01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0379 |
| Title of Abstract | Investigating the Change and Variability in the Indian Ocean Meridional Overturning Circulation |
| Authors | Al Sumaina K N*, Saurabh Rathore |
| Organisation | Indian Institute of Technology |
| Address | Kalluparambil House Chalakudy Thrissur, Kerala, India Pincode: 680307 E-mail: alsumaina@gmail.com |
| Country | India |
| Presentation | Poster |
| Abstract | The Indian Ocean Meridional Overturning Circulation (IMOC) is a key part of the global thermohaline circulation, regulating heat transport, ocean⿿atmosphere interactions, and long-term climate variability. Yet, compared to other basins, its dynamics remain less well understood, particularly across seasonal to multi-decadal timescales. This study investigates the structure, variability, and long-term changes of the Shallow (SMOC) and Deep (DMOC) Meridional Overturning Circulation using multiple ocean reanalysis products (ECCOv4r4, ORAS4, ORAS5, SODA3.15.2, CGLORS, GLORYS2v4) and coupled climate model simulations (CMIP6 and SMILE). Results show distinct seasonal patterns, with monsoon-driven reversals in the Subtropical Cell (STC) and Cross-Equatorial Cell (CEC). Both cells exhibit strong interannual to decadal variability, including a weakening trend during 1992⿿2000 linked to zonal wind stress. Over 80% of reanalysis products agree on these features. The STC, between 5°S⿿20°S, remains anticlockwise year-round, confined to the upper 400 m, and upwells to the Seychelles Dome thermocline ridge. The CEC, linking both hemispheres, upwells to ~10°N off Somalia, reverses from December⿿March, and is anticlockwise otherwise. A clockwise subtropical gyre near 20°S and a northward-flowing equatorial roll between 5°S⿿5°N are also identified. For the DMOC, reanalysis products consistently show two overturning cells: an anticlockwise cell south of 20°S and a clockwise cell near 10°S during boreal winter, both reversing in summer. While CMIP6 models underestimate SMOC features due to weaker wind stress, they reproduce DMOC structures with 80% multi-model mean agreement. A comparison between 1980⿿1989 and 2005⿿2014 highlights significant changes in IMOC strength. These results advance understanding of IMOC variability and its role in Indian Ocean warming, sea-level rise, and ecosystem impacts. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Meridional Overturning Circulation |
| For Awards | no |