historical evolution and extreme climate events during the last 400years on the rhone prodelta nw mediterranean abstract the rhone river is the most important source of freshwater and sediment to the western mediterranean sea deltaic lobes and littoral prisms compose the sedimentary units that make up the whole rhone subaqueous delta which reaches up to 50 m in thickness individual lobes that accompanied the retreat of the rhone during sea level rise and the subsequent westward then eastward shift of the main outlet display averaged sedimentation rates in excess of 1 cm yr 1 containing both continental and marine material during the industrial period most of the river flow was delivered through the pegoulier and roustan distributary channels which evolved under human influence within the prodeltas associated to these distributaries very expanded sedimentation rates 10 cm yr 1 allow the documentation of historical extreme climate events a 7 71 m long piston core rhs ks57 was retrieved from the distal prodelta 79 m water depth a multi proxy study was carried out using microfossil assemblages ostracods benthic foraminifera and coccoliths in combination with sedimentological and geochemical proxies our results show that 1 four different intervals i iv spanning a time range comprised between 1600 ad and present day have been differentiated from this multi proxy analysis they correspond to a different position of distributary channels each interval correlates with the different phases of channel avulsion induced by climate events or by human activity 2 the signature of extreme floods that can be identified by the punctuated occurrence of freshwater continental ostracods e g candona spp ilyocypris sp correlating with increases in grain size and or organic carbon content they correspond to decadal scale increased runoffs reported in historical archives our study demonstrates the relevance of benthic microfossil studies for reconstructing paleoenvironmental changes in transitional marine continental settings

spatial distribution of live benthic foraminifera in the rhone prodelta faunal response to a continental marine organic matter gradient abstract benthic foraminifera were collected in the rhone prodelta gulf of lions mediterranean sea an enriched zone with high organic matter content in june 2005 sediment cores were sampled at depths ranging from 20 to 100 m four distinct foraminiferal assemblages were determined in the study area reflecting the geographical distribution of the impact of river supply the living foraminiferal faunas present a typical picture with strongly impoverished faunas composed exclusively of stress tolerant taxa fursenkoina fusiformis bulimina aculeata leptohyalis scottii and adelosina longirostra in the immediate vicinity of the river mouth this assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment to the southwest under the main corridor followed by the river plume high organic input with a dominantly terrestrial signature more refractory may be stressful for many taxa which need organic matter of a more labile quality in this area nonion scaphum nonionella turgida and rectuvigerina phlegeri are present in low densities on the edge of this area these taxa show much higher densities a greater proportion of marine organic carbon could explain their increasing abundances in this area towards the east and towards the deepest stations in the outer part of the enriched zone biodiversity increases faunas at these stations have intermediate densities and contain a number of taxa cassidulina carinata epistominella vitrea valvulineria bradyana nonionella iridea bradyi at the deepest stations bolivina dilatata spathulata and textularia porrecta at the eastern stations that seem to benefit from more marine organic matter the comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the rhone prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment water interface since bottom waters are well oxygenated 215 260 mol l and oxygen penetration into the sediment is less than 1 cm at all stations benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution

sources and exchanges of mercury in the waters of the northwestern mediterranean margin abstract ocean margins are focal regions in terms of mercury hg exchanges between the continent and the open sea the aim of this paper is to describe the distribution and partition of hg between the gaseous dissolved and particulate phases in the waters of the northwestern mediterranean nwm margin in order to assess the hg sources and exchanges within the continuum between the continental shelf gulf of lions and the open sea northern gyre mean standard deviation of total hg species hgt concentrations in unfiltered water samples were 1 52 1 00 pmol l 1 n 36 in the inner shelf 1 09 0 15 pmol l 1 n 30 along the slope and 1 10 0 13 pmol l 1 n 99 in the northern gyre the dissolved phase the hg from the open sea water is the largest hg input to the gulf of lions 5 7 kmol yr 1 whereas inputs from the riverine source account for 3 4 kmol yr 1 and atmospheric deposition for less than 0 5 kmol yr 1 the hg accumulated in the sediments of the shelf is 4 5 kmol yr 1 including 0 6 1 7 kmol yr 1 in the rhone prodelta sediments the evasion to the atmosphere represents a hg flux of 2 6 kmol yr 1

