Drivers of sargassum

WP1 – Drivers

The macroalgae Sargassum grows at the ocean surface, drifting with currents and winds. Mariners have long come across Sargassum in the subtropical Atlantic, but in 2011 large quantities showed up in the tropics.

Multiple drivers of the Great Sargassum Belt

Since then, Sargassum has proliferated, most notably in spring and summer, from the Gulf of Mexico, through the Caribbean, to west Africa. This natural phenomenon presents both environmental problems and opportunities to develop a new natural resource, across the region. The reason for this proliferation of Sargassum across the tropical Atlantic are not fully understood, but multiple drivers are likely involved. Changes in the surface ocean and regional climate may have compounded changes in supplies of nutrients via the great rivers of South America or in dust blown from the Sahara.

A more complete understanding of systematic environmental changes will inform regional adaptation to “Great Sargassum Belt” as it most likely evolves over the next decade. At seasonal timescale, strong winds and swift currents drive Sargassum far and wide, to eventually beach throughout the Caribbean and along the shores of west Africa. With satellite-derived maps of “Floating Algae Index” to specify the distribution of Sargassum early in the season, and with a detailed understanding of winds and currents, we can predict trajectories over many months, to predict the time and quantify beaching events at selected locations. These statistical seasonal predictions are complementing an embryonic Sargassum forecast system based on historical drifter data and operational ocean models, informing local adaptation and resource management.

This work package is led by Prof Bob Marsh, Prof Hazel Oxenford and Prof Kwasi Appeaning Addo.

Outputs from this work package :