Spatial and Temporal  Patterns of Chlorophyll-a and Sea Surface Temperature Linked to Typhoon-Induced Ocean Surface Layer Blooms in the Northwest Pacific

This study analyzes typhoon-induced ocean surface layer blooms in the Northwest Pacific from 2015-2022, utilizing Himawari-8/9 satellite data. It highlights the critical importance of intense physical air-sea interactions during these extreme weather events. As typhoons traverse the ocean, their strong winds and the resultant turbulent conditions at the air-sea interface induce significant modifications in the upper ocean’s structure and biogeochemistry, impacting marine ecosystems. Utilizing multi-spectral Himawari-8/9 data, the study tracks the spatiotemporal variability of chlorophyll-a (Chl-a) concentrations and sea surface temperatures (SSTs) around individual typhoon eyes across the basin,  focusing on the seven days preceding and following each storm’s passage. The powerful winds influence upper ocean mixing and upwelling processes, injecting nutrient-rich deep water into the sunlit euphotic zone, and stimulating phytoplankton blooms. These conditions concurrently alter SSTs. A cluster analysis of the Chl-a response around typhoon eyes revealed distinct biogeochemical provinces with differential biological responses, influenced by variations in wind-driven turbulence intensity, stratification, and background nutrient levels unique to each region. Integrating SST data provided further insight into the connections between the physical drivers and variables in bloom intensities. The results offer a deeper understanding of how typhoons can dramatically yet unevenly modify regional ocean surface layer dynamics through intense atmosphere-ocean interactions, leading to pronounced localized phytoplankton blooms.