Thermocline climatology of the Arabian Sea – a review

Abstract

The monthly evolution of the thermocline characteristics for the Arabian Sea based on temperature profiles averaged over 2° × 2° grid cells is presented. During the pre-monsoon period, the entire Arabian Sea is characterized by a shallow thermocline (30–40 m) due to strong surface heating. Upwelling in the coastal regions and downwelling in the central Arabian Sea result in large variations in the thermocline topography during the south-west monsoon. This pattern reverses during winter when the surface currents reverse direction. The thermocline gradient is between 0.04°C m^-1 and 0.14°C m^-1 . An interesting result is the large variability in thermocline gradient (from 0.04°C m^-1 near the coasts to 0.12°C m^-1 in the central Arabian Sea) during July–September throughout the Arabian Sea. Weak gradients noticed in the northern Arabian Sea are due to the interaction of two different warm-water masses (the Arabian Sea and Persian Gulf water masses). The decrease in gradient in the equatorial Arabian Sea from January to June is attributed to the equatorial undercurrent which causes spreading of isotherms in the thermocline.