dynamics of wind forced coherent anticyclones in the open ocean we numerically study the dynamics of coherent anticyclonic eddies in the ocean interior for the hydrostatic rotating stably stratified turbulence we use a high resolution primitive equation model forced by small scale winds in an idealized configuration many properties of the horizontal motions are found to be similar to those of two dimensional and quasi geostrophic turbulence major differences are a strong cyclone anticyclone asymmetry linked to the straining field exerted by vortex rossby waves which is also found in shallow water flows and the complex structure of the vertical velocity field which we analyze in detail locally the motion can become strongly ageostrophic and vertical velocities associated with vortices can reach magnitudes and levels of spatial complexity akin to those reported for frontal regions transport and mixing properties of the flow field are further investigated by analyzing lagrangian trajectories particles released in the pycnocline undergo large vertical excursions because of the vertical velocities associated to the vortices with potentially important consequences for marine ecosystem dynamics

geophysical and geochemical methods applied to investigate fissure related hydrothermal systems on the summit area of mt etna volcano italy abstract a multidisciplinary approach integrating self potential soil temperature heat flux co 2 efflux and gravity gradiometry signals was used to investigate a relatively small fissure related hydrothermal system near the summit of mt etna volcano italy measurements were performed through two different surveys carried out at the beginning and at the end of july 2009 right after the end of the long lived 2008 2009 flank eruption and in coincidence with an increase in diffuse flank degassing related to a reactivation of the volcano leading to the opening of a new summit vent nsec the main goal was to use a multidisciplinary approach to the detection of hidden fractures in an area of evident near surface hydrothermal activity despite the different methodologies used and the different geometry of the sampling grid between the surveys all parameters concurred in confirming that the study area is crossed by faults related with the main fracture systems of the south flank of the volcano where a continuous hydrothermal circulation is established results also highlighted that hydrothermal activity in this area changed both in space and in time these changes were a clear response to variations in the magmatic system notably to migration of magma at various depth within the main feeder system of the volcano the results suggest that this specific area initially chosen as the optimal test site for the proposed approach can be useful in order to get information on the potential reactivation of the summit craters of mt etna

scales and structures of large lake eddies 1 observations of currents and near surface temperatures from lake superior reveal a surprisingly rich field of eddies that extended throughout the water column and were present throughout the lake and during all seasons despite their ubiquity the lake eddies have previously gone unreported in the literature these observations of the eddy velocities and surface temperatures suggest that we have to revise our conceptual understanding of the vertical and horizontal transport mechanisms within large lakes to take into account persistent mesoscale turbulence

partitioning of kinetic energy in the arctic ocean s beaufort gyre kinetic energy ke in the arctic ocean s beaufort gyre is dominated by the mesoscale eddy field that plays a central role in the transport of freshwater heat and biogeochemical tracers understanding beaufort gyre ke variability sheds light on how this freshwater reservoir responds to wind forcing and sea ice and ocean changes the evolution and fate of mesoscale eddies relate to energy pathways in the ocean e g the exchange of energy between barotropic and baroclinic modes mooring measurements of horizontal velocities in the beaufort gyre are analyzed to partition ke into barotropic and baroclinic modes and explore their evolution we find that a significant fraction of water column ke is in the barotropic and the first two baroclinic modes we explain this energy partitioning by quantifying the energy transfer coefficients between the vertical modes using the quasi geostrophic potential vorticity conservation equations with a specific background stratification observed in the beaufort gyre we find that the quasi geostrophic vertical mode interactions uphold the persistence of ke in the first two baroclinic modes consistent with observations our results explain the specific role of halocline structure on ke evolution in the gyre and suggest depressed transfer to the barotropic mode this limits the capacity for frictional dissipation at the sea floor and suggests that energy dissipation via sea ice ocean drag may be prominent

convective modifications of a geostrophic eddy field ocean convection often occurs in regions of mesoscale eddy activity where convective mixing and geostrophic eddy dynamics interact the authors examine the interactions between a group of geostrophic eddies and convective mixing induced by surface buoyancy loss through a series of numerical simulations using a nonhydrostatic boussinesq model the eddies are initially baroclinic with a surface intensified density anomaly and sheared flow but they are stable to baroclinic instability because of their small size in the absence of buoyancy loss eddy mergers occur much as in previous studies of geostrophic turbulence with the addition of surface buoyancy loss the surface stratification is eroded by small scale convection the convective mixing is highly heterogeneous being deeper in regions of weaker initial stratification and shallower in more strongly stratified regions the deformation radius is reduced in mixing regions and the weakly stratified eddies become baroclinically unstable the barotropic component of kinetic energy increases as convection proceeds largely due to the conversion of the available potential energy of the eddies in the baroclinic instability process the convective forcing therefore provides a means of increasing the barotropic component of the eddy kinetic energy by enabling the baroclinic instability the fluid is efficiently homogenized by the energetic eddy field leading to a few isolated eddies separated by a well mixed fluid these simulations provide a possible explanation for energetic eddy fields observed during convective periods in the labrador sea

significant sink of ocean eddy energy near western boundaries ocean eddies generated through instability of the mean flow are a vital component of the energy budget of the global ocean modelling combined with satellite altimetry data suggests that the energy from westward propagating eddies is scattered and eventually dispersed when they reach the western boundary of an ocean basin

barotropic rossby waves radiating from tropical instability waves in the pacific ocean abstracttropical instability waves are triggered by instabilities of the equatorial current systems and their sea level signal with peak amplitude near 5 n is one of the most prominent features of the dynamic topography of the tropics cross spectral analysis of satellite altimetry observations shows that there is sea level variability in the pacific ocean as far north as hawaii i e 20 n that is coherent with the sea level variability near 5 n associated with tropical instability waves within the uncertainty of the analysis this off equatorial variability obeys the dispersion relation for nondivergent barotropic rossby waves over a fairly broad range of periods 26 38 days and zonal wavelengths 9 23 of longitude that are associated with tropical instability waves the dispersion relation and observed wave properties further suggest that the waves are carrying energy away from the instabilities toward the north pacific subtropical gyre which together with the observed coherence of the sea

circulation and stirring in the southeast pacific ocean and the scotia sea sectors of the antarctic circumpolar currenta abstractthe large scale middepth circulation and eddy diffusivities in the southeast pacific ocean and scotia sea sectors between 110 and 45 w of the antarctic circumpolar current acc are described based on a subsurface quasi isobaric rafos float based lagrangian dataset these rafos float data were collected during the diapycnal and isopycnal mixing experiment in the southern ocean dimes the mean flow adjusted to a common 1400 m depth shows the presence of jets in the time averaged sense with speeds of 6 cm s 1 in the southeast pacific ocean and upward of 13 cm s 1 in the scotia sea these jets appear to be locked to topography in the scotia sea but aside from negotiating a seamount chain are mostly free of local topographic constraints in the southeast pacific ocean the eddy kinetic energy eke is higher than the mean kinetic energy everywhere in the sampled domain by about 50 the magnitude of the eke increases drastically by a factor of 2 or more as the current crosses over the hero and

