Argo observations of barrier layer in the tropical Indian Ocean

Abstract

All the available Argo float observations of temperature and salinity for the period January 2002 through December 2008 have been analyzed to evaluate the seasonal characteristics of barrier layer (BL) in the entire tropical Indian Ocean (TIO). The annual average barrier layer thickness (BLT) in the TIO varies from 10 to 50m, with larger values in the warm pool regions viz., eastern TIO, Bay of Bengal (BOB) and southeastern Arabian Sea (SEAS). Standard deviation is also high (10–35m) indicating strong seasonal variations. The annual average mixed layer depth is low (<50m), whereas isothermal layer depth (ILD) is high (>50m) in these regions. Annual average BLT pattern largely coincides with the average precipitation pattern. The relative importance of atmospheric forcings (wind and precipitation) obtained from satellites and ocean dynamics (once again using satellite-derived currents) has been investigated. Also, net production of energy has been computed to find out the reason for the formation, sustenance and destruction of barrier layer. Expectedly, regions of deep barrier layer have been found to coincide with those of high net energy. A significant interannual variation in BLT has been found in the SEAS and eastern equatorial Indian Ocean (EEIO).