Local Winds Drive Kerala Coastal Cooling Despite Global El Nino Trends

A fisherman from Marianad village in Thiruvananthapuram district called during a humid July afternoon to report that the sea felt surprisingly cool, defying expectations during an El Nino year when global ocean temperatures were running high. Despite rough seas and risks, fishers were still heading out into deeper waters because murky water helped catch fish easily in nets, and limited shore supply meant high prices and good earnings. El Nino typically warms the tropical Pacific Ocean and shifts global pressure patterns, often weakening the Indian monsoon's moisture flow and making rainfall erratic. However, this global pattern can be offset by the Indian Ocean Dipole. Along the Kerala coast, a separate local process called upwelling occurs when southwest monsoon winds blow parallel to the shore, pushing surface water out to sea and drawing cold, nutrient-rich water up from below. This local wind-driven upwelling operates independently of basin-wide climate events like El Nino. Marianad sits at roughly 8.6 degrees north, well inside a coastal band between 8 and 10 degrees north where alongshore upwelling is strongest. This regional cooling explains why local waters felt cold even while global forecasts predicted warmth, driving fish into deeper zones and creating rich feeding grounds that support diverse marine species and traditional fishing gear like Portuguese-origin boat seines unique to Thiruvananthapuram.