an analytical model of the response of the meridional overturning circulation to changes in wind and buoyancy forcing abstractan analytical model of the full depth ocean stratification and meridional overturning circulation for an idealized atlantic basin with a circumpolar channel is presented the model explicitly describes the ocean response to both southern ocean winds and the global pattern and strength of prescribed surface buoyancy fluxes the construction of three layers defined by the two isopycnals of overturning extrema allows the description of circulation and stratification in both the upper and abyssal ocean the system is fully solved in the adiabatic limit to yield scales for the surface layer thickness buoyancies of each layer and overturning magnitudes the analytical model also allows scaling of the antarctic circumpolar current acc transport the veracity of the three layer framework and derived scales is confirmed by applying the analytical model to an idealized geometry eddy permitting ocean general circulation model consistent with previous results the abyssal overturning is found to scale

residual mean solutions for the antarctic circumpolar current and its associated overturning circulation abstract residual mean theory is applied to the streamwise averaged antarctic circumpolar current to arrive at a concise description of the processes that set up its stratification and meridional overturning circulation on an f plane simple solutions are found in which transfer by geostrophic eddies colludes with applied winds and buoyancy fluxes to determine the depth and stratification of the thermocline and the pattern of associated residual meridional overturning circulation

the adiabatic pole to pole overturning circulation abstractthe adiabatic pole to pole cell of the residual overturning circulation roc is studied in a two hemisphere semienclosed basin with a zonally reentrant channel occupying the southernmost eighth of the domain three different models of increasing complexity are used a simple analytically tractable zonally averaged model a coarse resolution numerical model with parameterized eddies and an eddy resolving general circulation model two elements are found to be necessary for the existence of an adiabatic pole to pole cell 1 a thermally indirect wind driven overturning circulation in the zonally reentrant channel analogous to the deacon cell in the antarctic circumpolar current acc region and 2 a set of outcropping isopycnals shared between the channel and the semienclosed region of the northern hemisphere these points are supported by several computations varying the domain geometry the surface buoyancy distribution and the wind forcing all three models give results that are qualitat

rotating horizontal convection horizontal convection hc is the generic name for the flow resulting from a buoyancy variation imposed along a horizontal boundary of a fluid we study the effects of rotation on three dimensional hc numerically in two stages first when baroclinic instability is suppressed and second when it ensues and baroclinic eddies are formed we concentrate on changes to the thickness of the near surface boundary layer the stratification at depth the overturning circulation and the flow energetics during each of these stages our results show that for moderate flux rayleigh numbers o 1 0 11 rapid rotation greatly alters the steady state solution of hc when the flow is constrained to be uniform in the transverse direction rapidly rotating solutions do not support a boundary layer exhibit weaker overturning circulation and greater stratification at all depths in this case diffusion is the dominant mechanism for lateral buoyancy flux and the consequent buildup of available potential energy leads to baroclinically unstable solutions when these rapidly rotating flows are perturbed baroclinic instability develops and baroclinic eddies dominate both the lateral and vertical buoyancy fluxes the resulting statistically steady solution supports a boundary layer larger values of deep stratification and multiple overturning cells compared with non rotating hc a transformed eulerian mean approach shows that the residual circulation is dominated by the quasi geostrophic eddy streamfunction and that the eddy buoyancy flux has a non negligible interior diabatic component the kinetic and available potential energies are greater than in the non rotating case and the mixing efficiency drops from sim 0 7 to sim 0 17 the eddies play an important role in the formation of the thermal boundary layer and together with the negatively buoyant plume help establish deep stratification these baroclinically active solutions have characteristics of geostrophic turbulence

suppression of eddy diffusivity across jets in the southern ocean abstract geostrophic eddies control the meridional mixing of heat carbon and other climatically important tracers in the southern ocean the rate of eddy mixing is typically quantified through an eddy diffusivity there is an ongoing debate as to whether eddy mixing in enhanced in the core of the antarctic circumpolar current or on its flanks a simple expression is derived that predicts the rate of eddy mixing that is the eddy diffusivity as a function of eddy and mean current statistics this novel expression predicts suppression of the cross jet eddy diffusivity in the core of the antarctic circumpolar current despite enhanced values of eddy kinetic energy the expression is qualitatively and quantitatively validated by independent estimates of eddy mixing from altimetry observations this work suggests that the meridional eddy diffusivity across the antarctic circumpolar current is weaker than presently assumed because of the suppression of eddy mixing by the strong zonal current

the role of eddy transfer in setting the stratification and transport of a circumpolar current abstract high resolution numerical experiments of a circumpolar current are diagnosed to study how lateral and vertical transfer of buoyancy by geostrophic eddies balances advection by a meridional circulation driven by surface wind stresses and buoyancy fluxes a theory is developed in the framework of the residual circulation to relate the vertical and horizontal stratification set up to the transfer properties of eddies and the patterns of imposed wind and buoyancy forcing simple expressions are found for the depth of penetration stratification baroclinic transport and residual circulation of the current finally the ideas are applied to the antarctic circumpolar current acc and yield predictions for how its properties depend on wind and buoyancy forcing

abyssal circulation driven by near boundary mixing water mass transformations and interior stratification the emerging view of the abyssal circulation is that it is associated with bottom enhanced mixing which results in downwelling in the stratified ocean interior and upwelling in a bottom boundary layer along the insulating and sloping seafloor in the limit of slowly varying vertical stratification and topography however boundary layer theory predicts that these upslope and downslope flows largely compensate such that net water mass transformations along the slope are vanishingly small using a planetary geostrophic circulation model that resolves both the boundary layer dynamics and the large scale overturning in an idealized basin with bottom enhanced mixing along a midocean ridge we show that vertical variations in stratification become sufficiently large at equilibrium to reduce the degree of compensation along the midocean ridge flanks the resulting large net transformations are similar to estimates for the abyssal ocean and span the vertical extent of the ridge these results suggest that boundary flows generated by mixing play a crucial role in setting the global ocean stratification and overturning circulation requiring a revision of abyssal ocean theories

