WASHINGTON — Two sections of Antarctica’s Larsen ice shelf have collapsed over the past decade and another portion could be headed for the same fate as warming ocean waters undermine the ice, researchers say.

CURRENTS OF WATER deep beneath the surface are melting the floating ice shelf from below, said Andrew Shepherd of the University of Cambridge in England.

Large sections of the shelf collapsed and broke into icebergs in 1995 and 2002, and the major section could be weak enough to fail within a century, a research team led by Shepherd reports in Friday’s issue of the journal Science.

Changes in the surface level of the ice shelf, which rests along the Antarctic Peninsula extending toward South America, were studied using nine years of measurements from the European Remote Sensing satellite.

Between 1992 and 2001 the surface level of a 12,000-square-mile (31,000-square-kilometer) region of the shelf lowered between 3 inches and 6.6 inches (7.5 to 16.7 centimeters) per year, they found, with the decline more pronounced at the northern end of the shelf.

It was in the northern part…

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