed.

The wet bed is right in the middle of the West Antarctic Ice Sheet today. So, that was a prime candidate for what we called the CLIMAP Eemian experiment, 125,000 years ago, the Eemian Period. And my ISCAP bulletins were making a case that that might be happening right now during the present interglaciation. So, George Denton was given a piece of the CLIMAP pie to reconstruct the ice sheets for the two CLIMAP experiments: the Last Glacial Maximum 18,000 years ago and the Last Interglacial Maximum 125,000 years ago. And my ISCAP bulletins fit very nicely into the second of those, because it’s focusing on collapse of the West Antarctic Ice Sheet and marshaling all the evidence that that has been going on since the Last Glacial Maximum, and may still be going on today.

And when the ISCAP bulletins were going around, a lot of other people got interested in the same questions. NSF decided to make answering this question a major priority of its Antarctic research program. Well, George Denton and Hal Borns—he was the founder of what was originally the Institute for Quaternary Studies; now it’s the Climate Change Institute—Hal Borns was the first director of that, and he was also chairman of the Geology Department at that time. This would have been 1974. Two of my ISCAP bulletins were already out, the two I did at Ohio State. And I had gone for six months on kind of a sabbatical to the National Center for Atmospheric Research out in Boulder, Colorado. Out there I was writing a third one of these things. Denton thought that I’d be a good guy to be the one who reconstructed the ice sheets for CLIMAP for both of these experiments. It’d be close to steady-state ice sheets for the Last Glacial Maximum, which would be the ice sheets in North America and Eurasia primarily, and the enlarged Antarctic ice sheet before the West Antarctic Ice Sheet started to collapse. Then the Eemian experiment would be taking the West Antarctic Ice Sheet in its full-bodied configuration and then collapsing it, and developing computer models that would do this.

Thomas:

This isn’t ’74 yet?

Hughes:

Yeah, that’s why I was hired. So, the first set of experiments was to construct steady-state ice sheets. The second one, the Eemian experiment, was to take a steady-state ice sheet that’s a marine ice sheet and collapse it over time, so those are the two experiments. I was offered the opportunity to do that here. I saw it as a chance to become involved in this much larger enterprise of studying the history and causes of global climate change, whereas at Ohio State it was in the Institute of Polar Studies, which was primarily interested in the Arctic and the Antarctic. It has become interested in climate globally. And it’s got a new name, too. Now it’s called the Byrd Polar Research Center. The Institute for Quaternary Studies has always from the very beginning had that goal in perspective and climate research, paleoecology, archeology, glacial geology, glaciology, climate change in general, and how to determine what it was, how to measure it, and how to understand it. From the very beginning, that was the goal of this place, and so it was a good fit with this larger enterprise that was CLIMAP, and so Denton was picked to reconstruct the ice sheets.

Well, what made CLIMAP possible was John Imbrie and his laboratory assistant Melba Kipp had developed what they call transfer functions, and what these did was provide a way to determine the ocean’s surface temperature in the past. The way they did it is by having all kinds of microorganisms, both plants and animals that lived on the ocean’s surface and on the ocean floor, especially the ocean-surface-dwelling ones that were very sensitive to temperature and salinity. There’s hundreds of species of these things, many hundreds, diatoms being the major plant species, and there’s just hundreds of those. They’re all microorganisms. They all have some kind of a shell, but when they die the shell will either be silicon or carbonate and it’ll sink to the seafloor and be a major constituent of the seafloor sediments. So, if you can core into those sediments and then look at thin sections, you could identify what the species were from their shells. The shells are like fingerprints; each one is unique. And so they can identify the abundance of these microorganisms on the Earth’s surface and on the seafloor and compare their abundances with the abundances today, which are dependent on the salinity and the temperature. They know what the salinity and the temperature are today that are optimum for these creatures, and so then they’re able to, knowing their abundances in the past, they can map the ocean surface temperatures and seafloor temperatures anytime in the past, as long as they have some way to date the column of sediments. Well, in the North Atlantic, there happened to be some very fortuitously placed volcanic ash layers from volcanoes in Iceland that gave dates of radiocarbon horizons, and then they used sedimentation rates to get a timescale in between these horizons. They continued to do this all over the world. Where they didn’t have some volcanic horizon, they used the sedimentation rates that they had anchored to the absolute horizons in the North Atlantic and they were able to map the ocean surface temperatures worldwide. Especially at 18,000 years ago, because the radiocarbon chronology goes back that far. For the Eemian, 125,000 years ago, it was more problematic, but less important because you didn’t have the big ice sheets then. You know, they’re interested primarily in getting rid of the West Antarctic Ice Sheet.

So, the main focus of CLIMAP was the Last Glacial Maximum. So, they knew the ocean’s surface temperatures at that time, and the atmospheric circulation models were very primitive then. One of the major inputs they needed was the ocean surface temperatures, because the ocean-to-atmosphere heat transport takes place at the ocean surface. That’s what drives atmospheric circulation. Most of solar radiation, especially the short-wavelength part, passes right through the atmosphere and warms the darker parts of the Earth’s surface that have the low albedo, which would be jungles and the sea surface. Those are the parts that look dark from outer space. The deserts and the ice sheets are lighter colored, so they have high albedo, they reflect solar radiation back into the atmosphere. Well, when the solar radiation heats the dark places, then they’re warmed up. Then they’ll emit long-wave radiation, which doesn’t pass through the atmosphere; it gets trapped in the atmosphere and heats the atmosphere. That’s what drives atmospheric circulation. You get the temperature difference between the equatorial latitudes and the polar latitudes, and the heat wants to move from the hot places to cold places, and that sets up a general drift of the atmosphere. Of course, the Earth is rotating under that drift, so it experiences in mid-latitudes these strong westerly winds. You know, from our position here on the Earth’s surface, it seems like winds are blowing from the west to the east, but actually they’re just moving towards the poles and we’re moving under that at the rotation rate of the Earth, which is hundreds of miles an hour. And that’s what gives us the winds, or that’s what we feel as winds.

So anyway, they had that important boundary condition, the ocean surface temperature. From pollen records, they had some idea what the land vegetation was at that time, and what they needed to be able to run those models were how much the ocean’s surface area had decreased because of the buildup of the ice sheets that lowered sea level. And it decreased something like from three-fourths of what we have today to two-thirds. So, quite a lot of the continental shelves were exposed, and that reduced by that amount the ocean–atmosphere heat exchange. So, that’s an important change from today’s condition, because that’s what heats the atmosphere, you know, gets the thing going. So, they needed that. They needed the volume of the ice sheets, because you could calculate from the volume how much continental shelves became exposed and reduced the ocean’s surface area. They needed the elevation of the ice sheets, because the westerly winds, which are surface winds, can’t easily go around ice that’s three kilometers high. All of Canada was as high as Pike’s Peak back then, because of the ice sheet, and so they needed the elevation for the wind patterns. And also, the jet stream, because the jet stream dips down in the mid-latitudes, lower than the ice sheet, so it can be divided into two branches, a stronger southern branch and a weaker northern branch that goes around the North American Ice Sheet and then hooks up again in the North Atlantic. And then the Eurasian Ice Sheet can split the jet stream again. So, they needed to know elevation. And then of course they needed to know the albedo, so they needed the area extent, not just of the ice sheets but the sea ice that was year-round and seasonal at that time. Well, there are microorganisms, for example diatoms, in the ocean’s surface that attach themselves to the underside of sea ice, and so there’s a seasonal distribution of these things that fluctuates with the extent of the sea ice. So, that was something that they knew from these microorganisms and the ocean floor sediments. What they didn’t know… Well, they needed to know the areal extent of ice on land. Well, that’s the purview of a glacial geologist, which is what George is, so he was brought into CLIMAP specifically to provide that input. Well, then they needed the vertical extent to get the volume and the elevation, and he needed a glaciologist for that, not a glacial geologist, so that’s why I was brought in. So, the University of Maine provided these three essential boundary conditions for those models.

Thomas:

Sorry, who’s running the CLIMAP project?

Hughes:

John Imbrie of Brown University was Mr. CLIMAP, but it was Columbia University, Oregon State University, University of Maine, and Brown University. Those are the major ones, and then individuals at other universities had little pieces of the action. It was run out of Lamont-Doherty Geological Observatory. They’ve renamed it since then. We met at Lamont-Doherty during these years.

Thomas:

And sort of being funded or coordinating by the NSF?

Hughes:

By NSF, yeah. It was part of the International Decade of Ocean Exploration. Now, the only model of ice sheets that existed at that time had been developed by Australians, and they had applied it to the Antarctic ice sheet, and they used surface precipitation and the—

Thomas:

Is this Budd?

Hughes:

Bill Budd, Dick Jenssen, and Uwe Radok were the three. And they produced a monograph called Derived Physical Characteristics of the Antarctic Ice Sheet. This is it right here. It used all the surface information that was collected during the IGY and later years, and that included ice thickness data, so they had some idea of what the bed topography was. That stuff’s all on that American Geographical Society’s map of Antarctica that’s in the other room that came out in 1970. So, they developed this computer model for the Antarctic Ice Sheet as a steady-state model along flow lines, which are directions, going from the interior to the margin in the directions of maximum surface slope. The ice flows downhill where the surface slope is steepest. And then from that information they calculated what the temperatures were at the bed if the bed was frozen. If the temperature is at the melting point, then they can calculate the melting rate. That’s what they got out of that.

Well, that is not something that will work for constructing ice sheets at the Last Glacial Maximum. For one thing, we don’t know what the surface temperatures were or accumulation rates were. It depends on the elevation, which is what CLIMAP wanted us to calculate. For the Antarctic Ice Sheet, all that stuff is known. For former ice sheets it’s all unknown, so you can’t use that kind of a model. Also, to get a frozen or a thawed bed, they had to put in something for the geothermal heat flux from the Earth’s interior, but if they change that by a factor of two, their model that calculated a frozen bed almost everywhere would calculate a thawed bed. Just by doubling the geothermal heat flux. Geothermal heat hasn’t been mapped all over North America and Eurasia where there are former ice sheets. They don’t know that heat flux. They know what it is in certain places from the geophysical prospecting of some kind or another going on.

Thomas:

Is that presumed to be constant, or relatively so, over tens of thousands of years?

Hughes:

That’s the assumption they make, but they don’t know that. It’s an assumption of convenience, as much of scientific assumptions are. Just to do something, you have to make these assumptions. So, it was completely inadequate for reconstructing the CLIMAP ice sheets, although in principle you could do it that way. Well, so I had to come up with a different way of doing it, and the basic assumption in glaciology, which you’ll never see stated outright in any of the books—and I’ve got whole shelves full over here—is that the height of ice above the bed is determined primarily on how strongly ice is coupled to the bed. The strongest coupling is ice frozen to kind of a rough bed with a lot of little bedrock projections in it. If the bed thaws, then the ice can slide on that water film. But if the bed is still rugged, there’ll be a lot of little bits of rocks sticking up into the ice and it can still offer quite a lot of resistance to this sliding action. So, you go from ice frozen to a rough but thawed bed, that’s a reduction in coupling. Then that sliding will eventually polish the ice-bed contact by removing all these little bumps and things, and so then it’ll be ice sliding on a smooth bed. But there’ll still be hills and hollows that the ice has to go up and down over these things, and that provides some resistance.

Thomas:

Now, the thawing is mainly a matter of pressure?

Hughes:

Pressure? The pressure will crush… Ice floats in water. That’s the crystal structure of ice right there. At very high pressures, that’s a fairly opens structure, it will crush it into a more compact structure, which is water molecules, individual H2O molecules. The unit cell in a crystal of ice has 24 hydrogens and 12 oxygens. That’s what’s there is in that model. And that occupies a greater volume than water, so ice floats in water. So, if you get enough ice overburden pressure, you can crush the base of ice into water. Also, ice is a good insulator, and so if you pile enough ice on the land it will insulate the geothermal heat flux. Without the ice sheet, that heat is readily going to transport into the atmosphere. When this insulating thick ice layer blankets the bed, heat can’t be conducted upward so easily, so more of that heat gets trapped at the ice-bed interface. That will, over time, melt ice as well. And then the frictional heat of ice shearing over the bed will generate frictional heat, and even after the bed thaws, there’s still some of these little bumps; the ice has to go over an around these things, and that deforms the ice and that generates frictional heat, too. So, we have these three basic sources of melt water at the bed: there’s the crushing of ice into water; there’s the geothermal re-insulation property of ice that traps the geothermal heat, keeps it concentrated in the bed; then there’s the frictional heat of ice motion over the bed, whether the bed is frozen or thawed you’ll get that frictional heat. It’d be less for a thawed bed than for a frozen bed, but it’ll still be there. It’ll be there wherever you got one of these bumps that stick up into the ice. But it’ll be at these point sources rather than sort of uniformly over the whole bed, but it doesn’t make much difference because the ice motion smooths all that out anyway. All that heat generally gets distributed more or less uniformly.

Anyway, there are still hills and hollows that provide some resistance to this ice sliding motion. If you increase the melting rate after the bed is thawed, the additional melt water has to thicken, and it’ll thicken first in the hollows, and that’ll drown the bumps, the irregularities on the bed, beginning in the hollows and then progressively encroaching on the hills. When that happens you go from what’s called sheet flow, which is this slow spreading of the ice as a sheet over the landscape, to stream flow, which is fast currents of ice that develop along these bedrock hollows that tended generally to be elongated, because originally, before the ice sheet was there, there were probably river drain systems, so the ice will tend to follow those and that’ll produce ice streams, fast currents of ice that aren’t that much different from the rivers that drain most of North America. They get stronger near the ice margin and larger because they’re moving faster and the ice is getting thinner, and so all the ice is getting funneled into these things and they discharge up to 90% of the ice by the time you get to the edge of the ice sheet. So, to study the dynamics of ice sheets, you really have to understand the dynamics of ice streams because up to 90% of the ice comes out of them, and it’s never less than 50%, so it’s 50 to 90. Right now, about 70% for Greenland and 90% for Antarctica comes out by ice streams. That was true for the ice sheets in the past, too. We know where they were from the glacial geology.

So, all these things that I’m mentioning is reducing the ice bed coupling, you know, first thawing the bed, then drowning the bed. Everything is acting in a way that it uncouples the ice from the bed. So, it’s possible to calculate how thick the ice can be above a bed that has a certain amount of coupling. What tells you how much coupling there was at the Last Glacial Maximum… well, the glacial geology tells you that—if you interpret it correctly. That’s the key. And what we had to do for the CLIMAP reconstructions is not look at what traditional glacial geologists map, you know, the striated pavements and moraines, because that’s a record of the last retreat. Those are the deposits and the imprint in the landscape during the last retreat of the ice sheet. We want the imprint that existed at the maximum, which is different, way different. The retreat has second-order glacial geology imprinted on the first-order glacial geology, which is reinforced during each glaciation cycle because the ice sheets form over the same land masses, and these sort of close-to-steady-state processes create an imprint that gets reinforced with each glaciation cycle. So, that’s what we did for the CLIMAP ice sheets. We looked at first order glacial geology—it wasn’t even mentioned in the literature. We developed it for the purposes of the CLIMAP reconstructions. And when we presented them in an International Glaciological Society meeting in Ottawa, our reconstructions were all rejected on that basis, because all the referees were looking at the standard glacial geology that was produced during the last retreat; they couldn’t understand this other way of doing it. So, we put out a book, The Last Great Ice Sheets, where we bypassed the review process. We picked the referees, or George Denton did.

