Global Sources of Moisture for Atmospheric Rivers over Antarctica

 

The quantity and characteristics of atmospheric rivers over Antarctica, which import heat and moisture towards the continent, are a major source of uncertainty in future sea level rise estimates. We employ a new variable-resolution grid over Antarctica, using CESM2 (VR-CESM2), which balances the extensibility of a GCM with the high computational costs of a high-resolution climate model. This setup uses observed sea surface temperature and sea ice concentration, implements moisture-tagging (linking precipitation to a moisture source region on the globe), and produces high spatial and temporal resolution atmosphere and ice sheet surface outputs, which can be used to detect atmospheric rivers and to estimate their impact.

As a baseline for experiments testing the relative importance of large-scale drivers, we first quantify, over an idealized 10-year period, the global sources of moisture and the portion of total precipitation that reaches the ice sheet during large-scale vs atmospheric river events (and their associated synoptic characteristics). Beyond this baseline, we will use this setup to perform initial test scenarios assessing the relative impact of reduced sea ice combined with enhanced ocean heat at lower latitudes.