a multidisciplinary approach to detect active pathways for magma migration and eruption at mt etna sicily italy before the 2001 and 2002 2003 eruptions two strong flank eruptions occurred in july august 2001 and from late october 2002 to late january 2003 at mt etna volcano the two eruptions mainly involved the upper southern flank of the volcano a particularly active area during the last 30 years damaging several tourist facilities and threatening some villages the composite eruptive activity on the upper southern flank of mt etna during 2001 2003 has confirmed a posteriori the results of a multidisciplinary study started well before its occurrence by combining geological seismic and geochemical data gathered in this part of the volcano we were able in fact to highlight fractured zones likely to be re activated in the near future in this area where the largest majority of eruptive fissures in the recent past opened along n120 to n180 ranging directions the spatial distribution of earthquake epicentres during the period june 30th 2000 june 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre 2001 period and that of the 2001 and 2002 lateral eruptions soil co2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids mainly co2 and water vapour along some nnw sse trending volcano tectonic structures of the area even during inter eruptive periods indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of etna the temporal changes in both seismic and geochemical data from june 30th 2000 to june 30th 2001 were compared with the evolution of volcanic activity the comparison allowed to recognize at least two sequences of anomalous signals august to december 2000 and april to june 2001 likely related to episodes of step like magma ascent towards the surface as indicated by the following eruptive episodes the n120 to n180 structural directions are in accord with one of the main structural lines affecting eastern sicily they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of etna in the near future this study also pointed out the high instability of the southern slope of etna a sector where the potential hazard by lava flow invasion will remain high also in the near future

the vertical partition of oceanic horizontal kinetic energy to produce an interpretation of the surface kinetic energy as measured by altimeters a survey is made of the vertical structure of kinetic energy profiles in a large number of globally distributed long current meter records although the data are geographically confined primarily to a latitude band in the north pacific to the north atlantic and to a few moorings in the south atlantic the results show generally speaking that most regions are dominated by the barotropic and first baroclinic modes because of the near surface intensification of baroclinic modes altimeters primarily reflect the first baroclinic mode and thus the motion of the main thermocline there is good quantitative agreement with a few exceptions with estimates of the surface kinetic energy obtained from the topex poseidon altimeter and from vertical extrapolations to the surface of the mooring profiles these results are consistent with previous suggestions that barotropic models have little skill in depicting variability as seen in the altimeter data an eof analysis is shown to produce fictitious mode coupling unless the dynamical modes have very different energy levels

eastern boundary contribution to the residual and meridional overturning circulations a model of the thermocline linearized around a specified stratification and the barotropic linear winddriven stommel solution is constructed the forcings are both mechanical the surface wind stress and thermodynamical the surface buoyancy boundarycondition the effects of diapycnal diffusivity and of eddy fluxesofbuoyancy parameterizedintermsofthelarge scalebuoyancygradient areincluded theeddyfluxes of buoyancy are especially important near the boundaries where they mediate the transport in and out of the narrow ageostrophic down upwelling layers the dynamics of these narrow layers can be replaced by effective boundary conditions on the geostrophically balanced flow the effective boundary conditions state that the residual flow normal to the effective coast vanishes the separate eulerian and eddy induced components may be nonzero this formulation conserves the total mass and the total buoyancy while permitting an exchangebetweentheeulerianandeddytransportofbuoyancy withinthedown upwellinglayers inturn this exchange allows buoyancy gradients along all solid boundaries including the eastern one a special focus is on the buoyancy along the eastern and western walls since east west buoyancy difference determines the meridional overturning circulation the inclusion of advection of buoyancy by the barotropic flow allows a meaningful distinction between the meridional and the residual overturning circulations while retaining the simplicity of a linear model the residual flow in both meridional and zonal directions reveals how the subsurface buoyancy distribution is established and in particular how the meridional buoyancy gradient is reversed at depth in turn the horizontal buoyancy gradient maintains stacked counterrotating cells in the meridional and residual overturning circulations quantitative scaling arguments are given for each of these cells which show how the buoyancy forcing the wind stress and the diapycnal and eddy diffusivities as well as the other imposed parameters affect the strength of the overturn

hydrothermal circulation beneath mount pelee inferred by self potential surveying structural and tectonic implications abstract self potential sp surveys were made on mount pelee volcano martinique island french west indies in 1991 and 1992 in order to recognize its hydrothermal system the associated groundwater channeling and the main superficial structures of the massif almost 70 km of profiles were carried out with an average sample spacing of 50 m measurements essentially reveal negative sp anomalies down to 1700 mv with high gradients 1 83 mv m due to the infiltration of meteoric water into the massif rims of summit calderas morne macouba and etang sec present sharp negative sp anomalies on the western northern and eastern flanks negative sp anomalies indicate no upward water flow beneath mount pelee summit on the southwestern volcano flank a 3 5 6 km horseshoe shaped structure corresponding to a southwest flank collapse event older than 25 000 years bp is clearly identified by the sp mapping high gradients border the inner southern rim from morne calebasse to st pierre town and the caribbean sea along the northern rim of the horseshoe shaped structure the negative sp anomalies give place to a positive sp anomaly up to 200 mv of sw ne trend this zone covers the area of two active hot springs sources chaudes and puits chaud 40 65 c marine magnetic surveys and bathymetry show that the horseshoe shaped structure spreads into the caribbean sea up to about 10 km from the coast buried structural discontinuities are evidenced inside the flank collapse structure the upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards this discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south southwestern flank and covered by recent pyroclastic deposits or more probably the trace of a bulge landslide a circulation model of the hydrothermal waters is proposed rainfall 5 6 m year is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement there the groundwater constitutes perched aquifers at the contact of the bulge landslide or of the hypothetical old caldera rim along the inner northern border of the flank collapse structure the phreatic water is reheated warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops of medium temperature finally the main part of the meteoric water is channeled along the old caldera rim or along the bulge landslide towards the south flank of mount pelee where some gaps in the rim exist there the groundwater finds again a subhorizontal gravitational circulation along mount pelee slopes into the caribbean sea

possible closed system pingo and ice wedge thermokarst complexes at the mid latitudes of utopia planitia mars abstract on earth hydrostatic or closed system pingos csps are perennial ice cored mounds formed by the freeze thaw cycling of water when or as thermokarst lakes lose their water by drainage or evaporation the mounds vary in shape from circular or sub circular to elongate are sub kilometre in their long axes and may reach decametres in height often the mounds show summit depressions radial fractures and single tiers or benches as the csps degrade small scale debris flows or slumps occur end stage degradation typically exhibits debris laden ramparts elevated metres above the surrounding terrain typically the csps originate and develop where deep and continuous permafrost is ice rich i e infused with excess ice as it is in the tuktoyaktuk coastlands of northern canada mid to northern alaska and northeast russia in these areas or regions the terrain often is populated by a thermokarst lakes and alases thermokarst lake basins absent of water b fields of small scale ice wedge polygons either low centred or high centred relative to the polygon margins and c melt water filled or emptied polygon margin troughs or corner pits individual troughs and pits connected by means of the local topographical gradient comprises beaded stream systems or networks here we report describe and discuss a suite of candidate csps at the mid latitudes of utopia planitia up 35 50 n 80 115 e the morphologies scale and height of the martian mounds as well as the surface textures and characteristics landscape features and spatially associated landforms are consistent with the csps observed in ice rich regions on earth the up mounds are nested in or reside adjacent to flat floored possibly thermokarstic depressions small scale polygons some of which exhibit low or high centres relative to their margins and connected polygon margin depressions or pits that mirror beaded stream systems in ice rich terrain on earth the size frequency distribution of craters in our study region precludes a surface younger than 100 ma thus the csp like mounds in up and the pre mound periglacial revisions of the landscape presented by us may be markers of freeze thaw cycling that occurred much earlier in the amazonian epoch than most of the current discussions about periglaciation in up suggest

