01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0271 |
| Title of Abstract | Weakening of interannual-to-decadal Sea Surface Temperature Variability of the South Indian Ocean: role of internal variability vs forced response |
| Authors | Anjana S, Abhisek Chatterjee*, Weiqing Han, William Kamp |
| Organisation | Indian National Centre for Ocean Information Services (INCOIS) |
| Address | INCOIS, Pragathi Nagar (BO), Nizampet (SO) Hyderabad, Telengana, India Pincode: 500090 E-mail: abhisek.c@incois.gov.in |
| Country | India |
| Presentation | Oral |
| Abstract | Sea surface temperature (SST) variability in the Indian Ocean in the low-frequency (interannual-decadal) timescale is most pronounced in the subtropical South Indian Ocean (STIO; 15oS-40oS). Using a high-resolution global model simulation, we investigate the role of atmospheric forcing and the internal oceanic variability in the observed decline in the low-frequency variability in this region. Observations for the period 1965-2021 suggest a significant shift in the magnitude of low-frequency SST variability in the early 1990s, with a rapid decrease across the STIO, particularly in the central-western basin, except for the eastern basin off the west and northwest Australian coasts, where an increase is detected. After the early 2010s, a revival of SST variability is noted. We show that weakening of surface wind variability played a key role in causing the observed shift in the SST variability in the early 1990s. The heat convergence/divergence within the basin associated with lateral advection also contributes significantly. Dominant climate modes, which explain ~71% of the SST variability in the basin, do not explain the shifts. The external climate forcings, however, likely contribute to the observed weakening. The instability embedded in the large-scale Rossby waves that propagate across the south subtropical Indian Ocean can also significantly contribute to the low-frequency SST variability at the local scale, but owing to its smaller scale, it is unlikely to influence the large-scale observed SST variabilities of this region. Our results highlight that the external climate forcings and the associated change in cross-basin connections are the critical parameters that should be considered for this region's interannual/decadal prediction system. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Climate variability, External forcing, Inter-basin connections, Air-sea intercations |
| For Awards | no |