adjusting internal model errors through ocean state estimation abstract oceanic state estimation is a powerful tool to estimate internal model parameters simultaneously with the model s initial conditions and surface forcing field that jointly would bring a model into consistency with time varying large scale ocean observations here an attempt to estimate geographically varying fields of horizontal and vertical viscosity and diffusivity within a 9 yr long estimation procedure is presented the estimated coefficients are highly efficient in preserving watermass characteristics and frontal structures by reducing the model temperature and salinity drift especially around the southern ocean the estimated mean circulation results in stronger transports of western boundary currents and of the antarctic circumpolar current moreover an increase of about 10 in the strength of the meridional overturning circulation and in the poleward heat transport can be found estimated changes in the horizontal mixing coefficients seem to agree with the notion that diapycnal mixing i

estimating eddy stresses by fitting dynamics to observations using a residual mean ocean circulation model and its adjoint a global ocean circulation model is formulated in terms of the residual mean and used to study eddy mean flow interaction adjoint techniques are used to compute the three dimensional eddy stress field that minimizes the departure of the coarse resolution model from climatological observations of temperature the resulting 3d maps of eddy stress and residual mean circulation yield a wealth of information about the role of eddies in large scale ocean circulation in eddy rich regions such as the southern ocean the kuroshio and the gulf stream eddy stresses have an amplitude comparable to the wind stress of order 0 2 n m 2 and carry momentum from the surface down to the bottom where they are balanced

on the transport and angular momentum balance of channel models of the antarctic circumpolar current abstract angular momentum balances are discussed both in general as well as in the context of simple channel models of the antarctic circumpolar current acc particular emphasis is placed on the close relationship between the angular momentum balance and the meridional circulation it is found that topographic form drag is established very early in the integration whereas interfacial form drag can take much longer to develop restrictions on the geostrophic portion of the meridional circulation imposed by zonally reconnecting potential vorticity contours in the upper ocean allow derivation of an estimate for the steady state transport the estimate assumes there to be little or no circumpolar flow at great depth an assumption that stems from the belief that the band of zonally reconnecting geostrophic contours in the southern ocean does not extend to the ocean floor the predicted transport is proportional to the strength of the stratification and compares favorably with numerical results in the lite

upper ocean eddy heat flux across the antarctic circumpolar current in drake passage from observations time mean and seasonal variability abstracteddy heat flux plays a fundamental role in the southern ocean meridional overturning circulation providing the only mechanism for poleward heat transport above the topography and below the

understanding the regional variability of eddy diffusivity in the pacific sector of the southern ocean a diagnostic framework is presented based on the nakamura effective diffusivity to investigate the regional variation in eddy diffusivity comparison of three different diffusivity calculations enables the effects of locally enhanced tracer diffusion to be distinguished from the streamwise average it also enables the distinction to be made between locally generated complexity in the tracer structure and that advected into a particular domain the technique is applied to the pacific sector of the southern ocean the results highlight the important role that the mean flow plays in determining eddy diffusivity the effective diffusivity is not simply related to the eddy kinetic energy in regions of a strong mean flow the eddy diffusivity can be suppressed even in the presence of moderately strong eddy activity conversely in a region of weak mean flow the eddy diffusivity can be enhanced even in the presence of only weak eddy activity this casts doubt on the ability of parameterizations based solely on the eddy kinetic energy to adequately characterize the eddy diffusivity in regions of strongly varying mean flow such as the southern ocean the results are however consistent with the eddy transport and mixing variability predicted by potential vorticity based arguments

the dependence of southern ocean meridional overturning on wind stress an eddy resolving numerical model of a zonal flow meant to resemble the antarctic circumpolar current is described andanalyzedusing the framework of j marshallandt radko in additionto windand buoyancy forcing at the surface the model contains a sponge layer at the northern boundary that permits a residual meridional overturning circulation moc to exist at depth the strength of the residual moc is diagnosed for different strengths of surface wind stress it is found that the eddy circulation largely compensates for the changes in ekman circulation the extent of the compensation and thus the sensitivity of the moc to the winds depend on the surface boundary condition a fixed heat flux surface boundary severely limits the ability of the moc to change an interactive heat flux leads to greater sensitivity to explain the moc sensitivity to the wind strength under the interactive heat flux transformed eulerian mean theory is applied in which the eddy diffusivity plays a central role in determining the eddy response a scaling theory for the eddy diffusivity based on the mechanical energy balance is developed and tested the average magnitude of the diffusivity is found to be proportional to the square root of the wind stress the moc sensitivity to the winds based on this scaling is compared with the true sensitivity diagnosed from the experiments

interior water mass variability in the southern hemisphere oceans during the last decade abstractusing an argo dataset and the eccov4 reanalysis a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the southern hemisphe

on the dynamics of wind driven circumpolar currents the factors controlling the transport of the antarctic circumpolar current acc have recently been a topic of heated debate at the latitudes of drake passage potential vorticity contours are uninterrupted by coastlines and large amplitude flows are possible even with weak forcing and dissipation the relationship between the dynamics of circumpolar currents and inertial recirculations in closed basins is discussed in previous studies sverdrup balance and baroclinic adjustment theories have both been proposed as theories of the acc transport these theories predict the circumpolar transport as various simple functions of the surface wind stress a series of experiments is performed with a simple channel model with different wind strengths and different idealized basin geometries to investigate the relationship between wind strength and circumpolar transport the results show that baroclinic adjustment theories do predict transport in the special case of a periodic channel with no topographic variations or when the wind forcing is very weak more generally the transport is determined by a complex interplay between wind forcing eddy fluxes and topographic effects there is no support for the idea that sverdrup balance determines the transport through drake passage

southern ocean thermocline ventilation abstract an approximate mass volume budget in the surface layer of the southern ocean is used to investigate the intensity and regional variability of the ventilation process discussed here in terms of subduction and upwelling ventilation resulting from ekman pumping is estimated from satellite winds the geostrophic mean component is assessed from a climatology strengthened with argo data and the eddy induced advection is included via the parameterization of gent and mcwilliams together with eddy mixing estimates all three components contribute significantly to ventilation finally the seasonal cycle of the upper ocean is resolved using argo data the circumpolar averaged circulation shows an upwelling in the antarctic intermediate water aaiw density classes which is carried north into a zone of dense subantarctic mode water samw subduction although no consistent net production is found in the light samw density classes a large subduction of subtropical mode water stmw is observed the s

