paleomagnetic dating of sulfide mineralization and cap rock formation in gulf coast salt domes remnant magnetization of stratiform sulfides within salt dome cap rocks provides a means of dating the timing of mineralization and its relationship with tectonic sedimentation and fluid evolution events within the local basin the winnfield salt dome in northern louisiana hosts stratiform laminae of pyrrhotite and other sulfides in anhydrite cap rock detailed paleomagnetic analyses indicate the presence of numerous magnetic reversals that can be correlated with the sea floor magnetic anomaly sequence thus providing the first direct determination of a salt dome cap rock formation age the sampled section that represents about two thirds of the total anhydrite thickness formed between 157 and 145 ma latest jurassic accumulation rates calculated from these data indicate that the average rate for the oldest cap rock sampled is 5 7 m m y and decreases to 2 8 m m y for the younger strata the winnfield diapiric salt contains about 3 anhydrite indicating the diapir growth rate was at least 30 times faster a figure that is compatible with independent geologic estimates the best documented cap rock hosted sulfide concentrations occur at the hockley salt dome in south central texas hockley is a relatively young diapir with the cap rock believed to have developed within the last 45 ma sulfidesmore occur throughout the 285 m thick cap rock but major metal concentrations occur within a 20 m zone within the central cap rock stratigraphy if this zone formed at comparable rates to the winnfield cap rock then the main pulse of hockley mineralization lasted only a few million years paleomagnetic studies are in progress to constrain timing of mineralization of hockley less

structure of the mediterranean undercurrent and mediterranean water spreading around the southwestern iberian peninsula 1 rafos float and hydrographic data are analyzed to investigate the pathways rates and mechanisms of mediterranean water mw spreading into the north atlantic from the gulf of cadiz with an emphasis on processes other than meddies we find that the transition of the mediterranean outflow from a density current to an intermediate depth jet occurs as it enters portimao canyon south of portugal due to rapidly steepening topography and associated turbulent entrainment this feature was not seen in recent plume model simulations due to their use of smoothed topography in addition to the traditional lower salinity maximum or core a denser deeper continuous vein of mw was also traceable from portimao canyon to cape st vincent the mean velocity structure of the mediterranean undercurrent changes from a 30 km wide jet with peak mean westward speed of 0 2 m s 1 along the southern iberian slope to a broader much weaker northward flow with maximum mean speed of only 0 06 m s 1 along the western iberian slope due in part to changes in the bottom slope lower core mw spread mainly 1 southward into the interior gulf of cadiz 2 northward along the western iberian slope and 3 westward into the deep tagus abyssal plain the average spreading rate was 0 01 0 02 m s 1 toward the west northwest direction meddies forming near the slope were found to have an indirect but profound impact on mw spreading often diverting mw approaching from upstream into the interior the results are compared to recent hydrography based studies of mw spreading pathways

meddies in the mercator north atlantic and mediterranean sea eddy resolving model the new generation of high resolution ocean models offers a new way to investigate the characteristics and the evolution of the ocean mesoscale an analysis of the simulated mediterranean eddies the so called meddies is presented the model used in this study is the mercator north atlantic 9 n 70 n and mediterranean sea prototype pam a high resolution configuration 3 5 8 km horizontal grid based on the opa ocean general circulation model the meddies are coherent structures of warm and salt mediterranean water mw advected in the northeast atlantic a 5 year experiment performed with pam reproduced the main observed characteristics of the meddies thermohaline properties 11 8 c 36 psu sizes radius between 25 and 110 km thickness between 500 and 1000 m westward advection velocities 1 4 cm s 1 angular velocities a period of 20 days a good estimate of the number of meddies in the northeast atlantic 22 and their realistic geographical distribution 80 south of 40 n moreover and in agreement with a previous study based on an observation cruise these modeled meddies represent half of the westward salinity transport of mw

