• AJAI KUMAR RAI

      Articles written in Journal of Earth System Science

    • Benthic foraminiferal response to changes in the northwestern Arabian Sea oxygen minimum zone (OMZ) during past ${\sim}$145 kyr

      VISHWESH KUMAR PATHAK ASHISH KHARWAR AJAI KUMAR RAI

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      The benthic foraminiferal abundance and diversity for the last ${\sim}$ 145 kyr at ODP Hole 723A in the northwestern Arabian Sea have been analyzed to better understand the factors responsible for the changes in the strength of Oxygen Minimum Zone (OMZ). The decline in the abundance of dysoxic taxa and more diverse fauna during interstadials of MIS 5 (5.5 and 5.1) along with higher percentages of G. bulloides reveal that the increased advection of well-oxygenated southern deep waters enhanced the rate of remineralization of sinking organic matter and also reduced the strength of OMZ. The improved supply of organic matter to the sea floor due to southwest summer monsoon linked higher surface productivity between 114 and 108 ka and 102 and 92 ka enhanced the decay of organic matter utilizing more oxygen at intermediate depths which resulted in the development of strong OMZ. The increased inflow of well-oxygenated Sub-Antarctic Mode and Antarctic Intermediate Waters (SAMW-AAIW) and significantly reduced or negligible outflow of low oxygen Red Sea Water (RSW) in the northwestern Arabian Sea developed relatively weak OMZ and better bottom water oxygenation during early Holocene. The low abundance of G. bulloides indicates decline in the surface water productivity due to weaker southwest summer monsoon during late Holocene while more outflow of oxygen poor RSW at intermediate depths and no further inflow of well oxygenated SAMW-AAIW beyond 5$^{\circ}$N relatively strengthens the OMZ in the northwestern Arabian Sea.

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