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A 334-year coral record of surface temperature and salinity variability in the greater Agulhas Current region

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posted on 05.08.2022, 08:50 authored by J Zinke, TK Watanabe, S Rühs, M Pfeiffer, S Grab, D Garbe-Schönberg, A Biastoch
The Agulhas Current (AC) off the southern tip of Africa is one of the strongest western boundary currents and a crucial choke point of inter-ocean heat and salt exchange between the Indian Ocean and the southern Atlantic Ocean. However, large uncertainties remain concerning the sea surface temperature (SST) and salinity (SSS) variability in the AC region and their driving mechanisms over longer timescales, due to only short observational datasets being available and the highly dynamic nature of the region. Here, we present an annual coral skeletal Sr/Ca composite record paired with an established composite oxygen isotope record from Ifaty and Tulear reefs in southwestern Madagascar to obtain a 334-year (1661-1995) reconstruction of δ18Oseawater changes related to surface salinity variability in the wider Agulhas Current region. Our new annual δ18Oseawater composite record from Ifaty traces surface salinity of the southern Mozambique Channel and AC core region from the SODA reanalysis between 1958 and 1995. δ18Oseawater appears to be mainly driven by large-scale wind forcing in the southern Indian Ocean on interannual to decadal timescales. The δ18Oseawater and SST at Ifaty show characteristic interannual variability of between 2 and 4 years and interdecadal variability of 8 to 16 years, coherent with El Niño-Southern Oscillation (ENSO) records. Lagged correlations with the multivariate ENSO index reveals a 1-2-year lag of δ18Oseawater and salinity at Ifaty and the AC region, suggesting that propagation of anomalies by ocean Rossby waves may contribute to salinity changes in the wider southwestern Indian Ocean. The δ18Oseawater and SST reconstructions at Ifaty reveal the highest interannual variability during the Little Ice Age, especially around 1700 CE, which is in agreement with other Indo-Pacific coral studies. Our study demonstrates the huge potential to unlock past interannual and decadal changes in surface ocean hydrology and ocean transport dynamics from coral δ18Oseawater beyond the short instrumental record.

Funding

Royal Society Wolfson Fellowship (grant no. RSWF-FT-180000)

Honorary Fellowship at the University of Witwatersrand

SINDOCOM grant under the Dutch NWO program “Climate Variability” (grant no. 854.00034/035)

NWO ALW project CLIMATCH (grant no. 820.01.009) and the Western Indian Ocean Marine Science Association through the Marine Science for Management programme (grant no. MASMA/CC/2010/02)

History

Author affiliation

School of Geography, Geology and the Environment, University of Leicester

Version

VoR (Version of Record)

Published in

Climate of the Past

Volume

18

Issue

6

Pagination

1453 - 1474

Publisher

Copernicus GmbH

issn

1814-9324

eissn

1814-9332

Acceptance date

01/06/2022

Copyright date

2022

Available date

05/08/2022

Language

en

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