Richard C. Schopp

Institut Français de Recherche pour l'Exploitation de la Mer CNRS LPO · laboratoire d'océanographie physique et spatiale

The Intermediate and Deep Equatorial and Tropical Circulations (DEC and DTC) consist of a complex system of zonal jets. This paper attempts at unifying existing observations and theories to present our current understanding of this jets system. Recent in situ observations suggesting a continuity between DEC and DTC are confronted against the variou...

The stability properties of a vortex lens are studied in the quasi geostrophic (QG) framework using the generalized stability theory. Optimal perturbations are obtained using a tangent linear QG model and its adjoint. Their fine-scale spatial structures are studied in details. Growth rates of optimal perturbations are shown to be extremely sensitiv...

Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding M...

The dynamics of layering surrounding meddy-like vortex lenses is investigated from a tracer stirring point of view using a tracer advection model as well as Primitive Equation (PE) and Quasi Geostrophic (QG) models. Recent in situ data inside a meddy as well as high resolution PE simulations reveal the formation of highly density-compensated layers...

Evidence of persistent layering, with a vertical stacking of sharp variations in temperature, has been presented recently at the vertical and lateral periphery of energetic oceanic vortices through seismic imaging of the water column. The stacking has vertical scales ranging from a few metres up to 100 m and a lateral spatial coherence of several t...

This work addresses the linear dynamics underlying the formation of density interfaces at the periphery of energetic vortices, well outside the vortex core, both in the radial and axial directions. We compute numerically the unstable modes of an anticyclonic Gaussian vortex lens in a continuously stratified rotating fluid. The most unstable mode is...

Depth-dependent barotropic instability of short mixed Rossby–gravity (MRG) waves is proposed as a mechanism for the formation of equatorial zonal jets. High-resolution primitive equation simulations show that a single MRG wave of very short zonal wavelength and small to moderate amplitude is unstable and leads to the development of a largely barotr...

Equatorial observations in the Atlantic show three distinct vertical scales: quasi-barotropic eastward Extra-Equatorial Jets (EEJ), Equatorial Deep Jets (EDJ) of scale 500-800 m, and a smaller scale signal (50-100 m) of thin layers of well-mixed tracer fields. In the combined system of jets, westward EDJ correspond to zero-Potential Vorticity (PV)...

The available meridional sections of zonal velocity with high vertical and meridional resolution reveal tall eastward jets at 2N and 2S, named the extra-eqaatorial jets (EEJ), straddling the stacked eastward and westward jets of smaller vertical scales right at the equator, the so-called equatorial deep jets (EDJ). In contrast to the semi-annual to...

Low-frequency variations of the large-scale ocean circulation in the Atlantic are reconstructed from NODC pentadal anomalies of temperature and salinity from 1955 to 1998 based on hydrographic data, in addition to atmospheric reanalysis surface forcing. Diagnostic ocean circulations are estimated from simple methods using dynamical model integratio...

The stability of mixed Rossby gravity (MRG) waves has been investigated numerically using three-dimensionally consistent high-resolution simulations of the continuously stratified primitive equations. For short enough zonal wavelength, the westward phase propagating MRG wave is strongly destabilized by barotropic shear instability leading to the fo...

Master 2 Physique Océan Atmosphère Question posée: quelle est la dynamique de la pycnocline et comment cette structure peut être reliée au forçage du vent Arnaud David Sous la direction de Richard Schopp 2008

Antarctic Intermediate Water (AAIW) occupies the intermediate horizon of most of the world oceans. Formed in the Southern Ocean, it is characterized by a relative salinity minimum. With a new, denser in situ National Oceanographic Data Center dataset, the authors have reanalyzed the export characteristics of AAIW from the Southern Ocean into the So...

From a numerical simulation of the Atlantic Ocean, Jochum and Malanotte-Rizzoli provide evidence that the equatorial subsurface countercurrents can be triggered by tropical instability waves through eddy-mean flow interactions in a low-Rossby-number regime. Adapting the transformed Eulerian mean formalism to a shoaling jet, they propose eddy heat f...

The deep equatorial track of the world ocean is subject to intense zonal flow fields that still remain to be better understood. Inertial instability has been invoked to explain some of its features. Here we present possible in situ imprints of such a mechanism in the equatorial Atlantic Ocean below the thermocline. We analyse the observed pattern o...