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

what sets the surface eddy mass flux in the southern ocean abstract the ocean circulation and climate advanced modelling occam global eddy permitting ocean general circulation model has been used to investigate the surface eddy mass flux in the southern ocean the isopycnal eddy mass flux in the surface layer is almost uniformly poleward and scales well with the local ekman transport this seems at odds with other models and observations suggesting topographic localization of the eddy fluxes with locally large rotational components integrated over the thermocline depth the eddy fluxes do show such topographic localization the surface eddy mass flux is mainly a consequence of the intermittent deepening of the mixed layer with the seasonal cycle which redistributes the ekman transport over the stack of layers that eventually become ventilated baroclinic instability gives rise to much smaller eddy induced transports independent of the framework in which the residual mean flow is analyzed isopycnal or geometric the eddy induced transport that opposes the

a laboratory model of thermocline depth and exchange fluxes across circumpolar fronts a laboratory experiment has been constructed to investigate the possibility that the equilibrium depth of a circumpolar front is set by a balance between the rate at which potential energy is created by mechanical and buoyancy forcing and the rate at which it is released by eddies in a rotating cylindrical tank the combined action of mechanical and buoyancy forcing builds a stratification creating a large scale front at equilibrium the depth of penetration and strength of the current are then determined by the balance between eddy transport and sources and sinks associated with imposed patterns of ekman pumping and buoyancy fluxes it is found that the depth of penetration and transport of the front scale like l and wel2 respectively where fw g9 e we is the ekman pumping g9 is the reduced gravity across the front f is the coriolis parameter and l is the width scale of the front last the implications of this study for understanding those processes that set the stratification and transport of the antarctic circumpolar current acc are discussed if the laboratory results scale up to the acc they suggest a maximum thermocline depth of approximately h 5 2 km a zonal current velocity of 4 6 cm s 21 and a transport t 5 150 sv 1 sv 106 m3 s 21 not dissimilar to what is observed

potential vorticity constraints on the dynamics and hydrography of the southern ocean abstract constraints on the hydrography and geostrophic velocity shear of the southern ocean implicit in its potential vorticity field are discussed and illustrated by diagnostic study of observed and modeled potential vorticity fields a stress driven thermodynamically inactive eddy resolving quasigeostrophic model of the southern ocean suggests that through the systematic erosion of potential vorticity gradients by geostrophic eddies the large scale flow equilibrates toward a state in which interior potential vorticity gradients are small observations of the large scale isopycnal distribution of potential vorticity ipv deduced from climatological hydrographic data reveal a much richer structure the most striking feature of the ipv field is the presence of large near surface gradients of ipv a vortocline coinciding with the axis of the antarctic circumpolar current acc to the south of this front potential vorticity pv is large to its north pv has low values and relative to those foun

eddy variability and energetics from direct current measurements in the antarctic circumpolar current south of australia two year time series measurements of current velocity and temperature in the subantarctic front saf south of australia from 1993 to 1995 provide estimates of eddy fluxes of heat and momentum across the antarctic circumpolar current acc and further insight into the variability of the acc the saf was found to be an energetic meandering jet with vertically coherent fluctuations varying on a timescale of 20 days with typical amplitude 30 cm s21 at 1150 dbar a daily varying coordinate frame that follows the direction of flow allowed mesoscale variability of the saf to be isolated from variability due to meandering of the front and proved very successful for examining eddy fluxes vertically averaged cross stream eddy heat flux was 11 3 kw m 22 poleward and significantly different from zero at 95 for fluctuations in the 2 90 day band zonally integrated this eddy heat flux 50 9 pw is more than large enough to balance heat lost south of the polar front and is as large as cross saf fluxes found in drake passage cross stream eddy momentum fluxes were small not significantly different from zero and of indeterminate sign but tending to decelerate the mean flow a relationship between vertical motion and meander phase identified in the gulf stream was found to hold for the acc eddy kinetic energy levels were similar to those in drake passage and southeast of new zealand eddy potential energy was up to an order of magnitude larger than at other acc sites most likely because meandering of the front is more common here baroclinic conversion was found to be the dominant mechanism by which eddies grow south of australia typical eddy growth time is estimated to be 30 days approximately twice as fast as in drake passage consistent with eddy energy growing rapidly downstream

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

an exploration of the role of transient eddies in determining the transport of a zonally reentrant current the meridional ekman transport in a zonally reentrant channel may be balanced by diabatic circulations standing eddies associated with topography or by lagrangian mean eddy mass fluxes a simple model is used to explore the interaction between these mechanisms a key assumption of this study is that diabatic forcing in the poleward edge of the channel acts to create lighter fluid as is the case with net freshwater fluxes into the southern ocean for weak wind forcing or strong diabatic constraint a simple scaling argument accurately predicts the level of baroclinic shear however given our understanding of the relative magnitudes of ekman flux and deep upwelling this is not the appropriate parameter range for the antarctic circumpolar current with stronger wind stresses eddies are prominent with baroclinic instability initially developing in the vicinity of large topography arguments have been advanced by a number of authors that baroclinic instability should limit the velocity shear leading to a stiff upper limit on the transport of the current however in the simulations presented here baroclinic instability is largely confined to the region of topographic highs and the approach to a current that is independent of the wind stress occurs gradually several recent parameterizations of transient eddy fluxes do not reproduce key features of the observed behavior

a toy model for the response of the residual overturning circulation to surface warming abstracta simple model for the deep ocean overturning circulation is presented and applied to study the ocean s response to a sudden surface warming the model combines one dimensional predictive r

the mediterranean sea overturning circulation abstractthe time mean zonal and meridional overturning circulations of the entire mediterranean sea are studied in both the eulerian and residual frameworks the overturning is characterized by cel

