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| Abstract Submission No. | ABS-2022-07-0164 |
| Title of Abstract | Differential response of surface ocean pCO2 to tropical cyclones in the contrasting basins of northern Indian Ocean |
| Authors | Trishneeta Bhattacharya*, Kunal Chakraborty, Balaji Baduru |
| Organisation | Indian National Centre for Ocean Information Services |
| Address | Director Bungalow, ground floor, INCOIS, Pragathi Nagar hyderabad, Telangana, India Pincode: 500090 Mobile: 9007660260 E-mail: trishneeta@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | This study examines the spatio-temporal variability of surface ocean pCO2 and its controlling factors in response to the cyclonic events, Phailin (8th -14th Oct 2013; over the Bay of Bengal) and Ockhi (29th Nov-6th Dec 2017; over the Arabian Sea) using a high-resolution, regional ocean-ecosystem model simulated outputs and available surface ocean carbon observations. Dissipation of large amounts of energy into the upper ocean and strong vertical mixing during tropical cyclones erode stratification under the influence of strong winds. As a consequence, colder, nutrient and carbon-rich waters upwell from the deeper layers, creating a favorable environment for biological productivity that eventually utilizes dissolved carbon, leading to striking spatio-temporal pCO2 variability along the track of cyclone. The spatio-temporal variability of pCO2 is strongly associated with the changes in temperature (T), dissolved inorganic carbon (DIC), total alkalinity (ALK), and salinity (S). To identify the factors controlling spatio-temporal variability in pCO2, a decomposition analysis has been carried out. In the case of Phailin (Ockhi), the mean contribution of the deeper, colder water rising to the surface i.e., T-driven changes in inducing pCO2 variability are 5.4 (-8.82) and -7.59 (-58.75) μatm as a response to the pre- and post-cyclonic conditions. In contrast, DIC-driven changes due to the presence of carbon-rich waters at shallower depths are 23.59 (19.5) and 27.76 (77.97) μatm. In the case of Phailin (Ockhi), S-driven changes in inducing pCO2 variability as a response to pre- and post-cyclonic conditions are -18.7 (3.33) and 14.08 (1.04) μatm. Salinity has a relatively lesser control when compared to T- and DIC-driven changes in inducing surface ocean pCO2 variability. But its response to the post-Phailin conditions is significant owing to the strong salinity stratification in the Bay of Bengal. The estimated mixing length for the cyclones Phailin (Ockhi) during their peak is ~35 (~45) m which indicates that stratification is a more dominant controlling factor in the Bay of Bengal than in the Arabian Sea. Alkalinity exerts negligible control in inducing pCO2 variability. In the case of Phailin (Ockhi), ALK-driven changes in inducing pCO2 variability as a response to the pre- and post-cyclone are -0.809 (-2.99) and 0.59 (-0.09) μatm. Contrastingly, the spatio-temporal variability induced by the biological pump, consisting of soft and hard tissues, is 0.005 (0.06) and 0.21 (4.51) μatm. Although the impact of the biological pump is significant in the case of Ockhi, the physical dynamics dominate the biological processes in inducing spatio-temporal variability of surface ocean pCO2 in the case of both cyclones. |