But that remained the most accurate reconstruction of ice sheets because it doesn’t depend on all these other things. If you get the glacial geology right, you will get the ice elevations right. It doesn’t matter so much what the former accumulation rates or temperatures were. They’ll be determined by the height of the ice anyway, and you’re getting that as a first-order output. All the rest of it is secondary, it doesn’t have much effect, and you don’t have to know what the basal geothermal heat flux is. Glacial geology tells you what the ice-bed coupling was, and that allows you to reconstruct the ice sheets. So, that’s how we did it. And it doesn’t depend on the past history of the ice sheets. It’s the coupling that existed right at that time that tells you how high the ice had to be at that time. So, it was a completely different way of doing it, totally revolutionary, outside the box, and it’s just as valid today as it was then—if you get the glacial geology right. So, there’s been a big effort ever since CLIMAP to look at glacial geology in this other way, and that’s one of the fruits of our contributions to CLIMAP that’s ongoing right now. We had two reconstructions: the maximum version and a minimum version. And here again, talking to glacial geologists in Canada and Europe, they couldn’t imagine the ice sheets extending out into the sea as marine ice sheets. But it happens in Antarctica: we know they can do that. They couldn’t get outside the land box and into the sea. Well, we knew the sea floor topography, we know there are troughs going out from the inter-island channels and the straits that cut across the continental shelf. They had to be occupied by ice streams, being foredeepened like fjords are.

Thomas:

So, I have the assumption then that you’re referring to is that there’s land ice and then there’s sea ice.

Hughes:

It’s marine ice. It’s ice that is grounded. Sea ice is floating, but the ice sheets advanced out onto the continental shelves to the edge of the shelves.

Thomas:

But what I’m saying is that the usual theories that you’re arguing against were saying that there were just land ice and then sea ice, and that there wasn’t marine ice.

Hughes:

They would say sea ice in the sense of just a meter or two or three thick in the Arctic Ocean today, and there was. But the continental shelves… grounded ice sheets are on the continental shelves. I mean that was our maximum reconstruction. The minimum was just to shut them up. We did a version that ended the ice sheets pretty much at present-day shorelines, just to get them off our backs. Then we did the other one the way we thought it really was, and that’s the one that prevailed. It was quite a while before they caved in and took this exposure age-dating techniques. Are you familiar with exposure age-dating, cosmogenic nuclides that date rocks?

Thomas:

I don’t think so.

Hughes:

Bring it up with George; he’ll tell you all about it. It’s a dating technique that only came on board the last 10 or 20 years, post-CLIMAP. It allows dates going back hundreds of thousands of years, so it greatly expands dating beyond the range of radiocarbon dating. You’re lucky if you can get to 30,000 years with radiocarbon. And they showed that all these headlands of the fjords had to have been covered with ice, and it’s only possible if the ice goes out onto the continental shelf. So, the Greenland and North American Ice Sheet were all one continuous ice sheet. That came out of CLIMAP too. We had the maximum and the minimum versions. The reconstructions are in our book. We got them both. That says why the critics, you know, they wanted to believe in the minimum version. They want to get outside their box. The maximum or minimum was there, too, because there were these two ways of doing it. Both of them were reconstructing ice sheets from the bottom up, which is that thing I just gave you there that tells how we did it. One was recasting glacial geology into first order and second order, and then using the first order for the LGM and the second order for deglaciation, the final retreat during the termination. That’s the way it should have been used all along, and they didn’t do it that way. So, that was the first thing, revolutionizing the way of looking at glacial geology, and then the second thing was getting these ice sheets much bigger than anybody thought they’d been, getting out to the edge of the continental shelf in Eurasia and North America, like we know happened in Antarctica. And it’s still in parts of Antarctica today, like West Antarctica, it’s out on the continental shelf. So, well, that pretty much brings things up to date.

Thomas:

Okay. Well, in that case I’d like to take the opportunity to kind of go back. The thing that I’d like to ask you about first is kind of how you pick up this perspective from the ISCAP bulletins, particularly. There’s sort of a tradition in the review literature that goes back to Mercer in ‘68 with the “Sangamon Sea Level” paper, but I’m under the impression that you’re sort of responding in part to that, but more to sort out theories that had been going back into the ’50s and ’60s with a lot of glaciological papers and also a lot of the ice age theories. Weertman had originally responded to Ewing and Donn. Alex Wilson’s theory that came up in the late ’60s was picked up by guys like John Hollin. And so I’m wondering what people are responding to most in the ISCAP bulletins?

Hughes:

John Mercer was at Ohio State when I was there. His office was just down the hall from mine, and he had developed the concept of marine ice sheets while I was there and published it. So, I was aware of… And the idea that the West Antarctic Ice Sheet could have been bigger in the past; he had some evidence for that in his glacial geological studies in Antarctica, and he also was the first one to suggest that during the Eemian, 125,000 years ago, what’s there now had collapsed. So, for both of those CLIMAP experiments, the LGM and the Eemian, he was the first one to suggest that the West Antarctic Ice Sheet had been a lot bigger at the LGM, and then it had disappeared during the last interglacial maximum. So, yeah, he was very much an inspiration for the ISCAP bulletins. And everything that I saw on the American Geographical map of Antarctica was compatible with Mercer’s ideas. Denton himself had been working in the Dry Valleys at that time, as I had mentioned earlier, and he had concluded that there was invasion of grounded ice from the Ross Sea into the Dry Valleys, probably at the Last Glacial Maximum. He didn’t have much in the way of dating back then, but he described it as an invasion of ice into the Dry Valleys from West Antarctica at a time when the Ross Ice Shelf was grounded and part of the grounded part of the West Antarctic Ice Sheet. So, that came out in 1968. That was the year I went to Ohio State. ’68 was also the year that Mercer proposed the collapse of the West Antarctic Ice Sheet during the Eemian. Then two years later in 1970… Well, I think even in ’68 he was talking about a bigger West Antarctic Ice Sheet. He coined the word marine ice sheet to describe West Antarctic Ice Sheet in 1970, and it was with respect to ice sheets in the Arctic that would have been grounded on the continental shelves, primarily of Europe in the Bering Sea north of Scandinavia. So, he was thinking along those lines as well for the Arctic, you know, marine ice sheets and their inherent instability.

John Hollin had picked up on Alex Wilson’s idea that the whole Antarctic Ice Sheet might surge, not just West Antarctica but East Antarctica, too. There’s some sea level data in England and maybe some other places that show sea levels were 20 meters higher than today, something like that. It’s not as well documented as the six-meter Eemian sea level and aren’t dated, but there’s some evidence for that. Hollin was citing.... I mean, you can’t get that from Greenland or West Antarctica; you got to get at least some of it from East Antarctica. So, he was arguing that parts of the East Antarctic Ice Sheet could be unstable, too. And there are parts that are grounded below sea level, you know, so it could be.

Thomas:

And you yourself were viewing this as a sort of possible trigger for a new ice age, in line with the Wilson theory?

Hughes:

Well yeah. If you take these ice sheets, or Greenland or West Antarctica, and they do collapse and disintegrate, then you’re putting a lot of ice into the surrounding oceans. And for the Greenland Ice Sheet in particular, the Gulf Stream comes up the East Coast and then cuts across as the North Atlantic current and heads towards Scandinavia. There’s places north of Iceland in the Labrador Sea where North Atlantic deep water is produced, and the high evaporation rates of gulf stream water that gets up into those locations, the North Atlantic current water, that provides that mild climate that you have in western and northern Europe today, is the evaporation of that warm gulf stream water when you get up into those higher latitudes, and then the westerly winds bring that warmer air into Europe. But if you dump a lot of icebergs in there, and it takes one degree of sensible heat to raise one gram of ice one degree, and then it takes 80 calories to melt that gram. If you’ve got icebergs that are being dumped in that average, say 10 degrees below zero, it’ll take 10 calories for each gram to get it up to the melting point, and then another 80 calories to melt it, that’s 90 calories for each gram. In any of these big iceberg outbursts, which we’re talking about billions of metric tons, and as an ice sheet collapses, you can dump those volumes of ice into the ocean in a hurry. To melt that ice, it has to be taken from the ocean surface water down to a depth of the draft of the icebergs, which is 100, 200, 300 meters, something like that. And then there’s no heat available for the ocean-atmospheric heat exchange that drives atmospheric circulation because you’ve used it to melt the ice. So, yeah, that’ll kick you into another climate regime, and it’ll be an ice age type climate regime. It’ll shut down what’s called that conveyer belt that Wallace Broecker talks about. Denton and Broecker highlighted that in a paper that they published about 20 years ago. So, yeah, it can. Ice sheets can change climate, and that’s what happened. I think that’s the explanation for the termination of the last glaciation cycle. Laurentide Ice Sheet in particular collapsed, but so did the Eurasian ice sheet, the marine portions first, and all that ice was dumped into the North Atlantic. Then, after that ice was melted, then this conveyer system could start and create the climate that we have today.

Thomas:

I wanted to ask you about your work habits in the period. I guess we’ll take this up again after your talk.

[Pause in recording]

Thomas:

So, I was asking you a little bit about your work habits when you went to Ohio State and were developing the ISCAP bulletins. This was all after you came back from the fieldwork in Antarctica. So, it seems to me that it’s fairly… developing a synthetic approach to paleoclimate and also glaciology based upon the work of people like Weertman and Nye. So, I’m wondering if it is largely just reading very broadly and trying to bring that all into a coherent picture, or if there is something else that you are doing in that period?

Hughes:

My best work has always been the consequence of what I’ve done in the field. I’ve got a lot of publications, but the ones that stand the test of time are the ones that are based on the fieldwork for a couple of reasons. One, they’re grounded in reality more than things that are just a figment of my imagination. The second one is they allow a degree of quantification that avoids making assumptions if something is just purely theoretical to get from one step to another. If you don’t have any data, you make some guess about things. But I haven’t been in the field as often as a lot of people around here. I have been to Antarctica a number of times and Greenland a number of times. Well, the first time was drilling those holes through Meserve Glacier, so I looked at the temperature increase and the velocity decrease with depth. The second time, I was on the Ross Ice Shelf with a glaciologist who came here for a few years in the middle 1970s, Bob Thomas, who’s at NASA now. He basically got the glaciological program going there at NASA. He wasn’t the one who initiated it, but he’s the one who made it the most comprehensive in getting an awful lot of field work included, as well as satellite measurements of conditions on the surface of the ice sheets. He was the chief scientists on the Ross Ice Shelf Project, which was a project of the 1970s.

Thomas:

Did you have much to do with that at all?

Hughes:

No, I went down there as a field assistant with him one season, just to get the opportunity to be on an ice shelf. Then, he and I had a proposal to study Byrd Glacier, which is the biggest ice stream coming into the Ross Ice Shelf. It comes in from East Antarctica. Over there in the other room, there’s a photograph of Byrd Glacier, a photograph that’s based on false-color Landsat imagery. And so, he and I wrote a proposal to study that, it’s the biggest ice stream supplying the Ross Ice Shelf. His wife was expecting a second child at the time and she wanted him to be with her when the baby was born, so he didn’t go down. Nonetheless, there was a project we collaborated on. Then in ’80–’84, I was on Deception Island in Antarctica, a volcanic island that had erupted and blown away the front of a glacier, leaving an ice wall 100 meters high. So, I was studying the calving mechanism of ice blocks, slabs of ice falling into the crater produced by the eruption. Ice streams and calving dynamics are two parts of glaciology that I’ve invested a lot of work on, and that was fieldwork, fieldwork dealing with those two situations.

Thomas:

This work is interspersed with the CLIMAP project?

Hughes:

It went on at the same time.

Thomas:

But they weren’t closely related?

Hughes:

Not particularly, no. They proceeded on separate paths, but you always learn something. There’s always cross-fertilization. Now, the ice stream that I was interested in was Jakobshavn Ice Stream that comes into Baffin Bay about a third of the way up the west coast of Greenland, and for a long time it’s the fastest known ice stream in the world. It moves about six or seven kilometers a year, and it produces the big icebergs, big tabular icebergs break off of it, because it becomes afloat in Jakobshavn ice fjord. It’s probably one of its icebergs that sank the Titanic, because they’re big icebergs that go into Baffin Bay and make that circuit around Baffin Bay and then get into the North Atlantic shipping lanes around the Grand Banks of Newfoundland, in that area. That’s where the Titanic hit an iceberg. So, Jakobshavn produced the biggest icebergs. Its icebergs would’ve had the biggest chunks. They disintegrate as they move around in the ocean, but the biggest chunks would’ve survived that far into the shipping lanes. Probably from Jakobshavn, because they’re like a one square kilometer in size when they break off, you know. And that one, unlike Byrd Glacier in Antarctica, has a lot of surface melting in the summertime, so that melt water can get down in crevasses and eventually find their way to the bed and lubricate the bed. That’s probably why it moves faster than Byrd Glacier. Byrd Glacier moves less than one kilometer a year, and Jakobshavn is about seven. I saw those as kind of end members in studying ice streams, Byrd Glacier comes into the Ross Ice Shelf, which I mentioned earlier is the size of Texas, and it’s confined in the Ross Sea embayment, and its grounding line locks into the embayment between ice streams like pieces in a jigsaw puzzle. So, it’s really quite anchored in that embayment even though a lot of ice streams come into it. All together they can’t move it out as one block into the northern Ross Sea. It stays confined in that embayment. Some of these ice streams are coming in at different directions anyway. From West Antarctica, they’re coming in from the east, and in East Antarctica they come in from the south and the west, and so they’re running into each other to some extent and being forced to turn north. So, that provides some resistance as well to keep the Ross Ice Shelf in place. This is called buttressing, the ice shelves’ ability to buttress the ice streams that supply it, and that’s a term that Bob Thomas coined, and he did his doctoral research on the Brunt Ice Shelf in East Antarctica, not far from the Weddell Sea embayment. There’s also some pinning points on Ross Ice Shelf, like Roseville Island and Crary Ice Rise.

Thomas:

So, Bob Thomas is really the primary one—Hans Weertman a little bit, with his ‘74 paper—to respond to your ISCAP bulletins.

Hughes:

Weertman was purely theoretical, whereas what Thomas has done was develop Weertman’s theory with field data—going into the field, actually measuring the stresses and strain rates on these ice shelves. He and his graduate student Doug MacAyeal, who is now at the University of Chicago, were the first ones to model the Ross Ice Shelf, or any ice shelf for that matter. They developed a finite element model when Doug was here as Bob’s graduate student. That was the first really quantitative demonstration that an ice shelf that’s confined in an embayment and anchored at these pinning points can, in fact, slow the ice streams that discharge into them, and therefore provide buttressing. If you remove the ice shelf, the ice streams would move faster and pull out a lot more ice. So, that was an important contribution. And that was done here. Bob Thomas was at the University of Nebraska at the time, where the Ross Ice Shelf project had its headquarters, and the centerpiece of that was to drill a hole through the Ross Ice Shelf, but it included something called RIGGS, which is the Ross Ice Shelf Geophysical and Glaciological Survey. The guy who headed that up was Charlie Bentley at the University of Wisconsin. He was a geophysicist, and he did the geophysical measurements, but the glaciological part of it was Bob Thomas, and Bob was at the University of Nebraska when that got started, and I invited him to come up here.

Thomas:

Was this on account of his kind-of responses to your ISCAP bulletins?

Hughes:

That probably fit into it to some degree. There was a drilling operation there, and he was working alone as a glaciologist in Nebraska when I was a glaciologist at Maine, and Maine was involved in CLIMAP, so it was an opportunity for Bob to get some exposure to that.

Thomas:

Was he involved in CLIMAP at all while he was here?

