But the narrow peninsula contains relatively little inland ice. Glaciologists are more concerned that they are now beginning to detect similar signs closer to the South Pole, on the main body of the continent, where ice shelves are much larger — and could contribute far more to sea level changes. Of particular interest is this remote and almost inaccessible region known as "the weak underbelly of West Antarctica," where some individual ice shelves are as large as Texas or Spain and much of the land on which they rest lies under sea level.

"This is probably the most active part of Antarctica," said Eric Rignot, a glaciologist at the Jet Propulsion Laboratory in Pasadena, Calif., and the principal author of the Geophysical Research Letters paper. "Glaciers are changing rapidly and increasingly discharging into the ocean, which contributes to sea level rise in a more significant way than any other part of Antarctica."

According to another paper, published in the journal Science in September, "the catchment regions of Amundsen Sea glaciers contain enough ice to raise sea level by 1.3 meters," or about 4 feet. While the current sea level rise attributable to glacier thinning here is a relatively modest 0.2 millimeters a year, or about 10 percent of the total global increase, the paper noted that near the coast the process had accelerated and might continue to do so.

As a result, the most recent flights by NASA and the Chilean center have been directed over the Thurston Island and Pine Island zones of West Antarctica, near where the Bellinghausen and Amundsen seas come together. The idea is to use the laser and radar readings being gathered to establish a base line for comparison, with measurements to be taken every two years or so.

"We're not sure yet how to connect what we see on the peninsula with what we observe going on further south, but both are very clearly dramatic and dynamic events," Bindschadler said. "On the peninsula, large amounts of melt water are directly connected to disintegration of the ice shelf, but the actual mechanism in West Antarctica, whether melt water, a slippery hill or a firmer bedrock, is not yet clear. Hence the need for more data."

The information being gathered here coincides with the recent publication of a report on accelerating climate change in the Arctic, an area that has been far more scrutinized than Antarctica. That study, commissioned by the United States and seven other nations, found permafrost there to be thawing and glaciers and sea ice to be retreating markedly, raising new concerns about global warming and its impact.