Keywords:Arabian Sea, organic matter, oxygen minimum zone (OMZ), δ15N
The northeastern Arabian Sea is characterized by a widespread midwater oxygen minimum zone (OMZ), between 80 to 1300 m, with oxygen concentrations reaching values of <0.05 mL/L-1at present. In particular, biogenic particle fluxes in this region have experienced large seasonal changes due to strong monsoonal winds in summer and winter. Here we report carbon and nitrogen isotope data for a sediment core (ER-4) collected from this region. Synchronous downcore variations in the δ15N record, which are explained by regional changes in the isotopic composition of subsurface nitrate, and hence denitrification were found. Moreover, these variations are synchronous with Indian monsoon changes during the glacial-interglacial cycles, thereby establishing a link with global climate. We discuss that these climate linked variations in this region that are likely to have experienced marine biogeochemical cycles during the Late Quaternary.