arms winding around a meddy seen in seismic reflection data close to the morocco coastline the north atlantic temperature and salinity distributions are strongly influenced by the existence of mediterranean eddies meddies which significantly contribute to the transport of the warm and salty mediterranean water along different pathways the most common pathways are observed to be north and west of the canary current however a 2011 seismic reflection cruise conducted by bgr and ifremer near the north western african margin of morocco mirror leg 2 revealed the presence of a meddy south of the azores front and very close to the morocco coastline this unusual location of a strong mediterranean water anomaly is confirmed by other data moreover meddies are long lived structures whose dynamics and dissipation are not yet completely understood recently theoretical studies have revealed critical level baroclinic instabilities of compact lens like vortices this theory supports the slow growth of azimuthal eigenmodes along critical surfaces which leads to the formation of arms winding around the vortex developing sharp internal fronts these structures are very thin and spatially intermittent and are identified for the first time in a seismic dataset this is made possible by the length of seismic sections at high lateral resolution citation menesguen c b l hua x carton f klingelhoefer p schnurle and c reichert 2012 arms winding around a meddy seen in seismic reflection data close to the morocco coastline geophys res lett 39 l05604 doi 10 1029 2011gl050798

the merger of geophysical vortices at finite rossby and froude number partial support for this research has come from the uk engineering and physical sciences research council grant number ep h001794 1

a census of meddies in a long term high resolution simulation the output from a high resolution two decade long mediterranean outflow simulation is analysed here to provide a census of mediterranean water eddies aka meddies both anticyclones and cyclones the formation rate of meddies that survive for at least 90 days is of 12 meddies yr 1 of which 12 are cyclones the rate of formation reaches 40 meddies yr 1 30 cyclones when considering all the meddies living over 15 days about 70 of the population is born along the southwestern iberian slope but several robust meddies also originate in points of convergence of the main pathways into the open ocean the longest lived meddies propagate northwestwards but most of the anticyclones veer southwestwards after a while as the meddies drift away from their birthplace their radius tends to increase gradually from 15 to 30 km the thickness depth difference between isopycnals 27 2 and 27 5 of anticyclones born near cape st vincent contracts by approximately 100 m after travelling 1000 km from their source their mean swirl velocities range from about 21 cm s 1 at z 1000 m up to 27 cm s 1 at z 600 m mean salinity and temperature anomalies are significantly lower for cyclones which in general are also more slowly rotating shallower and thinner than anticyclones cyclones are more easily tracked at 600 m depth where longer trajectories are recorded in the vicinity of portimao canyon cyclones outnumber anticyclones while the reverse happens downstream of cape st vincent

surface circulation in the gulf of cadiz model and mean flow structure 1 the mean flow structure of the gulf of cadiz is studied using a numerical model the model consists of a set of one way nested configurations attaining resolutions on the order of 2 6 km in the region of the gulf of cadiz in the large scale configuration the entrainment of the mediterranean water is parameterized implicitly through a nudging term in medium and small scale nested configurations the mediterranean outflow is introduced explicitly the model reproduces all the known features of the azores current and of the circulation inside the gulf of cadiz a realistic mediterranean undercurrent is generated and meddies develop at proper depths on the southwest tip of the iberian slope the hypothesis that the azores current may generate in association with the mediterranean outflow plume theories is confirmed by the model results the time mean flow is dominated by a cyclonic cell generated in the gulf which expands westward and has transports ranging from 4 to 5 sv the connection between the cell and the azores current is analyzed at the scale of the gulf the time mean flow cell is composed by the westward mediterranean undercurrent and by a counterflow running eastward over the outer edge of the mediterranean undercurrent deeper vein as the latter is forced downslope this counterflow feeds the entrainment at the depths of the mediterranean undercurrent and the atlantic inflow at shallower levels coastward and upslope of this recirculation cell a second current running equatorward all the way along the northern part of the gulf is revealed this current is a very robust model result that promotes continuity between the southwestern iberian coast and the strait of gibraltar and helps explain many observations and recurrent sst features of the gulf of cadiz

