Oral History Transcript — Dr. Charles Bentley
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Interview with Dr. Charles Bentley
Charles Bentley; August 6, 2008
ABSTRACT: This interview was conducted as part of a series documenting the history of scientific work on the West Antarctic Ice Sheet (WAIS). Charles Bentley has been a geophysicist at the University of Wisconsin since 1959. This interview discusses his entry to geophysics and graduate work at Columbia University under Maurice Ewing, and his inclusion by Frank Press in Antarctic traverses associated with the International Geophysical Year. He discusses his discovery with Ned Ostenso of the marine nature of WAIS during this field work, and then the building of the geophysics program at Wisconsin. There is detailed information about the organization and work of the Ross Ice Shelf Geophysical and Glaciological Survey, and the Siple Coast Project, and his group's subsequent field work. He also discusses his interest in the subject of the prospective disintegration of WAIS, and his shift in interest from geophysics to glaciology on account of this problem.
TranscriptSession I | Session II
Thomas:This is Will Thomas on August 6, 2008. Iím in Charlie Bentleyís office at the University of Wisconsin at Madison and weíre going to be doing an oral history interview focusing on the West Antarctic Ice Sheet, the science and scientific assessments of it, but weíll also be trying to do a broader career overview. So, I guess why we donít start with a little personal background. Oftentimes itís traditional in these interviews for people to talk about who their family members were, if they came from a scientific family or not, how they got interested in science. And then, we kind of move into education and beyond, if need of it.
Bentley:Well, I grew up in Rochester, New York, and I come from a family of lawyers, primarily. I had two, an older brother and an older sister, and a younger sister, none of whom are/were scientists. My older sister is not living anymore. My parents are dead. But I was always interested in science and I was interested in high school. I went off for a year of prep school before going to Yale where I did my undergraduate work as a Physics major. And my senior year I didnít really know what I wanted to do.
Thomas:This is at college or high school?
Bentley:This is senior year at Yale.
Bentley:Yeah. I didnít really know what I wanted to do so I took a set of vocational aptitude tests and they said physics — that my strengths were in physics — plus outdoor work. And, the tester looked it up in a little book he had, and he found that physics plus outdoor work equals geophysics, which neither of us at that time in 1950 had heard of before. It wasnít a well-known science back then. So, I took this seriously and I managed to get a summer job, through a family connection actually, to somebody who knew somebody who knew Maurice Ewing at Columbia University who was a famous oceanographer. And I applied to him to see if I could get a summer job. And, at first he said, no, they were full up, but then in June I got a message saying, ďSomething has opened up. Can you come right now?Ē So, I went off and spent a summer out on the Atlantic Ocean with the oceanography research at Columbia. And I decided that that was really what I wanted to do. And Ewing was happy enough with the work that I did, so he got me into graduate school at Columbia. So, I went to Columbia as a graduate student in geophysics. And, after Iíd been there, I was doing marine geophysics, along about 1952 or Ď53, when the planning was being done for the International Geophysical Year expedition to Antarctica. One of the organizers of that program, who was responsible for finding people to go on the geophysical exploration part of the IGY, was Frank Press, who had an office right across the hall. He was an assistant professor, I think, at Columbia at the time. So, he walked across the hall where a bunch of graduate students, including me, were, and said, ďWould anybody like to go to the Antarctic?Ē And, I thought that sounded like a pretty good deal. I didnít have a thesis project. Although, once again I wasnít sure what I was going to do. So, I volunteered and then as a result of that I went to Greenland for two summers and sort of learned how to do seismic work on an ice sheet, by doing it because there wasnít anybody to teach me. So, that turned into my Ph.D. thesis, and then I was given special dispensation to stay — after the other people headed south to the Antarctic, left from Davisville, Rhode Island by ship. But I was given extra time so I could defend my thesis. I defended my thesis and left the next day for Panama to pick up the ship on the way to the Antarctic. So, Iíve been doing Antarctic research ever since.
Thomas:So, at Columbia, was the geophysics kind of part of the rest of the physics program or was it more closely attached to geology?
Bentley:It was part of geology. Ewing was a geology professor. We took physics courses. I mean, it was a strongly physics-based geophysics program, but we were in the Geology Department.
Thomas:And you did your thesis under Ewing?
Thomas:Okay. How big was the geophysics program there at that time? How many students, for example?
Bentley:Well, there were probably a dozen students, maybe. And there were three or four faculty members: Ewing, and Press, and Joe Worzel, and Jack Nafe, by the time I left. N-A-F-E. He was actually from the physics department. But it was a rapidly-growing organization. So, I say a dozen students, maybe, when I started out, but I have a very poor recollection for that kind of thing.
Thomas:Okay. So, what was kind of the objective of some of the science that you were doing on the ice sheet of Greenland, especially in the period before the IGY?
Bentley:Well, I was studying the structure of the ice sheet from a standpoint of how the wave velocity varies with depth in the ice, because thatís related to the physical properties of the ice. And then I was also doing ice thickness soundings, which was particularly aimed at [Ö] an important part of what Iíd be doing in the Antarctic, just measuring the ice thickness from seismic reflection sounding.
Thomas:So, it was sort of ďmappingĒ sort of activity then at that time?
Bentley:Not really in Greenland. They did lots of refraction profiles of various lengths, and reflection shooting. But, we didnít have any transportation other than local. We had a couple of Weasels that we were allowed to use at night. Of course, it was still light out. But, when the people from the Snow Ice and Permafrost Research Establishment were not using their vehicles, or the Army people who ran the station, then we could get access to the vehicles and so we could go out, and weíd have transport locally but we couldnít go any distance away. So, we werenít doing any mapping.
Thomas:Okay. So, I see by the CV that you sent me that you finished up then in 1959?
Bentley:Well, I actually finished in 1956 but I forgot to give them $50 to cover the deposit on my thesis. So, they didnít get my $50 until I got back in 1959, and so I got my degree in 1959.
Thomas:I see. I see.
Bentley:Formally. But it was, it was all done. It was just an oversight.
Thomas:So, when you defended then, that was when you went to the Antarctic?
Bentley:Yeah. Right after that.
Thomas:Right after that?
Thomas:Okay, so why donít we talk about that then a little bit. So, you were there for quite some time, correct?
Bentley:The first time I was there for twenty-five months.
Thomas:Right. So, was that, at that time an unusual amount of time?
Bentley:It wasnít. Well it was for the IGY. I mean, other national expeditions, particularly in those days, routinely sent people down for a couple of years. And one year, it was necessary to do any field work, because in those days you could only go in by ship, and you could only get in by ship at the end of the summer season when the sea ice had retreated. So, in order to get a full summerís field season in you had to go in the end of the field season before and spend the winter first, and then do the field season, and then come home or not. What happened was that I only was expecting to go for one year. But, I got so interested in what we were finding, which was how deep the West Antarctic ice sheet is, how far down the bed is, that I — believing that the IGY was a one-shot deal, that it was going to be over in another year, and I wasnít through finding out what I wanted to find out — so I re-upped, because I wanted to complete the survey of the area around Byrd Station in Central West Antarctica. So, I stayed for another year, thinking that was my only chance. And then, of course, by the time I got done, the SCAR, the Antarctic investigator countries, had all decided they were going to continue their work, and have been continuing it ever since. So, in a sense, I didnít have to stay another year at all. But, I never was sorry because it was a worthwhile experience, because I learned a lot, and because as long as I was there, why not? I had no connections at home. Well, I mean, I have my original family, so to speak, but no wives or girlfriends or anything like that.
Thomas:Right. So, just out for the Antarctic?
Bentley:Yeah. So, it worked out very well. I was ready to come home by the time the second year was over, though. Iíll have to admit that.
Thomas:I imagine the cold would get monotonous after a while?
Bentley:The whole business got monotonous. One of the things I did, when I got back to the United States, I went to New York to get my degree problems solved, and one of the first things I did was make a point of getting on the subway at rush hour. Because I had seen so few people for over two years that I wanted to — I just enjoyed the crush, which I remembered. I mean, I had been on it before. I never really appreciated the New York subway at rush hour back when I was living in New York, when I was at Columbia. But, after two years in the Antarctic I had a different feeling about it.
Thomas:Could you tell me a little bit about the group that you were with down there?
Bentley:At Byrd Station, well to begin with when we had a traverse party with our Sno-Cat vehicles running from Little America Station to Byrd Station, and at the end of our first summer, the summer we went down. So, that was in February of 1957, the end of the Ď56-í57 field season. The trail out to Byrd Station had only just been finished a few weeks before and they were just starting to put up the station, because they had a lot of trouble getting through the crevasse zone, the boundary between the Ross Ice Shelf and inland ice. But we had a marked trail, so we drove — there were five of us — we drove our vehicles out from Little America to Byrd as that was a way to get the vehicles there and also to do some work along the way. So, we were doing seismic sounding and other geophysical and glaciological work along the way. And, that was when we first discovered that the bed of West Antarctica was so far below sea level. Up until then we had expected that since there were mountains to the north of the route from Little America to Byrd, and there are mountains to the south that there were probably mountains covered by the ice in Central West Antarctica also. So, we were quite surprised when we found that the bed was — we thought after we left the ice shelf where itís floating, of course the bed was well below sea level there, it has to be, but we thought when we got to the grounded ice that the bed would come up underneath. But instead, it went down. And, at first I wasnít even sure that I was making measurements right. But finally, it got to a point where the reflections were deep enough and good enough that I actually got a double reflection, one that went down and back twice, without anything in between. So now, what I was afraid of was what I was actually measuring was a double reflection and I wasnít able to see the first reflection, that if that had been true then, when I got the double, if the first one had been a real double then I would have had to get a triple before I could get the quadruple. If you see what I mean?
Thomas:I think so.
Bentley:Iím not making that very clear.
Thomas:Want to use the back of this sheet of paper?
Bentley:Here, Iíll [Bentley is drawing slanted lines, representing a signal, bouncing between two parallel lines, representing the ice surface and the bed. A single reflection is a signal that bounces off the bed and is measured again at the surface. A double reflection bounces off the bed, the surface, and the bed again, giving a measurement at the surface of apparently twice the depth of a single measurement if one misses the first echo. The pattern continues for triple and quadruple reflections]Öthereís this, hereís the surface and hereís the bed [drawing the single reflection], and this is what I thought it was. So, I thought I was getting this. Thatís what it appeared to be. But this bed was so deep that I didnít really believe it. So, what I thought what I might be getting was this one. [A double reflection off a shallower bed]
Thomas:Right. Went down off the top and then down off the bottom again.
Bentley:Okay. Now, but then when I got the one that did this [a double reflection], and there was no sign of one that had gone down and back. See, if the bed was really here [shallow] then youíd have to get all three of these [reflections], and this would be the fourth one. Now, this one [the first echo of a quadruple reflection] we wouldnít see because it was too noisy here. There was still noise on the seismogram so you couldnít see an echo. So, thatís why I couldnít tell from recording this I didnít know whether it was this one, or this one. Because there was good reason why I wouldnít see the first reflection if it were this shallow. But then, when I didnít see the triple reflection if it had been shallow — it would have been the triple reflection. When I saw nothing here, but I did see this one [the second reflection, or what would have been the fourth reflection of a quadruple reflection], which was even later and traveled even farther, then I knew that Ö
Thomas:So, youíd seen the double instead of what would have been a quadruple?
Bentley:Yeah, right. But, I couldnít see the quadruple without the triple.
Bentley:So, when I didnít see the triple I knew it wasnít a quadruple and, in fact, it was just a double.
Bentley:Okay? So, it was in the course of that February drive out to Byrd that we discovered that the West Antarctic ice sheet had a bed way below sea level, which is why itís been in the news, not quite ever since, but why youíre interested in it, in essence, because (Thomas: Because itís a marine ice sheet?) of potential instability.
Thomas:Yeah. Did you have a sense that the entirety of West Antarctica then was — or not the entirety, obviously, but that large chunk of it?
Bentley:Well, it just kept going down. Byrd Station is quite a long way inland. And, it just kept going down as we went into Byrd Station, and then, of course, I was really anxious to see what happened when we went north and east. We went first towards Mount Takahe and then over towards the Sentinel Mountains, and then through the — you want a map?
Thomas:Yeah, I think thatíd be useful.
Bentley:[Crosses the room] I think Iíve got oneÖ this isnít a small size. Well, here. Itís not particularly small, but itís a good map. [Unfolding map] Letís see, Iím not sure which — well, itís, here the bedrock surface one weíre going to have to use.
Bentley:Well, this is [???].
Thomas:You know, I have your paper with Ned Ostenso here. It might Ö
Bentley:Oh, okay. Yeah. Letís look at the map there that [turning pages] where, the one, you already went by it.
Bentley:Yeah, here. Okay, so this is the route that I was talking about from Little America to Byrd, and from here all the way out to here we were seeing a bed way below sea level. And then we went out this way and it got even farther below sea level, up to 3,500 meters ice thickness over in here. And then when we came back over here, we hit the spot that, for a long time, was the lowest spot known under the ice sheet, on the way back. Then we knew that all of this, these are [inaudible], so this is the edge the Ellsworth Mountains, below the ice. So, we knew that this entire region was below sea level, and then I wondered whatís it like down this way, down towards the Horlicks? This was just a big blank, except for little mountains there, the Whitmore Mountains.
Thomas:Why donít we move back?
Bentley:Yeah. So, we found out then — [move back to microphone] oh yeah, we got away from your tape recorder.
