Antarctic snow drift processes.

摘要

Wind-driven redistribution of snow on the surface of the Antarctic ice sheet forms an important component of the ice sheet's mass balance as it responds to climate change. Modeling and field studies documented in this dissertation demonstrate that significant mass transport occurs at low wind speeds in the form of drifting snow. This process is often overlooked in studies of blowing snow, a high-wind-speed process that is less common but volumetrically more substantial. Paired measurements of snow accumulation and precipitation in stormy conditions in the Bellingshausen Sea region demonstrate the importance of wind-borne snow transport: only 1/3 of the precipitating snow accumulated on level sea ice surfaces. A review of sastrugi and snow dunes shows they are ubiquitous on the surface of the Antarctic ice sheet, and form through a complex interplay between precipitation, sintering processes, and drifting snow. Including low wind-speed drifting snow in a model of snow transport near a Ross Ice Shelf iceberg-calving rift demonstrates snow infilling at a faster rate than observed topographic change, suggesting corresponding subsidence and basal melt of ice melange within the rift. Drift threshold measurements made on the McMurdo Ice Shelf using multiple sensors indicate that low drift thresholds correspond to smaller particle sizes in motion. This suggests that fine grains enter saltation first, even if fine grain sizes are not representative of the exposed surface snow. The first known precipitation measurements collected from a research ship working near the West Antarctic coastline correspond well with the timing and relative intensity of open-ocean precipitation forecast for co-located grid cells by the ECMWF model. Measurements near ice shelves reveal substantial contamination of any new precipitation signal by snow blown off the ice sheet. This observation helps corroborate the finding that export of snow from Antarctica to the ocean exceeds 5% of total surface accumulation, large enough to be a significant factor in mass balance studies.