Abstract

Satellite identification and interpretation of new Sargassum bloom areas in the north Tropical Atlantic have led to considerable misunderstanding of available political and engineering solutions for local Sargassum events in the Caribbean. Cloud cover and satellite resolution have inhibited detection in much of the North Equatorial Recirculation Region (NERR), leading to the assumption that it is ‘blooming’ off Brazil in the North Brazil Current Retroflection (NBCR). Ocean surface transport patterns and events off West Africa, however, suggest that it is a much larger problem, with bloom/growth/mortality and consolidation not easily confined to one relatively small region. In this study winds and surface currents are analyzed over periods significantly longer than the ‘Sargassum era’ which began off Brazil and West Africa in 2011. Archived near surface currents from a finite difference model (HYcom) and a diagnostic model (OCSAR) together with NCEP blended 10 m winds are analyzed by the empirical orthogonal function method to elicit patterns and determine temporal variations in the patterns. Recirculation in two regions is clearly defined: a small western recirculation region associated with the NBCR and a large eastern recirculation region. Although long term trends in the patterns are clear, there was no sudden change in 2010/2011 to suggest that the Sargassum bloom in the NERR was due to hydrography alone. Most likely it was a combination of retention in a warm nutrient rich area together with a seeding mass critical for bloom to occur.

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