malvinas current volume transport at 41 s a 24 yearlong time series consistent with mooring data from 3 decades and satellite altimetry fil artana camila indira instituto franco argentino sobre estudios del clima y sus impactos argentina centre national de la recherche scientifique francia universite pierre et marie curie francia

global statistical space time scales of oceanic variability estimated from the topex poseidon altimeter data four years of the topex poseidon altimeter data are used to produce estimates of statistical space time scales of ocean variabilities for the sea surface height a three dimensional space time correlation function with an anisotropic directional dependence is assumed the function has gaussian distributions in radial directions in the space time coordinates and ellipsoidal contour surfaces the function can reveal the space time scales and propagations of the variabilities and statistical errors in the altimeter data we evaluated the space time scales using the best fit correlation function to the altimeter data the scales show geographical differences this means that dominant variabilities depend on regions we show an optimum interpolation oi method as an example of the application of the fitted correlation function the oi is applied to the altimeter data in the space time domain to make grid point data with higher accuracy than those obtained from a usual spatial two dimensional oi 2 d oi the values of the correlation function are used for the correlation coefficients of the first guess error in the oi a propagation diagram obtained from the space time oi 3 d oi shows clear propagations of planetary disturbances with larger amplitude the grid point values from the 3 d oi show better correspondences with sea levels from tide gauges than those from the 2 d oi the advantage is due to the data of the different cycles being additionally adopted and the correlation function reflecting propagation of the ocean variabilities

internal tides around the hawaiian ridge estimated from multisatellite altimetry 1 satellite altimetric sea surface height anomaly ssha data from geosat follow on gfo and european remote sensing ers as well as topex poseidon t p are merged to estimate m2 internal tides around the hawaiian ridge with higher spatial resolution than possible with single satellite altimetry the new estimates are compared with numerical model runs along track analyses show that m2 internal tides can be resolved from both 8 years of gfo and 15 5 years of ers ssha data comparisons at crossover points reveal that the m2 estimates from t p gfo and ers agree well multisatellite altimetry improves spatial resolution due to its denser ground tracks thus m2 internal tides can be plane wave fitted in 120 km 120 km regions compared to previous single satellite estimates in 4 lon 3 lat or 250 km 250 km regions in such small fitting regions the weaker and smaller scale mode 2 m2 internal tides can also be estimated the higher spatial resolution leads to a clearer view of the m2 internal tide field around the hawaiian ridge discrete generation sites and internal tidal beams are clearly distinguishable and consistent with the numerical model runs more importantly multisatellite altimetry produces larger m2 internal tidal energy fluxes which agree better with model results than previous single satellite estimates this study confirms that previous altimetric underestimates are partly due to the more widely spaced ground tracks and consequently larger fitting region multisatellite altimetry largely overcomes this limitation

a census of tehuantepec and papagayo eddies in the northeastern tropical pacific 1 we use a 12 year 1992 2004 time series of satellite altimetry to characterize long lived wind generated anticyclonic eddies originating in the gulfs of tehuantepec and papagayo in the northeastern tropical pacific a total of 42 tehuantepec and 26 papagayo eddies were observed eddy merging usually of a tehuantepec papagayo pair was observed on 16 occasions on average the eddy season began in late october and lasted approximately 250 days until early july with 3 5 tehuantepec and 2 2 papagayo eddies formed each year minimum average eddy lifespan was 143 days and 84 days for tehuantepec and papagayo eddies respectively there was considerable interannual variability in eddy activity with greater fewer number of eddies more intense weaker eddies and a longer shorter eddy season during el nino la nina years eddy intensification was consistently observed at the east pacific rise

pathways of eddies in the south atlantic ocean revealed from satellite altimeter observations 1 the majority of the kinetic energy of ocean currents is contained in the mesoscale eddies the pathways of ocean eddies which are the weather of ocean circulation are mapped from space using a decade long record of sea surface height measured by two simultaneously flying satellite radar altimeters the speed and direction of the propagation of eddies in the south atlantic ocean are presented in the paper the patterns of the eddy propagation velocity reveal the effects of the interaction between mean flow and eddies with strong influence of bottom topography the information describes a unique property of the ocean general circulation and serves as a basis for testing ocean models