Thomas:Thatís good. It might have caught it. But we were just talking, in case the recorder didnít get it, about the route, which is the one thatís on the second page of the paper with Ned Ostenso.
Bentley:Yeah. So, I was talking about first going from Little America to Byrd. Then we spent a winter at Byrd. Then we went out north and east from Byrd Station. And then, we spent another winter at Byrd and then we went south and east from, down towards the Horlick Mountains.
Thomas:How long would one of these circuits take?
Bentley:About three months.
Thomas:Three months? So, youíre just sort of camping out on the ice?
Bentley:Yeah. We slept in our Sno-Cats. In our first winter — well, let me go back a step because I got off the track of what you had originally asked me. So, there were five of us going out. Ned Ostenso was my assistant seismologist. There was Vern Anderson, the chief glaciologist, Mario Giovinetto was assistant, and Anthony Morency was the mechanic. And, so we drove out to Byrd, then Morency went home. Jack Long was then the mechanic, and he came in at the beginning of the summer. Wait a minute. Is that right? No, I canít remember when Jack Long — he was a mechanic on this traverse and I was pretty sure he was on this traverse too, but I donít remember his wintering over twice. So, Iím confused about that.
Thomas:Okay. Well, Iím sure we can straighten that out later.
Bentley:Yeah, that can be straightened out — but at any rate, the basic crews were two seismologists, two glaciologists, a mechanic, and then, when we went from Byrd then we had some people from the Byrd winter-over party who were interested in going along with us for a while. Dan Hale was one.
Thomas:What was Byrd Station like at that time?
Bentley:Byrd Station was those orange pre-fabricated buildings, which by the end of the winter were all completely snowed under, so that the snow surface around the Byrd Station area was even with the tops of the buildings. Because once the snow drifted up to the top of the building level then there was no obstruction to it anymore, and so it could just flow freely. And so then the rest of the ice sheet gradually built up to the height of the top of the buildings at Byrd, before it would start getting where the snow would start to accumulate on the top of the station again. So, by the end of the winter we were snug and cozy, completely isolated, and protected from the wind. So, there were half a dozen, maybe, of these prefab buildings and they served all our purposes. I mean, we slept in one. We had our science area in one, the same one for us.
Thomas:How many people wereÖ
Bentley:There were twenty-four people. There were twelve Navy and twelve civilian. And it was a joint command arrangement, which some people before IGY thought was a bad idea. So, there was one man who was in charge of the Navy people, an officer, and then there was a civilian who was in charge of the civilian people. George Toney. And, it worked very well actually. And, as an aside, the Navy doctor, who was in charge of the Navy contingent, named Brian Dalton, I just saw him at an Antarctic reunion just a couple of weeks ago, for the first time in fifty-one years.
Bentley:Yeah. First time I had seen him since he left Byrd Station. He left before I did. So, that was pretty neat.
Thomas:What had he been doing in the meantime, justÖ
Bentley:He had a full medical career. He stayed in the Navy for a while, but then he got out and did his own thing.
Bentley:So, then we had a regular routine of traveling a day and, and then doing station work for a day. So, we would travel twenty-four or thirty nautical miles one day and then the next day weíd do our seismic sounding and detail study of the wave velocities in the upper part of the ice sheet. And, the glaciologist would dig a pit to study the stratigraphy within the snow layers so they could determine what the snow accumulation rate was, primarily. That was a dayís work, and then the next day weíd travel again. And, while we were traveling we stopped every three miles for gravity measurements for the geophysicists, and for snow hardness measurements for the glaciologists. And then, we were doing altimetry also, aneroid altimetry. And, the way we got it, tried to get rid of weather effects, was by traveling three miles apart, so we were always reading two altimeters over a three-mile interval. Then weíd assume that the large-scale pressure changes were essentially the same at both ends of the three-mile line. So, the differences in what the altimeters read were the elevation differences between the two spots. So, then we got the absolute elevation just by adding differences, which is an inaccurate way of doing things. You know how errors can accumulate. But, it was the best we could do becauseÖ
Thomas:As a first approximation?
Bentley:Yeah. Because, I mean it was better than just having a single altimeter. Well then youíre measuring nothing but the weather.
Thomas:Mhmm. So, I see also here that this was for the Arctic Institute of North America. Whatís that?
Bentley:The Arctic Institute was just an organization that could pay the Antarctic traverse people. The National Science Foundation didnít hire people directly, so they had to have somebody toÖ
Thomas:As the administrative organization for the IGY?
Bentley:Well, Iím not sure whether it was for the whole IGY, but it was for this traverse program. There were several: there was this over- snow traversing, there was one at Byrd, there was one at Little America, there was one at Ellsworth Station over on the Filchner Ice Shelf. And, well, those are the three full-fledged traverse programs. Then they did a little bit of inland work at Wilkes Station, but they had an idea once [that] they would try and traverse the pole, but they didnít. They werenít set up to do that. It wasnít part of the plan. They didnít have the equipment. So.
Thomas:They didnít proceed?
Bentley:All they had was a lot of enthusiasm. [Laugh]
Thomas:Uh huh. Itís so close, why not?
Bentley:Yeah, well itís quite a ways from Wilkes Station to the pole. [Laugh] Wilkes is on the coast of East Antarctica.
Thomas:Right. But still, you know, closer than any of the other continents. I guess it could seem tempting?
Bentley:Yeah, itís close. Yeah, theyíre already in the Antarctic. Thatís right.
Thomas:Mhmm. So, is there anything else that we ought to discuss about that initial expedition or should we move forward to what comes next?
Bentley:No, I think that covers it pretty well. By the time we were done we had a pretty good picture. A good picture of what we knew at the end of IGY is a Science paper. Do you have that? Bentley, Crary, Ostenso, and Thiel?
Thomas:I might not have brought it with me.
Bentley:Published, I think, in 1960, in Science?
Thomas:I might know it by its Ö
Bentley:Well, the Bentley and Ostenso paper gives more detail about West Antarctica.
Thomas:Okay. Oh, here it is. ďStructure of West Antarctica,Ē 1960.
Bentley:Oh yeah, thatís right, Iím sorry, thatís West Antarctica too. But it includes what information we had about crustal structure as well as ice thickness.
Thomas:So, you put that out and then in 1961, ďGlacial and Subglacial Topography of West Antarctica?Ē
Bentley:Yeah. This one is a detailed report on our geophysical work on those two traverses. Well, no, on those three traverses, including the one from Little America to Byrd. The other one was a more summary and review paper that included work done by Ed Thiel in the Filchner Ice Shelf area, and Bert Crary, and theÖ
Thomas:So, it was more of an overview of everything (Bentley: Yeah.) that was done?
Bentley:Bert Crary and the Ross Ice Shelf area. Crary led the traverse on the Ross Ice Shelf, and Thiel had led the traverse on the Filchner Ice Shelf, to the — well, you know where the Filchner Ice Shelf is?
Thomas:Thatís the one on the other side?
Bentley:Thatís the one on the other side, yeah.
Thomas:That the peninsula kind of curls around, right? Like, yeah, here.
Bentley:Yeah, itís this one over here.
Thomas:Filchner and then Ronne.
Bentley:The Filchner actually, this is now the Ronne Ice Shelf. The Filchner Ice Shelf is, is just a little piece over here. At the timeÖ
Thomas:So, they changed the name?
Bentley:Well, they changed the name because the pre-IGY maps had an ice shelf that was just a strip along the coast here. This was known as Edith Ronne Land, after Finn Ronneís wife. But then, after the IGY work discovered that there wasnít any land there, it was all ice shelf. (Thomas: I see.) So, Edith Ronne Land disappeared. So, to make up for that they moved Filchnerís name down here to this part of the ice shelf and they put Ronne, and then they dropped the ďEdith,Ē because only Byrd had enough clout to keep his wifeís first name (Thomas: I see.) on one of the Ö
Thomas:Marie Byrd Land?
Bentley:Marie Byrd Land.
Bentley:Ronne, he had a lot of clout but he didnít have quite enough to keep Edith. So, the ice shelf became Ronne Ice Shelf, which is named after Edith Ronne, not after Finn Ronne.
Thomas:I see. So, I know they often hyphenated it. So, thatís just kind of the structure of the two of them?
Bentley:Yeah. Because glaciologically itís one ice shelf with a big island in the middle. It would be like over, over here in the Ross Ice Shelf. If Roosevelt Island were bigger, like this, then youíd name this one thing and call this part something else. But, itís really just one ice shelf. So, thatís why you so often see it Filchner-Ronne.
Thomas:I see. Okay. So, you came back?
Bentley:So now we can go on. So, yeah.
Thomas:Paid your fee?
Bentley:And came back, paid my fee. Then I was given a choice of going to the University of Wisconsin to work on my data, or giving up my two and a half years, or twenty-five months worth of data. SoÖ
Thomas:Was there any upside to the second choice?
Bentley:No. Not for me. That was a very easy decision to make. So, thatís how I got here. Because the professor here, George Woollard had the grant from the National Science Foundation for data analysis for the Antarctic Over-Snow Traverse Program. So, Thiel, and Ostenso, and Behrendt, all came here. Bert Crary didnít because he had a higher-level job in Washington with the National Science Foundation. He was not the chief Antarctic scientist, that was Harry Wexler, but he was the chief of the geophysical exploration program.
Thomas:Okay. So, then you came here?
Bentley:So, then we came here and worked on data, went back to the Antarctica in Ď60-í61, and then Ď62-í63, and developed the Antarctic research program here, and then I started teaching a course in seismology, theoretical seismology. And then, gradually, through the back door, I worked my way into the faculty. It was such a sneaky approach that [Ö] some years later I was trying to find out when I was actually appointed to the faculty, and the university didnít know. They had no record. Because I was trying to figure out how many years it had been since I was made an assistant professor. But they simply didnít have a record of it.
Thomas:So, here [on Bentleyís CV], when you say that youíre a project associate from 1959-61, and then assistant professor from 61-63?
Bentley:Well, I had to put something. I couldnít just put a question mark.
Thomas:So, thatís just sort of arbitrary?
Bentley:Well, Ď61 is pretty close. But, that was just largely by when I thought it happened. But the college deanís office didnít have any record. Things were pretty casual back in the Ď60s. Itís not like the way they do things now.
Thomas:Right. So, what was the program like here when you arrived?
Bentley:Well, there had already been a year of the data analysis program going on because the people who didnít spend the second winter, which was most of the traverse people, came here and were hard at work, working on their data. So, there was an active group here already. Thiel, and Ostenso, and Behrendt, and Hugh Bennett, who was with Crary on the Ross Ice Shelf, and Ed Robinson was also with Crary on the ice shelf. Steve den HartogÖ were all here working away when I got here.
Thomas:Okay. So, this is sort of, I guess, one of the post-IGY centers then ofÖ
Bentley:Yeah, there were two. There were two from the traverse operation. The geophysicists came here. Woollard had the grant for that, and then Dick Goldthwait at Ohio State had the grant for the surface glaciology, snow pit studies, etc., at Ohio State. So, Vern Anderson, and Bill Long, who were the two glaciologists on the Sentinel traverse, and others, went to Ohio State. So, they had their data analysis program there. Mario [Giovinetto] went there for a while, and then he came to Wisconsin to do a Ph.D. program in geography.
Bentley:Still as a glaciologist.
Thomas:The existing, I guess, glaciology — or not glaciology but, what would you call it, the department here, that you joined?
Bentley:Well, there was a Department of Geology, and at some point early on or maybe just before I got here, was named Geology and Geophysics. I donít remember just when that name changed. But, the only faculty member — well no, I take that back. There were two new assistant professors, Bob Meyer and John Rose, and Woollard was the full professor who was head of the program. They were all working on various aspects of gravity. That was theÖ
Bentley:That was big — gravity of the Earth.
Bentley:Not gravity waves. [Laugh] Not celestial gravity but Ö
Bentley:Woollard had a program for worldwide gravity measurements. So, that was a big deal. It was an important program. And Bob Meyer before long got into doing seismic studies of continental structure in the United States, and eventually elsewhere also, South America and Russia. Whereas John Rose was working primarily on absolute gravity. He worked with pendulum gravity measurements and then he worked for years trying to develop an absolute gravity device. And, then after a few years, Iíve forgotten the exact years, Woollard moved to Hawaii and John Rose went with him. Bob Meyer stayed here, as did I. And Ned Ostenso was then, for a little while, assistant professor here, before he went and joined the Office of Naval Research.
Thomas:Okay. So, this is really kind of the beginning of a polar program that youÖ
Bentley:That was the beginning of the polar program, yeah. Woollard had a grant, starting from before IGY, but he didnít really have any program because there wasnít any glaciology. There wasnít any science before the IGY. He just had the program. He bought one set of the seismic equipment that we had in the Antarctic. But the program really started when those first people came back at the end of the first IGY year.
Thomas:Okay. Was there a sense of — I mean just outside of getting the general bearings from all the data thatís brought back from IGY — a sort of programmatic sense of what geophysics or geology of the polar regions or Antarctica should be like?
Bentley:Um, Iím not sure.
Thomas:Were there any specific problems that stood out in your mind? One of the ones that crops up in the preliminary research that Iíve done is a lot of ice age studies and the role of — not necessarily the role — but just what the ice in Antarctica and the Arctic wasÖwhat role they —
Bentley:How long theyíve been there?
Thomas:Yeah, how long it had been there and any possible roles that it might have played in forcing interglacial periods or glacial periods.
