Arabian Sea high salinity core supplies oxygen to the Bay of Bengal

Abstract

The oxygen minimum zone (OMZ) in the Bay of Bengal (BoB) is unique owing to its curious capability to maintain steady dissolved oxygen (DO) levels. In this study, we identify a process by which the oxygen is supplied to the BoB, using DO and microstructure profiles in the southern BoB and Argo profiles over the entire basin. A high salinity core (HSC) rich in DO is advected by the Summer Monsoon Current (SMC) into BoB. Vertical mixing driven by turbulent processes recharge DO concentration in thermocline above OMZ. Salt-fingering processes were active below the HSC and were observed to enhance the vertical mixing. HSC identified in the Argo data, also rich in oxygen, can be traced up to 19° N, confirming that HSC is a source of DO and potentially prevents OMZ from moving to the denitrification regime. This might be a potential oxygen source for the BoB OMZ in changing climate conditions.