Synchroneity of oxygen minimum zone intensity on the Oman and Pakistan Margins at sub-Milankovitch time scales

Abstract

In this paper we present evidence for sub-Milankovitch variability in monsoon intensity from the Oman and Pakistan Margins, northern Arabian Sea. A new high-resolution geochemical record from the Oman Margin combined with microfossil data shows high-frequency variations in sea surface productivity caused by changes in the intensity of summer monsoon-induced upwelling. The local oxygen minimum zone (OMZ), which presently impinges on the Oman Margin, was reconstructed using laminations, redox-sensitive elements and aragonite preservation. Comparison with a Pakistan Margin record shows that OMZ intensity varied synchronously across the basin. OMZ intensity varies together with summer monsoon strength, being weakest during periods of minimum summer monsoon intensity. Correlating the pattern of summer monsoon variability with that of the winter monsoon inferred from proxy records in the northeastern Arabian Sea suggests a reversed relationship between summer and winter monsoon strength. Furthermore, the Oman and Pakistan Margin records confirm earlier results suggesting a link between high northern latitude climate, as reconstructed from Greenland ice cores, and monsoonal climate.