Hughes:

Yes, he reviewed the Antarctic chapter, which had the disintegration of the West Antarctic Ice Sheet for that Eemian experiment 125,000 years ago. He had developed a calving bay model, when an ice sheet becomes afloat and can begin to release icebergs at the calving front of the floating ice shelf. Bob’s model included the mechanism for retreat of the grounding line as the bed slopes downhill into the ice sheet. The weight of the ice pushes the bed down, and it’s already a marine ice sheet below sea level, so it’ll have a downhill slope inland. The grounding line is on this downhill slope. There’s a number of parameterizations you can have as ice is crossing the grounding line that can trigger, at least in principle, what can be an irreversible downhill retreat. He applied his model to a former ice stream in the Gulf of St. Lawrence that drained part of the former Laurentide Ice Sheet that covered much of North America.

Thomas:

This was at your suggestion—I was reading in his paper, on that.

Hughes:

I don’t know whose suggestion it was. It was a long time ago. He came up here and we had these discussions. I think he had been working on grounding-line retreat before he came, but anyway he finished that work here. He was here when it got published. “Calving Bay Retreat in the Gulf of St. Lawrence,” I think is the title of the paper. There was a big ice stream that came out of the St. Lawrence River estuary into the Gulf of St. Lawrence. Then, he and a couple of Brits applied his mechanism to the Amundsen Sea sector of the West Antarctic Ice Sheet today. We invited him to be a co-author on the Antarctic chapter of our CLIMAP book, and we applied his mechanism to collapse our reconstruction of the West Antarctic Ice Sheet. We had concave ice streams in our reconstruction, obtained by employing a mechanism for drowning the low points on the bed and generating stream flow out of sheet flow in that way, getting the low concave surface I had originally seen on the Antarctic map in 1970 by the American Geographical Society. That’s what got me started on this whole thing—that, plus talking with Mercer about his work with marine ice sheets and so forth.

By the time we had made the decision to publish our CLMAP work as a book, Thomas wanted to get his mechanism in the literature and not have to wait for it to appear in a book chapter. So, what he agreed to do was be the referee for that chapter. Denton picked the referees for each chapter, people who wouldn’t shoot it down because they didn’t believe there was such a thing as first-order glacial geology, for example, or they were stuck in some time warp that didn’t allow them to think outside the box. Because that’s what happened in Ottawa when we presented these papers at that symposium. We knew Thomas would be sympathetic to this way of getting rid of the West Antarctic Ice Sheet, so George picked him to review that chapter. Bob gave it a thorough review. Wiley Interscience published the book because all of the chapters got good reviews, and the rest is history. It’s a collector’s item now—it’s a classic.

Thomas:

There’s sort of a sense I get of Thomas is sort of an intermediate figure. I’m not entirely clear that it’s your main concern as to exactly when the ice sheet would disintegrate. And Thomas seems to be sort of a person who’s suggesting, well, there are reasons we have to believe that it could be stable or that its disintegration would be slower than is suggested. But he in turn would be considered a more sympathetic figure then say, Bentley, who becomes interested around 1980.

Hughes:

Yeah, but Bentley, he took longer to get outside the box than Thomas. Thomas has been a major influence in my career all the way along. Still is. We’ve never really collaborated very much. I read his papers, and he reads mine. We send emails back and forth and meet every once in a while and kick things around. His last big project was PARCA, that Greenland thing that NASA put together. I don’t remember what it means. Thomas measured the mass balance of the Greenland Ice Sheet for ice crossing the 2,000 meter surface elevation contour line. PARCA also involved work on some of the major ice streams that develop closer to the coast. It was an important project. There’s a whole issue right behind you of the Journal of Geophysical Research that’s devoted to all the PARCA work. Bob had his own program going that didn’t need me as part of it, you know. We think enough alike, but I couldn’t really provide anything that he wouldn’t be able to provide himself.

I was producing a book called Ice Sheets during the 1990s that updated thinking I had in The Last Great Ice Sheets, which included steady-state reconstructions of ice sheets at the Last Glacial Maximum. There’s only one chapter devoted to collapsing the West Antarctic Ice Sheet, and it was the second-to-last chapter. The last time the CLIMAP people met there was down at Lamont. There was a discussion of, can we keep milking this cash cow? What do we have to do? How do we go about it? At that time, I made a suggestion to them. I said, this has never been stated up front in the CLIMAP proposals or in any of the CLIMAP papers, but there is an underlying assumption made in picking the LGM, the Last Glacial Maximum, and the LIM, the Last Interglacial Maximum, as the two climate reconstructions. There’s an implicit assumption there that Earth’s climate machine is fundamentally stable, and the fluctuations occur within these stable limits of the glacial maximum and an interglacial maximum, and it’s basically based on the Milankovitch solar insolation signals. Probably the most well-known paper that came out of CLIMAP was one by three of the CLIMAP people: Jim Hayes, John Imbrie, and Nick Shackleton, who in Nature called Milankovitch insolation the “pacemaker of the ice ages.” It was very much looking at the Milankovitch thing as causing variations in climate known throughout the whole Quaternary, and climate change has to be confined within those insolation limits at the various latitudes. And so, if you look at the maximum perturbation at the cold end and at the warm end, Earth’s climate varies between them, so we’ve bracketed it. That was a basic philosophical underpinning for CLIMAP. But it’s an assumption—we don’t know if it’s true. During the decade of CLIMAP work, the 1970s, there were holes being drilled through both the Greenland and Antarctic ice sheets to obtain climate records from oxygen isotope ratios in ice cores. Today, trace amounts of cations and anions also provide climate records. They all show very rapid fluctuations of climate with time, and that was coming onboard during the CLIMAP years, especially toward the end.

So, I said, suppose the CLIMAP assumption is wrong. Suppose Earth’s climate is fundamentally unstable, and always searching for but never finding some stable regime. If that’s the case, what should have been studied are not these two end members that are the closest approach to steady-state conditions at the cold end and the warm end, but the times of the most rapid climate change. So, if you get some kind of climate curve that varies through time, such as temperature going up and down over time, instead of taking the tangent to the curve at the top and at the bottom, you want to take the steepest slope coming from warm to cold, and then coming back from cold to warm, because that’s when these instabilities are most manifest, causing climate to change the most rapidly. So, what you can do, if you want to keep milking this cash cow, is just say to NSF, well, our CLIMAP work during the 1970s was based on this assumption that Earth’s climate is fundamentally stable, but that’s not the only paradigm. There’s this other way of looking at it, and give us another ten years and we’ll look at that. They weren’t really ready to climb onboard with that, but it would’ve been a project of the 1980s if they had. I was getting more and more intrigued with that, and it almost becomes inescapable as these ice core records, and then the sea floor records of sediments too, show these rapid changes, you know, the Dansgaard-Oeschger cycles and the Heinrich events. It’s hard to still argue that slowly varying Milankovitch insolation is the pacemaker of the ice ages.

Thomas:

So, you essentially stayed most interested in these macro-climatological questions?

Hughes:

Well, no, I never got really interested in climate.

Thomas:

Because I know the ways science leans towards the CO2 issue after Mercer in ’78. There was a conference here in 1980 that I wanted to ask you about.

Hughes:

Yeah, we’ve had those, and they’re discussed in that thing I gave you about modeling from the bottom up. I was interested in ice sheets driving climate rather than Milankovitch, especially the termination and the ability to have rapid changes. It seemed to me insolation just wasn’t capable of delivering those things. So, I began to abandon the steady-state thinking underpinning CLIMAP reconstructions at the LGM. I mean, I think they’re okay, there’s nothing wrong with them because that was the closest approach to steady state. But the destruction of the Laurentide Ice Sheet can’t be pulled out of a steady-state model. It has to be a time-dependent model that allows for rapid deglaciation. And so, I began thinking in terms of the maximum extent of the Laurentide Ice Sheet at the LGM as not just a mass-balance steady-state regime, where there’s enough precipitation over the ice sheet that would force it to advance to its southern limits, south of the Great Lakes. In the same way, the Scandinavian Ice Sheet would be forced by the mass balance to cross the Baltic Sea onto the North European Plain and cross the Barents Sea onto the North Russian Plain. I began to think in terms of these critical thresholds that you get with the weight of the ice pushing more of the bed below sea level and creating an increasingly steeper downhill slope. That, again, goes back to the paper Thomas did for the Gulf of St. Lawrence that came out in 1977.

Thomas:

’76, I think?

Hughes:

It was 1977, but that doesn’t matter. The advance of these ice margins into mid-latitudes was not a result of an expanding volume of ice that was always close to steady state, but of crossing a mechanical threshold where the bottom of the ice sheet, which had a lot of thawed areas where lakes exist today but had frozen areas between these lakes that also became thawed. When the whole bed became thawed enough so basal melt water could begin to drown a lot of the bumps on the bed and thereby reduce ice-bed coupling which determines how high the ice can be, the center of these ice sheets collapsed and shot out the ice streams that advanced the southern terrestrial margins, and the northern marine margins, too, out to the edges of the continental shelf. When that happened, then the water that had built up under the center of the ice sheet just kind of got squeezed out under these ice streams and provided the reduced ice–bed coupling that allowed ice streams to advance so far. The advancements of the Last Glacial Maximum occurred mainly without a change in ice volume; it was just a redistribution of ice volume from being a high central dome to collapsing the dome and advancing the perimeter by way of these ice streams. That was done by reducing ice–bed coupling. Ice–bed coupling was the basis for reconstructing our CLIMAP ice sheets in the first place. We had used ice–bed coupling to tell us how high the ice could get. And the glacial geology supported that interpretation, because the Canadian Shield and the Scandinavian Shield has a lot of lakes scattered around, and those would be thawed patches; in between the bed could be frozen, and that would allow the ice to get high because there were all these frozen areas in between isolated thawed patches. Once the weight of ice got thick enough to crush basal ice into water, then all of the sudden the thawed patches would expand and completely envelop the frozen areas, and you can see that in the glacial geology. This is why the all the Paleozoic rocks have been stripped off, exposing Precambrian rocks on the Laurentian Shield in Canada and the Baltic Shield in Scandinavia. That’s all been stripped away, and that requires the bed to be thawed everywhere. So, if you reduce the ice–bed coupling everywhere, then the center has to drop down because the reduced coupling won’t support ice that high. And where will the basal water go? As I said, it will follow the linear depressions occupied by ice streams. These depressions may have been former river systems on land, or inter-island channels in the case of the marine margins. All that water will be discharged from under ice lobes at the end of terrestrial ice streams and will cross the grounding line at the end of marine ice streams. As ice streams pull out interior ice, cold upper ice moves closer to the bed and eventually refreezes the bed. Then ice streams shut down.

Thomas:

Are the time frames on these processes ever a major concern of yours?

Hughes:

Yes, but, they can be modeled. Actually, models can deliver pulses through this kind of thing. During lowering of the ice, the ice up higher is colder than ice at the bed. As ice is spreading out, that colder is ice is moving closer to the bed, and so the temperature gradient from bottom to top is getting steeper. Heat is not going though the original thickness of ice, it’s going through a reduced thickness of ice, so basal heat will be conducted up away from the bed more rapidly and eventually the bed will freeze. That will restore the original ice–bed coupling, and allow the ice to thicken again. Thinking along those lines, and getting away from a steady-state paradigm, but looking at these rapid changes that were showing up in the ice core records and sea floor sediment cores, I decided it’s time to supplant the CLIMAP vision of things with this more dynamic system where ice sheets aren’t really finding any secure steady-state regime because there’s too many things going on, basal ice is decoupling and recoupling in various places. And so, I wrote all of that up in my book, Ice Sheets, which Oxford University Press published in 1998. I spent the better part of ten years doing that. So, The Last Great Ice Sheets came out in 1981, and then I spent about ten years wondering if we were missing the main event. Our reconstructed CLIMAP ice sheets, like ice sheets today, were close to steady-state at the LGM, but should we have been thinking in terms of fundamental instability rather than thinking in terms of fundamental stability? When those thoughts had gelled to the point where I thought it was time to act on them, I began writing Ice Sheets (which is that blue-covered book over there). In it, I use glacial geology to reconstruct ice sheets for a full glaciation cycle, not just at the LGM. I don’t just use glacial geology. I also use geomorphology, the permafrost distribution, free air of gravity anomalies that give an idea of where the rebound of the land is greatest because the ice load was greatest in the past. There’s a whole suite of things in addition to glacial geology that I used to reconstruct a glaciation cycle from initiation of it and early advance, to stadial and interstadial fluctuations, and finally crossing an instability threshold that terminates the glaciation cycle, when ice sheets self-destruct. This is called a termination.

Milankovitch has a role in this. I’m not saying you can ignore it, because the insolation variations are real. You can run ice sheet models just using them, you can. There’s all these stadials and interstadials during a glaciation cycle. Ice sheets have a rapid but temporary advance followed by a rapid retreat, not retreating as far as it had been, and then another advance a little bit further, and then a retreat not quite as much. These are stadials and interstadials; that’s what they’re called. So, I identified landforms that I associated with stadials and interstadials that brought ice sheets up to the glacial maximum. Then this marine instability kicks in because the bed is depressed too far. Then, when ice sheets had gone from stadials to interstadials, instead they go from an LGM stadial to a termination. The whole ice sheet self-destructs because its center has collapsed. And then calving bays can migrate up the ice streams on the marine margins and carve out the interior of the ice sheet. Calving bays take out the accumulation zone of the ice sheet, and when it doesn’t have an accumulation zone it starves to death. So, that’s what gets rid of the ice sheet. That’s the scenario that I put in Ice Sheets. It’s treating a full glaciation cycle, whereas our CLIMAP book just looks at the LGM, the Last Glacial Maximum, and getting rid of the West Antarctic Ice Sheet at the Last Interglacial Maximum.

So, there are two quite different ways of looking at it. Each is valid in its own way, but they’re quite different. That’s basically where I am now. When you look at my paper, “Modeling Ice Sheets from the Bottom Up” in Quaternary Science Reviews, you’ll see where my current thinking is going. The East Antarctic Ice Sheet is maybe not as stable as we always thought; it might be vulnerable too. The Antarctic Ice Sheet is the only big ice sheet we had at the LGM that’s still around. The marine portion in West Antarctica has been collapsing for about 8,000 years, and if that continues, there’s a pathway into the East Antarctic Ice Sheet through this big gap in the Transantarctic Mountains I call the Bottleneck. Where the bed is below sea level, that pathway goes right to the South Pole, and it makes the East Antarctica Ice Sheet vulnerable to collapse right at its center, just like the calving bay that went up Hudson Strait into Hudson Bay and took out the Laurentide Ice Sheet right in its center. So, I’m keeping that on the table as something that could happen in Antarctica. It can happen because it has already begun in West Antarctica, and it can continue into the future for a few centuries. I think that’s a scenario that’s getting more and more probable. So, that’s where my research is right now, applying the Laurentide collapse scenario to the Antarctic Ice Sheet in the future, the whole ice sheet and not just the marine part in West Antarctica.

[Pause in recording]

Thomas:

We are back from Terry Hughes’s lunchtime talk. So, I guess what I would like to discuss right now is probably two things that I have on my list of things to talk about. One is Jim Fastook, who I don’t think I’ll get a chance to talk to personally because he said he was down in Massachusetts. Then, I also wanted to ask you specifically about the “weak underbelly” of the Antarctic Ice Sheet argument, as you termed it: Pine Island and Thwaites Glaciers. Why don’t we talk about Fastook first?