paleosol and dolocrete associated clay mineral occurrences in siliciclastic red sediments of the late miocene komisini formation of the tuzgolu basin in central turkey abstract the late miocene was characterized by high global temperatures and partly to nearly complete desiccation of the mediterranean sea throughout the latter part of the messinian age the messinian salinity crisis the late miocene marine mediterranean sea area has been widely studied from different perspectives but terrestrial paleoenvironmental and paleoclimatic records from the mediterranean area are highly limited in their spatial range to this end the paleosols dolocrete and fluvial sedimentary rocks of the komisini formation in the northwestern part of the tuzgolu basin are described in detail six lithofacies were identified as a clast supported gravel b massive pebbly sandstone c massive mudstone d disrupted mud e disrupted conglomerate and f disrupted matrix supported conglomerate the siliciclastic facies were interpreted as braidplain and the distal part of braidplain deposits is associated with an ophiolitic area while the disrupted mud and disrupted conglomerate were identified as three types of paleosols inceptisols aridisol and vertisols the calcretes occur in the paleosols in nodular powder and massive forms clay minerals include smectite chlorite palygorskite illite and serpentine gypsum smectite and chlorite are dominant minerals at the base and middle part of the section whereas palygorskite and illite appear as the prevailing clay minerals in the upper sections smectite illite and palygorskite precipitated in a vadose zone from strongly evaporated alkaline water rich in si ca and mg and poor in al at increased temperatures and at an advanced stage of dolocrete and paleosol formation k si mg al fe and ca are required for smectite illite palygorskite and calcification given the increase in ba cr ni and co these cations might have originated from ophiolite carbonate and volcanic units as a consequence the vertical distribution of clay mineral types suggests the variations of paleoclimatic conditions during the deposition and the relationships among the type of host rock paleosol and dolocrete which corresponds to nearly complete desiccation of the mediterranean sea

a description of local and nonlocal eddy mean flow interaction in a global eddy permitting state estimate abstractthe assumption that local baroclinic instability dominates eddy mean flow interactions is tested on a global scale using a dynamically consistent eddy permitting state estimate interactions are divided into local and nonlocal if all the energy released from the mean flow through eddy mean flow interaction is used to support eddy growth in the same region or if all the energy released from eddies through eddy mean flow interaction is used to feed back to the mean flow in the same region eddy mean flow interaction is local otherwise it is nonlocal different regions have different characters in the subtropical region studied in detail interactions are dominantly local in the southern ocean and kuroshio and gulf stream extension regions they are mainly nonlocal geographical variability of dominant eddy eddy and eddy mean flow processes is a dominant factor in understanding ocean energetics

vorticity structures in the tropical pacific from a numerical simulation abstractthe small scale variability of the tropical pacific is studied with the simulations from a numerical model in terms of vorticity structures a lagrangian method based on the okubo weiss parameter is used to identify the structures and track their main characteristics between 8 s and 8 n the structure characteristics are spatially inhomogeneous compared to higher latitudes they can be grouped into three categories anticyclonic and cyclonic structures off the equator and the equatorial structures between 2 s and 2 n they all have a strong annual cycle with maximum presence from september to march except during strong el nino years when the number of structures becomes very low off the equator from 2 to 8 the anticyclonic structures dominate but with drastically different characteristics north and south of the equator in the north large nonlinear vortices develop known as the tropical instability vortices in phase with the 30 35 day oscillation related to an unstable first meridional

ocean circulation in the great australian bight in an eddy resolving ocean reanalysis the eddy field seasonal and interannual variability abstract the ocean circulation in the great australian bight gab is dominated by the surface intensified leeuwin current lc over the outer continental shelf and the flinders current farther offshore in the gab the lc flows eastwards and varies seasonally with strongest currents of up to 0 8 m s at 130 5 e bringing warm and salty waters as far east as western tasmania the flinders current flows westwards as an undercurrent at depths of around 500 m over the continental slope and at the surface offshore of the lc off the shelf the gab is rich in mesoscale eddies with surface intensified currents of up to 0 4 m s that are coherent over the full water depth getting weaker with depth within deep water eddies isotherms are displaced vertically by up to 200 m eddies in the eastern gab are most energetic in austral winter and spring coincident with the seasonal weakening of the lc the eastern most penetration of gab eddies occurs in austral winter when the lc starts to weaken we hypothesise that the horizontal shear associated with the lc generates eddies in the eastern gab the volume transport of the lc at the head of the gab is typically between 1 and 7 sv with a clear seasonal cycle and the interannual variability of lc transport is up to 2 sv

