01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0327 |
| Title of Abstract | Influence of the extreme Indian Ocean Dipole on the equatorial Indian Ocean circulation |
| Authors | Srinivas Gangiredla*, Amol P, Arnab Mukherjee |
| Organisation | CSIR-National Institute of Oceanography |
| Address | Dona Paula Goa, Goa, India Pincode: 403004 E-mail: srinivasg.nio@csir.res.in |
| Country | India |
| Presentation | Oral |
| Abstract | The Equatorial Indian Ocean (EIO) plays an active role in global and regional climate change through ocean-atmosphere-coupled processes and acts as a base for many global and regional climate and weather patterns. An extreme positive Indian Ocean Dipole (IOD) event occurred in the 2019 boreal autumn, which has induced severe climate impacts around the Indian Ocean region. The ADCP observed high-frequency currents reveal that there is a strong eastward subsurface current at a depth of 50m - 150m persisting from fall 2019 to spring 2020 which is abnormal to a normal condition. Here, observational data, together with the simulations from an ocean model used to identify the processes responsible for the abnormally strong subsurface currents in the EIO during 2019/2020. The Modular Ocean Model (MOM) ocean model shows anomalous strong westward flow in the surface and strong eastward flow in the subsurface at a depth of 50m ⿿ 150m depth consistent with the observation with a good correlation. The surface westward flow during the fall of 2019 was induced by the easterlies driven by a strong positive IOD. However, the subsurface strong eastward flow persisted in the following winter and spring of 2020 after its peak with two-fold stronger and deeper than the pIOD composites. The sensitivity experiments from a linear and continuously stratified (LCS) model reveal that an abnormal westerly wind anomaly in the western EIO is responsible for these high-magnitude subsurface currents. An anomalous westerly wind burst in the western EIO in early June generated an eastward propagating downwelling Kelvin wave, which reflected from the eastern boundary as a downwelling Rossby wave with a westward phase propagation to the western EIO. Our analysis suggests that the equatorial wave dynamics and wind anomalies on the western EIO play a dominant role in the development of an extreme IOD. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Zonal current, Wyrtki Jets, Indian Ocean Dipole, equatorial waves, observations |
| For Awards | no |