Anatomy of a subtropical intrathermocline eddy
Barceló-Llull, B.; Sangrà, P.; Pallàs-Sanz, E.; Barton, E.D.; Estrada-Allis, S.N.; Martínez-Marrero, A.; Aguiar-González, B.; Grisolía, D.; Gordo, C.; Rodríguez-Santana, Á.; Márrero-Díaz, A.; Aristegui, J. (2017). Anatomy of a subtropical intrathermocline eddy. Deep-Sea Res., Part 1, Oceanogr. Res. Pap. 124: 126-139. https://dx.doi.org/10.1016/j.dsr.2017.03.012 In: Deep-Sea Research, Part I. Oceanographic Research Papers. Elsevier: Oxford. ISSN 0967-0637; e-ISSN 1879-0119, more |  |
| Author keywords | Intrathermocline eddy; Mesoscale eddy; Potential vorticity; Canary Eddy Corridor |
| Authors | | Top | - Barceló-Llull, B.
- Sangrà, P.
- Pallàs-Sanz, E.
- Barton, E.D.
| - Estrada-Allis, S.N.
- Martínez-Marrero, A.
- Aguiar-González, B., more
- Grisolía, D.
| - Gordo, C.
- Rodríguez-Santana, Á.
- Márrero-Díaz, A.
- Aristegui, J.
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| Abstract | An interdisciplinary survey of a subtropical intrathermocline eddy was conducted within the Canary EddyCorridor in September 2014. The anatomy of the eddy is investigated using near submesoscale fine resolutiontwo-dimensional data and coarser resolution three-dimensional data. The eddy was four months old, with avertical extension of 500 m and 46 km radius. It may be viewed as a propagating negative anomaly of potentialvorticity (PV), 95% below ambient PV. We observed two cores of low PV, one in the upper layers centered at85 m, and another broader anomaly located between 175 m and the maximum sampled depth in the threedimensionaldataset (325 m). The upper core was where the maximum absolute values of normalized relativevorticity (or Rossby number), |Ro| =0.6, and azimuthal velocity, U=0.5 m s−1, were reached and was definedas the eddy dynamical core. The typical biconvex isopleth shape for intrathermocline eddies induces a decreaseof static stability, which causes the low PV of the upper core. The deeper low PV core was related to theoccurrence of a pycnostad layer of subtropical mode water that was embedded within the eddy. The eddy core,of 30 km radius, was in near solid body rotation with period of ~4 days. It was encircled by a thin outer ring thatwas rotating more slowly. The kinetic energy (KE) content exceeded that of available potential energy (APE),KE/APE=1.58; this was associated with a low aspect ratio and a relatively intense rate of spin as indicated bythe relatively high value of Ro. Inferred available heat and salt content anomalies were AHA=2.9×1018 J andASA=14.3×1010 kg, respectively. The eddy AHA and ASA contents per unit volume largely exceed thosecorresponding to Pacific Ocean intrathermocline eddies. This suggests that intrathermocline eddies may play asignificant role in the zonal conduit of heat and salt along the Canary Eddy Corridor. |
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