Premium
Coherent mesoscale eddies in the N orth A tlantic subtropical gyre: 3‐D structure and transport with application to the salinity maximum
Author(s) -
Amores Angel,
Melnichenko Oleg,
Maximenko Nikolai
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc012256
Subject(s) - ocean gyre , argo , eddy , mesoscale meteorology , geology , temperature salinity diagrams , advection , mixed layer , subtropical front , sea surface temperature , atmospheric sciences , salinity , climatology , subtropics , oceanography , geophysics , water mass , mechanics , turbulence , physics , fishery , biology , thermodynamics
The mean vertical structure and transport properties of mesoscale eddies are investigated in the North Atlantic subtropical gyre by combining historical records of Argo temperature/salinity profiles and satellite sea level anomaly data in the framework of the eddy tracking technique. The study area is characterized by a low eddy kinetic energy and sea surface salinity maximum. Although eddies have a relatively weak signal at surface (amplitudes around 3–7 cm), the eddy composites reveal a clear deep signal that penetrates down to at least 1200 m depth. The analysis also reveals that the vertical structure of the eddy composites is strongly affected by the background stratification. The horizontal patterns of temperature/salinity anomalies can be reconstructed by a linear combination of a monopole, related to the elevation/depression of the isopycnals in the eddy core, and a dipole, associated with the horizontal advection of the background gradient by the eddy rotation. A common feature of all the eddy composites reconstructed is the phase coherence between the eddy temperature/salinity and velocity anomalies in the upper ∼ 300 m layer, resulting in the transient eddy transports of heat and salt. As an application, a box model of the near‐surface layer is used to estimate the role of mesoscale eddies in maintaining a quasi‐steady state distribution of salinity in the North Atlantic subtropical salinity maximum. The results show that mesoscale eddies are able to provide between 4 and 21% of the salt flux out of the area required to compensate for the local excess of evaporation over precipitation.