Mass Balance and Accumulation Rate Along US ITASE Routes

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This award provides support for five years of funding to determine the mass balance and accumulation rate of ice along the traverse routes of the U.S. International Trans-Antarctic Scientific Expedition (US ITASE) program. The rate of ice sheet thickening or thinning will be measured along flow lines, along ice divides and along elevation contours in West Antarctica using a method which measures the vertical velocities of markers buried in subsurface ice. This method uses the Global Positioning System (GPS) and surveying techniques to determine the precise location of these markers. Vertical velocities so obtained are compared with long-term rates of snow accumulation and the difference in the two is a measure of ice sheet thickness change. A series of recording instruments will be installed to provide continuous records of firn densification and snow surface elevation change. These instruments will be deployed at selected sites to link transient changes in snow surface elevation, as measured by altimeters, to long-term rates of ice thickness change. Ice motion at drill sites, upglacier topography and upglacier gradients in accumulation rate will be measured and used to calculate ice flow-induced accumulation rate variations and remove them from the ice core records. This work will provide the capability to deduce true past climatic variations in accumulation rate from the US ITASE ice core records.