Seasonal variability of near-surface thermal structure and heat budget of the mixed layer of the tropical Indian Ocean from a new global ocean temperature climatology

A subset of the global ocean temperature climatology is used to characteriz e the observed seasonal variability in the near-surface thermal structure o f the tropical Indian Ocean. In the near-surface isothermal layer the seaso nal variability is least in the warm pool region and increases poleward. Ov er much of the tropical Indian Ocean, local surface heat fluxes overwhelm h orizontal advection in the seasonal evolution of the mixed layer temperatur e. Entrainment cooling is weaker by an order of magnitude than the other tw o processes. Several dynamical processes produce the most prominent signals in the thermocline in different geographic regions, such as coastal upwell ing/downwelling with associated reversals in the flow off Arabia, off south west India, and off the east coast of India, Ekman-driven thermocline deepe ning in the central Arabian Sea, convergence of waters caused by Wyrtki Equ atorial Jets in the eastern equatorial Indian Ocean, Ekman divergence of a dome of cold waters just south of the equator in the west, propagating Kelv in waves in the coastal regions of the Bay of Bengal, and propagating Rossb y waves from Off southwest India to Somalia and in the Indo-Pacific through flow region. For the spatiotemporal resolutions considered in this study th e penetration of the seasonal cycle of temperature appears to be limited to 150 m depth or so. Numerical model solutions have revealed the causative m echanisms for some of the prominent signals seen in the observations, in pa rticular, those driven by long-period propagating waves in regions of large stratification, whose structure was not revealed by earlier climatologies to date, as revealed by this new climatology.