the diabatic deacon cell abstract southern ocean air sea fluxes from the coads dataset are examined for compatibility between buoyancy gain and northward ekman transport an analysis in density classes points to an upwelling of upper circumpolar deep water and subsequent buoyancy gain from air sea exchange as water flows northward in the ekman layer the upper circumpolar deep water layer is too shallow to admit southward geostrophic flow along topography and an eddy mass flux mechanism for southward transport in this layer to replenish the upwelling is advanced based on observed large scale potential vorticity gradients estimates of the strength and vertical structure of the meridional flow are given using repeated hydrographic sections and a new climatology

the dynamics of the antarctic circumpolar current abstract the dynamics of the antarctic circumpolar current acc in a near eddy resolving model of the southern ocean fram are investigated a streamwise coordinate system is used rather than a more conventional approach of considering zonally averaged quantities the motivation for this approach is the large deviation from a purely zonal flow made by the current comparisons are made with a zonal mean analysis of the same model it is found that the topographic form drag is the main sink of the momentum that is input by the wind however in contrast to a zonal mean analysis other terms namely horizontal mixing bottom friction and advection of momentum are no longer negligible the total effect of transient eddies is to produce a drag on the mean flow again in contrast to the zonally averaged case the vertical penetration of stress is considered a generalized formula is derived for the interfacial form stress averaged along a convoluted path and that includes nonquasigeostrophic effects the i

winter sea ice melting in the atlantic water subduction area svalbard norway herein we study a small area along the shelf west of spitsbergen near prins karls forland where warm saline atlantic water of the west spitsbergen current currently first encounters sea ice this sea ice is drifting in a coastal current that carries arctic water originating from the barents sea northward over the shelf our aim was to investigate whether melting of sea ice by atlantic water in this area might be a significant factor that could contribute to the formation of a cold halocline layer that isolates the sea ice from further melting from below observations of temperature and salinity profiles were collected during two winters via ctd srdl instruments deployed on harbor seals phoca vitulina and fed into a heat and freshwater budget box model in order to quantify the importance of melting relative to other processes that could transform the shelf water mass during winter cross frontal exchange of atlantic water from the west spitsbergen current driven by buoyancy forcing rather than ekman upwelling was determined to be the source of the heat that melted drift ice on the shelf some local sea ice formation did take place but its importance in the total heat and freshwater budgets appeared to be minor the data suggest that the production of a cold halocline layer was preceded by southerly winds and rapid drift ice melting

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography application to the southern ocean abstract recent estimates from observations and inverse models indicate that turbulent mixing associated with internal wave breaking is enhanced above rough topography in the southern ocean in most regions of the ocean abyssal mixing has been primarily associated with radiation and breaking of internal tides in this study it is shown that abyssal mixing in the southern ocean can be sustained by internal waves generated by geostrophic motions that dominate abyssal flows in this region theory and fully nonlinear numerical simulations are used to estimate the internal wave radiation and dissipation from lowered acoustic doppler current profiler ladcp ctd and topography data from two regions in the southern ocean drake passage and the southeast pacific the results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation previously inferred from finescale measurements in the region suggesting that it is one of the

overturning circulation pathways in a two basin ocean model abstracta toy model for the deep ocean overturning circulation in multiple basins is presented and applied to study the role of buoyancy forcing and basin geometry in the ocean s global overturning

antarctic ocean and sea ice response to ozone depletion a two time scale problem theresponseofthesouthernoceantoarepeatingseasonalcycleofozonelossisstudiedintwocoupledclimate models and is found to comprise both fast and slow processes the fast response is similar to the interannual signature of the southern annular mode sam on sea surface temperature sst onto which the ozone hole forcing projects in the summer it comprises enhanced northward ekman drift inducing negative summertime sst anomalies around antarctica earlier sea ice freeze up the following winter and northward expansion of the sea ice edge year round the enhanced northward ekman drift however results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice with sustained bursts of westerly winds induced by ozone hole depletion this warming from below eventually dominates over the cooling from anomalous ekman drift the resulting slow time scale response years to decades leads to warming of ssts around antarctica and ultimately a reduction in sea ice cover year round this two time scale behavior rapid cooling followed by slow but persistent warming is found in the two coupled models analyzed one with an idealized geometry and the other with a complex global climate model with realistic geometry processes that control the time scale of the transition from cooling to warming and their uncertainties are described finally the implications of these results are discussed for rationalizing previous studies of the effect of the ozone hole on sst and sea ice extent

planetary geometric constraints on isopycnal slope in the southern ocean abstracton planetary scales surface wind stress and differential buoyancy forcing act together to produce isopycnal surfaces that are relatively flat in the tropics subtropics and steep near the poles where they tend to outcrop tilted isopycnals in a rapidly rotating fluid are subject to baroclinic instability the turbulent mesoscale eddies generated by this instability have a tendency to homogenize potential vorticity pv along density surfaces in the southern ocean so the tilt of isopycnals is largely maintained by competition between the steepening effect of surface forcing and the flattening effect of turbulent spatially inhomogeneous eddy fluxes of pv here quasigeostrophic theory is used to investigate the influence of a planetary geometric constraint on the equilibrium slope of tilted density buoyancy surfaces in the so if the meridional gradients of relative vorticity and pv are small relative to then quasigeostrophic theory predicts ds dz f0 cot 0 a or equivalently r z

along slope variability of cross slope eddy transport in east antarctica circumpolar deep water cdw transport across the antarctic continental slope regulates the delivery of heat to the shelf and its availability to melt floating ice shelves the cross slope density field calculated from profiles collected by conductivity temperature depth tagged marine mammals on the east antarctic slope 0 160 e above 1 000 to 3 000 m isobaths indicates eddy driven overturning onshore transport of cdw and offshore transport of shallower antarctic surface water enhanced eddy activity determined by a spice standard deviation threshold in the cdw layer is present over about a third of the east antarctic slope analyzed significantly stronger cdw transport in regions of elevated spice variability produces subsurface temperature anomalies of 0 2 0 25 c relative to the east antarctic average estimating eddy diffusivity from the hydrography yields about 0 8 m2 s of warm cdw transport to the shelf break in high variability regions variability of eddy induced cdw transport influences the reservoir of heat available for transport across the shelf break

