On the role of the Agulhas system in ocean circulation and climate

Abstract

The Atlantic Ocean receives warm, saline water from the Indo-Pacific Ocean through Agulhas leakage around the southern tip of Africa. Recent findings suggest that Agulhas leakage is a crucial component of the climate system and that ongoing increases in leakage under anthropogenic warming could strengthen the Atlantic overturning circulation at a time when warming and accelerated meltwater input in the North Atlantic is predicted to weaken it. Yet in comparison with processes in the North Atlantic, the overall Agulhas system is largely overlooked as a potential climate trigger or feedback mechanism. Detailed modelling experiments—backed by palaeoceanographic and sustained modern observations—are required to establish firmly the role of the Agulhas system in a warming climate.

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Figure 1: Agulhas leakage affected by westerly winds and position of subtropical front.
Figure 2: Warm, saline Agulhas waters influence temperature and salinity in the Atlantic over the full depth of the water column.
Figure 3: Agulhas leakage advects warm, saline waters into the Atlantic, predominantly through Agulhas rings.
Figure 4: Palaeoceanographic time series from the Agulhas leakage corridor spanning the last 570,000 yr.

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Acknowledgements

Fig. 1 was produced by E. Van Sebille and Fig. 2 was produced by H. Van Aken. We thank D. leBars for discussions. L.M.B. is funded by the US National Science Foundation through the ACT project, award no. OCE-0850891. W.P.M.D.R. is funded by the Netherlands Organization for Scientific Research through the INATEX program, ZKO no. 839.08.430. R.Z. receives funding from the Ministerio de Ciencia e Innovación, Spain, through grant CGL2007-61579/CLI. A.B. and R.Z. acknowledge funding by the EC FP7 Marie Curie ITN GATEWAYS. This document is based on work partially supported by the US National Science Foundation under Grant OCE-0938349 to the Scientific Committee on Oceanic Research.

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The ideas presented here were developed jointly by L.M.B., W.P.M.D.R., A.B., R.Z. and the SCOR/WCRP/IAPSO Working Group 136 on the Climatic Importance of the Greater Agulhas System. Working Group 136 is sponsored by the Scientific Committee for Oceanic Research (SCOR), the World Climate Research Program (WCRP) and the International Association for the Physical Sciences of the Ocean (IAPSO).

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Correspondence to Lisa M. Beal.

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Beal, L., De Ruijter, W., Biastoch, A. et al. On the role of the Agulhas system in ocean circulation and climate. Nature 472, 429–436 (2011). https://doi.org/10.1038/nature09983

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