the ocean mesoscale regime of the reduced gravity quasigeostrophic model abstracta statistical equilibrium geostrophic turbulence regime of the stochastically forced one layer reduced gravity quasigeostrophic model is identified in which the numerical solutions are

open ocean regimes of relative dispersion as two fluid particles separate in time the entire spectrum of eddy motions is being sampled from the smallest to the largest scales in large scale geophysical systems for which the earth rotation is important it has been conjectured that the relative diffusivity should vary respectively as d2 and d4 3 for distances respectively smaller and larger than a well defined forcing scale of the order of the internal rossby radius with d the r m s separation distance particle paths data from a mid latitude float experiment in the central part of the north atlantic appear to support these statements partly two particles initially separated by a few km within two distinct clusters west and east of the mid atlantic ridge statistically dispersed following a richardson regime d2 t3 asymptotically for r m s separation distances between 40 and 300 km in agreement with a d4 3 law at early times and for smaller separation distances an exponential growth in agreement with a d2 law was briefly observed but only for the eastern cluster with an e folding time around 6 days after a few months or separation distances greater than 300 km the relative dispersion slowed down naturally to the taylor absolute dispersion regime

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

the role of mixed layer instabilities in submesoscale turbulence upper ocean turbulence at scales smaller than the mesoscale is believed to exchange surface and thermocline waters which plays an important role in both physical and biogeochemical budgets but what energizes this submesoscale turbulence remains a topic of debate two mechanisms have been proposed mesoscale driven surface frontogenesis and baroclinic mixed layer instabilities the goal here is to understand the differences between the dynamics of these two mechanisms using a simple quasi geostrophic model the essence of mesoscale driven surface frontogenesis is captured by the well known surface quasi geostrophic model which describes the sharpening of surface buoyancy gradients and the subsequent breakup in secondary roll up instabilities we formulate a similarly archetypical eady like model of submesoscale turbulence induced by mixed layer instabilities the model captures the scale and structure of this baroclinic instability in the mixed layer a wide range of scales are energized through a turbulent inverse cascade of kinetic energy that is fuelled by the submesoscale mixed layer instability major differences to mesoscale driven surface frontogenesis are that mixed layer instabilities energize the entire depth of the mixed layer and produce larger vertical velocities the distribution of energy across scales and in the vertical produced by our simple model of mixed layer instabilities compares favourably to observations of energetic wintertime submesoscale flows suggesting that it captures the leading order balanced dynamics of these flows the dynamics described here in an oceanographic context have potential applications to other geophysical fluids with layers of different stratifications

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

reconstructing the ocean interior from high resolution sea surface information abstractwhen evaluated against the 1 30 resolution submesoscale resolving ofes model outputs the previously published interior surface quasigeostrophic method from the 2013 study by wang et

pattern formation at the ocean surface sargassum distribution and the role of the eddy field positively buoyant organisms such as the macroalga sargassum and the cyanobacterium trichodesmium often form surface accumulations visible in satellite imagery that have lateral scale separation of tens of kilometers and cannot be explained by langmuir circulation here we discuss the accumulation of floating materials in the ocean in presence of meso and submesoscale activity using high resolution simulations of the ocean mesoscale in both idealized a 3 dimensional box where coherent eddies are forced by small scale winds and realistic domains western gulf of mexico where extensive concentrations of floating sargassum have been recorded in satellite images we show that the distribution of tracers at the ocean surface departs rapidly from that observed a few tens of meters below it such distribution does not resemble that observed for passive tracers in quasi geostrophic turbulence the strong divergence and convergence zones generated at the surface by ageostrophic processes in the submesoscale range are responsible for the creation of areas where the floating material accumulates floating particles are expelled from the core of mesoscale eddies and concentrate in convergence regions in patterns comparable to the ones observed through the satellite images in light of those results sargassum and or trichodesmium may provide a useful proxy to track convergence divergence processes resulting from ageostrophic processes at the ocean surface

bottom trapped currents as statistical equilibrium states above topographic anomalies oceanic geostrophic turbulence is mostly forced at the surface yet strong bottom trapped flows are commonly observed along topographic anomalies here we consider the case of a freely evolving initially surface intensified velocity field above a topographic bump and show that the self organization into a bottom trapped current can result from its turbulent dynamics using equilibrium statistical mechanics we explain this phenomenon as the most probable outcome of turbulent stirring we compute explicitly a class of solutions characterized by a linear relation between potential vorticity and streamfunction and predict when the bottom intensification is expected using direct numerical simulations we provide an illustration of this phenomenon that agrees qualitatively with theory although the ergodicity hypothesis is not strictly fulfilled

soil and fumarole gases of mount etna geochemistry and relations with volcanic activity abstract between 1993 and 1996 gas samples were collected on mt etna volcano from both high and low temperature fumaroles and from soils in areas of anomalous degassing located on the flanks of the volcanic edifice the chemical composition of all the emitted gases is consistent with their magmatic origin during their transport to the surface they would undergo shallow mixing processes mostly with air locally as in the case of a point in the lower southwestern flank of the volcano p39 very high contents of he and ch4 indicate that deep gases mainly interact with ground waters and also with a hydrocarbon reservoir the isotopic composition of carbon in co2 from these gases also suggests its primary magmatic origin with inferred 13 c values of magmatic co2 in the range 2 to 1 vs pdb such values significantly more positive than those measured in morbs are in the typical range measured at the other mediterranean volcanoes 5 to 0 more negative values can be explained by shallow interactions between magmatic and organic co2 and or between the former and cold t 120 c ground waters both chemical and isotopic gas geothermometers agree in indicating calculated temperatures ranging from 180 to 270 c for the soil gases collected from low temperature fumaroles near the summit and temperatures around 150 c for the cold gases from p39 thus confirming the presence of a hydrothermal aquifer beneath this point a chemical geothermometer applied on the gases collected from the high temperature fumaroles near the summit craters shows equilibrium temperatures ranging from 385 to 690 c lastly many of the studied parameters showed anomalous variations in time during the studied period the most important of these concerned the flux of co2 through the soil and the concentration of soil h2 which were closely correlated with strong increases in the volcanic activity of etna

