Marine heatwaves are episodes of anomalously warm sea surface temperatures lasting days to weeks. In the Arabian Sea, they concentrate along the eastern and northern coasts — and their frequency is increasing rapidly, largely driven by anthropogenic warming.
Suhas et al. (arXiv:2603.18319) trace the mechanism from ocean surface to extreme rainfall on land. When the Arabian Sea surface overheats, it drives cyclonic winds. The warm water supercharges evaporation, the moist air converges, and the atmospheric circulation intensifies moisture transport toward the Indian coast. The result: extreme precipitation events along southwestern India.
The trigger mechanism is counterintuitive. Most marine heatwaves in this region are short-lived — under three weeks — and they form not from ocean currents bringing in warm water but from the atmosphere itself. During lulls in the monsoon's intraseasonal oscillations, cloud cover breaks, solar radiation floods the surface, and evaporative cooling weakens simultaneously. The ocean heats from above, through a gap in its own weather system.
The chain then reverses: the overheated ocean patch feeds moisture back into the atmosphere, intensifying the next active monsoon phase. When that intensification hits the western Indian coast or — in the case of northern Arabian Sea heatwaves — the mountainous terrain of northwestern India and Pakistan, the result is extreme flooding. The 2022 Pakistan floods followed this pattern.
A pause in the monsoon exposes the ocean to the sun. The sun heats the water. The heated water feeds the next monsoon pulse. The monsoon pulse produces extreme rain. The cycle requires the monsoon to fail briefly in order to succeed catastrophically — the calm builds the bomb.