an objective method for computing advective surface velocities from sequential infrared satellite images using cross correlations between sequential infrared satellite images an objective technique is developed to compute advective sea surface velocities cross correlations are computed in 32 x 32 pixel search second image and 22 x 22 template first image windows from gradients of sea surface temperature computed from the satellite images velocity vectors computed from sequential images of the british columbia coastal ocean generally appear coherent and consistent with the seasonal surface current in the region during periods of strong wind forcing as indicated by maps of sea level pressure the image advective velocities are stronger and more coherent spatially and appear to cross surface temperature gradients when winds are weaker the advective velocities correspond better with the infrared temperature patterns suggesting the increased contribution of the geostrophic current to the surface flow velocities determined from coincident near surface drogued 5 10 m buoys positioned every half hour by internal loran c units in mid june show excellent agreement with the image advective velocities in addition conductivity temperature and depth ctd measurements taken during the buoy tracking confirm the homogeneity of the upper 10 m and ctd derived geostrophic currents are consistent with

cold core eddies and fronts of the antarctic circumpolar current south of new zealand from in situ and satellite data 1 the meridional heat flux required to balance the heat lost by ocean to atmosphere at high latitudes must be accomplished by some mechanism other than mean advection and the heat flux by eddies crossing the antarctic circumpolar current acc may be a candidate in this study the positions of the main acc fronts are determined based on 23 expendable bathythermographs xbt transects collected from 1994 to 2010 and are compared with those detected through satellite altimetry then cold core anomalies in xbt sections are identified and altimetry is used to follow the spatial temporal evolution of these cold low sea level anomalies mean values of main parameters such as speed 0 35 km h lifetime 79 weeks and diameter 105 km are estimated moreover estimations of rotational speed 0 9 76 8 cm s ocean surface layer heat content along temperature sections and eddy available heat anomaly mean value 9 74 109 jm 2 give a wider description of the detected eddies in our study area the spawning of eddies is found to occur downstream of the southeast indian ridge and in correspondence of the polar front pf with regard to the acc frontal structure the contribution of eddies to the global heat budget is not only linked to their ability to cross the acc fronts but also to the capacity of keeping partially unaltered the properties of water inside them analysis of the relation between the translation and rotational speeds shows that a typical eddy may effectively be a significant part 0 8 of the net meridional heat transport across the pf with a mean heat content anomaly of 7 65 1019 j

observations of sst induced perturbations of the wind stress field over the southern ocean on seasonal timescales the surface wind stress response to sea surface temperature sst over the latitude range 308 608 si n the southern ocean is described from the national aeronautics and space administration s quikscat scatterometer observations of wind stress and reynolds analyses of sst during the 2 yr period august 1999 to july 2001 while ocean atmosphere coupling at midlatitudes has previously been documented from several case studies this is the first study to quantify this relation over the entire southern ocean the spatial structures of the surface wind perturbations with wavelengths shorter than 108 latitude by 308 longitude are closely related to persistent spatial variations of the sst field on the same scales the wind stress curl and divergence are shown to be linearly related respectively to the crosswind and downwind components of the sst gradient the curl response has a magnitude only about half that of the divergence response this observed coupling is consistent with the hypothesis that sst modification of marine atmospheric boundary layer mabl stability affects vertical turbulent mixing of momentum inducing perturbations in the surface winds the nonequivalence between the responses of the curl and divergence to the crosswind and downwind sst gradients suggests that secondary circulations in the mabl may also play an important role by producing significant perturbations in the surface wind field near sst fronts that are distinct from the vertical turbulent transfer of momentum the importance of the wind stress curl in driving ekman vertical velocity in the open ocean implies that the coupling between winds and sst may have important feedback effects on upper ocean processes near sst fronts

