Antarctic ice shelves are melting from the bottom up, and this is the result of by warm oceans, according to new measurements published in the journal Science on June 13.
Watching film of icebergs breaking off the ice shelf in Antarctica is the most dramatic way of seeing the loss of ice there, but it is not the way most water there is lost, if this new research is confirmed.
The ice sheets of Antarctica are melting at an average of over 19 inches a year. But some parts of the ice sheet is melting much faster than that - up to 328 feet a year, although not every area is losing ice mass.
"These changes are faster and larger than anything people anticipated," Eric Rignot of the University of California, a study co-author and researcher, said.
Ice sheets form when snow falls on mountains and freezes into glaciers, which slowly travel downhill. When they meet the ocean, they flow evenly into the water, creating a flat surface.
As the ice shelf melts, glaciers can travel faster, which increases the flow of fresh water from land into the oceans, contributing to sea level rise. Over half - 55 percent - of the melting observed in Antarctica is taking place in just ten minor ice shelves. The researcher believes these shelves might act like a cork, preventing the loss of more land-locked water into the sea.
"This places more importance on the role of the ocean. If the ocean melts these ice shelves, it will affect the ice sheets on land," Rignot said.
The mass of ice sheets was calculated from measurements taken from satellites and aircraft between 2007 and 2008 in one of the most extensive research projects of its type ever undertaken. The climatologists then used computer models to calculate how much ice was lost through different methods. The research took almost ten years to complete, but is at a loss to explain exactly why the oceans around Antarctica are warming.
Antarctica is surrounded by constant winds that rotate clockwise around its landmass. With a slightly warmer atmosphere in the region, the winds have picked up in recent years, which may help drive warmer surface waters under the ice sheets.
About two-thirds of the Antarctic ice mass is located in the three largest sheets, yet they account for just 15 percent of the melting observed. Minor ice shelves on the southeastern Pacific side of Antarctica were responsible for 48 percent of the loss during those years.
