pacific equatorial subsurface countercurrent velocity transport and potential vorticity concurrent shipboard adcp and ctd sections are used to calculate the mean velocity transport and potential vorticity fields associated with the pacific equatorial subsurface countercurrents sccs averaged in stream coordinates the core eastward velocity of the sccs is a factor of 2 higher than previously reported means but the estimated transports are unchanged the meridional profile of zonal velocity along isopycnals is sharply peaked and nearly linear on each flank of the current the sharp and strong reversal of relative vorticity over a distance of 20 km at the jet core sharpens the coincident potential vorticity front this front separates a region of very low homogeneous potential vorticity on the equatorward side from a homogeneous high potential vorticity region on the poleward side each potential vorticity pool extends well beyond the edges of the scc into regions of westward flow on the equatorward sides of the sccs this westward flow is the equatorial intermediate current in the western pacific but in the central and eastern parts of the basin it is off the equator in deep extensions of the south equatorial current in the central and eastern regions the net westward transport in an isopycnal layer between the sccs exceeds the combined eastward scc transport in that layer the net zonal transport between the scc cores is highly divergent in the east and convergent in the west this pattern together with downstream changes in scc density indicates that neither they nor the westward return flows are simple inertial recirculations strong diapycnal processes must be involved

effects of topography on baroclinic instability abstractthe importance of bottom topography in the linear baroclinic instability of zonal flows on the plane is examined by using analytical calculations and a quasigeostrophic eddy resolving numerical model the particular focus is on the effects of a zonal topographic slope compared with the effects of a meridional slope a zonal slope always destabilizes background zonal flows that are otherwise stable in the absence of topography regardless of the slope magnitude whereas the meridional slopes stabilize destabilize zonal flows only through changing the lower level background potential vorticity gradient beyond a known critical value growth rates phase speeds and vertical structure of the growing solutions strongly depend on the slope magnitude in the numerical simulations configured with an isolated meridional ridge unstable modes develop on both sides of the ridge and propagate eastward of the ridge in agreement with analytical results

deep oceanic zonal jets constrained by fine scale wind stress curls in the south pacific ocean a high resolution coupled gcm study 1 oceanic alternating zonal jets at depth have been detected ubiquitously in observations and ocean general circulation models gcms such oceanic jets are generally considered as being generated by purely oceanic processes here we explore a possible air sea interaction induced by surface signatures of the deep zonal jets using an eddy permitting coupled atmosphere ocean gcm cgcm the 23 year cgcm integration reproduces bands of latitudinally narrow alternating jets in the southeast pacific they extend from the sea surface to well below the main thermocline and are embedded in the large scale westward flowing south equatorial current the latter mostly confined above the thermocline these jets generate fine scale sea surface temperature sst anomalies through the advection of zonal temperature gradients the atmospheric boundary layer appears to respond thermally to this fine scale sst field which induces fine scale wind stress anomaly through atmospheric pressure adjustment as indicated by a good spatial correlation between the sst laplacian field and the fine scale wind stress curl a sverdrup calculation on the wind stress field of the cgcm predicts fine scale zonal currents driven by the meridional gradient of the fine scale wind stress curl the positions of these sverdrup currents are generally coincident with those of the original zonal jets and the sverdrup prediction explains roughly half of the amplitudes of the jets while the original cause of the deep zonal jets simulated in our cgcm is unidentified this analysis suggests that there is likely a positive air sea feedback the jets generate fine scale wind stress curl that reinforces themselves through the sverdrup dynamics

direct measurement of the deep circulation within the brazil basin abstract in support of the deep basin experiment part of the world ocean circulation experiment a large number of neutrally buoyant floats were released within the brazil basin during the 1990s in an attempt to measure directly the circulation in the deep ocean interior three levels corresponding to the three major subthermocline water masses were selected and results from the deeper two north atlantic deep water nadw and antarctic bottom water aabw are described at this writing processing of acquired tracking data is incomplete hence this paper reports on the progress of the observational program and gives our initial conclusions it appears that the flow in the deep brazil basin is unlike previous conjectures in which the circulation patterns can be characterized as being primarily meridional both along the western boundary and in the interior the existence of a deep western boundary current dwbc is quite clear in the float data at the nadw level but less prominent in the aabw and the interior flow is dominantly zonal with unexpectedly small meridional space scales integral time scales are long of order 20 30 days and eddy kinetic energy levels are low of order 1 cm2 s2 in spite of the low energy levels a surprising number of our floats became caught up in vortices a line of seamounts extending offshore near 20 s known as the vitoria trindade seamounts interrupts the dwbcs and is the location for eddy formation and apparent flow away from the boundary into the interior although it has been speculated that this could feed a narrow zonal current of nadw the namib col current our float trajectories suggest a return to the western boundary rather than a continuation to the east

jet structure and scaling in southern ocean models abstract the jet structure of the antarctic circumpolar current acc simulated by two general circulation models gcms fram fine resolution antarctic model and pop parallel ocean program is examined in relation to the bottom topography field despite differences in configuration both gcms display similar behavior the model acc consists of a number of distinct current cores superimposed on broader scale flow the jets display temporal and spatial including vertical coherence with maximum velocities occurring at the surface it is shown that multiple jets can arise in wind forced baroclinic quasigeostrophic flow the main factors influencing the number and spacing of jets are found to be the bottom topography and the proximity of lateral boundaries the meridional spacing of jets on a flat bottomed plane is consistent with the rhines scaling criterion for barotropic plane turbulence with a small modification due to baroclinicity and the presence of meridional boundaries when a zonally orient

the influence of the hawaiian archipelago upon the wind driven subtropical gyre in the western north pacific in the middle of the subtropical gyre in the western north pacific is the subtropical counter current comprised of at least three narrow bands of eastward geostrophic mean flow near 20 n 24 n and 26 n each extending from the sea surface through the main pycrocline the origin of these narrow bands of eastward mean flow has not previously been explained in this study these bands are shown in the mean to extend zonally from the philippine sea i e 140 e to the vicinity of the hawaiian archipelago i e 160 w east of there they cannot be found therefore a hypothesis is presented wherein the hawaiian archipelago extending from 19 n to 26 n near 165 w is seen to act as an effective barrier modifying the response of the western subtropical north pacific to wind driven effects in the eastern subtropical north pacific and in so doing giving rise to these bands of eastward mean flow in the middle of the western subtropical gyre a test of this hypothesis utilizes a sverdrup 1947 model driven by the annual long term mean wind stress curl constructed on a 2 latitude longitude grid from synoptic 6 hourly surface wind observations for the 13 year period 1968 1980 two model simulations are conducted one in the absence of the hawaiian archipelago and one in the presence of it in the absence of the archipelago none of the bands of eastward mean flow are simulated in the presence of the archipelago the narrow bands of eastward mean flow at 20 n 26 n and 24 n are simulated although the latter band is very weak these narrow bands of eastward flow are shown to occur in response to the deflection northward of the wind driven geostrophic streamlines in the central subtropical north pacific by the hawaiian archipelago

