Mesoscale variability of the Antarctic slope front and the slope front current

Abstract

The Weddell Sea is essential for the global climate due to the production of the dense shelf water that contributes to the Weddell Sea Bottom Water (WSBW), feeding the lower limb of the global thermohaline circulation (Orsi et al., 1999). The Weddell Sea continental shelf region is currently protected from the inflow of warm water by the Antarctic Slope Front (ASF). However, we do not know how the slope front will change with the ongoing global warming, and we are concerned about the climatic response if warm water gains access to the continental shelf and accelerate the ice shelf melt rates. We study which mechanisms influence the mesoscale variability of the ASF and the associated Antarctic Slope Current (ASC). We base our study on two mooring arrays located at the eastern flank of the Filchner Trough opening and one mooring array 450 km upstream at 17o W, atmospheric data from the ERA5 reanalysis dataset, and sea ice motion from the NSIDC dataset. We set up time series analysis, frequency spectra and lagged correlations with 15 days of low pass filtering techniques. We find that the thermocline lies at depths of 400-1000 m. The lag in mesoscale variability between the along flow current at the two mooring arrays is shorter than the advective time scale. Combined with high correlation with atmospheric parameters, we conclude that the surface stress and Ekman pumping are strongly influencing the mesoscale variability of the Antarctic slope current. The lag correlation between absolute salinity in the two areas indicates that the variability we see in salinity could be a mix of direct atmospheric forcing and advection.