12:00–12:15 | ABSTRACT 1159
Thermal Signature of Sargassum aggregations from Landsat 9 Observations
Since 2011, Sargassum blooms in the Tropical Atlantic have led to massive strandings along coastlines, posing significant ecological, economic, and public health threats. A key research challenge is to better understand the environmental drivers of Sargassum growth and decay. Temperature has already been identified as a major factor influencing growth rates and in-situ measurements suggest that Sargassum aggregations could be warmer than the surrounding Sea Surface Temperature. We analyze three years of Landsat 9 observations in the Caribbean, combining high resolution Sargassum detections based on the optical sensor and thermal sensors to estimate the temperature of the Sargassum aggregations. We use Scaled Algal Index calculation associated with optical spectrum shape criteria for Sargassum detections and state of the art algorithm we regionally calibrated provide surface temperatures. The dataset obtained allows to quantify the temperature difference between Sargassum aggregations and surrounding waters for 4,390 aggregations in three key regions: the Lesser Antilles, Haiti, and Mexico. Our results confirm a consistent warming of Sargassum aggregations compared to nearby waters, with temperature differences reaching 1.5°C in the Lesser Antilles, and up to 1.8°C near Haiti and Mexico. We show that the magnitude of warming is influenced by aggregation size, shape, and local environmental conditions, particularly net heat flux and wave height. These findings highlight the need to account for aggregation warming in Sargassum growth and decay models. Furthermore, this work underscores the importance of expanded in-situ measurements to better characterize the vertical thermal structure and diurnal variability of Sargassum aggregations.
Amaia Fontan*, LEGOS, [email protected], https://orcid.org/0009-0002-3010-6730
Julien Jouanno, LEGOS, [email protected]
Pierre-Etienne Brilouet, LEGOS, [email protected]
Thibault Guinaldo, CNRM, [email protected]
