hydrographic structure of the convection regime in the gulf of lions winter 1987 abstract deep winter convection in the northwestern mediterranean gulf of lions and the subsequent formation of mediterranean deep water were observed using advanced oceanographic instrumentation during a six week long experiment in 1987 the severe 1987 european winter forced an intense outbreak of the mistral a cold dry wind blowing down the rhone valley in mid january surface cooling and evaporation were of sufficient intensity to cause an initial episode of deep convection shortly before the experiment described here began however several more mistral events took place during the experiment during several cruises into the area ctd and absolute horizontal velocity profiles were measured in the mixed area over the rhone fan as well as across the southern front of this region in addition continuous records of shipboard meteorological and oceanographic parameters air temperature surface salinity etc were made an early february mistral apparently did not produce enough surface cooling to

transport estimates at the western section of the strait of gibraltar a combined experimental and numerical modeling study 1 three yearlong time series of acoustic doppler current profiler adcp observations at a single station in espartel sill strait of gibraltar were used to compute an outflow of q2 0 82 sv through the main channel the cross strait structure of the velocity field or the outflow through a secondary channel north of the submarine ridge of majuan in espartel section is not captured by observations so that an improved version of a numerical model cepom has been used to fill the observational gap previously the model performance has been checked against historical data sets by comparing harmonic constants of the main diurnal and semidiurnal constituents from observed and modeled data at different sites of the strait considering the great complexity of tidal dynamics in the area the comparison is quite satisfactory and validates the model to infer the exchange at longer timescales using a climatological april in the simulation extracting a single station from the model at the same position as the monitoring station and processing the data similarly the model gives an outflow through the southern channel 13 higher than observations the inclusion of the cross strait structure of velocity reduces the computed outflow through the southern channel whereas the contribution of the northern channel brings the total outflow close to that computed using a single station 5 smaller if the same correction is applied to observations the total outflow would reduce to q2 0 78 sv the paper also assesses the importance of eddy fluxes to the total outflow their contribution being negligible 5

warming salting and origin of the tyrrhenian deep water 1 data collected from 1996 to 2001 down to 3 500 m in the tyrrhenian sub basin with ship handled and moored instruments show 5 year t and s trends 0 016 c yr 0 008 yr that are the largest ever evidenced in mediterranean deep waters this is not consistent with the usual hypothesis that tyrrhenian deep water tdw is a mixture of eastern water flowing from the sicily channel and western water flowing from the sardinia channel partly since both are reported to encounter lower trends we argue that tdw might result from a dense water formation process occurring within the tyrrhenian itself in a region never reported up to now east of the bonifacio strait whatever the validity of our hypothesis climatic changes are occurring in the whole sea and are efficiently specified with long time series

a laboratory study of gyres and uplift near the strait of gibraltar laboratory experiments were conducted in which a rotating basin of stratified salty water in a field of gravity with a free surface was connected to a basin of fresh water by a narrow shallow channel the resulting density driven flow in the channel consisted of two currents a freshwater flow at the top from the fresh basin to the salty basin and a saltwater flow at the bottom in the opposite direction it models the flow in the strait of gibraltar which connects the atlantic ocean to the saltier mediterranean sea selective withdrawal of deep water up to and over the sill depth is observed in the stratified salty mediterranean basin the governing dimensionless numbers are the ratio of the rossby radius of deformation within the strait to the width of the strait and the ratio of rossby radius in the stratified med water to rossby radius of deformation within the strait the experiments were deliberately scaled to correspond to the parameters of the real mediterranean gibraltar region or not as we wished with the most correct parameters the water at a depth corresponding to 700 m in the mediterranean was selectively withdrawn up to sill depth and out of the salty basin the water at a depth corresponding to 900 m was not with double the correctly scaled stratification the water at a depth corresponding to 500 m was drawn out and the water at a depth corresponding to 700 m was not with no stratification water of a depth corresponding to 1200 m was drawn out the results are qualitatively consistent with the ideas of stommel et al 1973 that water at great depth in the mediterranean is drawn up and out at the strait of gibraltar although quantitatively the scaled experimental depths of withdrawal are not as great there are some indications that the gyre of atlantic water corresponding to the alboran sea gyre may enhance the selective withdrawal process but the mechanism is unclear