an idealized model of weddell gyre export variability recent observations suggest that the export of antarctic bottom water aabw from the weddell sea has a seasonal cycle in its temperature and salinity that is correlated with annual wind stress variations this variability has been attributed to annual vertical excursions of the isopycnals in the weddell gyre modifying the water properties at the depth of the orkney passage recent studies attribute these variations to locally wind driven barotropic dynamics in the northern weddell sea boundary current this paper explores an alternative mechanism in which the isopycnals respond directly to surface ekman pumping which is coupled to rapidly responding mesoscale eddy buoyancy fluxes near the gyre boundary a conceptual model of the interface that separates weddell sea deep water from circumpolar deep water is described in which the bounding isopycnal responds to a seasonal oscillation in the surface wind stress different parameterizations of the mesoscale eddy diffusivity are tested the model accurately predicts the observed phases of the temperature and salinity variability in relationship to the surface wind stress the model despite its heavy idealization also accounts for more than 50 of the observed oscillation amplitude which depends on the strength of the seasonal wind variability and the parameterized eddy diffusivity these results highlight theimportanceofmesoscaleeddiesinmodulatingtheexportofaabwinnarrowboundarylayersaroundthe antarctic margins

on the parameterization of geostrophic eddies in the ocean abstract an attempt is made to incorporate into a two layer zonally averaged channel ocean model the important transfers achieved by a geostrophic eddy field using gross parameterizations rather than resolving individual eddy events it is shown that a representation of the eddy field as an explicit diffuser of potential vorticity can give a reasonable description of the interaction between the eddies and mean flow provided care is taken to satisfy the attendant constraints that the zonally invariant channel geometry imposes on the eddy fields

direct estimate of lateral eddy diffusivity upstream of drake passage abstractthe first direct estimate of the rate at which geostrophic turbulence mixes tracers across the antarctic circumpolar current is presented the estimate is computed from the spreading of a tracer released upstream of drake passage as part of the diapycnal and isopycnal mixing experiment in the southern ocean dimes the meridional eddy diffusivity a measure of the rate at which the area of the tracer spreads along an isopycnal across the antarctic circumpolar current is 710 260 m2 s 1 at 1500 m depth the estimate is based on an extrapolation of the tracer based diffusivity using output from numerical tracers released in a one twentieth of a degree model simulation of the circulation and turbulence in the drake passage region the model is shown to reproduce the observed spreading rate of the dimes tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m2 s 1 and peaks at the steering level near 2 km where the eddy ph

acceleration and overturning of the antarctic slope current by winds eddies and tides all exchanges between the open ocean and the antarctic continental shelf must cross the antarctic slope current asc previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability yet the mechanisms responsible for setting the asc s transport and structure have received relatively little attention in this study the roles of winds eddies and tides in accelerating the asc are investigated using a global ocean sea ice simulation with very high resolution 1 48 grid spacing it is found that the circulation along the continental slope is accelerated both by surface stresses ultimately sourced from the easterly winds and by mesoscale eddy vorticity fluxes at the continental shelf break the asc exhibits a narrow 30 50 km swift 0 2 m s 1 jet consistent with in situ observations in this jet the surface stress is substantially reduced and may even vanish or be directed eastward because the ocean surface speed matches or exceeds that of the sea ice the shelfbreak jet is shown to be accelerated by tidal momentum advection consistent with the phenomenon of tidal rectification consequently the shoreward ekman transport vanishes and thus the mean overturning circulation that steepens the antarctic slope front asf is primarily due to tidal acceleration these findings imply that the circulation and mean overturning of the asc are not only determined by near antarctic winds but also depend crucially on sea ice cover regionally dependent mesoscale eddy activity over the continental slope and the amplitude of tidal flows across the continental shelf break

can eddies set ocean stratification abstract a simple theory is presented for the buoyancy anomaly and depth of penetration of a warm lens created by a surface buoyancy flux and ekman pumping in an initially homogeneous rotating fluid it is assumed that the overturning of isopycnals induced by pumping and differential heating balances the counteroverturning tendency of baroclinic instability baroclinic eddies not only develop on the stratified lens but also play a fundamental role in setting its stratification the theory is successfully tested against numerical and laboratory experiments in which the mechanically induced deepening of a buoyant lens is arrested by its baroclinic instability finally the possibility is discussed that the eddy transfer process studied here might play a role in setting the stratification and depth of the main thermocline in the ocean

the connection between southern ocean winds the atlantic meridional overturning circulation and indo pacific upwelling abstractcoupled gcm simulations are analyzed to quantify the dynamic effect of southern ocean so winds on transports in the ocean it is found that the closure for skew diffusivity in the non eddy resolving ocean model does not allow for a realistic eddy saturation of the zonal transports in the so in response to the wind changes and that eddy compensation of the meridional transports in the so is underestimated too despite this underestimated eddy compensation in the so however and in contrast to previous suggestions the atlantic meridional overturning circulation amoc strength is almost insensitive to so winds in the limit of weak so winds the amoc waters upwell not in the so but rather in the tropical indo pacific through their effect on sea ice weaker so winds also lead to less production of antarctic bottom water and therefore a deeper and stronger amoc

the deacon cell and the other meridional cells of the southern ocean abstract the meridional circulation cells of the southern ocean are investigated using the results from a fine resolution primitive equation model zonal integration along depth levels shows the classical series of meridional cells but integration along density layers shows a number of differences including the virtual disappearance of the deacon cell to investigate the differences the meridional transport is calculated as a function of both density and depth the results show that the deacon cell is associated with systematic changes in the depth of density surfaces between the western boundary current region off south america and the return flow in the interior of the ocean water flowing on each density surface produces a meridional cell with a vertical excursion of a few hundred meters thew cells combine without water crossing density surfaces to produce a single integrated deacon cell extending from the surface to below 2000 m the results also show that at each latitude water on each of the

