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| Abstract Submission No. | ABS-2022-11-0256 |
| Title of Abstract | Prolonged La Niña events and the associated heat redistribution in the Tropical Indian Ocean |
| Authors | Soumya Mukhopadhyay*, C. Gnanaseelan, Jasti S. Chowdary, Anant Parekh, Sandeep Mohapatra |
| Organisation | Indian Institute of Tropical Meteorology, Pune |
| Address | TS Division, Indian Institute Of Tropical Meteorology, Dr. Homi Bhava Road, Pash Pune, Maharashtra, India Pincode: 411008 Mobile: 9595714129 E-mail: soumya.mukhopadhyay@tropmet.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | La Niña events influence the tropical Indian Ocean sea (sub) surface temperature, sea level, heat content and ocean transport significantly. In the present study, heat redistribution in the Tropical Indian Ocean (TIO) associated with the prolonged La Niña events during 1958⿿2017 is examined using reanalysis/observations. We have chosen the La Niña events which persist for more than 24-months to study the effects of such events in the TIO. It is found that the prolonged La Niña forcing strengthened the east⿿west thermocline gradient in the equatorial Indian Ocean and propelled the eastward extension of thermocline ridge of the Indian Ocean (TRIO) from its climatological location of southwestern TIO. The cyclonic winds over the southeastern TIO and the associated upwelling Rossby waves are primarily driving the TRIO intensification and its eastward extension. Anomalous subsurface warming, thermocline deepening, and the associated increase in the upper ocean heat content and sea-level in the eastern equatorial Indian Ocean, southeastern TIO and Bay of Bengal (BoB) are characteristic features of the for all the prolonged La Niña events. Moreover, the features like thermocline deepening and sea-level rise in the headbay, intense cooling and anomalous sea level low in the TRIO region and Arabian Sea (AS), cyclonic wind over southwestern TIO are found to be unique of the prolonged La Niña events. Cross equatorial Sverdrup transport near the eastern boundary during the prolonged La Niña events has increased the heat content of BoB and is found to be a pathway of the warm Pacific water entering the north Indian Ocean. The warming (cooling) of the BoB (AS) is speculated to enhance (suppress) pre and post monsoon cyclones over these regions by modulating the tropical cyclone heat potential during these prolonged La Niña events. |