An observed negative trend in West Antarctic accumulation rates from 1975 to 2010: Evidence from new observed and simulated records



[1] Observations of snow accumulation rates from five new firn cores show a negative trend that is statistically significant over the past several decades across the central West Antarctic ice sheet (WAIS). A negative temporal trend in accumulation rates is unexpected in light of rising surface temperatures as well as model simulations predicting higher accumulation rates for the region. Both the magnitude of the mean accumulation rates and the range of interannual variability observed in the new records compare favorably to older records collected from a broad area of the WAIS, suggesting that the new data may serve as a regional proxy for recent temporal trends in West Antarctic accumulation rates. The observed negative trend in accumulation is likely the result of a shift in low-pressure systems over the Amundsen Sea region, dominated by changes in the austral fall season. Regional-scale climate models and reanalysis data do not capture the negative trend in accumulation rate observed in these firn cores. Nevertheless the models and reanalyses agree well in both accumulation-rate means and interannual variability, with no single model or dataset standing out as significantly more skilled at capturing the observed magnitude of and trend in accumulation rates in this region of the WAIS.