Bentley:Yeah. No, we didnít have much concern of that. We were more narrowly focused on trying to determine what the ice sheet was what its characteristics were, how big it was. There were glacial geologists who were interested in the history of the ice sheet, but there was very little information in those early days from which you could draw much, if any, conclusions about history in the Antarctic ice sheet. (Thomas: Right, I see.) And most of us had physics backgrounds rather than geology backgrounds. So, we had less focus on the geological aspects in those days. We did — in that early paper, the Science paper, Bentley, Crary, Ostenso, and Thiel that I already mentioned — we do get a little idea of how we think the ice sheet formed, but thereís no timescale on it because we didnít have any sense of time scale.
Thomas:Again, a sort of preliminary sketch of what it was?
Bentley:Now, Ewing, the last thing Ewing said to me before I went off to the Antarctic, my major professor, he definitely had a sense of time. And he specifically instructed me, before I went, to keep an eye out for anything I could see that would give an idea of how long the ice sheet had been there. But I didnít find anything. And, I didnít have it at the front of my mind most of the time anyway.
Thomas:Right. I know, I guess more on the glaciological kind of things, and on the theoretical sides of things, this is sort of when things sort of — Iím not making much sense, but I guess on the physics of ice, you know, just talking to Hans Weertman the other day, (Bentley: Oh yeah.) what he and John Nye were doing, was that just totally off your radar at that time?
Bentley:No. No. The physics of ice was definitely of interest. And we were studying in detail the seismic wave velocity structure, which is related to the elastic properties of the ice. So, we were doing that kind of physics studies on the ice ourselves. And then we were interested in John Nyeís flow mechanics. We didnít have any direct information on that, but we looked, for example, at the relationship between surface slope and ice thickness, which came out of Nyeís theory, and to see how well that applied to Ė that came out of the fact that thereís a limited shear stress at the bed. So the shear stress is proportional to the product of the ice thickness and the surface slope. So, the thicker the ice the less the surface slope to keep the shear stress. And a simple theory was: it was a precise constant, the yield stress of ice on a plastic model. The ice is not really purely plastic. So, in fact, the shear stress can vary a bit, but it still tends to be very less than — I mean, a relatively small amplitude around an average value. So, that still means that thereís a tendency for the surface slope to be a reflection of the ice thickness. When you come across this, when you see the surface slope increasing, it probably means that thereís a high spot in the bed down below.
Thomas:Okay. How about, just in terms of, say, glacial mechanics. They were working on those sorts of things as well. Was that something that you would have been interested in, or was it more just sort of the Antarctic ice sheets?
Bentley:Yeah. I was interested in glacial mechanics. I mean, what I was just talking about, the surface slope, which is based on glacial mechanics.
Thomas:Related to that?
Bentley:Yeah. And, it wasnít anything we were working at actively, but yeah we were certainly interested in what they were finding, and read their papers and stuff.
Thomas:You, yourself, never did any work with mountain glaciers or anything like that?
Bentley:No. Never done any work on a mountain glacier. Only Greenland, Antarctica, and a couple of ice caps in the Canadian Arctic.
Thomas:Okay. I know, there are a couple of papers, at least, I know Weertman in particular. I canít think if Nye entered into it, or Glen, or any of those people about — there were papers in the early 1960s, particularly about the stability of ice sheets and ice caps. And, actually, some of those were related to the Ewing and Donn Theory of Ice Ages.
Thomas:I was wondering if you had any comments on those sorts of things, as sort of an extension of your interest in the physics of ice?
Bentley:No. IÖ no.
Thomas:No? Okay. Then I think Iíll let you take the lead again as we go through the 1960s, just to try and get at what was of most concern to you as you were digging in here at Wisconsin?
Bentley:Okay. What we were — our primary concern, besides the ice thickness, which was always a focus, I mean for quite a few years, we were interested in the crustal structure. We did quite a lot of, I mean, both for the gravity, and we did seismic refraction measurements with shot-detector spacing large enough so we could actually see the arrivals that had passed through. You know seismic refraction?
Thomas:Just general principles.
Bentley:So, in seismic refraction, this travels down at a critical angle [drawing] and then the wave travels along horizontally, I mean just below the bed. Thatís called a ďhead wave.Ē And then it comes back up over here someplace. And if you get out far enough, since this wave down here is traveling in the Earth is traveling faster than the wave in the ice this actually starts to come in first, and then you can get a part of it. Then you, if you get a series of these then the slope of the time distance curves gives you the wave speed down here.
Thomas:Oh, okay. Are these easily distinguished from, say, something more likeÖ
Bentley:Yeah. The reflections look very different. They come in at a different time. They have, what youíre after —
Thomas:Than the ones that just bounce?
Bentley:Yeah. For a long refraction youíre trying to get this refracted arrival to come in first before anything else does. And, these [Ö] you get waves that come through the ice. This is the way we study the part of the ice, as a velocity gradient which bends all the rays upwards. So, you get a whole bunch of different arrivals that go through the upper part of the ice. But, if you get out far enough then, this arrival, thatís gone all the way down here and come back up again starts coming in first. And then you can plot the wave velocity in the layers under the ice.
Thomas:Sorry, Iím not quite sure I understand how — I mean, when you say it ďcomes in first,Ē I mean obviously it travels a much greater distance?
Bentley:Yeah, but the point is this part of it travels at higher speed.
Thomas:Much higher speed, because itís [inaudible]?
Bentley:Itís like driving on the interstate. If you go far enough, even though youíre driving fartherÖ
Thomas:Right. Well, just because the material is so much denser?
Bentley:YeahÖ [Bentley is uneasy with the statement. The following conversation is Bentley explaining to Thomas that, while it is true that wave velocity does in reality tend to increase with rock density, this is not because wave velocity is directly proportional to density based on physical principles.]
Thomas:Itís like a sound traveling faster through steel than through air?
Bentley:Because it has higher wave speed. Yeah. And, actually, the denser rocks tend to have a higher wave velocity, but, literally speaking, thereís an inverse relationship between wave speed and density. But the wave speedís proportional to the square root of some elastic moduli divided by the density. But, what happens in rocks is that the elastic moduli go up proportionally faster than the density goes up. So, in fact, as the density goes up, even though the density appears in the denominator of the expression for the speed, the speed goes up because of the elastic moduli, which you put in the numerator, increases even faster. So, [writing] weíll take this simple wave velocity for a shear wave. This is just the shear modulus divided by the density. Now, if you kept the shear modulus constant and increased the density, if you took a partial derivative with respect to the density, then it would be negative. But, because [???mu], the (shear modulus, or rigidity) increases more rapidly than the density from rock to rock, it means that the denser rocks have a higher wave speed because this is increased even faster. Itís likeÖ
Thomas:I see what youíre saying.
Bentley:Itís like suppose we say the ? was proportional to ? [rho] squared. Then even though ? is appearing in the denominator here, this is increasing faster. Thatís, this is nonphysical. [writing] Thatís just a mathematical example.
Thomas:Right. So, thereís no hidden [???] up in theÖ
Bentley:No, thereís no actual [???] there at all. But itís not necessarily so. I mean, there are some materials where the velocity would actually decrease with increase in density because ? doesnít get larger.
Thomas:Okay. Iím onboard with you.
Bentley:Okay. So then our primary interest, other than the ice thickness, was the glacier bed, the crustal structure underneath the ice, reflecting probably that several of us came from [an] exploration geophysics background. And before I went off to Greenland I was doing marine geophysics, doing seismic refraction work on the ocean. So, that was something that was a designed part of the program for the Antarctic right from the start. I mean, the other traverse people were doing it too. But, I always had a particular interest in that, and a lot of my publications have been on that aspect as well as the ice itself, although diminishing through time. Eventually I became more and more interested in the ice itself. At some point I stopped thinking of myself as a geophysicist and started thinking of myself as a glaciologist.
Thomas:Mhmm. If we were to kind of focus in on that point, I mean, what decade would that have been in? Would that have been in the 1960s period or would that have been later on?
Bentley:No. Probably later on. Seventies. In the Ď60s, I went back and did a traverse out to the Bellingshausen Sea from Byrd Station. That was an interesting traverse. That one showed us that there wasnít an open connection with the Byrd Basin — the deep ice all the way out to the Bellingshausen Sea — which we thought there was. Before that traverse, we thought there might have been. But then I did some specialized geophysical glaciological work on Roosevelt Island for a couple of years. I mean, I went one year, but our program was for a couple of years. And then we moved up to the South Polar plateau and in the mid Ď60s, from Ď64 to í69, we ran (one, twoÖ) three traverses, (with a year off) from South Pole to the Pole of Inaccessibility, to the U.S. Plateau Station, which is a high-elevation station farther northwest, and then out into the middle of Queen Maud Land where the vehicle — we had big new Sno-Cats for that program. I mean, they were new in 1960. They were abandoned because NSF did not support us for the last leg of our traverse, of our planned four seasons. The last leg was going to bring us back to the South Pole, so weíd have all [the] equipment back. But we werenít supported to do that. So they picked us up, but they left the vehicles out there. So, theyíre still there. And, in fact, thereís a Norwegian-American traverse program going, that went from the Coast of the South Pole last year and theyíre going to go back next year and theyíll be driving not far from where those Sno-Cats still reside, buried under the ice.
Thomas:Okay, so theyíre buried by this time I guess, yeah.
Bentley:Yean, and since we had only celestial navigation in the Ď60s, we donít really know exactly where those vehicles are. I mean, they probably have a position thatís good within like a kilometer or something like that but theyíre not going to show at the surface. So theyíd be kind of hard to find. Youíd have to do a detailed radar survey or something like that to find them. I donít think anybody wants them enough to do that.
Thomas:No. No. I donít think so.
Bentley:They were beautiful vehicles. They were twice as big as the Sno-Cats we had before. Theyíre twice as big as any that Tucker Sno-Cat has built before or since. They were designed specifically for this work up on the high polar plateau and they were very good for that, you know, where itís really cold. So that went until the late Ď60s, and then they went to Dome C for a couple of seasons doing the same sort of work in detail: a lot of seismic refraction, and related geophysical work around the Dome C area in this station program. No, not traversing in that case. And then in Ď73 we started the Ross Ice Shelf project.
Thomas:Okay. So, running up to that, what, before that point — when did the drilling begin in Antarctica? That was in the late Ď60s as well?
Bentley:The first drilling was actually during IGY. They drilled 300 meters at Byrd Station in Ď59, and drilled essentially through the Ross Ice Shelf at Little America. They stopped just short of going all the way through because they didnít want to penetrate the ocean. But the first drilling to the bed was in Greenland at Camp Century. And, letís see, Ď68, I think it was, when they reached the bed at Byrd Station. And, that was the first deep drilling to the bed on the grounded ice sheet (also called the inland ice sheet) anywhere in Antarctica.
Thomas:So, with your seismological work, what sorts of things were you able to find out about the bed of the ice sheet at that time?
Bentley:Well, we got an idea of what the crustal structure was in various places, how it varied across West Antarctica, and East Antarctica too. [Gets volumes off shelf] I think thereís a summary article in this volume here. In fact, I think thereís some summary articles in these two volumes also, maybe three of them. Letís see if I can find them. [Turning pages] Here we go. [Turning pages] Yeah, this is a pretty good summary of it. I think thatís the latest of it. That wasnít all my work. I did a lot of compilation of all the geophysical studies I could find. All the crustal studies, so it includes surface wave analysis, andÖ [turning pages]
Thomas:Let me just jot that down real quick.
Bentley:I think that would probably be — I was just wondering if that book is — who published that?
Thomas:This is Australian Academy of Science.
Bentley:Yeah. That should be fairly easy to find.
Thomas:Yeah. Iím sure the University of MarylandÖ
Bentley:There are earlier summary review papers in this one, behind this one, but I think these would be harder to find. Well, that oneísÖ Universitatsverlag, which was published in Norway. Then this one, oh this one was published by the University of Wisconsin Press, actually, I think. After this monster — they had so much trouble with this they said they were never going to publish another. Yeah. Yeah, that was published right here. And I have a couple review papers in here. If you find it, that oneís — I mean you could just find it. If you want to just write down theÖ if you think it might be easier to find.
Thomas:Yeah. I already wrote down the Antarctic Geoscience thing.
Thomas:So, we should be able to dig it out of the usual sources.
Bentley:There are a couple of articles. One on specific new work and the other a review work. So the most important thing is, I think, that came out of those deep geophysical studies was evidence for the striking difference in crustal structure between East and West Antarctica. West Antarctica has a much thinner crust and itís not truly continental at all, or central West Antarctica is not truly continental. Itís a rift zone. But, there are volcanic islands that are continental, then Marie Byrd Land, and the Horlick Mountains, and the Ellsworth Mountains, and — theyíre not volcanic, the Ellsworth Mountains. But the region in between has been rifted. Itís thin crust. Itís distinct from East Antarctica, which is a true — itís mostly Precambrian. At least, thatís what people believe. Because, they still havenít done much research on whatís in the center of East Antarctica. I mean, thereís a big mountain range that goes up to 3,000 meters above sea level, which is not what one thinks of as typical of a Precambrian shield. But, the geologists, so far, have been going blithely along saying that itís all Precambrian because itís Precambrian along the coast. Iím not convinced.
Thomas:Okay. So, I guess Iíd like to get into RISP [Ross Ice Shelf Project] and RIGGS [Ross Ice Shelf Geophysical and Glaciological Survey] pretty soon, but Iím wondering if we should talk a little bit about building an Antarctic science program here at Wisconsin, in terms of students, classes, research groups, or anything of that sort, before[hand]?
