May 9, 2012
Antarctic Ice Sheet May Begin Melting Rapidly By Century’s End
The finding, made by climate researchers of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, refute a widely believed theory that ice shelves in the Weddell Sea would not be affected by global warming due to the peripheral location of the sea.
"The Weddell Sea was not really on the screen because we all thought that unlike the Amundsen Sea its warm waters would not be able to reach the ice shelves. But we found a mechanism which drives warm water towards the coast with an enormous impact on the Fichner-Ronne Ice Shelf in the coming decades", Dr. Hartmut Hellmer, oceanographer at the Alfred Wegener Institute and lead author of the study, said in a press release.
The team used different model calculations to demonstrate the result that chain reaction large ice masses could slide into the ocean within the next six decades.
"Our models show that the warmer air will lead to the currently solid sea ice in the southern Weddell Sea becoming thinner and therefore more fragile and mobile in a few decades," Dr. Frank Kauker, a researcher on the project, said.
According to Hellmer, if this happens, a hydrographic front in the southern Weddell Sea will disappear, which is a front that has prevented warm water from getting under the ice shelf.
"According to our calculations, this protective barrier will disintegrate by the end of this century", Hellmer said.
JÃ¼rgen Determann, one of Hellmer's colleagues, said the scientists expect the greatest melting rates near the zone in which the ice shelf settles on the sea floor at the transition to the glacier.
Determann believes that by the turn of the next century, the melt rates will increase to about 164-feet per year.
He is currently looking into how the ice streams behind will react in the event of the ice shelf melting in these proportions.
"Ice shelves are like corks in the bottles for the ice streams behind them," Hellmer said. "They reduce the ice flow because they lodge in bays everywhere and rest on islands. If, however, the ice shelves melt from below, they become so thin that the dragging surfaces become smaller and the ice behind them starts to move."
According to the latest estimates, the global sea level rose for the period 2003-2010 at a rate of nearly 0.06-inches per year due to melting glaciers and ice shelves.
"If the high melting rates are completely compensated by inland ice flow, this loss in mass would correspond to an additional rise in global sea level of 4.4 millimeters (0.17-inches) per year", JÃ¼rgen said.
During the study, the scientists used the atmospheric projections of the British Met Office Hadley Center in Exeter for forcing data. They used information on the future development of the wind and of the temperature in Antarctica.
"We started the BRIOS model in 1860 to see whether its results also represent the current situation. We found that this condition was satisfied," Dr. Ralph Timmermann, another researcher on the project, said in the release. "For example, the water temperatures for the Weddell Sea predicted by BRIOS are close to those we have actually measured in the recent past."
He said the model has been verified, and correctly predicts sea ice thickness, concentration, and drift as well as circulation patterns. According to Timmermann, BRIOS only needs less than a week of data for a century's worth.