Dissolved oxygen as a tracer for intermediate water mixing characteristics in the Indian Ocean

The mixing characteristics of intermediate water at the Central Indian Ocean Basin (CIOB) and the Arabian Sea using dissolved oxygen (DO) as a tracer were studied. Only a few datasets are available in the literature for north–south mixing in this region. Our studies using DO sensor mounted on a remotely operated vehicle in comparison with array for real-time geostrophic oceanography (ARGO) reveal the influence of sub-Antarctic mode water (SAMW) in the study region. Reduction in second oxygen maximum concentration anomaly from south to north may be due to very low concentrated oxygen minimum zone in the Arabian Sea and influence of Red Sea water and the Persian Gulf water. We observed second oxygen maximum concentration at a depth of 300–700 m at CIOB from 150 to 220 μM, compared to the Arabian Sea profiles in the 25–40 μM range with peak value at a depth at 450 m. The present study highlights the usage of high-resolution DO data as tracer for intermediate water circulation in the Indian Ocean and also shows the influence of SAMW up to 8°N along 75°E.