enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

simulations of nearshore particle pair dispersion in southern california knowledge of horizontal relative dispersion in nearshore oceans is important for many applications including the transport and fate of pollutants and the dynamics of nearshore ecosystems two particle dispersion statistics are calculated from millions of synthetic particle trajectories from high resolution numerical simulations of the southern california bight the model horizontal resolution of 250m allows the investigation of the two particle dispersion with an initial pair separation of 500m the relative dispersion is characterized with respect to the coastal geometry bathymetry eddy kinetic energy and the relative magnitudes of strain and vorticity dispersion is dominated by the submesoscale not by tides in general headlands are more energetic and dispersive than bays relative diffusivity estimates are smaller and more anisotropic close to shore farther from shore the relative diffusivity increases and becomes less anisotropic approaching isotropy 10km from the coast the degree of anisotropy of the relative diffusivity is qualitativelyconsistentwiththat foreddy kinetic energy thetotal relative diffusivity asa functionof pairseparation distance r is on average proportional to r 5 4 additional lagrangian experiments at higher horizontal numerical resolution confirmed the robustness of these results structures of large vorticity are preferably elongated and aligned with the coastline nearshore which may limit cross shelf dispersion the results provide useful information for the design of subgrid scale mixing parameterizations as well as quantifying the transport and dispersal of dissolved pollutants and biological propagules

rhinegraben horizontal stylolites indicating stress regimes of earlier stages of rifting abstract buchner f 1981 rhinegraben horizontal stylolites indicating stress regimes of earlier stages of rifting in j h illies editor mechanism of graben formation tectonophysics 73 113 118 tectonic stylolites horizontal columns and their statistical distribution in middle triassic and jurassic limestones on both flanks of the rhinegraben are described and their relation to the rhinegraben taphrogenesis is discussed a generation of pre middle miocene nne striking horizontal stylolites and a subsequent generation of post lower miocene nw striking horizontal stylolites have been recognized the first generation stylolites indicates a horizontal compression in the nne ssw direction while the second generation indicates a compression in the nw se direction average maxima of joints parallel to the two horizontal stylolite maxima were found joints and their corresponding horizontal stylolites were formed under the same stress regime

the neotectonics of the tibetan plateau part of the continuing northward convergence between india and eurasia is probably taken up by strike slip displacement with tibet as a whole moving eastward away from the collision zone and undergoing east west extension molnar and tapponnier 1975 ni and york 1978 on the basis of our interpretation of landsat images we propose that strike slip faulting occurs throughout the tibetan plateau such that its north south cross section is being shortened with little contemporary folding or thrusting

relative dispersion of surface drifters in the benguela upwelling region abstractwe examine the relative dispersion of surface drifters deployed in groups of triplets at the boundaries of a filament in the upwelling region off namibia for both the entire ensemble and th

temporal variability of currents in the eastern ligurian sea surface and intermediate waters enter the ligurian sea from the tyrrhenian and algero provencal basins via northward flows along the east and west coasts of corsica the temporal variability of these flows is examined by means of a 1 year time series of current data october 1986 to september 1987 and hydrographic data from december march and may cruises the flow through the corsica channel increases suddenly during december and then gradually decreases after march reaching its lowest values in late summer the seasonal variability in the channel seems associated mainly with the steric sea level differences between the tyrrhenian sea and ligurian sea the west corsican current appears more stable throughout the one year of data the two flows converge just north of corsica into the ligurian current because of the water masses differences between the two currents in the area of convergence considerable smaller scaled structure is observed during winter the less dense tyrrhenian water provides available potential energy to the ligurian shelf area and thereby helps sustain the large scale cyclonic circulation in the ligurian basin during the other seasons the spatial structures over the ligurian shelf are less organized and the spatial scale of the flow is a few tens of kilometers