combining altimeter and subsurface float data to estimate the time averaged circulation in the upper ocean 1 a new technique is presented for estimating time averaged upper ocean geostrophic velocity from a combination of altimeter data and subsurface float data the technique makes uses of the strong relationship between sea surface height anomaly and anomalous velocity at depth to reduce mesoscale eddy variability in subsurface float displacements the technique is demonstrated on a region in the north atlantic that was well sampled by argo floats the 2004 through 2006 time averaged density field was estimated from the surface to 2000 db by combining altimeter and hydrographic data from the floats in addition a reference velocity field was estimated at 1000 db based on a combination of altimeter data and subsurface float displacements the reference velocity field was combined with geostrophic shear based on the density field to produce a three dimensional estimate of geostrophic velocity from the surface to 2000 db the gulf stream transport in the upper 2000 db is estimated to be 76 sv at 73 w in addition an estimate of the 3 year average dynamic height at the surface was computed by combining the 1000 db reference dynamic height and the time averaged density field

dynamically balanced absolute sea level of the global ocean derived from near surface velocity observations 1 the 1992 2002 time mean absolute sea level distribution of the global ocean is computed for the first time from observations of near surface velocity for this computation we use the near surface horizontal momentum balance the velocity observed by drifters is used to compute the coriolis force and the force due to acceleration of water parcels the anomaly of horizontal pressure gradient is derived from satellite altimetry and corrects the temporal bias in drifter data distribution ncep reanalysis winds are used to compute the force due to ekman currents the mean sea level gradient force which closes the momentum balance is integrated for mean sea level we find that our computation agrees within uncertainties with the sea level computed from the geostrophic hydrostatic momentum balance using historical mean density except in the antarctic circumpolar current a consistent horizontally and vertically dynamically balanced near surface global pressure field has now been derived from observations

a new eulerian method to estimate spicy agulhas leakage in climate models the agulhas leakage brings warm and saline water from the indian ocean into the south atlantic forming part of the returning branch of the global thermohaline circulation an important component of climate we develop a new method using the passive tracer spice to estimate agulhas leakage transport in an ocean eddy resolving climate model that properly captures agulhas retroflection and leakage we identify agulhas leakage waters as positive spice anomalies 0 1 and are able to trace leakage to depths greater than 1000 m spice based eulerian agulhas leakage captures spikes in lagrangian leakage transport which coincide with the passage of agulhas rings yielding a statistically significant correlation 0 47 on interannual times scales differences between eulerian and lagrangian transports are reduced and correlation increases to 0 77 we obtain a mean spice based eulerian agulhas leakage of 17 4 sverdrup sv and lagrangian agulhas leakage of 18 2 sv which are within the range of observational estimates

agulhas eddies a synoptic view using geosat erm data abstract warm core rings formed in the agulhas retroflection transfer water from the indian ocean to the south atlantic in an attempt to measure the strength of this exchange a combination of satellite altimeter and hydrographic data are used to examine agulhas eddy paths and decay rates in the south atlantic because the surface dynamic height of a warm core eddy is higher than surrounding waters the rings are visible in satellite altimeter measurements over 20 agulhas eddies have been tracked from maps of anomalous sea surface height ssh derived from the geosat exact repeat mission erm dataset the correlation r2 of dynamic height referenced to 2000 dbar and anomaly ssh for one coincidentally sampled area is 97 within an agulhas eddy dropping to a fraction of that outside of it indicating that the ssh anomaly signal is a reliable measure for strong features like agulhas eddies the sizes and distribution of the agulhas eddies in the erm record compare favorably with those in recent hydrogr

