coupling of the surface and near bottom currents in the gulf of mexico coupling between the surface and near bottom currents in the gulf of mexico gom has been reported in many case studies however geographical variations of this coupling need more examination in this study surface geostrophic currents derived from satellite observed sea surface height and subsurface currents from a collection of deep ocean moorings are used to examine the surface and bottom coupling in different parts of the gom the short period 30 90 days fluctuations generated by the loop current lc and the lc eddies lces have a more vertically coherent structure and stronger deep ocean expressions than the long period fluctuations 90 days in addition the strength of the coupling is modulated by the long period variations of the lc and lce sheddings moreover the surface and bottom coupling varies geographically in the lc region the surface fluctuations along the eastern side of the lc are important in causing the bottom current fluctuations through baroclinic instability under the lc and through traveling topographic rossby waves trws north of the lc in the central deep gom the bottom currents are affected by the upper fluctuations of the northern lc through both local baroclinic instability and remote trw propagation in the northwestern gom the bottom current fluctuations are largely related to the remote surface variability from the west side of the lc by trws propagating northwestward this study will help us better understand mechanisms of the bottom current fluctuations that are important for the dispersal of deep ocean materials and properties

eddy formation near the west coast of greenland abstract this paper extends a bracco and j pedlosky s investigation of the eddy formation mechanism in the eastern labrador sea by including a more realistic depiction of the boundary current the quasigeostrophic model consists of a meridional coastally trapped current with three vertical layers the current configuration and topographic domain are chosen to match as closely as possible the observations of the boundary current and the varying topographic slope along the west greenland coast the role played by the bottom intensified component of the boundary current on the formation of the labrador sea irminger rings is explored consistent with the earlier study a short localized bottom trapped wave is responsible for most of the perturbation energy growth however for the instability to occur in the three layer model the deepest component of the boundary current must be sufficiently strong highlighting the importance of the near bottom flow the model is able to reproduce important features o

analytical and numerical studies of the beta effect in tropical cyclone motion part i zero mean flow abstract the effect on tropical cyclone motion is studied using an analytical as well as a numerical model in a nondivergent barotropic framework the analytical model and the linear version of the numerical model give essentially the same result the linear effect causes a westward stretching of the model vortex but no significant movement of the vortex center an east west asymmetry in the meridional wind field is also created it is the inclusion of the nonlinear term that produces the northwestward movement of the vortex previously found by other investigators e g kitade 1981 this northwestward movement increases with both the maximum wind speed and the radius of maximum wind in a constant shape vortex a wind maximum is also found to the northeast of the vortex which appears to be consistent with the observational findings of shea and gray this asymmetry plays an important role in the vortex motion

loop current and deep eddies abstract in contrast to the loop current and rings much less is known about deep eddies deeper than 1000 m of the gulf of mexico in this paper results from a high resolution numerical model of the gulf are analyzed to explain their origin and how they excite topographic rossby waves trws that disperse energy to the northern slopes of the gulf it is shown that north of campeche bank is a fertile ground for the growth of deep cyclones by baroclinic instability of the loop current the cyclones have horizontal vertical scales of about 100 km 1000 2000 m and swirl speeds 0 3 m s 1 the subsequent development of these cyclones consists of two modes a and b mode a cyclones evolve into the relatively well known frontal eddies that propagate around the loop current mode a cyclone can amplify off the west florida slope and cause the loop current to develop a neck that sometimes leads to shedding of a ring this process is shown to be the loop current s dominant mode of upper to deep variability

mesoscale eddies in the south atlantic bight 1 satellite derived sea level anomaly fields constructed by combining measurements from simultaneously operating altimeters are used to quantify properties and propagation characteristics of eddies in the south atlantic bight sab eddy detection and eddy tracking algorithms are applied to 19 years of high resolution observations available at weekly intervals inshore of the 800 m isobath eddies are most frequently observed at and downstream of the charleston bump a major topographic feature located at 31 32 n a region where the amplitude of most eddies is increased the bump is also a preferred region for eddy generation the amplitude of eddies is found to increase with water depth eddies generated in the sab tend to propagate westward toward the coast and to the northeast presumably due to the influence of the strong mean northeastward flow of the gulf stream those eddies are highly nonlinear with potential to trap water in their interior as they propagate since a large fraction of the eddies that at some point in their histories are found inshore of the 800 m isobath experience large bathymetric changes along their trajectories they can potentially serve as efficient mechanisms for cross isobath transport in the sab analysis of temporal variability in eddy activity suggests that cross isobath transport due to nonlinear eddies may be significant during all seasons but will likely be characterized by large interannual variability

