Drift formation history off MacRobertson Land Shelf, East Antarctica, reveals paleo-distribution of Cape Darnley Bottom Water

ricarda.nielsen [ at ] awi.de


Within Meridional Overturning Circulation, formation of Antarctic Bottom Water (AABW) plays an essential role and is widely accepted to be the engine of global Thermohaline Circulation (THC), which is sensitive to climate changes. Studying paleo conditions and changes of AABW distribution during warm and cold periods is fundamental to gain knowledge about its interaction and response to climate changes, which helps to understand recent and future changes of THC due to global warming. Along MacRobertson Land Shelf area, west of Prydz Bay in East Antarctica, a recent production of dense shelf water has been recognized in the Cape Darnley Polynya and outflow as so-called Cape Darnley Bottom Water (CDBW) along the Wild Canyon. CDBW contributes around 6-13% to the total circumpolar AABW. In order to understand the paleo conditions of AABW, it is necessary to investigate the paleo-evolution of CDBW. To do this, we have studied the formation history of a 200 km long sediment drift (Darnley Drift herein) at the western flank of the Wild Canyon. We utilized more than 13.000 km of multi-channel seismic reflection data and lithological Data of ODP Site 1165. We characterized Darnley Drift to be a mixed turbiditic-contourite drift formed by an interplay of downslope and along-slope processes. Turbiditic outflow along the later formed Wild Canyon dominated during the Oligocene. An onset of CDBW can be inferred during the early Miocene, forming an asymmetric channel-levee system along the Wild Canyon. After the mid-Miocene Climatic Optimum a major climate change occurred, resulting in a strong intensification of bottom currents and major growth of the drift with simultaneous areas of non-deposition and erosion. This was followed by a sharp reduction of sedimentation rates. Since the late Miocene the growth of Darnley Drift is further dominated by contourite bottom currents.

Item Type
Conference (Poster)
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Primary Topic
Helmholtz Cross Cutting Activity (2021-2027)
Publication Status
Event Details
81. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, 01 Mar 2021 - 05 May 2021, online.
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Cite as
Nielsen, R. and Uenzelmann-Neben, G. , Alfred-Wegener Institut, Helmholtz Zentrum für Polar und Meeresforschung (2021): Drift formation history off MacRobertson Land Shelf, East Antarctica, reveals paleo-distribution of Cape Darnley Bottom Water , 81. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, online, 1 March 2021 - 5 May 2021 .

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