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The Totten ice shelf (TIS) in East Antarctica has received increasing attention in recent years due to high basal melt rates, which have been linked to a presence of warm modified Circumpolar Deep Water (mCDW) observed at the ice front. We show that mCDW on-shelf intrusions towards the TIS strengthen when the Antarctic Slope Current (ASC) weakens. This demonstrates that the ASC has a blocking effect and ASC weakening leads to on-shelf intrusions, as proposed by previous observational studies. The interannual variability of the ASC is controlled primarily by atmospheric and oceanic conditions beyond our regional model domain. We further show that heat intrusions onto the continental shelf off the TIS are not influenced by off-shelf warming but are enhanced with coastal freshening, suggesting positive feedback whereby ice melt and freshening upstream could start a chain reaction, leading to increased melt, and further coastal freshening.

Recently, a source of Antarctic Bottom Water (AABW) was identified off Cape Darnley at the eastern end of the Weddell-Enderby Basin. However, the behavior and long-term variability of Cape Darnley Bottom Water (CDBW) are not clearly understood. Hydrographic observations from 1974 to 2016 were compared, and a decade-long bottom temperature record was analyzed to clarify multidecadal changes in the CDBW in this region and its downstream influences. In the Cooperation Sea, CDBW spread northwestward with its deepest part reaching to approximately 4,900 dbar. CDBW freshening of 0.001-0.003 decade(-1) was revealed. In the Cosmonaut Sea, long-term AABW warming of approximately 0.01-0.03 degrees C decade(-1) was prominent in the deep basin, while freshening was detected on the upper continental slope. Spatial patterns suggest that an interbasin deep transport of excess freshwater is carried by CDBW and fed into the Weddell Gyre, which might act as an abyssal freshwater buffer. Plain Language Summary Global oceans' abyss is filled with the cold, dense water fed from the Antarctic coastal margin. The Weddell Sea is the most voluminous supplier of this bottom water. In addition to the well-known source of the bottom water, new source regions are discovered recently: Continental shelf off Cape Darnley, East Antarctica, is one of such regions. Vast parts of the ocean around Antarctica is experiencing freshening for these decades, possibly related to an accelerating ice mass discharge from the Antarctic continent. In contrast, the abyssal Weddell Sea has been known to be warming significantly, acting like a huge heat buffer. Our study shows the newly discovered bottom water off Cape Darnley is carrying an increasing amount of freshwater and feeding the excess freshwater into the abyssal Weddell Sea. This suggests that the Weddell Sea experiences changes that originate from a distant, continental source.