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Antarctic ice loss accelerating

Glaciers in Antarctica are thinning faster than they did in the 1990s and researchers have discovered an unexpected folded section deep beneath the ice cap, findings that may indicate the ice is less stable than had been thought.

Glaciers in west Antarctica are discharging 60 percent more ice into the sea than they are accumulating from snowfall, a research team led by Robert Thomas at NASA Goddard Space Flight Center in Wallops Island, Va., reported in Thursday's issue of the journal Science.

The glaciers flowing into the Amundsen Sea are thinning twice as fast as they did in the 1990s, the researchers said, a rate of loss that could raise sea level by 0.2 millimeters per year. That's a rate equal to previous estimates for all Antarctic melting, the team said.

Global sea level rise has been estimated at 1.8 millimeter per year. There are about 25 millimeters in an inch.

A second paper in the same issue of Science disclosed an unexpected fold in the ice deep inside the Antarctic ice cap.

The fold, located some 2,600 feet below the surface, may indicate a change in the speed and direction of movement of the ice several centuries ago, said the research team from England's Bristol University and the British Antarctic Survey.

The discovery suggests that the whole ice sheet is more susceptible to future change than previously thought, they reported.

Change in the west Antarctic ice sheet has been limited to its edges, but the group led by Martin Siegert of Bristol University said the fold indicates that several centuries ago this ice sheet was moving more rapidly and in a different direction than currently. Such changes, the group said, imply that the center of the ice sheet is more mobile than had been thought.

They used ice-penetrating radar to locate the fold deep below the surface.

In a separate report in the journal Geophysical Research Letters, scientists disclosed that glaciers that had been blocked behind an ice shelf have started flowing more rapidly into the Weddell Sea, following the breakup of that shelf.

The Larsen B ice shelf on the Antarctic Peninsula collapsed in 2002, and researchers said nearby glaciers began flowing up to eight times faster than they did prior to the breakup.

They said the speedup also caused glacier elevations to drop, lowering them by up to 125 feet in six months.