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Modern and past processes of ocean-atmosphere-climate interactions in the low-latitude western Pacific and Indian Ocean
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Toward a 5 Million Year Record of the Greater Agulhas Current System
Wednesday 9th @ 1330-1350, Conference Room 1
Ian R. Hall* , School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff Wales, CF10 3AT, United Kingdom
Sidney R. Hemming, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, New York 10964, USA
Leah LeVay, International Ocean Discovery Program, Texas A&M University, College Station TX 77845, USA
Expedition 361 Scientists,
Presenter Email: hall@cardiff.ac.uk |
| International Ocean Discovery Program Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel, at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and the Cape Basin were targeted to reconstruct the history of the Greater Agulhas Current System over the past ~ 5 Ma. The Agulhas Current is the strongest western boundary current in the southern hemisphere transporting some 70 Sv of warm and saline surface waters from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates including individual weather systems such as extra-tropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as a control mechanism on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Plio-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, to address the influence of the Agulhas Current on African terrestrial climates and potential links to Human evolution. Here we highlight some of the expedition successes and ongoing post-cruise research to show how it has made major strides toward fulfilling each of these objectives. The recovered sequences allowed complete spliced stratigraphic sections to be generated that span the interval of 0 to between ~0.13 and 7 Ma. These sediments provide an exceptional opportunity to generate decadal to millennial-scale climatic records that will resolve key paleoceanographic and paleoclimatic questions from a region poorly represented in the database of scientific drill sites.
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