Carriers of \emph{Sargassum} and mechanism for coastal inundation in the Caribbean Sea

TL;DR

This paper identifies mesoscale eddies as carriers of Sargassum in the Caribbean Sea using satellite data and explains a mechanism for coastal inundation driven by thermal instability and eddy interactions with bottom topography.

Contribution

It introduces a novel satellite-based method to identify Sargassum carriers and proposes a new physical mechanism for coastal inundation involving thermal instability and eddy dynamics.

Findings

Mesoscale eddies are effective carriers of Sargassum.

Eddy boundaries are identified as coherent material boundaries.

Thermal instability in eddies explains coastal inundation.

Abstract

We identify effective carriers of \emph{Sargassum} in the Caribbean Sea and describe a mechanism for coastal choking. Revealed from satellite altimetry, the carriers of \emph{Sargassum} are mesoscale eddies (vortices of 50-km radius or larger) with coherent material (i.e., fluid) boundaries. These are observer-independent -- \emph{unlike} eddy boundaries identified with instantaneously closed streamlines of the altimetric sea-surface height field -- and furthermore harbor finite-time attractors for networks of elastically connected finite-size buoyant or "inertial" particles dragged by ocean currents and winds, a mathematical abstraction of \emph{Sargassum} rafts. The mechanism of coastal inundation, identified using a minimal model of surface-intensified Caribbean Sea eddies, is thermal instability in the presence of bottom topography.