Summary of Abstract Submission

Abstract Submission No. IO50-04-0018PresentationPoster

MECHANISMS CONTROLLING THE OXYCLINE VARIABILITY ALONG THE WEST COAST OF INDIA AT INTERANNUAL TIME SCALE: A MODELING APPROACH

V. Parvathi*1, I. Suresh1, S. Neetu1, M. Afroosa1

1 CSIR-National Institute of Oceanography, India

ABSTRACT :

The land-locked Indian Ocean northern boundary prevents the supply of oxygenated higher-latitude water into the Arabian Sea (AS). This lack of ventilation combines with strong oxygen uptake from the high productivity to produce one of the most intense, perennial, open-ocean oxygen minimum zones in the world oceans. Upwelling of this low-oxygen waters leads to the formation of the world┐s largest natural near-surface low-oxygen zone along the west coast of India. This oxygen deficiency exhibits large year-to-year variations and has strong impacts on the biology and living resources. The natural and anthropogenic, physical and biogeochemical factors that control the oxygen variability along the western Indian coastline however remain elusive. In this study, we assess the physical controls on the oxygen variability off the west coast of India using a regional coupled physical-biogeochemical simulation of the Indian Ocean region over the 1963-2012 period. This simulation captures the seasonal oxygen variability in this region reasonably well, with lowest oxygen content in late summer/early fall, and largest interannual upper ocean oxygen variability in fall. The modelled oxygen variability along the west coast of India is strongly tied to the local thermocline variability at both seasonal and interannual timescales. Seasonal oxygen variations off the west coast of India are driven by the reversing monsoon winds. Remote wind forcing associated with the Indian Ocean Dipole drives a significant part of the interannual oxygen and thermocline variations off the west coast of India during the fall season.