Intraseasonal variability in barrier layer thickness in the south central Bay of Bengal

Time series measurements of temperature and salinity recorded at 8 degrees N, 90 degrees E in the south central Bay of Bengal from a Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction buoy, along with satellite altimetry and scatterometer data, are utilized to describe the seasonal and intraseasonal variability of barrier layer thickness (BLT) during November 2006 to April 2009. The BLT shows strong seasonality with climatological minima during both March-May and August-September and maxima during December-February. Large-amplitude, intraseasonal fluctuations in BLT are observed during September 2007 to May 2008 and during September 2008 to April 2009. The observed intraseasonal variability in BLT is mainly controlled by the vertical movement of isothermal layer depth (ILD) in the presence of a shallow mixed layer. Further, the analysis shows that both ILD and BLT are modulated by vertical stretching of the upper water column associated with westward propagating intraseasonal Rossby waves in the southern bay. These waves are remotely forced by intraseasonal surface winds in the equatorial Indian Ocean.