three layer view of transports and hydraulics in the strait of gibraltar a three dimensional model study 1 the ability of a three dimensional sigma coordinate free surface model to reproduce the interfacial layer between the atlantic and mediterranean waters in the strait of gibraltar is verified the model uses a coastal following curvilinear orthogonal grid that includes the gulf of cadiz and the alboran sea with very high resolution in the strait less than 500 m it is forced by imposing the two major semidiurnal tidal components m2 and s2 along the atlantic and the mediterranean open boundaries the main experiment covers an entire spring neap cycle fortnight period results show that the model is able to reproduce a thick interfacial layer that carries a substantial fraction of the total transport the interfacial thickness is strongly modulated by tidal forcing that enhances the vertical exchanges between layers in order to take into account the thick interfacial layer a three layer approximation is used to study the hydraulics results show that the exchange regime is intermittently maximal due to cyclically controlled regions over camarinal sill and within tarifa narrows the analysis has been repeated in a two layer framework to evaluate the impact of the introduction of an interfacial layer on the calculation of hydraulics in the two layer approximation there is not any controlled region extending on the whole cross section so the exchange is always submaximal concluding the two layer approximation underestimates hydraulic controls in the strait respect to the three layer approach

tracking the mediterranean outflow in the gulf of cadiz abstract the mediterranean water leaves the western end of the strait of gibraltar as a bottom wedge of salty and warm waters flowing down the continental slope the salinity of the onset mediterranean outflow water mow is so high that leads to water much denser initially in excess of 1 5 kg m 3 than the overlying central waters during much of its initial descent the mow retains large salinity anomalies causing density anomalies that induce its gravity current character and relatively high westward speeds causing a substantial coriolis force over long portions of its course we use hydrographic data from six cruises a total of 1176 stations plus velocity data from two cruises together with high resolution bathymetric data to track the preferential mow pathways from the strait of gibraltar into the western gulf of cadiz and to examine the relation of these pathways to the bottom topography a methodology for tributary systems in drainage basins modified to account for the coriolis force emphasizes the good agreement between the observed trajectories and those expected from a topographically constrained flow both contour avenues and cross slope channels are important and have complementary roles steering the mow along the upper and middle continental slope before discharging as a neutrally buoyant flow into the western gulf of cadiz our results show that the interaction between bottom flow and topography sets the path and final equilibrium depths of the modern mow furthermore they support the hypothesis that as a result of the high erosive power of the bottom flow and changes in bottom water speed the mow pathways and mixing rates have changed in the geological past

meteorologically forced subinertial flows through the strait of gibraltar the observed transport due to subinertial flows with periods ranging from days to a few months through the strait of gibraltar reaches values up to 106 m3 s 1 and is well correlated with atmospheric pressure fluctuations over the mediterranean sea this transport is barotropic and accounts for 84 of the variance observed at these frequencies a second mode accounts for 12 of the variance and is characterized by a node zero amplitude located at the mean depth of the interface between atlantic and mediterranean waters this baroclinic mode is modulated by the spring neap tidal cycle corresponding to an increased exchange of waters between atlantic and mediterranean at neap tides a simple model of the mediterranean which includes two basins and two straits indicates that the system has two resonant frequencies at periods of 1 2 and 5 6 days the 1 2 day resonance corresponds to the eastern and western basins oscillating through the strait of sicily while that at 5 6 days is the resonance of the mediterranean sea with the north atlantic ocean a good approximation to the observed flows is obtained when this model is forced with the most energetic mode of the atmospheric pressure over the eastern and the western mediterranean and a friction term is included to limit the flow through the strait of gibraltar restricting the flow through the strait of sicily does not improve the agreement between the model and the observations for the flows at gibraltar