numerical simulation of the gulf stream system the loop current and the deep circulation 1 the loop current and the deep circulation in the gulf of mexico are numerically investigated by a primitive equation sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model a deep cyclonic circulation bounded by the deep basin in the eastern gulf of mexico is spun up by the loop current the deep cyclonic circulation is coincident with a southward current of the loop current eastern limb and weakens after loop current ring separation and cessation of the southward current the anticyclonic semienclosed loop current also induces anticyclonic lower layer columnar eddies in the eastern gulf these lower layer eddies decouple from the upper layer loop current the westward translation speed of a loop current ring is about 2 16 5 18 km d 1 the lower layer eddies have a higher speed and lead the rings into the central gulf the time averaged surface circulation of the gulf of mexico basin is anticyclonic mainly because of the transport of anticyclonic vorticity by loop current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin

generation of topographic waves over the continental margin abstract numerical experiments were carried out to simulate the generation of topographic waves by a gulf stream ring over the continental margin in a stratified ocean on an f plane the study was aimed at understanding the combined effect of density advection and bottom topography on the flow field the momentum equation is linear and nonlinearity is introduced in the density equation the mechanism of wave generation was investigated by turning on and off the nonlinear density advection and by changing the strength of the ring and bottom topography the results show that topographic waves are generated by advection of density in a ring over a sloping bottom the vorticity associated with the swirl velocity of a ring is less important during wave generation the strength of a ring affects the wave amplitude in the case of a strong ring self advection of density may be induced at the surface however the generation and propagation of topographic waves are independent of the strength of the ring waves

lacode a lagrangian two dimensional thermo mechanical code for large strain compressible visco elastic geodynamical modeling abstract we present lacode lagrangian compressible deformation a matlab solver for the stokes equations for compressible non newtonian visco elastic flow in two dimensions based on a lagrangian formulation of the finite element method the incompressible boussinesq approximation is a widespread assumption in numerical models of lithospheric deformation thus potentially masking a significant contribution of mechanisms linked to volumetric changes that occur in the asthenospheric mantle and the lithosphere lacode employs a compressible formulation of the stokes equations designed to address such volume changing processes first we provide a description of the equations governing the deformation of earth rocks and detailed overview of the algorithm its numerical implementation treatment of the non linearities rising from the compressible formulation and ineleastic deformation and the remeshing algorithm that tracks and transfers the physical fields from a highly distorted mesh to a high quality one lacode is then benchmarked by comparing numerical results to analytical solutions for the bending of a thin elastic beam under a constant uniform load flow around a rigid inclusion rayleigh taylor instability stress build up in a visco elastic maxwell body and couette flow with viscous heating the rayleigh taylor instability test is further used to demonstrate the accuracy of the remeshing algorithm the importance of including volumetric strain for geodynamic processes is illustrated by two numerical experiments i volumetric strain inducing phase changes in amagmatic slow spreading ridges and ii subducting slabs

hydrographic and current observations on the continental slope and shelf of the western equatorial atlantic abstract hydrographic and current profiling data from december 1980 and current meter data obtained between september 1980 and november 1981 from the continental slope and shelf of the western equatorial atlantic between 2 and 7 n are used to describe the character of the north brazil coastal current nbcc system hydrographic data and the profiling results show that the nbcc has three distinct branches during the boreal fall in the near surface a strong current flows northwestward parallel to the coast at least as far as 6 n current speed within the near surface nbcc over a one year period were between 75 and 250 cm s 1 while the transport in december 1980 was between 15 and 20 106 m3 s 1 there was a southeastward near surface flow farther offshore which appears to be the return of the nbcc the ultimate destination of which is the north equatorial countercurrent offshore of the southeastward flow was a portion of a low salinity lens of amazon water the waters within and below the thermocline

the interaction of a two layer isolated mesoscale eddy with bottom topography abstract the propagation of an isolated mesoscale eddy onto a western bounding topographic slope is examined through the use of a two layer primitive equation numerical model variable parameters in the study are sense of rotation cyclonic anticyclonic vertical structure baroclinic barotropic and layer thickness ratio h1 h2 eddy size and strength rotational velocity and frictional parameterization are fixed dispersion in the isolated eddy is induced by planetary and topographic beta effects giving the eddy an asymmetric distribution this asymmetric distribution allows for nonlinear self advective propagation tendencies these nonlinear tendencies play a key role in the direction of propagation of the eddy specifically in a quiescient background an anticyclone can have eastward propagation tendencies which can overcome planetary and topographic beta effects conversely cyclones can have westward propagation velocities which are augmented greater than maximum rossby wave phase speed b