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

statistical analysis reveals spatial and temporal anomalies of soil co2 efflux on mount etna volcano italy abstract extensive geochemical surveys were carried out on the western flank of mt etna volcano for the determination of soil co 2 effluxes in order to study the relationship between soil gas anomalies faults and volcanic activity the areas of santa maria di licodia sml and w rift wr were selected because of their importance within the volcano tectonic framework of etna two gas surveys were performed in each area in different periods november 2005 and may 2006 in sml september 2007 and june 2008 in wr with 2140 measurements in total in each survey data were log normally distributed and were statistically different from the other surveys therefore their standard normal form was used to compare them log probability plots revealed five populations of data in each survey due to varying degrees of mixing between biogenic and magmatic co 2 and indicated anomalous co 2 effluxes for values 36 g m 2 d 1 magmatic output was 39 2 t d 1 in november 2005 15 8 t d 1 in may 2006 98 4 t d 1 in september 2007 and 234 1 t d 1 in june 2008 natural neighbor interpolation of standardized data produced distribution maps that showed some clustering of anomalous values along directions possibly related to hidden faults compatible with volcanic or regional structural trends analysis of magmatic co 2 emissions in time suggested a possible influence from seasonal variations but comparison with volcanic activity of etna also indicated a volcanic influence accompanying the 2008 2009 flank eruption

retrieving density and velocity fields of the ocean s interior from surface data using the interior surface quasigeostrophic isqg method the density and horizontal velocity fields of the ocean s interior can be retrieved from surface data this method was applied to the simple ocean data assimilation soda and the hybrid coordinate ocean model hycom navy coupled ocean data assimilation ncoda reanalysis data sets the input surface data include sea surface height ssh sea surface temperature sst sea surface salinity sss and a region averaged stratification the retrieved subsurface fields are compared with reanalysis data for three tested regions and the results indicate that the isqg method is robust the isqg method is particularly successful in the energetic regions like the gulf stream region with weak stratification and the kuroshio region with strong correlation between sea surface density ssd and ssh it also works though less satisfactorily in the agulhas leakage region the performance of the isqg method in retrieving subsurface fields varies with season and peaks in winter when the mixed layer is deeper and stratification is weaker in addition higher resolution data may facilitate the isqg method to achieve a more successful reconstruction for the velocity retrieval our results suggested that the isqg method can be used to reconstruct the ocean interior from the satellite derived ssh sst and sss data in the near future

vertical structure of eddies and rossby waves and their effect on the atlantic meridional overturning circulation at 26 5 n the meridional overturning circulation moc at inline image in the atlantic has a standard deviation of 4 9 sv and contains large fluctuations at subannual periods the geostrophic component of the moc is believed to be influenced on subannual time scales by eddies and rossby waves to quantify this effect the vertical structure and surface characteristics of westward propagating signals are studied using altimetric data and full depth mooring measurements from the rapid array at inline image westward propagating features are observed in the western north atlantic in both data sets and have periods of 80 250 days in the first baroclinic mode these features are still observed by the rapid moorings 20 km offshore of the western boundary the western boundary also exhibits deep variability characterized by enhanced energy in higher baroclinic modes the effect of eddies and rossby waves on the geostrophic transport is quantified by representing their vertical structure with the first baroclinic mode in total 42 of the variance of the transbasin thermocline transport inferred from geostrophic calculations at inline image can be attributed to first mode variability which is associated with eddies and rossby waves at periods of 80 250 days the standard deviation of the transbasin thermocline transport due to eddies and rossby waves is estimated to be 2 6 sv

diagnosing the energy cascade in a model of the north atlantic spectral potential and kinetic energy densities and fluxes in horizontal wavenumber space are estimated in an eddy resolving model of the north atlantic in agreement to recent observational results near surface kinetic energy fluxes are negative over wide regions of the north atlantic indicative of an inverse energy cascade this inverse kinetic energy cascade is found over a wide depth range but both the spectral kinetic energy density and the corresponding flux show no clear dependency on rossby radius or rhines scale potential energy fluxes tend to be positive and show a direct potential energy cascade towards a scale which is related to the rossby radius in the subtropical north atlantic

generation and separation of mesoscale eddies from surface ocean fronts abstractthis study is motivated by arctic ocean observations of sub mixed layer eddies found at large distances from their assumed formation region of a surface ocean front eddy formation is explored through high resolution numerical simulations of surface fronts separating two mixed layers with a range of configurations similar to those observed in the arctic ocean this study finds that frontal instabilities lead to the development of self propagating dipoles which have the potential to propagate far from the front if interactions with other eddies are avoided however most dipoles are unbalanced consisting of a dominating surface cyclone and a weaker anticyclone below and thus propagate on curved trajectories with eventual recirculation back to the front their maximum separation distance from the front depends on the ratio of self advecting velocities balanced dipoles that have 1 and the ability to propagate far from the front for dipoles generated numerically this study estimates u

a lagrangian based approach for determining trajectories taxonomy and turbulence regimes abstract the use of the ratio between the acceleration and velocity time scales y ta t to separate lagrangian trajectories in homogeneous classes is proposed in fact when analyzing subsurface floats data in the atlantic ocean and surface drifters data in the world s ocean basins it is observed that trajectories having different values of y are characterized by different shapes correlation and dispersal properties in particular trajectories having similar values of the acceleration and velocity time scales clearly show the influence of eddies and are characterized by an oscillating velocity correlation function it is shown here that this trajectory screening is a useful procedure to rationalize the analysis of real lagrangian trajectories and to avoid a mixture of different regimes when averaging quantities the mean statistical quantities computed averaging on quasi homogeneous datasets put in evidence the role of the coherent structures in the dispersion properties both in time and in the ma

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

the scales and equilibration of midocean eddies freely evolving flow quasigeostrophic turbulence theory and numerical simulation are used to study the mechanisms determining the scale structure and equilibration of mesoscale ocean eddies the present work concentrates on using freely decaying geostrophic turbulence to understand and explain the vertical and horizontal flow of energy through a stratified horizontally homogeneous geostrophic fluid it is found that the stratification profile in particular the presence of a pycnocline has significant qualitative effects on the efficiency and spectral pathways of energy flow specifically with uniform stratification energy in high baroclinic modes transfers directly quickly within a few eddy turnaround times and almost completely to the barotropic mode by contrast in the presence of oceanlike stratification kinetic energy in high baroclinic modes transfers intermediately to the first baroclinic mode whence it transfers inefficiently and incompletely to the barotropic mode the efficiency of transfer to the barotropic mode is reduced as the pycnocline is made increasingly thin the b effect on the other hand improves the efficiency of barotropization but for oceanically realistic parameters this effect is relatively unimportant compared to the effects of nonuniform stratification finally the nature of turbulent cascade dynamics is such as to lead to a concentration of first baroclinic mode kinetic energy near the first radius of deformation which in the case of a nonuniform and oceanically realistic stratification has a significant projection at the surface this may in part explain recent observations of surface eddy scales by topex poseidon satellite altimetry which indicate a correlation of surface height variance with the scale of the first deformation radius

