01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-03-0053 |
| Title of Abstract | Multidecadal to Centennial Variability in ENSO⿿Indian Monsoon Coupling Since 850 CE: Insights from Coupled Model Simulations and Paleo Data Assimilation |
| Authors | Hindhiya Shabu*, Dr Midhun M |
| Organisation | Cochin University of Science and Technology |
| Address | Padaparambath House, Elavoor Angamaly, Kerala, India Pincode: 683572 E-mail: hindhiyashabu@cusat.ac.in |
| Country | India |
| Presentation | Poster |
| Abstract | The El Niño⿿Southern Oscillation (ENSO) exerts a dominant influence on Indian Summer Monsoon (ISM) variability at interannual scales. However, this teleconnection exhibits substantial multidecadal fluctuations, with indications of weakening in recent decades. Understanding the mechanisms underlying such non-stationarity remains critical for predicting monsoon behavior. The limited temporal span of instrumental records constrains our ability to assess the drivers of long-term ENSO⿿ISM variability. To address this, we leverage both paleoclimate reconstructions and simulations from the Community Earth System Model⿿Last Millennium Ensemble (CESM-LME). Our analysis of 31-year running correlations between ENSO and ISM rainfall over the last millennium reveals significant correlation in ~55% of the period, highlighting episodic and non-stationary coupling. We investigate whether this variability stems from external forcings or internal dynamics. While ensemble simulations under various forcings (volcanic, solar, orbital, LULC, and GHG) show some influence on ISM⿿ENSO coherence, we find no systematic linkage between any single forcing and the breakdown or strengthening of the teleconnection, suggesting a dominant role for internal variability. To further explore internal drivers, we classify monsoon years based on ENSO phase and ISM anomaly into compound event types (e.g., El Niño + drought, La Niña + excess). Composite analysis of SST, SLP, and wind anomalies reveals distinct ocean-atmosphere patterns associated with each event type. For example, droughts during neutral ENSO phases exhibit diminished El Niño-like warming in the tropical Pacific, accompanied by North Atlantic cooling, a weak positive PDO-like pattern, and warming in the western Indian Ocean. These findings highlight that ISM variability⿿even during ENSO-neutral years⿿can be modulated by far-field SST anomalies and internal ocean-atmosphere dynamics. Our results underscore the complex, internally modulated nature of ENSO⿿ISM coupling and provide new insights into Indian monsoon variability on multidecadal to centennial timescales. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Indian Summer Monsoon, El Niño⿿Southern Oscillation, ENSO-ISM Correlation, Teleconnection Variability, Paleoclimate Reconstructions, Model Simulations |
| For Awards | yes |
| Date Of Birth | 03-11-1997 |
| ECSN Registration Number | IIOE2-ECSN-0223 |