topographic rossby waves in the gulf of mexico abstract observations of topographic rossby waves trw using moored current meters bottom pressure gauges and lagrangian rafos floats are investigated for the deep basin of the gulf of mexico recent extensive measurement programs in many parts of the deep gulf which were inspired by oil and gas industry explorations into ever deeper water allow more comprehensive analyses of the propagation and dissipation of these deep planetary waves the gulf of mexico circulation can be divided into two layers with the 800 1200 m upper layer being dominated by the loop current lc pulsations and shedding of large diameters 300 400 km anticyclonic eddies in the east and the translation of these lc eddies across the basin to the west these processes spawn smaller eddies of both signs through instabilities and interactions with topography and other eddies to produce energetic surface layer flows that have a rich spectrum of orbit periods and diameters in contrast current variability below 1000 m often has the characteristics of trws with periods ranging from 10 100 days and wavelengths of 50 200 km showing almost depth independent or slightly bottom intensified currents through the weakly stratified lower water column these fluctuations are largely uncorrelated with simultaneous upper layer eddy flows trws must be generated through energy transfer from the upper layer eddies to the lower layer by potential vorticity adjustments to changing depths of the bottom and the interface between the layers therefore the lc and lc eddies are prime candidates as has been suggested by some model studies model simulations have also indicated that deep lower layer eddies may be generated by the lc and lc eddy shedding processes in the eastern gulf the highest observed lower layer kinetic energy was north of the campeche bank under the lc in a region that models have identified as having strong baroclinic instabilities part of the 60 day trw signal propagates towards the sigsbee escarpment a steep slope at the base of the northern continental slope and the rest into the southern part of the eastern basin higher energy is observed along the escarpment between 89 w and 92 w than either under the northern part of the lc or further south in the deep basin because of radiating trws from the western side of the lc in the northern part of the lc evidence was found in the observations that 20 30 day trws were connected with the upper layer through coherent signals of relative vorticity the 90 phase lead of the lower over the upper layer relative vorticity was consistent with baroclinic instability along the sigsbee escarpment the trws are refracted and reflected so that little energy reaches the lower continental slope and a substantial mean flow is generated above the steepest part of the escarpment rafos float tracks show that this mean flow continues along the escarpment to the west and into mexican waters this seems to be a principal pathway for deepwater parcels to be transported westward away from the slope rafos floats tend to oscillate in the same general area as if primarily responding to the deep wave field little evidence of westward translating lower layer eddies was found in both the float tracks and the moored currents in the western gulf the highest deep energy levels are much less than in the central gulf and are found seaward of the base of the slope otherwise the situation is similar with trws propagating towards the slope probably generated by the local upper layer complex eddy field being reflected and forcing a southward mean flow along the base of the mexican slope amplitudes of the lower layer fluctuations decay from the northwest corner towards the south

on the influence of bottom topography on the agulhas eddy abstract a series of numerical experiments with a two layer primitive equation model is presented to study the dynamics of agulhas eddies the main goal of the paper is to examine the influence of an underwater meridional ridge modeled after the walvis ridge on an agulhas eddy hitting it first the propagation of an eddy of the specified vertical structure over a flat bottom is considered varying the initial eddy horizontal scale from 40 to 120 km unlike small nonlinear eddies large nonlinear eddies on the scale of agulhas eddies do not rapidly evolve into a compensated state no motion in the lower layer second the influence of a ridge on eddies of differing vertical structures having a specified intensity in the upper layer and a prescribed horizontal scale is analyzed significantly baroclinic eddies can cross the walvis ridge but barotropic or near barotropic ones cannot the evolution of eddies crossing the ridge is compared with that of initially identical eddies moving over a flat botto

stable and unstable vortices attached to seamounts we examine the properties of stationary barotropic flows over isolated topographic features such as seamounts according to a general variational principle flows that maximize or minimize the energy in a set of isovortical flows are stationary and stable using this it is shown that a large class of stable and stationary attached anticyclones exists at a seamount those with positive potential vorticity pv are maximum energy states while those with negative pv are minimum energy states if the seamount is circular there are also stable attached cyclones but these are destabilized by irregularities in the topographic shape unlike the anticyclones numerical simulations broadly support these theoretical predictions but also highlight the importance of time dependent processes particularly in cases in which the vortex collides with the seamount

