More evidence of Antarctic melting reported.

Scientists have released the most compelling evidence yet that certain glaciers in Antarctica are melting rapidly. In April, researchers with the British Antarctic Survey (BAS) and the U.S. Geological Survey reported that 87 percent of 244 marine glaciers they surveyed on the Antarctic Peninsula have retreated markedly in the last 50 years.

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The three-year effort, reported in Science magazine, is the most comprehensive study to date of ice loss on the peninsula, a narrow chain of mountains stretching towards South America. To assess glacial trends, the researchers analyzed more than 2,000 aerial and satellite photographs dating back to the 1940s. The study suggests that marine glaciers are retreating by about 50 meters a year, although one (the Widdowson Glacier) has lost more than a kilometer of ice annually in the past five years. The loss is relatively new, scientists say, as most of the glaciers were growing as recently as 50 years ago.

The researchers also report accelerated loss of the large floating ice shelves along the peninsula's eastern side. Although this melting does not affect sea levels because the shelves already displace water, enhanced flow from glaciers further inland--many of which were held back by the crumbling shelves--can contribute to sea level rise. Loss of all ice on the Antarctic Peninsula would raise oceans by an estimated 0.3 meters.

Scientists suspect the enhanced melting is linked to human-influenced climate change. Air temperatures in the region have risen by more than 2 degrees Celsius in 50 years, one of the fastest warming rates in the world. But they also say topography, wind and precipitation patterns, and changing ocean conditions could play a role.

If the retreat continues, the Antarctic Peninsula may eventually look like the Alps, with glaciers reaching only partway down their valleys and failing to reach the sea, says BAS glaciologist David Vaughan.

Other parts of Antarctica have seen signs of melting as well. Scientists report accelerated glacial drainage from the massive West Antarctic Ice Sheet, which contains enough ice to raise sea levels seven meters. In all, Antarctica is home to more than 90 percent of the world's ice.