This study investigates the impact of tropical cyclones on phytoplankton blooms in the North Indian Ocean (NIO) using two decades of satellite ocean color data (1997-2019). Cyclone-induced chlorophyll-a (Chl-a) blooms, significantly exceeding pre-cyclone levels (by 20-3000%), are observed. Bloom intensity inversely correlates with cyclone translational speed, with slower storms leading to more intense blooms. Cold-core eddies further enhance Chl-a concentrations when encountered by cyclones. La Niña years exhibit larger blooms than El Niño or normal years, while the Indian Ocean Dipole (IOD) impacts bloom amplitude differently in the Bay of Bengal and Arabian Sea. The study provides insights into cyclone-induced primary production, remote forcing, and climate change impacts on NIO.

J. Kuttippurath, N. Sunanda, M. V. Martin, Kunal Chakraborty