Influence of Antarctic Slope Current variability on modified Circumpolar Deep Water Intrusions in Prydz Bay, East Antarctica

Ruibin Xia, Nanjing University of Information Science & Technology, Nanjing, China, Zhaomin Wang, Hohai University, College of Oceanography, Nanjing, China, Andrew Stewart, University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, United States, Chengyan Liu, Nanjing University of Information Science and Technology, Nanjing, China and Chen Cheng, Nanjing University of Information Science & Technology, School of Marine Sciences, Nanjing, China
Abstract:
Onshore intrusions of modified Circumpolar Deep Water (mCDW) supply heat to the continental shelf of East Antarctica. This heat supply can substantially enhance the basal melt rates of the adjacent ice shelves, as has been shown in the case of Totten glacier. However, the mechanisms that control this heat supply and its temporal variability remain poorly understood. In this study we combine observational data and simulation results from a high-resolution regional numerical ocean/sea ice model to investigate variability of the Antarctic Slope Current (ASC) and its influence on mCDW intrusions in Prydz Bay, East Antarctica. Hydrographic measurements show a strong seasonal cycle in the strength of the ASC upstream of Prydz Bay, with maximum along-slope transport in winter (June to July). Imposing this seasonal cycle as an eastern boundary condition in our model domain leads to strong seasonal variations of the ASC at the mouth of Prydz Bay, and of the transport of mCDW onto the continental shelf. To isolate the influence of ASC changes at the eastern boundary from other potential contributions to the seasonal cycle of mCDW transport, such as local wind and buoyancy forcing, we perform a sensitivity experiment in which the ASC transport at the eastern boundary is halved. Contrary to expectations, we find that mCDW onshore intrusions were increased when ASC was weakened. This increasing of the mCDW transport associated with opposing changes in the variabilities of the mean and eddy transports of mCDW, and with a substantial strengthening of the mean southward transport mCDW transport into Prydz Bay. Our findings indicate that any processes that modifies the strength of the ASC upstream of Prydz Bay will have a substantial influence on mCDW transport onto the shelf there, and that adjustments to both the mean flow and transient eddies are important in determining this response.
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