sequence stratigraphy and depositional controls in late proterozoic early cambrian sediments of amadeus basin central australia the amadeus basin is an isolated intracratonic basin at the center of the australian continent which because of its location and geometry provides an ideal opportunity to investigate depositional controls to this end more than 6 000 km of seismic data in conjunction with a field and well log program have been used in a study of the late proterozoic early cambrian arumbera sandstone the arumbera sandstone was deposited as two major depositional sequences in a shallow marine and deltaic or coastal plain setting similar to that of the devonian catskill delta of north america sediment was supplied from the southwest by heavily laden braided streams during the deposition of the first sequence when sea level was at its maximum sedimentation appears to have been largely aggradational as sediment supply balanced or exceeded basin subsidence the sediments were probably deposited in a coastal or delta plain setting where small scale deltas prograded across the carbonate platform sediments of the julie formation during the accumulation of the second sequence sea level fell rapidly exposing large areas of sediment deposited during the first cycle and restricting edimentation to two steep sided rapidly subsiding subbasins deposition was largely progradational as major deltaic complexes developed on the southern and southwestern margins of the subbasins between the major delta complexes a depositional environment similar to that of the first sequence predominated in the deep subbasins the arumbera sandstone forms a continuous depositional unit across the proterozoic cambrian boundary the unconformable nature of that boundary over much of the earth possibly could be the result of a major eustatic sea level drop the final geometry of the arumbera sandstone and the nature of its sediments were determined largely by local subsidence rates subsidence briefly outstripped sediment supply during a stage of crustal extension as the basin evolved during deposition of sequence 1 depositional space and facies distribution were however fine tuned by salt tectonics and major sea level cycles as at passive margins sequence boundaries appear to be controlled by sea level cycles other variables such as climate the lack of vascular plants and the uplift of the source area were also factors in controlling deposition

interplay between depositional facies diagenesis and early fractures in the early cretaceous habshan formation jebel madar oman abstract diagenesis and fracturing can significantly alter petrophysical properties of subsurface carbonate reservoirs but the impacts of these processes at the inter well scale are hard to predict however the initial distribution of sedimentary facies is easier to predict and could template future diagenetic transformation and potentially influence fracturing as well this paper provides a case study investigating the mutual influence of depositional facies on diagenesis and interpreted early fractures in the berriasian valanginian habshan formation in jebel madar oman the habshan formation mostly comprises ooidal limestones but dolomitized beds a few metres in thickness and laterally correlatable over at least 5 km are present discordant vertical dolomite streaks are present in the limestone but are rare the various sedimentary and diagenetic processes were investigated using fieldwork xrd analysis petrography and geochemistry major and trace elements stable carbon and oxygen isotopes and strontium isotopes the lithologies consist of mud lean ooidal grainstones mud rich ooidal packstones and bioturbated limestones the changes in the amount of fine grained sediment suggest changing energy conditions at a backshoal position of a carbonate platform the mud lean versus mud rich depositional textures impacted on early diagenesis by promoting abundant calcite cementation in the mud lean ooidal grainstones and dolomitization in the mud rich packstones the discordant bodies interpreted as sediment filled early fractures are dolomitized in the same way as the mud rich ooidal packstones dolomitization occurred probably during the valanginian hauterivian in a shallow burial setting and was most likely caused by seepage reflux salt doming post dated dolomitization of the habshan formation the results of this study document the inter relationship between sedimentary facies early diagenesis and early fractures

mechanisms for the emergence of ocean striations in the north pacific recent observations suggest that the mean mesoscale oceanic zonal velocity field is dominated by alternating jet like features often referred to as striations here the generating dynamics of northeast pacific striations are explored with a set of 120 year eddy permitting model simulations simulations are conducted with decreasing complexity toward idealized configurations retaining the essential dynamics and forcing necessary for striation development for each simulation we diagnose the spin up of the ocean model and the sensitivity of striation generation to topography coastal geometry and wind stress which modulates the gyre circulation and the nonlinearity of the flow field results indicate that northeast pacific striations develop predominantly at the eastern boundary and migrate westward in congruence with beta plumes in both the nonlinear and quasi linear regimes mean striations are governed by coastline geometry which provides quasi steady vorticity sources energized by eastern boundary current instabilities

gyres and jets inversion of tracer data for ocean circulation structure abstract this paper describes a quasi 3d bayesian inversion of oceanographic tracer data from the south atlantic ocean initially one active neutral density layer is considered with an upper and lower boundary the available hydrographic data are linked to model parameters water velocities diffusion coefficients via a 3d advection diffusion equation a robust solution to the inverse problem can be obtained by introducing prior information about parameters and modeling the observation error this approach estimates both horizontal and vertical flow as well as diffusion coefficients a system of alternating zonal jets is found at the depths of the north atlantic deep water consistent with direct measurements of flow and concentration maps a uniqueness analysis of the model is performed in terms of the oxygen consumption rate the vertical mixing coefficient bears some relation to the bottom topography even though the authors do not incorporate topography into their model the method is extended to a m

geometric scale invariance genesis and self organization of polygonal fracture networks in granitic rocks abstract we documented polygonal fracture networks in the tuolumne intrusive suite sierra nevada batholith by collecting data on the size orientation and length of fractures and fracture bound polygons in nearly isotropic granitic rocks polygonal fracture networks are constrained to sheets of rock sub parallel to the underlying rock with the sheets bound above and below by fractures i e free surfaces data indicate that most geometric characteristics of the polygonal fracture networks are scale invariant large m scale networks exhibit the same geometry as small cm scale networks a linear correlation exists between sheet thickness and average polygon size polygons within the networks are anisotropic with the degree of anisotropy correlated with the degree of sheet curvature the preferred orientation of the polygons correlates with the inclination of the sheet with long axes of polygons parallel to sheet strike based on geometry we suggest that the polygonal fracture networks in granitic rocks observed in this study formed from temperature fluctuations that caused thermal expansion and contraction in the rock repeated cycles of expansion contraction led to the initiation and propagation of fractures within the network we propose that the observed fracture patterns are not a product of extrinsic conditions but rather a product of interactions between fractures implying that the polygonal fracture networks are self organizing systems

quasi zonal jets in 3 d argo data of the northeast atlantic 1 time mean zonal velocities estimated from argo float trajectories and density profiles are systematically examined for quasi zonal jets or striations with the use of a simple search algorithm a comparison to altimeter data combined with an independent estimate of the mean dynamic topography shows that the jets in the 2004 2006 period examined are persistent and stationary the jets have a typical meridional width of 100 to 200 km and a median transport of 4 sverdrups the jets tilt at approximately 6 from southwest to northeast in the horizontal plane but show no significant tilt in the vertical plane velocities and the cross stream width are similar for the westward and eastward jets