Bentley:Well, we didnít have a glaciology program as such. I probably couldnít consider it really that— I mean, it was always really a geophysical program. The geophysics my students did was on ice, almost exclusively but not entirely. I mean, I had students who did other things like magnetotellurics in Northern Wisconsin, for example. But, by and large, my students applied exploration geophysical techniques to studying the ice sheet. So, they learned how to do seismic measurements, and gravity measurements, and magnetic measurements, and electrical resistivity measurements, and radar sounding, airborne aeromagnetics. We did all those things. And that fit in well with the geophysics part of a field-oriented geology and geophysics department. And, the first students were the ones who had come back from the IGY. They didnít have Ph.D.s. Only Ed Thiel and I had Ph.D.s when we left. So, they came back here and they were working, at first, on their own thesis projects. Then other students just came. I didnít do much recruiting of students. They pretty much came through the normal application process for students who wanted to come and do geophysics. And, some of them got interested in glaciology after they got here. I mean, the glacial applications. There were still geophysics programs. Some of them, but then with time more and more people applied to come and do, specifically, to do geophysics on ice.
Bentley:Woollard did quite a lot about building up the initial program here. He managed to get a, a grant from the National Science Foundation just to support the development of the Geophysical and Polar Research Center, and that was helpful. Then, we had that for some years and then NSF decided that they werenít giving — at least the Antarctic Program wasnít giving out grants just for institutional purposes. They had to be research grants. But, by that time Woollard had gotten the place pretty well going. We had the going Antarctic Program that was, that I led, and there as an Arctic Program that Ned Ostenso led. And, there was a Continental Geophysics Program that Bob Meyer led that didnít have anything to do with the polar regions. Those are the three main thrusts of the geophysics program here for quite a few years.
Thomas:Okay. Shall we move on to RIGGS then?
Thomas:All right. I have the write-up that you did of it afterwards, but Iím wondering if we could just kind of get into some of the origins and the extent of what you did with it?
Thomas:Yeah, so I guess Iíll just let you start from the top.
Bentley:Well, at the time we were working on it at Dome C [Pause 11 seconds] — noÖ Iíve gotten something wrong. Iím trying to remember now what I was doing in the early Ď70s, after I did the — what have I forgotten? The reason I know thatís wrong is because Iím off by a decade. I was working at Dome C around 1980, or the late Ď70s, because I went from Dome C, where I was doing sonic velocity measurements in the drill hole, and I took that logger down to the Ross Ice Shelf where they had already finished some holes and did logging there. So, that obviously came after the — that was Ď78 to Ď80 or so is when I was at Dome C. So, in the last part of the Ď60s and the early part of the Ď70s, a couple years, I guess thatís when we were doing radar work out at Byrd Station.
Thomas:Okay. I have the list of publications if that would help put you in the time and place. [Turning pages]
Bentley:Yeah. Yeah, I was working with John Clough on radar work in West Antarctica.
Thomas:Right. ďElectromagnetic Sounding at Byrd StationĒ.
Bentley:And that may be in a time when I may not have gone to the Antarctic for a couple of years. But, at any rate, along about that time, I think I was first associated with the Committee on Glaciology about 1973. I think I sent you that date, which I was just looking at, which is how I happen to have it in mind, because you can tell, you can tell my memory for dates is pretty poor.
Thomas:Well, itís a lot of decades to keep track of.
Bentley:Oh no. I didnít print out the message I sent you. Does that say when I was on the Committee on Glaciology? I donít think it does. The Committee on Glaciology was a committee of the Polar Research Board.
Thomas:No, just ďPolar Research Board.Ē
Bentley:Earlier it was called a ďGlaciology PanelĒ. That was when the Polar Research Board was called the Committee on Polar Research. But, at any rate, I donít remember exactly when I got involved in the planning. I donít think I was in on the very earliest planning, but there was interest in drilling a hole. The start of the Ross Ice Shelf Project was to drill a hole through the Ross Ice Shelf. AndÖ
Thomas:Yeah. I have the, what you wrote here. [Reading] ďIn 1969, J.W. Brody suggested a multidisciplinary study centered around a drill hole through the Ross Ice Shelf so it would be possible to study not only the ice but also the ocean and ocean floor beneath the ice shelf.Ē
Bentley:Yeah. Well, then do I go on and say how we got? — youíd probably do better to read that than to listen to me. Because I knew what I was talking about when I wrote that. But it just seemed to me, as I remember, that as long as there was going to be this work on the Ross Ice Shelf, it was a perfect time to start a 2D study of the Ross Ice Shelf from a geophysical standpoint. So, we proposed to do a Ross Ice Shelf Geophysical Survey. RIGS was one ďGĒ. And this was a big step forward in the type of Antarctic support that we were going to have, because everything else we had done had been along traverse routes, and now we were going to be able to study the whole area, length and breadth. And NSF bought into the idea, and so they hired the Twin Otters to ferry us around from spot to spot. So, instead of doing traversing along linear routes, we went station hopping, covering the Ross Ice Shelf, close to 200 stations I think by the time it was done. [Turning pages]
Bentley:Yeah. Thatís pretty much the full picture.
Thomas:On page six of this [Bentleyís published report on RIGGS activities].
Bentley:Now, while I was still in the planning stages I think Bob Thomas, himself, proposed that there should be a glaciological component, other than the glaciology that we were doing as part of the geophysics. So, he proposed to add glaciology to R-I-G-S, RIGS with a single ďG,Ē and that went forward. That was a good idea. So, then it became RIGGS with a double ďG.Ē This was how that happened. So, Bob Thomas and his group were taking positions and then going back after a season and remeasuring positions. They were doing the surface glaciology and we were doing the same sort of geophysical work that we had done before. Primarily, I mean, seismic sounding is necessary to get the water depth. I mean, we had radar by that — Our first successful radar work was up on the South Polar Plateau in the mid Ď60s. By the Ď70s it was more routine, at least on the surface. Well, we found out, in the course of our first season, that we couldnít correlate between ice thickness measurements from spot to spot just on the fifty-kilometer grid. So, John Clough decided he would rig up an airborne radar sounding system and he just jerry-rigged, put some strings and wires underneath the wings on the Twin Otter aircraft and put the radar in the plane, and lo and behold, he added an airborne radar sounding program. So, then we started flying radar lines between all the survey spots. Then we had detailed information.
Thomas:That was as effective as doing it on the surface or were there sacrifices involved in doing it from the air?
Bentley:Precious little. You get the advantage of coherency from one spot to another. The radar signal tends to go in and out. Some people have called it the Picket Fence Effect. You get a strong echo, then a weak echo, then a strong echo, and if youíre doing it too locally, you canít make much sense of it. [Ö] Whereas, if you do it along a fifty-kilometer line, then itís obvious where the echo really is. You just extrapolate or interpolate through the soft spots, so to speak. So, [Ö] there were some types of measurements that we had to do on the surface like wide-angle experiments where you increase the separation between the transmitter and the receiver. So, thatís a way of measuring the wave velocity in the material youíre getting a reflection through. Thatís both a radar technique and a seismic technique.
Thomas:Were you still using seismic techniques at all?
Bentley:Yeah. Seismic techniques became particularly important on the Ross Ice Shelf project because you canít see through water with radar. So, in order to measure the water thickness under the ice shelf we had to use the seismic method. I didnít have any other choice, which pleased me because I like seismic work. I think itís still useful.
Thomas:Could you describe the seismic apparatus real quick? Like, what exactly is it that creates the wave?
Bentley:Oh, a little explosion.
Thomas:Itís a little explosion?
Bentley:Yeah. We use anywhere from a third of a pound of TNT up to hundreds of pounds, depending. The hundreds of pounds are for the long refraction shots where youíre trying to get energy to travel twenty kilometers or something like that. But, for the basic reflection shot, a small charge was not only enough energy, but it was preferable because it produced higher frequencies, and the higher frequencies are easier to see through background noise thatís of lower frequency. So, you just set off a charge. In Greenland I just dug a hole with a shovel to put the charge in, and that did not work very well. You have to get it at least a few meters down to get it in snow thatís a little bit firmer and get it below the steepest part of the velocity gradient, which focuses the energy upwards and therefore not downwards, which is what you want when youíre trying to get a reflection. So, we had hand augers on our IGY traverses and the typical shot-hole depth was four meters, and then we got good echoes from four meters. And then the glaciologists would normally drill a ten-meter hole, because thatís a standard depth at which to measure temperature in the ice. And, when they were done weíd shoot a shot in the ten-meter hole, and then it often gave even better results. Then, when we went up on the South Polar Plateau we had a continuous flight auger mounted right on the rear end of a flat-bed Sno-Cat. Well, then we were drilling forty meters. And, because the cold snow reverberates for a long time on a high polar plateau, the only way you can get that reverberation to diminish is by putting the shot a long way away from the surface. The deeper the shot the farther it is from the surface, and the less it generates this shot-generated noise at the surface. But, we had to go tens of meters deep in order to get decent echo on the South Polar Plateau. And then they set out a string of geophones or detectors, the standard cable is 360 meters long with twelve [takeouts?] of thirty-meter spacing. And, you set two of them out, usually, either end to end or in an L shape [Ö] If you want to measure the slope on the bed then you canít just have it along one line; you have to measure two components of a slope in order to get an absolute slope. So, the geophone is just a little weight thatís suspended in a magnetic field, weakly suspended. Itís a motion detector. When the sound hits the geophone, the weight wiggles the spring in the magnetic field and that generates a little EMF and that produces a signal thatís amplified. And then, the rest of the seismic system, back in the IGY days, was great banks of amplifiers. Youíd have to have an amplifier for each one of these traces. So, our seismic system had twenty-four amplifier channels. But, of course the amplifiers were big in those days because everything was done with vacuum tubes. The solid state devices were just beginning to come into practical use in the oil, in the geophysical industry, exploration industry, but solid state devices were still noisy. They had a high background noise, and that was not appropriate for use in the Antarctic because the natural environment Ö.
Thomas:Are we still talking during RIGGS here, or are we earlier?
Bentley:No. Now IímÖ
Thomas:Back at the pole?
Bentley:Yeah. Back at the start of IGY.
Bentley:So, this is why we had vacuum tubes. There were solid state devices that were just becoming available but they were too noisy. And since the background level in the Antarctic is extremely low, unless itís windy, you donít want to be limited by your electronic noise level. So, thatís why the people who were planning the instruments for the IGY went to vacuum tube systems. Now, by the time of RIGGS we were still using the same old gear that we had from the IGY. We didnít have a lot of money to buy what the people were using in the industry by that time. We did get a couple of digital systems to try out, that oil companies or exploration companies gave us, that they were through with. But they werenít very successful. So, the first real digital system we had in our program was home-built, and we didnít have it for RIGGS. We had it for the next decade when we started on the West Antarctic Ice Sheet.
Thomas:That was the Siple Coast Project?
Bentley:The Siple Coast Project. Thatís right.
Thomas:Okay. Thatís interesting how long it takes for the technology toÖ
Thomas:Do you want to take a break? Weíve been going at it for, I donít know, what have we got here on this? An hour and a half so far. Okay. So, we were just talking about RIGGS before and I think we left off with some of the technologies that were being used, the seismic technology, and you were discussing a bit about the radar technologies as well. So, what else should we discuss about the project?
Bentley:Well, it was, the Ross Ice Shelf problem. RIGGS was when we first started doing electrical resistivity measurements. We got interested in the electrical properties of ice, both for our interest in the physics of ice itself — the electrical properties are particularly interesting — but also as another way of studying the ice from a glaciological standpoint. And, at one time, this is a bit of an aside, but at the start of RIGGS I was afraid that we might have to have all our support flying done by helicopter and Iím scared of helicopters. They seem to have a tendency to crash in the Antarctic. And that really worried me. But fortunately, the helicopter pilots said they wouldnít fly anyplace where they didnít have something other than a pure, flat, white horizon to go by. So, if theyíre out of sight of land, so to speak, they canít see the mountains, they donít want to fly. Thatís for safety reasons too. So, itís very sensible. Well, of course, most of the Ross Ice Shelf is not within sight of the mountains, except on an exceptionally clear day. So, that idea went by the boards and we got the Twin Otters. Iím enamored of the Twin Otter. It can land anywhere on skis. Itís a STAL aircraft: short takeoff and landing. So, it takes off in a hundred meters or something like that, and itís ski-equipped, of course, so it can land anywhere. And if they have to come down in a whiteout they just gradually come down until the skis hit. And, we never had any problems with the Twin Otters in our four seasons with RIGGS. We had some problems with some of the pilots who didnít always want to fly when we thought it was okay to fly. But, of course, we had to defer to them. I mean, the safety of the aircraft was the responsibility of the pilot, and we couldnít override him, nor did we want to overrule that. That really was just one guy at one time. But, by and large, we had huge success with the Twin Otter support. And, Twin Otters have been supporting the U.S. program ever since. That was the beginning of the Twin Otter support for the U.S. Antarctic Program. The Ross Ice Shelf Project itself, drilling the hole was several years in the development, and it was partly in parallel between the U.S. activity headed by Jim Zumberge, and SCAR activity, which was also headed by Jim Zumberge.
Thomas:Could you tell me a little bit about him? I donít know much about him. Iíve seen some of the write-ups that heís done on this.