aspects of the antarctic circumpolar current dynamics investigated with drifter data interactions between eddies and mean flow are essential to close the momentum budget of the southern ocean as well as to determine the structure of the global meridional overturning circulation both the structure of the antarctic circumpolar current and the eddy dynamics arising at its heart are importantfor water mass circulation and global ocean ventilation and therefore for the global climate however the characterization of the eddy fields of heat and momentum are still poorly sampled by direct observations and are difficult to accurately resolve or parameterize in numerical models here we present observation based eddy statistics and eddy heat flux ehf from a consistent dataset and estimate southern ocean surface ehf from direct measurements without any parameterization assumption observations obtained from near surface drifters represent a very useful dataset to analyze the eddy field because of their ability to catch a large number of scales of motion while providing a quasi synoptic coverage of the investigated area differences between winter and summer distributions of mean velocities mean kinetic energy and eddy kinetic energy are shown to be strongly constrained by bottom topography and suggest a winter shift of the polar front in specific areas around the circumpolar belt overall the flow follows the contours of constant planetary vorticity set by the depth of the ocean and creates anisotropy in eddy dispersion with maximum dispersion along these contours furthermore eddy mean flow interactions are strongly influenced by topography with eddies having a tendency to accelerate jets upstream of ridges and decelerate them further downstream these strong regional variabilities introduced by topography affect the flux of heat induced by eddies and therefore affect formation and subduction of the main surface and intermediate southern ocean water masses integrated over the southern ocean subduction of water masses induced by ehf appears as an order on component for the southern ocean thermocline ventilation our results based on direct observations emphasizes once more the importance of continuing sustained effort to better represent the effect of mesoscale eddies in a coarse climate model if we are to represent and predict future climate

a late cenozoic regional mesofracture system in southern england and northern france the upper cretaceous and palaeogene rocks of s england and n france are cut by a nw trending system of fractures characterized by swarms of vertical extension joints accompanied by conjugate sets of hybrid and shear joints and normal mesofaults many major photolineaments exhibit the same nw trend as the fractures and are particularly conspicuous in n france where they are coincident with rectilinear drainage channels suggesting a relationship between fracture orientation and physiography in s england this relationship is absent possibly because of the influence of additional fracture systems related to major flexures trending obliquely to the nw se direction these major e w trending flexures and associated fracture systems were formed during the oligocene to early miocene 9helvetic9 phase of deformation and are cross cut obliquely by fractures in the nw trending system the nw trending fractures and lineaments are parallel to neotectonic normal faults in the lower rhine embayment and become less well developed to the west with increasing distance from these major structures the lower rhine faults were reactivated and propagated into the quaternary cover as a consequence of ne sw regional tension generated during the late neogene to recent 9jura9 phase of nw se alpine convergence the nw trending extensional structures in s england and n france are considered to be of about the same age and related to the same stress regime as the neotectonic normal faults of the lower rhine embayment however because fractures of the nw system cutting palaeogene sediments in se england are truncated by the erosion surface beneath the plio pleistocene red crag deposits it is possible that in england fracture initiation did not continue into quaternary times

the sardinian cold water coral province in the context of the mediterranean coral ecosystems abstract a new cold water coral cwc province has been identified in the mediterranean sea in the capo spartivento canyon system offshore the southern coast of sardinia the sardinia cold water coral province is characterized in the nora canyon by a spectacular coral growth dominated by the branching scleractinian madrepora oculata at a depth of 380 460 m the general biohermal frame is strengthened by the common occurrence of the solitary scleractinian desmophyllum dianthus and the occasional presence of lophelia pertusa as documented by remotely operated vehicle survey this area is a hotspot of megafaunal diversity hosting among other also live specimens of the deep oyster neopycnodonte zibrowii the new coral province is located between the central mediterranean cwc provinces bari canyon santa maria di leuca south malta and the western and northern ones melilla catalan provencal ligurian canyons as for all the best developed cwc situations in the present mediterranean sea the new sardinian province is clearly influenced by levantine intermediate water which appears to be a main driver for cwc distribution and viability in this basin

field evidence for active normal faulting in tibet crustal thickening does not now occur in southern tibet field observations made during the chinese french expedition of 1980 support an earlier hypothesis based on a combined analysis of satellite images and fault plane solutions of earthquakes immediately north of the highest peaks of the himalayas the tectonic regime is dominated by east west extension we have mapped a large number of north south normal faults which sharply cut the glacial and post glacial morphology and followed several recent earthquake breaks along faults detected on satellite and aerial photographs microtectonic measurements in the quaternary suggest that the maximum principal stress is vertical

