Do Eddies Connect the Tropical Atlantic Ocean and the Gulf of Mexico?

• Published in: Geophysical research letters Vol. 49; no. 20
• Main Authors: Andrade‐Canto, F., Beron‐Vera, F. J.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28-10-2022
• Subjects: Altimeters; Altimetry; Archipelagoes; Brazil Current; Coherence; Current rings; Detection; Eddies; Eddy currents; Filamentation; Fluid flow; geodesic eddies; material transport; North Brazil Current Rings; objectivity; Oceans; Satellite tracking; Satellites; Sea currents; Sea surface; SSH eddy; Streamlines; Topology; Translating; Turbulent flow; Brazil; Gulf of Mexico; Lesser Antilles; United States > US; Atlantic Ocean
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL099637

Consistent with satellite‐tracked trajectories of drogued drifters, but at odds with Eulerian assessment of satellite‐altimetry measurements of sea‐surface height, we show that North Brazil Currents Rings (NBCRs) are incapable of bypassing the Lesser Antilles as structures that coherently transport material. We arrive at this conclusion by applying geodesic eddy detection on the altimetric data set over nearly its entire extent. While we detect northwestward translating NBCRs that can be classified as coherent Lagrangian eddies, they typically experience strong filamentation and complete loss of coherence prior to reaching the Lesser Antilles. Moreover, the filamented material hardly penetrates into the Caribbean Sea, let alone the Gulf of Mexico, and not without substantively mixing with the ambient fluid east of the archipelago. The nature of the inability of the de‐facto oceanographic Eulerian, streamline‐based eddy detection technique to produce a correct assessment of the connectivity between the tropical Atlantic and the Gulf of Mexico is rooted in its lack of objectivity.
Plain Language Summary
Geodesic eddy detection is a Lagrangian (fluid‐parcel‐following) method that objectively, that is, in an observer‐independent manner, reveals eddies (fluid regions spinning about a common axis) with material (fluid) boundaries that defy the exponential stretching that arbitrary material loops typically experience in turbulent flow. Eddies instantaneously revealed as regions enclosed by streamlines in general do not have such a property: the topology of the streamlines depends on the observer viewpoint. Thus instantaneously closed streamlines cannot be guaranteed to hold and carry within material. Here we use geodesic eddy detection to demonstrate that North Brazil Current rings detected from their Eulerian footprints in the altimetric sea‐surface height field do not connect the tropical Atlantic Ocean and the Gulf of Mexico.
Key Points
The topology of sea‐surface height (SSH) streamlines is observer dependent and hence are eddies from the AVISO+ META database
Geodesic eddy detection objectively reveals eddies with stretching resisting material boundaries that also minimize diffusion
North Brazil Current Ring contents hardly penetrate into the Caribbean without mixing with the ambient fluid east of the Lesser Antilles