Structure and dynamics of the Antarctic slope and Weddell fronts along the SR04 WOCE section based on four oceanographic cruises (2007–2022)

Abstract

The Antarctic Slope Current (ASC) and the Weddell Front-associated Current (WFC) form a system of bottom-intensified jets found in the continental slope of the Antarctic peninsula, acting as major conduits for the export of dense Weddell Sea waters into the global overturning circulation. We investigate the structure, transport, and multiyear variability of these boundary currents in the northwestern Weddell Sea using hydrographic and velocity data. These include four occupations of the WOCE SR04 section: three RV Polarstern reoccupations between 2016 and 2022, complemented by an earlier occupation in 2007. Our multiyear observations reveal previously unquantified variability in the strength, vertical structure, and water-mass composition of the jets. ASC transport ranges from 0.4 ± 0.2 Sv in 2017 to 7.4 ± 0.3 Sv in 2019, while transport associated with the WFC varies from 5.2 ± 0.6 Sv in 2019 to 8.5 ± 0.7 Sv in 2017. Two key mechanisms emerge as drivers of this variability: (a) enhanced ASC flow associated with dense bottom water, steepening isopycnals and intensifying baroclinic shear, dominating during strong stratification events; and (b) wind-driven barotropic adjustment, indicated by negative wind stress curl aligned with steeper absolute dynamic topography gradients, dominating under strong wind forcing conditions. These findings highlight the combined role of stratification and wind forcing in regulating boundary current variability and establish a novel baseline for evaluating the climate sensitivity of dense water export in the northwestern Weddell Sea.