role of eddy forcing in the dynamics of multiple zonal jets in a model of the north atlantic multiple zonal jets are observed in satellite data based estimates of oceanic velocities float measurements and high resolution numerical simulations of the ocean circulation this study makes a step toward understanding the dynamics of these jets in the real ocean by analyzing the vertical structure and dynamical balances within multiple zonal jets simulated in an eddy resolving primitive equation model of the north atlantic in particular the authors focus on the role of eddy flux convergences eddy forcing in supporting the buoyancy and relative potential vorticity pv anomalies associated with the jets the results suggest a central role of baroclinic eddies in the barotropic and baroclinic dynamics of the jets and significant differences in the effects of eddy forcing between the subtropical and subpolar gyres additionally diabatic potential vorticity sources and sinks associated with vertical diffusion are shown to play an important role in supporting the potential vorticity anomalies the resulting potential vorticity profile does not resemble a pv staircase a distinct meridional structure observed in some idealized studies of geostrophic turbulence

generation of the north equatorial undercurrent jets by triad baroclinic rossby wave interactions abstractformation processes responsible for the north equatorial undercurrent neuc jets that appear across the tropical north pacific ocean near 9 13 and 18 n are explored both theoretically and using numerical models with different complexities analyses of an eddy resolving global ocean general circulation model output reveal that the neuc jets have a mode 1 baroclinic vertical structure and are spatially persistent on the interannual and longer time scales this ogcm simulated vertical structure prompts the authors to adopt the simpler nonlinear layer reduced gravity model as well as the baroclinic rossby wave triad interaction theory to unravel the essential processes underlying the neuc jets the seed for the neuc jets originates in annual baroclinic rossby waves driven by the large scale surface wind stress forcing emanating from the ocean basin s eastern boundary these wind forced primary waves are subject to nonlinear triad interactions and break down offshore where the e folding tim

dynamics of a quasi stationary jet along the subarctic front in the north pacific ocean the western isoguchi jet an ideal two layer model abstractthe dynamics of a quasi stationary jet along the subarctic front in the north pacific ocean the western isoguchi jet were investigated using an idealized two layer model the experiments suggested that a seafloor topography which is 500 m high produces a jet along its eastern flank the formation mechanism of the jet can be explained via baroclinic rossby wave characteristics baroclinic rossby waves propagate along characteristic curves which are significantly distorted by anticyclonic barotropic flow on the seafloor topography a baroclinic surface jet is formed where a characteristic curve originating in the subtropical gyre and one originating in the subpolar gyre meet because the pycnocline depth varies discontinuously at this location the barotropic flow on the seafloor topography is induced by eddies

far reaching effects of the hawaiian islands on the pacific ocean atmosphere system using satellite data we detected a wind wake trailing westward behind the hawaiian islands for 3000 kilometers a length many times greater than observed anywhere else on earth this wind wake drives an eastward ocean current that draws warm water from the asian coast 8000 kilometers away leaving marked changes in surface and subsurface ocean temperature standing in the path of the steady trade winds hawaii triggers an air sea interaction that provides the feedback to sustain the influence of these small islands over a long stretch of the pacific ocean

changes in the ventilation of the oxygen minimum zone of the tropical north atlantic changes in the ventilation of the oxygen minimum zone omz of the tropical north atlantic are studied using oceanographic data from 18 research cruises carried out between 28 5 and 23 w during 1999 2008 as well as historical data referring to the period 1972 85 in the core of the omz at about 400 m depth a highly significant oxygen decrease of about 15 mol kg 1 is found between the two periods during the same time interval the salinity at the oxygen minimum increased by about 0 1 above the core of the omz within the central water layer oxygen decreased too but salinity changed only slightly or even decreased the scatter in the local oxygen salinity relations decreased from the earlier to the later period suggesting a reduced filamentation due to mesoscale eddies and or zonal jets acting on the background gradients here it is suggested that latitudinally alternating zonal jets with observed amplitudes of a few centimeters per second in the depth range of the omz contribute to the ventilation of the omz a conceptual model of the ventilation of the omz is used to corroborate the hypothesis that changes in the strength of zonal jets affect mean oxygen levels in the omz according to the model a weakening of zonal jets which is in general agreement with observed hydrographic evidences is associated with a reduction of the mean oxygen levels that could significantly contribute to the observed deoxygenation of the north atlantic omz

multivariate fracture intensity prediction application to oil mountain anticline wyoming the geometric characteristics of natural fractures significantly impact the hydraulic behavior of fractured reservoirs prediction of fracture geometry is therefore important for reservoir development decisions and production forecasting although many geometric kinematic mechanical geomechanical petrophysical sedimentary and geophysical attributes correlate to fracture intensity typically only the attribute with the highest absolute value correlation is chosen to be carried forward to influence prediction we employ a geostatistical bayesian updating approach that quantitatively accounts for multiple important attributes together impacting fracture geometry prediction the resulting models are more representative of the true geological complexity this methodology is applied to the oil mountain anticline outcrop near casper wyoming

physical and chemical controls on the composition of waters in sedimentary basins abstract the composition of subsurface waters is determined not only by diagenetic reactions but also by physical processes of fluid convection and hydrodynamic dispersion the south west louisiana gulf coast provides an instructive field example of the net effects of diagenetic reaction and solute transport on pore water compositions in a regional siliciclastic sequence most formation waters here have compositions totally unlike the compositions of the connate meteoric and marine fluids that were buried with their host sediments at the time of deposition dissolved chloride has been generated by the subsurface dissolution of salt domes and has been pervasively transported by fluid flow throughout most of the upper 3 km of the sedimentary section the simultaneous systematic variation in dissolved na k mg ca and alkalinity with chloride in these waters supports the hypothesis that metastable thermodynamic buffering by silicate carbonate mineral assemblages is a first order control on fluid compositions the chemical potential of chloride or alternatively total anionic charge appears to be a master variable which ranks in importance with such other variables as pressure and temperature in driving diagenesis in this region this variable is controlled largely by physical processes of advection and dispersion in the upper 3 km of the section and by dehydration reactions in deeper mudstone dominated sediments where the composition of the fluid is largely rock buffered the ultimate origin of the fluid and its pathway of chemical evolution may be obscured at least in terms of major solute composition non buffered components such as cl and br or isotopic compositions are more likely to retain information on original end member fluid compositions and reaction pathways

volumetric curvature attributes add value to 3d seismic data interpretation horizon based curvature attributes have been used in seismic data interpretation for predicting fractures since 1994 when lisle demonstrated the correlation of curvature values to fractures measured on an outcrop different measures of curvature such as gaussian strike and dip have been shown by different workers to be highly correlated with fractures and many more applications are also possible by definition all such applications need the interpretation of a seismic horizon which may be simple if data quality is good and the horizon of interest corresponds to a prominent impedance contrast

