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
Rr. Rao et R. Sivakumar, 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, J GEO RES-O, 105(C1), 2000, pp. 995-1015
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.