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Eddy properties in the Subtropical Countercurrent, Western Philippine Sea

TitleEddy properties in the Subtropical Countercurrent, Western Philippine Sea
Publication TypeJournal Article
Year of Publication2017
AuthorsRamp S.R, Colosi J.A, Worcester P.F, Bahr F.L, Heaney K.D, Mercer J.A, Van Uffelen L.J
JournalDeep-Sea Research Part I-Oceanographic Research Papers
Date Published2017/07
Type of ArticleArticle
ISBN Number0967-0637
Accession NumberWOS:000405054000002
Keywordscore ring 82b; equatorial; interannual variability; Mesoscale eddies; north pacific; ocean; oceanography; pacific; pacific intermediate water; philippine sea; propagation; properties; sound-speed fluctuations; Subtropical Countercurrent; tropical water; water mass

An array of six oceanographic moorings with acoustic and environmental sensors was deployed in the central Philippine Sea from April 2010 to April 2011. The location spanned 18-23 degrees N, 124 - 130 degrees E in the Subtropical Countercurrent (STCC). The most prominent feature of the data set was a densely-packed eddy field with about equal numbers of cyclones and anticyclones moving westward at 6-12 km d(-1). Eddies of either sign displaced the thermocline about +/- 50 m and had surface velocities exceeding 110 cm s(-1). While warm eddies were slightly larger than cold eddies, the distance to maximum radial velocity was similar for both at about 65 km, close to the local Rossby radius of deformation. The steepness parameter U/c in the eddies ranged from 3 to 10, accompanied by relative vorticity of order 0.1-0.3f, suggesting nonlinear, quasigeostrophic features with trapped cores rather than linear waves. This was borne out by the water mass analysis which showed high salinity, high spice North Pacific Tropical Water (NPTW) being transported westward in the warm eddy cores. The total KE and APE in eddies of both signs was about 1x10(15) J with 85% of the APE and 74% of the KE located above 250 m depth. This equipartitioning of energy suggests mature eddies near equilibrium, that had been evolving for some time as they propagated into the area from the east.

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