he ar o sr and nd isotope constraints on the origin and evolution of mount etna magmatism abstract the 0 5 ma history of the origin and evolution of mount etna sicily has been investigated by analysing the isotopic composition of he ar o sr and nd in 21 selected lava samples the near constancy of the isotopic compositions of oxygen 18 o 5 4 0 3 and of helium trapped in olivine phenocrysts 6 7 0 4 ra is interpreted as evidence of a single mantle source despite drastic petrological changes during the volcano s history he analyses performed by crushing cogenetic pyroxene and olivine phenocrysts show a tendency to lower 3 he 4 he ratios in pyroxenes this is best explained by crystallization of pyroxenes at a depth shallower than that of olivines and or by exchange of helium trapped in pyroxenes with atmospheric or radiogenic he before eruption 87 sr 86 sr ratios of recent lavas tend to increase with time and to correlate with rb th ratios and for historical lavas these variations are tentatively attributed to shallow selective contamination from underlying sediments based on the similarity of the 3 he 4 he ratios at etna to those of european mantle xenoliths 1 we propose that the baseline geochemical signature of isotopic tracers at etna reflects the composition of the subcontinental mantle comparison to other southern italian active volcanoes etna vulcano ischia campi flegrei vesuvius shows gradual dilution of the predominantly mantle etnean end member by more radiogenic sr and he and material with higher 18o and c 3 he which is reasonably explained by the progressively important influence of subducted continental crust

anomalous diffuse co2 emission prior to the january 2002 short term unrest at san miguel volcano el salvador central america on january 16 2002 short term unrest occurred at san miguel volcano a gas and steamash plume rose a few hundred meters above the summit crater an anomalous microseismicity pattern about 75 events between 7 30 and 10 30 hours was also observed continuous monitoring of co2 efflux on the volcano started on november 24 2001 in the attempt to provide a multidisciplinary approach for its volcanic surveillance the background mean of the diffuse co2 emission is about 16 g m 2 d 1 but a 17 fold increase up to 270 g m 2 d 1 was detected on january 7 nine days before the january 2002 short term unrest at san miguel volcano these observed anomalous changes on diffuse co2 degassing could be related to either a sharp increase of co2 pressure within the volcanic hydrothermal system or degassing from an uprising fresh gas rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse co2 emission

a dynamically consistent analysis of the mesoscale eddy field at the western north pacific subarctic front 1 in this study we analyze the energetics of the quasigeostrophic qg currents observed in the course of an extensive soviet field experiment in 1987 the analyzed data span over the period of 1 month and cover the region 37 5 42 5 n 151 5 158 e at an average horizontal resolution of 35 km the processed data set includes the results of measurements at 668 hydrographic stations 118 moorings geosat sea surface height anomalies ecmwf winds and etop05 bottom topography a variational data assimilation method is employed to interpolate observations onto a regular space time grid an ensemble average over optimized ocean states is utilized to estimate posterior error bars assimilation has shown that the observed mesoscale structures are well described by qg dynamics which can explain 80 85 of the variability in the velocity and density fields the model data misfits lie within the observational error bars for all the data types used in assimilation the standard laplacian type parameterization of the small scale processes was found to be inconsistent with observations as the least model data misfits were obtained with zero diffusivity coefficients analysis of the interpolated patterns revealed a pronounced mesoscale mixing event characterized by the development of a warm streamer swirling around the upper cold core of an old anticyclonic kuroshio extension eddy the process was accompanied by a fast northwestward displacement of the eddy and induced detachment of a warm elongated vortex from its eastern rim within a week the vortex penetrated northward into the subarctic zone and eventually split into several smaller scale eddies energy analysis of the optimal solution indicates that baroclinic instability is the likely source of their energy computation of energy exchanges between depth averaged and shear components of the observed currents reveals the vertical energy cascade barotropization of the shear flow at a rate of 29 4 10 7 cm2 s 3 and the weaker kinetic energy transfer of opposite sign due to topographic interaction mean currents in the region are baroclinically unstable with an estimate of the available potential energy flux from the mean current to the eddies 53 8 10 7 cm2 s 3 potential enstrophy is transferred to mesoscale at a rate of 33 7 10 19 s 3 these figures can be considered as experimental evidence of the properties of free geostrophic turbulence which were predicted by theory and observed in numerical experiments

tectonic stresses and volcanism in situ stress measurements and neotectonic investigations in the etna area italy abstract mt etna has been building up for about 500 000 years on the eastern margin of sicily at the external border of the apenninic maghrebian mountain chain and at the crossing of several important regional fault systems the tholeiitic and alkaline magmatism of mt etna represents the northernmost manifestation of present day volcanism which was continuous in space and time from the upper miocene to the lower pleistocene in central eastern sicily in situ stress measurements and neotectonic investigations have been carried out on mt etna on its periphery and on the hyblean mountains to obtain a better understanding of the stress field which is connected to the present day activity of the volcano and a clearer picture of the regional geodynamical evolution the investigations allow a comparison of the present stress field with that acting during the quaternary the neotectonic analysis has given evidence of strong compressional stresses exerted on the pleistocene sediments overlying the substratum of the volcano and its immediate surroundings in addition to evidencing the already known extensional deformation the compressional forces were oriented approximately n s at the beginning of the volcanic activity the in situ stress measurements show now that this n s compression is today active only in the northernmost part of the etna area whereas in the remaining area extensional stresses oriented approximately wnw ese prevail it is concluded that the compressional stresses near the surface today limited to the northernmost part of the etna area had a much more widespread distribution at the beginning of the volcanic activity this conclusion is important for understanding the deep seated magmatic process focal mechanisms of earthquakes indicate a complex tectonic situation with normal faulting down to a depth of 5 km and reverse faulting at deeper levels

insights into fluid circulation across the pernicana fault mt etna italy and implications for flank instability article i nfo we conducted geophysical geochemical measurements on a 2k m n s profile cutting across the pernicana fault one of the most active tectonic features on the ne flank of mt etna the profile passes from the unstable e flank of the volcano to the south to the stable n flank and significant fluctuations in electrical resistivity self potential and soil gas emissions co2 rn and th are found the detailed multidisciplinary analysis reveals a complex interplay between the structural setting uprising hydrothermal fluids meteoric fluids percolating downwards ground permeability and surface topography in particular the recovered fluid circulation model highlights that the southern sector is heavily fractured and faulted allowing the formation of convective hydrothermal cells although the existence of a hydrothermal system in a volcanic area does not surprise these results have great implications in terms of flank dynamics at mt etna indeed the hydrothermal activity interacting with the pernicana fault activity could enhance the flank instability our approach should be further extended along the full extent of the boundary between the stable and unstable sectors of etna for a better evaluation of the geohazard in this active tectonic area

reconstructing the ocean s interior from surface data a new method is proposed for extrapolating subsurface velocity and density fields from sea surface density and sea surface height ssh in this the surface density is linked to the subsurface fields via the surface quasigeostrophic sqg formalism as proposed in several recent papers the subsurface field is augmented by the addition of the barotropic and first baroclinic modes whose amplitudes are determined by matching to the sea surface height pressure after subtracting the sqg contribution an additional constraint is that the bottom pressure anomaly vanishes the method is tested for three regions in the north atlantic using data from a high resolution numericalsimulation the decomposition yields strikinglyrealistic subsurfacefields it is particularly successful in energetic regions like the gulf stream extension and at high latitudes where the mixed layer is deep but it also works in less energetic eastern subtropics the demonstration highlights the possibility of reconstructing three dimensional oceanic flows using a combination of satellite fields for example seasurfacetemperature sst andssh andsparse orclimatological estimatesoftheregionaldepthresolveddensity themethodcouldbefurtherelaboratedtointegrateadditionalsubsurfaceinformation such as mooring measurements