hydrography of the gulf of mexico using autonomous floats abstractfourteen autonomous profiling floats equipped with ctds were deployed in the deep eastern and western basins of the gulf of mexico over a four year interval july 2011 august 2015 produ

a greenland sea perspective on the dynamics of postconvective eddies open ocean deep postconvection contributes to the formation of the dense waters that fill the global deep ocean the dynamics of postconvective vortices are key to understanding the role of convection in ocean circulation submesoscale coherent vortices scvs observed in convective regions are likely to be the anticyclonic components of hetons hetons are dipoles consisting of a surface cyclone and a weakly stratified subsurface anticyclone that can be formed by convection here key postconvective processes are investigated using numerical experiments of increasing sophistication with two primary goals 1 to understand how the ambient hydrography and topography influence the propagation of hetons and 2 to provide a theoretical context for recent observations of scvs in the greenland sea it is found that the alignment of hetons is controlled by ambient horizontal density gradients and that hetons self propagate into lighter waters as a result this provides a mechanism for transporting convected water out of a cyclonic gyre but the propagation is arrested if the heton meets large amplitude topography upon interaction with topography hetons usually separate and the surface cyclone returns toward denser water the anticyclone usually remains close to topography and may become trapped for several hundred days these findings may explain the observed accumulation and longevity of scvs at the greenland fracture zone on the rim of the greenland sea gyre the separation and sorting of cyclones from anticyclones have likely implications for the density and vorticity budgets of convective regions

observations of the labrador sea eddy field this paper is an observational study of small scale coherent eddies in the labrador sea a region of dense water formation thought to be of considerable importance to the north atlantic overturning circulation numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat yet their small size has hindered observational progress a large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms current meter moorings and satellite altimetry details of the current and water mass structure of individual eddy events as they are swept past by an advecting flow can then be extracted from the mooring data a transition is seen during mid 1997 with long lived boundary current eddies dominating the central labrador sea year round after this time and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time the topex poseidon altimeter covers the labrador sea with a loose net of observations through which coherent eddies can seem to appear and disappear by concentrating on locating and describing anomalous events in individual altimeter tracks a portrait of the spatial and temporal variability of the underlying eddy field can be constructed the altimeter results reveal an annual pulsation of energy and of coherent eddies originating during the late fall at a particular location in the boundary current pinpointing the time and place of the boundary current type eddy formation the interannual variability seen at the mooring is reproduced but the mooring site is found to be within a localized region of greatly enhanced eddy activity notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling these eddy observations as well as hydrographic evidence suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region

dominant circulation patterns of the deep gulf of mexico abstractthe large scale circulation of the bottom layer of the gulf of mexico is analyzed with special attention to the historically least studied western basin the analysis is based on 4 years o

the loop current observations of deep eddies and topographic waves abstracta set of float trajectories deployed at 1500 and 2500 m depths throughout the deep gulf of mexico from 2011 to 2015 are analyzed for mesoscale processes under the loop current lc in t

ocean circulation connecting fram strait to glaciers off northeast greenland mean flows topographic rossby waves and their forcing abstractfrom 2014 through 2016 we instrumented the 80 km wide norske trough near 78 n latitude that cuts across the 250 km wide shelf from fram strait to the coast our measurements resolve a 10

erosion of a surface vortex by a seamount abstract numerical experiments are carried out on the f plane using a shallow water isopycnal model to analyze the behavior of a surface intensified anticyclonic vortex when it encounters an isolated seamount the advection by the vortex of deep fluid parcels across the isobaths is known to generate deep anticyclonic and cyclonic circulations above and near the bathymetry respectively these circulations are shown to exert a strong shear on the upper layers which causes an erosion of the initial vortex by filamentation the erosion often results in a subdivision of the eddy while the eroded original structure forms a dipole with the deep cyclone and is advected away the filaments torn off from the original core aggregate into a new eddy above the seamount splitting in more than two structures is sometimes observed the erosion process is quantified by the bulk volume integral of the eddy potential vorticity anomaly a sensitivity study to different parameters of the configuration distance between

