By Sid Perkins
Satellite images of Antarctica between 1992 and 2006 indicate that the continent was losing ice much faster at the end of that period than it was a decade before.
Snow that falls on Antarctica makes its way to the sea as ice via glaciers, some of which flow faster than others (SN: 3/31/07, p. 202). Using data gathered by Earth-orbiting crafts, Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and his colleagues determined the thickness of ice fringing the continent’s coast. That data, combined with the speed of the ice streams and estimates of the continent’s snowfall, allowed the team to estimate Antarctica’s ice loss each year.
East Antarctica, home to the largest of the continent’s ice sheets, is fairly stable, losing only about 4 billion metric tons of ice each year, says Rignot. However, data suggest that ice loss elsewhere has accelerated, the team reports in the February Nature Geoscience. On the Antarctic Peninsula, the glaciers that nourished the Larsen A and Larsen B ice shelves lost about 3 billion metric tons of ice in 1996 but 31 billion metric tons in 2006. (The Larsen A shelf disintegrated and floated away in 1995, as did the Larsen B shelf in 2002.)
In West Antarctica, the Pine Island Glacier’s acceleration rose 34 percent from 1996 to 2006. That river of ice, plus its neighbors, dumped 90 billion metric tons of icebergs into southern oceans in 2006, compared with 41 billion metric tons in 1996.
Overall, the team’s analyses suggest, Antarctica lost about 75 percent more ice in 2006 than it did in 1996.
