North Atlantic fingerprint on severe heatwaves over the Indian region

Abstract Increasing frequency and intensity of heatwaves pose significant challenges for both the population and the ecosystem. Results reveal that the severe heatwave in 2024, along with many historical events, coincided with a distinct negative North Atlantic Tripole (NAT) sea surface temperature pattern, characterized by warming in the tropical and subpolar regions and a cooling anomaly in between. The finding from this study reveals a dynamic mechanism wherein NAT triggers a Rossby wave train that draws energy from the westerly jet stream, propagates toward western Asia, and creates an upper‐level anticyclone. This leads to a blocking pattern and atmospheric subsidence over northern India, thereby exacerbating heatwave conditions. While previous studies emphasized the role of El Niño (EL) in driving heatwaves over India, analysis of observational datasets and Coupled Model Intercomparison Project (CMIP6) simulations reveals that the occurrence of a negative NAT following an EL significantly increases heatwaves over the Indian region. Additionally, the sensitivity experiments using a global coupled model also demonstrate that co‐occurrence of NAT and EL significantly increases the duration and frequency of heatwaves as compared to pure EL‐induced heatwaves. Thus the EL in winter triggers a negative NAT phase in the following spring and the combined influence leads to intensified heat waves over India during April–June. This negative NAT phase further transitions the existing EL phase to the La Niña (LN) phase. With Atlantic warming projected to intensify under greenhouse warming, the potential implications for heatwaves over the Indian region remain unclear. CMIP6 projections for the 21st century indicate a likely increase in North Atlantic warming, accompanied by a significant rise in the frequency and intensity of heatwaves over India, demanding adaptive policies and a heat action plan for vulnerable communities.