| Summary: | Our proposed research has three primary objectives. The first is to develop estimates of the temporal and spatial patterns of accumulation on the Greenland ice sheet, with particular emphasis on recent decades and areas with high uncertainty. We will do this using ice-core measurements and coastal precipitation data, plus collaborative research in precipitation modeling, ice-penetrating radar, and space-based gravity measurements. The second objective is to determine the time history of large-scale changes in atmospheric circulation and the impact on accumulation variability over southern Greenland. For this we will use multi-century ice-core records of elemental and isotopic tracers, along with traditional trace chemistry and accumulation measurements, at sub-annual to annual time scales. The third objective is to define the influence of snow-accumulation variability on ice-sheet elevation change and on estimates of ice-sheet mass balance, and to develop a modeling approach to remove the effect of short-term variability of accumulation on ice-sheet elevation changes measured by altimetry. While many of the raw data needed to address these objectives were developed in the 1995 to 2001 time period, a small amount of additional fieldwork will be required. We propose to collect 6-10 shallow (20-30 m) and 3 intermediate (~150 m) ice cores in southern and central Greenland. We will use a newly developed CFA-TE (continuous flow analysis – trace elements) laboratory technique to develop high-resolution, multi-
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