Understanding the formation of the "Great Atlantic Sargassum Belt"

The aim of this thesis is to develop a Lagrangian particle tracking model to explore the
2011 formation of the ’Great Atlantic Sargassum Belt’ (GASB). A new population of free-
floating Sargassum was discovered approximately 20 degrees south of its existing source,
the North Atlantic Subtropical Gyre, also known as the Sargasso Sea. This new population
blooms within the Equatorial Atlantic and flows into coastal waters within the Caribbean
Sea, creating a multitude of environmental and socioeconomic issues.

Firstly, I produced a particle tracking model to simulate Sargassum transport across the
North Atlantic Ocean ±7 years around the anomalous initial bloom of the GASB. Simu-
lations demonstrated an increase in particle transport between the Sargasso Sea and the
Equatorial Atlantic in 2010/2011 when the residual transport from waves (Stokes drift)
was included in the advection field and that the transport path includes the not previously
considered Azores Current.

Next, I added a Sargassum biological model to the particle tracking outputs to explore
along-trajectory changes in biomass to those Sargassum particles that formed the GASB.
Enhanced growth rates were observed within the path of particle trajectories, indicative
of an upwelling event within that region. Results were able to further support that the
GASB was formed due to an anomalous transport event rather than an extreme bloom of
an existing population.

Lastly, I dived deeper into the GASB interannual variability by applying the Sargassum
biological model to a simple box model of the Equatorial Atlantic. Outputs of the box
model were able to determine that variability in GASB biomass was significantly linked
to phosphate availability.