estimating lagrangian transport blending drifters with hf radar data and models results from the tosca experiment in the ligurian current north western mediterranean sea abstract lagrangian transport estimates are investigated using results from hf radar model and drifter data during a dedicated experiment in the ligurian current in the toulon area north western mediterranean sea uncertainty estimates on particle position d t are computed and compared to absolute dispersion d 0 t that provides an indication of the uncertainty in case of zero prior knowledge in agreement with previous studies radar results show that d t 1 2 d 0 t i e 6 km after 24 h model results are less reliable as it can be expected in highly nonlinear coastal flows without local data assimilation the central result of this paper is that when drifters are promptly deployed in an area of interest their data can be used to significantly improve transport estimates using the lagrangian blending algorithm lava with velocity fields from models or radar uncertainty can be reduced to 1 6 d 0 t i e 2 km after 24 h for both radar and model implying a much reduced search range in case of operational applications the method is also found to have some forecasting skills with uncertainty 1 2 d 0 t during the first 6 h sensitivity tests provide indications on relevant time and space scales of predictability and provide suggestions for appropriate drifter sampling strategies

pairwise surface drifter separation in the western pacific sector of the southern ocean the southern ocean plays a critical role in global climate yet the mixing properties of the circulation in this part of the ocean remain poorly understood here dispersion in the vicinity of the southern antarctic circumpolar current front one of the branches of the antarctic circumpolar current is studied using 10 pairs of surface drifters deployed systematically across the frontal jet and its flanks drifter pairs were deployed with an initial separation of 13 m and report their position every hour the separation of the pairs over 7 months in terms of their finite scale lyapunov exponents fsle dispersion and diffusivity is characterized and related to expected behavior from quasi geostrophic qg and surface quasi geostrophic sqg theories the fsle analysis reveals two submesoscale regimes with sqg like behavior at scales below 3 2 km and mixed qg sqg behavior at scales between 3 2 and 73 km the dispersion analysis however suggests qg like behavior for the smallest scales both dispersion and diffusivity appear isotropic for scales up to 500 km finally there is no clear indication of a cross jet variation of drifter dispersion

parameterization of mixed layer eddies part i theory and diagnosis ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean in this paper a parameterization for the restratification driven by finite amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal the streamfunction is proportional to the product of the horizontal density gradient the mixed layer depth squared and the inertial period hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence in this paper the parameterization is theoretically motivated confirmed to perform well for a wide range of mixed layer depths rotation rates and vertical and horizontal stratifications it is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification two companion papers discuss the numerical implementation and the climate impacts of this parameterization

a high angle fault within the devonian tilicho pass formation on the west bank of the kali gandaki river north of jomsom central nepal

clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern andes clastic dike swarms are intruded into a cenozoic foreland fold and thrust belt in southern chile the dike material consists of sandstone and conglomerate with clasts as much as 25 cm in diameter brecciated wall rocks are also found in the clastic matrix the dikes often exceed 50 cm in width and hundred of metres in length in outcrop and are oriented overwhelmingly transverse to fold axes and parallel to cross joints the dike swarms are concentrated near the toe of major thrusts where they are found injected into the hanging wall a regional axial planar spaced cleavage is developed in the clastic dikes and sills clearly postdating injection of clastic material dike injection postdates at least the initiation of extension fractures the cross joint set within the swarms the dike intrusions represent as much as 20 extension parallel to fold axes in addition to several percent extension represented regionally by the cross joints the structural features of the dike swarms and their geometric relationship to other structures suggest rapid single phase injection the arrival of the front edge of a thrust on an already highly overpressured sedimentary sequence would cause an instantaneous increase in the overburden pressure and therefore could result in injection of a dense slurry of wet coarse sediments along preexisting planes of weakness field relationships of mesoscopic structures suggest the following evolution cross joint development incipient cleavage development initiation of thrusting and buckling clastic dike injection regional spaced cleavage development and associated late stage tightening of folds

submesoscale impacts on horizontal and vertical transport in the gulf of mexico 1 impacts of submesoscale processes on transport are investigated numerically in an energetic mesoscale flow with an ocean model run at two horizontal resolutions 1 and 5 km the focus is the northwestern gulf of mexico where the loop current eddies are surrounded by smaller vortices by increasing the horizontal resolution the number and strength of submesoscale eddies and vorticity filaments within the mixed layer increase dramatically and with them the vertical velocities inside the coherent eddies and at their peripheries increased vertical velocities for increasing resolution are associated to near inertial motions and they are not limited to the mixed layer but are found at all depths horizontal velocities on the contrary are similar lagrangian isobaric tracers are deployed close to the surface and at 100 m and three dimensional neutrally buoyant particles are released close to the surface at the base of the mixed layer and at 100 m the modeled horizontal dispersion curves for each deployment depth are independent of the kind of particles and of horizontal resolution close to the ocean surface however convergence zones generated by submesoscale ageostrophic motions and resolved at 1 km resolution influence the details of the tracer distributions vertical dispersion increases by several folds for increasing resolution at all depths explored with the largest differences found close to the surface therefore submesoscales processes play a fundamental role in driving vertical transport in eddy dominated flows both within and below the mixed layer for times comparable to the eulerian time scale

