A 75-square-mile chunk of ice shelf on the Antarctic Peninsula snapped off sometime earlier this year, scientists said Friday. They blamed global warming.

Satellite images of the Larsen B ice shelf, which reaches toward South America, show the section broke away between Feb. 26 and March 23 as the Antarctic summer turned to winter, according to the U.S. National Snow and Ice Data Center in Boulder, Colo.In January 1995, the Larsen A ice shelf to the north broke away.

The British Antarctic Survey predicts the entire Larsen Ice Shelf, which covers over 4,000 square miles, is near its limit of stability.

The ice shelf collapse is consistent with "what we see from the effects of increased greenhouse gases, which cause warming," said Bill Budd, a meteorology professor at Australia's Antarctic Cooperative Research Center.

"And it's the warming in the ocean that is most important for the reduction in the ice shelves," he said. "It is the melting from underneath that can be much more effective than warming of the air."

Over the past 50 years, the Antarctic Peninsula has experienced a sustained atmospheric warming of 4.5 degrees.

Research by Budd and his colleagues indicates global warming will melt most of the ice shelves, which border about 44 percent of Antarctica and cover 580,000 square miles.

Budd's computer climate models predict significant degradation of the ice shelves beginning in the 21st century and their near-total loss within 500 years.