A new estimate puts maximum global sea level rise from the collapse of the West Antarctic Ice Sheet at 10.5 feet (3.2 meters)—not the 16 feet (five meters) or more predicted in the past.

The latest research indicates that this massive ice sheet is unlikely to disappear completely, limiting the damage as it melts. Glaciologist Jonathan Bamber of the University of Bristol in England and his colleagues modeled the collapse of the ice sheet based on the relative likelihood of a given section vanishing completely.

Their work suggests only those parts of the ice sheet that are grounded below sea level or sloping downwards would collapse. Those parts of the sheet grounded above sea level or on bedrock that slopes upwards would remain in place.

Ice cores drilled from the poles have provided valuable historical climate records, as the composition of the ice and the air bubbles trapped therein offers a relatively pristine glimpse of ancient conditions. Now a group of Japanese scientists says that the same technique may yield records of significant astronomical events as well.

In a paper posted recently to arxiv.org, Yuko Motizuki of the RIKEN Nishina Center for Accelerator-Based Science in Wako, Japan, and colleagues present evidence for an Antarctic ice-core record of supernovae, or stellar explosions, a millennium ago. A 400-foot (122-meter) core pulled up in 2001 at Dome Fuji station in East Antarctica shows spikes in the concentration of nitrate ion (NO₃^–) that coincide with two known supernovae in the 11th century: supernova 1006, named for the year it was observed, and the Crab Nebula supernova of 1054. (Astronomers and astrologers in the Far East and the Middle East were already making detailed records of such events by that time.) Nearby supernovae, the researchers write, shower Earth with gamma rays, which can boost levels of nitrogen oxides in the atmosphere that might be recorded as nitrate spikes in the ice.

Was the Antarctic once a balmier place? Researchers report in the British journal Proceedings of the Royal Society B that a fossil of a tiny crustacean offers proof that it had a relatively toasty clime as recently as 14 million years ago. The rocks in eastern Antarctica's Dry Valleys region yielded the fossil of an ostracod (seen at left)—a shrimp-like crustacean that lived in an ancient Antarctic lake seen at left. The tiny crustaceans need liquid water to survive—unavailable in today's Antarctic where temps average -13 degrees Fahrnenheit (-25 degrees Celsius), but possible eons ago when the climate there was more like Alaska's. The living relatives of the ancient critter don't get any closer to Antarctica than the surrounding seas, but the fossil indicates that the bone dry landscape, often compared to that of Mars, once was warm enough to have water. What it doesn't reveal is what caused the climate shift, a process that may be reversing itself at present.