Warm Surface Waters Dominate Melting of the Denman‐Shackleton Ice Shelf System

Abstract

The ocean dynamics controlling the melting of the Denman‐Shackleton ice shelf system are investigated using a high‐resolution regional ocean‐sea ice‐ice shelf model. Our results show that basal meltwater production exhibits strong seasonal variability, driven by the ocean heat supply toward the ice shelf system, and occurs through two distinct melting modes, “shallow” and “deep.” The vertical distribution of the basal meltwater production—and hence the relative contribution of the shallow and deep modes to melting—is modulated by the frequency distribution of ice shelf draft, with the largest ice‐ocean interface area occurring between 100 and 300 m depth. As a result, shallow melting dominates meltwater production in this region, peaking in January‐May when air‐sea fluxes warm sea ice‐free surface waters over the continental shelf. These warmed surface waters are subsequently transported shoreward by wind‐driven onshore Ekman transport, subduct beneath the ice front through downwelling, and become a heat source for shallow basal melting of the ice shelf. At the same time, this wind‐driven Ekman transport sets up the westward Antarctic Coastal Current along the coastal margin, delivering warm surface waters to the ice shelf from the east and thereby further contributing to shallow basal melting. Our results highlight the critical role of sea ice, wind, and air‐sea fluxes in driving basal melting in this region, and suggest that this basal melting is likely to intensify as Antarctic sea ice declines.