ocean eddy dynamics in a coupled ocean atmosphere model the role of mesoscale oceanic eddies is analyzed in a quasigeostrophic coupled ocean atmosphere model operating at a large reynolds number the model dynamics are characterized by decadal variability that involves nonlinear adjustment of the ocean to coherent north south shifts of the atmosphere the oceanic eddy effects are diagnosed by the dynamical decomposition method adapted for nonstationary external forcing the main effects of the eddies are an enhancement of the oceanic eastward jet separating the subpolar and subtropical gyres and a weakening of the gyres the flow enhancing effect is due to nonlinear rectification driven by fluctuations of the eddy forcing this is a nonlocal process involving generation of the eddies by the flow instabilities in the western boundary current and the upstream part of the eastward jet the eddies are advected by the mean current to the east where they backscatter into the rectified enhancement of the eastward jet the gyre weakening effect which is due to the time mean buoyancy component of the eddy forcing is a result of the baroclinic instability of the westward return currents the diagnosed eddy forcing is parameterized in a non eddy resolving ocean model as a nonstationary random process in which the corresponding parameters are derived from the control coupled simulation the key parameter of the random process its variance is related to the large scale flow baroclinicity index it is shown that the coupled model with the non eddy resolving ocean component and the parameterized eddies correctly simulates climatology and low frequency variability of the control eddy resolving coupled solution

classification and sudden departure mechanism of high speed landslides caused by the 2008 wenchuan earthquake the sudden departure mechanism of high speed landslides has always constituted a popular yet difficult research topic therefore although a systematic classification of high speed landslides is necessary particularly since different types of landslides exhibit different mechanisms an associated methodology has yet to be established this paper investigates an easily overlooked phenomenon landslide quake which is defined as a local ground vibration triggered by the sudden rupture of the locked segment of a high speed landslide that occurs immediately prior to the departure of the landslide this new concept is employed as a foundation for a new classification the characteristics and formation conditions of landslide quake are discussed based upon which the high speed landslides that occurred following the 2008 wenchuan earthquake are classified into three different types subsequently the sudden departure mechanism of each type of landslide is analyzed thereby providing a new method for research on the sudden departure mechanism of high speed landslides

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

on the reasons for the formation and variability of the azores current abstract recent studies have shown that the formation of the well defined zonally oriented azores current may be the result of water mass transformation associated with the mediterranean outflow in the gulf of cadiz as the denser mediterranean water descends down the continental slope it entrains overlying north atlantic central water it is believed that the azores current then forms as part of the horizontal recirculating gyre generated through the plume mechanism in this study the authors further explore this hypothesis by performing a series of numerical experiments these experiments are based on a high resolution general circulation model that includes the mediterranean sea and that realistically simulates the water mass exchange through the strait of gibraltar and the transport and variability of the azores current the authors show that the divergence of the relative vorticity flux and the planetary vorticity flux associated with planetary waves are the main factors determining the variab

vortices of the mediterranean sea an altimetric perspective the presence of coherent vortices makes observed mesoscale fields of the ocean resemble twodimensional turbulence using this analogy a common definition of a coherent structure has been used to study the statistical properties of mediterranean sea vortices observed by satellite altimeters over a 7 yr period a vortex has been defined as the simply connected region with values of the okubo weiss parameter w 0 2w where w is the spatial standard deviation of w and the same sign of vorticity this definition is shown to be appropriate to detect and characterize statistically properties such as size mean kinetic energy and amplitude of vortices in the mediterranean basin from sea level anomaly maps corresponding to the period from october 1992 to october 1999 the distribution of such properties for the mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long lived vortices from the whole set of structures identified in altimetric maps such coherent vortices appear to be selected for amplitudes greater than 2w where the amplitude has been defined in terms of the okubo weiss parameter rather than vorticity and strongly correspond to those reported from observations with independent data systematic locating and tracking of such vortices provide for the first time a general picture of their preferential paths in the mediterranean basin which are characterized by complex but rather well defined patterns

high resolution satellite measurements of the atmospheric boundary layer response to sst variations along the agulhas return current abstract the marine atmospheric boundary layer mabl response to sea surface temperature sst perturbations with wavelengths shorter than 30 longitude by 10 latitude along the agulhas return current arc is described from the first year of sst and cloud liquid water clw measurements from the advanced microwave scanning radiometer amsr on the earth observing system eos aqua satellite and surface wind stress measurements from the quikscat scatterometer amsr measurements of sst at a resolution of 58 km considerably improves upon a previous analysis that used the reynolds sst analyses which underestimate the short scale sst gradient magnitude over the arc region by more than a factor of 5 the amsr sst data thus provide the first quantitatively accurate depiction of the sst induced mabl response along the arc warm cold sst perturbations produce positive negative wind stress magnitude perturbations leading to short scale perturbations in the wind stress curl and divergence fields that are li

