Effect of Cyclone Thane in the Bay of Bengal Explored Using Moored Buoy Observations and Multi-platform Satellite Data

This work examines the response of the upper ocean during the passage of cyclone Thane (December 25-30, 2011) over the Bay of Bengal. Observations from a moored buoy are employed to assess the changes in the upper 100 m depth of the ocean. Observations revealed strong temperature inversion prevailing in this region. The temperature inversion resulted in varying response in the subsurface, with warming in the upper 40 m depth and cooling in the depths of 40-80 m at the moored buoy location. Analysis of subsurface temperature and salinity revealed the signatures of vertical mixing induced by Thane. The subsurface currents are observed as strongly responding to the cyclone winds. Analysis revealed that the influence of Thane was generally confined to within 100 m depth. Intense biological response is revealed along the track of the cyclone. However, the bloom is localized in two distinct regions: one in the central Bay and other off the south-western coastal region. This is attributed to the intense Ekman pumping velocity, slow translation speed and the availability of nitrate concentration in the shallow coastal waters.