Comparison of snow accumulation events on two High-Arctic glaciers to model-derived and observed precipitation

Abstract

We evaluate how precipitation forcing data used in glacier mass balance models characterize snow accumulation events on synoptic timescales for two glaciers in north-western Svalbard (Kongsvegen and Holtedahlfonna). Using sonic ranger (snow depth) and wind speed data from automatic weather stations located on the glaciers, we distinguish accumulation events occurring under either calm or windy conditions. We show clear differences in the timing and magnitude of snow accumulation events between the two neighbouring glaciers, illustrating the spatial heterogeneity of snow accumulation in this region. The accumulation measurements show that at equivalent elevations, Kongsvegen receives more snowfall than neighbouring Holtedahlfonna, and that Kongsvegen is more affected by wind-driven snow redistribution than Holtedahlfonna. This is consistent with the synoptically-driven precipitation patterns in the region. Accumulation events are then compared to precipitation data from the nearest meteorological station in Ny-Alesund (ca. 30 km distant) and to a downscaled snowfall data product based on the ERA-Interim reanalysis (nearest gridpoint ca. 300 m distant). Evaluation of the synchrony of observed events at the glacier sites and the precipitation products shows that the ERA-Interim precipitation data reproduce more snowfall events than the Ny-Alesund station data, suggesting that the precipitation fields from distributed reanalysis data provide a more reasonable representation of accumulation on the study glaciers, even over short timescales.