Publication Date:
2014-09-23
Description:
In this work we obtain new results on the manifestation of meddies (or of other deep eddies) at the sea-surface, further developing the results by Bashmachnikov and Carton [2012]. The quasi-geostrophic equations are used to describe a near-axisymmetric vortex in the upper ocean, forced at its lower boundary by the isopycnal elevation of a moving meddy. The solution thus obtained provides a better approximation of the characteristics of meddy surface signals. The results show that in subtropics large meddies with dynamic radius R m ≥ 30 km are always seen at the sea-surface with AVISO altimetry, that medium-size meddies with R m = 20 km may be seen at the sea-surface only if they are sufficiently shallow and strong, while small meddies with R m = 10 km generally cannot be detected with the present accuracy of altimetry data. The intensity of meddy surface signals decreases to the south with the decrease of the f/N ratio. The seasonal variation in intensity of the surface signal for northern meddies (45° N) is on the order of 2-3 cm, but for subtropical meddies (35° N) it can be on the order of 5-10 cm. The radii of meddy surface signals range from 1 to 2 times the radii of the corresponding meddies. For most of the observed meddies the upper limit should be used. Numerical experiments show that surface signals of meddies translated with β- drift are efficiently dispersed by the radiation of Rossby waves. At the same time, for meddies translated by a background current, the surface signal does not show strong dissipation.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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