a census of meddies tracked by floats recent subsurface float measurements in 27 mediterranean water eddies meddies in the atlantic are grouped together to reveal new information about the pathways of these energetic eddies and how they are often modified and possibly destroyed by collisions with seamounts twenty meddies were tracked in the iberian basin west of portugal seven in the canary basin during february 1994 14 meddies were simultaneously observed 11 of them in the iberian basin most 69 of the newly formed meddies in the iberian basin translated southwestward into the vicinity of the horseshoe seamounts and probably collided with them some meddies 31 passed around the northern side of the seamounts and translated southwestward at a typical velocity of 2 0 cm s into the canary basin some meddies observed there were estimated to be up to 5 yr old four meddies in the canary basin collided with the great meteor seamounts and three meddies were inferred to have been destroyed by the collision overall an estimated 90 of meddies collided with major seamounts the mean time from meddy formation to a collision with a major seamount was estimated to be around 1 7 yr combined with the estimated meddy formation rate of 17 meddies yr from previous work this suggests that around 29 meddies co exist in the north atlantic therefore during february 1994 we observed about half of the population of meddies

cyclones and anticyclones in seismic imaging 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 mw cyclones using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion it is shown that after a stable state is reached both anticyclones and cyclones display similar patterns of layering stacked thin layers of high acoustic reflectivity located above and below the core of each vortex which do not match isopycnals the authors conclude that it should not be possible to distinguish between mw cyclones and anticyclones based on their signature in seismic imaging alone complementary information is needed to determine the sense of rotation

three dimensional interface modelling with two dimensional seismic data the alpine crust mantle boundary summary we present a new approach to determine the 3 d topography and lateral continuity of seismic interfaces using 2 d derived controlled source seismic reflector data the aim of the approach is to give the simplest possible structure consistent with all reflector data and error estimates we define simplicity of seismic interfaces by the degree of interface continuity i e shortest length of ovsets and by the degree of interface roughness least surface roughness the method is applied to structural information of the crust mantle boundary moho obtained from over 250 controlled source seismic reflection and refraction profiles in the greater alpine region the reflected and refracted phases from the moho interface and their interpretation regarding crustal thickness are reviewed and their reliability weighted weights assigned to each reflector element are transformed to depth errors considering fresnel volumes the 2 d derived reflector elements are relocated in space 3 d migration and interpolation is performed between the observed reflector elements to obtain continuity of model parameters interface ovsets are introduced only where required according to the principle of simplicity the resulting 3 d model of the alpine crust mantle boundary shows two ovsets that divide the interface into a european an adriatic and a ligurian moho with the european moho subducting below the adriatic moho and with the adriatic moho underthrusting the ligurian moho each sub interface depicts the smoothest possible i e simplest surface fitting the reflector data within their assigned errors the results are consistent with previous studies for those regions with dense and reliable controlledsource seismic data the newly derived alpine moho interface however surpasses earlier studies by its lateral extent over an area of about 600 km by 600 km by quantifying reliability estimates along the interface and by obeying the principle of being consistently as simple as possible

