Modified Circumpolar Deep Water inflow to the Dotson-Getz Trough in the summers of 2020 and 2022

The melting of the West Antarctic Ice Shelf has increased since the 1990s,driven by the relatively warm Circumpolar Deep Water(CDW)that penetrates into the West Antarctic Ice Shelf cavities through submarine glacial troughs across the continental shelf.In this study,temperature,salinity,and current velocity data obtained by the Chinese National Antarctic Research Expedition in the Dotson-Getz Trough(DGT)shows clear differences in distribution of modified Circumpolar Deep Water(mCDW)in the summers of 2020 and 2022.Combined with contemporaneous wind data and additional temperature and salinity data from instrumented seals,the processes and mechanisms responsible for this variation are discussed.Compared with 2020,there is a significant increase in mCDW thickness in 2022,with a doubling of total heat content as the mCDW inflow path across the DGT shifts towards the eastern bank.We propose that a southward shift in the westerly winds in the summer of 2022 moved the upper oceanic divergence zone southward towards the continental slope,promoting the upwelling of mCDW above 500 m.Concurrently,stronger westerly winds over the continental slope strengthened the eastward undercurrent,increasing the transport of this mCDW and its associated heat content to the DGT through Ekman dynamics.These observations show there is strong interannual variability in the strength,path and extent of mCDW inflows to the DGT and that care must be taken when planning observation programs for long-term monitoring of the oceanic heat input to the ice shelves of this globally significant region.