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Salt exchange in the Indian-Atlantic Ocean Gateway since the LGM: A compensating effect between Agulhas Current changes and salinity variations?

Simon, Margit H., Gong, Xun, Hall, Ian Robert, Ziegler, Martin, Barker, Stephen, Knorr, Gregor, van der Meer, Marcel T. J., Kasper, Sebastian and Schouten, Stefan 2015. Salt exchange in the Indian-Atlantic Ocean Gateway since the LGM: A compensating effect between Agulhas Current changes and salinity variations? Paleoceanography 30 (10) 10.1002/2015PA002842

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Abstract

The import of relatively salty water masses from the Indian Ocean to the Atlantic is considered to be important for the operational mode of the Atlantic Meridional Overturning Circulation (AMOC). However, the occurrence and the origin of changes in this import behaviour on millennial and glacial/interglacial timescales remains equivocal. Here we reconstruct multiproxy paleosalinity changes in the Agulhas Current since the Last Glacial Maximum and compare the salinity pattern with records from the Indian- Atlantic Ocean Gateway (I-AOG) and model simulations using a fully coupled atmosphere–ocean general circulation model. The reconstructed paleosalinity pattern in the Agulhas Current displays coherent variability with changes recorded in the wider I-AOG region over the last glacial termination. We infer that salinities simultaneously increased in both areas consistent with a quasi-inter-hemispheric salt-seesaw response, analogous to the thermal bipolar seesaw in response to a reduced cross-hemispheric heat and salt exchange during times of weakened AMOC. Interestingly, these hydrographic shifts can also be recognised in the wider Southern Hemisphere, which indicates that salinity anomalies are not purely restricted to the Agulhas Current System itself. More saline upstream Agulhas waters were propagated to the I-AOG during HS1. However the salt-flux into the South Atlantic might have been reduced due to a decreased volume transport through the I-AOG during the AMOC slowdown associated with HS1. Hence, our combined data-model interpretation suggests that intervals with higher salinity in the Agulhas Current source region are not necessarily an indicator for an increased salt import via the I-AOG into the South Atlantic.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Water Research Institute (WATER)
Additional Information: PDF uploaded in accordance with publisher's policies at http://www.sherpa.ac.uk/romeo/issn/0883-8305/ (accessed 2.10.15).
Publisher: American Geophysical Union
ISSN: 0883-8305
Funders: NERC and EU
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 19 September 2015
Last Modified: 01 Jul 2019 10:11
URI: http://orca.cf.ac.uk/id/eprint/77251

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