Hughes:

Well, he got his PhD in the Physics Department here doing experiments on condensation of inert gasses in cloud chambers, so it was an experimental dissertation. His undergraduate degree was at RPI, Rensselaer Polytechnic Institute. He was just basically finishing up his coursework for his PhD, when he went through the course catalog to see if there might be any course that he would be interested in taking, and he saw my glaciology course listed. I was hired in ’74, but I mentioned I spent six months out at the National Center for Atmospheric Research, NCAR, and then I came in here on January 1, 1975, so the first time I taught glaciology was the fall semester of ’75. Before coming to UM, during the spring semester of 1968 at OSU I attended lectures called World of Geology by J. Tuzo Wilson, a renowned visiting geophysicist from Canada. I was also reading a lot of the classic papers in glaciology to get familiar with it. At that time, Gerry Holdsworth was a New Zealander who wanted to drill holes through Meserve Glacier as part of his doctoral research under Colin Bull, who had just hired me at OSU. I mentioned NSF wouldn’t let Gerry go down that year because of some spot on his chest x-ray, so I was put in charge of drilling the holes even though I knew nothing about drilling and next to nothing about ice. Gerry was also interested in measuring the elevation of Mount Logan in Yukon Territory of Canada. It’s listed as the second-highest mountain in North America at 19,850 feet. McKinley is 20,300. Logan’s elevation was first surveyed after Russia sold Alaska to the United States and there was a survey of the boundary between Alaska and Canada. That boundary is not far from Mount Logan, so we could get a better elevation for Mount Logan using better surveying technology. That was quite a while ago. When did we buy Alaska, was it before or after the Civil War?

Thomas:

I think after.

Hughes:

I think it might have been after, too, but I’m not sure. Anyway, Holdsworth thought that they could have been off by as much as 500 feet, and if it was all on the low side of the measurement error, Logan could be as much as 50 feet higher than McKinley, which would make it the highest peak in North America. On the basis of that, he got some money from the Arctic Institute of North America and National Geographic Society, maybe, I’m not sure. Anyway, Gerry wanted to go up there and do a proper survey that would have a party down at some marker at the base of Logan, and then another surveying team at the top so they could do simultaneous sightings and correct for the curvature of light in the air. The summit party was supposed to be two people, and when I took a trip around the world, one of the things I did was climb Kilimanjaro, which is 19,650 feet high, so Gerry knew I could handle the altitude problem and he picked me to be with him on the summit team. I was basically his pack mule (he called me “Horse”). Anyway, that was being planned in that spring semester and it was keeping me busy. Then, there was a glaciological meeting in the late summer here at Hanover, New Hampshire, where the U.S. Army has its Cold Regions Research and Engineering Laboratory, and I attended that. So, these things kept me occupied when I first arrived at Ohio State. I wasn’t teaching glaciology there. I had a research appointment. Then I came to Maine in January of ’75, and I taught glaciology for the first time. I wrote my third and fourth ISCAP bulletins during 1974 and 1975. I began the third at NCAR, but the fourth one was done here.

Jim Fastook thought my course description for glaciology was interesting, so he took it, and he’s stayed in glaciology ever since then here at UM. The chairman of the Mechanical Engineering Department was Bill Schmidt, and he used finite-element modeling in a contract he had with the Canadian government to study heat flow in Canadian nuclear reactors. He used the finite-element method to track heat flow through the reactors. And so, he taught that course, and I advised Jim Fastook to… I don’t think he actually took the course, but he learned the method. He sat in on the course or something. Anyway, Jim picked it up from Bill Schmidt. Doug MacAyeal came here a couple years later and actually did take that course from Schmidt. So, that’s how the finite-element method entered glaciology—it entered from here before any other place that does glaciology used it. It was used here, and now it’s commonly used by anybody that does ice sheet modeling.

I said Jim Fastook did an experimental thesis, but he got interested in numerical techniques, which he didn’t need for his doctoral research, but we enlisted him to work with us on the CLIMAP reconstructions. So, Jim, Dave Schilling, a mathematician from a two-year campus of the University of Wisconsin system in a town called Rice Lake who came here for a year, and I put together the computer program for reconstructing these ice sheets from the bottom up using glacial geology, as I mentioned. And then Bob Thomas arrived as well with his marine instability mechanism, which he had just developed. Jim produced a program to apply Bob’s mechanism to the collapse the West Antarctic Ice Sheet we had reconstructed for the CLIMAP Eemian experiment. It was basically the same reconstruction we did for the Last Glacial Maximum for CLIMAP: same ice sheet; we didn’t have any reason to make it any different for that earlier time. Jim used the concave ice-stream profiles I had developed for the CLIMAP ice sheets. It was the concave profiles of ice streams produced by downdrawn interior ice that allowed grounding lines to retreat faster than they would in Thomas’s original model, which had a convex surface coming right down to the grounding line. So, it was harder for that grounding line to retreat than a concave profile, which was a continuation of the ice shelf profile inland, but climbing in elevation. So, Jim was involved in that as well, with both CLIMAP experiments.

Jim just took to modeling ice sheets, and that’s what he’s been doing ever since. He got an appointment in the Computer Science Department through the intervention of George Markowsky, who’s chairman of the department now and was 20 years ago. Jim got his tenure track appointment through George, and now he’s a tenured full professor. But the research he does is modeling ice sheets, and he models them on Mars, not just here. You know, you really should talk to Jim while you’re here. He’s on sabbatical this semester, so he’s not here full-time like he would normally be. Well, he’s modeled the icecaps on Mars. Mars has Milankovitch cycles, too, and during its axial tilt cycle, the rotational axis almost points right at the sun, so glaciers form on the mountains around the equator when that happens. So, Jim’s model generates those things. You’ve seen photographs of Mars taken by satellites that show landforms with surfaces twisted and contorted in ways that are hard to explain from anything that’s happening on Mars today. All Mars has going on today are dust storms, you know. Well, Jim’s model produces big glaciers under the contorted surface rubble, and the contortions reveal the flow pattern of ice below. The rubble has to mimic the pattern of ice flow underneath. There’s no question that if people ever go to Mars, they’re going to have all the water they want because that cover of rubble is fairly thin. It’d be pretty easy to go through it and get to pretty clean ice under it, all over the planet where you see these features, which are common.

Thomas:

How frequently has your work intersected with his? I see your names on the same papers from time to time.

Hughes:

We haven’t done that much collaboration. He doesn’t publish much under his own name. His model is a three-dimensional time-dependent version of that Budd, Jenssen, and Radok model that the Australians put out in 1970. That was a pioneering model, and all modeling activities are basically improvements of that one. Two of those three were meteorologists, Budd and Radok, first, before they went into glaciology, and so they were looking at modeling ice sheets basically from the top down, you know, dump the snow on and the ice builds up, and after a while it begins to spread out, but surface melting keeps it from spreading too far. Eventually the backward melting rate will equal forward flow rate, and then the ice front stays put. Surface lowering is built up by snowfall; snow will tend to restore the original ice elevation. So, the whole thing, when it’s in a steady state, doesn’t change its size or its shape. But if you want to model it over time, you’ve got to grow it from virtually nothing, just as snow on highlands that builds up over time. And if you want to get rid of it at the end, you’ve got to have some mechanism that’ll deliver one of these collapses that I talked about earlier. You can even actually get rid of the whole ice sheet quickly that way, whereas without it the ice sheets are still here. The Laurentide Ice Sheet is still here today. That’s the big North American ice sheet that attained its maximum size about 20,000 years ago and is now gone.

One thing Jim does is work with glacial geologists from Canada and Scandinavia who are looking at the whole glacial record on the landscape, not just at the maximum or during the last retreat, but through the full glaciation cycle, and locating ice streams and places where the bed is frozen or thawed, and how that changes over time. When they think they’ve got it figured out, so they’ve mapped the basal thermal regime, they’ll come over here and sit down with Jim with his model. He calls it UMISM, University of Maine Ice Sheet Model. He will target the places where they think they understand the basal thermal conditions dictated by the glacial geology. He has enough things that he can alter in his model within acceptable limits, like the surface accumulation rate and the hardness parameter for ice and the roughness parameter for ice sliding over the bed, to generate the basal thermal conditions deduced by the glacial geology. He does that to deliver the basal thermal regime that these glacial geologists believe is reflected by the glacial geology. So, in that sense, his top-down model uses bottom-up information, and went with that information, the top surface of the ice sheet can be adjusted to be compatible with observed bed conditions. So, it’s kind of an iterative thing, you know, with the new bottom conditions he’d adjust the top conditions, then he gets the bottom conditions for the new top conditions, but he still has to sustain the bottom conditions because that’s model input from the glacial geologists. So, he’s able to get the ice sheet to conform with the glacial geology at any time during the glaciation cycle where they think they have it nailed now. That’s what he does in those papers they publish with him. The first authors on those papers are the guys who do the fieldwork, so Jim is listed after them. There are several papers like that, but not too many because the fieldwork takes a long time to conduct, and then to map and interpret, getting dates if possible. So, it stays in the pipeline for quite a while before a paper comes out at the other end. But that’s what he’s been doing the last several years. There are not an awful lot of papers to show for it, and the first authors are always these other people.

I haven’t coauthored a paper with him for quite a while. We had one that has been rejected by two different journals that’s called “The White Hole.” It’s a concept that I introduced 15 years ago, something like that. When you go into a glaciation cycle, the sea level drops almost as fast as it rises coming out of the cycle. You see that on the oxygen-isotope curves that are proxies for ice volume, which is a proxy for sea level. So, what mechanism is there that can get ice sheets to build up as fast as you can collapse them and disintegrate them? It’s not easy to imagine how that might happen. Well, in the white hole concept, I have continuous sea ice in the Arctic Ocean right up to the coastlines of Canada and Siberia, so that all the big rivers in Siberia and Canada that flow into the Arctic Ocean flow over the top of sea ice, which is a year-round condition going into initiation of a glaciation cycle. So, all that water flows out over the top of the sea ice and then just freezes, summer water that freezes in the winter. That thickens the sea ice and eventually it grounds. It grounds first on the shallow continental shelves. So, you’ve got s system where all the precipitation from snow over the surface and coming in from the rivers from rainfall or snowfall over the land, it all comes into the Arctic Basin and it doesn’t get out. The only outlet is a narrow gap between Greenland and Spitzbergen, and that’s too narrow a gap to discharge all the ice that’s coming in from the whole Arctic Basin plus all the watersheds in Eurasia and North America that feed into the Arctic Basin. So, it’s like a terrestrial counterpart of the black holes at the centers of galaxies, you know, all the stellar matter goes in and none comes out. In our Arctic, all the moisture, either ice or snow, comes in and doesn’t get out, or escapes only through a very narrow passage. Well, that means everywhere around the perimeter where floating ice is becomes grounded on the shallow continental shelves, all precipitation that falls on those regions and in the watersheds and the rivers that come into it never gets back to the ocean. And so, to the extent that all that is supplied by evaporation from the ocean and then precipitates over these broad areas, producing a white hole, sea level has to come down—it has to come down fast because of these are big areas. The areas of these watersheds and continental shelves are bigger than the areas of Northern Hemisphere ice sheets at the Last Glacial Maximum. So, they’re enormous areas, and all the rain and snow that falls over them doesn’t get back into the sea, and I think that’s why sea level lowers rapidly at the beginning of a glaciation cycle.

But referees of our paper aren’t buying into that. The concept is in my book Ice Sheets and I have a paper introducing it. But Jim’s UMISM ice sheet model will actually generate the ice cover that blocks up the Arctic Basin and creates the white hole conditions, and actually calculate how fast sea level will fall by impounding all that precipitation. We’ve got people who can’t see outside the box. Get one of them as a referee and you’ll never get anything published. Death is a blessing not a curse. It takes out all these creeps sooner or later. Preferably sooner, but even the ones who hang on are eventually out of the loop because of other circumstances.

Thomas:

I interviewed Jay Forester once, and he had similar opinions, actually, how ideas proceed.

Hughes:

That’s the story of the history of science, if you really look at it carefully.

Thomas:

One obituary at a time, as they say. Let me ask you a little bit, actually, in terms of the reception of ideas about framing concepts. It seems to me a lot of what you do is sort of generate ideas about how to represent the climatic record and the positions and morphology of ice sheets and so forth. You actually frequently use fairly colorful terminology, the “white hole” or the “weak underbelly,” as we were mentioning a little while ago.

Hughes:

Well, that one was when we were doing the CLIMAP reconstruction for the West Antarctic experiment, collapsing the West Antarctic Ice Sheet. Denton and I were looking at that very map, the American Geographical Society map, and we were agreed that the collapse had already taken place in the Ross and Weddell embayments to produce those big ice shelves. And the rest of West Antarctica is connected to the East Antarctic Ice Sheet through what we call the Bottleneck, that’s that gap in the Transantarctic Mountains. Or it fronts the Amundsen Sea. Or there’s the Antarctic Peninsula that’s connected, too, but that’s a mountain spine that’s not really vulnerable to rapid collapse of the ice sheet, and won’t exert any control on collapse in terms of the marine triggering mechanism. Right there in the Amundsen Sea is Pine Island Bay. It’s a polynya kept free of sea ice by katabatic winds coming down Thwaites and Pine Island Glaciers. So, we thought if Pine Island Bay expanded to the south, like the Ross and Weddell embayments already have, that’d get rid of the West Antarctic Ice Sheet because about a third of West Antarctic ice goes into Pine Island Bay now. If it expands southward, the drainage divide will retreat southward as well and eventually grab the rest of the West Antarctic Ice Sheet and take a lot of it out through Pine Island Bay. We were wondering what some kind of phrase that would capture the public imagination. During World War II, Churchill thought that the best way to invade Hitler’s Europe would be from the Mediterranean side, which he called the soft underbelly of Europe. So, that’s what the Allies did; they came to Sicily and then the Italian boot. It wasn’t soft at all; it was a hard grind up the Italian Peninsula. Normandy was much faster after the Allies got out of the hedgerows. They had one little setback during the Battle of Bulge that lasted a few weeks, but then it was a straight shot to Berlin. They’d have gotten there before the Russians if Churchill hadn’t handed over Eastern Europe to Stalin at Yalta. So, I never understood why… Did I say Churchill? I mean Roosevelt.

Thomas:

You said Churchill.

Hughes:

Yeah, Roosevelt. Well, they both did, you know, they both met with Stalin at Yalta. Churchill went into World War II to save Poland from the Nazis, and he ended up handing it over to Stalin and the communists, and Roosevelt did as well. So, I’ve never really seen those two guys as the great heroes in history books, because they basically handed over half of Europe to the worst despot of the 20th century. Well anyway, and for what? They didn’t have to. The Allied forces were stronger. We had the atom bomb, so we didn’t have to surrender half of Europe to the Red Army. Well, that’s another story. Churchill should have known better. As an English officer in World War I, he witnessed the slaughter of Aussies and Kiwis ordered by Brit generals to attack Turkish machine guns at Gallipoli, another “soft” spot on the underbelly.

So, I don’t know, one of us had mentioned that this might be the soft underbelly of Antarctica. But we didn’t want to use the word “soft,” because Churchill had applied that to Europe where it wasn’t so soft, you know? And someone would point that out. They would recognize the Churchillian expression, and that part of the Antarctic Ice Sheet is still there, so maybe it’s not so soft either, certainly wasn’t as soft the Ross and Weddell sectors—they’re gone. So, we thought, well, let’s call it weak. Weak isn’t the same as soft, but it connotes the same thing, and the remaining West Antarctic Ice Sheet may collapse into Pine Island Bay as it advances southward. So, that’s how the “weak underbelly” concept got started. I put it in a letter to the editor of the Journal of Glaciology titled, “The Weak Underbelly of the West Antarctic Ice Sheet.” That’s the place where the concept first appeared. It caught on and glaciologists began to use it as a catch phrase to open the sluices of government funding. But yeah, it got started just looking at the American Geographical Society’s 1970 map of Antarctica on that wall there.

