Oxygen isotope/salinity relationship in the northern Indian Ocean

Authors:
  • GDGilles Delaygue
    Gilles Delaygue
  • EBEdouard Bard
    Edouard Bard
  • CRClaire Rollion
    Claire Rollion
  • JJJean Jouzel
    Jean Jouzel
  • MSMichel Stiévenard
    Michel Stiévenard
  • JDJean‐Claude Duplessy
    Jean‐Claude Duplessy
  • GGGerald Ganssen
    Gerald Ganssen
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Abstract
We analyze the surface δ18O‐salinity relationships of the Bay of Bengal and the Arabian Sea, in the northern Indian Ocean, known for their contrasting hydrological conditions. New measurements of these tracers show a very low δ18O‐salinity slope associated with the strong dilution in the Bay of Bengal, but a slope more typical of this latitude in the Arabian Sea. Although this region is marked by a complex monsoonal regime, numerical modeling using a box model and a general circulation model is able to capture the δ18O‐salinity slope and its geographical variation. Both models clearly show that the low δ18O‐salinity slope is due to the evaporation‐minus‐precipitation balance, with an important contribution of the continental runoff in the Bay of Bengal. Although the low value of these slopes (∼0.25) makes past salinity reconstructions uncertain, insight into the Last Glacial Maximum conditions shows a probable stability of these slopes and limited error on paleosalinity.

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