West Antarctic ice sheet may not be losing ice as fast as once believed

Washington, October 20 (ANI): New ground measurements made by the West Antarctic GPS Network (WAGN) project has suggested that the rate of ice loss of the West Antarctic ice sheet has been slightly overestimated, and it may not be losing ice as fast as once thought.

"Our work suggests that while West Antarctica is still losing significant amounts of ice, the loss appears to be slightly slower than some recent estimates," said Ian Dalziel, lead principal investigator for WAGN.

"So, the take home message is that Antarctica is contributing to rising sea levels. It is the rate that is unclear," he added.

In 2006, another team of researchers used data from the Gravity Recovery and Climate Experiment (GRACE) satellites to infer a significant loss of ice mass over West Antarctica from 2002 to 2005.

The GRACE satellites do not measure changes in ice loss directly, but measure changes in gravity, which can be caused both by ice loss and vertical uplift of the bedrock underlying the ice.

Now, for the first time, researchers have directly measured the vertical motion of the bedrock at sites across West Antarctica using the Global Positioning System (GPS).

The results should lead to more accurate estimates of ice mass loss.

As the ice mass decreases, the bedrock immediately below the ice rises, an uplift known as postglacial rebound.

Postglacial rebound causes an increase in the gravitational attraction measured by the GRACE satellites and could explain their inferred measurements of recent, rapid ice loss in West Antarctica.

The new GPS measurements show West Antarctica is rebounding more slowly than once thought.

This means that the correction to the gravity signal from the rock contribution has been overestimated and the rate of ice loss is slower than previously interpreted.

"The published results are very important because they provide precise, ground-truth GPS observations of the actual rebound of the continent due to the loss of ice mass detected by the GRACE satellite gravity measurements over West Antarctica," said Vladimir Papitashvili, acting director for the Antarctic Earth Sciences Program at the National Science Foundation, which supported the research.

WAGN researchers do not yet know how large the overestimation was. Other researchers who specialize in interpreting GRACE data will conduct a more definitive correction. (ANI)