Can oxycline depth be estimated using sea level anomaly (SLA) in the northern Indian Ocean?

Abstract

Information on depth of oxycline is critical not only for understanding magnitude and extent of the hypoxic zone but also for specifying potential fishing zones on operational basis. We analysed Argo-oxygen data from the northern Indian Ocean, along with sea level anomaly (SLA) data from altimeter, to demonstrate the correlation between depths of oxycline, thermocline and SLA. Our analysis suggests that observed variability in oxycline depth is mainly governed by physical processes such as vertical movement in the thermocline depth in the northern Indian Ocean basin. There exists strong positive correlations between depths of thermocline, oxycline and SLA. Oxycline depth and SLA are highly correlated in the Arabian Sea, but the correlation between the two is weaker in the Bay of Bengal and equatorial Indian Ocean. We propose a regression equation between SLA and oxycline depth, which may be used to estimate the depth at which water is oxygen deficient (through oxycline) in the northern Indian Ocean.

Acknowledgement

The encouragement and facilities provided by the Director, INCOIS, are gratefully acknowledged. We thank International Argo Programme for collecting the data and making it freely available for researchers. We also thank various organizations who have contributed significantly towards collection of data and making it available for users. We thank two anonymous reviewers for their critical comments. This is INCOIS publication no. 154.