Oxycline variability in the central Arabian Sea: An Argo-oxygen study

Dissolved oxygen concentration in the oceanic waters plays a vital role in the global carbon cycle. The addition of oxygen sensors in the ongoing Argo programme could revolutionize our understanding of the ocean's role in climate change. Here we present a first analysis of the oxygen profiles obtained from Argo float 2900776, deployed in the oxygen minimum zone of the central Arabian Sea, one of the thickest oxygen minimum zones in the world ocean. Our study shows perennial oxygen minima in the sub-surface waters of the central Arabian Sea with strong inter-annual and intra-seasonal variability. The depth of the oxycline varies from 60 to 120 m but occasionally it may be as shallow as 40 m. It appears from the present data set that in the southeastern Arabian Sea the low oxygen water shoals up during the early winter monsoon and it is largely controlled by remote forcing. Small scale localized high wind events can cause further shoaling of the oxycline.

► Our study highlights importance of the Argo-oxygen floats.
► Argo oxygen data show seasonal and inter-annual variability in Arabian Sea.
► The oxycline shoals up during early winter monsoon due to Rossby waves.
► Cyclonic wind event causes further shoaling of the oxycline depth.
► Circulation appears to have greater control on maintenance of OMZ.