On the Modified Circumpolar Deep Water Upwelling Over the Four Ladies Bank in Prydz Bay, East Antarctica

Analyses of hydrographic observation data sets revealed that modified Circumpolar Deep Water (mCDW) tends to flood the western flank (73-78 degrees E, 67-68 degrees S) of the Four Ladies Bank (FLB) in Prydz Bay. In this study, we investigated the mechanism responsible for mCDW upwelling over the FLB based on an eddy-resolving coupled ocean-sea ice-ice shelf model in conjunction with the latest high-accuracy bathymetry. It was found that zonal step-like declines in the seabed over the FLB are crucial for the mCDW onshore upwelling, through topographic dynamic effects on the alongshore Antarctic Slope Current. In the presence of meridional cross-shelf sigma isopycnals, warm mCDW at 500-m depth in the deep sea can make its approach to the shallower continental shelf (200- to 500-m depths), characterized as a warm layer (> -1.8 degrees C) bounded by the cross-shelf sigma isopycnal surfaces of 27.5 and 27.7kg/m(3). The simulated outflow of the Prydz Bay gyre is concentrated to the eastern flank of the Prydz Channel. These results suggest that, in addition to the depressions and troughs around the Antarctic, smaller topographic features such as step-like declines in the seabed near the Antarctic Slope Current are also favorable for onshore mCDW intrusion. This study demonstrates that mCDW onshore transport around the Antarctic continental shelf might be significantly underestimated by numerical models with coarse spatial representations of the topography. Plain Language Summary Based the observational data sets, warm Circumpolar Deep Water was identified over the Four Ladies Bank in Prydz Bay, East Antarctica. The warm signals could be delivered into the ocean cavity beneath the downstream ice shelf and result in remarkable influences to the ice shelf basal melting. In order to investigate the intrusion of warm Circumpolar Deep Water, we used a numerical model to simulate the oceanic circulations in Prydz Bay. By assessing the simulated results, we found that the topographic influences of the changes in seabed on the continental shelf break jet play a dominant role in the responsible mechanism for warm water intrusion. Our findings highlighted that the improvements in the spatial resolution of the numerical model and the accuracy of the topographical representations are very useful in the investigation of warm water intrusion around the Antarctic continental shelf.