Temperature Inversion in the Bay of Bengal Prior to the Summer Monsoon Onsets in 2010 and 2011

Freshwater input such as runoff and rainfall can enhance stratification in the Bay of Bengal (BOB) through the formation of a barrier layer, which can lead to the formation of a temperature inversion. The authors focused on the temperature inversion in spring, especially before the onset of the summer monsoon, because previous research has mainly focused on the temperature inversion in winter. Using the hydrographic data from two cruises performed during 24-30 April 2010 and 1-4 May 2011, the authors found that inversions appeared at two out of nine Conductivity-Temperature-Depth Recorder (CTD) stations across the 10 degrees N section and at seven out of 13 CTD stations across the 6 degrees N section in the BOB. In 2010, the inversions (at stations N02 and N05) occurred at depths of approximately 50-60 meters, and their formation was caused by the advection of cold water over warm water. In 2010, the N02 inversion was mainly influenced by the warm saline water from the east sinking below the cold freshwater from the west, while the N05 inversion was affected by the warm saline water from its west sinking below the cold freshwater from its east. In 2011, the inversions appeared at depths of 20-40 meters (at stations S01, S02, S07, S08, and S09) and near 50 m (S12 and S13). The inversions in 2011 were mainly caused by the net heat loss of the ocean along the 6 degrees N section.