Thomas:

I was just reading a recent review by David Vaughn about various paradigms concerning the West Antarctic Ice Sheet, and he was mentioning the resurgence of a paradigm when Pine Island and Thwaites are the important things to look at. And he actually mentioned the weak underbelly as possibly too dramatic of a term. That was kind of what I was getting at in my original question.

Hughes:

Well, it might be, you know? Who knows that it’s weak at all, if it’s still there? But you don’t get any money from the government by saying nothing’s going to happen, do you? They’re not going to pay for that. You’ve got to have sea level coming up 20 meters in 100 years, and then they’ll take notice. So, that’s how it works. Disaster has to be tied to the election cycle. We see that today in the “man-caused climate warming” scam.

Thomas:

I just get the impression, talking to different people like Charlie Bentley, and after I got snowed out of my previous trip here last February, I spoke to Bob Thomas on the phone for an hour, and I’m just wondering to what extent the language that one uses in putting together a paper, the tone is important in terms of the acceptance of ideas, in terms of getting them noticed in the first place versus having them be accepted. Because Charlie Bentley was talking about his disagreements with Bob Bindschadler, and how when they came together to write a review article they realized that they didn’t really have very many differences, because Bentley was arguing against the idea that there would be disintegration of the West Antarctic Ice Sheet in 200 years, and Bob Bindschadler said, “Well, it could disappear within a couple of thousand of years.” It turned out that it was just simply a matter of timescale, but one sounds more alarmist because you’re saying, well it could disintegrate.

Hughes:

Well, the Eemian Sea level in just a very few hundred years came up six meters. So, if the West Antarctic Ice Sheet is a cause for that, that’s the timeframe.

Thomas:

Yeah, as I’ve been looking at just how the conversation unfolds in the articles, I see that for you the paleoclimatic evidence suggests that there must be a mechanism, and that the object is then to seek that mechanism out that could explain those changes, whereas others, such as Bentley, look more for something that we can see today as to whether or not…

Hughes:

Well, you probably do see it today in some kind of embryonic form.

Thomas:

Well, I mean, speaking back circa 1980, given what was known then…

Hughes:

The processes are going on, but it’s just not ubiquitous yet. I think once it gets going, it’ll be very fast. When the Ross and Weddell Sea sectors collapsed, ice was coming in from three sides—east, west, and south—and leaving only on the north for both of those sectors. What’s left of the West Antarctic Ice Sheet is ice is coming out on three sides—east, west, and north—and, if it’s coming in at all, it’s coming in through the Bottleneck very slowly from the south. So, that alone tells you that when it goes, it’s going to go a lot faster than coming in from three sides and going out from one. At best, in from one and going out three, I can tell you it could happen a lot faster, like ten times faster, just using those numbers. So, what took 2,000 years then could be done in 200 years now. That’s about the right timeframe for the West Antarctic Ice Sheet. Most of it collapsed in about 8,000 or 6,000 years. Most of it was getting down pretty close to sea level, but that would be the time when the sea level would be coming up. Once it’s a floating ice shelf, it’s not contributing anything to sea level.

So yeah, Bentley, it’s interesting though, he was the first one to have a positive reaction to the possibility of thermal convection in ice sheets, so he’s not inside the box all the time; he gets out once in a while. He’s made an enormous contribution to Antarctic research. It’s good stuff, you know, it’s stood the test of time. Not a hell of a lot of speculation there with his stuff—pretty much all solid data.

Thomas:

So, starting in 1980s, how involved have you been with the assessment process of the West Antarctic Ice Sheet for policy reasons or in terms of the Department of Energy?

Hughes:

Oh, from the beginning right up to the present. But I have never been part of the field teams working in West Antarctica because of CLIMAP—that took my attention during those early years, the 1970s. And I made a tactical decision: I decided that the West Antarctic Ice Sheet in those two Ross and Weddell sectors had basically collapsed. I mean, there wasn’t going to be a lot more ice being discharged by those ice streams. And I was interested in future collapse, and the Pine Island/Thwaites Glacier aspect didn’t occur to me right away. That came on board around 1980. My letter to the editor is around ’81 or something like that, right about the time The Last Great Ice Sheets came out.

Thomas:

The paper came out in ’81. I think you’d been circulating the idea since the late ’70s.

Hughes:

Yeah, probably submitted it in ’80 or something like that. But anyway, ’78-’79 was Byrd Glacier, and I’d been up to Greenland for Jakobshavn Ice Stream in the early ’70s. So, I was thinking of to what extent could the Greenland and East Antarctic ice sheets also be unstable, and they just haven’t manifested it yet, whereas the West Antarctic Ice Sheet has. So, the West Antarctic Ice Sheet is the end of this line the way it is today, rather than… And if we’re interested in future sea level rise, maybe you’ll want to look at other places that haven’t collapsed that much yet. So, I was thinking of Byrd Glacier as the biggest ice stream coming into the Ross Ice Shelf as maybe being able to pull out a lot of East Antarctic ice. It does have the biggest drainage basin in East Antarctica. Its drainage basin is big as the whole grounded West Antarctic Ice Sheet. And Jakobshavn Ice Stream (or Isbrae) is the fastest in the world, comes into a fjord with a floating part that’s only about six kilometers long, so there’s very little buttressing by an ice shelf there. Whereas Byrd Glacier comes into this big Ross Ice Shelf the size of Texas, so it’s quite firmly buttressed. And there’s surface melting on Jakobshavn, and that water can get down and lubricate the bed through crevasses, and it’s moving seven or eight times faster than Byrd. There’s much less buttressing, much more possibility the bed has got a lot of water down there.

So, I was thinking of these two ice streams as kind of bracketing ice stream behavior, where you have relatively strong ice–bed coupling under Byrd Glacier because the only water available is going to be what’s generated at the bed itself; you’re not going to get any surface water down there. And then it’s got the big buttressing ice shelf in front of it. That’s sort of an ice stream that has a maximum stability because of constraints on fast flow. It’s still flowing pretty fast. It’s flowing faster than any West Antarctic ice stream coming into the Ross Ice Shelf. Byrd Glacier has a simple geometry, you know, it’s going through an almost parallel-sided straight fjord, and it’s more accessible than the West Antarctic Ice Sheet. It’s a short hop from McMurdo Station. So, I see that as representing the most confined and contained example of a major ice stream, and Jakobshavn is the most unconfined and uncontained example in either Greenland or Antarctica. So, if I study those two ice streams, instead of other ice streams, I’d be sort of bracketing extremes in a kind of life cycle for ice streams. Byrd is at the most constrained mature stage and Jakobshavn is at a highly unconstrained dynamic stage that, if duplicated by other ice streams, could cause the Greenland Ice Sheet to self-destruct. If you go to the end of the life cycle for ice streams buttressed by a mature ice shelf, you’re looking at the West Antarctic ice streams. They’ve pulled out about as much ice as they’re going to. So, I wasn’t interested in ice streams at the end of the line but at the most stable and unstable stages. That’s why I picked Byrd and Jakobshavn as the focus of my field research and never participated in studying the West Antarctic ice streams that attracted everyone else.

Thomas:

Right, that was the whole Siple Coast Project in the 1980s.

Hughes:

But I was the first one to do some studies of Thwaites and Pine Island glaciers in the field, once I realized that was where the future action would be. Then I got involved and some ice breakers were able to get us in there (a team headed by Tom and Davida Kellogg from Maine, John Anderson from Rice University, and Stan Jacobs from Columbia) to map and sample the floor and to collect oceanographic data in Pine Island Bay. I got ice samples on Pine Island Glacier and erratic boulders from a lateral moraine for exposure-age dating. My graduate student, Dean Lindstrom, used Tricamera photos and Landsat imagery to get velocities of moving crevasses on both ice streams. The British Antarctic Survey people got interested, too. That’s in the slice of the Antarctic pie that the Brits claim. And Rutford Ice Stream across the ice divide from Pine Island Glacier, they’ve done a lot of work on it. They did the first radar sounding to get the ice thickness from those ice streams, and they remain active right up to the present time. So, to the extent I’ve done any work in West Antarctica, it’s been with Thwaites and Pine Island Glaciers, very preliminary stuff, you know. The real serious fieldwork I haven’t done. It was a tactical decision I made to study Byrd and Jakobshavn, because that’s where I could look into the future, not look back into the past by studying Siple Coast ice streams that have shot their wad. And I stick by that, even to this very day, even though there are all these Siple Coast papers.

There’s a book right over there about the dynamics of the West Antarctic Ice Sheet, reporting all that stuff. And it’s very important stuff, you know, very important insights on ice-stream dynamics by an awful lot of people. But I would argue the tiny fraction of that effort that I devoted to Byrd and Jakobshavn is more important than all the time that they’ve devoted of these ice streams that are basically at the end of the line. But they are still ice streams. People learned a lot about ice-stream dynamics by studying them. And it was not a wasted effort by any means. But it just wasn’t where I… It was a tactical decision I made with a strategic objective of looking into the future, and that’s why I picked the two ice streams I did. And I couldn’t get anybody else much interested in them until CReSIS came along. CReSIS is the Center for Remote Sensing of Ice Sheets at the University of Kansas. You should talk to Prasad Gogineni who runs it. Is that a name that rings a bell with you?

Thomas:

Actually no.

Hughes:

That’s where all the action is right now and will be for the next five or six years, the University of Kansas.

Thomas:

What’s the name again?

Hughes:

CReSIS, Center for Remote Sensing of Ice Sheets.

Thomas:

Is Kees van der Veen involved in that?

Hughes:

Yes, he’s down there. He was at Ohio State, moved down there within the last year. And I’m part of it. Jim Fastook’s part of it. The first five years was funded for $20 million. There’s a year and a half to go on that funding, and then if we deliver good results there’ll be another five years of funding for a similar amount, around 20 million bucks. So, that’s 40 million bucks being pumped into looking at the response of these two ice sheets to global warming. So, that’s where the action is. It’s where the foreseeable future is. So, you most definitely have to talk to Siva Prasad Gogineni. He’s an Indian, Hindu, not Muslim Indian. Siva is one of those Hindu gods who go around destroying things. He goes by S. Prasad Gogineni. He emphasizes the Prasad part, not the Siva part. But if he’s interested in the destructions of ice sheets due to global warming, maybe “Siva” is the name he should use. Prasad had been in charge of the NASA glaciological program after Bob Thomas got tired of juggling funding proposals and wanted to do more research himself. Then he put Prasad in charge, and that’s where I first met Prasad. When Prasad also wanted to get back into research, he returned to the Electrical Engineering Department at the University of Kansas to continue developing radar technology for getting through these ice streams. They have crevassed surfaces, so a lot of radar energy gets scattered and lost in surface crevasses. It takes special techniques to be able to get a good bed reflection for ice streams because of surface crevasses. And for Jakobshavns Isbrae he was able to do it. It’s just in the last year he was able to finally pull it off. I’ll retire soon, so I won’t be part of the second five years of CReSIS, which will begin in 2010. But by all means, you’ve got to talk with him. And van der Veen would be a good guy to talk to as well, if you haven’t already. He’ll tell you how full of shit T. Hughes is. Then you’ll get another side of what I’ve been telling you. He’s a very good glaciologist by the way. He’s got three books on glaciology: Ice Sheets and Climate, Dynamics of the West Antarctic Ice Sheet, and Fundamentals of Glacier Dynamics. All three of them are right here. Two of them were with Hans Oerlemans, who’s a first-class climate modeler.

Thomas:

Yeah, yeah. He gets involved in this whole thing.

Hughes:

They’re both Dutchmen. Hans Weertman is Dutch. That’s a Dutch name.

Thomas:

Yeah, his parents came over actually.

Hughes:

Born in Alabama, though. Did you ever talk with Hans Weertman?

Thomas:

Yes, in August I went to Chicago…

Hughes:

His parents were born in Holland?

Thomas:

Yeah, his parents were born in Holland and then he was born in Alabama and then went up to Pittsburgh, I think.

Hughes:

So, these Dutchmen, you know, with their country below sea level, they take more of an interest in ice sheets than maybe the rest of us. [Laughs] Because Kees is Dutch, and Oerlemans and Weertman, and the editor-in-chief of the journal, Antarctic Science, I think he’s Dutch. He’s got a Van der-something name. And there’s been a Dutch president of the International Glaciological Society. So, the Dutch, they have an oar in the water for all this stuff.

[George Denton joins]

Denton:

I’m not a glaciologist, so I haven’t had that much to do with all this.

Thomas:

Well, that’s all right. I just want to get everyone’s perspective on it who’s been involved with the science of what’s going on. In fact, it’ll actually be pretty useful to me because I have been speaking with mostly glaciologists, so an alternative perspective would be very useful.

[Background discussion]

Hughes:

I’ll just turn it over to you. I think he’s probably gotten everything out of me that’s worth getting.

Denton:

I’m not a glaciologist, so I have not worked on the glacier itself. I’m a glacial geologist. I just worked for 30 field seasons in Antarctica trying to reconstruct the past history of the East Antarctic Ice Sheet and the West Antarctic Ice Sheet. I finished fieldwork there about six or seven years ago. I began in the ’60s. So, we had papers beginning in the ’60s, culminating in a volume that was put out in 2000 reconstructing what the West Antarctic Ice Sheet did during the Last Glacial Maximum, as well as the East Antarctic Ice Sheet. And then it’s retreatal history to the situation it’s at today. I suppose this could be considered background for the overall WAIS project.

Thomas:

I think so.

Denton:

Fairly important background, actually. We did most of the reconstructions of the ice in the Weddell Sea, the Ross Sea, the Amundsen Basin, and we put the first ones in a book that Terry and I put out, The Last Great Ice Sheets, back in 1981 with Wiley InterScience. And the last one was a compilation. I don’t know if you’ve seen the compilation Geografiska Annaler published in 2000?

Thomas:

No, I don’t think I’ve seen that one.

Denton:

Oh, well, there’s a lot of reconstructions in there as well. And so, we gave some of the background and the chronology. We have a lot of radiocarbon dates of the maximum of the last glaciation and how it fits into the rest of the world, as well as the configuration of the ice sheet at that time. We can do that as well. Because see, glaciologists couldn’t do that, so we could complement what they were doing. And then the history of recession since the Last Glacial Maximum, most of which I think has been pretty recent. And so, I worked in the Dry Valleys region, and back in the early ’70s and late ’60s out in the islands of the Ross Sea looking for erratics on top the islands. And then later on, in northern Victoria Land and the Transantarctic Mountains south of McMurdo, because when ice built up in the Ross Sea it dammed up ice flowing from East Antarctica through the outlet glaciers like that, and so we looked at the seesaw effect. Terry was with me, too, back in ’78-’79. And then the Ellsworth Mountains, the grounding line between the Weddell Sea and the West Antarctic Ice Sheet. There’s beautiful trim lines there, gorgeous trim lines that we could reconstruct. And at Beardmore Glacier, we did the work at Beardmore Glacier, the Hatherton Glacier, Darwin Glacier, Byrd Glacier, Reeves Glacier, lots of places. It took 30 field seasons. It didn’t start because of the West Antarctic Ice Sheet project. It started because of something called CLIMAP. CLIMAP was an instrumental project that really started modern-day paleoclimatology. We needed to reconstruct the ice sheet in three dimensions as it existed at the LGM.