origin and pathways of winter intermediate water in the northwestern mediterranean sea using observations and numerical simulation received 25 june 2013 revised 31 october 2013 accepted 6 november 2013 published 6 december 2013 1 the study of water masses worldwide their formation spreading mixing and impact on general circulation is essential for a better understanding of the ocean circulation and variability in this paper the formation and main pathways of winter intermediate water wiw in the northwestern mediterranean sea nwmed are investigated during the winter spring 2011 using observations and numerical simulation the main results show that the wiw formed along the continental shelves of the gulf of lion and balearic sea circulates southward following five preferential pathways depending on the wiw formation site location and the oceanic conditions wiw joins the northeastern part of the balearic sea or flows along the continental shelves until joining the balearic current maximum of 0 33 sv in early april or further south until the ibiza channel entrance two additional trajectories contributing to water mass exchanges with the southern part of the western mediterranean sea bring the wiw through the ibiza and mallorca channels maxima of 0 26 sv in late march and 0 1 sv in early april respectively the circulation of wiw over the nwmed at 50 200 m depth its mixing and spreading over the western mediterranean sea reaching the south of the balearic islands the algero provencal basin the ligurian and the alboran seas suggest that the wiw may have an impact on the ocean circulation by eddy blocking effect exchange of water masses between north and south subbasins of western mediterranean sea through the ibiza channel or modification of the ocean stratification

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

tectonostratigraphic evolution of the eastern algerian margin and basin from seismic data and onshore offshore correlation abstract the eastern algerian basin part of the western mediterranean domain is a back arc basin resulting from the se drift of the lesser kabylia block gave rise to continental extension and birth of a new oceanic domain we aim here to define the structure and tectonostratigraphic evolution of this basin and the adjoining continental margin indeed the absence of wells and the lack of published mcs data kept this area mostly unknown the crustal architecture down to the moho and seismo stratigraphy of the sedimentary infill are detailed emphasizing particularly the pre messinian series by combining a new set of offshore deep penetrating seismic conventional mcs sections and wide angle seismic data because no well exist offshore we realized new field descriptions of the late oligocene and miocene deposits on land and propose onshore offshore extrapolation and age correlations the pre messinian series display four main units pmsu1 to 4 above which messinian units are consistent with stratigraphic models already proposed for the mediterranean basin the deep basin displays units as old as the omk oligo miocene kabyle series on land the basement is shaped by conjugate transcurrent faults striking n120 n40 forming a series of rhombic troughs resulting from transtensional tectonics the coeval e w extension and nw se stretching of the continental crust suggest a radial opening of the algerian basin during late oligocene lower miocene followed by a progressive uplift of the upper margin after the collision of lesser kabylia with africa besides steep slope of the eastern algerian margin downward flexure of the oceanic basin near the margin toe and growth of s dipping thrusts within the margin evidence a significant quaternary stress inversion overall this study highlights the complex stress evolution of the east algerian margin since oligocene times as evidenced by significant upward downward vertical motions and crustal extensional compressional successions we summarize this evolution into three main stages 1 rifting including sea floor spreading at late oligocene burdigalian in the context of back arc 2 collision between alkapeca blocks and africa at 17 ma and post rift sag basin infill till late tortonian to messinian and 3 inversion of the margin and development of flexural basins at quaternary times

