Characteristics of surface signatures of Mediterranean water eddies

Abstract

AbstractIn 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 ≥ 30 km are always seen at the sea‐surface with AVISO altimetry, that medium‐size meddies with = 20 km may be seen at the sea‐surface only if they are sufficiently shallow and strong, while small meddies with = 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 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 subtropical meddies, the upper limit should be used. Numerical experiments show that surface signals of meddies translated with ‐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.