deep water formation in the western mediterranean wintertime deep convection was studied in the gulf of lions northwestern mediterranean using the chlorofiuoromethane cfm distributions components f11 and f12 from december 1991 and february march 1992 convection occurred on small spatial and temporal scales and it was not complete only convection to 1900 m depth was observed the vertical mixing of the water column above the convection depth turned out to be of major influence regarding the characteristic of newly formed deep water and regarding the boundary conditions for cfms in modeling deep water formation air sea gas exchange and entrainment were found to be negligible these findings are important in estimating deep water formation rates for all water masses renewed by convection e g greenland sea deep water labrador sea water and in evaluating the spreading of deep water masses along the western boundary current a box model is presented which uses cfm and tritium distributions to estimate formation of western mediterranean deep water below 1000 m the model starts with zero tracer concentrations in 1945 the integration step is 1 year and the deep water formation rate is assumed to be constant from 1945 to 1992 the best fit between cfm model concentrations and measurements were obtained at a mean deep water renewal time of 5 7 years equivalent to a conversion of 0 46 sv modified atlantic water 0 to 150 m depth and 0 76 sv levantine intermediate water 150 to 400 m depth into deep water however the tritium measurements are only partly matched by the model by assuming that convection stopped in the years 1964 1968

ar ar ages and trapped ar components in martian shergottites rbt 04262 and lar 06319 abstract we made 39ar 40ar ar ar analyses of whole rock wr and mineral samples of two martian shergottites rbt 04262 rbt and lar 06319 lar in order to determine their ar ar ages and the 40ar 36ar ratios of the trapped martian ar they contain all samples released trapped excess 40ar and 36ar and suggested ar ar ages older than their formation ages because trapped ar components having different 40ar 36ar were released at different extraction temperatures we utilized only a portion of the data to derive preferred ar ar ages we obtain ar ar ages of 171 8 ma for rbt plagioclase and 163 13 ma for lar whole rock we identify two trapped ar components at low temperatures particularly for plagioclase trapped a with 40ar 36ar 285 3 was released and we believe this is most likely absorbed terrestrial air at high extraction temperatures particularly for pyroxene trapped b with 40ar 36ar 1813 127 was released the poikilitic non poikilitic texture of rbt and the presence of large pyroxene oikocrysts allowed a clear definition of trapped b this ar component is martian and its isotopic similarity to the martian atmospheric composition suggests that it may represent martian atmospheric ar incorporated into the shergottite melt via crustal rocks trapped b partitioned into pyroxene at a constant molar ratio of k 36artr 33 2 9 5 106 for rbt 04262 and 80 21 106 for lar 06319 trapped a mixed in different proportions with trapped b could give apparently intermediate trapped 40ar 36ar compositions commonly observed in shergottites

on the upper layer circulation in the alboran sea we present new experimental results and assemble them with previous results in order to develop an improved picture of the upper layer circulation in the alboran sea it is suggested that the key idea to understanding this upper layer circulation is the tendency of the atlantic jet aj to have negative curvature local interactions with the western alboran gyre wag or the african coast can however counterbalance this tendency and modify the anticyclonic path of the aj it is also proposed that the density gradients in the wag can be maintained in part by means of an intermittent surface cross gyre current which results in an input mixing and renewal of atlantic water the static stability at the bottom of the gyre increases because of the mixing of atlantic water with western mediterranean deep water which is uplifted close to the african coast this mixing process thereby acts as a local source of potential vorticity we also report the existence in the alboran sea of subsurface anticyclonic eddies located between 100 and 400 m of relatively cold water that appear to be detached from the iberian shelf regarding the large scale variability of the aj wag system we present evidence of an eastward migration of the wag and the subsequent formation of a new anticyclonic gyre in the western alboran basin on a timescale of 1 month this eastward gyre migration process temporarily allows the simultaneous presence of three anticyclonic gyres in the alboran sea

how important are diapycnal mixing and geothermal heating for the deep circulation of the western mediterranean the dissipation rate of turbulent kinetic energy e and the associated diapycnal turbulent mixing is inferred from a set of microstructure observations collected over several cruises from year 2012 to 2014 the geographical distribution of e highlights several regions of enhanced levels of turbulence ranging from 10 9 to 10 6 w kg 1 the sicily channel the corsica channel and the ligurian sea elsewhere e was small often below 10 10 w kg 1 below 1300 m geothermal heating provides three fold more buoyancy than small scale turbulence geothermal heating and turbulent diffusion provide enough buoyancy to balance 15 to 50 of a mean yearly deep water formation rate of 0 9 to 0 3 sverdrup 106 m3 s respectively the remaining part has to eventually overflow through the strait of gibraltar

