Nutrient enrichment induced by tropical cyclone Seroja in the southeastern tropical Indian Ocean

Tropical cyclone (TC) passage triggers a complex response from the adjacent ocean, including vertical mixing, leading to biochemical alterations and affecting the surrounding ecosystem’s dynamics. In previous studies, increased nutrient concentrations and primary production were observed along the cyclone track after the storm. TC Seroja was awakened near the equator in the southeastern tropical Indian Ocean, making it interesting to investigate how the ambient ecosystem responds. Hence, we analyzed the sea surface temperature and nutrient changes during the Seroja event using multi-satellite remote sensing and numerical model data in the south of Indonesia and East Timor along the Seroja track between April 2 and 10, 2021. Immediately after the TC Seroja passed, the sea surface temperature cooled to 3 °C around the TC lane. At the same time, the spatial distribution patterns showed the upsurge of some nutrients in response to the passage of TC Seroja; the surface nitrate swells up to 1.5 mmol/m3, while phosphate increased up to 0.2 mmol/m3, and the dissolved silicate concentration enhanced up to 1.0 mmol/m3. The responses recover within 2-7 days. These results indicate that tropical cyclones contribute to nutrient enrichment in oligotrophic areas outside of their usual annual upwelling time, thereby further supporting ecosystem sustainability.