Antarctica's ice shelves melting from the bottom up

Many of Antarctica's ice shelves are melting away from the bottom up, research by a glacial expert at the University of California, Irvine, indicates. A study published Wednesday in Science found that about 55 percent of the mass lost from ice shelves in Antarctica is through melting at the ice-ocean boundary, National Geographic reported. "This places more importance on the role of the ocean," said study leader Eric Rignot, a glacier expert with a joint appointment at the University of California, Irvine, and the Jet Propulsion Laboratory in Pasadena, Calif. "If the ocean melts these ice shelves, it will affect the ice sheets on land." Ice shelves act like plugs in a bottle, Rignot said, because they regulate the flow of ice from the glacier into the ocean. The results could have implications for how Antarctica changes because of global warming, National Geographic said. Using data from satellite observations, radar and computer models, Rignot and his colleagues measured ice shelf thickness and speed, and the net input of snowfall onto shelf surfaces from 2007 to 2008. The data suggested 48 percent of the water lost came from smaller ice shelves on the southeastern Pacific side of Antarctica. "Continued warming of the ocean will slowly increase ice shelf thinning," the study's authors said. The big shelves, which account for 61 percent of the ice shelf cover in the Antarctic, contributed only about 15 percent of the meltwater in the analysis. Rignot said the reason for the disproportionate loss from the smaller shelves is because they sit on relatively warmer water than the bigger shelves.