length scales of eddy generation and nonlinear evolution of the seasonally modulated south pacific subtropical countercurrent the dynamical processes behind the seasonal modulation of the two dimensional eddy kinetic energy eke wavenumber spectrum in the subtropical countercurrent region of the south pacific are investigated with 14 yr of satellite altimeter data and climatological hydrographic data the authors find a seasonally modulated generation of eke via baroclinic instability in modes with larger meridional length scales subsequent nonlinear eddy eddy interactions redistribute the eke to larger total horizontal length scales and larger zonal scales in particular this is confirmed by diagnosing the spectral transfer of eke in the surface geostrophic flow which is found to drive an anisotropic inverse cascade being redirected in the sense consistent with the effect as predicted by geostrophic turbulence theory on the plane because of the seasonal renewal of meridionally elongated anomalies by baroclinic instability and possibly because of the barotropization process however the net outcome for the formation of surface zonal flows is observed to be limited

principles of electrography applied to self potential electrokinetic sources and hydrogeological applications 1 the electrical potential field passively recorded at the ground surface of the earth and termed self potential can be analyzed to determine the shape and the depth of the piezometric surface the coupling between hydraulic flow and electrical current density is electrokinetic in nature the electrokinetic coupling coefficient entering into the integral equation relating the depth of the water table to self potential signals is analyzed for various types of porous materials it is simply related to the electrical conductivity of the pore water in steady state conditions each element of the water table can be seen as an elementary dipole with an inclination locally perpendicular to the water table and strength proportional to the water table elevation then we propose three methods to obtain the shape and range of possible depths of the water table from the study of the self potential distribution recorded at the ground surface the nonuniqueness of the solution is removed if one knows either the electrokinetic coupling coefficient or the water table at one location and under the assumption of the spatial homogeneity of the electrokinetic coupling coefficient two field cases are discussed to show the success of the proposed methods for estimating the shape and depth of the water table at two different scales of investigations they concern the study of self potential signals associated with the shape of the water table in the vicinity of a pumping well and in the flank of the kilauea volcano

circum antarctic shoreward heat transport derived from an eddy and tide resolving simulation almost all heat reaching the bases of antarctica s ice shelves originates from warm circumpolar deep water in the open southern ocean this study quantifies the roles of mean and transient flows in transporting heat across almost the entire antarctic continental slope and shelf using an ocean sea ice model run at eddy and tide resolving 1 48 horizontal resolution heat transfer by transient flows is approximately attributed to eddies and tides via a decomposition into time scales shorter than and longer than 1 day respectively it is shown that eddies transfer heat across the continental slope ocean depths greater than 1 500 m but tides produce a stronger shoreward heat flux across the shelf break ocean depths between 500 m and 1 000 m however the tidal heat fluxes are approximately compensated by mean flows leaving the eddy heat flux to balance the net shoreward heat transport the eddy driven cross slope overturning circulation is too weak to account for the eddy heat flux this suggests that isopycnal eddy stirring is the principal mechanism of shoreward heat transport around antarctica though likely modulated by tides and surface forcing

continuous soil co2 and discrete plume so2 measurements at mt etna italy during 1997 2000 a contribution to volcano monitoring continuous monitoring of soil co2 dynamic concentration which is proportional to the co2 flux through the soil was carried out at a peripheral site of mt etna during the period november 1997 september 2000 using an automated station the acquired data were compared with so2 flux from the summit craters measured two to three times a week during the same period the high frequency of data acquisition with both methods allowed us to analyze in detail the time variations of both parameters anomalous high values of soil co2 dynamic concentration always preceded periods of increased flux of plume so2 and these in turn were followed by periods of summit eruptions the variations were modeled in terms of gas efflux increase due to magma ascent to shallow depth and its consequent depressurization and degassing this model is supported by data from other geophysical and volcanological parameters the rates of increase both of soil co2 dynamic concentration and of plume so2 flux are interpreted to be positively correlated both to the velocity of magma ascent within the volcano and to lava effusion rate once magma is erupted at the surface low rates of the increase were recorded before the nine month long 1999 subterminal eruption higher rates of increase were observed before the violent summit eruption of september november 1999 and the highest rates were observed during shorter and very frequent spike like anomalies that preceded the sequence of short lived but very violent summit eruptions that started in late january 2000 and continued until late june of the same year furthermore the time interval between the peaks of co2 and so2 in a single sequence of gas anomalies is likely to be controlled by magma ascent velocity

degassing of so2 and co2 at mount etna sicily as an indicator of pre eruptive ascent and shallow emplacement of magma abstract we studied soil co 2 emissions together with crater so 2 fluxes from mt etna during the period july 1997 to march 1999 this period was characterized by high levels of volcanic activity and ended with the onset of a 10 month long sub terminal eruption on february 4 1999 soil co 2 degassing was measured at two sites p39 on the lower sw flank of etna and p78 on the e flank known for being connected to deep faults that allow the escape of magmatic gas site p39 is inferred to drain gas from a deep 15 km magma reservoir whereas site p78 is connected to a shallower 5 10 km reservoir based on the temporal variations of measured soil co 2 and crater so 2 data five intervals of anomalous degassing were recognized each of them is interpreted as due to massive gas release from a magma batch that is moving toward the surface the time lag between the occurrence of degassing anomalies of co 2 and those of so 2 agrees well with the different depth of exsolution of the two gases our data also indicate a step like migration of magma to the surface which bears on the existence of at least three different temporary storage levels within etna s feeder system lastly the observed anomalies preceded by months to weeks increases in the summit activity of mt etna including the february 4 1999 eruption comparison between the amounts of degassing magma during each interval of anomalous degassing based on so 2 fluxes and erupted volumes of lava during the same periods seems to indicate that the 1999 eruption was largely fed by magma that started entering the upper feeder system of etna about 1 year earlier

structural features of the july august 2001 mount etna eruption evidence for a complex magma supply system we describe the evolution of the volcanic activity and deformation patterns observed at mount etna during the july august 2001 eruption seismicity started at 3000 m below sea level on 13 july accompanied by moderate ground swelling ground deformation culminated on 16 july with the development of a ne sw graben c 500 m wide and c 1 m deep in the cisternazza area at 2600 2500 m above sea level on the southern slope of the volcano on 17 july the eruption started at the summit of mount etna from the se crater central lateral eruptive system from which two radial c 30 m wide c 3000 m long fracture zones associated with eruptive fissures propagated both southward 17 july and northeastward 20 july on 18 july a new vent formed at 2100 m elevation at the southern base of the montagnola followed on the next day by the opening of a vent further upslope at 2550 m eccentric eruptive system the eruption lasted for 3 weeks approximately 80 of the total lava volume was erupted from the 2100 m and the 2550 m vents the collected structural data suggest that the cisternazza graben developed as a passive local response of the volcanic edifice to the ascent of a north south eccentric dyke which eventually reached the ground surface in the montagnola area 18 19 july in contrast the two narrow fracture zones radiating from the summit are interpreted as the lateral propagation from the conduit of the se crater of north south and ne sw oriented shallow dykes 2 3 m wide the evolution of the fracture pattern together with other volcanological data magma ascent and effusion rate eruptive style petrochemical characteristics of the erupted products and petrology of xenoliths within magma suggest that the eccentric and central lateral eruptions were fed by two distinct magmatic systems examples of eccentric activity accompanied by central lateral events have never been described before at etna

