Atmospheric rivers in Antarctica: a closer look

Abstract:

Recent studies confirmed that atmospheric rivers reach the continent of Antarctica and thus influence the Antarctic accumulation patterns and the ice sheet mass balance (Gorodetskaya et al. 2014, GRL). In particular, anomalous accumulation of 2009 and 2011 in Dronning Maud Land in East Antarctica has been linked to atmospheric rivers. Were these years out of the ordinary? Did atmospheric rivers ever reach Antarctic prior to 2009? Should we expect more atmospheric river events to reach Antarctic coast in the future? To answer these questions we take a two-fold approach.

First, we use the newly defined thresholds adjusted to cold Antarctic environment to assess the climatology of atmospheric rivers as seen by ERA Interim Reanalysis. We evaluate the occurrence of atmospheric rivers reaching the coast of Antarctica and consider the role of large-scale atmospheric circulation patterns, such as the Southern Annular mode (SAM), El Nino Southern Oscillation (ENSO) and Zonal Wave 3 (ZW3). In addition, we compare our results with recent evaluation of poleward moisture transport reaching the coast of Antarctica.

Second, we perform a detailed investigation of May 2009 atmospheric river event using the Weather Research and Forecasting (WRF) model simulations. We investigate the synoptic scale development of a storm that led to an anomalous precipitation pattern in East Antarctic. We investigate the role of upper level vs lower level forcing in the formation of the storm. We also perform sensitivity studies to figure out the role of sea ice in the development of this system.