zonal structure of the mean flow and eddies in the azores current system 1 the surface circulation and eddy field from the azores current system are studied here by analyzing surface drifters records and altimetry maps collected over more than 16 years clear differences in mean flow and eddy characteristics allow for a classification of the azores current in three zonal sectors west of 30 w between the mid atlantic ridge and the hyeres atlantis seamount system between 30 w and the longitude of madeira and east of madeira a detailed and quantitative characterization of each sector is given the transition between the western and central parts is controlled by the hyeres atlantis ridge in the transition to the eastern sector there is a change in the dynamics and the flow is forced by the cyclonic recirculation driven by the mediterranean outflow there is no clear expression of a continuous surface northern counterflow but three distinct westward flows are seen one along the southeastern border of the azores plateau another one southwest of madeira and a third one along 31 n west of the hyeres seamount no clear tilt in the axis of the azores current is found in the calculated mean surface flow from surface drifters observations from both drifters and altimetry data show that anticyclonic features dominate in the northern region whereas cyclonic ones dominate in the southern region overall cyclones are more numerous constituting 60 of large eddies the eddy features detected in the west tend to be larger than those in the east both in size and sea level anomaly there is indication of different mean propagation speeds east and west of 25 w 30 w with the mean speeds consistently increasing by 25 45 in the west estimates for the rate of formation of strong eddies range from 1 4 to 2 4 year 1 for cyclones and 1 2 to 1 7 year 1 for anticyclones

observations and numerical modelling of the mediterranean outflow splitting and eddy generation during the canigo project the generation of dipolar eddies in the mediterranean water mw layers off south portugal was recorded by subsurface floats from february to november 1998 the role of the bottom topography on the spreading of the mw in the gulf of cadiz and on the generation of these mw eddies was studied in the framework of the medtop project some of the hydrological and velocity observations collected during medtop in 2001 and 2002 also revealed the association of anticyclones meddies and cyclones in the region just south of the portimao canyon the evolution of these structures is studied with subsurface floats deployed in the vortices the splitting of the mw plume in the gulf of cadiz and the generation mechanisms of the mw vortices in the region from portimao canyon to the estremadura promontory are investigated using a bottom following numerical primitive equations model in a regional ocean configuration incorporating the realistic topography of the iberian continental slope the model reproduces the mw division into different cores in the gulf of cadiz as well as the generation of baroclinic dipoles downstream of portimao canyon the role of the bottom topography in the eddy generation process is discussed

a numerical study on the successive formation of meddy like lenses 1 we present a process study on the sustaining mechanism of lens formation using a series of numerical experiments of a density current over a sloping bottom with a cape along the coastline water parcels in the bottom density current are shed into the offshore region leading to periodic formation of anticyclonic lenses as part of baroclinic dipolar vortices the cyclonic partner is more prominent at the surface and the coupled vortices are carried by the mean current established in the offshore region parameter dependence of dipole generation is examined which suggests that the background current is necessary for the detached eddies to be coherent in the downstream direction and for shedding events to repeat nof and pichevin 1996 it is also shown that the density mixing of the bottom current provides criteria for cyclogenesis at the sea surface a detailed analysis is given by a five layer model forced by a water mass source sink which reproduces the baroclinic dipolar vortices similar to those observed in the preceding z coordinate model we find that the dipole generation is due to the finite amplitude divergence convergence of the baroclinic current passing the cape stern and chassignet 2000 the overall analyses suggest three necessary conditions for successive eddy formation 1 a localized variation in the coastline causing the finite amplitude disturbance 2 mixing of mediterranean water with the surrounding fluids leading to anticyclonic rotation of meddies as well as cyclogenesis at the surface and 3 background currents that advect the detached vortices out of the source region index terms 4255 oceanography general numerical modeling 4219 oceanography general continental shelf processes 4520 oceanography physical eddies and mesoscale processes 4528 oceanography physical fronts and jets keywords eddy shedding dense water plume numerical simulation

evidence of time mean cyclonic cell southwest of iberian peninsula the mediterranean outflow driven β plume 1 first observational evidence of time mean cyclonic recirculation southwest of iberia is presented data sets of hydrography satellite altimetry and surface drifters velocities are analyzed jointly in order to obtain an accurate time averaged circulation in the mid latitude northeast atlantic off the gulf of cadiz a cyclonic recirculation cell with characteristics similar to those predicted by theoretical and modeling studies is detected in all computed velocity fields the cell in the upper 1000 m layer exhibits transports of 3 to 4 sv that are only slightly smaller than the model transports the cell is centered at approximately 36 n 10 w is elongated zonally and extends to 15 w westwards wind driven sverdrup transport and plume dynamics are both suggested to play a role in the generation of the cyclonic cell but the relative contribution of these effects is yet to be clarified the core of the recirculation appears compact and the magnitude of the cell fades westwards much faster than predicted by the theoretical and modeling studies considered