sediment dynamics during wet and dry storm events on the tet inner shelf sw gulf of lions abstract the importance of short term processes such as floods and storms on sediment delivery and reworking on the tet inner shelf was investigated the tet inner shelf is a small event dominated system located in the south western part of the gulf of lions the expected sedimentary scenario in this environment is that fluvial sediment should be deposited on the prodelta and later dispersed around the shelf and slope by wave and current reworking during storms this paper investigates differences in inner shelf sediment dynamics between storm events occurring during usual river discharges and those occurring during river floods waves current velocities near bottom water turbidity bottom sediment grain size and sea floor erosion accretion were concurrently measured at 28 m water depth on the tet inner shelf from november 2003 to march 2004 two major storms took place on 4 december 2003 and 21 february 2004 and two moderate storms occurred on 8 december 2003 and 14 march 2004 the two major storms displayed similar wave characteristics maximum significant wave height h s 7 m peak period t p 12 s and wave direction around 90 the main environmental differences during the two major storm events correspond to the amount of sediment discharged from the tet river about 2 10 4 t of sediment was delivered by the river during the 4 december flood wet storm and less than 5 10 2 t during the 21 february storm dry storm sediment dynamics were quite similar during the storm events resuspension caused by waves and sediment advection towards the southeast due to near bottom shelf currents were the dominant sedimentary processes the result was a bottom sediment erosion of several centimetres at the study site during both the wet and dry events the main differences between the wet and dry events arose after the storm immediately after the peak of the wet storm sediment supplied by the tet river and probably from other rivers was deposited around the river mouth a few days later during a moderate storm this unconsolidated sediment was resuspended transported offshore and deposited on the inner shelf in contrast a moderate storm which occurred some days after the dry february storm caused bottom erosion on the inner shelf because no fresh sediment was available on the shallower area the results from this study indicate that the tet inner shelf at 28 m water depth is mainly a bypass zone for sediment that is transported s se towards the middle outer shelf and slope although ephemeral sediment deposits may be favoured by the sediment supplied from flood events sediment transport across the shelf from the river to the slope follows a complex multi step pattern that needs to be addressed using a multi event approach

origin and dynamics of mesoscale eddies in the catalan sea nw mediterranean insight from a numerical model study past observations and satellite sea surface temperature imagery indicate the presence of mesoscale anticyclonic eddies drifting along the catalan coast in september 2001 one of these anticyclonic eddies was surveyed over the shelf break during an oceanographic cruise which permitted the 3 d description of its structure in this work we investigate the origin and dynamics of such catalan eddies using a numerical circulation model of the northwest mediterranean at 3 km resolution driven by high resolution atmospheric analyses and compare model eddies with the observations in the catalan sea we identify two zones of eddy formation in the gulf of lions in front of the city of marseille and at the southeast of coast of roussillon from which anticyclonic eddies are observed to drift toward the catalan sea the hydrology and dynamics of the structures observed in the simulations are characterized sensitivity experiments and energy analysis are performed which allow us to identify the mechanisms associated with their generation properties of the eddy observed during the 2001 cruise at the catalan shelf break are found to compare well with model eddies generated at the southeast of the roussillon coast the model relates the origin of these eddies to the separation of the coastal current downstream from creus cape flow separation is linked to intense downwelling taking place in front of the roussillon coast when strong northwesterly winds events occur

physical characteristics and dynamics of the coastal latex09 eddy derived from in situ data and numerical modeling 1 we investigate the dynamics of a coastal anticyclonic eddy in the western part of the gulf of lion gol in the northwestern mediterranean sea during the latex campaign in the summer 2009 latex09 the sampling strategy combines sea surface temperature satellite imagery hull mounted acoustic doppler current profiler data conductivity temperature depth casts and drifter trajectories our measurements reveal an anticyclonic eddy latex09 eddy with a diameter of 23 km and maximum depth of 31 m centered at 3 34 e 42 33 n we use a high resolution three dimensional primitive equation numerical model to investigate its generation process and evolution the model is able to reproduce the observed eddy in particular its size and position the model results suggest that the latex09 eddy is induced by a large anticyclonic circulation in the northwestern part of the gol pushed and squeezed toward the coast by a meander of the northern current this represents a new generation mechanism that has not been reported before the post generation dynamics of the eddy is also captured by the model the collision of the latex09 eddy with cape creus results in a transient structure which is depicted by the trajectories of two lagrangian drifters during latex09 the transient structure and its advection lead to a transfer of mass and vorticity from the gol to the catalan shelf indicating the importance of mesoscale structures in modulating such exchanges in the region

