Interannual variations of snow accumulation on the Greenland Ice Sheet (1985-1996): new observations versus model predictions

Newly measured time series of net water-equivalent accumulation from ice cores are reported for 11 sites located near the 2000-m contour of the Greenland Ice Sheet. Many of these sites are located in regions where accumulation has not been previously measured. We compared these nem; time series of annual accumulation with previously reported modeled precipitation covering the same time range, Because ice core accumulation records include both regional and local accumulation components, we used adjacent ice core records at six multiple-core sites to estimate the local component and extrapolated these results to the five single-core sites. We investigated the impact of this short-scale spatial variability in accumulation on statistical comparisons between the observed accumulation and model precipitation. Although scalers were required to match the similar to 12-year mean modeled precipitation to the mean observed accumulation, a high degree of correspondence between observed interannual accumulation and scaled modeled precipitation was found at 7 of 11 locations. The need for scaling and the low correspondence between model simulations and observations at some sites clearly indicate that model improvements are needed. Although very encouraging, a more spatially distributed array of ice core accumulation measurements, spanning the same time period as the precipitation modeling, is necessary for continued model improvement and validation. In agreement with earlier studies, the large temporal variability in snow accumulation predicted by modeling and confirmed by ice cores indicates that the ice sheet elevation varies by tens of centimeters from year to year simply because of changing accumulation.