A fully three-dimensional primitive equation simulation is performed to "reunite" the local equatorial dynamics of the subsurface countercurrents (SCCs) and thermostad with the large-scale tropical ventilated ocean dynamics. It captures (i) the main characteristics of the equatorial thermostad, the SCCs' location and their eastward evolution, and t...

Sensitivity tests are performed to assess the respective influences of the large-scale ventilation and of the near-equatorial winds on the dynamics of the the subsurface countercurrents (SCCs) and thermostad. They show that the intensity of the inertial jets is a function of the potential vorticity (PV) values at subduction and that stronger jets a...

A fully three-dimensional Primitive Equations simulation is performed to ``reunite'' the local equatorial dynamics of the subsurface Counter Currents (SCCs) and thermostad with the large-scale tropical ventilated ocean dynamics. It captures (i) the main characteristics of the equatorial thermostad, the SCCs location and their eastward evolution as...

Uncertainties in the surface wind field have long been recognized as a major limitation in the interpretation of results obtained by oceanic circulation models. Surface winds over the global oceans are measured by scatterometry since ERS-1 launch in August 1991 by the European Space Agency and its follow-on ERS-2 launched in April 1995. Despite the...

The GyroScope project started with the new millennium, on January 2nd, 2001. Nine laboratories in four countries are collaborating to develop a component of an in situ observing system of ocean variability. The project is an initial contribution to the international ARGO project, which plans to deploy a global array of some 3000 autonomous profilin...

Two independent data sets are used to diagnose the wind effect on the mesoscale activity in the North Atlantic Ocean. The oceanic surface variability is described with TOPEX/Poseidon sea surface height measurements from October 1992 to September 1997. Spatial extensions and temporal variations of high mesoscale activity are compared with the zonal...

The motion of fluid contained between two concentric spherical surfaces is analysed in the limit of strong rotation appropriate to large scale flows and arbitrary gap width. To do so, the dynamical equations are written in the natural cylindrical co-ordinate system that gives a central role to the axis of rotation. The case of a homogeneous fluid a...

The effect of the wind on large scale circulation is analysed to locate the different dynamical regimes observed in the ocean on a global scale. It is shown that the wind plays a major role in shaping the circulation of the upper part of the ocean. On the basis of planetary potential vorticity dynamics allowing isopycnals to have large vertical exc...

It is well known that the widely used powerful geostrophic equations that single out the vertical component of the Earth's rotation cease to be valid near the equator. Through a vorticity and an angular momentum analysis on the sphere, we show that if the flow varies on a horizontal scale L smaller than (Ha)1/2 (where H is a vertical scale of motio...

Oceanic Trapped Taylor-Proudman columns by topography

A simple Sverdrup-type two-layer model that allows the outcropping of isopycnals is forced by wind stress, is completed with a frictional western boundary layer, and is investigated along the zero wind-stress curl line separating the subpolar gyre from the subtropical gyre. The study focuses on the different cross-gyre flow patterns. -from Author

Simulations of the wind-driven Ocean circulation, carded out with an eddy-resolving quasi-geostrophic numerical model, and symmetric, idealized wind forcing have a large-scale structure that is predicted wen by the steady nonlinear theory of Rhines and Young. The sharp jet and inertial recirculation am often confined weft inside the region of close...

An interpretation in terms of planetary waves is proposed, which sheds light on the dynamics underlying the large-scale cross-gyre geostrophic flow recently developed in a two-layer ventilated thermocline model. The cross-gyre communication flow is the result of an arrested nondispersive baroclinic Rossby wave in the presence of zonal Sverdrup tran...

Several mechanisms are proposed to explain the northward flow observed at middepth in the eastern North Atlantic. These mechanisms are based on the two forcings that can set the ocean in motion: wind forcing on the one hand, andthermodynamical forcing on the other hand.In the first mechanism that is based on the hypothesis of the ventilated thermocli...

A mechanism is proposed, based on the assumption of ventilation, to explain the middepth northward flow observed in the North Atlantic. The main feature of the solution is that the outcropping line of an intermediate layer at high latitudes is uniquely specified by the condition that the middepth waters of the subtropical gyre may be “sucked up” by...