mathematical geophysics a survey of recent developments in seismology and geodynamics n j vlaar g nolet m j r wortel s a p l cloetingh editors reidel dordrecht 1988 xi 407 pp dfl 120 00 49 00 37 35 hardback

modeling the deep convection in the northwestern mediterranean sea using an eddy permitting and an eddy resolving model case study of winter 1986 1987 1 in the northwestern mediterranean sea winter 1986 1987 was particularly cold inducing a strong open ocean convection event in order to investigate the impact of numerical models spatial resolution on the convection representation and the effects of deep convection on the northwestern mediterranean circulation we perform two numerical three dimensional simulations eddy permitting versus eddy resolving models are forced at the surface by the era40 atmospheric fluxes with a simple heat flux correction to better mimic the observed value we examine the characteristics of the deep convection mixed layer water masses characteristics convection zone and mesoscale structures and perform temporal analysis of this event in terms of kinetic energy buoyancy equilibrium and deep water dw evolution the convection characteristics are similarly represented on a global scale by both models and are in good agreement with observations except for the size of the convection region however the eddy resolving model better reproduces the mesoscale structures whose role in the dw formation mixing and transport is shown to be essential the boundary circulation and the overturning are enhanced during the convection event sixty six percent of the dw spreading is due to the bleeding effect into the catalan sea during the convection event whereas 33 is due to the mesoscale structures southwestward advection after the event sixty percent of the restratification with respect of the water column initial structure occurs before july 1987 and is due to light water advection afterward restratification is due to the mixing and is not complete before next year convection

a sensitivity study of the general circulation of the western mediterranean sea part ii the response to atmospheric forcing abstract this paper investigates the influence of sea surface thermohaline fluxes and wind stress on the circulation of the western mediterranean sea using a high resolution 3d primitive equation model an 18 year experiment was forced with the daily output of a fine grid mesh numerical weather prediction model the major characteristics of the circulation are well reproduced the basin surface circulation is cyclonic over all of the basin the two anticyclonic alboran gyres are present the instabilities of the algerian current generate large anticyclonic eddies that invade the whole algerian basin the liguro provencal catalan current is well marked deep water convection down to the bottom only occurs during the first 3 years then winter intermediate water is produced the north south gradient of the atmospheric thermohaline fluxes induces a northward surface transport of water from the algerian basin into the liguro provencal basin this pattern can be associated with the balearic front sensitivity

on the nature of near inertial oscillations in the uppermost part of the ocean and a possible route toward hf radar probing of stratification abstractinertial band response of the upper ocean to changing wind is studied both theoretically and by analysis of observations in the northwestern mediterranean on the nontraditional f plane because of the horizontal component of the earth s rotation for waves of inertial band with frequencies slightly below the local inertial frequency f there is a waveguide in the mixed layer confined from below by the pycnocline it is argued that when the stratification is shallow these waves are most easily and strongly excited by varying winds as near inertial oscillations nios these motions have been overlooked in previous studies because they are absent under the traditional approximation the observations that employed buoys with thermistors adcps and two 16 3 mhz wellen radar wera hf radars were carried out in the gulf of lion in april june 2006 the observations support the theoretical picture a pronounced inertial band response occurs only in the presence of shallow stratification and is confined

