Seesaw Shift in Sea Surface Height Drives Spring Decline of the Antarctic Slope Current in the Cosmonaut Sea, East Antarctica

Abstract The Antarctic Slope Current (ASC) plays a crucial role in modulating the transport of warm Circumpolar Deep Water onto the continental shelves, influencing ice shelf melting and Antarctic ice sheet mass balance. However, our understandings of the ASC variability and its driving mechanisms remain limited due to observational constraints in the Antarctic region. This study investigates the seasonal variability of the ASC in the Cosmonaut Sea, East Antarctica, focusing on the observed spring weakening of the ASC and its underlying mechanisms. The spring weakening of the ASC is shown to be linked to reduced wind‐driven poleward Ekman transport, which induces a seesaw shift in sea surface height and a subsequent adjustment in the isopycnal structure across the continental slope. Our findings emphasize the importance of understanding the dynamical processes modulating the ASC's strength for assessing future Antarctic ice sheet mass loss and its contribution to global sea level rise.