topographic effects on the path and evolution of loop current eddies 1 eddy topography et interactions are important in determining the path and evolution of oceanic eddies including loop current eddies lce in the gulf of mexico gom we use the hybrid coordinate ocean model and satellite altimetry data to investigate the et interactions and the impact on lce pathway evolution in the gom satellite altimetry reveals that lces translate dominantly westward in the central gom and strongly collide and reflect against topography near the continental slope in the northern and western gom the result is the frequent generation of an anticyclone cyclone ac pair in conjunction with the lces in the absence of lateral or surface boundary forcing but including realistic topography simulations initialized with idealized eddies at various locations in the gom reveal the following results southward eddy reflection from the northern slope occurs when a cyclone drastically strengthens east of the anticyclone because of the et collision the prevailing westward propagation in the central gom occurs because the cyclone is very dispersive toward nearby topographic features causing a reduced southward component of drift and or moves to the south forming a meridional ac pair causing an enhanced westward component et collision is strongest over the northwestern slope north of 24 n because of the eddy colliding relatively normal to the steep slope and the eddy typically tracks anticyclonic pathways during the collision reflection process along the western slope a strong et collision produces a southeastward reflection and the accompanying cyclone to the northeast strongly enhances the reflection near the southern gom slope eddy pathways tend to propagate alongslope with an onshore offshore oscillatory trajectory because of the competition between topographic and planetary effects in the southwestern gom a bimodal pathway occurs i e northward migration with an anticyclonic route for relatively stronger eddies and southward dissipative propagation along the shelf edge for weaker ones

tracking three meddies with sofar floats abstract three meddies were tracked for up to two years in the canary basin using neutrally buoyant sofar floats these meddies have cores of warm salty mediterranean water and are approximately 100 km in diameter 800 m thick and are centered at a depth of 1100 m meddy 1 was tracked for two years 1984 86 with five floats as it drifted 1090 km southward with a mean velocity of 1 8 cm s 1 four shipboard surveys made during these two years revealed the nearly total decay of meddy 1 by gradual mixing processes meddy 2 drifted 530 km southwestward over 8 5 months with a mean velocity of 2 3 cm s 1 until it collided with hyeres seamount near 31 n 29 w the floats trapped in this meddy then stopped looping abruptly implying a major disruption of this meddy meddy 3 drifted 500 km southwestward for a year and a half with a mean translation velocity of 1 1 cm s 1 a comparison of the velocity of meddies to the velocity of nearby floats at 1100 m depth outside of the meddies shows clearly that all three m

buoyancy arrest and shelf ocean exchange when steady flow in a stratified ocean passes between the continental slope and open ocean its ability to cross isobaths is potentially limited by buoyancy arrest if the bottom ekman transport vanishes and there are no interior stresses then steady linear flow on an f plane must be geostrophic and follow isobaths exactly the influence of arrest on cross shelf transport is investigated here to establish 1 whether there are substantial penetration asymmetries between cases with upwelling and downwelling in the bottom boundary layer 2 over what spatial scales hence in what parameter regime buoyancy arrest is important and 3 the effects of depth dependent interior flow the problem is approached using scalings and idealized numerical models the results show that there is little or no asymmetry introduced by bottom boundary layer behavior further if the stratification is weak or moderate as measured by a slope burger number s 5 an f where a is the bottom slope n is buoyancy frequency and f is the coriolis parameter buoyancy arrest does not exert a strong constraint on cross isobath exchange

some aspects of vortex structure related to tropical cyclone motion abstract some effect of tropical cyclone structure on the vortex motion are examined in a nondivergent barotropic numerical model with no basic current as suggested earlier by demaria the initial maximum wind speed has little effect on the track vortex translation associated with the beta effect depends sensitively on the strength of the flow between 300 and 1000 km from the center if the flow in this annulus is made more cyclonic the track will turn cyclonically and move more toward the west in the northern hemisphere the dynamics of this beta drift is studied via a decomposition into symmetric and asymmetric circulations the symmetric flow experiences a slight weakening of the maximum wind speed and an anticyclonic circulation is induced beyond 600 km the asymmetric circulation is dominated by an azimuthal wavenumber one circulation with an anticyclonic gyre east of the center a cyclonic gyre to the west and a nearly uniform broad scale ventilation flow between the gyres the vortex translati