structural effects of tidal exposures on mudflats along the french guiana coast wetting and drying cycles on intertidal mudflats vary considerably with altitude modifying the physical characteristics of surface sediment in ways favoring or not plant colonization in this context sediment properties were investigated by means of laboratory experiments and field surveys on a wide range of fluid to desiccated muds from the highly dynamic coastline of french guiana changes in physical parameters such as sediment erodability yield stress water loss and pore water salinity indicated a long term compaction of mudflats as well as fluctuations related to the successive wetting and drying cycles mudcracks constituted a spectacular feature representative of the contractional stress they re opened after a few days of dewatering and re healed during the subsequent wetting from the analysis of field data the trapping of avicennia germinans propagules in ephemeral mudcracks turned out to be responsible of 95 of the sprouting on the coastal fringe thus desiccation process usually considered as a typical feature of erosion revealed herein to be a major mechanism of colonization this mechanism undoubtedly affects the 1600 km long amazon coastal system and is believed to exist in many other tropical environments submitted to important siltation

rapid changes in mixed layer stratification driven by submesoscale instabilities and winds 1 submesoscale eddies generated by baroclinic instability of upper ocean fronts lead to rapid restratification of the mixed layer on a time scale of days this restratification can be opposed by a down front wind stress acting in the direction of the geostrophic velocity that drives a surface ekman flow from the dense side to the light side of the front to arrest the slumping of isopycnals a scaling diagnostic is suggested to determine whether the effect of eddies or wind dominates under different conditions using a numerical model we investigate the juxtaposition of submesoscale eddies and down front winds acting on the mixed layer by estimating the eddy induced overturning stream function in the mixed layer we separate the along and cross isopycnal fluxes of buoyancy associated with submesoscale mixed layer eddies and demonstrate the need for parameterization of the advective along isopycnal flux though the cross front transport of buoyancy induced by the down front component of the wind opposes restratification by mixed layer eddies it becomes diminished as the eddies and growth of the frontal instability disrupt alignment between the wind and frontal axis

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

lagrangian analysis of the meridional overturning circulation in an idealized ocean basin the lagrangian ocean model is used as a tool to simulate the response of the basin scale overturning circulation to spatially variable diapycnal mixing in an idealized ocean basin the model explicitly calculates the positions velocities and tracer properties of water parcels owing to its lagrangian formulation numerical diffusion is completely eliminated and water parcel pathways and water mass ages can be quantified within the framework of the discrete advective transit time distribution to illustrate the ventilation pathways simulated trajectories were tracked backward in time from the interior ocean to the surface mixed layer where the water parcel was last in contact with the atmosphere this new diagnostic has been applied to examine the response of the meridional overturning circulation to highly localized diapycnal mixing through sensitivity experiments in particular the focus is on three simulations the first holds vertical diffusivity uniform in the second the vertical diffusivity is confined within an equatorial box and the third simulation has a diffusivity pattern based on idealized hurricane induced mixing domain integrated deep ventilation rates and heat transport are similar between the first two cases however locally enhanced mixing yields about 30 younger water mass age in the tropical thermocline due to intense localized upwelling in the third simulation a slower ventilation rate of deep waters is found to be due to the lack of abyssal mixing these results are interpreted using the classical theories of abyssal circulation highlighting the strong sensitivity of the ventilation pathways to the spatial distribution of diapycnal mixing

the antarctic slope current in a changing climate the antarctic slope current asc is a coherent circulation feature that rings the antarctic continental shelf and regulates the flow of water towards the antarctic coastline the structure and variability of the asc influences key processes near the antarctic coastline that have global implications such as the melting of antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation recent theoretical modeling and observational advances have revealed new dynamical properties of the asc making it timely to review earlier reviews of the asc focused largely on local classifications of water properties of the asc s primary front here we instead provide a classification of the current s frontal structure based on the dynamical mechanisms that govern both the along slope and cross slope circulation these two modes of circulation are strongly coupled similar to the antarctic circumpolar current highly variable motions such as dense overflows tides and eddies are shown to be critical components of cross slope and cross shelf exchange but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations results linking the asc to larger modes of climate variability such as el nino show that the asc is an integral part of global climate an improved dynamical understanding of the asc is still needed to accurately model and predict future antarctic sea ice extent the stability of the antarctic ice sheets and the southern ocean s contribution to the global carbon cycle

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography theory abstract observations and inverse models suggest that small scale turbulent mixing is enhanced in the southern ocean in regions above rough topography the enhancement extends o 1 km above the topography suggesting that mixing is supported by the breaking of gravity waves radiated from the ocean bottom in this study it is shown that the observed mixing rates can be sustained by internal waves generated by geostrophic motions flowing over bottom topography weakly nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow vigorous inertial oscillations are driven at the ocean bottom by waves generated at steep topography the wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations differing substantially from the classical lee wave problem the theoretical predictions are tested versus two dimensional high resolution numerical simulations with parameters representative of

sensitivity of the southern ocean overturning circulation to surface buoyancy forcing 1 the sensitivity of the southern ocean overturning to altered surface buoyancy forcing is investigated in a series of eddy permitting idealised simulations the modelled response indicates that heat and freshwater fluxes in the southern hemisphere mid latitudes may play a significant role in setting the strength of the overturning circulation enhanced buoyancy fluxes act to increase the meridional overturning up to a limit approaching the wind driven ekman transport the sensitivity of the overturning to surface buoyancy forcing is strongly dependent on the relative locations of the wind stress profile buoyancy forcing and upwelling region the numerical simulations provide support for the hypothesis that changes in upwelling during deglaciations may have been driven by changes in heat and freshwater fluxes instead of or in addition to changes in wind stress

how wind forcing and air sea heat exchange determine the meridional temperature gradient and stratification for the antarctic circumpolar current mesoscale oceanic eddies have a profound effect on the meridional circulation in the antarctic circumpolar region previous studies have shown that eddies transport heat poleward to balance the heat lost by the ocean to the atmosphere in the waters around antarctica and also transport eastward momentum downward at a rate comparable to the amount of momentum put into the water column by the wind stress using the poleward eddy heat fluxes to relate air sea heat loss and wind stress we find that the meridional temperature gradient in the circumpolar region is determined by the ratio of the air sea heat loss to the zonal wind stress including a widely used parameterisation where poleward eddy heat fluxes are proportional to the mean meridional temperature gradient we find that the slope of isotherms or isopycnals across the circumpolar zone is determined by the wind stress further assuming no cross isopycnal mixing in the interior ocean we find that the stratification in the deep ocean is determined by the ratio of air sea heat loss to zonal wind stress squared the poleward eddy heat fluxes also represent a southward eddy mass transport in the upper water column in density coordinates the vertical gradient of this eddy mass transport is the meridional component of the eddy stokes drift which is equal to the difference between the lagrangian and eulerian mean velocities in the circumpolar region because there can be no zonally averaged geostrophic eulerian meridional velocity across the circumpolar region above the topography this southward eddy stokes drift provides a mechanism by which circumpolar deep water can flow southward across the circumpolar zone eddy heat fluxes which are central to the mass momentum heat and energy balances in the circumpolar region provide a catalyst for relating the roles of wind and buoyancy forcing in setting the overall circulation for the southern ocean