meddy dynamics and interaction with neighboring eddies southwest of portugal observations and modeling 1 during the semane 2000 experiment southwest of portugal two meddies were found in near contact these meddies had hydrological radii of about 20 and 30 km thickness of 900 m maximum temperatures of 12 45 c and 13 45 c and maximum salinities of 36 52 and 36 78 the smaller meddy with more pronounced thermohaline anomalies was clearly double cored at 750 and 1300 m depths while the wider one was more diffuse and more homogeneous the associated geostrophic velocities referenced at 2000 m locally reached 0 5 m s in the smaller meddy and 0 2 m s in the wider one three rafos floats and two deep drogued surface drifters seeded in the two meddies rapidly gathered in the more intense meddy this meddy trajectory revealed by the float motion was first eastward then southward maps of sea level anomaly indicate that this motion did not correspond to the long term evolution of the initial positive sea level anomaly signature of the meddies and that neighboring cyclones must have played a role in the meddy evolution to determine the role of each eddy in the observed evolution several scenarios were studied with a three layer quasi geostrophic numerical model the interaction of two meddies in isolation did not result in the observed meddy trajectories on the long term the interaction of these two meddies with successive neighboring cyclones provided a more realistic trajectory of the meddy containing the floats

real time tracking of a galician meddy we describe the properties and displacement of the northernmost meddy that has ever been studied this meddy was found to the northwest of the iberian peninsula in april 1997 its hydrological properties suggest that it was born offshore galicia the northwestern corner of spain it was tracked in real time for more than one year using recent types of deep drogued buoys and lagrangian floats and remained quasi stationary for an unusually long period of 11 months around 45 n 12 w

an analysis of the evolution of meddies in the north atlantic using floats and multisensor satellite data previous studies focusing on the remote detection of mediterranean eddies meddies have reported that the isopycnal surface changes derived from satellite multisensor measurements at the approximate depth of 400 m can be used to sense the presence of underlying meddies while the isopycnal surface near that depth does indeed reveal the locations of meddies an analysis of isopycnal surface changes in response to the evolution of meddies has yet to be made accordingly this research focuses on analyzing the relationship between isopycnal surface changes and the evolution of meddies the vertical isopycnal surface variability of meddies which is directly related to contributions from rotational velocity interior thermal variation and vertical displacement of meddies is observed and studied using float observations from a mediterranean undercurrent seeding experiment amuse the contributions of each of the three aforementioned parameters are estimated enabling us to understand their relative role in changing the isopycnal surface above meddies furthermore in order to further understand meddies evolution and their associated forcing the dominant frequencies of their horizontal and vertical displacements as well as the sea surface height variability above the meddy are analyzed using the hilbert huang transform finally the horizontal and the vertical eddy viscosity dissipation of meddies is computed and compared with a theoretical model the empirical horizontal and the vertical eddy viscosities are found to be 7 106 cm2 s 1 and 200 cm2 s 1 respectively this study will therefore contribute to understanding how the isopycnal surface is related to the presence of meddies what frequencies dominate its variability and the values of eddy viscosity which can be used for a numerical model

eddy generation in the mediterranean undercurrent abstract in the framework of the european union mast iii project canary islands gibraltar azores observations 24 rafos floats were deployed in the mediterranean water mw undercurrent off south portugal between september 1997 and september 1998 a preliminary analysis of this lagrangian approach complemented with xbt and current meter data show some of the major aspects of the flow associated with the undercurrent as well as associated eddy activity floats that stayed in the undercurrent featured a downstream deceleration and a steering by bottom topography three meddy formations at cape st vincent could be isolated from the float data the dynamical coupling of meddies and cyclones was observed for a considerable period of time the generation of two dipolar structures in the portimao canyon region also was observed with the float data a major bathymetric relief gorringe bank was not only an important constraint to the eddy trajectories and of the flow at the mw levels but also a site for meddy formation