origin of brine in the kangan gasfield isotopic and hydrogeochemical approaches the kangan permo triassic brine aquifer and the overlying gas reservoir in the southern iran are located in kangan and dalan formations consisting dominantly of limestone dolomite and to a lesser extent shale and anhydrite the gasfield 2 900 m in depth and is exploited by 36 wells some of which produce high salinity water the produced water gradually changed from fresh to saline causing severe corrosion in the pipelines and well head facilities the present research aims to identify the origin of this saline water brine as a vital step to manage saline water issues the major and minor ions as well as 2h 18o and 37cl isotopes were measured in the kangan aquifer water and or the saline produced waters the potential processes causing salinity can be halite dissolution membrane filtration and evaporation of water the potential sources of water may be meteoric present or paleo seawater the na cl and i cl ratios versus cl concentration preclude halite dissolution concentrations of cl na and total dissolved solid were compared with br concentration indicating that the evaporated ancient seawater trapped in the structure is the cause of salinization 18o isotope enrichment in the kangan aquifer water is due to both seawater evaporation and interaction with carbonate rocks the 37cl isotope content also supports the idea of evaporated ancient seawater as the origin of salinity membrane filtration is rejected as a possible source of salinity based on the hydrochemistry data the 18o value and incapability of this process to dramatically enhance salinity up to the observed value of 330 000 mg l the overlaying impermeable formations high pressure in the gas reservoir and the presence of a cap rock above the kangan gasfield all prevent the downward flow of meteoric and persian gulf waters into the kangan aquifer the evaporated ancient seawater is autochthonous because the kangan brine aquifer was formed by entrapment of brine seawater during the deposition of carbonates gypsum and minor clastic rocks in a lagoon and sabkha environment the reliability of determining the source of salinity in a deep complicated inaccessible high pressure aquifer can be improved by combining various methods of hydrochemistry isotope hydrodynamics hydrogeology and geological settings

quasi stationary north equatorial undercurrent jets across the tropical north pacific ocean 1 subthermocline circulation in the tropical north pacific ocean 2 n 30 n is investigated using profiling float temperature salinity data from the international argo and the origins of the kuroshio and mindanao current okmc projects three well defined eastward jets are detected beneath the wind driven westward flowing north equatorial current dubbed the north equatorial undercurrent neuc jets these subthermocline jets have a typical core velocity of 2 5 cms 1 and are spatially coherent from the western boundary to about 120 w across the north pacific basin centered around 9 n 13 n and 18 n in the western basin the neuc jet cores tend to migrate northward by 4 in the eastern basin vertically the cores of the southern central and northern neuc jets reside on the 26 9 27 2 and 27 3 surfaces respectively and they tend to shoal to lighter density surfaces by about 0 2 as the jets progress eastward

intermediate zonal jets in the tropical pacific ocean observed by argo floats abstractargo float data in the tropical pacific ocean during january 2003 august 2011 are analyzed to obtain lagrangian subsurface velocities at their parking depths maps of mean zonal velocities at 1000 and 1500 m are presented at both depths a series of alternating westward and eastward zonal jets with a meridional scale of 1 5 is seen at the basin scale from 10 s to 10 n these alternating jets with mean speeds about 5 cm s 1 are clearly present in the western and central parts of the basin but weaken and disappear approaching the eastern coast they are stronger in the southern hemisphere along the equator at both 1000 and 1500 m a westward jet is seen the jets closer to the equator are remarkably zonally coherent across the basin but the jets farther poleward appear broken in several segments in the western half of the basin the 1000 m zonal jets appear to slant slightly poleward from east to west at the western boundary in the south east of solomon islands and papua new guinea the al

upper proterozoic evaporites in the amadeus basin central australia and their role in basin tectonics the amadeus basin an isolated intracratonic basin in the center of the australian continent contains an upper proterozoic to mid paleozoic stratigraphic succession of shallow marine sediments that in places exceeds 14 km in thickness the gillen member of the bitter springs formation which occur toward the base of the upper proterozoic succession includes evaporites which are among the world9s earliest 0 8 to 0 7 ga because of their age the evaporites have been cited in discussions of sea water chemistry and have been the focus of scrutiny for early life forms in spite of their importance the evaporites are poorly known particularly from the viewpoint of their depositional and tectonic setting in an attempt to rectify this deficiency more than 6 000 km of seismic data were analyzed in conjunction with a field and well log study of the unit the late proterozoic amadeus basin appears to have consisted of two major poorly circulated anoxic sub basins which perhaps opened to the ocean to the southeast through the adelaide geosyncline data relating to facies are limited but suggest that deposition of the evaporites was cyclic and followed the patterns identified in other major evaporite basins the carbonates and sulfates being closer to the basin margins and later stage halite and possibly potassium salts being toward the basin center the evaporites were deposited in a shallow marine setting at the time of a relative sea level high stand the apparent sea level high may relate to basin dynamics whereas the cyclicity of the evaporites may be due to eustatic sea level controls acting on the barrier to allow intermittent inflow of sea water salt tectonism began shortly after the evaporites were deposited and continued throughout basin development consequently most of the major anticlinal structures have salt cores the geometry of the salt structures suggests that during their growth the mean strain rate was 10 16 s 1 a rate typical of large salt structures growth on these salt structures has played an important role in controlling later sedimentation particularly during the cambrian

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

the degree of anisotropy for mid ocean currents from satellite observations and an eddy permitting model simulation 1 the degree of anisotropy is calculated for the mid ocean currents estimated from satellite altimetry and simulated with a numerical model of the pacific ocean a high resolution eddy permitting model is used for its ability to simulate mid ocean multiple zonal flows crucial for the evaluation of the degree of anisotropy using a commonly defined parameter of anisotropy that falls between 1 and 1 and equals 0 1 and 1 for an isotropic purely meridional and purely zonal flow respectively it is found that increases from nearly zero for weekly data to significantly positive values for seasonally and annually averaged data this tendency of increasing zonal anisotropy with averaging time is true for the surface geostrophic velocity from satellite altimetry and for both surface and deep ocean velocities from the model simulation the absolute value of for the simulated surface currents agree with that derived from satellite observation reaffirming the reliability of both data sets in the model simulation the behavior of at the surface is very similar to that at 1000 m indicating a deep structure of the zonally elongated features in the middle of the pacific ocean the implications of these findings are discussed in the context of oceanic eddies rossby waves and zonal jets

