Ice Loss from the West Antarctic Ice Sheet Slower than Previously Estimated
21.10.2009 - Logistics, Land & Geology, Ice & Snow, Other, Antarctic
Results of improved ground measurements in West Antarctics were recently published in the online journal Geochemistry, Geophysics, Geosystems of the American Geophysical Union and the American Geochemical Society. The measurements, made in the framework of theWest Antarctic GPS Network (WAGN) project, showed that the rate of ice loss of the West Antarctic Ice Sheet might have been overestimated in previous studies.
In 2006, researchers used data from the Gravity Recovery and Climate Experiment (GRACE) satellites and form this inferred that a significant loss of ice took place in West Antarctica between 2002 and 2005. However the GRACE measurements did not measure the ice loss directly, but rather changes in gravity, which can be caused by both ice loss and vertical uplift of the bedrock underneath the ice.
The new study has measured for the first time the vertical motion of the bedrock using a network of 18 Global Positioning System (GPS) stations. These measurements, based on accurate three-dimensional locations of each station, were taken twice, once between 2001 and 2003, and once between 2004 and 2006. From this the researchers were able to determine the postglacial rebound, a phenomenon which causes an increase in the gravitational attraction measured by the GRACE satellites and could explain why they inferred rapid ice loss was occurring in West Antarctica. The new GPS measurements show West Antarctica is rebounding more slowly than once thought, meaning that the correction to the gravity signal from the contribution of the rock had been overestimated and that West Antarctica is losing ice more slowly than previously thought.
Although the magnitude of the miscalculation has not so far been determined exactly, the new results provide precise GPS observations of the continent's actual rebound. Further corrections will be made by other researchers specialized in interpreting GRACE results and will be supplemented with additional data from the first year of the Polar Earth Observing Network (POLENET) project.
