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Periodical breakdown of the Arabian Sea oxygen minimum zone caused by deep convective mixing
Reichart, G.-J.; Nortier, J.; Versteegh, G.J.M.; Zachariasse, W.J. (2002). Periodical breakdown of the Arabian Sea oxygen minimum zone caused by deep convective mixing. Geol. Soc. Lond. Spec. publ. 195: 407-419
In: Hartley, A.J. et al. (Ed.) Geological Society Special Publication. Geological Society of London: Oxford; London; Edinburgh; Boston, Mass.; Carlton, Vic.. ISSN 0305-8719, more
Peer reviewed article  

Also published as
  • Reichart, G.-J.; Nortier, J.; Versteegh, G.J.M.; Zachariasse, W.J. (2002). Periodical breakdown of the Arabian Sea oxygen minimum zone caused by deep convective mixing, in: Clift, P.D. et al. The tectonic and climatic evolution of the Arabian Sea region. Geological Society Special Publication, 195: pp. 407-419, more

Available in Authors 

Keywords
    Arabian Sea; Arabian sea; Oxygen minimum layer; Quaternary; Sea surface temperature; Globorotalia truncatulinoides (d'Orbigny, 1839) [WoRMS]; Marine

Authors  Top 
  • Reichart, G.-J.
  • Nortier, J.
  • Versteegh, G.J.M.
  • Zachariasse, W.J.

Abstract
    The northern Arabian Sea is at present characterized by a pronounced oxygen minimum zone (OMZ) with oxygen concentrations reaching values as low as 2µM between 150 and 1250 m. This intense mid-water OMZ results from high annual organic particle fluxes and a moderate rate of thermocline ventilation. Sediment studies have shown that the intensity of the northern Arabian Sea OMZ has fluctuated on Milankovitch and sub-Milankovitch time scales, in conjunction with changes in either surface water productivity or thermocline ventilation. Here we evaluate the role of convective mixing in the periodical breakdown of the OMZ by reconstructing the density gradient for periods showing a well-ventilated water column. For this reason we reconstructed sea surface temperatures and salinities for the last 70 ka based on alkenone thermometry and d18O analyses on planktic and benthic foraminifers. For the studied time span thermocline ventilation by intermediate water formation in the northern Arabian Sea is a viable mechanism to explain observed fluctuations in the intensity of the OMZ. We postulate that the necessary decrease in the vertical density gradient during well- ventilated periods resulted from intensified winter monsoonal winds in combination with effects caused by glacio-eustacy.

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