upper and intermediate circulation in the western equatorial pacific ocean in october 1999 and april 2000 1 the upper and intermediate circulation 0 1200 m in the western equatorial pacific ocean is examined thanks to lowered acoustic doppler current profiler ladcp measurements carried out during two cruises in october 1999 and april 2000 several new features of the equatorial circulation are discussed it is shown that the secondary south subsurface countercurrent ssscc laying at 6 s 400 m depth had a deep extension at 165 e with a maximum core velocity around 5 s 1000 m furthermore the equatorial intermediate current eic and the lower eic leic displayed a strong temporal variability between 165 e and 180 as these two westward currents were replaced by eastward flow along the equator on the second cruise finally during the april 2000 cruise the zonal velocity profile carried out at the equator east of the gilbert island around 175 e broke into small vertical scales possibly reflecting topographic effect and or destabilization mechanism that leads to the formation of long zonal jet like structures

zonal jets as transport barriers in planetary atmospheres abstract the connection between transport barriers and potential vorticity pv barriers in pv conserving flows is investigated with a focus on zonal jets in planetary atmospheres a perturbed pv staircase model is used to illustrate important concepts this flow consists of a sequence of narrow eastward and broad westward zonal jets with a staircase pv structure the pv steps are at the latitudes of the cores of the eastward jets numerically simulated solutions to the quasigeostrophic pv conservation equation in a perturbed pv staircase flow are presented these simulations reveal that both eastward and westward zonal jets serve as robust meridional transport barriers the surprise is that westward jets across which the background pv gradient vanishes serve as robust transport barriers a theoretical explanation of the underlying barrier mechanism is provided it is argued that transport barriers near the cores of westward zonal jets across which the background pv gradient is small are found in jupi

middepth equatorial tracer tongues in a model of the atlantic ocean 1 observational estimates of middepth tracer tongues in the equatorial atlantic are reviewed and are compared with results from several eddy resolving model simulations local maxima of chlorofluorocarbon cfc concentrations along the equator at around 1500 m depth are related to mean eastward jet structures in the models at similar depth ranges and can also be identified in several simulated tracer distributions similar to the observations strong eastward jets are located in the simulations 1 2 north and south of the equator the model simulations show in addition consistent with the cfc observations weaker jets at around 4 6 n s and 8 10 n s suggestive of a large scale alternating eastward westward current system in the western tropical atlantic in this depth range lagrangian transport estimates in the model using float diagnostics show a transport of 1 3 sv in each of the eastward jets 1 2 n s off the equator compared to 3 12 sv throughflow into the south atlantic with no seasonal cycle apparent in the transport fractioning comparing different model solutions reveals the choice of the subgrid scale mixing parameterization as important for the amplitudes of the jets enhanced reduced diapycnal mixing is related to stronger weaker jets

multiple zonal jets in a quasigeostrophic model of the antarctic circumpolar current abstract the presence of multiple zonal fronts in the antarctic circumpolar current acc a phenomenon described as zonation has been confirmed by many observations suggesting that the fronts are circumpolar in extent in the context of quasigeostrophic turbulence models panetta has shown that fronts associated with long lived zonal jets develop spontaneously in very wide baroclinically unstable regions of width large compared with the rossby radius of deformation the present paper examines the relevance of this mechanism to the zonation of the acc using a quasigeostrophic wind forced channel model multiple jets appear when the forcing scale is wide enough and they have horizontal scales and a strength that compares well with observations however in the presence of large scale random topography a different dynamical regime emerges in which the flow structure depends on the topographically controlled stationary eddies

stress evolution during 3d single layer visco elastic buckle folding implications for the initiation of fractures abstract buckle folds of sedimentary strata commonly feature a variety of different fracture sets some fracture sets including outer arc tensile fractures and inner arc shear fractures at the fold hinge zones are well understood by the extensional and compressional strain stress pattern however other commonly observed fracture sets including tensile fractures parallel to the fold axis tensile fractures cutting through the limb extensional faults at the fold hinge and other shear fractures of various orientations in the fold limb fail to be intuitively explained by the strain stress regimes during the buckling process to obtain a better understanding of the conditions for the initiation of the various fractures sets associated with single layer cylindrical buckle folds a 3d finite element modeling approach using a maxwell visco elastic rheology is utilized the influences of three model parameters with significant influence on fracture initiation are considered burial depth viscosity and permeability it is concluded that these parameters are critical for the initiation of major fracture sets at the hinge zone with varying degrees the numerical simulation results further show that the buckling process fails to explain most of the fracture sets occurring in the limb unless the process of erosional unloading as a post fold phenomenon is considered for fracture sets that only develop under unrealistic boundary conditions the results demonstrate that their development is realistic for a perclinal fold geometry in summary a more thorough understanding of fractures sets associated with buckle folds is obtained based on the simulation of in situ stress conditions during the structural development of buckle folds

origin of salinity in produced waters from the palm valley gas field northern territory australia abstract the chemical composition and evolution of produced waters associated with gas production in the palm valley gas field northern territory has important implications for issues such as gas reserve calculations reservoir management and saline water disposal the occurrence of saline formation water in the palm valley field has been the subject of considerable debate there were no occurrences of mobile water early in the development of the field and only after gas production had reduced the reservoir pressure was saline formation water produced initially this was in small quantities but has increased dramatically with time particularly after the initiation of compression in november 1996 the produced waters range from highly saline up to 300 000 mg l tds with unusual enrichments in ca ba and sr to low salinity fluids that may represent condensate waters the sr isotopic compositions of the waters 87sr 86sr 0 7041 0 7172 are also variable but do not correlate closely with major and trace element abundances although the extreme salinity suggests possible involvement of evaporite deposits lower in the stratigraphic sequence the sr isotopic composition of the high salinity waters suggests a more complex evolutionary history the formation waters are chemically and isotopically heterogeneous and are not well mixed the high salinity brines have sr isotopic compositions and other geochemical characteristics more consistent with long term residence within the reservoir rocks than with present day derivation from a more distal pool of brines associated with evaporites if the high salinity brines entered the reservoir during the devonian uplift and were displaced by the reservoir gas into a stagnant pool which has remained near the reservoir for the last 300 400 ma then the size of the brine pool is limited at a minimum it might be equivalent to the volume displaced by the reservoired gas

modelling approaches to understanding fold development implications for hydrocarbon reservoirs a mechanics based approach to the evolution of buckle folds is proposed existing analytic and simple numerical models are used to demonstrate that dramatic changes in layer parallel stress occur in developing folds and that the bulk effective rheology of folding rocks is strongly reduced in relation to neighbouring rocks with no folds a methodology for estimating regions of folds more or less likely to suffer fracture is set out in this methodology a simple abstraction of the natural fold is identified and the stress history during its development is calculated using linear viscosity as a proxy for competence this simple and computationally cheap approach allows all salient features of natural multilayer folds to be recreated in numerical experiments the final step in the method is to use the stress conditions for three types of fracture failure tensile failure dilatant shear failure and grain crushing to define potential functions that indicate increased or decreased probability of failure results give predictions that agree well with observation in the simple cases studied a novel method for approximating three dimensional deformations is used to model the propagation of folds in the axial direction and it is found that this occurs rapidly and allows constructive and destructive interference of propagating folds below a certain amplitude this provides a means by which perturbations may interact over a certain distance such a mechanism was an implicit requisite of classic fold theories but its identity has been obscure for three decades it is shown that many small perturbations are needed to give patches of coherent folds and that few large perturbations give single arc folds