mediterranean climate and oceanography and the periodic development of anoxic events sapropels mediterranean sapropels are layers with elevated organic carbon concentrations that contrast with surrounding sediments which are organic poor sapropels occur quasi periodically in sedimentary sequences of the last 13 5 million years and exist both in the eastern and western mediterranean sub basins they have been the subject of extensive study based on records from both short conventional and long ocean drilling program sediment cores and from a wide variety of uplifted marine sediment sequences on the basin margins and islands previous syntheses in the 1990s and 2000s have discussed how the formation of sapropels is commonly ascribed to deep sea anoxia enhanced export productivity or a combination of these effects however a wealth of new evidence and insights has emerged during the past 1 2 decades based on traditional and novel proxy data as well as modelling which has revealed intriguing new aspects and nuances to the reconstructed conditions hence it is timely to present a new synthesis of current understanding of the processes behind the formation of sapropels which have over the past decade also become a matter of commercial interest in sub salt hydrocarbon exploration in this review we present a context of modern mediterranean climate and oceanography followed by an integrated assessment of the growing understanding of climatological and ocean circulation changes that were associated with sapropel deposition we find that sapropels predominantly formed during astronomically timed episodes when climatic and oceanographic conditions and ecological responses broadly preconditioned the basin for sapropel deposition there is strong correspondence with times of monsoon intensification fuelling runoff from north africa into the mediterranean sea while preconditioning due to sea level rise and regional precipitation and runoff may have contributed as well within these broad episodes of surface buoyancy gain and resultant decline in deep water ventilation specific deposition under dysoxic anoxic or even euxinic conditions occurred within a clearly dynamic system that was characterised by complex spatial and depth dependent patterns gradients with distinct temporal variability on at least decadal to centennial millennial timescales in the final section we evaluate the implications of different modes of deep water removal from silled basins to investigate why sapropels are more frequently and often more intensely developed in the eastern mediterranean than in the western mediterranean

the western mediterranean deep water a proxy for climate change reconstructions of mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the north atlantic and the western mediterranean deep water wmdw formed in the gulf of lions in winter because of consistent air sea heat fluxes over these areas strongly correlated to the north atlantic oscillation nao

observation of an abrupt disruption of the long term warming trend at the balearic sea western mediterranean sea in summer 2005 1 the properties of the western mediterranean deep water in a wide area located at the western boundary of the mediterranean sea including the balearic sea have revealed intense changes when observed in summer 2005 between february and june 2005 a temperature drop of 0 14 c reverted dramatically the progressive warming trend of 0 011 c yr 1 that had been observed since 1996 in the waters below 600 dbar north of the balearic channels a similar temperature drop has been observed east of the minorca island below the levantine intermediate water and down to 1500 dbar in the deepest levels a complex thermohaline structure which implies different waters masses as sources was tracked more than 400 km along the western boundary of the mediterranean sea from barcelona to the algerian basin it is suggested that the changes may be linked to the severe 2004 2005 winter occurred at the northwestern mediterranean sea

