Changing surface water conditions for the last 500ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling
Petrick, B.F.; McClymont, E.L.; Marret, F.; van der Meer, M.T.J. (2015). Changing surface water conditions for the last 500ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling. Paleoceanography 30(9): 1153–1167. dx.doi.org/10.1002/2015PA002787
In: Paleoceanography. American Geophysical Union: Washington, DC. ISSN 0883-8305; e-ISSN 1944-9186, meer
The Southeast Atlantic Ocean is an important component of global ocean circulation, as itincludes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productiveBenguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program(ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the latePleistocene (0–500 ka). The UK'37 index and dinoflagellate cyst assemblages are used to reconstruct SSTs,dDalkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenonesand chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitudeof SST warming precedes decreases in benthic d18O and therefore occurs early in the transition from glacialsto interglacials. The dDalkenone, as a salinity indicator, increases before SSTs, suggesting that the pattern ofAgulhas leakage is more complex than suggested by SST proxies. Marine isotope stage (MIS) 10 shows ananomalous pattern: it is marked by a pronounced increase in chlorine concentration, which may be related toenhanced/expanded Benguela upwelling reaching the core site. We find no evidence of an absence of Agulhasleakage throughout the record, suggesting that there is no Agulhas cutoff even during MIS 10. Finally, the ODPSite 1087 record shows an increasing strength of Agulhas leakage towards the present day, which may haveimpacted the intensity of the Atlanticmeridional overturning circulation. As a result, the newanalyses fromODPSite 1087 demonstrate a complex interaction between influences of the Benguela upwelling and the Agulhasleakage through the late Pleistocene, which are inferred here to reflect changing circulation patterns in theSouthern Ocean and in the atmosphere.
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