Seasonal circulation, transport, and connectivity of the Gerlache and Bransfield straits based on 20 years of SADCP measurements

Abstract

We use shipboard ADCP data (1999–2018) and a box-integration approach to study the spatial and seasonal variability that regulates water mass exchanges between the Bellingshausen and Weddell Seas in the northwest Antarctic Peninsula. This system comprises three major currents: the Gerlache Strait Current (GSC), the Bransfield Current (BC), and the Antarctic Coastal Current (AACC). The GSC exhibits the clearest seasonality, with significant weakening in autumn (0.10 Sv; 5.2 cm s−1) relative to stronger transport in spring and winter (∼0.30 Sv; ∼19.8 cm s−1), regulated by wind-stress seasonality. Along the western Gerlache margin, flow through Croker Passage shifts southwestward from 0.13 Sv in spring to 0.23 Sv in winter. Large standard deviations indicate strong interannual variability. This pattern suggests that along-stream reversals and across-stream wind-stress intensification modulate the flow. Within the Bransfield Strait, the BC forms a robust northeastward jet year-round, peaking in summer and spring (∼37 cm s−1; ∼0.99 Sv), while the AACC flows southwestward along the Antarctic Peninsula margin (−0.45 to −0.59 Sv). High standard deviations in both indicate strong interannual variability but no significant seasonal differences. These results reveal a seasonally structured circulation rather than a simple GSC-to-BC connection, providing the first statistically supported evidence that wind forcing is a key modulator of GSC variability across the system. The present work provides a robust physical framework for interpreting oceanographic connectivity and shelf-slope exchanges across the western Antarctic Peninsula, while underscoring the need for higher-resolution and in situ observations to resolve the role of intermittent pathways and climate variability.