the surface branch of the zonally averaged mass transport circulation in the troposphere the near surface branch of the overturning mass transport circulation in the troposphere containing the equatorward flow is examined in isentropic and geometric coordinates a discussion of the zonal momentum balance within isentropic layers shows that the equatorward flow at a given latitude is confined to isentropic layers that typically intersect the surface at that latitude as a consequence of mass transport within the surface mixed layer much of the equatorward flow occurs in layers with potential temperatures below the mean surface potential temperature in the conventional transformed eulerian mean formulation for geometric coordinates the surface branch of the overturning circulation is represented in an unrealistic manner streamlines of the residual circulation do not close above the surface a modified residual circulation is introduced that is free from this defect and has the additional advantage that its computation unlike that of the conventional residual circulation does not require division by the static stability which may approach zero in the planetary boundary layer it is then argued that cold air advection by the residual circulation is responsible for the formation of surface inversions at all latitudes in idealized gcms with weak thermal damping also included is a discussion of how a general circulation theory for the troposphere must be built upon a theory for the near surface meridional mass fluxes

circumpolar response of southern ocean eddy activity to a change in the southern annular mode 1 analysis of satellite altimeter data reveals anomalously high eddy kinetic energy eke in the antarctic circumpolar current acc during the period 2000 2002 around 2 3 years earlier 1998 the circumpolar eastward wind stress as quantified by the southern annular mode sam showed a significant positive peak and we have shown previously that the acc peaked around 1998 in response an eddy resolving ocean model is used to investigate the delay between wind forcing and the eddy response and demonstrates that the lag is due to the time taken to influence the deep circulation of the acc winds over the southern ocean have shown a strong climatic increase over the past few decades if this increase in winds is also reflected as an increase in eddy activity as our analysis suggests it might then the increased poleward heat flux may have played a significant role in the observed warming of the southern ocean citation meredith m p and a m hogg 2006 circumpolar response of southern ocean eddy activity to a change in the southern annular mode geophys res lett 33 l16608 doi 10 1029 2006gl026499

standing and transient eddies in the response of the southern ocean meridional overturning to the southern annular mode abstractto refine the understanding of how the southern ocean responds to recent intensification of the southern annular mode sam a regional ocean model at two eddy permitting resolutions was forced with two synthetic interannual forcings the first forcing corresponds to homogeneously intensified winds while the second concerns their poleward intensification consistent with positive phases of the sam resulting wind driven responses differ greatly between the nearly insensitive antarctic circumpolar current acc and the more sensitive meridional overturning circulation moc as expected eddies mitigate the response of the acc and moc to poleward intensified winds however transient eddies do not necessarily play an increasing role in meridional transport with increasing resolution as winds and resolution increase meridional transport from standing eddies becomes more efficient at balancing wind enhanced overturning these results question the current paradigms on the role of eddies and present

on the factors controlling the eddy induced transport in the antarctic circumpolar current abstractthis study examines eddy driven material transport by analyzing trajectories of lagrangian particles in an idealized model of the southern ocean the main focus is on the direction of the transport in the latitude depth plane as well as on the magnitudes of the vertical and meridional particle dispersion in particular this transport is along the mean isopycnals in the control simulation but changes its direction and intensity in a series of sensitivity experiments with artificially modified currents the main new conclusion is that the direction of the transport is determined by the three dimensional interplay between the zonal background flow and the transient eddies the stationary meanders play a secondary role the key parameter here is the strength of the zonal advection relative to the eddy magnitudes whereas the mean vertical shear in the zonal velocity is of secondary importance in particular stronger mean zonal advection leads to steeper orientation of the eddy fluxes and deeper pe

energetics of the global ocean the role of layer thickness form drag abstract understanding the role of mesoscale eddies in the global ocean is fundamental to gaining insight into the factors that control the strength of the circulation this paper presents results of an analysis of a high resolution numerical simulation in particular the authors perform an analysis of energetics in density space such an approach clearly demonstrates the role of layer thickness form drag residual effects of hydrostatic pressure perturbations which is hidden in the classical analysis of the energetics of flows for the first time in oceanic studies the global distribution of layer thickness form drag is determined this study provides direct evidence to verify some basic characteristics of layer thickness form drag that have often been assumed or speculated about in previous theoretical studies the results justify most of the previous assumptions and speculations including those associated with i the presence of an oceanic energy cycle explaining the relationship between layer th

isolating the role of mesoscale eddies in mixing of a passive tracer in an eddy resolving model 1 this study examines the role of mesoscale eddies in distribution of chlorofluorocarbon cfc in a numerical model of the north atlantic our main conclusions are based on a comparison of two eddy resolving experiments one with and one without eddy advection of cfc the cfc distributions in these two experiments exhibit substantial differences within the subpolar gyre in particular in the presence of eddies the horizontal distribution of cfc in the upper 1000 m is more uniform and the cfc concentration is lower in the lower 1500 m our analysis demonstrates that these basin wide differences are caused by the interactions of eddy advection with convection and mean advection in several isolated locations the corresponding eddy flux divergence terms are spatially non uniform in magnitude their effects are often nonlocal and sometimes work against the spreading of cfc being carried out by the mean advection these conclusions are further confirmed by a third experiment in which the eddy advection was replaced by a down gradient diffusive parameterization our results demonstrate that advection by mesoscale eddies is crucial to the mixing of atmospheric gasses into the ocean and outline difficulties in representing eddies by the down gradient diffusion