last millennia sedimentary record on a micro tidal low accumulation prodelta tet nw mediterranean statistical sequential analysis was performed on a series of sediment cores collected from the tet prodelta in the gulf of lions northwestern mediterranean sea between october 2003 and october 2004 seabed changes during that period were correlated to hydrodynamic conditions waves and currents and river discharge low sediment supply prevents full preservation of new sediment strata on this low accumulation prodelta located on a microtidal storm dominated inner shelf severe meteorological events caused a rapid succession of erosion and deposition phases for example the december 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and or bioturbation until a new storm event eroded this layer a typical sedimentary sequence was observed for the secular deposits composed of a 10 cm thick sandy layer overlaying siltyclayey layers these characteristic features were used to analyse the last millennia sedimentary record of the tet prodelta the low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions no flood layer was found related to catastrophic flooding of the last century in the sedimentary record the little ice age 1550 1850 ad probably favoured the formation of a well developed muddy prodelta in the mouth of the tet river later on the decrease of sediment supply by rivers due to climate change and or human activities damming irrigation and the increase of the number of high energy storms reaching the coast induced a coarsening of the top sediment layer on this prodelta this modern change of the substrate is also observed in the composition of benthic biota found in the substrate

the rhone river plume in unsteady conditions numerical and experimental results surface current maps obtained in the plume of the rhome river by two vhf radars gave rise to comparisons with simulations produced by a primitive equation model two situations were investigated one in steady conditions the other with a variable wind the model gives a good estimation of current direction and velocity not only in the plume itself but also in the surrounding water the model reveals the mechanisms involved in the plume dilution and more generally in the renewal of surface water near the coast when the wind changes direction the sensitivity of the model results to the upper boundary condition for turbulent kinetic energy is also shown

nutrients and plankton spatial distributions induced by a coastal eddy in the gulf of lion insights from a numerical model a plankton functional types model forced by a hydrodynamic model is used in the present work to study the impacts of a coastal eddy on the distribution of nutrients and plankton in the western part of gulf of lion nw mediterranean sea this study based on a realistic simulation of the year 2001 focuses on a long life anticyclonic eddy detected during summer the studied anticyclonic eddy has some biogeochemical characteristics of those observed in the open ocean as for example the low productivity at their core and rising up of nutricline on their edges however the functioning and consequences of such coastal eddy on nutrients and plankton distributions are complicated by potential interactions with topography wind induced upwelling along the languedoc coast and nearby northern current nc especially the proximity of the southern edge of the eddy with the nc makes possible the exchanges of organic matter plankton at times during the eddy s life the coastal eddy thus transports organic matter from the coastal zone to the offshore domain the coupled model also suggests the importance of offshore to coastal transport by nc through a seeding process of the eddy in plankton at the beginning of its life a detailed biogeochemical functioning of the studied eddy all along its lifetime is proposed from the model results at the beginning the eddy mainly acts as a transporter of the plankton wind induced bloom occurring along the languedoc coast several days before the eddy set up at the same time the eddy shows upwards vertical velocities on its edges creating upwelling of nutrient enriched waters the process of eddy induced upwelling is notably enhanced on the eddy western side along the roussillon coast due to the shelf topography the around eddy advection and relative lower temperatures prevent the large development of phytoplankton along the roussillon coast and the eddy induced bloom is predicted to occur near the northwestern side of the eddy the eddy induced and wind induced blooms of phytoplankton then merge on the eastern side by advection and this process of aggregation may explain the persistent occurrence of a filament of high chlorophyll observed on the offshore edge of the eddy throughout the study period the changes in plankton composition due to a combination of top down and bottom up processes during the coast to offshore transport may explain the disappearance of the filament south of 43 n at the surface

