Expedition 361 Preliminary Report: South African Climates (Agulhas LGM Density Profile)

Jens.Gruetzner [ at ] awi.de


International Ocean Discovery Program (IODP) 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 Cape Basin, were targeted to reconstruct the history of the greater Agulhas Cur- rent system over the past ~5 my. The Agulhas Current is the stron- gest 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 influ- ence southern African climates, including individual weather sys- tems 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 con- trolling the strength and mode of the Atlantic Meridional Overturn- ing Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North At- lantic and global climate change. The main objectives of the expedi- tion were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene–Pleistocene, to determine the dynamics of the Indian-Atlantic 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 Af- rican terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancil- lary Project Letter, consisting of high-resolution interstitial water samples that will 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 span from 0 to between ~0.13 and 7 Ma. This sediment will provide decadal- to millennial- scale climatic records that will allow answering the paleoceano- graphic and paleoclimatic questions set out in the drilling proposal.

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DOI 10.14379/​iodp.pr.361.2016

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Hall, I. , Hemming, S. , LeVay, L. and Expedition 361 Scientists (incl. Jens Gruetzner), (2016): Expedition 361 Preliminary Report: South African Climates (Agulhas LGM Density Profile) , [Other] doi: 10.14379/​iodp.pr.361.2016

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