pattern and velocity of propagation of the global ocean eddy variability 1 satellite altimeter data are used to study the characteristics of the horizontal propagation of eddy variability of the global oceans decade long time series of sea surface height is analyzed for finding the maximum cross correlation with neighboring time series within a window of space and time lags the space and time lags corresponding to the maximum correlation allow an estimate of the propagation velocity of the eddy variability that dominates the variance of sea surface height anomalies the method cannot distinguish the various forms of eddy variability isolated eddies and fronts the meandering of ocean currents or planetary waves however the results provide at a given location of the global oceans a uniquely determined propagation velocity that represents a time averaged description of the tendency of the movement of the local eddy variability the propagation velocity is highly inhomogeneous in space outside the equatorial zone the zonal propagation is intrinsically westward modified by ocean currents which could reverse the zonal propagation to eastward in regions like the gulf stream and the antarctic circumpolar current at midlatitudes and high latitudes the propagation pattern is highly affected by the path of ocean currents and the shape of bottom topography at tropical latitudes the meridional propagation is convergent toward the equator in the western basins and divergent away from the equator in the eastern basins comparison with the simulations of an eddy permitting ocean general circulation model shows overall agreement especially in the latitudinal variation of the zonal propagation velocity the result suggests that the model has captured the essence of the dynamics governing the propagation of ocean eddy variability

a mechanism for the latitudinal dependence of peak spectrum sea surface height variability previous studies have shown that the power spectrum of satellite observed sea surface height ssh variability peaks at a certain frequency or a wave number band at a given latitude lin et al 2008 attributed this latitudinal dependence to the critical frequency of the first baroclinic mode rossby waves in the tropical and subtropical oceans their study was based on the linear rossby wave theory and focused on ssh variability in the tropical and subtropical oceans since the altimetry data do not adequately resolve lengths of baroclinic rossby waves at and near the critical frequency in high latitudes in this study we expand their analysis to high latitude oceanic basins and to include nonlinear eddy effects by using a linear wave model and a high resolution model output from the ogcm for the earth simulator ofes it is found that the linear wave mechanism by and large remains valid in the tropical and subtropical oceans in higher latitudes as well as in some regions in the western tropical and subtropical oceans other mechanisms like nonlinear eddy play more important role in determining the ssh variability

subsurface circulation and mesoscale variability in the algerian subbasin from altimeter derived eddy trajectories algerian eddies are the strongest and largest propagating mesoscale structures in the western mediterranean sea they have a large influence on the mean circulation water masses and biological processes over 20 years of satellite altimeter data have been analyzed to characterize the propagation of these eddies using automatic detection methods and cross correlation analysis we found that on average algerian eddy trajectories form two subbasin scale anticlockwise gyres that coincide with the two algerian gyres which were described in the literature as the barotropic circulation in the area this result suggests that altimetry sea surface observations can provide information on subsurface currents and their variability through the study of the propagation of deep mesoscale eddies in semienclosed seas the analysis of eddy sea level anomalies along the mean pathways reveals three preferred areas of formation eddies are usually formed at a specific time of the year in these areas with a strong interannual variability over the last 20 years

determining the mean gulf stream and its recirculations through combining hydrographic and altimetric data the altimetric data from the first 2 5 year geosat exact repeat mission were used to estimate the mean sea surface height ssh field in the region of the gulf stream and its recirculation gyres assuming the instantaneous surface velocity field is composed of an eastward flowing jet and two westward recirculating flows we used the time varying surface data from the altimeter to determine the shape of the along track mean ssh profiles and the historical hydrographic data to constrain the net ssh difference across the gulf stream system the two dimensional mean ssh field was determined by objectively mapping the mean height profiles along the ascending and descending tracks the ssh jump across the mean gulf stream has a maximum of 1 15m around 65 w and drops to an almost constant 0 9m downstream of the new england seamount chain nesc while the ssh jump associated with the mean northern recirculating flow is mostly uniform we found that the gulf stream s southern recirculation has two local gyres that are separated by the nesc an attempt was then made to estimate the mean deep circulation in this region by comparing the mean ssh field derived from the altimetry data and the surface dynamic height field based on the historical hydrographic data despite the large uncertainties the mean deep flow pattern thus estimated agrees favorably with the overall circulation pattern from the long term current meter observations like the well defined northern recirculation gyre we found that a continuous southward flow exists along 57 5 w which follows closely along the deep layer potential vorticity contours to the south of the gulf stream the deep circulation consists of two separated recirculation gyres the recirculation gyre to the east of the nesc appears to be trapped around the corner rise