Thomas:

Maybe you could tell me a little bit about that. You were in CLIMAP before Terry came here. So, maybe you could tell me a little bit about your own experience.

Denton:

Well, I had worked in Antarctica in the ’60s when I was still at Yale, and had established to my own satisfaction that the West Antarctic Ice Sheet had in fact grounded out to the continental shelf in the LGM and its basic dates of recession. And I was working elsewhere after that. I was working Yukon Territory and Lapland, and I had abandoned Antarctica. That was back in the late ’60s. And then John Imbrie, who was a professor at Brown, he was a paleontologist who had moved to Brown as chairman, and he was working on Paleozoic paleontology, and he got interested in the Quaternary. He started to work in Quaternary foraminifera, and he made some transfer functions that allowed him to reconstruct sea surface temperatures from planktonic foraminifera. And he was excited about this. He went to INQUA in 1969—it was held in Paris in September of ’69—to give a paper about his breakthrough for quantitative sea surface temperatures. Sea surface temperatures are important because the atmosphere heats from below, as you know. And so, he went to his session at INQUA and only two people showed up. One was from China and didn’t speak any English, and the other was Nicholas Shackleton from Cambridge University. Shackleton turned out to be one of the most famous of all paleoclimatologists. He was just finishing his PhD at the time. What Shackleton had determined was that the O-18/O-16 fluctuations in deep-sea cores didn’t represent temperatures, largely as it was thought then, but rather they represented ice volume changes—largely, not completely. But the minute he recognized they prominently represented ice volume changes, he knew that he had a unique stratographic tool to tie the oceans together. Because within the mixing time of the oceans, the O-18/O-16 ratios would, for example, allow him to pick out the LGM everywhere in the ocean—he could pick out the determination everywhere in the ocean from the O-18/O-16 signatures. It was a major breakthrough. Nick came to hear Imbrie’s talk. I was at that INQUA, but I didn’t go to Imbrie’s talk. I didn’t know Imbrie from a hole in the wall. And I’ll show you. I’ll be right back. This will show you how this all happened. Terry’s not aware of any of this.

Thomas:

I should mention for the recording here that we’re speaking with George Denton who has just come in, and he will be right back since he’s just left the room.

Denton:

Well anyway, what happened was that Shackleton and Imbrie got together and they designed CLIMAP, because Imbrie had a way to produce the sea surface temperatures and Shackleton had a way to do the stratigraphy, and so they could now have the potential to produce sea surface temperatures for the entire ocean surface. At the same time, atmospheric climate models were being developed at GFDL, and Larry Gates at Oregon State was developing them. These were primitive models at the time. But they saw that for the first time they could put together—

Thomas:

Sorry, GFDL, that’s at Princeton?

Denton:

Yeah, Geophysical Fluids Dynamics Laboratory. There’s a young Japanese scientist there by the name [Syukuro] Suki Manabe at the time, who became famous after that. And Joseph Smagorinsky was running it at the time. So, Imbrie and Shackleton got together and they started to design this project called CLIMAP, in which they wanted to reconstruct the surface of the Earth at the LGM using sea surface temperatures, and then the sea level lowering because it produced new land topography, and then the huge white ice sheets, the big white mountains that formed in the north. They could use that as the input into these primitive atmospheric models. They’ll see what they produced for a climate at the LGM. So, Imbrie went down, he took a few of us including me, down to GFDL, and that would have been I think 1970 or 1971, and he presented this scheme to Smagorinsky. Up till then the atmospheric models had never worked with any of us, and they went for it. Manabe was there, and Smagorinsky, and they thought this was a heck of a good idea. The reason they were interested was they were going use their climate models for forecasting, right. But if they couldn’t hindcast, how could they trust their forecast, you see? They wanted to see what the model gave under completely different boundary conditions of the ice age. And so CLIMAP was put together. And since I knew Imbrie pretty well by that time—I didn’t know him at all by ’69—this team was put together. We hired Terry at the time, so we carried out combined glacial geology and glaciology, reproduced the ice sheets, and we came out with a book, The Last Great Ice Sheets.

But in the meantime, the most important document I think that’s ever come out to push atmospheric research in the United States is one, “Understanding Climatic Change: A Program for Action,” 1975. That was put together when the CLIMAP thing started, and the committee had some of the most famous people in the world on it at that time. This set the scene for CLIMAP, too. It had Larry Gates, who was a modeler; Wallace Broecker, who’s still at Lamont, he’s at Columbia; had Kirk Bryan Jr., who was Kirk Bryan’s son. He was the oceanographer at the time. It had Jule Charney from Massachusetts Institute of Technology, John Imbrie, Edward Lorenz. These are the guys who originated the conveyer belt sort of thing. Suki Manabe, the one I mentioned, was on it. Jerome Namias from Scripps and Henry Stommel from Massachusetts Institute of Technology. So, this was the group right here. And it produced that program which started the CLIMAP programs in the United States.

With this program in action, we turned to the [NSF] Division of Polar Programs, and we asked them, can they give us a hand? We needed to reconstruct for this program and understand the history of the Antarctic Ice Sheet. It wasn’t primarily because of the possibility it would collapse; it was just to reconstruct its history so we could fit it into this whole global scheme, along with Laurentide Ice Sheet and others. And so in The Last Great Ice Sheets, we have a long chapter about the West Antarctic Ice Sheet. And as we were developing it, Terry and I recognized that Pine Island Bay was a weak spot, and Terry went on to publish his paper. At that time I didn’t join Terry in that. I believed it thoroughly, but there were other reasons I didn’t join him on that.

Hughes:

It was just a letter to the editor in the Journal of Glaciology.

Denton:

Yeah, it had developed from these things we were doing. And we produced reconstructions, and we’ve been refining them ever since, including the West Antarctic Ice Sheet. So, I wasn’t involved in the collapse business; I was involved in ice-sheet reconstructions, the background.

Thomas:

That’s certainly been a significant part of Terry’s perspective on the problem.

Denton:

The whole history, yeah, he and I worked together on this for thirty years now. Yeah, I would say that geological history has helped, hasn’t it Terry? The glaciologists had no clue what went on before yesterday. So, we’ve been all around the Antarctic. We got all the trim lines set up and the three dimensions set up, and I think we have it basically right. There are some small disagreements now. Richard Alley and others think that Siple Dome on the Siple Coast of West Antarctica hasn’t—I think we’re right. [laughs] I know we’re right. They think that it wasn’t quite as thick as we made it. There are little details they go over, and I think they’re wrong actually. But I don’t care anymore. I’ve been away from this for six years. I don’t care if it’s 100 meters higher or lower in Siple Dome. It’s a detail. So, I finished basically in the year 2000. Have you seen the publication we put out in 2000?

Thomas:

That was the one you were just telling me about?

Denton:

Yeah, Geografiska Annaler. I published one more paper with Terry. Remember the one we published in 2002 about the LGM, in Quaternary Science Reviews? But since then, I’ve been involved with New Zealand and South America and Greenland, places like this. Our last paper just came out. We reinterpreted Antarctic ice cores, came out in Nature Geoscience about three weeks ago about how to interpret ice cores. We didn’t like the interpretation of Antarctic ice cores that’s going on now, so we put another interpretation out. I can give you a PDF of that if you want.

Thomas:

Okay. Up until then has it been primarily the polar ice sheets and glaciers that you’ve been working on? I’ve looked over your papers, and it seemed to me they were all over the world, so...

Denton:

Yeah, I work all over the world. I worked at Alaska, Lapland, Greenland, and 30 years in Antarctica. Right now I’ve been working in New Zealand and South America trying to tie those… We’re interested in the climate history, not just for the collapse of the West Antarctic Ice Sheet but what drives ice ages and how the whole thing fits into the Milankovitch theory. But I just didn’t believe what the ice core people were saying. They were claiming that lack of a signal from the north miraculously got transferred to the Antarctic ice cores. And Peter Huybers from Harvard, he and I came up with a different idea how it works, and we came up with a slightly different idea how the Greenland one works. We published that after working in Greenland.

Hughes:

I have that laying around here someplace.

Denton:

If you don’t want that I’ll take it. I don’t need one. You don’t need that, do you?

Hughes:

It’s the only one I’ve got.

Denton:

Well, that was a seminal book right there. (Paul [Darrell?] said he had another copy of one. I’m dying to get another copy of that. It just brings back old memories. I worked on that, too.) So, that’s how we designed it, and that’s those ages, and right now I’m working ice age theory. I never concentrated… Well, although I did. The geological background of the West Antarctic Ice Sheet is brought up again and again and again in these discussions, so we’re the ones who did it. It took us 30 years, whether they consider that important or not… Terry does know, but I don’t think the other ones do.

Hughes:

Brought a lot of money to a lot of people.

Denton:

Yeah, he and Mercer started it.

Hughes:

Kept glaciologists in business for 30 years or more.

Denton:

Yeah, that whole West Antarctic Ice Sheet, Mercer started it, and I guess I was the first geologist to work on it.

Hughes:

I never got a penny for all that work on the Antarctic Ice Sheet.

Denton:

His paper in ’73…

Thomas:

We were just mentioning that it was ironic that you weren’t involved in the whole Siple Coast.

Denton:

Oh no, no, no, no, no, no. The way science works is the minute there’s a good idea, they all pachoom like this on it, and they all produce little postage-stamp contributions to it. Frankly, that’s what I think they are. There’s been no big break through since Terry’s paper of ’73 and Mercer’s paper of ’68. As far as the geological construction is concerned, there’s been no breakthrough since our early ones 30 years ago. There are refinements. And because of its potential for sea-level change, in fact, in the globe it’s become an important problem. It’s not particularly an important scientific problem because it’s just an important problem akin in the way I would think of it that a bridge might break and cars fall into the river. I don’t think it’s an important scientific problem. The important scientific problem is the origin of ice ages, and this is an appendage to that. It’s an important problem for humanity, whether that ice sheet collapses because of the CO2 disaster and all that sort of thing, but it doesn’t affect ice age theory very much.

What does affect ice age theory, and where I think that he’s made the fundamental contributions, is that in understanding how the whole thing works—and he was one of the people who started with his paper in ‘74 on ice streams in Antarctica—how ice streams work and how they interact with ice shelves and how the buttressing effect and how the whole thing is pinned together, I think is absolutely fundamental to ice age theory. The reason I think that is because, when it’s applied to the large ice sheets in the north, it puts an ice sheet like the Laurentide Ice Sheet in a situation where if it builds up to be a large ice sheet and depresses the bed beneath it, it becomes mechanically very much like the marine ice sheets in Antarctica. And that to me is the enormous breakthrough. Whether that one actually collapses some time is an engineering question.

Thomas:

Well, I noticed you published a paper in ’99 on the continued moving of the grounding line and suggested that it wasn’t related to any of the… that it was not human involved or anything of that sort as they’ve been trying to assess. Is that right?

Denton:

To whose grounding line? No, I didn’t say… The past grounding line, yes, that’s right. That’s ’99.

Thomas:

The past grounding line, that it continues to move in the same way. Is that correct?

Denton:

The grounding line’s been moving back through the Holocene. That’s not caused by humans. And if it’s continued to move back now, I don’t know if it’s a continuation of that Holocene retreat of whether it was triggered late in the de-glaciation. But to get back to the fundamental contribution, I think the fundamental contribution of Terry’s work in Antarctica has been not just to understand the West Antarctic Ice Sheet, but to understand the northern ice sheets, because I think that the fundamental climate changes at the end of the ice age are related to instabilities of the Laurentide Ice Sheet of the same sort that go on in Antarctica. The great termination of the last ice age I think is—and I think a lot of people think this—is connected to the dynamics of the Laurentide Ice Sheet, its collapse into the North Atlantic with the subsequent changes in southern oceans and CO2 rise and that sort of thing. But they all come back to this fundamental understanding of how the mechanics of ice sheets work, which came out of the early work. That was basically known, I would say. We have a lot of it in The Last Great Ice Sheets. I would say it’s basically known by the late ’70s, the fundamental parts of it. Terry?

Hughes:

Yeah. I mean, nobody is alone in developing these things. John Mercer and George, both in ’68, came to the conclusion separately from their own studies down there that the West Antarctic Ice Sheet had been a lot larger probably at the Last Glacial Maximum. Mercer coined the term “marine” ice sheets and cited the West Antarctic Ice Sheet as the best source for the six meter or higher sea level during the Eemian. That was in 1968, 1970. That’s the year I entered glaciology. The American Geographical Society map of Antarctica came out in 1970 and showed the concave profile of the West Antarctic Ice Sheet staring us in the face. It hadn’t been that obvious before, and I got my ISCAP bulletins started. So, a lot of things happened. Mikhail Grosswald (Russian), Wes Blake (Canadian) and Gunnar Hoppe and Valter Schytt (Swedes) published evidence for a former marine ice sheets in the Barents Sea north of Scandinavia, right about that time, 1968. That was a very productive year for glaciology in a lot of ways.

Denton:

I would say ’68 through the ’70s, I think most of this was put in place. And there’s a lot of details since, details on certain ice streams and how they were moving, and details of glacial geology up and down the Transantarctic Mountains and details of the seafloor. But the basic picture doesn’t change. In those days the basic picture was buttressing and ice shelves. That was argued about for a long time by glaciologists, many of whom poo-pooed for a long time until nature made a natural experiment. Nature exploded the ice shelves out on the east side of the Antarctic Peninsula, and guess what? The ice streams behind them sped up by five times. In Greenland, Jakobshavn went from flowing 8,000 meters a year to 12,000 meters a year once the ice shelf broke away, and Greenland Ice Sheet… all the glaciers sped up. So, that’s all back online again, the buttressing ice shelf effect. So, there’s been a lot of work done in West Antarctica since then, but I think the fundamental ideas were in place a long time ago. By the end of the 1970s they were there.

Thomas:

The things that are necessary to make the overall climate changes in the history of the Earth make sense. Right.

Denton:

Yeah, so that’s about it.

Thomas:

Okay. Could you tell me a little but about the program that you put together here at Orono? It’s been described as somewhat unusual.

Denton:

Oh, I didn’t put it together personally. It started when Imbrie enlisted me to help do the ice sheets, because he knew that I was a glacial geologist. Hal Borns and I enlisted Terry to move here to work with us, and then we found Jim Fastook here, and Bjorn Andersen was imported from Norway. Bjorn did the European work for CLIMAP. And we spent the better part of a decade. We were the first ones to reconstruct ice sheets globally that I’m aware of. Do you know anybody else, Terry?

Hughes:

No, not former ice sheets, no.

Denton:

It was a big jump.

Hughes:

Bill Budd, Dick Jensen, and Uwe Radok modeled the Antarctic Ice Sheet as it is today, but not in the past.

Denton:

Yeah, but we did it for the world. You’ve seen the book, The Last Great Ice Sheets, it’s all in there. We started the work in Antarctica at that time because the CLIMAP executive committee went down to speak to NSF people at Polar Programs to get us going in the fieldwork. I had done four years at that stage. I’ve done another 26 field seasons down there as a result of CLIMAP. So, we had the program going here. This climate group here has grown. It’s fairly large now, but nothing much to do with me. I started that part of it.

Thomas:

Well, that’s fine. I was just wondering, because everyone else who has mentioned the Maine program has said, “Oh yeah, and then there’s the Maine program.” You know, I spent some time in the Midwest back in August. I talked to Doug MacAyeal, for example, who was here for a little while and then went to Princeton, and he is saying that he had been working on this catastrophic model of climatic change and Imbrie said, oh, you should go talk to the people in Maine and study there. From here he went to Princeton and did a doctorate under Kirk Bryan, Jr.