properties and pathways of mediterranean water eddies in the atlantic abstract data from ship vertical casts nodc data set argo profiling floats coriolis data set and rafos type neutral density floats woce data set are used to study characteristics of meddies in the northeast atlantic in total 241 mediterranean water eddies meddies and 236 parts of float trajectories within meddies are selected for detailed analysis the results suggest that the meddy generation rate at the southern and southwestern iberian peninsula portimao canyon cap st vincent estremadura promontory gorringe bank is 3 times that at the northwestern iberian peninsula porto aveiro canyons cape finisterre and galicia bank meddies generated south of estremadura promontory the southern meddies as compared to those generated north of it the northern meddies have smaller radii smaller vertical extension higher aspect ratio higher rossby number and higher stability stronger potential vorticity anomaly these latter properties result from the southern meddies higher relative vorticity and stronger buoyancy frequency anomaly away from the generation regions meddy drift concentrates along four main paths three quasi zonal paths northern central southern and a path following the african coast coastal the quasi zonal paths are aligned to the isolines of the ambient potential vorticity field several cross path exchanges identified in this work are aligned to topographic rises northward translation of the northern meddies within the north atlantic current to the subpolar gyre is detected within the first 600 km from the coast meddy merger is proved to be a common event this explains the observed difference in radii between the newly generated meddies and those away from the iberian margin the decay of the southern meddies proceeds mainly via the loss of their skirts and does not affect meddy cores until the latest stages the decay of the northern meddies goes in parallel with the decay of their cores in average meddy decay is achieved within 1 2 years although may take over 3 years collisions with the mid atlantic ridge and seamounts sensibly decrease meddy lifetimes meddy decay also speeds up when meddies meet the azores current or the north atlantic current a rapid drop in the number of meddies south of the azores current proves that it represents a dynamic barrier for weak meddies

new observations of meddy movement south of the tejo plateau mediterranean salt lenses meddies are a dominant factor in the salt budget of the atlantic at middepth in spite of their important role their juvenile migration has not yet been directly observed for the first time two rafos float trajectories show strong evidence of a meddy along the iberian continental slope off lisbon over six weeks we obtained drift observations from two levels 629 847 dbar both instruments recorded a series of loops with an azimuthal speed o 30 cm s 1 at a radius of about 25 km relatively high propagation speeds of several centimeters per second indicate the meddy was probably carried along with the undercurrent of mediterranean water the tejo plateau a prominent feature of the continental slope and a natural obstacle for the spreading mediterranean water tongue appears to act as a deflector for advected meddies possibly formed by interaction of the undercurrent with the canyon rich topography farther south

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

observations and laboratory modeling of meddy generation at cape st vincent abstract the amuse canigo and ampor observations provided a large amount of subsurface float data showing evidence of several distinctly different flow behaviors within the mediterranean water layers in the vicinity of cape st vincent southwest portugal some of the floats followed the coastline and moved northward and some were trapped either in anticyclonic lenses of mediterranean water meddies generated at cape st vincent or in cyclonic structures these observations clearly indicated that the anticyclones were accompanied by cyclones at least during their early stages as the dipolar structure moves away from the cape the cyclone tends to shift slowly away from the anticyclone while decaying so that after some time only the meddy persists these in situ observations are compared with large scale laboratory experiments and the agreement between the two sets of observations is remarkably good near the cape and shortly after the generation the nondimensional radius relative vorticity and r

