Glacial South Atlantic Mid Ocean Circulation and ventilation ages changes derived from cold water corals from off Brazil
Final Report Abstract
Coupled 230Th/U and 14C dates allow reconstruction of the ∆14C history of the ambient seawater for the past ~40 ka BP. It becomes apparent that large depletions in the radiocarbon content of these depths are not a phenomenon restricted to the last termination. Injection of very old waters occurred during the mid-Holocene and glacial period before the onset of the last termination with depletions comparable to other studies. Local hydrocarbon seepage activity as a possible source of 14C-dead carbon can be precluded as indicated by stable isotope measurements. Interestingly, ∆14C activity decrease apparently following in part the decay curve one would expect for a closed system pointing to an isolated and continuously ageing water mass, which bathed the corals. The decoupled behavior of ∆∆14C and εNd for the two deeper cores corroborates the idea of a continuously advecting and simultaneously ageing water mass of a southern ocean origin, which flushed the intermediate-depth core sites off Brazil. Furthermore, the relatively stable εNd values are in accordance with the hypothesis of an isolated deep water reservoir presumably located in the South Atlantic and/or Southern Ocean region and the concept of stable conduits allowing 14C to decay significantly during the purging events.
Publications
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(2013) Cold water corals: A paleoceanogtaphic archive. Tracing past ocean circulation changes in the mid-depth subtropical western South Atlantic off Brazil for the last 40 ka BP, PhD Thesis, University of Heidelberg, 203pp.
Ruckelshausen, M.
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(2010) Deep sea corals off Brazil verifa a poorly ventilated Southern Pacific Ocean during H2, H1 and the Younger Dryas, Earth and Planetary Science Letters, 293: 269-276
Mangini,A., Godoy, J.M., Godoy, M., Kowsmann, R., Santos, G., Ruckelshausen, M., Schröder- Ritzrau, A., Wacker, L.
