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Glacial South Atlantic Mid Ocean Circulation and ventilation ages changes derived from cold water corals from off Brazil

Subject Area Palaeontology
Term from 2009 to 2015
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 144733378
 
Final Report Year 2015

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

  • (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.
  • (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.
 
 

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