Objective Detection of Oceanic Eddies and the Agulhas Leakage

• Published in: Journal of physical oceanography Vol. 43; no. 7; pp. 1426 - 1438
• Main Authors: BERON-VERA, Francisco J, YAN WANG, OLASCOAGA, María J, GONI, Gustavo J, HALLER, George
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.07.2013
• Subjects: Altimetry; Biological activity; Boundaries; Climate change; Dynamical systems; Earth, ocean, space; Exact sciences and technology; External geophysics; Flow control; Leakage; Marine; Nonlinear systems; Ocean circulation; Ocean currents; Oceanic eddies; Physics of the oceans; Salinity; Satellite altimetry; Studies; Thermohaline structure and circulation. Turbulence and diffusion; Transport; Transport theory; Velocity; Vortices; Water circulation; South Atlantic; Atlantic Ocean; Agulhas current; Arctic region; ISW, West Indian Ocean, Agulhas Current; AS, South Atlantic; ocean currents; Subtropical gyre; Mesoscale; Oceanic turbulence; Ring current; Measurement technique; Geodesic; Ocean dynamics; Ocean gyre; Vortex; altimetry
• ISSN: 0022-3670; 1520-0485
• DOI: 10.1175/jpo-d-12-0171.1

Mesoscale oceanic eddies are routinely detected from instantaneous velocities derived from satellite altimetry data. While simple to implement, this approach often gives spurious results and hides true material transport. Here it is shown how geodesic transport theory, a recently developed technique from nonlinear dynamical systems, uncovers eddies objectively. Applying this theory to altimetry-derived velocities in the South Atlantic reveals, for the first time, Agulhas rings that preserve their material coherence for several months, while ring candidates yielded by other approaches tend to disperse or leak within weeks. These findings suggest that available velocity-based estimates for the Agulhas leakage, as well as for its impact on ocean circulation and climate, need revision.