01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-06-0117 |
| Title of Abstract | Subseasonal to seasonal CO2 emissions in the eastern Arabian Sea: physical and biogeochemical drivers |
| Authors | C.K. Sherin*, G.V.M. Gupta |
| Organisation | Centre for Marine Living Resources and Ecology, MoES |
| Address | CMLRE, LNG road, Puthuvype Kochi, Kerala, India Pincode: 682508 E-mail: sherinsci@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Rising atmospheric carbon dioxide (CO2) concentrations, driven by human activities, are altering the ocean⿿s natural ability to sequester carbon. The Arabian Sea, recognised as a major source of CO2 to the atmosphere, remains poorly constrained in terms of coastal flux estimates, necessitating detailed investigation. To better understand the underlying mechanisms and key drivers, basin-scale observations were conducted nine times across the eastern Arabian Sea (EAS) between January 2018 and January 2019. Surface pCO2 ranged from 289 to 1310 µatm, with the lowest mean in early spring (428±30 µatm) and the highest in the late summer monsoon (606±97 µatm). Strong upwelling and cyclonic eddies in the south and central EAS elevated surface pCO2 during the summer monsoon, while moderate upwelling and strong winds drove similar enrichment in the north. Coastal stratification and benthic production suppressed surface pCO2 during non-monsoon periods. Changes in dissolved inorganic carbon and total alkalinity together accounted for 24-85% of pCO2 variability, while temperature explained 12-52%, underscoring the dominant biogeochemical controls on air-sea exchange. Persistently higher surface pCO2 relative to the atmosphere confirms the EAS as a perennial CO2 source, with a mean flux of 4.7±8.4 mmolCm-2d-1 and peak efflux during the summer monsoon (15.9±19.5 mmolCm-2d-1). The monsoon season alone contributed 66% of annual emissions (9.9 TgCy-1), due to upwelling-driven CO2 supply exceeding biological drawdown. The northern EAS accounted for the highest annual emissions (6.5 TgCy-1), driven by shallow thermoclines, weak stratification, and persistent winds. Conversely, deeper thermoclines and strong thermohaline stratification limited fluxes in the central (2.4 TgCy-1) and southern (1.0 TgCy-1) regions. While no clear long-term trend in pCO2 was observed over the past two decades, substantial inter-annual variability was evident. Variations in upwelling and monsoon intensity, linked to ENSO and the Indian Ocean Dipole, significantly modulated CO2 fluxes, highlighting the region⿿s sensitivity to climate variability. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | CO2 flux, Eastern Arabian Sea, pCO2 drivers |
| For Awards | no |