Antarctica is Melting from the Bottom Up

As much as 90 percent of the ice loss in some parts of Antarctica happens beneath the water, according to researchers who report that much more ice is melting from the undersides of submerged ice shelves than previously thought.

Every year 2,800 cubic kilometers leave the Antarctic ice sheet, but for decades the general consensus among scientists was that calving -- where huge chunks of ice break off from glaciers and float out to sea -- was the main source of Antarctic ice loss.

Using satellite and climate modeling data, a team of scientists from three universities contend that the sub-shelf melting impacts ice levels in Antarctica have a large impact on overall ice loss just as much as iceberg calving, if not more.

How much ice specific shelves lose to melting versus calving varies dramatically, the researchers report, saying that as much as 90 percent of ice loss can be attributed to sub-shelf melting in some areas, while sub-shelf melting elsewhere on the continent only accounts for 10 percent of ice loss.

"Understanding how the largest ice mass on the planet loses ice to the oceans is one of the most fundamental things we need to know for Antarctica. Until recently, we assumed that most of the ice was lost through icebergs," said Jonathan Bamber from the University of Bristol's School of Geographical Sciences. Bamber conducted the study with researchers from University of California and Utrecht University

"Now we realize that melting underneath the ice shelves by the ocean is equally important and for some places, far more important," Bamber said. "This knowledge is crucial for understanding how the ice sheets interact now, and in the future, to changes in climate."

The research measured the flow of ice, its elevation and its thickness and combined that data with the output of a climate model for snowfall over the ice sheet. By comparing how much snow was falling on the surface and accumulating versus how much ice was leaving the continent, entering the ocean and calving, the scientists were able to determine the percentage of ice that was lost as a function of ice melt and calving.

The paper "Calving fluxes and basal melt rates of Antarctic ice shelves," is published in the journal Nature.