Distribution of floatingSargassumin the Gulf of Mexico and the Atlantic Ocean mapped using MERIS

We used satellite imagery from the European Space Agency (ESA) Medium Resolution Imaging Spectrometer (MERIS) optical sensor to make the first mapping of the full distribution and movement of the population of Sargassum in the Gulf of Mexico and the western Atlantic. For most of the years for which we have data (2002 to 2008), the results show a seasonal pattern in which Sargassum originates in the northwest Gulf of Mexico in the spring of each year, and is then advected into the Atlantic. The Sargassum appears east of Cape Hatteras as a ‘Sargassum jet’ in July and ends northeast of the Bahamas in February of the following year. This pattern is consistent with historical surveys from ships. MERIS provides a spectral band that greatly improves the discrimination of floating vegetation from confusing signals such as cloud and sunglint.