interbasin deep water exchange in the western mediterranean owing to its nearly enclosed nature the tyrrhenian sea at first sight is expected to have a small impact on the distribution and characteristics of water masses in the other basins of the western mediterranean the first evidence that the tyrrhenian sea might in fact play an important role in the deep and intermediate water circulation of the entire western mediterranean was put forward by hopkins 1988 there an outflow of water from the tyrrhenian sea into the algero provencal basin was postulated in the depth range 700 1000 m to compensate for an observed inflow of deeper water into the tyrrhenian sea however this outflow the tyrrhenian deep water tdw was undetectable since it would have hydrographic characteristics that could also be produced within the algero provencal basin a new data set of hydrographic tracer lowered acoustic doppler current profiler ladcp and deep float observations presented here allows us now to identify and track the tdw in the algero provencal basin and to demonstrate the presence and huge extent of this water mass throughout the western mediterranean it extends from 600 m to 1600 1900 m depth and thus occupies much of the deep water regime the outflow from the tyrrhenian is estimated to be of the order of 0 4 sv sv 10 6 m 3 s 1 based on the tracer balances this transport has the same order of magnitude as the deep water formation rate in the gulf of lions the tyrrhenian sea effectively removes convectively generated deep water western mediterranean deep water wmdw from the algero provencal basin mixes it with levantine intermediate water liw above and reinjects the product into the algero provencal basin at a level between the wmdw and liw thus smoothing the temperature and salinity gradients between these water masses the tracer characteristics of the tdw and the lowered adcp and deep float observations document the expected but weak cyclonic circulation and larger flows in a vigorous eddy regime in the basin interior

ten years of marine current measurements in espartel sill strait of gibraltar more than 10 year of acoustic doppler current profiler observations collected at the westernmost sill espartel sill of the strait of gibraltar by a monitoring station have been carefully processed to provide the most updated estimation of the mediterranean outflow a comprehensive quality control of the factors affecting the uncertainty of the measurements has been carried out and great care has been paid to infer the current at the bottom layer where direct observations are lacking the mean outflow in the southern channel of the sill section has been estimated as 0 82 sv 1 sv 1 106 m3 s 1 with an average contribution of the eddy fluxes of 0 04 sv this figure is an overestimation as the mooring measurements assumed valid for the whole section ignore the lateral friction on the other hand it only gives the flow through the southern channel and disregards the fraction flowing through shallower northern part both drawbacks have been addressed by investigating the cross strait structure of the outflow from hindcasts produced by the mitgcm numerical model run in a high resolution domain covering the gulf of cadiz and alboran sea basins an overall rectifying factor of 1 039 was found satisfactory to correct the first estimate so that the final mean outflow computed from this data set is 0 85 sv complemented with an uncertainty of 0 03 sv based on the interannual variability of the series the temporal analysis of the series shows an outflow seasonality of around the 8 of the mean value with maximum outflow in early spring

mesoscale dynamics and vertical motion in the alboran sea abstract the inflow of atlantic water through the strait of gilbraltar usually exhibits a stationary wavelike pattern in the alboran sea we use an objective analysis technique for quantitative scale separation to investigate the interaction of scales in the region the large scale is clearly dominated by an anticyclonic gyre smaller scale analysis shows the existence of several mesoscale cyclonic eddies along the northern boundary of the western alboran sea anticyclonic gyre the relationship between the large scale mesoscale variability and the induced ageostrophic vertical motion is established using the q vector formulation we find that on the macroscale upward motion occurs upstream of the anticyclonic gyre upstream of a wave crest while downward motion takes place downstream upstream of a trough we also show that the vertical motion associated with the mesoscale eddies is an order of magnitude higher than the large scale vertical motion these patterns of large scale and mesoscale vertical m

evaluation of regional ocean circulation models for the mediterranean sea at the strait of gibraltar volume transport and thermohaline properties of the outflow a set of simulations from different configurations of the nemomed8 nemomed12 and nemomed36 ocean regional circulation models for the mediterranean sea has been studied in order to assess the accuracy of their representation of the exchange through the strait of gibraltar the model volume transport and thermohaline properties of the mediterranean outflow have been compared with observational data collected at espartel sill the westernmost sill of the strait by a permanent station moored since october 2004 in the frame of the ingres projects results show that in terms of volume transport nemomed8 simulations perform a better representation of the exchange while nemomed12 36 underestimate both the mean inflow and outflow the reason for this underestimation is a too low velocity of the flow which could be consequence of an enhanced roughness effect due the flow bathymetry interaction an important improvement in the representation of the exchange seasonality is achieved by the simulations including sea surface height variability of the atlantic area of the domain the results for the themohaline characteristics of the mediterranean outflow are better for nemomed12 and nemomed36 as a consequence of their better representation of the local dynamical processes that leads to a more realistic composition of the mediterranean waters comprising the flow

