A comprehensive study of Antarctica’s ice confirms that the polar cap is shrinking. In 2006 alone, Antarctica lost nearly 200 billion tonnes of ice, researchers say — the equivalent of a global sea level rise of more than half a millimetre. That’s 75% more than losses in 1996, they add.
The study follows on a 2006 report that also concluded the rate of ice loss from glaciers melting and sliding away is greater than the gain from snow (see “Antarctica is shrinking”). That report concluded that from 2002 to 2005, Antarctica lost an average of 152 cubic kilometres (139 billion tonnes) a year.
“It reinforces the finding that the Antarctic is losing mass — which is still not a well-accepted result,” says Eric Rignot, an ice sheet expert at the University of California at Irvine and head of the team that reports the new result today in Nature Geoscience 1. “Doing it with an independent technique is very important,” he adds. Both groups used satellite data, but based on different techniques.
Andrew Shepherd, who studies global ice sheet dynamics at the University of Edinburgh in Scotland, says Rignot’s findings are in good agreement with his2 and other recent studies. He says the net losses in ice mass are very similar to losses he has calculated for Greenland (see “Glacial pace picks up”).
Isabella Velicogna, now a colleague of Rignot’s at Irvine, led the 2006 work that also showed Antarctic ice loss. Her study was based on gravity measurements and had more data points, but over a shorter time period. She says her and Rignot’s results are in good agreement. “We’re both seeing a trend that is significant.”
The IPCC report (which is proving to be too conservative) did not suggest that Antarctic melting was imminent. But it’s happening. Rignot:
“Each time I look at some new data, I am astonished.”