The following is an excerpt from National Geographic.
Antarctica's ice shelves are losing it.
Conventional wisdom holds that ice shelves-the seaward extension of glaciers on land-lose most of their mass by shedding icebergs. But new research finds that there's another weight-loss program at work-many of Antarctica's ice shelves are melting away from the bottom up.
A bottom-up view of ice in the Antarctic as an emperor penguin shoots to the surface. Photograph by Paul Nicklen, National Geographic
Glacier experts have known for years that ice shelves melt at the boundary between the ice and the sea. But previous studies have only looked at individual glaciers and ice shelves in Greenland and Alaska, said Erin Pettit, a glacier expert at the University of Alaska in Fairbanks who was not involved in the new research.
A study published today in the journal Science has gone beyond those individual observations and found that about 55 percent of the mass lost from ice shelves in Antarctica is through melting at the ice-ocean boundary. (Learn more about The Big Thaw in National Geographic magazine.)