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

the upper oceanic response to overflows a mechanism for the azores current abstract the oceanic response to overflows is explored using a two layer isopycnal model overflows enter the open ocean as dense gravity currents that flow along and down the continental slope while descending the slope overflows typically double their volume transport by entraining upper oceanic water the upper oceanic layer must balance this loss of mass and the resulting convergent flow produces significant vortex stretching overflows thus represent an intense and localized mass and vorticity forcing for the upper ocean in this study simulations show that the upper ocean responds to the overflow induced forcing by establishing topographic plumes that are aligned more or less along isobaths and that have a transport that is typically a few times larger than that of the overflows for the topographic plume driven by the mediterranean overflow the occurrence of eddies near cape st vincent portugal allows the topographic plume to flow across isobaths the modeled topographic plume circu

generation of submesoscale vortices a new mechanism small scale intense vortices composed of water with anomalous values of quasi conservative tracers have been observed in many oceans they are particularly numerous in the beaufort gyre of the arctic ocean possible mechanisms responsible for the generation of these features are examined conservation of temperature salinity and nutrients requires that beaufort sea vortices be created from water that flows into the arctic ocean from the pacific ocean across the broad shallow chukchi sea much of this water passes through barrow canyon near point barrow alaska observations in the canyon show the generation of vortices of approximately the same size as those observed in the beaufort sea barrow canyon is therefore a likely site for the generation of beaufort sea vortices most observed beaufort sea vortices have a central potential vorticity near zero because of a relative vorticity close to their chukchi sea source water is typically stratified with little relative vorticity so that its potential vorticity is nonzero a key step in the generation of the vortices is therefore the reduction of the potential vorticity of chukchi sea water to nearly zero it is proposed that this occurs through the action of frictional torques occurring as the chukchi sea water flows through barrow canyon rather than througji the action of vertical mixing because this flow is driven by a downstream pressure gradient it is concentrated on the right hand wall of the canyon by the coriolis force the frictional torques thus preferentially reduce the potential vorticity of the fluid anticyclonic vortices are therefore preferentially generated it is suggested that a similar scenario may play a role in the generation of submesoscale vortices containing water from the mediterranean and labrador seas

three dimensional oceanic eddy analysis in the southern california bight from a numerical product with eight islands complex coastlines and bottom topography strong wind curls and frequent upwelling fronts the southern california bight scb is an area with strong eddy activity by applying an automated eddy detection scheme to a 12 year high resolution numerical product of the oceanic circulation in the scb a three dimensional eddy data set is developed it includes information for each eddy s location polarity intensity size boundary and moving path at nine vertical levels through a series of statistical analyses applied to the eddy data set three dimensional statistical characteristics of mesoscale and submeoscale eddy variations in the scb are elucidated these shed light on how eddies are generated evolve and terminate a significant percentage of eddies is found to be generated around islands and headlands along the coastline which indicates that islands in the scb play a vital role in eddy generation three types of eddies based on shape are identified from the numerical product bowl lens and cone a dynamic analysis shows that some submesoscale eddies with finite local rossby numbers tend to be ageostrophic balanced while mesoscale eddies are in geostrophic balance the present research results are useful for the interpretation of data sets obtained during the interdisciplinary santa barbara channel radiance in a dynamic ocean radyo field experiment conducted on september 3 25 2008

meddy trajectories in the canary basin measured during the semaphore experiment 1993 1995 as part of the structures des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore experiment four mediterranean water eddies meddies were identified in the canary basin and tracked with freely drifting rafos floats one large and energetic meddy discovered 1700 km west of cape saint vincent portugal set a distance and speed record as it translated another 1700 km southwestward at 3 9 cm s during 1 5 years this meddy traveled 57 of the distance from cape saint vincent toward the spot mcdowell and rossby 1978 found a possible meddy north of the dominican republic two meddies were observed to interact with the azores current as they passed underneath or through it three meddies collided with tall seamounts which seemed to disrupt the normal swirl velocity perhaps fatally in two cases one meddy appeared to bifurcate when it collided with seamounts