Freshening of Antarctic Bottom Water Off Cape Darnley, East Antarctica
Shigeru Aoki, Katsuro Katsumata, M. Hamaguchi, A. Noda, Yujiro Kitade, Keishi Shimada, Daisuke Hirano, Daisuke Simizu, Yuichi Aoyama, Katsumi Doi, Yoshifumi Nogi
Abstract
Abstract 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°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.