application of geoelectric methods using buried electrodes in exploration and mining1 various geoelectric methods which have been developed and applied in the last 10 20 years in elgi are discussed these methods which use buried electrodes are hole to surface gradient mapping to detect bauxite deposits in sinkholes below a resistive screening layer in mine gradient profiling to map the basement topography below galleries and the hole to surface version of geoelectric layer tracing to find outcrops of mineralized zones penetrated by drillings data processing procedures have been developed on the basis of common concepts and hypotheses to link theoretical models with geological structures the objects investigated are determined as the difference between the theoretical models and geological structures the predominant part of the real electric field measured above the geological structures is the theoretical field related to the theoretical model the effects of the objects the anomaly are superposed on the theoretical field but their extent is small compared with the values of the latter the theoretical field and the anomaly depend strongly on the separation from the sources for this reason the anomalies are difficult to recognize therefore the ratio of the theoretical field to the measured one is computed since a the apparent specific conductivity is proportional to this ratio it is demonstrated that since the changes in the a curve depending on the location of the observation point are small the anomalies can easily be recognized on the curve the a curve computed in the above way reflects the objects better than the originally measured electric fields examples illustrate the solution of the above mentioned geological problems by the practical application of adequate geoelectric methods using buried electrodes

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

suspended sediment fluxes and transport processes in the gulf of lions submarine canyons the role of storms and dense water cascading contemporary suspended sediment transport was studied in seven submarine canyons of the gulf of lions gol current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from november 2003 to may 2004 sediment transport events were monitored and studied in relation to forcing conditions there was a large flood in early december during which discharges from all of the coastal rivers increased by more than one order of magnitude a smaller flood of the rhone river occurred later in mid january followed by a persistent high river discharge that lasted until mid february there were also several e se storm events during the measurement period two of them causing large swell one in early december max hs 8 4 m coinciding with the major river flood andoneinlatefebruary maxhs 7m duringaperiodoflowerriverdischarge mostofthevariabilityindown canyoncurrentspeeds waslinkedtostrongdownwellinginducedbye sestormsandtocascadingofdenseshelfwaterinducedbynandnwwinds theintensity and timing of these processes strongly varied spatially eastern storms generated higher waves and induced stronger downwelling in the western than in the eastern sector of the gol shelf dense water cascading events were enhanced during eastern storms and they were also more intense in the western sector of the gol these events occurred frequently from january to may along the western canyons and from february to april along the eastern canyons from february to april they occurred simultaneously in all the canyons sediment transport was mainly down canyon and mostly concentrated during storm induced downwelling and dense water cascading events during the high river discharge season most of the newly supplied and resuspended sediment remained stored on theshelf however duringthelatefebruarystormandcascadingevent thestoredsedimentwasquicklyresuspendedandtransported mainly through the westernmost submarine canyon cap de creus following a flushing pattern later although minor storms and shelfdensewatercascadinghardlyincreasedsuspendedsedimentconcentrationswithinthecanyons theyinducedstrongnear bottom current velocities increasing down canyon sediment fluxes and generating small but significant sediment transport events most of the shelf canyon transfer took place during the late february storm and cascading event through the cap de creus canyon where the net suspended sediment flux was between one and two orders of magnitude higher than in the other canyons

sea surface transport in the western mediterranean sea a lagrangian perspective 2 we study the sea surface transport in the western mediterranean sea from a lagrangian point of view in particular the alboran and the north western subbasins the study is carried out through the analysis of 3 years of surface velocity model data through finite size lyapunov exponents residence time and virtual particle trajectories complementing the classical eulerian approach the spatiotemporal variability of the main transport processes is inferred from the empirical orthogonal function modes of the lyapunov exponents being the most relevant modes discussed and physically interpreted results indicate that some of the variability in the surface transport patterns in the western mediterranean can be explained by specific modes which provide an indication of connectivity among subbasins like the inflow of atlantic waters through the ibiza channel

numerical high resolution air sea coupling over the gulf of lions during two tramontane mistral events 1 the near sea surface meteorological conditions associated with strong wind events over the mediterranean sea constitute a strong forcing on the ocean mixed layer the present study addresses the question of the sea surface scheme used in high resolution and short range atmospheric numerical modeling to represent the ocean mixed layer response under these severe mistral wind events in the gulf of lions area several slab ocean models have been used coupled with the weather research and forecasting wrf model and applied on two mistral cases 1 a slab model based on the transport divergence equation where the mixed layer evolution is only driven by the wind stress 2 a slab model where the temperature is the only prognostic variable and evolves according to the net surface heat flux and 3 a complete slab scheme from price 1981 the coupled simulations are also compared to two basic simulations one using a constant sea surface temperature sst field during all of the model integration and another using a 6 hourly update sea surface temperature reanalysis in this study we mainly focus on the slab model performances we identify the processes involved in the ocean mixed layer response under strong wind situations i e local and fast cooling and deepening the feedbacks of an interactive ocean mixed layer on the atmospheric simulation are also investigated

