From Bottom‐Water Production to Warm Water Intrusions—The Cenozoic History of Bottom‐Current Evolution Offshore the Denman‐Shackleton Region, East Antarctica

Abstract

AbstractThe deep glacial trough and hinterland of the Denman Glacier (East Antarctica) makes the area around the Shackleton ice shelf sensitive to ice loss due to warmer deep water intruding onto the continental shelf in the near future. In addition, the configuration of the ocean currents offshore is an important factor in priming the local and regional vulnerability to warm water intrusions. Here, we use reflection seismic data sets from the Bruce Rise offshore the Denman‐Shackleton region to investigate the Cenozoic history of the ocean bottom current configurations offshore and their influence on the Cenozoic sedimentation patterns of the Denman‐Shackleton region. On the Bruce Rise, sediment drift building, and erosional features indicate three distinct ocean current configurations, (a) the production of dense shelf waters in times of a smaller East Antarctic Ice Sheet (EAIS), (b) periods dominated by a strong Antarctic Slope Current (ASC) and (c) periods with a weak ASC. During the early establishment of the EAIS, the Denman‐Shackleton area contributed to the production of Antarctic Bottom Water, a process which stabilizes the regional ice sheet. With a growing icesheet, the ASC strengthened representing an effective barrier between the continental shelf and the warmer water masses of the deeper ocean during most of the times of an extended EAIS. The transition in the paleoceanographic setting from a strong, erosive ASC, toward a weak ASC increases the vulnerability of the Denman‐Shackleton continental shelf to deep water intrusions as we are observing today.