Snowfall in coastal West Antarctica much greater than previously assumed

Abstract

A new Antarctic accumulation distribution, based on regional model output calibrated with 1900 in-situ observations, is used to re-assess accumulation in 24 Antarctic ice drainage basins. When compared to the previous compilation, good agreement is found for 19 of the 24 basins, representing 93% of the ice sheet that is reasonably well covered with observations. In contrast, the Amundsen Sea sector of West Antarctica and the western Antarctic Peninsula, both data sparse regions, are found to receive 80–96% more accumulation than previously assumed. For the Pine Island and Thwaites Glaciers (West Antarctica), which have recently undergone rapid acceleration and thinning, this means a downward adjustment of their contribution to global sea level rise from 0.24 to 0.14 mm per year. Model time series do not show a significant change in Antarctic accumulation over the period 1980–2004. Citation: van den Broeke, M., W. J. van de Berg, and E. van Meijgaard (2006), Snowfall in coastal West Antarctica much greater than previously assumed, satellite radar altimetry suggests that the East Antarctic ice sheet has thickened between 1992 and 2003, mitigating sea level rise by 0.12 mm per year [Davis et al., 2005]. [3] The reliability of these projections suffers from a lack of in-situ accumulation observations. To obtain full spatial coverage, the sparsely available accumulation observations are usually interpolated using background fields of accumulation-related parameters such as temperature, surface elevation and slope [Giovinetto et al., 1990; Fortuin and Oerlemans, 1990] or passive microwave data from satellites [Zwally and Giovinetto, 1995; Vaughan et al., 1999]. A different approach is to calibrate output of a highresolution regional atmospheric climate model to optimally match in-situ observations. Here we show that the latter approach provides important new insights into the surface mass (im-)balance of Antarctic ice drainage basins.