spectral energy fluxes in geostrophic turbulence implications for ocean energetics abstract the energy pathways in geostrophic turbulence are explored using a two layer flat bottom f plane quasigeostrophic model forced by an imposed horizontally homogenous baroclinically unstable mean flow and damped by bottom ekman friction a systematic presentation of the spectral energy fluxes the mean flow forcing and dissipation terms allows for a comprehensive understanding of the sources and sinks for baroclinic and barotropic energy as a function of length scale the key new result is a robust inverse cascade of kinetic energy for both the baroclinic mode and the upper layer this is consistent with recent observations of satellite altimeter data over the south pacific ocean the well known forward cascade of baroclinic potential and total energy was found to be very robust decomposing the spectral fluxes into contributions from different terms provided further insight the inverse baroclinic kinetic energy cascade is driven mostly by an efficient interaction between the baroclinic velo

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

tracking oceanic currents by singularity analysis of microwave sea surface temperature images in the recent years the power of employing singularity analysis of scalar variables to perform pattern recognition in complex images has been evidenced this approach is particularly useful when the image under study corresponds to a scalar variable submitted to a turbulent flow because in that case the arrangement of singularity manifolds corresponds to the multifractal hierarchy from the underlying turbulent flow in this paper we will show how this intimate connection between image processing and physics when applied to microwave sea surface temperature images allows to uncover global circulation patterns in the ocean at a daily basis with the resolution of 1 4 of degree using this technique details not evidenced in the non processed image are revealed the emerging patterns provide a description of the global oceanic currents much richer than the usual global circulation scheme in particular instabilities eddy generation and filamentation are distinctly identified a pattern extraction of this kind is useful in order to measure and track mesoscale oceanic phenomena opening the way to many operational and reanalysis applications

ssh wavenumber spectra in the north pacific from a high resolution realistic simulation abstractfollowing recent studies based on altimetric data this paper analyses the spectral characteristics of the sea surface height ssh using a new realistic simulation of the north pacific ocean with high resolution in the horizontal and 100 vertical levels this simulation resolves smaller scales down to 10 km than altimetric data limited to 70 km because of the noise level in high eddy kinetic energy eke regions as in the western part ssh spectral slope almost follows a k 4 with k the wavenumber or slightly steeper law in agreement with altimeter studies the new result is that unlike altimeter studies such a k 4 slope is also observed in low eke regions as in the eastern part in these regions this slope mostly concerns scales not well resolved by altimetric data such k 4 ssh spectral slopes are weaker from what is expected from quasigeostrophic turbulence theory but closer to surface quasigeostrophic sqg turbulence theory the consequence is that the small scales concerned

the vorticity balance of the ocean surface in hawaii from a regional reanalysis abstractthe ocean surface vorticity budget around the hawaiian islands is examined using an 18 month model reanalysis generated using four dimensional variational state estimation with all available observations satellite in situ and high frequency radio to better resolve the ocean surface currents and reduce the representation error of the radio measured surface currents this study developed a new vertical scheme for the regional ocean modeling system a new detailed description of the ocean surface vorticity is created revealing a region dominated by cyclonic anticyclonic vorticity to the north south of the mean position of the hawaii lee countercurrent advection of vorticity is the primary process that transports the vorticity generated in the lee of the islands by the wind wake in this island lee the zonal wavenumber spectra show a cascade of vorticity energy from the submesoscale toward the larger scales latitudinal differences in the advection of vorticity spectra indicate the propag

do altimeter wavenumber spectra agree with the interior or surface quasigeostrophic theory in high eddy energy regions it is generally assumed that sea level wavenumber spectra compare well with quasigeostrophic qg turbulence models and that spectral slopes are close to the expected k 5 law this issue is revisited here sea level wavenumber spectra in the gulf stream kuroshio and agulhas regions are estimated using the most recent altimeter datasets the ocean topography experiment topex poseidon jason 1 the environmental satellite envisat and the geosat follow on the authors show that spectral slopes in the mesoscale band are significantly different from a k 5 law in disagreement with the qg turbulence theory however they very closely follow a k 11 3 slope which indicates that the surface quasigeostrophic theory sqg is a much better dynamical framework than the qg turbulence theory to describe the ocean surface dynamics because of the specific properties of the sqg theory these results offer new perspectives for the analysis and interpretation of satellite data

on the catalytic role of high baroclinic modes in eddy driven large scale circulations abstract this paper investigates the tridimensional consistency of the resolution of eddy scales in simulating large scale flows the generation of classical wind forced eddy driven double gyre circulation is investigated with a multilayered quasi geostrophic model six layers on the vertical have been chosen to assure the convergence of the baroclinic instability emphasis is on the resolution of the high baroclinic modes and its effects on the dynamics of the midlatitude jet several eddy resolving experiments identical except for the horizontal resolution which can be low 20 km or high 10 km are compared in every experiment the scales associated with the first and second baroclinic modes are well resolved but those associated with the third and higher baroclinic modes are so only in 10 km experiments for a better illustration of the importance of the high vertical modes three layer experiments having configurations equivalent to that of the six layer experiments have been conducted note th

effects of bottom friction on nonlinear equilibration of an oceanic baroclinic jet abstract bottom friction is an important sink of energy in the ocean indeed high resolution ocean models need bottom friction to achieve a satisfactory kinetic energy level at equilibrium however bottom friction has also subtle and discriminating effects on the different energy transfers and therefore on the 3d structure of the flow some of which have to be clarified in this study those effects on an unstable baroclinic jet are reexamined using a primitive equation model as in previous studies using quasigeostrophic models it was found that bottom friction strongly affects the barotropic mode whereas the baroclinic modes are weakly changed the new result is that bottom friction yields a significant space scale selection analysis of the dynamics reveals strong agreement with previous quasigeostrophic studies at the mesoscale in the interior but differences in the eddy field at small scales close to the surface a rationalization of these results is proposed by a comparison with preceding atmosph

vertical structure of midlatitude mesoscale instabilities abstract instability processes in frontal jet regions outside the western boundary currents are examined for their ability to produce mesoscale variability comparable to that observed in the open ocean the important of sufficient numerical resolution for a correct modeling of these processes is considered using a local plane quasi geostrophic multilevel model with periodic horizontal boundary conditions the combined effects of special density and current profiles typical for the midlatitude eastern north atlantic are studied the linearized approach yields a set of vertical shear modes with different vertical structure depending on the zonal wavelength of the perturbation some of these shear modes are unstable the mesoscale range 50 500 km reveals two different types a surface intensified shear mode and a deep sea intensified one the growth rates of the former are usually largely exceeding those of the latter due to the larger velocities and shears their exponential amplification time scale ra