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

the fate of river organic carbon in coastal areas a study in the rhone river delta using multiple isotopic delta c 13 delta c 14 and organic tracers a significant fraction of the global carbon flux to the ocean occurs in river dominated ocean margins riomar although large uncertainties remain in the cycle of organic matter om in these syste

observation and modeling of the winter coastal oceanic circulation in the gulf of lion under wind conditions influenced by the continental orography fetch experiment 1 hydrological and currentmeter observations were collected on the continental shelf and slope of the gulf of lion during the fetch experiment 13 march to 15 april 1998 results from the first part of the cruise characterized by strong northern winds are presented the hydrological structures evidence well mixed water masses on the eastern and western ends of the shelf in the central part the situation is more complex with the influence of the rhone river s freshwater plume in the first 40 m of the water column and closer from the bottom with the confrontation of downwelled coastal cold water and upwelled warmer and saltier slope water current measurements show the path of the cyclonic circulation along the slope which is part of the general circulation of the western mediterranean and suggest the presence of large and temporary eddies on the shelf this oceanic circulation is simulated with a free surface three dimensional model using realistic forcing the model outputs are in agreement with the main hydrological and circulation patterns the results further indicate that coastal eddies are generated by the mesoscale structure of the wind field

a numerical study of the effects of coastline geometry on wind induced upwelling in the gulf of lions an attempt is made to explain the fixed locations of coastal upwelling centers in the gulf of lions as a function of the coastline geometry alone the semi implicit numerical model based on two layer shallow water equations uses a spatial discretization with triangular finite elements vertical mixing is shown to play an important role in determining the final shape of the upwelling centers it is conjectured that an observed upwelling filament results from the straining and stretching of a coastal upwelling center by the observed anticyclonic circulation farther offshore

observing global ocean topostrophy 1 recent publications have evaluated topostrophy f v d where is f coriolis v is velocity and d is gradient of total depth as a means of comparing models circulations some results are striking comparing four global models two with modest grid size and two with fine grids merryfield and scott 2007 show that finer grid models are characterized by more positive especially at greater depths and higher latitudes among nine arctic ocean models holloway et al 2007 find in three of the models quite distinct from the other six a result shown to depend upon subgrid eddy parameterization from different choices of numerical method within the same model penduff et al 2007 show that improved numerical representations support more positive can these model results be compared with observations a global compilation has been prepared from 17120 current meter records spanning 83087 current meter months the compilation tends to confirm modeling progress achieved by finer resolution improved parameterizations and better representations a new characterization of global ocean circulation emerges with suggestive dynamical insights

the fetch experiment an overview the flux etat de la mer et teledetection en conditions de fetch variable fetch was aimed at studying the physical processes associated with air sea exchanges and mesoscale oceanic circulation in a coastal region dominated by frequent strong offshore winds the experiment took place in march april 1998 in the northwestern mediterranean sea gulf of lion observations were collected with the r v l atalante with an air sea interaction spar asis buoy with waverider buoys and with research aircraft equipped for in situ and remote sensing measurements the present paper is an introduction to the following special section which groups 12 papers including this one presenting results on turbulent flux measurements at the ocean surface on the behavior of the marine atmospheric boundary layer on the ocean waves characteristics on the ocean circulation and on remote sensing of surface parameters this overview presents the background and objectives of fetch the experimental setup and operations and the dominant atmospheric and oceanic conditions and introduces the different papers of the special section