Physics Today Daily Edition
Wall Street Journal: Over the past six months, 95% of the northern section of Australia's Great Barrier Reef has been affected by coral bleaching. Bleaching occurs when ocean temperatures increase, killing the algae that inhabit coral and give the reefs their color. Without the algae, the coral starve and eventually die. The damage was assessed by an aerial survey, which is now examining the southern part of the reef. The bleaching event isn't localized to the Great Barrier Reef; it is the third global event since 1998. All have been tied to the occurrence of an El Niño system in the southern Pacific.
Guardian: During the winter of 2015–16, the average sea ice cover in the Arctic never exceeded 14.52 million km2, a record low winter maximum for the region. According to the US National Snow and Ice Data Center, March was the third straight month in which sea-ice levels reached a new low. Winter is usually the period when sea-ice extent increases, but unusually high temperatures in January and February significantly stunted its growth. Many Arctic researchers suggest that the record low increase in ice coverage could signal the beginning of an irreversible trend of continually shrinking sea ice. Recent summers have seen extreme lows in sea ice as well. Because dark water absorbs more solar energy than does bright white, snow-covered ice, the growing areas of open water have contributed to the increased temperatures year round. Within 20 to 25 years, it is likely the Arctic will be completely ice-free during summer months.
Space.com: On Thursday at the annual Lunar and Planetary Science Conference in The Woodlands, Texas, NASA's Cassini team announced that it had identified a 3337-m-high mountain on the surface of Titan, one of the moons of Saturn. Images from Cassini have revealed a number of 3000-m-plus mountains on the moon, mostly in equatorial regions, but the team believes this mountain will prove to be the tallest. The presence of such tall mountains suggests that the moon is tectonically active. That activity could be caused by the pull of Saturn's gravity, the cooling of Titan's crust, or variations in the moon's rotation.
Science News: Accurately predicting cloud formation is a difficult but important element of climate models. According to Kevin Wilson of Lawrence Berkeley National Laboratory and his colleagues, the current models have not been completely successful. Water droplets form when water vapor condenses onto airborne particulate matter called aerosols. Current models assume that water-soluble molecules alter the chemistry of the droplets, which allows them to grow larger. Wilson's team tested that idea by filling a large tube with humid air and organic aerosols. Using lasers to measure the size of the water droplets that formed, the researchers found that the resulting droplets were 40% to 60% larger than expected if the organic molecules were simply dissolving. The scientists believe that a different mechanism is at work: Instead of dissolving, the organic molecules coat the exterior of the droplet, which lowers the surface tension of the water and makes it easier for additional water to condense and join the droplet.