tropical atlantic air sea interaction and its influence on the nao an atmospheric general circulation model agcm is forced with a prescribed sst dipole anomaly in the tropical atlantic to investigate the cause of cross equatorial sst gradient cesg variability and its teleconnection to the extratropics the model response bears a striking resemblance to observations in both the tropics and extratropics the tropical response is robust and can act to reinforce the prescribed sst anomalies through wind induced evaporation a new feedback mechanism involving low level stratiform clouds in the subtropics is also identified in the model and observations the tropical sst dipole forces a barotropic teleconnection into the extratropics that projects onto the north atlantic oscillation nao it further induces the extratropical portion of the north atlantic sst tripole when the agcm is coupled with an ocean mixed layer model cesg variability thus appears to be the centerpiece of a pan atlantic climate pattern observed to extend from the south atlantic to greenland

study of fracture induced anisotropy from discrete fracture network simulation of well test responses different conceptualizations of fracture networks have been generated in order to simulate well tests in fractured reservoirs these models have two purposes firstly to investigate whether the behaviour of realistic fracture networks can be emulated with more simple models and secondly to assess whether different sources of anisotropy have characteristic and recognizable influences on the pressure derivative the anisotropy of the fracture networks was increased by decreasing the angle between two originally orthogonal fracture sets and by increasing the permeability contrast between two orthogonal fracture sets results indicate that simple models can capture the first order behaviour of more realistic examples however because early time data are strongly influenced by the connectivity of the fracture network the degree of anisotropy can only be assessed at later times in a test increasing anisotropy results in increasing heterogeneity and compartmentalization and permeability anisotropy in an orthogonal system can only partially replicate the behaviour of a geometrically anisotropic system

the impact of advective transport by the south indian ocean countercurrent on the madagascar plankton bloom 1 based on ten years 1998 2007 of satellite ocean color data we analyze the spatiotemporal patterns in the seasonal madagascar plankton bloom with respect to the advection of the recently discovered southern indian ocean countercurrent sicc in maps of finite time lyapunov exponents ftle and finite time zonal drift ftzd computed from altimetry derived velocities we observe a narrow zonal jet that starts at 25 s at the southern tip of madagascar an important upwelling region and extends to the east further than the largest plankton blooms 2500 km in bloom years the jet coincides with large parts of the northern boundary of the plankton bloom acting as a barrier to meridional transport our findings suggest that advection is an important and so far underestimated mechanism for the eastward propagation and the extent of the plankton bloom this supports the hypothesis of a single nutrient source south of madagascar

observational evidence of alternating zonal jets in the world ocean 1 multiple zonal jets with the east west velocity direction alternating with latitude are discovered in satellite altimetry data the time varying jets are shown to populate every part of the world ocean and its marginal seas and are best seen in the anomaly of geostrophic vorticity at midlatitudes the jets have a meridional wavelength of about 300 kms with r m s sea level velocity and vorticity values of 2 4 cm 6 9 cm s and 1 5 10 6 s 1 correspondingly realistic data from the high resolution ogcm run on the earth simulator are used to justify high vertical coherence of the jets structure and relevance of the jets to an evolving mesoscale eddy field strong coupling between the jets and mesoscale eddies is hypothesized

anisotropic material transport by eddies and eddy driven currents in a model of the north atlantic this study analyzes anisotropic properties of the material transport by eddies and eddy driven zonal jets in a general circulation model of the north atlantic through the analysis of lagrangian particle trajectories spreading rates defined here as half the rate of change in the particle dispersion in the zonal direction systematically exceed the meridional rates by an order of magnitude area averaged values for the upperocean zonal and meridional spreading rates are approximately 8100 and 1400 m 2 s 21 respectively and in the deep ocean they are 2400 and 200 m 2 s 21 the results demonstrate that this anisotropy is mainly due to the actionofthetransienteddiesandnotto thesheardispersionassociated withthetime meanjets thisproperty is consistent with the fact that eddies in this study have zonally elongated shapes with the exception of the upper ocean subpolar gyre eddies also cause the superdiffusive zonal spreading significant variations in the spreading rate in the vertical and meridional directions and the difference between the westward and eastward spreading

near coastal circulation in the northern humboldt current system from shipboard adcp data the near coastal circulation of the northern humboldt current system is described analyzing 8700 velocity profiles acquired by a shipboard acoustic doppler current profiler sadcp during 21 surveys realized between 2008 and 2012 along the peruvian coast this data set permits observation of i part of the peru coastal current and the peru oceanic current that flow equatorward in near surface layers close to the coast and farther than 150 km from the coast respectively ii the peru chile undercurrent pcuc flowing poleward in subsurface layers along the outer continental shelf and inner slope iii the near surfacing equatorial undercurrent renamed as ecuador peru coastal current that feeds the pcuc and iv a deep equatorward current referred to as the chile peru deep coastal current flowing below the pcuc a focus in the pcuc core layer shows that this current exhibits typical velocities of 5 10 cm s 1 the pcuc deepens with an increasing thickness poleward consistent with the alongshore conservation of potential vorticity the pcuc mass transport increases from 1 8 sv at 5 s to a maximum value of 5 2 sv at 15 s partly explained by the sverdrup balance the pcuc experiences relatively weak seasonal variability and the confluence of eddy like structures and coastal currents strongly complicates the circulation the pcuc intensity is also affected by the southward propagation of coastally trapped waves as revealed by a strong pcuc intensification in march 2010 coincident with the passage of a downwelling coastal wave associated with a weak el nino event

zonal jets in the pacific ocean 1 the spatial and temporal properties of zonally coherent jet like structures found in high resolution ocean models is examined we focus on the pacific ocean we find the properties of the jets are not very sensitive to the model configuration distinct differences are found in the persistence and vertical structure of the jets poleward of 30 n and s compared with those in the tropics we make a quantitative comparison between the meridional scale of the jets and the rhines scale we find a local scaling applies in that the horizontal variation of the meridional scale of the jets is consistent with horizontal variations in the rhines scale

