The effect of storms on the Antarctic Slope Current and the warm inflow onto the southeastern Weddell Sea continental shelf

Abstract

Storms have been suggested to drive enhanced southward transport of modified Warm Deep Water (mWDW) towards the Filchner Ice Front in the southern Weddell Sea. This region is a known location of dense bottom water production and is thus tightly linked to the global climate system. However, increased heat transport could lead to higher ice shelf melt rates and disrupt dense water production. The role of storms and wind forcing in enhancing the southward heat transport is therefore of interest. We utilize observational records spanning up to four years of data from a network of moorings deployed in the Filchner Trough region to investigate how the regional ocean circulation responds to storm events. We find that about 70 % of the storm events that (i) last sufficiently long (longer than 5.7 d), (ii) have a large enough accumulation of ocean surface stress anomaly throughout the storm (larger than 0.9 N m-2 d-1), and (iii) are severe enough at their peak intensity (maximum stress above 0.5 N m-2) lead to a significant increase in the speed of the Antarctic Slope Current (ASC) just upstream of Filchner Trough while roughly 25 % of the identified events also cause increased southward current speed on the shelf at depths where mWDW is expected to be present during the summer and autumn. At the southernmost mooring (76° S) storm-driven responses are observed mainly during the latter part of the record (mid-2019 to early 2021). This interannual variability in storm response indicates a potential dependency on background hydrography and circulation that remains to be fully explained. This study highlights the potential importance of storms for southward heat transport: an accelerated circulation on the shelf increases the likelihood for warm summer inflow to reach the ice shelf front and cavity before the heat is lost to the atmosphere through winter convection.