Impact of Tropical Cyclones on Pelagic Sargassum

The strong proliferation of holopelagic Sargassum in the Tropical Atlantic from 2011, raises many questions on the environmental factors controlling their growth and decay at interannual, seasonal, and intraseasonal scales. In this work, we specifically investigate the response of the Sargassum aggregations to high wind events such as those found in Tropical Cyclones (TCs). The evolution of Sargassum coverage obtained from MODIS observations in the north tropical Atlantic Ocean (from 0 to 30 degrees N and from 0 to 100 degrees W) was analyzed under 86 historical paths of TCs and tropical storms from 2011 to 2020 that crossed Sargassum aggregations. Our results show on average a 40% drop in Sargassum coverage under TC trajectories, which can exceed 60% for the most intense TCs. We associate this drop with a sinking of Sargassum toward the deep ocean. Our estimates suggest that TCs contribute to the seasonal decay of Sargassum biomass from August to November.