stationary mesoscale jet like features in the ocean 1 xbt and float data of the world ocean database 2005 are used to validate new stationary jet like features striations recently found in the high resolution mean dynamic ocean topography mdot two study areas were selected in the eastern parts of the north and south pacific subtropical gyres free of any strong currents appropriate horizontal high pass filtering applied to the ensemble mean temperature at 100 m depth revealed the striation signal coherent with mdot the features are also distinct in the data of depth of 12 c isotherm lying close to the thermocline the striations are oriented nearly zonally and coherent vertically at least through 700 m depth their wavelength is approximately 400 km and the azimuth of wavevector is 13 9 in the northern southern domains correspondence between the striations in observations and ofes ogcm for the earth simulator model as well as the nature of the striations are discussed

arterial ocean circulation of the southeast indian ocean 1 the time mean ocean circulation for the southeast indian ocean seio is analyzed using a colorwheel to reveal an arterial like structure although quasi zonal the mean circulation in this region is distinctly more complex than previously presented in recent literature the mean flow is derived from an eddy resolving ocean reanalysis of the past 14 years the ocean state is constrained through data assimilation with observed sea level anomaly sea surface temperature and in situ profiles geostrophic currents derived from the reanalyzed mean dynamic topography mdt are validated against two other mdt analyses to show a comparable arterial structure and distribution of scales in particular the broad scale eastward flow is regularly interspersed by narrow bands of the near westward flow meridional sections from the ocean reanalysis reveal a net eastward transport in the surface layer and a net westward flow at mid depth the seasonality of the surface layer flow in the seio appears to have increased decreased eastward mean transport that coincide with seasons of stronger weaker leeuwin current lc whether the narrow bands of mean current and mass flux are simply the average of the eddies or represent an underlying weak jet remains a topic of current debate

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

interpretation of the propagation of surface altimetric observations in terms of planetary waves and geostrophic turbulence 1 the interpretation of surface altimetric signals in terms of rossby waves is revisited rather than make the long wave approximation the horizontal scale of the waves is adjusted to optimally fit the phase speed predicted by linear theory to that observed by altimetry assuming a first baroclinic mode vertical structure it is found that in the tropical band the observations can be fit if the wavelength of the waves is assumed to be large of order 600 km or so however poleward of 30 it is more difficult to fit linear theory to the observations and the fit is less good than at lower latitudes the required scale of the waves must be reduced to about 100 km somewhat larger than the local deformation wavelength it is argued that these results can be interpreted in terms of rossby wave baroclinic instability and turbulence theory at low latitudes there is an overlap between geostrophic turbulence and rossby wave timescales and so an upscale energy transfer from baroclinic instability at the deformation scale produces waves at high latitudes there is no such overlap and waves are not produced by upscale energy transfer these ideas are tested by using surface drifter data to infer turbulent velocities and timescales that are compared to those of linear rossby waves a transition from a field dominated by waves to one dominated by turbulence occurs at about 30 broadly consistent with the transition that is required to fit linear theory to altimetric observations

geochemical tracing and hydrogeochemical modelling of water rock interactions during salinization of alluvial groundwater upper rhine valley france in the southern upper rhine valley groundwater has undergone intensive saline pollution caused by the infiltration of mining brines a consequence of potash extraction carried out during the 20th century major and trace elements along with sr and u isotopic ratios show that groundwater geochemical characteristics along the saline plumes cannot reflect conservative mixing between saline waters resulting from the dissolution of waste heaps and one or more unpolluted end members the results imply the occurrence of interactions between host rocks and polluted waters and they suggest that cationic exchange mechanisms are the primary controlling process a coupled hydrogeochemical model has been developed with the numerical code kirmat which demonstrates that cationic exchange between alkalis from polluted waters and alkaline earth elements from montmorillonite present in the host rock of the aquifer is the primary process controlling the geochemical evolution of the groundwater the model requires only a small amount of montmorillonite between 0 75 and 2 25 which is in agreement with the observed mineralogical composition of the aquifer the model also proves that a small contribution of calcite precipitation dissolution takes places whereas other secondary mineral precipitation or host rock mineral dissolution do not play a significant role in the geochemical signature of the studied groundwater samples application of the model demonstrates that it is necessary to consider the pollution history to explain the important cl na and ca concentration modifications in groundwater samples taken over 2 km downstream of waste heaps additionally the model shows that the rapidity of the cationic exchange reactions insures a reversibility of the cation fixation on clays in the aquifer

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

the ocean general circulation near 1000 m depth abstractthe mean ocean circulation near 1000 m depth is estimated with 100 km resolution from the argo float displacements collected before 1 january 2010 after a thorough validation the 400 000 or so displacements found in the 950 1150 dbar layer and with parking times between 4 and 17 days allow the currents to be mapped at intermediate depths with unprecedented details the antarctic circumpolar current acc is the most prominent feature but western boundary currents and their recirculations and alternating zonal jets in the tropical atlantic and pacific are also well defined eddy kinetic energy eke gives the mesoscale variability on the order of 10 cm2 s 2 in the interior which is compared to the surface geostrophic altimetric eke showing e folding depths greater than 700 m in the acc and northern subpolar regions assuming planetary geostrophy the geopotential height of the 1000 dbar isobar is estimated to obtain an absolute and deep reference level worldwide this is done by solving num

long extratropical planetary wave propagation in the presence of slowly varying mean flow and bottom topography part ii ray propagation and comparison with observations ray theory is used to predict phase and group velocities for long planetary waves under realistic albeit slowly varying oceanic conditions the results are compared with local theory using fields smoothed to the same amount 9 latitude longitude as well as those with much less smoothing 1 the agreement is excellent showing that local theory forms a good proxy for ray theory results the predicted speeds agree well with observations of planetary waves deduced from sea surface height data the theory uses purely baroclinic mean flow the inclusion of barotropic flow has little effect except at high latitudes

aerial observations of hawaii s wake abstract under the influence of the east northeasterly trade winds the island of hawaii generates a wake that extends about 200 km to the west southwest during the harp project in july and august 1990 five wake surveys were carried out by the ncar electra the patterns of wind and aerosol concentration revealed by these flights suggest that hawaii s wake consists of two large quasi steady counterrotating eddies the southern clockwise rotating eddy carries a heavy aerosol load due to input from the k volcano at the eastern end of the wake the eddies are potentially warmer and more humid than the surrounding trade wind air several other features are discussed sharp shear lines near the northern and southern tips of the island dry and warm air bands along the shear lines a small embedded wake behind the kohala peninsula wake centerline clouds hydraulic jumps to the north and south of the island a descending inversion connected with accelerating trade winds and evidence for side to side wake mo