Bentley:Zumberge was down in the Antarctic. He did a study of ice deformation in the Little America area, where the ice is deformed where it flows around Roosevelt Island. It was one of the years I was down there. Iím not sure. I canít remember for sure whether it was the first IGY year, whether it was Ď57-í58 or Ď58-í59, or maybe it was both, but it was very early on he was doing this glaciology program there. [Ö] I donít remember where he was at that time. But at any rate, soon after he came back he became president of Grand Valley College in Michigan. [Ö] Larry Gould (who was the SCAR representative and the head of the Polar Research Committee on Polar Research, at that time — and sort of Mr. Antarctica in the U.S. at the time) he [Zumberge] became Gouldís anointed successor. Gould pretty much decided that he wanted Zumberge to follow him in these roles. And I think Gould was influential in Zumbergeís establishment at University of Nebraska with the Ross Ice Shelf Project office. And, then, Zumberge turned [RISP] over to Bob Rutford after a couple of years and he went off to California, USC. He was president of USC. And then he was the SCAR representative for years, and he was the president of SCAR, and then he died at much too young an age. I forgot how, I mean I think he was just sixty or something, all after he went to USC.
Thomas:Okay. So, we were discussing the starting up thenÖ
Bentley:Yeah, so through a combination of interest in the United States and interest in the international community that I think was driven primarily by the U.S. and New Zealand (who has a particular interest in the Ross Ice Shelf), the Ross Ice Shelf Project was developed as an international program, but with the international and national project offices centered sort of in the same organization, as I recall, at the University of Nebraska. And they got Lyle Hansen from CRREL. You know what CRREL is?
Thomas:Yeah. Johannes Weertman was telling me about that.
Bentley:Okay. He told you about CRREL?
Bentley:Well once upon a time it was Snow Ice and Permafrost Research Establishment.
Bentley:Yeah, it was SIPRE and it changed to CRREL in the Ď60s sometime.
Thomas:When they moved to Hanover [New Hampshire].
Bentley:When they moved to Hanover and joined withÖ
Bentley:No, not with Dartmouth. With another Army environmental lab. SIPRE and another Army environmental lab joined and moved to Hanover and became CRREL. But, there was another division that I had totally forgotten about myself until I was doing a little review work on that. Nobody ever thinks of this other group. I mean, all the fame and fortune and all the good work came out of SIPRE and CRREL. But, there is another outfit. [Laugh]
Thomas:We can always look it up.
Bentley:Yeah. I have it somewhere. Actually, I probably have it on my laptop, but itís not worth looking up. Thatís too far afield. But Lyle Hansen was one of the ace drillers from CRREL. He went in charge of the drilling development in Nebraska for the Ross Ice Shelf Project.
Thomas:Whereís the funding on this primarily from? Is it NSF yet, or is itÖ
Bentley:No, this was NSF.
Thomas:[Ö] Sorry, Iím getting my history possibly confused. Was that in partnership with the Navy then, the aircraft support, or was that [inaudible]?
Bentley:In the Ď70s the Navy was still doing all the support activity for the Antarctic Program. They didnít phase out until [the] late Ď80s, I think it was. But it wasnít like an IGY station. I mean, the base camp for the Ross Ice Shelf Project was not staffed by Navy, like McMurdo was at the time, and like Byrd Station, and like the IGY stations had all been, like South Pole Station still was at that time. It was all civilian. The Ross Ice Shelf Project and the Polar Ice Coring Office, which were co-existing organizations at the University of Nebraska at that time — PICO, I think, was the one that was responsible for the support activity. No, I think thatís backwards. I think PICO was responsible for the drilling and Ross Ice Shelf Project was responsible for the support activity. Anyway, Iím not sure. The reason I had to change my mind about that is because it sounds like Polar Ice Coring Office ought to be involved with the ice coring, doesnít it? So, thatís being more logical. But, anyway, one did one and the other did the other. And then they were both there. And it was a troubled program. They froze in a drill their first season, and their objective [Ö] was to access the ocean and they wanted to do it in as clean a way as possible. Not introduce contaminants into the ocean. But, they failed with their wire-line drill that they had high hopes for, not particularly because of the fault of the drill, but, for reasons that still arenít clear, they — Iíve talked to people about this because I did a little review of drilling history some time ago, and Iíve talked to several people who were directly involved with the program and they donít agree as to what happened. But what they all agree on is that the drill got caught in the ice, because it was left too long and there was no fluid in the hole, because they didnít want to introduce any fluid into the ocean underneath the ice shelf. But, if you go down three or four hundred meters — I think the ice was 450 meters thick; maybe they were down 350 or something — the ice closes up in a hurry if you donít, because youíve got all the overburden pressure of the ice tending to close the hole. Ice flows quite rapidly as — I mean if youíve been talking to Weertman youíve been talking about how ice flows. So, the main reason in drilling in ice for putting fluid in the hole is not for chip transport or to lubricate the parts; itís to keep the hole from closing. Glaciostatic pressure has to be balanced by the hydrostatic pressure. But they didnít have any fluid in that hole, so when they stopped drilling for too long, only a half an hour or something like that, the ice closed in and grabbed the drill and they never got it back. So, the next season [Ö] there were all these principal investigators on biological and oceanographic projects who were waiting for the access hole to be drilled into the ocean so they could do their experiments. And, I think some got as far as McMurdo, some got as far as New Zealand, and then they were all on hold waiting for the hole to be finished so they could go and do their work. Well, the hole never was finished that year. So, they decided the next year they damn well better have a hole and not let anything like this happen again. So, Jim Browning had a giant blow torch, a flame-jet drill. Itís used for drilling in solid rock. It has such a powerful flame it melts solid rock. And so they decided this is a way to get through the ice shelf. So, they brought down this giant blow torch. Itís just an acetylene torch [Laugh], a huge acetylene torch; only it doesnít run on acetylene. They ran it on fuel oil, and I donít remember whether they had oxygen or they just used compressed air. But, in order to keep it going underwater — this was melting the ice so they had water in the hole, and they realized they had to leave the water in the hole in order to keep the hole from closing — in order to keep the flame going underwater they had to have an extremely rich mixture, most of which didnít burn. I donít know the chemical reason for that. But, the point of that was that this giant blow torch also produced huge amounts of soot, so they wound up with this machine that was absolutely the dirtiest way they could possibly find to drill a hole through the Ross Ice Shelf and into the ocean below. Nevertheless, the project was, in the end, successful. They got a lot of interesting work done. One of the most interesting things from the biological standpoint I remember is, after they had the access hole, they lowered a long string with some meat, like bait, on it, all the way down to the bottom of the hole to see if there was anybody down there who was interested. And before very long a whole swarm of amphipods — amphipods are little shrimp-like creatures — came swarming in. This is several hundred miles from the open ocean under the completely lightless — I mean thereís no light underneath the Ross Ice Shelf. So, there can be no plant life. You can understand why these little animals were pretty hungry after going thousands of years without anything to eat. And, itís just a picture that you would have of piranha attacking a cow skull in a South American river.
Thomas:They had a camera down there? OrÖ
Bentley:They had a camera down there taking a picture of it. Yeah. Itís very dramatic. Anyway, so it did turn out to be a successful experiment, and they eventually got several holes through the ice. They switched from the flame-jet drill to a giant hot water drill, which of course is much cleaner. In fact, there isnít anything thatís less polluting than using hot water to drill a hole in ice, because youíre drilling it with the same fluid thatís formed the ice, obviously, and itís not going to pollute the ocean either. So, while all that was going on, [Ö] we started first (ďweĒ being RIGGS) — one of our jobs in the first season of RIGGS was to pick a spot for the drill hole.
Thomas:Before we get going on this, just as far as getting RIGGS going, you were mentioning earlier, and it went by kind of quickly, that you were kind of leading the R-I with a single G, S effort to get that kind of involved in this RISP project?
Thomas:Okay. So, who did you go to, Zumberge? to get that going? Or, was thereÖ
Bentley:No, I think we had their approval but it was a standard NSF-supported grant. I mean we wrote grant proposals, and they were tied together. Oh, I have an idea that maybe the impetus — now, I may be entirely wrong about this — but remembering that one of our first jobs was to use our geophysical tools to try and find the best spot to drill the RISP hole, maybe we were asked to do something like that, and I decided as long as we were going to do that we might as well survey the whole ice shelf. I donít remember how I came up with that idea.
Thomas:Well, we can confirm it from the report.
Bentley:Yeah. It may or may not be there.
Thomas:OK. Sorry, but just as long as weíre on the topic, were there administrative papers for the project that were kept anywhere, or were those in your files?
Bentley:Well, I have a lot of files on the RIGGS Project, including some of the more administrative aspect, I think like grant proposals and stuff like that.
Thomas:I was just wondering where we might be able to find some of that?
Bentley:Yeah. And some of those might still be in the financial records here at the University of Wisconsin. If weíre just talking about the proposals themselves, and any reports [Ö] ought to be at the National Science Foundation too.
Thomas:Okay. Would Nebraska have kept anything?
Bentley:Well, Nebraska, yeah. Nebraska would have had all the stuff from the drilling project. We wouldnít have had any of that.
Thomas:Okay. RIGGS was run out of here?
Bentley:RIGGS was run out of here.
Bentley:Yeah. Oh yeah, I should have mentioned that. Yeah, the RIGGS Program was our primary activity from Ď73 to í78. And, yeah, we ran it out of here. Now, the arrangements — Iím trying to remember who made the arrangements — I canít remember for sure who made the arrangements. We had a logistics office that was very active during the Ď60s and petered out sort of during the Ď70s, I guess it was because the Ross Ice Shelf Project took over the logistics. I guess they made the arrangements for the Twin Otter support for us. Iím a little vague on that, because I think by that time our logistic office, which has been there primarily to run the Over-Snow Traverse Program to provide the mechanics for taking care of the vehicles and that sort of thing, I think that had ended. So, the logistics support was all by Ross Ice Shelf Project. The science part was all run out of here, including the people. They all came from here. I mean the geophysicists who were doing the research program. So, one of our jobs the first year was to find a spot that had the best combination of ice thickness and water depth below the ice to suit a bunch of criteria that the RISP planning people had come up with for a compromise between what the glaciologists wanted and what the oceanographers wanted. And so thatís how I know that we started first, because we did that in our first season. We found a good spot. It became known as J-9. J-9 was actually a designator that came from the RIGGS Project. That was our station. We had a letter-number system. One was east-west and one was north-south.
Thomas:Yeah. I always get confused in this polar geography. But, yeah, the numbers go east-west [on the map in Bentleyís RIGGS report].
Bentley:Oh yeah, that map is done on a grid orientation. Yeah. So, I guess our second season at RIGGS was the first season of the drilling, Ď74 to — no, thatís not right. No. It took them longer than that to get ready. Because, they didnít start drilling until Ö at least 1975, Ď75-í76, and I think it may have even been Ď76-í77. Yeah. So, I guess we went through two seasons of RIGGS, then we took a year off. That may have been when the drilling started. And then, we did two more seasons to end up.
Thomas:So, what was your contact then, or the relationship with the glaciologist, who was (Bentley: Bob Thomas?) — yes. Bob Thomas, and the people who were working with him?
Bentley:Well we all worked closely together.
Thomas:Okay. Were you kind of in the same places at the same time, orÖ?
Bentley:Yeah. Well, the first two seasons there was just one base camp. And it was somewhat of a complex process to try and arrange effectively for the Twin Otter time to go and take one group. Our geophysicists, and he and the glaciologists did not work at the same spot at the same time. So, the Twin Otter was shuttling one group to Point A and then shuttling that group to Point B and the other group to Point A.
Thomas:Right. And Doug MacAyeal was telling me yesterday about them dropping off equipment just on the fly as well. The way he described it was like those tricks where they pull the table cloth out from underneath of the things on the table.
Bentley:Yeah. What do they call that? Thereís a word for that. Freight lining. I think thatís the term. Freight lining? Where they do that with [Herc shell? [C-130 Hercules aircraft]]. They used to do it quite a lot where the [Herc?] never even stops. They just push the stuff out the rear door. Itís landed, but they just push the stuff out the rear door while they drive forward. Yeah, now Bob Thomasí crew, after the first season, they had to go back to as many stations as they could find at the beginning of the second season to reoccupy them, because the transit navigation system — I think when they first started they had only celestial, only solar, navigation. But, I think at some point early on, maybe it was still in the first season, they had the Doppler satellite receivers.
Thomas:MacAyeal was telling me about this yesterday. Where they track the satellite across the sky?
Bentley:And they had those right off from the first season or did theyÖ
Thomas:He was only there, I think, for a couple seasons toward the end. So, I donít know.
Bentley:No, [Ö] I think he was there in the first season.
Thomas:Iíd have to double check.
Bentley:Or maybe not the first season. Well, [Ö] he ought to know. But, I remember being there at the same time he was, and it wasnít Ď77-í78.
Thomas:I think he graduated from Brown in Ď73 as an undergraduate, and then went up to Maine. Well, Iíd have to double check. Youíre probably right.
Bentley:Well, heís probably right. [Laugh]
Thomas:Yeah. Well, I donít remember exactly what he said. Weíd have to check the time thatís on there. So anyway you got to work with Bob Thomasís Ö
Bentley:Yeah. SoÖ you know, Iím having trouble. Iím not sure that Iím right. It may be that part of the time we had people who were at the same station at the same time. Gee. Thatís only thirty-five years ago. I ought to be able to remember that better than that.