mesoscale eddy characteristics in the interior subtropical southeast indian ocean tracked from the leeuwin current system abstract two oppositely rotating mesoscale eddies originating from the leeuwin current were captured during a research cruise in the interior southeast indian ocean in august 2012 a few hundred kilometers off the west coast of australia the two eddies had different vertical structures the anticyclonic eddy had stronger vertical shear above 200 m and a less stratified thermocline below the mixed layer while the cyclonic eddy had a more barotropic structure in the upper 500 m compared with the same types of eddies sampled in 2003 close to the australian coast the 2012 anticyclonic eddy had a larger radius deeper isothermal depths and higher peak velocity whereas the 2012 cyclonic eddy had a similar structure with the 2003 survey we use an argo float and three surface drifters deployed and trapped in the anticyclonic eddy to track its evolution over a 4 month period the eddy was observed to propagate 1000 km further to the west indicating that the leeuwin current properties of the eddy may be preserved for over 2000 km off the west coast of australia the eddy appeared to have experienced radial excursions relative to the eddy center with periodicity of 4 6 days and 15 days during their anticlockwise motions the radial movements of the drifters appeared to be constrained by the radial momentum balance within the eddy the importance of eddy distortions to ocean primary production in anticyclonic eddies in the southeast indian ocean warrants further studies

mixed layer instabilities and restratification abstract the restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied the lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical these instabilities which are referred to as mixed layer instabilities mlis differ from instabilities in the ocean interior because of the weak surface stratification spatial scales are o 1 10 km and growth time scales are on the order of a day linear stability analysis and fully nonlinear simulations are used to study mlis and their impact on mixed layer restratification the main result is that mlis are a leading order process in the ml heat budget acting to constantly restratify the surface ocean climate and regional ocean models do not resolve the scales associated with mlis and are likely to underestimate the rate of ml restratification and consequently suffer from a bias in sea surface temperatures and ml depths in a

surface drifter pair spreading in the north atlantic 1 this study examines spreading of surface drifter pairs deployed as part of the clivar mode water dynamic experiment climode project in the gulf stream region the spreading is resolved at hourly resolution and quantified by relative dispersion and finite scale lyapunov exponents at scales from 1 3 km to 300 500 km the dispersion follows richardson s law indicating stirring by eddies comparable in scale to the pair separation distance at larger scales the spreading becomes a random walk described by a constant diffusivity the behavior from 1 3 km to the local deformation radius is inconsistent with the enstrophy cascade of 2 d quasigeostrophic turbulence to test various hypotheses for this result drifter pair spreading is examined for pairs that were not launched together pairs deployed in the eastern subtropical north atlantic and climode pairs subsampled to daily temporal resolution our results indicate the presence of significant energy at the submesoscale in the gulf stream region which flattens the wave number spectrum and dominates surface stirring at this scale range results in the less energetic subtropical eastern atlantic are more equivocal

the tibetan side of the india eurasia collision results are reported from the 1980 joint french chinese field expedition in tibet the area covered was from the high himalaya in the south to the region of nagqu 250 km north of yangbajain ophiolites in the zangbo valley represent remnants of the crust of an ocean basin which lay adjacent to the gangdise granodiorite belt in the late mesozoic the ophiolites were thrust to the south onto the cretaceous melange and triassic flysch but the age of this event is unclear in the tertiary sediments of the indian margin and the xigaze basin were folded with steeply dipping cleavage which indicates some north south shortening of the crust however the tertiary volcanic sequence on the lhasa block and further north shows comparatively little folding and thrusting in the quaternary deformation of tibet was characterized by east west extension