effects of eddies on an ocean observing system with profiling floats idealized simulations of the argo array 1 this study aims at evaluating effects of the mesoscale variability on the expected accuracy of reconstruction of temperature salinity and velocities from the argo measurements and trajectories for this purpose an idealized observing system with profiling floats is simulated in a high resolution ocean model of the north atlantic set up to produce annual mean hydrography and circulation the simulations with and without mesoscale variability are compared and the effects of the time mean and mesoscale eddy induced advection are effectively separated and investigated the results demonstrate several effects of mesoscale eddies on the expected accuracy of the argo based reconstructions of temperature salinity and horizontal velocities in most of the domain the eddies help to achieve uniform spatial coverage the effects of eddy advection on reconstruction errors are however complex but moderate in most of the domain high frequency variability in temperature and salinity leads to enhancement of reconstruction errors especially if the sampling is carried out for only a few years the reconstruction of horizontal velocities from trajectories of the profiling floats is capable of detecting multiple zonal jets which have been observed already the reconstruction of the meridional velocities is significantly less reliable primarily due to a small signal to noise ratio in the in the interior of domain

large scale mechanical buckle fold development and the initiation of tensile fractures tensile failure associated with buckle folding is commonly associated to the distribution of outer arc extension but has also been observed on fold limbs this study investigates whether tensile stresses and associated failure can be explained by the process of buckling under realistic in situ stress conditions a 2 d plane strain finite element modeling approach is used to study single layer buckle folds with a maxwell viscoelastic rheology a variety of material parameters are considered and their influence on the initiation of tensile stresses during the various stages of deformation is analyzed it is concluded that the buckling process determines the strain distribution within the fold layer but is not solely responsible for the initiation of tensile stresses the modeling results show that tensile stresses are most dependent on the permeability viscosity and overburden thickness low permeability 10 19 m2 high viscosity 1021 pa s and low overburden pressure can explain tensile failure at the fold hinge tensile stresses in the limb of the fold cannot in general be explained by buckling rather it develops due to a combination of compression and erosional unloading the modeling results show that erosion of high permeability rocks can explain the generation of tensile stresses at significant depths 2 km both at the hinge of the fold and throughout the limb of the fold this study shows that tensile stresses and associated failure within buckle folds is directly dependent on the distribution of material parameters but moreover to the strain history of the geologic system

equatorward energy cascade critical latitude and the predominance of cyclonic vortices in geostrophic turbulence geostrophic turbulence exhibits features similar to those observed in the oceans a movement of energy toward the equator a critical latitude below which are alternating zonal flows and above which the flow is largely isotropic and a predominance of cyclonic vortices above the critical latitude these features arise in geostrophic turbulence when the latitude dependence of the deformation radius is taken into account with the aid of a quasigeostrophic one layer numerical model this paper proposes physical mechanisms giving rise to these features

basin scale evolution of formation waters a diagenetic and formation water study of the triassic chaunoy formation paris basin abstract formation waters and their movements within basins are commonly attributed with responsibility for patterns of cementation and porosity loss within reservoirs and aquifers it is thus important to understand when and how waters move in the subsurface we have studied the evolution and movement of formation water in the triassic chaunoy formation of the paris basin nw europe to define the way in which the water has evolved and to interpret water movement patterns using mineral isotope and fluid inclusion data in conjunction with detailed formation water analyses the chaunoy formation is cemented with different types of dolomite calcite and quartz cement we have studied the evolution of waters in terms of oxygen carbon and strontium isotopes and salinity connate waters were meteoric in origin but strongly influenced by the proximity of a playa lake input of palaeo meteoric water which entered the chaunoy via eastern halite bodies resulted in highly saline formation water for the majority of the chaunoy formation from about 100 ma until and for some time after maximum burial saline waters spread into the aquifer initially taking a west north west trajectory and then switching to a west south west pattern in the eocene following the alpine orogeny and localised uplift of the basin margin the southern portion of chaunoy received fresh low salinity meteoric water it is likely that formation water was lost from the chaunoy in a more central part of the basin via sub vertical cross formational flow to the mid jurassic dogger formation to accommodate the influx of fresh water

atmospheric manifestation of tropical instability wave observed by quikscat and tropical rain measuring mission observations from two new spaceborne microwave instruments in 1999 clearly reveal the atmospheric manifestation of tropical instability waves north of the pacific equatorial cold tongue a unique zonal temporal band pass filter enables the isolation of the propagating signals and the determination of their phase differences the phase differences between the propagation of wind and sea surface temperature sst signals observed from space and the vertical wind profiles measured from a research ship are consistent with the hypothesis that the coupling between wind and sst is caused by buoyancy instability and mixing which reduces the wind shear in the atmospheric boundary layer the coupling causes higher evaporative cooling over the warm phase and infers a negative thermal feedback

quantifying and interpreting striations in a subtropical gyre a spectral perspective abstractthe amplitude origin and direction of striations in the subtropical gyre are investigated using simulated and analytical multidimensional spectra striations defined as banded structures in the low frequency motions account for a noticeable percentage of zonal velocity variability in the east north pacific enp 25 42 n 150 130 w and central north pacific cnp 10 22 n 132 e 162 w regions in an eddying global ocean model thus they likely are nonnegligible in mixing and transport processes striations in the enp region are nonzonal and are embedded in the nonzonal gyre flow whereas striations in the cnp region are more zonal as are the mean gyre flows an idealized 1 5 layer model shows the gyre flow partially determines their directions which qualitatively resemble those in the global eddying model in the linear limit structures are quasi stationary frequency 0 linear rossby waves and the gyre flow influences the direction by influencing the nature of the zero rossby wave f

subtropical countercurrent in an idealized ocean gcm abstract in the north pacific there is a shallow eastward current called the subtropical countercurrent which flows across the central subtropical gyre the present article studies the generation mechanism of the subtropical countercurrent reproduced in an ocean general circulation model gcm with a simple geometry driven by surface wind stress and surface buoyancy forcing in the ocean gcm the deep mixed layer occurs in the northern part of subtropical gyre and shoals abruptly in the central subtropical gyre the mixed layer front the narrow transition zone of the mixed layer depth slants from the western central subtropical gyre to the northeast and the low potential vorticity fluid is formed at the intersection of the mixed layer front and the outcrop line since the surface density is almost zonally uniform and the mixed layer front slants northeastward the minimum potential vorticity fluids on denser isopycnals are formed in the northeastern region while those on lighter isopycnals are form

eddy trains and striations in quasigeostrophic simulations and the ocean abstractthis study explores the relationship between coherent eddies and zonally elongated striations the investigation involves an analysis of two baroclinic quasigeostrophic models of a zonal and double gyre flow and a set of altimetry sea level anomaly data in the north pacific striations are defined by either spatiotemporal filtering or empirical orthogonal functions eofs with both approaches leading to consistent results coherent eddies identified here by the modified okubo weiss parameter tend to propagate along well defined paths thus forming eddy trains that coincide with striations the striations and eddy trains tend to drift away from the intergyre boundary at the same speed in both the model and observations the eof analysis further confirms that these striations in model simulations and altimetry are not an artifact of temporal averaging of random spatially uncorrelated vortices this study suggests instead that eddies organize into eddy trains which manifest themselves as stria