Precipitation, sublimation, and snow drift in the Antarctic Peninsula region from a regional atmospheric model

A regional atmospheric model, with a horizontal grid spacing (Deltax) of 14 km, is used to study the surface mass balance components ( precipitation, sublimation, and snow drift) in the region of the Antarctic Peninsula (AP). An integration is performed for the 7-year period 1987-1993, using a realistic forcing at the lateral model boundaries and at the sea surface. Output from this integration indicates that the precipitation reaches its maximum value on the northwestern slope of the AP, where the upward motion in the atmosphere is largest. Uplift occurs upstream of the barrier, affecting the precipitation distribution over sea. The effect of the barrier on the precipitation distribution over the Bellingshausen Sea might have important implications for the ocean circulation in this region. The mean precipitation over the grounded ice of the AP (1.20 m water eq yr(-1)) is 6 times larger than the mean value over all the grounded ice of Antarctica. Our estimates for the surface sublimation and wind transport of snow over the grounding line toward the sea are 9% and 6 +/- 1% of the precipitation, respectively. In situ data of the wind distribution at three coastal sites located on the northern, eastern, and western sides of the AP are used to evaluate the modeled wind field, which is important for the snow drift calculations. For two of the three sites considered, the prevailing wind direction and bimodal wind distribution are correctly represented by the model. The calculated distribution of accumulation and ablation due to snow drift shows a complex pattern. The wind removes snow from the spine of the AP, where the near-surface flow field diverges, whereas deposition occurs mainly on the eastern slopes, where the near-surface flow field converges. An intercomparison between two 7-year integrations at different horizontal resolution (Deltax = 14 km and Deltax = 55 km) shows that the precipitation on the northwestern slope is very sensitive to the model resolution: In the Deltax = 14 km integration, precipitation on the northwestern slope is higher than in Deltax = 55 km because of higher vertical velocities, resulting in a 35% increase in average precipitation over the grounded ice of the AP.