Denton:

Well, he started his fieldwork on the Ross Ice Shelf from here.

Thomas:

Right. And he had been working under Bob Thomas who was here for a little while in the late 1970s. And so it seemed to be sort of a fairly unique program here.

Denton:

Yeah, I think the uniqueness here is the combination of glacial geology and glaciology. We talk to each other. As a geologist, I talk to Terry and he explains everything to me, and we come up with these ideas together, and then we say, well, gee, if it works in Antarctica, my God, it must work for Laurentide Ice Sheet, because no one had done it then either. And why couldn’t it have ice shelves? And then Grosswald came over from the Soviet Union. He joined us, too. So, we put that paper out in Nature in ’77—that’s a seminal paper, about how the whole thing works up north, and the instabilities in the Laurentide Ice Sheet, which are caused by the same instabilities that are now instrumental in forcing ice ages and forcing the termination of ice ages. All these surges out of the Hudson Strait into the North Atlantic, and in that particular case, they affect global ocean circulation, which affects CO2 in the atmosphere. So, all these things that go home to roost exist in the Laurentide Ice Sheet, but when we first started to apply them to the Laurentide Ice Sheet, we met a huge amount of resistance. The Last Great Ice Sheets, the reviews of it said we won’t have to worry about this book; no one will ever read this book. It’s selling for $500 bucks on eBay now. So, apparently it didn’t just disappear, and it’s 30 years old.

Thomas:

Yeah, Terry was mentioning that you had even a difficult time… well, that you had to make special arrangements to get it published, because you eventually had to go to the book format because—

Denton:

Right, because the International Glaciological Society wouldn’t publish it. And the reason they wouldn’t publish it is there was a great resistance to apply what to us was obvious, that the Antarctic Ice Sheet had ice streams, and ice shelves, and all these mechanics, then the Laurentide Ice Sheet might have had them. But the minute we suggested that the Laurentide Ice Sheet had them, we met with enormous resistance. I mean, someone called up Hal Borns here trying to get me fired, they were so upset with us applying the Antarctic model to the north. It just didn’t work. Well, it’s accepted without blinking an eyelash now. The fact that there were marine ice sheets, that they had ice streams, that there were ice shelves, that a lot of the stability was from the same mechanics that went on in Antarctica.

Hughes:

Will told me that the history of science is the history of obituaries—

Thomas:

Well, somebody once said that…

Hughes:

—got to get these people out of the way before you can have any progress.

Denton:

But that’s my perspective. I don’t work on it anymore. I work now on reconstructing climate history of New Zealand and South America. Although I worked in Greenland. I met a fellow, Gary Comer, who ran Lands’ End Corporation. He became a great friend, and he helped us a lot with money and logistics, and so we started working in Greenland. And we saw that in Greenland… you know, the abrupt climate changes in Greenland, from the Greenland ice core? We recognized immediately, by looking at the glacial geology alongside the ice cores in Greenland, that there was a great deal of seasonality involved there, that they were majorly winter events. What I’m working on is climate change, the Northern and Sothern Hemispheres together, alpine glaciation and the ice ages from a Southern Hemisphere perspective in New Zealand and South America. But again, I’m just following the footsteps of John Mercer. He worked there, too. Everywhere I went, he was there. He was a good friend, Mercer was.

Thomas:

I haven’t been able to find out all that much, I mean, there are the obituaries of Mercer…

Denton:

Oh, he was a great man. Terry knows. He and I were friends of Mercer. Mercer died quite a while ago now. Yeah, Mercer and I had a lot in common because we worked in the same areas: South America, Chilean Lake District, Lago Argentino, the New Zealand Southern Alps.

Thomas:

And he was primarily in your area of study?

Denton:

Yeah, in my area, so I spent a long time with him in Ohio at his house, talking to him about different things. So, even once down in the middle of the desert at 85 degrees south, working one day, I thought, well jeez, Mercer has never been here. Then I saw a little white thing sticking up from underneath a rock, and I flipped it over. It was a sample bag. It said J. M. on the sample bag. He was there.

Thomas:

“Mercer was here.”

Denton:

Yeah, and I was on Témpano Glacier three years ago with Charlie Porter, and Mercer had been up there in a Zodiac [boat] all the way from Puerto Edén. And I went to Bernardo Glacier, and Mercer had been there. I worked at Puerto Bandera moraines; Mercer worked on those. I worked at the Waiho Loop moraines in New Zealand; Mercer had worked on those. Just following in Mercer’s footsteps. Mercer was everywhere.

Hughes:

Transantarctic Mountains, Reedy Glacier and Beardmore Glacier… was there…

Denton:

Yep. He was a very gentle man, very nice man, a type of intelligence I would call the intuitive intelligence. He could jump over all the nitty-gritty details that would stop everybody else and see where the truth lies. I thought he could. And I remember he wore a big, huge Mickey Mouse t-shirt. He was devoted to his daughter, Jane, and to his wife, Judy. But Jane, the sun rose and set on her. And he operated in South America on nothing. It was cheap down there then. The taxis were cheap, so he never rented a car. He just went out of the hotel in the square at Castro, and he just would call in his favorite taxi driver, and pay him a few pesos, and they would go off for the day. That’s how he did it. So, I searched out that taxi driver when I was working down there, and he was still there. He remembered Mercer, that guy did.

Hughes:

When I was at Ohio State, he had slideshows from time to time and showed Fitzroy on one of those occasions. So, I thought I got to see that. So, one of the times when I came back from Antarctica, from Deception Island in fact, I plopped down at the British Club in Rio Gallegos and knew Mercer would show up sooner or later, and he did. He had an old Jeep that needed a set of tires. I said, “John, I’ll buy you a set of tires for your Jeep if you drop me off to spend two or three days in Fitz Roy.” So, he did. He also drove me all around where he’d been working, so I got a first-hand view of the way he was putting all those things together back then as well as getting to Fitz Roy. [ed. For further recollections by Hughes of Mercer, see the obituary he wrote in 1988 for the Journal of Glaciology, https://doi.org/10.3189/S0022143000009163]

Denton:

Why the history of the West Antarctic Ice Sheet, don’t forget who started it—this guy and Mercer. Not all these people who are talking to you now. They are Johnny-Come-Latelys.

Hughes:

Well, Mercer’s office was right next door to mine at Ohio State, you know.

Thomas:

And I spoke to Hans Weertman as well, so.

Denton:

Well, what’d he say? Same thing? Hans is right there, too. His 1974 marine ice sheet paper, if you look at papers. Terry was there in ’73, Hans in ’74, Mercer in ’68. I was reconstructing ice sheets in ’68, ’69. The story was pretty well set at that stage. And now there are teams… It’s not that the work going on right now is not important. There are a lot of details. But I don’t think the basic story has changed one iota since then. Do you think so, Terry?

Hughes:

No. Now, that was a very productive year, ’68.

Denton:

What happens is, if there is a seminal idea like this, NSF has got to investigate it. They cannot be a position where they are working in Antarctica and the ice sheet collapses from under their feet. And so all the glaciologists… that’s been the major glaciological program in the United States for 25 years. And I still think that it’s the same exact… I could go back now and I’d hear the same things I heard in the ’70s.

Thomas:

Now, Mercer has another kind of seminal paper, and that’s his ’78 one that links it to CO2, and then two years later there’s actually the first Department of Energy conference here. And I’ve been trying to figure out exactly—

Denton:

Is that the one that Uwe Radok was at?

Hughes:

Yeah.

Denton:

Oh my God.

Hughes:

I got the transcript of all the talks right in the drawer over there.

Thomas:

Yeah, yeah, I keep hearing about this transcript, and one of my colleagues actually has a copy of it in San Diego.

Denton:

That was a seminal meeting. It was held right here. I was at that meeting. That meeting was a classic.

Thomas:

Yes, can you tell me anything about it? Either of you, really.

Denton:

Well, I stood up at that meeting and I gave what I thought was exciting… We’d been all over the place doing work: the trim line work at Ellsworth Mountains, the glaciers. This was all exciting at the time. This took a lot of work. So, I get up and gave it—

Hughes:

Discover the algae layers in the Dry Valleys, and got the dates for—

Denton:

The algae layers for dating; how to date the algae. This doesn’t come easily, you know? All over this big continent. It took a lot of work. And I get up, and I give some of it. Uwe Radok heard my story and says, “What’s glacial geology? Just 101 insignificant little moraines with 1001 explanations.” [laughs] And that was that.

Hughes:

He dismissed it with a wave of the hand. George spoke too fast for the stenographer to follow, so George’s presentation and Uwe’s wisecrack probably aren’t in the transcript.

Denton:

That’s what I remember from that meeting. Charles Swithinbank liked the whole thing. He caught on right away, Charles did.

Hughes:

Radok gave a talk, and Swithinbank gave a talk. And Swithinbank talked about ice rumples on ice shelves. Ice rumples. Surface ice rumples are caused by pinning points under an ice shelf where the ice is able to scrape over the pinning point, as opposed to having it stick up into the ice and make ice flow around it. That produces an ice rise on the surface. I thought Radok was originally Latvian, but I’ve heard since then that he was Hungarian, so I don’t know for sure. But anyway, he had this Eastern European accent. And at the end of Swithinbank’s talk where he had mentioned ice rumples, Radok asked… Swithinbank was one of these Englishmen from Cambridge who had this sort of upper-class persona about him. His father was in the Burmese Foreign Service—

Denton:

That book has a lot about Mercer in it. That’s a great book. That will illustrate the whole history of climate change. Have you heard about that one? It just came out.

Thomas:

Yeah, actually my boss is Spencer Weart. He’s also done a book on the history of climate change and I think he has this on his shelf.

Denton:

I don’t know who he his. This is our publication from the year 2000. The summary… And these 101 marines with 1001 explanations, they have one explanation. That’s from the algae dates in the Dry Valleys and from Beardmore Glacier.

Thomas:

Figure 10-C, page 155. Okay.

Denton:

That’s it at Hatherton Glacier. That’s it at the head of Beardmore right beside the East Antarctic Ice Sheet. That’s it at Mackay Glacier. That’s it in the Dry Valleys. That’s it right there along the foothills. That’s the 101 moraines with 1001 explanations. But that’s what I remember from that meeting.

Hughes:

When they’re mapped and dated, there’s only one explanation. Before, they were either mapped and undated, or if they were dated they were unmapped.

Denton:

This is our reconstructions there from Beardmore Glacier at the Ross Sea. That’s 30 years of work. So, that sets the scene for what that ice sheet has done in the past, and the recession of it in Holocene time back like that. And then McMurdo Sound, the reconstructions. And then in 2002 we had the reconstruction, not just of the Ross embayment, but of the whole ice sheet.

Hughes:

At the end of Swithinbank’s talk at this meeting up here, Radok was in the audience, and Swithinbank was talking about ice shelves, and Radok says, “Vas iss dis vord rrrrrumples? I don’t know dis vord rrrrrrrumples!” Swithinbank replies, “It’s a perfectly legitimate English word. You’ll find it in any comprehensive English dictionary.” That was all he said about it. Swithinbank, you know, he was a Cambridge graduate. His father was in the British Foreign Service in Burma. He was actually born in Burma. So, he had this persona, you know, of someone who could move in those circles and not be perturbed by the rabble, like Radok running away from Hitler. [ed., Radok’s family had emigrated to Australia in 1938 to escape Nazi persecution.]

Denton:

It’s too bad Mercer wasn’t alive, because you would have done him. But in Fixing Climate, there’s almost a chapter on Mercer. Who’s your person that wrote a book on it?

Thomas:

Spencer Weart. It’s called The Discovery of Global Warming.

Hughes:

I’ve got to go to my glaciology class. It goes from 2:30 to 4:30 on Wednesdays. I didn’t start it until early October because one of the students who wanted to take it was on a ship in the Gulf of Alaska, and so I postponed getting started until he came back.

Thomas:

Should I wait around for you or are we done?

Hughes:

Available until the late afternoon.

[Hughes departs]

Denton:

This guy’s a genius, you know. He’s got an IQ of 180.

Thomas:

He reminds me of… if you’ve ever read the work of some of the 18th century natural philosophers, like William Herschel.

Denton:

What’s strange to me is that this guy originated… You probably saw the ISCAP bulletins he put out.

Thomas:

Oh yeah, yeah, yeah. No, that’s why I’m up here.

Denton:

He and Weertman and Mercer, none of them have benefited from it. I don’t think he’s gotten a grant to work on it. It’s a whole team of glaciologists working down there and making a living on all of this for 20 or 30 years. He just kind of got left in the lurch. But he originated it. And that’s still the big idea of glaciology, and the big idea after that about the buttressing, and the ice shelves, the ice streams. Just look at his papers from the ’70s. It’s right there. Everything else has been great work, but it’s not been the big breakthrough. That was a big breakthrough was in the ’60s and ’70s.

Thomas:

Could you tell me a little bit about how that conference that was here that we were just talking about kind of came together?

Denton:

No, I can’t remember much about it. I remember there was a big effort put into it. It was 30 years ago. And this was all just breaking news at the time, and a lot of people came. All the major figures were here at the time. I remember exactly where it was. It was on the side of the campus here, and I remember giving the papers, and I remember there was a lot of arguments about it in those days. It wasn’t fully accepted. He remembers all these details.

Thomas:

Yeah, it was the first of many conferences. There was one at Berkley Springs, West Virginia in 1982. I don’t suppose you wouldn’t have had much to do with these. And then in San Diego and Seattle as well.

Denton:

Yeah, I’m more of a geologist, so I go to geological conferences. I’m interested to know more than just the West Antarctic Ice Sheet. Mercer was interested in the same things I was. If you read this book, Fixing Climate, I’m in that book. That’s what I’m interested in more than… Although I shouldn’t say that. I spent 30 years putting together the history of the West Antarctic Ice Sheet, 30 field seasons. I don’t go to the WAIS meetings or anything like that. I’ve heard it before, most of it. And then we had Doug MacAyeal here at that time. He’s a very intelligent person. He had a lot of ideas. And we’ve had a lot of students working on the history of Antarctica. In fact, I mean there’s Brenda Hall here who’s taking over for me, working in the Transantarctic Mountains. They’re leaving in about two weeks to go to Scott Glacier, mapping and dating those same “insignificant” moraines, going down and getting more details on the dating and the chronology, because a new method of chronology has come out called exposure-age dating that allows the actual history of lowering ice levels near the Siple Coast to be mapped and dated from the beryllium-10 content of rocks in moraines alongside Brenda’s outlet glaciers.

Thomas:

Yeah, Terry mentioned you could tell me about that.

Denton:

But right now, most of our students, we’re working Alpine glaciation north and south, and this whole theory on abrupt climate change. That’s an interesting study though, how a few individuals started it many years ago.

Thomas:

Could you tell me a little bit about the papers that you and Terry did, especially in the 1980s?

Denton:

Yeah, we spent a long time writing The Last Great Ice Sheets, ’81. Our CLIMAP work was done by about 1977. It took four years of writing and editing before Wiley-Interscience published it in our book. Prior to that we put out papers in the ’70s.

Thomas:

Oh, let’s see here. Yeah, you had a paper on the Milankovitch theory of ice ages, and then global ice sheet systems interlocked by sea level, potential influence of floating ice shelves and the climate of an ice age. Maybe a couple more.

