Western Antarctic Losing More Ice

The Earth's northern polar region isn't the only area to see shrinking ice cover in recent years. Scientists using satellite data and computer modeling now estimate that Western Antarctica is losing increasing amounts of ice as well.

Jonathan Bamber, a professor at the University of Bristol in the U.K., is among several researchers who recently discovered that ice loss in western Antarctica accelerated by about 75 percent between 1996 and 2006. The team made that estimate by first analyzing satellite data covering most of the icy continent's coastline, then by comparing those findings with computer models showing what snow accumulation in the region should have been over the 10-year time frame being studied.

Compared to the expected ice cover from climate models, West Antarctica lost about 132 billion tons of ice in 2006. That region's ice loss was 83 billion tons in 1996. The remainder of the Antarctic Peninsula also lost more ice in 2006 -- about 60 billion tons -- while ice in East Antarctica has remained unchanged.

Bamber and his fellow researchers say their study indicates the factors affecting ice cover in Antarctica is more complex than previous climate models have assumed. Computer simulations of global warming have suggested that the continent's ice sheet would actually expand as the climate warmed and snowfall increased. However, these latest estimates might mean that ice loss from increased glacier flow might have a greater impact on Antarctica's ice cover than greater snow accumulation.

The regions where Antarctic ice loss is most pronounced is in areas with narrow glacier outlets, where the flow of ice into the sea appears to be accelerating. However, while such conditions haven't been observed in East Antarctica, that part of the continent could also see rapid change in the near future if its ice cover over water continues to thin.

Bamber said the level of ice loss is notable, simply because of the huge volumes involved.

"To put these figures into perspective, four billion tons of ice is enough to provide drinking water for the whole of the U.K. population for one year," he said.

The signs of climate change have been most pronounced at the Earth's poles. Last October, the National Snow and Ice Data Center reported that Arctic sea ice reached historic all-time lows in the summer of 2007. By the summer's end, the extent of ice there had shrunk to 1.65 million square miles, compared to a 1979-2000 summer average of 2.70 million square miles. Researchers have also found dramatically higher-than-average temperatures in Earth's polar regions, both on land and in water.

Scientists warn that such changes, if they continue, could reach a tipping point at which global warming becomes irreversible and accelerates as more climate feedback loops come into play.