Combined influence of strong winds and warm deep water on the formation of Amundsen Sea Polynya in winter

Polynyas play an important role in climate change by enhancing heat and material exchange between the atmosphere and the ocean in polar regions. This study investigated the influence of strong winds and warm deep water on the Amundsen Sea Polynya (ASP), with a particular focus on ASP events during the winter of 2014. The ASP is located directly above the underwater Bear Ridge, with its shape corresponding to the topography. The ASP is more frequently observed on the eastern side than on the western side, due to the influence of the iceberg chain (fast ice) east of the ASP and prevailing southeast winds. However, we found that the occurrence frequency of the ASP is highest in the shallowest points of the topography, rather than near the iceberg chain on the easternmost side. This is related to the upwelling of warm deep water driven by topography. The upward mixing of warm water with the surface waters inhibits sea ice formation and growth there, helping to maintain the ASP on the east side of the Bear Ridge top. Given the potential for a warmer subsurface ocean around Antarctica in the future, enhanced warm deep water mixing could further impact the thermodynamics of the ASP.