quaternary stress regime change in the hatay region se turkey in this study we determine the plio quaternary to present day stress regime acting in the hatay region located at the northeastern corner of the east mediterranean region the modern state of stress is obtained from inversion of focal mechanism solutions of shallow earthquakes this inversion identifies a dominantly extensional stress regime with a ne trending h m i n 3 axis at the present day the stress regime determined from inversion of slip vectors measured on fault planes confirms that this regime is extensional in the studied area both the kinematics and chronologies of fault slip vectors show that the stress state changed from an earlier strike slip regime to a younger extensional stress regime with a consistent ne trending h m i n 3 axis the change from strike slip to extensional stress regimes probably occurred during the quaternary regionally both stress regimes induce sinistral displacement on the east anatolian fault and dead sea fault systems the north anatolian fault naf is a dextral strike slip fault which runs about 1400 km from east to west and has been active since collision between the eurasian and arabian plates together with the sinistral east anatolian fault the naf intracontinental deformation zone contributes to the westward extrusion of anatolia as a consequence of northward drift of arabia consequently the late cenozoic stress regimes acting in the hatay region result from the coeval influence of forces due to 1 the subduction processes in the west and southwest 2 the continental collision in the east and 3 the westward escape of the anatolian block however the timing of the temporal stress transition suggests that the quaternary stress regime change resulted from subduction processes with the extensional stress regime in the hatay region being mainly attributable to roll back of the mediterranean subducted slab along the cyprus arc

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

an extensive western mediterranean deep water renewal between 2004 and 2006 1 the deep waters of the western mediterranean are known to have an almost constant trend towards higher salinity and temperature values since the 1950s recent observations have shown an acceleration of this tendency which has been attributed by some authors to the effect of the propagation of the signal of the eastern mediterranean transient from east to west from 2004 to 2006 five basin scale oceanographic cruises evidenced a relevant change in the deep structure of the western mediterranean in less than two years almost the whole deep basin has been filled with highly saline and warm new deep water which substantially renewed the resident deep water the paper shows evidence of the rapid basin wide extension of the event giving insights into the origin and the propagation of the new deep water towards the basin interior and showing the evolution of the deep characteristics

dense water dynamics along the strait of sicily mediterranean sea abstract hydrographic and current meter data gathered in different periods in the strait of sicily and in the southern tyrrhenian sea allow the outflow characteristics from the eastern toward the western mediterranean basin to be analyzed the evolution through the strait of a deep vein of dense water coming from the eastern mediterranean is described together with the dynamic interaction with overlying layers these data are related to a slightly generalized version of recent density current models such as those of emms and those of baringer and price taking into account the dynamic influence of the overlying currents and in particular their friction and mixing this model explains the path of this deep flow and enables estimates of entrainment and bottom friction to be made with these new data a phenomenon of considerable interest namely the dynamics of density currents crossing and outflowing from a strait is examined and discussed

observation of a deep convection regime with acoustic tomography in the winter of 1991 1992 a convection experiment was conducted in the western mediterranean gulf of lions combining a variety of observational techniques an essential component was an acoustic tomography array consisting of six moorings designed to observe the time evolution of the large scale processes believed to be relevant in a convection regime here two dimensional slice inversions in three directions from the central mooring are used to estimate the volume of convected water and the mean convection depth and to observe the preconditioning and restratification processes before and after the convection the near surface layer is well sampled by the acoustics which show cooling and subsequent entrainment of the warmer levantine intermediate water liw from below in agreement with mixedlayer calculations during the 2 months prior to the main convection event the total heat loss of the large scale field is in approximate agreement with the surface heat fluxes showing that little net warm water advection takes place from outside the convection region the implied confinement of water by the local circulation should be an important factor in setting the location and extent of the deep convection patch the volume of water modified by convection in this winter is estimated to correspond to an area of order 60 km radius and 1500 m depth it is argued that the homogenized area implies an annual mean deep water replenishment of 0 3 sv the restratification by the return of less dense water in the surface and liw layers occurs first by rapid capping in the near surface region thereafter the southern and eastern parts of the region restratify in the deeper layers on a 40 day timescale while a dense core of 50 60 km diameter remains in the northwest until the end of the experiment