Thomas:Yeah, I know, seriously, whatís wrong? [Laughter]
Bentley:But at any rate, Thomasís group, at least, I know this is right. They had to go back, even with the transit satellite, the Doppler satellite — it wasnít accurate enough so that they could measure movement in one season like you can do now with GPS. They had to go back the next season and remeasure the spot in order to get the movement of the ice, which is how they drew all those arrows in that report. But it seems to me that even at the first visits, we were sending the parties to the same group of stations, but at different times. Gee. That bothers me that I canít remember that. Well, I donít know for sure. No! No, by golly. Now I do know Iím wrong about that. The groups went out together, because I remember one specific case where I got annoyed at Bob Thomas and John Clough, who were out together. Since John Clough was my grad student, he was doing the geophysical work and they were at the same — I have something to peg my memory on it. I got annoyed one time because I was staying in base camp and tried to make the most efficient use of the Twin Otter, and schedule which spot it would go to and which party it would pick up and move someplace else. And, they called directly to the plane and called for the plane to come out and get them, which was not whatÖ
Thomas:It wasnít on the schedule?
Bentley:It wasnít on the schedule and it screwed everything up for the whole day. [Laugh] So I think that was the only time I lost my temper in the course of the RIGGS program. I got mad at them. I was talking about John Clough. John Clough and I have renewed our friendship in recent years. The last couple of years I visited in Marthaís Vineyard where he has a family home. I was just there a couple weeks ago. And, he doesnít remember this. He doesnít remember this story at all the way I do, but he does remember that something happened. But, other than that things went very well. We got along.
Thomas:Okay, so since this is kind of the same period when the West Antarctic Ice Sheet stability question starts kind of percolating, I thought I might ask at this point: just how prominent was it of an issue? I know that the way that the review articles tell the story of it is that in 1968 John Mercer has a paper linking six extra meters of sea level to West Antarctica. Terry Hughes picks up on this in the early 1970s. Hans Weertman has his 1974 paper. And so this is as RIGGS is going on.
Bentley:Yeah. Yeah. And we did some work across the grounding line, particularly under Bob Thomasí instigation. It turned out not to be on an ice stream but on the end of Ridge BC, I think, what used to be called BC.
Thomas:This is when you kind of discover the importance of the ice stream, is in this period, right, with RIGGS, or is that later on?
Bentley:No, the real discovery of the ice streams was with the NSF-SPRI-TUD [NSF-Scott Polar Research Institute Technical University of Denmark] radar sounding flights.
Bentley:We didnít get far enough inland to learn much about the ice streams as part of RIGGS, but we were learning about them from other radar flights that were done. We did a lot of radar flying, of course, in the Siple Coast Project, all over the ice streams. But yeah, the interest in that boundary zone was just developing and I wouldnít have remembered that Weertmanís paper was in Ď74. But, by the time we had absorbed that, I think we were on our year off, or working over on the other half of the ice shelf away from the West Antarctic inland ice. So, it didnít really have a strong influence on our work on RIGGS.
Thomas:Oh, and I should also mention, I mean we already discussed the ice age theories but a lot of the idea of surging, aside from, you know, mountain glacier surging, has to do with Alex Wilsonís ice age theory.
Bentley:Oh yeah. Yeah, where the ice surged out and created a huge band of ice shelf all around Antarctica, and cooled the climate down. Yeah. I remember that.
Thomas:Yeah something like that. And that was something that Hughes and Hollin seemed to take seriously in the early 1970s. I mean, MacAyeal was giving me his perspective on how these guys Ö
Bentley:Hughes, and who was the other one?
Bentley:Oh, John Hollin. Oh yeah. Yeah. Most of us didnít take that too seriously. Doug MacAyeal didnít take it too seriously did he?
Bentley:Thatís a question.
Thomas:Well, he said that when he was doing his undergraduate work [on a catastrophe theory of ice ages] everyone thought that he should go to Maine because thatís where the crazies hung out, [Laugh] and so thatís how he ended up, with Thomas and Hughes up there before going on and getting his Ph.D. at Princeton. And he mentioned that the Wilson thing was — that a lot of people came through Maine in that period — well, I know he said Hollin came through — but that it was kind of viewed as quackery, but that Hughes kind of had a collection of quack theories that he sort of integrated into his own work.
Bentley:I was at Plateau Station, I believe, in about Ď68, and I went out to Plateau and helped get the traverse ready before the last leg of that traverse up there. And, I was sitting with a guy that I didnít know in the mess hall once and we were talking about glacial matters, and the subject came up about Alex Wilsonís theory. And, I said it was kind of extreme, but I was quite restrained and polite about it, and it turned out the guy I was talking to was Alex Wilson. [Laughter] I had no idea that he was at Plateau Station. I donít know how heíd gotten there or why he was there. He was a really nice guy. And, Iím sure he was quite used to people taking violent objection to his theories. But, no, we were not influenced by that. We were still primarily in a geophysical mode.
Thomas:Sure. And, then Bob Thomas would have beenÖ
Bentley:Now, that does not include Bob Thomas. Bob, of course, was taking care of the glacier movement, what the people from Ohio State used to do on our traverses. Not glacial movement, but I mean the other things, pit studies and that sort of thing, ten-meter temperatures. And so we continued to do geophysical work, it was under the Ross Ice Shelf, under the ocean —.
Thomas:Sorry, I just ran into: Doug MacAyeal was in Antarctica in Ď76 and Ď77, according to his CV. I just happened to notice that sheet.
Bentley:Well then he must have been at C-16. Because, I know I was there at the same time he was, and my mental picture of — I remember his being there and going out on a snowmobile once to guide a plane in out of the fog. The Twin Otter landed, but once he landed he couldnít see anything because it was a foggy day. So, the Twin Otter revved up his engine so people could hear him and then Doug MacAyeal hopped on a Ski-Doo and drove out to find the plane and then lead him back in to the camp, so he could find the camp. Did he tell you that story?
Thomas:No, he didnít tell me that particular one. [Shuffling papers] So, letís see here. You write a couple papers with Bob Thomas then. They come out in 1978.
Bentley:Yeah, what happened there was that he had a draft paper in which he was talking about the interaction at the ice shelf-inland ice margin and he was using a bunch of data that he had gotten from us, not without putting anybody as a co-author but without even — I think there was a bare acknowledgement. And I took exception to that. I said, ďOur geophysical measurements of ice thickness are just as important as your measurements of movement, if youíre going to be studying mass fluxes. So, this should be a joint publication. It shouldnít just be yours using our data without our participation.Ē And so, he said, ďOkay.Ē And, he put me on as a co-author on his paper. But then it turned out that his paper had all this additional work that he had done, theoretical work. And it was originally all one paper. This was the only part that I thought I should be on, representing Wisconsin. (Thomas: I see.) But, when he split it off, he kept my name on this one, too, kind of in a fit of pique, and I should have taken my name off. But, instead what I did was put some time and effort into going through it all, and making sure that I agreed with what he said and, you know, made some additions and corrections. Mostly corrections. But, the ideas behind this work are Bob Thomasís. I get credit, I still get credit for participation in that that I donít deserve.
Thomas:Right. Because at this point you were still almost entirely geophysically concerned and not with the — well, like ďModels for Holocene RetreatĒ, for example.
Bentley:Right. Yeah. And actually, when I started working on that paper, that was what really got me interested in that kind of problem. That was my first. I mean, I thought Terry Hughesí ideas were a bit far out. Not as far out asÖ
Bentley:Öas Wilson. But I didnít take Terry Hughesí stuff too seriously either. But working on Bobís paper peaked my interest in that, which then continued from thereon. [It] remained a growing interest of mine. And particularly when I went off to Dome C around 1980. But then, in the early Ď80s, we all went over and started — well, by that time Bob Thomas and I had come to a parting of the ways. But then we started on the Siple Coast Project, and then of course we were very much interested in the boundary problem.
Thomas:Right. So weíve done a lot on RIGGS. Is there anything else we should say to wrap that up, or should we move on to this period?
Bentley:Well, I think that pretty well wraps that up. Iíd just be repeating myself.
Thomas:Okay. So, I mean this is actually a very good kind of segue then, I guess, into the next period. So, you were a member of the Polar Research Board then starting in 1978. I guess I donít know whatís really involved in that. Should we talk about Wisconsin instead, or is there field work, like the Ice Dome C stuff?
Bentley:Whatís involved — the Polar Research Board is just a planning body. You say you want to know whatís involved in what?
Thomas:As being a member of it. I mean, how much time would you devote to something like that?
Bentley:Oh. Well, the main involvement in my earlier days at Polar Research Board was just going to the meetings. I was a member of the Committee on Polar Research before I was a member of the Polar Research Board. And then I was, I think, in my first years on the Polar Research Board, I was chairman of the Committee on Glaciology. And then I remained as chairman. As chairman on the Committee of Glaciology that got me the Polar Research Board. Linc Washburn picked me to succeed him as chair of the Polar Research Board. So Iíd been involved from the glaciological side for some time before Ď78. The year that sticks in my head is í73, as being my first committee assignment which was, I think — at that time it was the Panel on Glaciology of the Committee on Polar Research, which then became the Polar Research Board. But, this was all planning. This was glaciological planning as well as an annual meeting to find out what was going on. Because, in the glaciology field, there werenít enough glaciologists in those days, so we [never] had glaciology professional meetings, unless they were international. But there was this Committee on Glaciology that met once a year, and it sort of served a double purpose. One: planning and what ought to be done in glaciology. And the other was hearing from the few glaciologists that existed in the United States, what theyíve been up to in the last year.
Thomas:Right. So, you didnít have to be a glaciologist to be involved in the Glaciological — I mean, you had to be aware, obviously, butÖ
Bentley:Yeah. And, I think the more pure glaciologists, letís say, were becoming increasingly aware of how important the geophysical techniques, and exploration techniques, were to glaciology. So, I think I was certainly one of the first, if not the first exploration geophysicist-glaciologists to be on that committee. Yeah, thatís probably true, because there werenít very many of us around. But, half of the work with the glaciology committee, and then all the work with the Polar Research Board, was planning: planning what ought to be done and advising the National Science Foundation on what are the most important problems in various aspects of polar research. And then also serving as the national committee for SCAR which is another planning organization. So, there was no real direct connection between the Committee on Glaciology or the Polar Research Board and my research, in the sense that my research was not for the PRB or anything like that. On the other hand it had everything to do with my interest in how my glaciological work fit into the bigger scheme of things, which is what the PRB and the Committee on Glaciology were all about. So, my interest in these planning activities was growing already at about the same time that we started on RIGGS. Because, I think thatís about the time I started with the Glaciology Committee, just as a member.
Thomas:Going back to RIGGS, you just were spending several months at a time down there then; these werenít [inaudible]?
Bentley:I went down, yeah, several months at a time. Now, I didnít go every season, personally, but our group was down there. I went two of the four seasons. And, our group was down there four out of five years. We took one year off halfway through. Okay, so then, I think, it was just general agreement. Everybody was ready to go to West Antarctica — ďeverybodyĒ meaning the dynamic glaciologists, the geophysical glaciologists. Everybody thought that the neighboring part of the West Antarctic Ice Sheet to the Ross Ice Shelf was the next place to go, because the ice streams were of huge interest by then, and the whole West Antarctic Ice Sheet problem was — I mean in all these, if you look at these reports youíll see that the dates on all these reports, theyíre all in the early Ď80s. I did want to show you that there this was mentioned already in 1974 back when it was called WASP, but the rest of these are í83, í83, í84, í84, í85. We were having a conference to talk about this about every year and a half.
Thomas:Right. And the CO2 problem comes in around this time as well?
Bentley:Yeah. The CO2, right. Yeah. In fact, the first one of these reports that I dug out was actually this one on carbon dioxide.
Bentley:ProceedingsÖ. Iím not sure.
Thomas:Or this one?
Bentley:No, Iím not sure. I think that may be from a different — itís the same overall effort. It came from the same.
Bentley:You have a bound copy of this?
Thomas:Yeah. This is from the University of Maryland.
Bentley:Yeah. I donít, I donít seem to have a, thatís the one thatís Ö
Thomas:I just grabbed this like about a week ago.
Bentley:Yeah, thatís the one that was in West Virginia someplace.
Thomas:Yes. Berkeley Springs, West Virginia, 1982. Which wasÖ
Bentley:Yeah. I donít seem to have a copy of that anymore. Iím glad you have it because I Ö
Thomas:Yeah. I downloaded that, actually, from the governmentís (Bentley: Oh, you did?) National Information site.
Bentley:Because I have only this one left.
Thomas:Yeah. I have a PDF of it.
Bentley:I know I looked for this other one. Is that a paper that I wrote, or is that the whole thing?
Thomas:No. This is the paper that you wrote and the responses to it by Hughes andÖ Gordon?
Bentley:Yeah. So, Terry had a lot to do withÖ
Bentley:Öwith developing interest in the West Antarctic Ice Sheet. I mean, I give him a lot of credit for that. In spite of the fact that I thought some of what he wrote was wrong, he certainly did do a bang-up job of getting everybody interested. And, I think he got shortchanged, in the sense that he seemed to find it hard to get support to do any of the field work himself. He wanted to go in and study whatís now Mercer Ice Stream, and I think he proposed several times to do that, and he never got funded. And he should have, because he was an important part of the process. But, yeah, the DOE got interested because of the carbon dioxide. They had a carbon dioxide program, what did they call it?
Thomas:The Carbon Dioxide Research Division of the Office of Basic Energy Sciences, apparently.
Bentley:Yeah, they got, they got interested in this. I donít know how they got interested. If I ever knew Iíve forgotten.
