Abstract This study addresses the dynamics of Agulhas inshore front in submesoscale range upstream 26° E. Submesoscale frontal eddies are observed vicinity Port Elizabeth (26° E) from satellite images and observations collected underwater gliders. Using a submesoscale‐resolving numerical model (dx ∼ 0.75 km), we able to simulate similar eddies. Barotropic instability is confirmed as generation mechanism by one‐dimensional linear stability analysis an eddy kinetic energy budget. Kinetic...

Abstract During the RESILIENCE cruise aboard R/V Marion Dufresne II (April 19–24 May 2022), a high‐resolution in situ observation campaign investigated mesoscale dipole Mozambique Channel, composed of large anticyclonic ring and cyclonic eddy. Using an innovative adaptive sampling strategy to track its movement, we employed continuous observing systems, including Moving Vessel Profiler Acoustic Doppler Current Profilers, capture vertical sections. The results revealed distinct dipolar...

Diurnal warm layers (DWLs) develop under relatively weak winds and strong solar radiation their associated stratified layer has important consequences for turbulent mixing air‐sea interactions.  In this paper we investigate DWLs during three consecutive days in the South Atlantic using observations from an underwater glider equipped with a turbulence microstructure package, series of drifters at two different depths, 1-D model.  The modeling show that create...

A small volume (117 cu‐inch) seismic source producing signal predominantly in the 150–200 Hz frequency window was used during GO calibration experiment Gulf of Cadiz (April–May 2007). The data show scale (<10 m z direction) internal structure ocean. High‐resolution images display reflectors that often appear as distinct, horizontal, short (∼a few hundred meters to a km long) segments, lying at different depths, while low‐resolution (∼20 30 Hz) long, horizontal tens km), sometimes linked...

The Intermediate and Deep Equatorial Tropical Circulations (DEC DTC) consist of a complex system zonal jets. This paper attempts at unifying existing observations theories to present our current understanding this jets system. Recent in situ suggesting continuity between DEC DTC are confronted against the various generation mechanisms that have been proposed literature. key notion differentiate these previous studies lies so‐called “cascade mechanisms,” is, energy pathway equilibration...

The stability of mixed Rossby gravity (MRG) waves has been investigated numerically using three-dimensionally consistent high-resolution simulations the continuously stratified primitive equations. For short enough zonal wavelength, westward phase propagating MRG wave is strongly destabilized by barotropic shear instability leading to formation jets. large-scale zonally generates jets because it consists primarily sheared meridional motions, as shown recently for problem. Simulations were...

The North Atlantic temperature and salinity distributions are strongly influenced by the existence of Mediterranean eddies (meddies) which significantly contribute to transport warm salty Water along different pathways. most common pathways observed be West Canary Current. However, a 2011 seismic reflection cruise conducted BGR Ifremer near North–Western African margin Morocco, MIRROR Leg 2, revealed presence meddy south Azores front very close Morocco coastline. This unusual location strong...

Abstract Evidence of persistent layering, with a vertical stacking sharp variations in temperature, has been presented recently at the and lateral periphery energetic oceanic vortices through seismic imaging water column. The scales ranging from few metres up to 100 m spatial coherence several tens kilometres comparable vortex horizontal size. Inside this situ data display $[{ k}_{h}^{- 5/ 3} { 2} ] $ scaling law for two different quantities, temperature proxy its derivative, but ranges...

Abstract A collision of Mediterranean Water dipoles in the Gulf Cadiz is studied here, using data from MedTop and Semane experiments. First, a eddy (meddy) was surveyed hydrologically November 2000 southwest Cape Saint Vincent. Then, this meddy drifted northeastward position, accompanied by cyclone (detected only via altimetry), thus forming first dipole. In February 2001, dipole measured just after its formation near Portimão Canyon. This second southwestward. The western eastern meddies...

Abstract The dynamics of the formation layering surrounding meddy-like vortex lenses is investigated using primitive equation (PE), quasigeostrophic (QG), and tracer advection models. Recent in situ data inside a meddy confirmed highly density-compensated layers temperature salinity at periphery core. Very high-resolution PE modeling an idealized showed realistic even absence double-diffusive processes. strong density compensation observed model, good agreement with data, suggests that...

This paper investigates the stability of an axisymmetric pancake vortex with Gaussian angular velocity in radial and vertical directions a continuously stratified-rotating fluid. The different instabilities are determined as function Rossby number $Ro$ , Froude $F_{h}$ Reynolds $Re$ aspect ratio ${\it\alpha}$ . Centrifugal instability is not significantly from case columnar due to its short-wavelength nature: it dominant when absolute $|Ro|$ large stabilized for small moderate generalized...

In this paper, we analyse the results from a numerical model at high resolution. We focus on formation and maintenance of subsurface equatorial currents in Gulf Guinea base our analysis evolution potential vorticity (PV). highlight link between submesoscale processes (involving mixing, friction filamentation), mesoscale vortices mean area. simulation, eastward currents, South North Equatorial Undercurrents (SEUC NEUC respectively) Undercurrent (GUC), are shown to be linked westward located...

