Advances and next steps in observing and modeling Antarctica’s coastal winds

Westerlies prevail at low levels over most of the Southern Ocean. Within about 400 km of Antarctica, the winds reverse direction and become the polar or coastal easterlies. Closer to the continent, the flow direction is further modified by the complex terrain of the steep coastal slopes. Both the large-scale easterlies and more topographically constrained near-coastal flows are referred to in this report as Antarctic coastal winds (ACWs). ACWs have global importance due to their impacts on ocean circulation, sea ice, and vulnerable ecosystems. As the planet warms, changes to the large-scale circulation may favor a weakening of the coastal easterlies which encircle Antarctica (Bracegirdle et al. 2008). These winds are intimately connected with the structure and dynamics of the Antarctic Slope Front in the ocean, a barrier between cold, fresh shelf waters, and warm circumpolar deep water (CDW; Thompson et al. 2018). CDW intrusions are in turn a key driver of ice shelf basal melt and hence play an indirect role in sea level rise (Spence et al. 2014). ACWs are tied to sea ice production and motion (Haumann et al. 2014; Holland and Kwok 2012), including over polynya regions where Antarctic Bottom Water is formed (Stewart and Thompson 2012). They are also critical for low-level sublimation of precipitation (Grazioli et al. 2017), blowing snow, and moisture advection toward continental Antarctica (Van Lipzig and Van Den Broeke 2002). A growing number of ocean and sea ice modeling efforts have been undertaken to better understand and project air–sea–ice coupling in the Antarctic. All of these require detailed information about ACWs. The goal of this workshop, a key final outcome of a Natural Environment Research Council (NERC) project on ACWs, was to bring together meteorologists, climate scientists, and oceanographers to highlight recent progress in understanding ACWs and to identify priorities for interdisciplinary research. This report details many of these recent advances (section 2–5) presented at the workshop and summarizes research priorities which were emphasized by participants (section 6).