A new Sargassum drift model derived from features tracking in MODIS images

Area of Science:

• Marine biology
• Oceanography
• Remote sensing

Background:

• Massive Sargassum stranding events impact coastlines globally, from the Gulf of Guinea to the Gulf of Mexico.
• Accurate forecasting of Sargassum transport and stranding necessitates advancements in detection and drift modeling.

Purpose of the Study:

• To evaluate the influence of ocean currents and wind (windage) on Sargassum drift dynamics.
• To improve the predictive models for Sargassum transport and stranding events.

Main Methods:

• Utilized the MODIS 1 km Sargassum detection dataset for automatic tracking of Sargassum aggregates.
• Compared computed Sargassum drift with collocated surface current and wind estimates from drifters and altimetric products.

Main Results:

• Confirmed a substantial total wind effect on Sargassum drift (approximately 3%), with pure windage contributing around 2%.
• Identified a consistent deflection angle of approximately 10° between Sargassum drift direction and wind direction.
• Indicated a reduced role for currents in Sargassum drift, suggesting currents contribute only about 80% of their velocity, likely due to Sargassum's resistance to flow.

Conclusions:

• The findings enhance the understanding of Sargassum's complex drift behavior.
• Improved models incorporating these refined windage and current effects will significantly boost the accuracy of Sargassum stranding forecasts.