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www.clim-past-discuss.net/7/2193/2011/
doi:10.5194/cpd-7-2193-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
High-latitude obliquity forcing drives the agulhas leakage
1Environnements et paléoenvironnements océaniques, UMR5805, CNRS – Université de Bordeaux 1, EPOC, France
2NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, 1790 AB Den Burg, The Netherlands
3Alfred Wegener Institut (AWI), Germany
4Laboratoire des Sciences du Climat et de l'Environnement, LSCE, Gif-sur-Yvette, France
Abstract. The Agulhas Current (AC) transport of heat and salt from the Indian Ocean into the South Atlantic around South Africa (Agulhas leakage), has a profound role in the decadal variability of the Atlantic meridional overturning circulation (AMOC), which influences global climate. On glacial-interglacial timescales, paleostudies postulate that Agulhas leakage plays a decisive role for AMOC resumption during terminations (glacial-interglacial transitions). However, efforts to elucidate forcing mechanisms connecting Agulhas leakage with glacial-interglacial AMOC variability have been hampered due to a lack of climate records extracted from the area where the AC originates. Here we present 800-kyr sea surface temperature (SST) and salinity (SSS) records from the "precursor" region of the AC. These records contain strong obliquity-driven 41-kyr cycles, nearly in phase with changes in annual mean insolation and air temperature at high southern latitudes. In contrast, precession-driven cycles were negligible in our SST records, which is surprising given the low-latitude location of the Agulhas leakage. Together, this suggests that long-term Agulhas leakage dynamics are associated with a high latitude rather than a tropical climate forcing mechanism, probably by varying the position of the Southern Hemisphere subtropical convergence (STC) and its associated westerlies. We argue that during terminations stronger Agulhas leakage was triggered by increased obliquity exerting a positive feedback on the global climate system through modulating long-term AMOC variations.
Discussion Paper (PDF, 2461 KB) Supplement (849 KB) Interactive Discussion (Closed, 5 Comments) Final Revised Paper (CP)
Notice on Discussion StatusCitation: Caley, T., Kim, J.-H., Malaizé, B., Giraudeau, J., Laepple, T., Caillon, N., Charlier, K., Rebaubier, H., Rossignol, L., Castañeda, I. S., Schouten, S., and Damsté, J. S. S.: High-latitude obliquity forcing drives the agulhas leakage, Clim. Past Discuss., 7, 2193-2215, doi:10.5194/cpd-7-2193-2011, 2011. Bibtex EndNote Reference Manager XML