Thomas:Okay. I was kind of wondering if you had had anything to do with that.
Bentley:No, not with getting them interested. They heard about it. I started working with them early on leading — I think there was that one, the Berkeley Springs one, what was the date on that? That was earlier, wasnít it?
Thomas:That was September 1982.
Bentley:Eighty-two? Yeah, I think that was the first workshop we had looking at that specifically. So, DOE and that Carbon Dioxide Assessment Program, what was the name? Never mind.
Thomas:Carbon Dioxide Research Division.
Bentley:Research. Oh, but yeah, that was the division, but — Anyway, it doesnít matter [Ö] The carbon dioxide program really did the first early work on developing statements and studying what needed to be done. So, that one is Ď82 and this one is Ď83. No, this oneís Ď85. Sorry.
Thomas:Yeah. The conference was in Ď84.
Bentley:The conference was in Ď84. But it seems to me thereís another one. Did I give you that list of files?
Bentley:It seems to me there was another one.
Thomas:Itíll take me a second.
Bentley:Or maybe itís the same one that Ö
Thomas:Thatís what you mean? [Shows Bentley a piece of paper]
Bentley:Oh yeah. Oh, I should have warned you about that. I recycle paper. Here. [The list was on the back of a piece of paper with something printed on the other side, which Bentley crosses out.] I forget to tell people about that. It can be very confusing.
Thomas:Yeah, thereís this 1980 —
Bentley:1980 in Orono.
Thomas:DOE and AAAS.
Bentley:Yeah. Thatís right. That was the first one. But, thatís the same group. This one is just a report from this. And then I donít remember this informal workshop in San Diego. And I donít seem to have any report that came out of that either. All I know about it is that thereís a file [on the list] by that name.
Thomas:Right. Which is kept at Ohio State? [The list of conferences on West Antarctica is taken from a list of files kept in Bentleyís papers, which are already archived at the Byrd Polar Archives at Ohio State University.]
Bentley:Yeah. These are all at Ohio State. So I guess DOEís first activity was sponsoring this. Oh, and thatís right, the AAAS cosponsored that meeting in Maine on the West Antarctic Ice Sheet. But obviously the Polar Research Board got interested pretty fast too, either directly or through its Committee on Glaciology. And so we got all this succession of reports aimed at that. Some focused directly on that, but some of these are just more general reports that I thought you might be interested in looking at, if you havenít already, to see how the West Antarctic Ice Sheet problem grew in recognition through the whole glaciological community, and through the whole polar community, which took a while. It seems as though it took several years through the Ď80s. Of course, thatís not really very long, in a historical perspective. But, it took a while through the Ď80s before the importance of studying the West Antarctic Ice Sheetís stability had permeated the polar community. And, of course, there was still a long time after that before other people started taking it seriously.
Thomas:Do you want to break? Weíve been on about an hour here.
Thomas:Okay. Weíll be right back. Okay, we are back. We were just discussing, off the recording, some of the workshops and conferences that were held in the 1980s and the 1990s, just kind of going through them in list fashion. I guess one thing that might be nice to do is to try and get at how all these conferences started coming up in this period, who was spearheading this, and how it snowballed in the Ď80s, Ď90s, and maybe how it was incorporated into the IPCC in the late 1980s? But, we can start at the beginning, around 1980, when you said there was that Orono conference that they have the full transcript of.
Bentley:Yeah. I donít really remember how that got started. Letís see, what was the date on that one again?
Thomas:That was 1980.
Bentley:1980? So, at that time I was probably chairman of the Committee on Glaciology, which is probably why they came to me to help them organize this workshop. I was one of the organizers of the workshop in Orono. And, in the glaciological community, there was already a substantial interest in the subject. I donít recall how the AAAS and DOE got interested in the subject. And, I donít remember why there was a sudden emphasis on carbon dioxide.
Thomas:I know that in 1978 John Mercer came out with another paper. He tends to have a heavy place in the review literature, but, as near as I can tell, there are just two main papers, the 1968 one and the 1978 one linking to carbon dioxide. After that, Bob Thomas, in 1979, wrote a paper that attempted to assess the threat to the West Antarctic Ice Sheet from CO2.
Bentley:But it didnít really relate specifically? Is that the Thomas, Sanderson, and Rose paper?
Thomas:I think it is, yes.
Bentley:Yeah, and so I think that was Ď79. Yeah. That was assessing what the response could be to an increase in sea level, I believe. But, I donít think Thomas, Sanderson, and Rose looked at the response to — I mean, they didnít have the intervening step of what all carbon dioxide might lead to.
Thomas:Sea level rise?
Bentley:Sea level rise.
Bentley:Once he got started, it took on a life of its own. I mean, one workshop seemed to lead more or less directly to another one, trying to develop a program of research on how to tackle the problem.
Thomas:Who are some of the primary figures as we move through? I mean, who would be the organizers of these workshops? [Ö] We were mentioning Hughesí involvement earlier, but NASA was becoming involved as well with Thomas there, Bindschadler, but also Europeans. Oerlemanns started becoming involved during that decade.
Bentley:Oerlemanns, of course, was the one who organized the Utrecht workshop.
Thomas:Right. In Ď85.
Bentley:I think Uwe Radok was at NSF in the Office of Polar Programs as — he wasnít a program manager. He had some special position, as I recall. And he was interested in this problem, and I think he didnít — in getting NSF support to run these workshops. And, Mark Meier, I think, was involved. Heís had an interest for a long time. He succeeded me as chair of the Committee on Glaciology, I think, when I became chair of the Polar Research Board. What might help me jog my memory a bit is if I can find the list of participants. Letís just pick the one that was held here. [Shuffling papers]
Thomas:We were talking about Environment of West Antarctica: Potential CO2 Induced Changes from 1983, here at the University of Wisconsin. [Turning pages]
Bentley:Oh, Tom Gross. Tom Gross was very active in this. Tom Gross was at the CO2 Research Division at DOE, and it was one of the primary foci of his CO2 work. The CO2 Division it seems to me was — oh, he was one of those involved in organizing the original Orono meeting.
Bentley:Yeah. I just saw his name here. That really rings a bell. I donít see anybody here from AAAS. But, the names I — yeah: Radok, Meier, myself, [turning pages]. Oh here, participants in that conference: [inaudible]. Radok was a convener of that workshop. Mark Meier was the chairman of the Committee on Glaciology. Yeah, I think we were the ones who were the primary instigators of this series of events. Plus, letís see, who would have been the — I think Dick Cameron would have been the program manager for Glaciology at Polar Programs at that time. He would have been supporting these. But, this particular one appears to have been sponsored only by the DOE, at least thatís the only one in the acknowledgements. So, I guess this one didnít have NSF support. Letís see, whereís the Seattle one?
Thomas:I think itís that one right there. That big one [Ö]
Bentley:I remember Craig Lingle did the write-up. But that wasÖ Mark MeierÖ
Thomas:[Reading] U.S. Geological Survey.
Bentley:Yeah, I wonder if this Ad Hoc Committee on the Relationship Between Land Ice and Sea Level, is that the last item on that thing I saw you file there away?
Thomas:Down here. Ad Hoc Committee on Land, Ice, and Sea Level. Yes.
Bentley:Oh, okay. So thatís, that explains what that refers to. That refers to this, which is related to the Seattle workshop.
Bentley:So, it must have been an ad hoc committee of the Polar Research Board? [Turning pages] Yeah. Thereís Dick Cameron. Tom Gross. Well, there were a lot of active participants, but I think we were the ones who were responsible for putting these together. Because this was during the time that I was chair either of PRB or the Committee on Glaciology. And Mark Meier, when I wasnít Glaciology chair, Mark Meier was, and heís always beenÖ I mean heís had a strong interest, and heís certainly one of the prime movers in studying sea level change in relation to glaciers.
Thomas:Whatís the relationship between these sets of workshops and, say, the organization of the Siple Coast Project? Is there any? Or is it a separate set of concerns?
Bentley:A little bit apples and oranges. I mean, the Siple Coast Project, the group that organized that were organizing the research itself, and talking about field programs, and whoís going to do what, and what are we going to do next year. And I used to meet annually with the Midwestern glaciology annual workshop, just as a venue of convenience, to plan the next couple of seasons. So, the people who participated in that were the PIs of the people who had field projects. Whereas this was a group of experts talking about what ought to be done, but not talking about their own research programs. So, the Siple Coast Project meetings we were very much talking about our own research programs.
Thomas:Right. So, letís talk about Siple Coast then, since it starts in Ď82, or so?
Bentley:I think it was Ď83 or Ď84 was the first season.
Thomas:Oh, okay, Ď83-í84?
Bentley:Well, you may be right. One of the things I know for sure, that I could very much rely upon, is that I cannot trust my memory. Iíve learned that over the years that no matter how vivid a memory I may have of something, thatís probably wrong, particularly when it comes to the date.
Thomas:Well, historians are really used to having to fact check against oral histories, and that sort of thing.
Bentley:Good. Good. Yes. [Laugh]
Thomas:Donít be concerned about leading us astray. Weíre professionals.
Bentley:All right. Okay. [Laugh] So, all right, in the early Ď80s, at any rate, we were ready to move on, and NSF was ready. I donít know whether itís any of these, or whether this is additional workshops, itís sort of in-between those two modes that I was just talking about a minute ago, but actually to plan what ought to be done as part of the developing West Antarctic Ice Sheet project. And then the first season we started on work around Crary Ice Rise. We worked around Crary Ice Rise for a while, and then moved up to upsteam B. When we started out it was just Bindschadler and [Ian] Whillans, and me. But then the list of participants grew, which was a great thing because we got people like Barclay Kamb, Bob Jacobel and his radar program. Letís see, who else joined as we went along? Keith Echelmeyer, Will Harrison from Alaska. I think those are the main players. And then since I havenít been involved anymore — this is not a cause and effect statement — Howard Conway, Charlie Raymond [of the University of Washington]. Well, Iím not sure whether Charlie actually — well, itís the same program at any rate. Anyway, the Washington people. And, of course itís not the Siple Coast Project anymore either. I think it was Julie Palais [who] decided that the Siple Coast Project had to end. Even though the work wasnít ending they had to terminate the name Siple Coast Project and call it something else, for NSF and internal reasons.
Thomas:Yeah. Bob Bindschadler was telling me about that. I could look it up in my notes.
Bentley:[Laughs] Yeah. It was, it was just window dressing, you know, to change the name. But, I donít even remember what it was changed to. Iím sure Bob would have told you that. So the Siple Coast Project, or whatever it was called after that, continued from Ď82 or Ď83, whichever it was, onto — as far as I was concerned, my last season was I think Ď94 or í95 — but, it reached the point where — what turned me off was we werenít allowed to do our radar sounding the way we used to, where we weíd go into the field with all our geophysical equipment with a plan for what we wanted to do, and then, as we started to find out things, weíd change our plans and do something, follow what the earth was telling us, so to speak, as the geologists say. But, the NSF put a lot of money into a remote sensing airplane and decided it had to be used. So, at that point, as far as the radar sounding went, we could no longer do anything according to what we found. We had to lay out a track plan ahead of time, then let somebody else go and do all the flying and data collecting on that track plan with no deviations from it, and no opportunity to change anything according to what we learned in the process. And then get the data back. I mean it was like a turnkey oil deal. It took the interest out of it for me. To me thatís not the way to do a geophysical field program. Although thatís the only way you could do things when it comes to the satellite operations. So, I had to get used to doing that when I started doing satellite radar altimetry. And it caused a lot of headaches, that mode; even though it was the only way you could do it. With the radar altimetry, every year or so theyíd come up with a new error theyíd found, and they had to recalculate everything. And I didnít have any control over data quality. I grew up in an era, and spent my entire Professional career, where you go in the field and, once you got there with your equipment, then you could follow your nose. I used to do that. Ewing used to do that, too, way back in the marine geophysics days. He had an idea of what he wanted to do, but if he found something new and interesting, then heíd go and work on that, follow that lead. So then I kind of ran out of graduate students at the same time. The last field program on the ground was my last graduate student. So, it all sort of came together, and I retired in 1998. And so I havenít really had much to do with anything thatís happened since as far as field work goes.
Thomas:Right. Well, itís just interesting how you mentioned that, because Bob Thomas, I had talked to him on the phone for about an hour when I was supposed to go up to Maine to meet them [Thomas and Hughes; Thomas was visiting Maine while living for a time in Europe], and that trip got canceled. He was saying how he had had a similar experience with just the research program becoming unwieldy and how heíd had better experience in recent years with the Chileans, who had provided a couple of aircraft that they could use more flexibly.
Bentley:Yeah. Was he talking about the PARCA program becoming rigidified?
Thomas:I donít remember specifically.
Bentley:The one with the Greenland laser altimeter flying?
Thomas:Yeah. I think it might have had something to do with that. That was back in February now, and I only took notes from that. I didnít record that one because I was on the phone.
Bentley:Bob and I wrote a paper together with Isabella Velicogna for UNEP [United Nations Environmental Program] on Ice Sheets and Sea Level Change. That was published last — when the hell was that? Oh, I donít know. Within the last year. We were on the same NASA science team for the Laser Altimeter Project for years. So, weíve gotten to be pretty good friends, starting from some rough spots. [Laughter]
Thomas:The days in RIGGS, calling out the airplanes before theyíre ready?
Bentley:Yeah. And, I thought he was — oh. Can I tell you something off the record?
