Research Objectives:
The polar ice sheets and the snow falling on them are important components of the global hydrological cycle. Yet, because of their very large size and remote locations, scientists have only a limited understanding of their mass balance (rate of thickness change) or the spatial distribution of snow accumulation. Work conducted as part of the U.S. ITASE seeks to improve this understanding.
This five-year project is beginning its fourth year in the 2002-2003 field season. Researchers will measure the rate of ice sheet thickening (or thinning) at selected sites along flow lines, on ice divides, and along elevation contours. The vertical velocity of ice is obtained from precise GPS surveys of markers buried 5-20 meters deep in the surface firn. The velocity measurements are compared with the local, long-term average snow accumulation rate evident in ice core stratigraphy. Earlier work demonstrates that very precise rates of thickness change can be measured using this technique.
This group is also studying spatial variations in accumulation rates, probing the link between snow accumulation and surface topography. Continuously operating, autonomous instruments will be deployed at several closely spaced sites that have very different slope gradients. The instruments will record snow accumulation, wind speed, and direction, firn compaction, and firn temperature. These results will enable this group to test hypotheses of the physical processes of snow deposition and erosion.
This project will also investigate the ice flow effects on accumulation rates derived from U.S. ITASE ice core records. At sites along flow lines, ice cores record the integrated accumulation rate history for a certain distance up-glacier of the core site. Changes in surface topography along this flow line will lead to apparent accumulation rate variations in the ice core record. By studying local ice dynamics (horizontal velocities, surface slope) around each ice core site, researchers will be able to better understand the cause of accumulation rate variations in the core records.