interannual eddy kinetic energy modulations in the agulhas return current interannual variability in the mesoscale eddy field in the agulhas return current arc of 32 42 degrees s and 15 35 degrees e is investigated based on satellite altimeter observations and state estimate from the estimating the circulation and climate of the ocean phase ii from 1993 to 2016 it is found that the interannual modulation of eddy kinetic energy in the arc region is externally mediated by the wind stress forcing that generates the westward propagating sea surface height anomalies across the south indian ocean subtropical gyre the wind forced sea surface height anomalies influence the upstream agulhas current volume transports by modulating the intensity of barotropic instability of the arc mean flow centered around the retroflection region the agulhas current inflow variability leads to the downstream interannual eddy kinetic energy fluctuations in the arc region

global observations of horizontal mixing from argo float and surface drifter trajectories mixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers with important implications for physical and biochemical systems at local to global scales roach et al 2016 https doi org 10 1002 2015jc011440 demonstrated that a two particle analysis of argo trajectories produces robust estimates of horizontal mixing in the southern ocean here we extend this analysis to produce global 1 1 maps of eddy diffusivity at the nominal argo parking depth of 1 000 m we also applied this methodology to estimate surface eddy diffusivities from global drifter program gdp surface drifters the global mean eddy diffusivity was 543 155 m2 s at 1 000 m and 2637 311 m2 s at the surface with elevated diffusivities in regions of enhanced eddy kinetic energy such as western boundary currents and along the antarctic circumpolar current the eddy kinetic energy at the equator is high at both the surface and depth but the eddy diffusivity is only enhanced near the surface at depth the eddy diffusivity is strongly suppressed due to the presence of mean flow we used our observational estimates to test the validity of an eddy diffusivity parameterization that accounts for mixing suppression in the presence of zonal mean flows our results indicated that this parameterization generally agrees with the directly observed eddy diffusivities in the midlatitude and high latitude oceans

divergent pathways of cyclonic and anti cyclonic ocean eddies satellite altimetry is used to study the propagation pathways of warm and cold ocean eddies in different ocean basins we consider eddies that have a life span longer than 3 months and we present three regional studies in the southeast indian the southeast atlantic and the northeast pacific oceans the case studies show that simple theories for vortex propagation on a plane work in regions where energetic eddies propagate though a weak background flow under these conditions anticyclonic cyclonic eddies propagate westward and equatorward poleward this divergence in the eddy pathways implies a net equatorward eddy heat flux and has implications for the meridional transport of freshwater carbon nutrients etc

ocean surface geostrophic circulation climatology and annual variations inferred from satellite altimetry and goce gravity data we have studied for the first time variations in absolute surface geostrophic currents sgc using satellite data only the proposed approach combines 18 years altimetry data which provide reliable measurements of absolute sea level asl with a gravity field and steady state ocean circulation explorer geoid model to obtain dynamic topography and achieves unprecedented precision and accuracy our proposal overcomes the main limitations of existing approaches based solely on altimetry data which suffer from lack of an independent reference for derivation of asl maps and approximations based on in situ data which are characterized by a sparse and inhomogeneous coverage in time and space features of annual variations of sgc are also addressed as a result of our study we provide new absolute sgc climatology in the form of a 52 week data set of surface current fields gridded at quarter degree longitude and latitude resolution and resolving spatial scales as short as 140 km for presentation this data set is averaged monthly and the results presented as monthly climatology are compared with climatology based on in situ observations from drifter data