Expedition 361 summary

Jens.Gruetzner [ at ] awi.de


International Ocean Discovery Program Expedition 361 drilled six sites on the southeast African margin (southwest Indian Ocean) and in the Indian-Atlantic Ocean gateway, 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 Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ~5 My. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water 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 extratropical 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 may influence 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 role of the Agulhas Current in climatic changes during the Pliocene–Pleistocene, specifically to document the dynamics of the Indian-Atlantic Ocean gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of Ancillary Project Letter number 845, consisting of high-resolution interstitial water sampling to help constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that range from 0 to between ~0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal.

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DOI 10.14379/iodp.proc.361.101.2017

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Hall, I. , Hemming, S. , LeVay, L. , Barker, S. , Berke, M. , Brentegani, L. , Caley, T. , Cartagena-Sierra, A. , Charles, C. , Coenen, J. , Crespin, J. , Franzese, A. , Gruetzner, J. , Han, X. , Hines, S. , Jimenez Espejo, F. , Just, J. , Koutsodendris, A. , Kubota, K. , Lathika, N. , Norris, R. , Periera dos Santos, T. , Robinson, R. , Rolinson, J. , Simon, M. , Tangunan, D. , van der Lubbe, J. , Yamane, M. and Zhang, H. (2017): Expedition 361 summary / I. Hall , S. Hemming , L. LeVay and t. Expedition 361 Scientists (editors) , In: South African Climates (Agulhas LGM Density Profile), Proceedings of the International Ocean Discovery Program, 361, College Station, TX, International Ocean Discovery Program . doi: 10.14379/iodp.proc.361.101.2017

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