in situ and satellite observations of the eastward migration of the western alboran sea gyre during october 2003 an intensive oceanographic survey biomega was carried out in the alboran sea coinciding with a migration event of the western alboran sea gyre wag the observations gathered during that cruise constitute the first field evidence of a migrated stage of the wag in this work we present the main differences between the 3d hydrodynamic fields observed during biomega and those corresponding to a wag located at its usual position the migration of the gyre was followed by satellite altimetry and sea surface temperature imagery the causes of the gyre migration are explored in terms of the quasi geostrophic tendency equation in particular of the dynamics governing scales larger than the rossby radius of deformation it is shown that the steady state gyre must be almost equivalent barotropic and that the key process to break down the stationarity would be a density advection at gyre scale the mechanisms to explain the migration of the wag proposed by previous authors are discussed in light of the explanation proposed in this work

deep and intermediate water in the western mediterranean under the influence of the eastern mediterranean transient 1 the well known changes in the deep thermohaline circulation of the eastern mediterranean sea the so called eastern mediterranean transient emt which modified the outflow characteristics through the sicily strait led to significant changes in the western mediterranean sea since the early 90 s in spring 2005 an oceanographic survey carried out in the central part of the western basin showed the presence of a recently formed layer of western mediterranean deep water spreading at the bottom of the whole algero provencal basin it was characterized by unusual 0 s shapes as its temperature salinity and density were higher with respect both to the resident deep waters and to the climatological values the possible influence of the emt on the deep water formation processes occurred in the gulf of lions in the previous winter is here evidenced even taking into account other data sets previously collected in the western mediterranean

atlantic forcing of the mediterranean oligotrophy 1 the mediterranean sea shows a peculiar anomaly in its nutrient pattern compared to the global ocean as there is decrease in nutrient concentration from west to east this feature has been attributed to the antiestuarine circulation at the strait of gibraltar where an eastward flow of atlantic nutrient poor surface waters is compensated by a westward countercurrent of mediterranean nutrient rich deep waters this water exchange has been suggested as the ultimate cause for the oligotrophy of the mediterranean basin even though only a few studies have accurately examined the magnitude of the nutrient flux through the strait of gibraltar in this work data from the gibraltar fixed time series gift between 2005 and 2008 were used to assess nutrient distributions applying a two layer model of water mass exchange and using the mediterranean outflow recorded in situ the net export of nutrients from the mediterranean to the atlantic was calculated as 139 and 4 8 gmol yr 1 of nitrate and phosphate respectively the results also demonstrated that the atlantic inflow is not nutrient depleted and in particular contains significant levels of phosphate which is the limiting factor for biological productivity in the eastern mediterranean the distribution of the quasi conservative parameter n in the western and eastern basins indicated that nitrate deficient surface waters are transformed into phosphate deficient bottom waters by internal cycling processes therefore phosphate depletion in the mediterranean does not have its origin in the entry of a phosphorus impoverished atlantic inflow through the strait of gibraltar

palaeoclimate and palaeoceanographic conditions in the westernmost mediterranean over the last millennium an integrated organic and inorganic approach previous studies have revealed the excellence of the westernmost mediterranean records for reconstructing climate conditions over the last two millennia in particular inorganic and organic proxies have revealed a coherent signal of climate and oceanographic responses during this time here we compare and integrate both proxy records for reconstructing climate and oceanographic conditions with focus on the last millennium the higher temperatures indicated by lipid based proxies during the medieval climate anomaly mca are coincident with drier conditions indicated by inorganic proxies in contrast lower temperatures and humid conditions are indicated during the little ice age lia the industrial period was characterized by increasing humidity in comparison with the previous lia however a progressive aridification occurred since the second half of the twentieth century coexisting with a warming trend and higher contribution of c3 grasses proxy records are also interpreted to show atlantic water inflow at ad 1450 and 1950 and an intensification of the upwelling conditions coinciding with a prolonged positive north atlantic oscillation nao phase in the intervals ad 1000 1450 and 1960 1990 large scale oceanic atmospheric circulation patterns the nao and the atlantic meridional circulation and solar irradiance variations seem to have played the major key role during the last millennium together with anthropogenic contributions in the more recent record