Denton:

Oh, I had papers in the late ’60s on the West Antarctic reconstruction, some in an un-refereed journal called Antarctic Journal of the United States that NSF put out. And back in ’71 we published quite a famous book, I’ll show it to you. [Denton leaves to find a book.] Well, here’s some of the earlier ones, references to them. I don’t keep track of them very well, but this is a book. It was ’91. Here’s one from ’79, “Glaciation of the Byrd-Darwin Glacier Area.” Here’s one, “The Antarctic Ice Sheet Influence.” Here’s one, ’68, “Glacial Geology and Chronology of McMurdo,” and that started it. There’s one here, The Last Great Ice Sheets, you’ve seen that. “Potential of Floating Ice Shelves.”

Thomas:

Yeah, these are the ones that I was kind of referring to.

Denton:

There’s one here, ’83, “Cenozoic History”. Here’s one that was pretty instrumental. This one published at Yale University Press 1971, The Late Cenozoic Glacial History of Antarctica, that had a West Antarctic reconstruction in it. That’s ’71, that’s what, 37 years ago. There’s a whole bunch of them here. 1986, “Interlocked by Sea Level.” Do you want to copy? You could Xerox this.

Thomas:

No, I think I have references to most of these.

Denton:

’68, you have it, too?

Thomas:

Yeah, I was just wondering what kind of project it was. I mean, obviously just reconstruction of the ice.

Denton:

Yeah, there’s ice surface fluctuations of Beardmore Glacier, geology of the Ellsworth Mountains, Antarctic ice mass. That was 1991. And then we have this one. It was a major effort, this one in 2000 we have here in Geografiska Annaler. This one was a major effort. It’s got another set of maps that goes with it. It’s got a map portfolio.

Thomas:

They aren’t tucked in here, are they?

Denton:

No, it’s a separate piece that goes with it. That gives all the background of the dating, and by that time we had lots of carbon dates and everything. Again, this work was nothing new. This in 2000 was known in ’71—nothing new.

Thomas:

One piece that I’ve been trying to fit into all of this was something Hans Weertman was working on theory-wise in the 1960s, and John Hollin was interested in, some of these ice age theories. At first, Ewing and Donn proposed an ice-free Arctic Ocean, and then came Alex Wilson’s ice-age theory. I was wondering, since that’s sort of your area.

Denton:

Yeah, I was there at the meeting in Quebec when Alex presented this. He published it in ’64 in the Canadian Journal of Earth Sciences. And so I know Alex well. I know him very well. Yeah, he basically gave that at a meeting in Quebec, and later at a conference in Trois-Rivières, a city southeast of Quebec City. And I was at the meeting. It was a meeting about surging glaciers. The Canadian Journal of Earth Sciences published the papers in ’69, but the meeting was earlier. Alex published his original theory in ’64 in Nature, and he just gave the paper there in front of the glaciologists. That was a very interesting meeting about surging glaciers. His idea was that the Antarctic Ice Sheet surged out to form an ice shelf, and solar heat reflected back into space from the high-albedo ice shelves caused ice ages. That was him. And it was also when Ewing and Donn gave their theory that evaporation from an ice-free Arctic Ocean provided snow precipitation that produced new ice sheets. At that stage, of course, Milankovitch wasn’t accepted. Milankovitch wasn’t really accepted as an ice-age pacemaker until Hayes, Imbrie, and Shackleton published their famous paper of ’76 in Science. That’s the seminal paper in our whole field, pacemaker of the ice ages. But before that, any theory went, including surging of the Antarctic Ice Sheet, or Ewing and Donn, and all these others. But they’ve all vanished. Weertman, the papers I remember by Hans, included that classic one in ’74 about the marine instability mechanism.

Thomas:

Right, the marine instability in response to Terry’s initial ISCAP bulletins.

Denton:

But Terry was his student, you see. Oh, Weertman is a genius. These two people, Terry and Weertman, are very special. Hans Weertman was at that meeting for the surging glaciers that Alex Wilson gave his paper.

Thomas:

Right, that’s the one where they had the special issue of the Canadian Journal of Earth Sciences.

Denton:

That’s right, Hans was there. I was just there listening, because I didn’t work in surging. I was working at that stage in mountains, which were full of surging glaciers, so I was interested in the subject, but I didn’t contribute anything to the meeting. I just listened to it. But it was a historical meeting. Weertman was there. I remember him clearly being there. [Gordon] Robin was there. [Kenneth] Hewitt was there; he’s now at Toronto presenting surging glaciers from the Karakoram. Austin Post and Mark Myer and Alex Wilson. Alex Wilson was surrounded by newspaper reporters because he was explaining ice ages, these new ideas of surging glaciers. Oh, he was the center of attention at that meeting. I don’t think that theory is ever mentioned these days.

Thomas:

No, not really. You kind of have to dig to find it. It’s sort of referenced in Terry’s papers, and it seems to have been the cause for a lot of the attention that was paid to the possible instability of the ice sheet.

Denton:

That’s right, it was.

Thomas:

But then it sort of disappeared after it took on a life of its own. And it’s not exactly clear to me how long it was sort of tied into the interest in the ice sheet. Let me put it this way, was there a period when it was taken seriously or wasn’t taken seriously?

Denton:

Yeah, I don’t know if it was even taken seriously then by the people who are associated with that. You don’t know Alex, do you?

Thomas:

No, I don’t.

Denton:

You ought to meet him. He’s out in Arizona. He runs nude dude ranches, I believe.

Thomas:

Oh, really? Interesting.

Denton:

Yeah. He’s a very smart guy. I know Alex well. I spent many days in the field with Alex. I don’t know if that was instrumental in Mercer’s thinking at the time or not. I don’t think a lot of people took it very seriously even at that time. John Hollin—

Thomas:

Right, well I know Hollin definitely did. Weertman at least wrote papers on it. I asked Hans about it, but he didn’t seem to have much memory of it.

Denton:

I remember Hans being there. Yeah, John Hollin was here for a while. Oh, he’s a wonderful guy. He’s a very innovative thinker. Yeah, he took that theory very seriously, looking into sea level rises associated with it. But it was John who came up… I forgot about John. He came up in ’61 with a classic paper in the Journal of Glaciology about controlling the Antarctic Ice Sheet via sea level. You know that paper?

Thomas:

Yes, yes. I’ve done a lot of research back into that period to find the origins of what I’m looking at.

Denton:

Well, you can go back even further than that. I knew Ned Ostenso, and I knew Charlie Bentley in those days. I first went to Antarctica in ’58. I went down on a plane with Paul Siple of the Siple Coast, and he was at the South Pole Station as well. Paul’s daughter lives right here in Orono, and his wife Ruth I knew very well. But Ned Ostenso was aboard that airplane, he and Ed Thiel. Ned and Ed worked with Charlie Bentley, and they were the first ones to discover the existence of marine ice sheets. That, I think, was published in ’61 as well, in the Journal of Glaciology. Ned, I think, has died since then. I saw Charlie this summer. We have an Antarctic meeting of the old folks from IGY back at Fort Clyde in July. It was fantastic. Charles Swithinbank was there and Charlie Bentley was there, and they discovered the existence of marine ice sheets to start with. You have to go back to the beginning. That’s the marine ice sheet of West Antarctica where those IGY traverses… and that work was published, if you look back in the Journal of Glaciology, I think in 1961 it was published, approximately then. And Hollin’s paper was about 1961 as well, John’s paper. John is very smart guy. That was a seminal paper, and I would say that Ostenso and Bentley wrote a seminal paper. And Alex’s paper in ’64 was interesting as a fad at the time, I think is what it boiled down to. Weertman’s paper, in my opinion, of ’74 is seminal. All of Weertman’s work is seminal—I mean, this guy is really something. This guy here, too.

Thomas:

Very innovative people, when you look at the fact that there was nothing beforehand. They essentially create the concepts.

Denton:

All knowledge is obvious once you know it. They didn’t know it then. We didn’t know anything about the glacial history of Antarctica either, nothing. So, yeah, I started there in ’58. I was 18 years old.

Thomas:

Why don’t we, as long we have just a few minutes, could you tell me, you know, kind of how you got started in that?

Denton:

Yeah, I went to Tufts University. I’m from Boston. You might tell by the way I talk. Tufts had an orientation week before classes started. I was only 17 then when I entered Tufts. What they did was to have professors in different departments give lectures for students. So, I went around and listened to all these lectures, and they were pretty good. And I went to one in geology given by a man named Bob Nichols, and Nichols worked in Antarctica. He worked in the Finn Ronne expedition of ’47. I went to Tufts in ’57-‘58, and Bob had just come back from Antarctica from working in Marble Point for Metcalfe and [Andy Angenierson? Not a name?]. He gave a talk about it, and I became interested, so I took geology. And I liked it a lot, and I got to know Bob, and so when I was sophomore, I was then 18 at Tufts, he took me to Antarctica as his field assistant. Then he took me again in 1960 as his field assistant. That was my first two trips to Antarctica. I liked it a lot. I learned a lot, and those were the early days.

Thomas:

You went to the South Pole Station you said?

Denton:

No, no. I went to Antarctica. I worked in the Dry Valleys and Marble Point. No, not South Pole, no. Paul Siple went there. He was going to winter over at the South Pole. But I never went. I’ve been, but I never went that time. And so I worked as a field assistant for a couple of years. Then I started working on St. Elias Mountains for my Ph.D. at Yale. I went to Yale after that and worked with Richard Foster Flint, who was the great Quaternist of the day. And Link Washburn, who was head of the Polar Research Board for a long time. And I worked on St. Elias Mountain, and when I finished that I went to the University of Stockholm on a postdoc. Well, I lost interest in Antarctica. I went back there a couple times in the late ’60s. Well, I wanted to do the reconstruction of the ice sheet. That’s when we published the paper in ’68, ’69, ’71, and The Cenozoic Ice Age published by Yale University Press. Dick Armstrong, Minze Stuiver, and I published that paper. I didn’t know Terry at the time. I only knew Terry when his ’73 paper came out.

Thomas:

Did you get the ISCAP bulletins or was it the papers?

Denton:

Yes, I got the ISCAP bulletins. They were very important. They came out of Ohio State. Yes, I got the ISCAP bulletins that he circulated in the ’70s. He called himself the “Father of ISCAP.” That’s how he signed his name: Terence Joseph Hughes, Father of ISCAP. He was. He was! This guy thought it all up. He and his buddy Mercer sitting right beside him there. Then, after those Antarctic seasons I came here in ’69. I told you, I met Imbrie in ’69, then we started CLIMAP. I had recognized Terry’s genius, and we need this guy. We need innovative thinking. So, we hired him, and we’ve had innovative thinking ever since. And you saw at noon down there today at the lecture. So, he and I worked closely together ever since on a whole series of papers. We worked on CLIMAP, and that was a huge struggle. And we put The Last Great Ice Sheets out. There’s a lot of Antarctic stuff in there, and the application of Antarctic stuff to the northern hemisphere ice sheets. And what did I do after that? Oh, I decided that if we were going to do it right, then all right, let’s do it right. So, I worked for 30 seasons getting it what I think is right, all the way from the Antarctic Peninsula to northern Victoria Land. And all my students worked there, too, PhDs, and they’re there now in various places. Brenda Hall is upstairs. Dave Marchant is at Boston University. The last one just took a job at Dartmouth. They’re everywhere now working on these projects. Then we kind of set Antarctica aside for all the good stuff in glacial geology elsewhere. I started working in South America and then New Zealand. That’s where I work now. And then Gary Comer came along, and I worked three summers in Greenland with him.

Thomas:

Well, I think that should about cover it. I asked Terry about the weak underbelly argument. You mentioned it a little bit in your initial kind of run through of it. He said that you were looking at the map that was put out in 1970 by the American Geographical Society, and that basically just said, well, this is the thing that we need to—

Denton:

Oh, yeah Terry and I thought of that idea together. At that stage, I wasn’t too happy with how things were going—not with Terry, with other things. And so, I didn’t want anything more to do with Antarctica for a while. There were some personalities involved that I didn’t like. Some of our ideas appeared under other people’s names, and so he went ahead and published it, but we thought of it together, that weak underbelly. He’s got a famous picture of the… I won’t tell you about the picture, but in his way of doing things, that’s where the ice sheet evacuated. I’m sure it’s Pine Island Bay. And we knew a little bit of that in The Last Great Ice Sheets. He published that, then he went ahead and wrote a letter to the editor about that, because someone else had taken the idea and was publishing that, so he wrote that letter. I didn’t like what was going on, so I just refrained from joining in on the whole thing. We thought of that when we were doing The Last Great Ice Sheets, the weak underbelly of the Antarctica Ice Sheet. Now it’s big stuff.

Thomas:

Yeah, I was just reading a review by Vaughan the other day.

Denton:

What’s it say?

Thomas:

It said that the paradigm has been revived for the disintegration of the West Antarctic Ice Sheet, and it’s been through the Pine Island Bay.

Denton:

Yeah, guess where that came from?

Thomas:

Yeah, well exactly.

Denton:

He wrote it, but he and I made it up in this CLIMAP thing because of various circumstances of other people, saw it was a good idea, and started to publish it. I got so disgusted with that that I just told him—I guess I should have published it with him, because we thought of it together. I think he’ll tell you the same thing.

Thomas:

Yeah, he mentioned that. That’s why I asked you.

Denton:

Yeah, we have a picture of ourselves in front of Pine Island Bay. I don’t know where that picture went, but that was back in, I’m going to say that was in ’76, something like that, ’75 we thought of it. Years before. Now it’s hot stuff. Yeah, he and I thought of it. It was obvious. Anyone could think of it. Yeah, he probably told you the same story I just told you.

Thomas:

About that, yes. I didn’t hear about the picture though. That’s interesting.

Denton:

Yeah, he thinks that’s where the ice sheet had diarrhea, you see. That’s how he puts things out. So, he and I were in the picture, but I’m ashamed of the picture now because of that. It was a lot of work to do that stuff, write that book. Pine Island Bay is in that book, buried in there. And now it turns out to be a seminal idea, doesn’t it? They’re spending millions on it. NSF, I’m sure, are the people working on it don’t know where it came from. It came from right here, him and me. But he wrote the letter to the editor, and he asked me, let’s do it together. And I was just tired. I didn’t like what was going on. There were a lot of innovative ideas at that stage, and then we put a paper out, just the paper in 1977 in Nature, which set up how the northern ice sheets work by Hughes, Denton, and Grosswald, 1977, in Nature magazine, applying the Antarctic dynamics to the north and how the northern ice sheets become unstable.

Thomas:

Right, that’s all in The Last Great Ice Sheets as well of course.

Denton:

That’s there, too. But the first paper was Nature ’77. Unfortunately, we used the name “Wurm.” Nobody uses that name anymore. Nobody even knows what it means. It means the Last Glacial Maximum. We got the ice shelves too big in that one, but other than that I think it still works perfectly well. It explains why the Greenland Ice Sheet is left today and all the others are gone. For example, it explains why the Laurentide Ice Sheet is gone. It explains how it went away. It explains the basic instabilities of the Laurentide Ice Sheet, which I think is what triggers the termination of the ice ages. And that all came from the work we were doing in Antarctica. It’s there. The ’70s were…

Thomas:

The period of innovation.

Denton:

There was Hughes. I was working glacial geology. Hughes was working his theory, Hans Weertman was working his theory John Mercer was working. Has anything changed since then? Now they’re back to Pine Island Bay. Now I wish I had put my name on the thing. I was mad then, though, for reasons that are personal, but I was. Not at him, but at somebody else. But it all set in motion a lot of careers, didn’t it? People have gotten millions studying the West Antarctic Ice Sheet. How much has Terry gotten? Zero. Mercer? Well, he got a little bit. I made a living out of it for a long time, but he didn’t.

Thomas:

Well, I think we’ve kind of bulleted through most of the pertinent things that I wanted to ask about.