Thomas:Yeah. Yeah. Sure. I was just asking about the West Virginia conference and kind of your perspective on the WAIS issue, versus say Terry Hughes, and you have very different perspectives, in particular at the West Virginia conference. You give a paper and then heís one of the respondents to it. And, that actually makes Michael Oppenheimerís 1998 review in Nature as [there] being kind of the two perspectives on it, although Hughes and Thomas had previously had differing perspectives as well. And so, Iím just wondering if you could tell meÖ
Bentley:Well, Hughes and Thomas both had a collapse perspective. And, I felt that the evidence just wasnít there for that. But thatís a difference in perspective. One of the differences, one of the things that always gave me a problem about some of these scare papers — thatís an exaggeration, but you know what I mean — was that I felt a lot of what they said was true, but they failed to put a time scale on it. So, they talk about how the ice sheet could disappear and raise sea level by six meters, but it makes a big difference whether that happens in a decade or 5,000 years. And, in some cases, I even suspected that that was left deliberately vague, just so it would be more effective in showing the need for research and NSF dollars. How you phrase things in ways that are attractive to people who are going to give you money, while not violating the truth, is part of academic gamesmanship, or grantsmanship. I felt in some cases that theyíd gone a little bit over the line.
Thomas:Iíve noticed that phrasing is very important to you. In particular I was reading your review of Denton and Hughesí Last Great Ice Sheets, and you were very careful to say that while thereís a lot thatís of interest in there, that they werenít careful to state what was speculative versus what was clearly certain. And so, Iím wondering if that was a more general response you had towards —?
Bentley:Well, yeah. It was something that particularly struck me in that book. YeahÖI thought that Terry and George took their models too seriously.
Thomas:Mhmm. Well, thatís another thing thatÖ
Bentley:They got too far towards the promotional attitude rather than a skeptical scientific attitude, it seemed to me. And, in that case it wasnít so much a matter of the time scale, I donít think.
Thomas:So much as it is just the register of certainty versus speculative, speculativeness?
Bentley:Yeah. The time scale thing came a little bit later when there were — I think this is one of the things I had some differences with Bob Bindschadler about, which, when we got right down to it and said, ďWhat do we each really believe?Ē it turned out that we were we were pretty much in agreement, and then we wrote that Scientific American article. Have you encountered that?
Thomas:ďOn Thin IceĒ?
Bentley:Yeah. Thatís right. I think thatís what itís called.
Thomas:I have a copy of that somewhere in here too.
Bentley:And really our differences were all over a matter of time scale. What I was saying was that itís not going to happen in the next century or two. And what he was saying was that itís going to happen in the next 5,000 years or so, probably. And he didnít really have an argument with what I was saying, and I didnít have an argument with what he was saying. But, I think we recognized that better than perhaps the perception elsewhere. I tried to make it clear that I was talking about the short time scale, in what I published, and I had a feeling that Bob, and maybe others, were less careful to make it clear what time scale they were talking about. Well, it would probably have been a bit of a misperception. I think it some way came from the mindset that I saw in that SeaRISE subtitle.
Thomas:Right. The 1990 SeaRISE workshop, which later became the WAIS Initiative?
Thomas:Yeah, I guess my perspective on it is looking at just some of the initial exchanges. Hughes was quite vague about it, and then Thomas is the first one who comes out with a number on time scale and says, ďIt couldnít possibly be shorter than 400 years, for the following reasons.Ē And so, whereas Hughes had taken, I think, a bit more of, ďThis could happen very, very quickly,Ē I saw Thomas as being a bit more of a skeptic in that respect.
Thomas:But, it seems to me, and from other things that Iíve heard, that Thomas actually fits more on — I mean, if thereís a spectrum of positions, that you would be among the more conservative, if you will, skeptical positions. Thomas would be somewhere over here, and then everyone seems to agree that Hughes is more on the, you know, ďThis is going to happen. I want to find a mechanism to [Ö] explain itĒ?
Bentley:Yeah, Bob was pretty much on the [laughs] on the collapse side. When we did this Det Norske Veritas exercise, he had the most rapid disappearance of the ice, but Terry wasnít part of that. [Laughter] Yeah, he and I probably emphasized different aspects, but I donít see him as one whoís distorting anything, which is one reason that itís interesting that we wrote this paper together on whatís likely to happen to Greenland and Antarctica, at least that was part of it, ďIce Sheets and Sea LevelĒ for this UNEP publication. Because we didnít have any trouble writing the paper together.
Thomas:Right. How about as the science changes, like in the mid-1980s you found out about the bed beneath the ice streams, for example? You said you announced that at that Utrecht conference?
Thomas:Did you see those kinds of results as altering your views on things at all, or was it just sort of a more scientific result? One of the conversations I was having with Doug MacAyeal yesterday was seeing science as a means to say something about whatís going to happen to WAIS versus another perspective, which is seeing the WAIS problems as an excuse to do science. And so, Iím wondering if you have a perspective on how your own views may or may not have changed as more became known about the dynamics.
Bentley:Well, in a way a little distressing aspect of whatís been going on with the West Antarctic — not really distressing, annoying is a better word — is that we keep learning more and more. Weíve learned a hell of a lot about the ice streams and the ice and how it all behaves, and now thereís these damn subglacial lakes going up and down. And, I donít see that weíve gotten very far towards understanding whatís going to happen to the ice. I donít think we know an awful lot more now, in terms of predictability, than we knew back twenty years ago or twenty-five years ago, when we got started. From just a pure glaciology standpoint, itís been great. Itís been all tremendously interesting, and a lot of surprising results, and weíre in a much better position to put real physics in on modeling the ice sheet than before. But, thereís still, still not enough to be able to do a particularly good job. I mean, it seems like the more advances we make the farther away the goal gets. Because, I think what the problem is that the more we learn about the ice sheet, the more complicated it gets, and the more complicated the controls on its movement gets. And the more complicated the situation, the harder it is to come up with a realistic model. So, we really were much farther away from the useful model back twenty-five years ago than we thought we were. Thatís what we really learned. I mean, obviously, weíve gotten a lot closer, because we learned a lot. But we havenít gotten a lot closer in terms of feeling that weíre just around the corner from being able to have a realistic model that everybodyíll believe, and thatíll be useful for making predictions. Theyíre not there yet.
Thomas:Have you been involved with the IPCC process at all?
Bentley:Only in reviewing chapters when they were up for general review.
Thomas:Okay. Do you have any opinions on how the subject of West Antarctica has changed, in terms of the chapters on sea level rise? I know there were a lot of people who were angered in the first assessment or two that it was mostly just accumulation and melting that were included, because they were quantifiable versus the possibility of collapse. Which I think the probabilities of it which were the subject of that EPA conference and the Det Norske Veritas?
Bentley:That was all related to that problem of not being able to predict the ice sheets were going to do. What was the question?
Thomas:I guess, do you have any opinions on the proper way to handle those uncertainties?
Bentley:Oh, the IPCC, how they handle it? WellÖ [phone ringing]
Bentley:Is that you?
Thomas:Yeah. It is. But, donít worry about it.
Bentley:Oh, okay. Yeah. I had some sympathy with theirÖ
Thomas:Oh, sorry. Itís my grandmother. I better take it.
Thomas:Hey. Okay. Weíre back once again. So, we were talking about your opinions of the IPCC?
Bentley:So, I was saying, I had some sympathy with what they did because, but not total sympathy. I thought they couldnít change their estimates based on what was known — particularly on the first two reports — what was known about the ice sheets, how fast they might cause sea level rise, because there wasnít enough known. And I think that they were correct in not trying to make a prediction based on an unpredictable situation. But where I faulted them was a tendency I thought, then, to sweep it under the table instead of emphasizing that this was a big question mark, and that it affects all the results. And in the latest one Bob Thomas and I, in this review article for UNEP that I was talking about, I actually talk about that we think that theyíve been too conservative in failing to recognize the potential for sea level change that is real, even though itís not certain, and that should have made more of it. But I donít envy them, having to write that. [Laugh]
Thomas:Let me just ask, while itís in my mind: a lot of the people Iíve talked to have been especially impressed by the collapse of the Larsen Ice Shelves as being something that has sort of startled them into rethinking their views on the WAIS situation. I was wondering if you had similar thoughts, or not?
Bentley:Well, the most startling thing to me about the collapse was just the fact that it happened so fast, and I had no idea that a big ice shelf could collapse that fast. But itís still just an ice shelf. Now, the glaciers behind have accelerated, but I think I have seen recently that they are slowing down again, as though they just reached a new equilibrium shape. Itís not necessarily proof that if you took out the Ross Ice Shelf that the West Antarctic Ice Sheet would suddenly accelerate into the ocean. So, I am swinging myself towards more and more belief in something drastic likely to happen. I mean, Iím less, less of a conservative now than I was when I was writing. I mean now I think things could maybe happen faster than I thought they would be able to some years ago. But, I still have probably a bit of a, I think, to some extent a wait and see — We still need to know more quantitatively whatís going to happen, because my experience, just generally speaking, is that thereís a constant seesaw. What we think about a particular situation goes one way, and then we have an extreme event like the Larsen break off, or the breakup and then the glaciers behind it accelerate, and you think, ďUh oh, this is terrible. It means that the cork is out of the bottle, and thereís going to be a collapse.Ē And then we find some contrary information thatĖ Oh, no, I know what Iím thinking of: the really rapid acceleration of Helheim Glacier — Helheim Glacier in Greenland — and then it slowed down again. So, I think weíre still operating on too short a time scale to be able to make meaningful predictions for whatís going to happen. We still havenít been observing these beasts long enough and, as I was saying a short time ago, we donít have good enough models to be able to extrapolate into the future based on this insufficient time of observation. However, that doesnít mean that I believe that we shouldnít do anything. I agree with I think Michael Oppenheimerís point in his review article. Was that Nature or Science?
Thomas:Weíre talking about 1998?
Bentley:Was it that long ago?
Thomas:I think so.
Thomas:I have it right here. But, it is definitely...
Bentley:Yeah, we had some conversations about that.
Thomas:Well, I think itís 1998.
Bentley:I felt that he was piling too many ďIf this, then...Ē, too many ďifsĒ on top of each other. So, by the time you got to the pile of ďifsĒ, it was a very unlikely event. Now Iím coming around more to his way of thinking, then, from a practical standpoint, from a societal standpoint, we have to look more at the disaster that could happen rather than be convinced that itís a high-likelihood event. If itís a small-likelihood event, but itís very serious in its consequences, then we have to start doing something about it now. So thatís more his attitude, I think.
Thomas:Right. Let me ask about the anthropogenic climate change issue in the studies and assessments of WAIS. Because, of course, when the concern over it first started out, it was on just its innate instability. Terry Hughes, in accordance with the Wilson theory, thought it might trigger another ice age, which is one of the reasons why he wanted to draw attention to it. And then, in the 1980s, of course, there are all these CO2 conferences. But, to what extent were its innate behaviors still kind of the main focus, versus what might happen on account of, say, the sea water melting the Ross Ice Shelf, causing the ice streams to become unbuttressed?
Bentley:Itís still not clear. I mean, I still think the only effective way of influencing the ice shelf, particularly in the Antarctic — not so much Greenland where you could have a serious effect on the surface — but youíre going to have to have quite a lot of warming before youíre going to have any serious melting on the surface. Except in places like the Larsen Ice Shelf where you can break up an ice shelf. So, either by melting from below from warmer ocean currents, or melting from above by warmer surface temperatures, I think ice shelves may be vulnerable. On the other hand, I think whatís going on in Pine Island Bay and the Thwaites and Pine Island Glaciers and Smith Glacier, all of that group, is almost purely natural. Itís just doing whatever it decided to do at the end of the last ice age. Because, I donít see that thereís a significant influence from that little ice shelf in front of Pine Island Glacier. I donít think has a significant influence. And Thwaites doesnít have any ice shelf at all. And, I guess, they may be responding to the disappearance of an ice shelf some centuries ago in Pine Island Bay, but then thatís not an anthropogenic effect. So thatís just one aspect of the natural effect.
Thomas:Was it ever settled, I guess, as to whether or not there was any sort of equilibrium with the Ross Ice Shelf coming off of the last ice age, or glacial?
Bentley:Well, I think the answer is no. Weíve seen significant changes in terms of what might have been thought to have been retreat along the grounding line on the east side of the Ross Ice Shelf with the slowdown of Whillans Ice Stream, which is no longer even out of balance, where it was fifty percent out of balance when we first made an estimate of it back in the early — well, mid Ď80s I guess maybe. So, that area doesnít even appear to be particularly at risk anymore. The main focus is on the Amundsen Sea Basin, with good reason. But, as I say, I donít think thatís particularly due to anthropogenic effects. Greenland is a little different because it can have significant increase in surface melting. And, the surface melt can leak down to the bed, a la Jay Zwally, and lubricate the bed and cause the ice to speed up. And now the latest thing there — this is another case of a pendulum — is now theyíre saying, ďWell, it only speeds up seasonally, and itís not destabilizing the ice sheet, when, if you look over a longer time period, you see in the winter time it just slows down again.Ē So, itís not a destabilization of the ice sheet. So, I donít think Iím going to live long enough, Iím sorry to say, to see predictability for the Greenland and Antarctic ice sheets.
Thomas:Mhmm. Do we want to break off until tomorrow then, when we might, I guess, pick back up on the career track?
Bentley:I think Iím about ready.
Yeah. I think thatís about right. Weíve actually gone quite a ways today. So, weíll stop right here.
Session I | Session II