standing eddies in the meridional overturning circulation abstractthe role of standing eddies for the meridional overturning circulation moc is discussed the time mean isopycnal meridional streamfunction is decomposed into a time and zonal mean part a standing eddy part and a transient eddy part it turns out that the construction of an isopycnal moc with an exactly vanishing standing eddy part has to be performed by zonal integration along depth dependent horizontal isolines of time mean density in contrast zonal integration along time mean geostrophic streamlines generally only leads to an isopycnal moc with a reduced standing eddy part a generalized approach of constructing meridional transport streamfunctions by two tracer fields and the generalized way to neutralize the corresponding standing eddy part is given to summarize the discussion using the results of an idealized southern ocean model it is demonstrated that neglecting the depth dependence of the zonal integration paths by integrating along density contours or geostrophic streamlines of a

importance of mesoscale eddies and mean circulation in ventilation of the southern ocean this study examines the relative importance of the mean advection and mesoscale currents in the property exchange between the southern ocean mixed layer and downstream in the upper 2000 meters this exchange is referred to as ventilation a new highly efficient offline tracer model employed here uses pre calculated velocities to advect dynamically passive tracers two idealized tracers are considered the boundary impulse response bir tracer which helps to determine the ventilation pathways and time scales and the transient surface tracer tst which is relevant to transient atmospheric tracers the importance of eddies is isolated by contrasting the control simulation with a simulation without mesoscale currents the analysis reveals complex three dimensional ventilation pathways controlled by the interplay between the mean advection and eddy induced spreading the mean currents carry the tracers eastward within acc and contribute to the formation of the antarctic intermediate water aaiw in the south pacific and south atlantic the main effect of eddies is to disperse tracers away from the mean pathways and this dispersion acts to retain the bir tracer in the atlantic and indian sectors and reduce the upstream influence of these regions on the south pacific in addition the eddy induced along isopycnal spreading within acc increases the ventilated depth and the inventory of tst the results can be used to interpret distribution of tracers in the ocean in numerical simulations and observations this article is protected by copyright all rights reserved

an attempt to understand the behavior of dissolved organic carbon in coastal aquifers of pondicherry region south india groundwaters of the coastal region are significant and serve as a fragile ecosystem in the sedimentary terrain the pondicherry region is characterized by different geological formations of distinct geological epochs cretaceous tertiary and quaternary ninety three samples were collected from specific aquifers with respect to spatial distribution alluvium 31 upper cuddalore 13 lower cuddalore 13 other tertiary 7 cretaceous 24 and mixed multiple completion aquifer 5 the collected samples were analyzed for major ions ca2 mg2 na k hco3 cl po42 so42 f and doc stables isotopes of 18o d and 13c were also analyzed along with heavy metals like al ba fe sr cd and zn the 18o ranges between 6 85 and 2 15 and d ranges between 43 94 and 19 41 the distribution of these environmental isotopes in groundwater of this layered aquifer sequence was also attempted a comparison of the isotopic data with the rainfall local meteoric water line with a equation of d 7 398 18o 5 067 indian meteoric water line and global meteoric water line was performed the 13c values for groundwater ranges from 5 3 to 18 1 the result indicates that the groundwater in the study area is mainly meteoric in origin and few samples show evidence of evaporation the dissolved organic carbon doc is a very important component in biogeochemical cycling of elements characterized by high susceptibility to leaching the range of the doc in the study area is 0 16 mg l factor analysis was applied to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry the alluvium aquifers show a complex hydrogeochemistry than the older aquifers the major factor influencing the hydrogeochemistry of the region is rock water interaction and anthropogenic processes hence metal mobility of the groundwater shows the correlation of metal bonding and doc the relation between the doc and heavy metal concentration in the aquifers was also identified

diapycnal and isopycnal transports in the southern ocean estimated by a box inverse model quantitative descriptions of circumpolar deep water upwelling and evolution into a lighter mode and heavier bottom waters in the southern ocean are still not well constrained here data from two occupations of eight hydrographic sections are combined and used in a box inverse model to estimate isopycnal and diapycnal transportsinthesouthernocean amixedlayerboxallowsdiapycnaltransportsinthesurfacemixedlayertobe estimated separately current velocity at 1000 dbar was constrained by the mean velocity field estimated from subsurfacefloatdriftdata theestimatedisopycnaltransportsarelargelyconsistentwithpastestimatesandwith outputs of three ocean general circulation models the estimated subduction and upwelling at the base of the southernoceanmixedlayershowthatuppercircumpolardeepwaterupwells 16615and17621sv where 1sv 10 6 m 3 s 21 by different inversion methods and evolves into heavier lower circumpolar deep water 5 6 13 and 6 6 18sv and bottom water 86 9a nd 86 13sv or lighter mode and intermediate waters 96 18 and 13 6 24sv meridional transport in the surface mixed layer is due to northward ekman transport and mostly southward eddy transport in seasonal ice covered areas near antarctica a significant 14 6 14sv southward transport was found the southward eddy transport is largest north of the antarctic circumpolar currentanddecreasespolewardbecauseofthepolewarddecreaseintheeddydiffusivity theinteriordiapycnal transports which can be either upward gaining buoyancy or downward gaining density are comparable in magnitude to the horizontal diapycnal transports within the surface mixed layer

an eddy permitting southern ocean state estimate abstract an eddy permitting general circulation model of the southern ocean is fit by constrained least squares to a large observational dataset during 2005 06 data used include argo float profiles ctd synoptic sections southern elephant seals as oceanographic samplers seaos instrument mounted seal profiles xbts altimetric observations envisat geosat jason 1 and ocean topography experiment topex poseidon and infrared and microwave radiometer observed sea surface temperature an adjoint model is used to determine descent directions in minimizing a misfit function each of whose elements has been weighted by an estimate of the observational plus model error the model is brought into near agreement with the data by adjusting its control vector here consisting of initial and meteorological boundary conditions although total consistency has not yet been achieved the existing solution is in good agreement with the great majority of the 2005 and 2006 southern ocean observations and better repr