Topography-Mediated Transport of Warm Deep Water across the Continental Shelf Slope, East Antarctica

Abstract

Warm deep water intrusion over the Antarctic continental shelves threatens the Antarctic ice sheet stability by enhancing the basal melting of ice shelves. In East Antarctica, the Antarctic Slope Current (ASC), along with the Antarctic Slope Front (ASF), acts as a potential vorticity barrier to prevent the warm modified Circumpolar Deep Water (mCDW) from ventilating the cold and fresh shelf. However, mCDW onshore transport is still observed within certain shelf regions, such as submarine troughs running perpendicular to the continental shelf. This study focuses on the dynamic mechanisms governing mCDW intrusion within a submarine trough over the fresh shelf regions, East Antarctica. Based on an idealized eddy-resolving coupled ocean–ice shelf model, two high-resolution process-oriented numerical experiments are conducted to reveal the mechanisms responsible for the mCDW onshore transport. Three dynamic mechanisms governing cross-slope mCDW intrusion are identified: 1) the bottom pressure torque, 2) the topography beta spiral, and 3) the topography Rossby waves. These three mechanisms simultaneously govern the mCDW intrusion together. The bottom pressure torque plays a leading role in driving the time-mean onshore flow whose vertical structure is determined by the topography beta spiral, while the topography Rossby waves contribute to the high-frequency oscillations in the onshore volume and heat transport. The simulated spatial distribution and seasonality of mCDW intrusion qualitatively coincide with the observed mCDW intrusion over fresh shelf regions, East Antarctica. Both the topography beta spiral and the ASC play an important role in governing the seasonality of mCDW intrusion.