coherent baroclinic eddies on a sloping bottom a coherent and stable baroclinic eddy in a rotating fluid was produced on a sloping bottom by releasing a dome of salt water into the ambient fresh water a strong cyclonic vortex is produced above the heavy dome the entire eddy system moves north westward with the up slope direction designated north as a taylor column the eddy system displays long lifetimes but it is shown that a theory of isolated systems cannot account for the experimental observations instead it is demonstrated that the vortex flow above the lens is along the lines of constant depth producing a net pressure force on the lens which approximately balances the buoyancy force when ekman friction is also included it accounts for the northward motion of the dome

interaction of barotropic vortices with coastal topography laboratory experiments and numerical simulations the interaction of a barotropic cyclonic vortex on a b plane with a strong topographic slope is studied by means of laboratory experiments and numerical simulations in the laboratory the vortex is produced in a rectangular rotating tank with a weak uniformly sloping bottom slope angle 3 58 in order to simulate the b effect the cyclonic vortex moves in the northwestward direction and interacts with an additional pronounced linear topography slope angle 358 along the western boundary of the tank the laboratory experiments revealed that the original northwestward trajectory changes to the south until the vortex is dissipated by viscous effects and bottom friction as it moves upslope the exterior ring of the vortex forms a strong current to the northeast from this current a new cyclonic vortex is created repeating approximately the behavior of the original one later two more vortices are formed in the same way a finite difference numerical model is used to solve the nondivergent barotropic equation despite the presence of the strong slope agreement between laboratory results and numerical runs suggests that conservation of potential vorticity is indeed the basic mechanism involved in the southward motion of the vortex and the northeastward meandering current

velocity and hydrographic structure of two gulf of mexico warm core rings results from an extensive survey of two gulf of mexico warm core rings are presented the data were taken during a 1 week period in december 1983 using a shipboard acoustic doppler current profiler adcp expendable current probes xcp expendable bathythermographs xbt and a ctd two rings were observed an older one in the western gulf adjacent to the west texas shelf and one just separated from the loop current the western ring was of order 200 km in diameter with peak currents of 1 m s 1 at the 100 m level water properties were uniform and characteristic of the high salinity caribbean subtropical underwater the eastern ring was of order 300 km in diameter with peak currents of near 2 m s 1 at the 100 m level water below 200 m is of caribbean origin while the surface waters show more variability suggesting some inflow of gulf of mexico common water the evolution of the rings is also described based on the cruise measurements satellite avhrr and other observations of opportunity

eruption of alkali basalts during crustal shortening in southern california the common occurrence of alkali basalts in continental rifts has led to the widespread assumption that late cenozoic alkali basalts of the western united states indicate an extensional tectonic regime however field relations of late cenozoic alkali basalt flows and cinder cones in the mojave desert area including flows that bear mantle xenoliths indicate that many were erupted in contractional or transpressional tectonic settings these observations call into question models of extensional magmatism in which lithospheric extension facilitates transport of magmas to the surface and suggest that an association of alkali basalts and coarse clastic sedimentary rocks need not indicate rifting

a geostrophic vortex over a slope abstract nonlinear quasigeostrophic f plane vortices in two layers over a topographic slope are considered scaling arguments suggest two parameters that dictate the effective strength of the slope the first indicates the likelihood of dispersion at depth and the second relates to baroclinic stability if the deep flow is only weakly dispersive weak slopes an initially barotropic vortex can translate barotropically across the isobaths provided the vortex scale exceeds the deformation scale over stronger slopes the vortex separates into topographic waves and a stationary surface trapped vortex an initially surface trapped vortex larger than deformation scale becomes unstable over a weak slope as it does over a flat bottom however a strong slope can stabilize the vortex to small perturbations despite the large vortex scale the effective slope parameters depend not only on topographic grade but on vortex strength and size and on the ambient stratification parameters obtained with represen

the prevalence of oceanic surface modes satellite observations have revolutionized oceanography capturing diverse phenomena over much of the globe however it remains to understand how surface fields like sea surface height reflect the motion occurring at depth the vertical structure of ocean eddies is often expressed in terms of baroclinic modes which are basis functions derived assuming a flat ocean bottom bathymetry alters the modes though weakening the bottom velocities using analytical solutions we demonstrate that with realistic bathymetry and or bottom friction the bottom velocities are nearly zero the resulting surface modes should be ubiquitous in the ocean this would explain the dominant mode of variability obtained from globally distributed current meter data and is consistent with energy spectra derived from sea surface height data the results yield a simple way to infer subsurface velocities from satellite data and suggest that ocean analyses should be made in terms of surface modes and topographic waves