The cold and densest Antarctic Bottom Water (AABW) results from negative buoyancy and brine rejection during sea-ice formation. Once formed at the shelf, AABW sinks to the seafloor and migrates northward following the topography, controlling the strength of the global meridional overturning circulation. At the same time, the relatively warm circumpolar deep water (CDW) outcrops at the sea surface, being responsible for the observed melting of continental ice in the Antarctic Peninsula. Hence, sea-ice freezing and melting control the Southern Ocean overturning circulation, playing a key role in the Earth¿s climate system. Here, we explore the relation between sea-ice coverage and water transports in the Powell Basin (northwestern Weddell Sea), with special focus on the transport of AABW through the western South Scotia Ridge into the Scotia Sea. For this purpose, we combine the sea-ice thickness distribution with velocity fields from the GLORYS12V1 reanalysis in the Powell Basin for a 5-years period (between 2017 and 2021). The preliminary results show high interannual variability of sea-ice extent in the region, reaching a maximum of 288.5 km3 in 2019 and a minimum of 144.4 km3 in 2017. This interannual variability is related to substantial changes in the AABW contribution to the Scotia Sea across the western South Scotia Ridge, with mean AABW outflow ranging between 2.5 ± 2.9 and 4.6 ± 1.9 Sv when there is ice coverage and between 1.2 ± 3.0 Sv and 6.6 ± 2.7 Sv when the region is not covered with sea-ice. Further, there appears to be an inverse relation between the CDW and AABW mass transport imbalances throughout the year, independent of the sea-ice cover presence, which suggests that part of the CDW mass transport that enters from the Antarctic ice shelf can be transformed in AABW. The net total mass transport is fairly well balanced during mid and late austral summer, but as the region becomes covered by sea-ice then there is a mean total inflow

Cryosphere 2022 - International Symposium on Ice, Snow and Water in a Warming World, 21-26 August 2022, Reykjavík, Iceland

Peer reviewed