the very first transformation of the mediterranean outflow in the strait of gibraltar 1 time series collected in the camarinal and espartel sills the two main sills of the strait of gibraltar have been analyzed to assess the first transformation of the mediterranean outflow in espartel west of camarinal sill the outflow has been estimated from a 6 year long time series of acoustic doppler current profiler observations the near bottom water flowing out at espartel is around 0 1 units saltier and 0 1 c warmer than at camarinal which is explained by entrainment and mixing of atlantic water by the outflow inside the basin bounded by both sills the constancy of heat and salinity transport implies an atlantic water entrainment of 0 03 sv which is about 4 of the outflow observed at espartel 0 77 sv and a flow of 0 74 sv at camarinal 96 of the flow at espartel it is also shown that the high energy dissipation rate associated with internal tides is enough to sustain the entrainment and a thorough mixing of the entrained water

interannual variability of the mediterranean outflow observed in espartel sill western strait of gibraltar 1 four year time series of observations in espartel sill at the western part of the strait of gibraltar have been analyzed in order to investigate the variability of the mediterranean outflow it is assumed that the observed variability comes from the changing properties of the dense waters that are located at the maximum depth from where they can be uplifted in the upstream basin alboran sea inside the mediterranean sea and evacuated through the strait from this perspective the following three mechanisms are investigated 1 the replenishment of the deep basin by newly formed western mediterranean deep water that depending on its density can either uplift old resident waters or lay above them leaving in any case a cold signature in the temperature series 2 the presence absence of the energetic anticyclonic gyres in the alboran sea particularly the western one which can transfer momentum to the underlying mediterranean vein and provide it with additional energy to ascend over the sills of the strait and 3 the meteorologically enhanced flows that follow the rapid changes of atmospheric pressure over the western mediterranean basin which would be able to aspire deeper waters residing in the upstream basin the three mechanisms act on different timescales from annual in case 1 to monthly in case 2 to weekly in case 3 although these two latter are modulated annually by the seasonal prevalence of the western alboran gyre in summer and of the strong meteorologically driven fluctuations in winter the mechanisms overlap at annual timescales making it difficult to separate out the different contributions

the flow of atlantic water through the strait of gibraltar abstract we describe and analyze observations of the water exchange through the strait of gibraltar the primary observations were taken in april 1986 and included data from moored recording instruments at four locations in the strait together with an intensive survey by ship these measurements included extensive ctd profiling acoustic doppler current profiling numerous profiles from expendable instruments and imaging using a high frequency echo sounder the analysis focuses on the internal hydraulics of the strait and in particular the presence of hydraulic controls and their influence on the exchange our observations during april 1986 show that the maximal exchange condition in which a subcritical flow is bounded by supercritical flow at both ends of the strait did occur although with various subtleties not explicitly incorporated in our previous theoretical developments the atlantic water moving east along the surface encounters a control at tarifa narrows in the eastern part of the strait the mediterranean water passes through controls both at camarinal sill and at spartel sill further west at our westernmost mooring at spartel the outflowing mediterranean water is continuously supercritical with little tidal variability the control at camarinal sill is periodically lost due to tidal action and reappears on a reverse flow during a falling spring tide tangier basin bounded by camarinal and spartel sills acts as an internal reservoir for the outflowing mediterranean water the interface rising and falling through each tidal cycle during spring tides the tangier basin interface rises high enough to flood the control at camarinl sill and produces a reverse flow of the lower layer when control is lost at camarinal sill a travelling bore is released this bore may modify the location of the control acting on the surface layer in tarifa narrows the atlantic water enters the alboran sea as a jet which may have a well defined northern boundary where it separates from the european coast this boundary may be identified by the presence of a slick although the internal jump west of camarinal sill is almost certainly an area of intense mixing frictional effects do not appear to be dominant in the subcritical portion of the flow