The available meridional sections of zonal velocity with high vertical and resolution reveal tall eastward jets at 2N 2S, named the extra-equatorial (EEJ), straddling stacked westward smaller scales right equator, so-called equatorial deep (EDJ).In contrast to semi-annual interannual fluctuations in component, measured component is dominated by intraseasonal period.We argue here that formation mechanism for both types linked variability associated wave motions.A process study complemented...

The fine resolution of long geoseismic sections should permit the characterization oceanic turbulence properties over several decades horizontal scales. range scales actually probed by three different acoustic sources is found to be directly linked their frequency content. inertial with a spectral slope k h −5/3 extend up 3 km wavelength for most intense reflectors which surround strong anticyclonic eddies. in situ data analysis confirmed high numerical simulations vortices, rotating...

Abstract The increase of computational capabilities led recent studies to implement very high-resolution simulations that gave access new scale interaction processes, particularly those associated with the transfer energy from oceanic mesoscales smaller scales through an interior route dissipation, which is still underexplored. In this context, we study spindown a mesoscale vortex, unstable mixed baroclinic–barotropic instability. Even though global almost conserved, some transferred down...

Abstract The linear instability of several rotating, stably stratified, interior vertical shear flows $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq \ge =\geqslant \geq \def \Pr {\mathit {Pr}}\def \Fr {Fr}}\def \Rey {Re}}\overline{U}(z)$ is calculated in Boussinesq equations. Two types baroclinic, ageostrophic instability, AI1 and AI2, are found odd-symmetric $\overline{U}(z)$ for intermediate Rossby number ( $\mathit{Ro}$ ). has zero frequency;...

Abstract At the ocean surface, satellite observations have shown evidence of a large spectrum waves at low latitudes. However, very little is known about existence and properties deep variability. Most subsurface rely on localized measurements, which do not allow for global estimation this In study, we use velocity estimates, provided by Argo float drifts 1,000 m, to analyze spatial temporal distribution eddy kinetic energy (EKE) its spectral signature with an unprecedented time space...

Western boundaries have been suggested as mesoscale eddy graveyards, using a diagnostic of the kinetic energy (EKE) flux divergence based on sea surface height (η). The graveyard’s paradigm relies approximation geostrophy — required by use η and other approximations that support long baroclinic Rossby waves dominant contribution to EKE divergence. However, recent study showed an opposite in Agulhas Current region unapproximated Here, we assess validity used derive η-based regional numerical...

The stability of circular vortices to normal mode perturbations is studied in a multi-layer quasi-geostrophic model. stratification fitted on the Gulf Cadiz where many Mediterranean Water (MW) eddies are generated. Observations MW used determine parameters reference experiment; sensitivity tests conducted around this basic case. objective study two-fold: (a) growth rates and nonlinear evolutions unstable for different three-dimensional (3D) velocity structures vortices, (b) check if...

Equatorial observations in the Atlantic show three distinct vertical scales: quasi-barotropic eastward Extra-Equatorial Jets (EEJ), Deep (EDJ) of scale 500-800 m, and a smaller signal (50-100 m) thin layers well-mixed tracer fields.In combined system jets, westward EDJ correspond to zero-Potential Vorticity (PV) "niches," inside which most are found.Because its correlation with zero-PV niches, formation is interpreted as due inertial instability.The latter encompasses barotropic instability...

Abstract In the Canada Basin of Arctic Ocean, warm and salty Atlantic‐origin Water (AW) lies in intermediate layer (250–800 m) below a colder fresher surface layer. It results depth range where vertical thermohaline gradients are propitious to double‐diffusion. Indeed, staircases commonly observed associated with double‐diffusive processes. Using observations from Beaufort Gyre Exploration Project large database Ice‐Tethered Profilers, we document presence density 300–700 m striking strong...

Abstract Oceanic large- and meso-scale flows are nearly balanced in forces between Earth’s rotation density stratification effects (i.e. geostrophic, hydrostatic balance associated with small Rossby Froude numbers). In this regime advective cross-scale interactions mostly drive energy toward larger scales inverse cascade). However, viscous dissipation occurs at scales. So how does the reservoir leak small-scale to arrive climate equilibrium? Here we solve linear instability problem of a flow...

Abstract Nearly all the subsurface eddies detected in seismic imaging of sections northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones observed and studied. In this study, work previous numerical studies is extended investigate some characteristics layering surrounding cyclones, using a primitive equation model with equal diffusivities for salinity temperature suppress effects double diffusion. It shown that, after stable state...

Abstract Western boundary currents are hotspots of mesoscale variability and eddy–topography interactions, which channel energy toward smaller scales eventually down to dissipation. Here, we assess the main eddies sinks in Agulhas Current region from a regional numerical simulation. We derive an eddy kinetic ( ) budget framework vertical modes. It accounts for transfers between reservoirs modes, including channeled by topography. The is dominated (barotropic first baroclinic modes) path...

Abstract The stability of lens-shaped vortices is revisited in the context an idealized quasigeostrophic model. We compute characteristics with higher accuracy and for a wider range Burger numbers (Bu) than what was previously done. It found that there are four distinct Bu regions linear instability. Over primary region interest (0.1 < 10), we confirm first second azimuthal modes only linearly unstable modes, they associated vortex tilting tearing, respectively. Moreover, most mode not...