lagrangian drifter dispersion in the southwestern atlantic ocean abstractin the framework of monitoring by ocean drifters mondo project a set of lagrangian drifters were released in proximity of the brazil current the western branch of the subtropical gyre in the south atlantic ocean the experimental strategy of deploying part of the buoys in clusters offers the opportunity to examine relative dispersion on a wide range of scales adopting a dynamical systems approach the authors focus their attention on scale dependent indicators like the finite scale lyapunov exponent fsle and the finite scale mean square relative velocity fsrv between two drifters as a function of their separation and compare them with classic time dependent statistical quantities like the mean square relative displacement between two drifters and the effective diffusivity as functions of the time lag from the release the authors find that dependently on the given observable the quasigeostrophic turbulence scenario is overall compatible with their data analysis with discrepancies fr

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

in situ estimates of submesoscale horizontal eddy diffusivity across an ocean front in the last decade the rapid advancements in computational power have favored the development of high resolution numerical models capable of directly resolving small scale structures such as fronts and filaments such models have greatly improved our understanding of submesoscale dynamics at the same time the small dimensions and short duration of these structures still pose major challenges for small scale dedicated field experiments for this reason submesoscale studies from in situ observations are still relatively scarce and quantitative estimates of key physical parameters for high resolution numerical models such as horizontal eddy diffusivity are still lacking this study presents a novel approach for computing in situ horizontal eddy diffusivity associated with frontal structures by combining cross front widths derived from surface thermosalinograph sections with stirring rates estimated from lagrangian drifter trajectories the method is applied to the measurements collected across a frontal structure observed in the western part of the gulf of lion during the latex10 campaign lagrangian transport experiment 1 24 september 2010 a total of 76 estimates of eddy diffusivity were obtained for strain rates of 0 70 and 1 21 day 1 and front widths horizontal scales ranging between 1 and 4 km the estimates are log normally distributed with 70 of the values ranging between 0 4 and 5 m 2 s 1 further analysis based on high resolution simulations and remote sensed observations as well as dedicated field experiments will help to assess the robustness of some of the assumptions at the base of the proposed approach and to extend the results to different ocean regions

targeted lagrangian sampling of submesoscale dispersion at a coastal frontal zone 1 the potential impact of rapidly evolving submesoscale motions on relative dispersion is at the forefront of physical oceanography posing challenges for both observations and modeling a persistent coastal front driven by river outflows in the north western mediterranean sea is targeted by two observational cruises conducted in the summer of 2010 the frontal zone is sampled using drifters launched with a multi scale strategy consisting of modules of triplets released on either side of the front by small boats this experiment is original in that the submesoscale range of 100 m to 1000 m is directly targeted and the results are expected to provide guidance for practical applications such as prediction of the initial spreading of pollutants and biogeochemical tracers the influence of submesoscale motions on relative dispersion is quantified using both particle mean square separation as a function of time and scale dependent finite size lyapunov exponents fsle our main finding is the identification of a local dispersion regime with values reaching as high as 20 days 1 at drifter pair separation distances of 100 m this value is more than an order of magnitude greater than that obtained by drifters in the offshore ligurian current the ligurian sea circulation is modeled using a fully realistic regional ocean modeling system roms with 1 60 horizontal resolution it is found that the numerical model significantly underestimates the relative dispersion at submesoscales indicating the need for particle dispersion parameterizations for unresolved processes

regional stress field and rifting in western europe abstract baumann h 1981 regional stress field and rifting in western europe in j h illies editor mechanism of graben formation tectonophysics 73 105 111 in situ stress determination is one possibility to determine stress magnitudes in the earth s crust most measurements especially in the northern alpine foreland have been carried out by using the doorstopper technique stress magnitudes are presented as excess stresses a number of sites where stresses have been determined gave sufficiently high values to statistically determine stress directions for the following tectonic blocks 1 western alps 2 their immediate foreland with the rhinegraben and 3 the rhenish shield bordering on the rift segment of the lower rhine embayment in discussing results of the statistical analyses of stress data it is suggested that stresses measured in the western alps have mainly a topographic origin in the alpine foreland to the north of the rhenish shield topographic stresses are superimposed on active tectonic stress considering the structural and lithological differences the foreland blocks show a different response to the same tectonic stress field which trends for 1 at about 146 this active stress field causes shear rifting in the upper rhinegraben but extensional rifting in the lower rhine embayment in the rhenish shield area only local step faults are observed in direction of 1 due to the ductile behaviour of its basement