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Summary of Abstract Submission

Abstract Submission No.ABS-05-0334
Title of AbstractRole of seasonally evolving near-surface salinity stratification on Mixed layer heat budget during Summer Monsoon Intraseasonal Oscillation in the northern Bay of Bengal during 2019
AuthorsV. R. Sherin*, M. S. Girishkumar, S. Shivaprasad, N. Sureshkumar, J.T. Farrar, K. Athulya, K. Ashin, E. Pattabhi Ram Rao, D. Sengupta, R. Venkatesan
OrganisationIndian National Centre for Ocean Information Services, Hyderabad
AddressOcean Observations Network Division (OON), INCOIS
Hyderabad, Telangana, India
Pincode: 500090
Mobile: 8411850594
E-mail: sr.vidwil-p@incois.gov.in
AbstractThe freshwater flux into the Bay of Bengal (BoB) from continental rivers increases in May and peaks in August-September during the summer monsoon. There is a corresponding variation in the strength of the salinity stratification in the upper ocean. Here we examine the difference in mixed layer temperature (MLT) response to Summer Monsoon Intraseasonal Oscillations (MISO) with respect to seasonally evolving near-surface salinity stratification in the northern BoB using accurate surface fluxes and high-vertical resolution temperature, salinity, and current measurements (~2 m) from a mooring in the northern BoB (17.80N, 89.5E) during 2019. Prominent MLT warming and cooling with a range of 1.5C is observed between suppressed (clear skies, calm winds) and active (cloudy, windy) phases of MISO convection. However, the intraseasonal MLT response to the active phase of a late-season MISO event is minimal compared to MISO events in early summer. We infer this is primarily due to the much smaller contribution from oceanic vertical processes (~6 Wm-2) in late summer 2019, compared to their role in early summer (-15 Wm-2 to -55 Wm-2). During the active phase of the MISO event of late summer 2019, the combined effect of reduced entrainment and weak vertical temperature gradients inhibits near-surface cooling. Conversely, the near-surface salinity stratification and the barrier layer were weak during MISO events in the early summer of 2019. These hydrographic conditions led to enhanced MLT cooling in response to MISO, apparently through a freer turbulent exchange of cool thermocline water with the surface layer.
KeywordsMonsoon intraseasonal oscillation, Bay of Bengal, Mixed layer heat budget, Salinity stratification
For Awardsyes
Date Of Birth19-01-1989