reconstruction of ocean s interior from observed sea surface information observational surface data are used to reconstruct the ocean s interior through the interior surface quasigeostrophic isqg method the input data include the satellite derived sea surface height satellite derived sea surface temperature satellite derived or argo based sea surface salinity and an estimated stratification of the region the results show that the isqg retrieval of subsurface density anomalies is quite promising compared to argo profile data at 1000 m depth the directions of retrieved velocity anomalies are comparable to those derived from argo float trajectories the reconstruction using surface density input field approximated only by sst with constant sss performs less satisfactorily than that taking into account the contribution of sss perturbations suggesting that the observed sss information is important for the application of the isqg method better reconstruction is obtained in the warm season than in the cold season which is probably due to the stronger stratification in the warm season that confines the influence of the biases in the surface input data especially sss in a shallow layer the comparison between the performance of isqg with argo based sss input and that with satellite derived sss input suggests that the biases in the sss products could be a major factor that influences the isqg performance with reduced biases in satellite derived sss in the future the measurement based isqg method is expected to achieve better reconstruction of ocean interior and thus is promising in practical application

the detection of concealed faults in the ofanto basin using the correlation between soil gas fracture surveys abstract an integrated geochemical morphological and structural analysis was applied to a basin filled with clayey sediments in southern italy ofanto valley to delineate tectonic features more than 100 soil gas samples were collected and analysed for co2 rn and he and the resulting distribution was compared with the location and orientation of field observed brittle deformations faults and fractures and air photo interpreted morphotectonic features the results show that the highest helium radon and co2 values occur preferentially along elongated zones similar to the most representative trends obtained by geomorphological and mesostructural analyses i e anti apennine apennine and secondarily n s orientations furthermore the development of geostatistical techniques has allowed the semi quantitative evaluation of the anisotropic soil gas distribution the gas distribution pattern is considered to result from the combination of the anisotropic distribution of fracture traces and the randomly distributed background field the correspondence between soil gas distribution and geomorphological mesostructural features as well as the results from the geostatistical analysis suggest that gas leakage towards the surface is controlled by the same structural pattern which also created some morphological features this technique has been shown to be a useful tool for neotectonic studies this is especially true in basins filled with clayey sediments as soil gas is even able to define the leakage of deep seated gases along tectonic discontinuities which have no surface expression

dynamics of the upper oceanic layers in terms of surface quasigeostrophy theory in this study the relation between the interior and the surface dynamics for nonlinear baroclinically unstable flows is examined using the concepts of potential vorticity first it is demonstrated that baroclinic unstable flows present the property that the potential vorticity mesoscale and submesoscale anomalies in the ocean interior are strongly correlated to the surface density anomalies then using the invertibility of potential vorticity the dynamics are decomposed in terms of a solution forced by the three dimensional 3d potential vorticity and a solution forced by the surface boundary condition in density it is found that in the upper oceanic layers the balanced flow induced only by potential vorticity is strongly anticorrelated with that induced only by the surface density with a dominance of the latter the major consequence is that the 3d balanced motions can be determined from only the surface density and the characteristics of the basin scale stratification by solving an elliptic equation these properties allow for the possibility to reconstruct the 3d balanced velocity field of the upper layers from just the knowledge of the surface density by using a simpler model that is an effective surface quasigeostrophic model all these results are validated through the examination of a primitive equation simulation reproducing the dynamics of the antarctic circumpolar current

streaming potential in volcanic rocks from mount pelee streaming potential and electric conductivity have been measured in a laboratory on 11 consolidated samples coming from five deposits of the different evolutionary stages of mount pelde volcano the streaming potential coupling coefficient ranges from 35 to 4905 mv mpa 1 and increases with increasing permeability this increase is mainly due to the dependency of rock effective conductivity with permeability the permeability of the samples varies from 0 146x10 12 to 34x10 12 m 2 the zeta potential at ph 7 and water conductivity of 2 1x10 4 s m l is relatively small for the majority of the samples it ranges from 4 to 19 rev according to water conductivity analysis on mount pel e streaming potential coupling coetficients of 25 to 406 mv mpa 1 can be expected for this volcano

global variability of the wavenumber spectrum of oceanic mesoscale turbulence abstractthe wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence near the edge of the core regions of high eddy energy agreement is observed with the prediction of the surface quasigeostrophic sqg turbulence theory which has fundamental differences from that of the traditional quasigeostrophic qg turbulence theory in the core regions of high eddy energy the spectra are consistent with frontogenesis that is not fully accounted for by the sqg theory however the observations in the vast ocean interior of low eddy energy exhibit substantial differences from the predictions of existing theories of oceanic mesoscale turbulence the spectra in these regions may reflect the ocean s response to short scale atmospheric forcing and air sea interaction the observations presented in this paper serve as a test bed for new theories and ocean general circulation models

the production and dissipation of compensated thermohaline variance by mesoscale stirring abstract temperature salinity profiles from the region studied in the north atlantic tracer release experiment natre show large isopycnal excursions at depths just below the thermocline it is proposed here that these thermohaline filaments result from the mesoscale stirring of large scale temperature and salinity gradients by geostrophic turbulence resulting in a direct cascade of thermohaline variance to small scales this hypothesis is investigated as follows measurements from natre are used to generate mean temperature salinity and shear profiles the mean stratification and shear are used as the background state in a high resolution horizontally homogeneous quasigeostrophic model the mean state is baroclinically unstable and the model produces a vigorous eddy field temperature and salinity are stirred laterally in each density layer by the geostrophic velocity and vertical advection is by the ageostrophic velocity the simulated temperature salinity diagram exhibits fluctuations at depths ju

the prevalence of oceanic surface modes satellite observations have revolutionized oceanography capturing diverse phenomena over much of the globe however it remains to understand how surface fields like sea surface height reflect the motion occurring at depth the vertical structure of ocean eddies is often expressed in terms of baroclinic modes which are basis functions derived assuming a flat ocean bottom bathymetry alters the modes though weakening the bottom velocities using analytical solutions we demonstrate that with realistic bathymetry and or bottom friction the bottom velocities are nearly zero the resulting surface modes should be ubiquitous in the ocean this would explain the dominant mode of variability obtained from globally distributed current meter data and is consistent with energy spectra derived from sea surface height data the results yield a simple way to infer subsurface velocities from satellite data and suggest that ocean analyses should be made in terms of surface modes and topographic waves

observations of intermittent deep currents and eddies in the gulf of mexico 1 intense currents having speeds between 10 and 40 cm s 1from 1000 m below the surface to the bottom have been measured in the loop current lc region and in the western gulf of mexico wgm the observations come from moored current meters sampling from the near surface to the bottom at 3300 3500 m and from august 2008 to august 2010 ten intermittent intensified currents are documented these events last 10 to 30 days and take place in the region just between the surface intensified anticyclonic cyclonic features as deduced from altimetry and measured currents in the wgm they occur between the cores of anticyclone cyclone pairs in the eastern gulf of mexico egm they occur in the loop current edge between its anticyclonic circulation and a neighboring cyclone during each event the analysis shows an increase in the barotropic contribution to the current in the loop current region these events are often associated with intensification of cyclonic vorticity in the deep layer