Characteristics of surface signatures of Mediterranean water eddies

Abstract

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 quasigeostrophic 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 5 20 km may be seen at the sea-surface only if they are sufficiently shallow and strong, while small meddies with R m 5 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 subtropical meddies, the upper limit should be used. Numerical experiments show that surface signals of meddies translated with b-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.

Properties and pathways of Mediterranean water eddies in the Atlantic

“…10d). For example, Ceres was observed to strongly weaken after crossing the 890 Azores Current (Richardson and Tychensky, 1997;Bashmachnikov et al, 2014). 891 892 The Rossby number, the ratio of meddy relative vorticity to the Coriolis parameter, 893…”

Vortex merger in surface quasi-geostrophy

“…These new sensors will allow the measurement of sea surface height features at submesoscale, a scale already attained by ocean color (see Gaultier et al, 2013) or SST (sea surface temperature) sensors. Such high-resolution measurements of the sea surface, complemented by high-resolution in-situ measurements, such as VM-ADCP current profiling, seasoar or glider hydrological profiling, or seismic oceanographic transects, and the worldwide, intensive ARGO program of deep-ocean profilers, will provide a three-dimensional picture of surface and of subsurface mesoscale or submesoscale structures in the ocean (see also Filyushkin and Sokolovskiy, 2001;Bashmachnikov et al, 2012Bashmachnikov et al, , 2013Bashmachnikov et al, , 2014. Such highresolution and synoptic databases will allow a complete validation of simple process studies.…”

Surface signature of Mediterranean water eddies in a long-term high-resolution simulation

“…On the other hand, a larger depth of the Meddy core can diminish the eddy surface signal. Surface turbulent features, like surface eddies shed by fronts (e.g, the Azores front [Bashmachnikov et al (2013), Bashmachnikov et al (2014)]) can also perturb the anticyclonic signature of a Meddy and enhance the signal or make it disappear. Bashmachnikov and Carton (2012) found that stronger upper ocean stratications can also reduce the SSH bumps related to an underlying Meddy.…”