a numerical model study of the alboran sea gyre abstract reduced gravity and two layer numerical models have been used to study the circulation in the westernmost basin of the mediterranean sea the alboran sea circulation is forced by flow through a 20 km wide port in the western boundary representing the strait of gibraltar the reduced gravity model domain is a rectangle measuring 600 km 160 km with 10 km 5 km grid resolution when forced by an eastward on northeastward inflow the model solutions evolve to a steady state which exhibits a meandering current the first meander of the current forms the northern boundary of an anticyclonic gyre horizontal dimensions of the gyre are strongly dependent upon the inflow angle vorticity associated with the incoming current magnitude of the incoming transport and the north south extent of the basin the meandering current is considered a standing rossby wave with a highly distorted vorticity trajectory due to the interaction of the current with the northern and southern boundaries when velocity transport is increased the wavelength increases approximately as v as a result the anticyclonic gyre shifts east as velocity increases and west as velocity decreases these solutions show that bottom topography winds and coastline features are not necessary mechanisms for the formation of the gyre two layer model solutions were obtained using realistic topography geometry and a westward moving lower layer the addition of the lower layer flow and topography distorted the circulation in the upper layer particulary in the southern half of the basin this is caused by the large topographically steered currents along the southern shelf the high variability of the horizontal dimensions and location of the gyre has been observed both experimentally and through satellite imagery model results show that the high variability is caused by variations in the inflow velocity drifter tracks both observational and model derived help determine the circulation in both layers of the alboran sea the close comparison between model and experimental drifters lends credibility to the model circulation and dynamics

airborne synthetic aperture radar tracking of internal waves in the strait of gibraltar abstract as part of the international gibraltar experiment we realized on june 22 and 24 1986 two surveys of the strait of gibraltar on board an aircraft equipped with a synthetic aperture radar our objective was to observe at spring tides and during two twelve hour tidal cycles at 24 h interval the generation of internal wave trains linked to the hydraulic jump formed west of the sill during the westward phase of the tidal current and their eastward propagation in the strait the speed of propagation of these waves and the effect of the diurnal component of the tide on their generation and propagation could then be determined our results suggest that two solitary waves of equal amplitude propagated eastwards in the strait on june 22 the tidal coefficient being equal to 92 with a speed relative to the ground of 2 1 to 2 6 m s 1 24 h later during the second survey on june 24 tidal coefficient 90 we observed the propagation of a train of non linear waves the speed of the leading wave of which being about 1 9 ms 1 our data show that other waves pass over the camarinal sill after the release of the bore and secondary internal wave trains are shown to propagate eastwards from there although our sar data show the appearance of waves west of the northern sill at about 4 h after high water hw the mechanism leading to their generation is not clear these waves could propagate eastwards all along the strait and or northwestwards along the western spanish coast they could be responsible for the solitary type events observed at the eastern entrance of the strait at about 7 h after hw by ziegenbein 1969 1970 these events are noticeable in the hydrological parameters time series of armi and farmer 1988 and in the high rate current data 2 min apart from their april 1986 cruise besides these alongstrait waves our sar data show the existence of cross strait waves and give an idea of their wavelength and speed of propagation their presence leads to perturbations in the current revealed by simultaneous current data at the camarinal sill and north of cape cires

the advection of submesoscale thermal features in the alboran sea gyre abstract noaa 7 infrared and nimbus 7 multi spectral visible imagery of the alboran sea collected as part of the donde va experiment during the period 6 20 october show the advection of submesoscale cold water features about the alboran sea gyre continuous monitoring of thew cold water features using satellite imagery is possible because of the twice daily every 12 h spacing of the noaa 7 coverage of the area after registration to a mercator projection and atmospheric correction analysis of the displacement of the cold water features in successive images shows their apparent origin to be just east of gibraltar their movement at average speeds of 0 4 m s 1 around the gyre and their apparent re entrainment into the incoming atlantic water east of gibraltar the nimbus 7 czcs imagery supplements the analysis by adding details of the movement and the theory on where the cold water features originate during the 15 day period nine cold water features were thermally distinct enough to be tracked for

aluminium as a tracer of the deep outflow from the mediterranean dissolved aluminium has been determined in sea water samples from the southwestern alboran sea and the gulf of cadiz partial dissolution of eolian dust is responsible for the elevated levels of dissolved al that were found in both the western mediterranean deep water wmdw 111 5 nm and levantine intermediate water liw 86 2 nm masses in the alboran sea the al concentration in the outflowing plume of mediterranean water sampled in the gulf of cadiz is also elevated 72 nm these enhanced signals and the differences between them are used in a three water mass system to calculate a maximum 10 contribution of western mediterranean deep water to the outflow plume considerably less than has been previously supposed while the synoptic nature of this study and the possibility of involvement of other water masses in the outflow plume leave scope to increase the participation of wmdw in the outflow plume these measurements indicate the potential of a nontransient tracer in elucidating the component parts of complex flow systems copyright american geophysical union 1988

high fertility in the alboran sea since the last glacial maximum based on the glacial to postglacial 13c differences between endobenthic uvigerina peregrina species from the alboran basin and from other mediterranean basins changes in the fertility of the western part of this basin during the last deglaciation are reconstructed as a result of particulate organic carbon poc rain from the highly productive upwelling cell along the northwestern margin of the alboran basin u peregrina is presently depleted by about 1 6 with respect to the measured 13c values of bottom water co2 and by about 0 9 with respect to specimens from other areas of the western mediterranean or from the gulf of cadiz within the mediterranean outflow water the uvigerina 13c difference between the alboran sea and the gulf of cadiz 13c was close to 0 at the beginning of the last deglaciation and during the late glacial time this suggests that highly fertile systems set in the alboran sea near 16 kyr b p two rapid increases in the 13c offset are recorded near 15 kyr and 11 kyr b p fluctuations around 1 1 to 1 2 occurred during the early holocene and a maximum was reached near 9 kyr b p after 4 kyr the 13c offset decreased to its present day average value of 0 9 changes in the intensity of surficial production cannot account for all the observed fluctuations especially in the early holocene time a strong decrease in the intermediate and deep water ventilation of the alboran basin may have occurred near 8 9 kyr in phase with the last stagnant phase in the eastern mediterranean and the deposition of sapropel s1 as a result the redistribution and remineralization at depth of the produced organic matter was incomplete the poc rain reaching the sediment was locally intensified and caused the lowering of the 13c values of endobenthic foraminifers such as u peregrina the benthic 13c signal suggests that the difference between the alboran sea and the gulf of cadiz was at its maximum at the same time an important modification in the water masses structure may have occurred near 9 8 kyr b p the deepening of the permanent pycnocline probably related to a thicker atlantic jet at a stage of high sea level stand is recorded by the replacement of the right coiling n pachyderma dominance coincident with a shallow pycnocline by the g inflata dominance coincident with a deep pycnocline diatom abundances were strongly reduced indicating an important modification of the productive system the glacial postglacial evolution of productivity within the alboran basin was therefore more complex than in the adjacent atlantic ocean and opposite to the global one which displays a general increase in productivity during glacial time although it is the global budget of paleoproductivity that would drive the partitioning of carbon within the ocean local or regional discrepancies with the global glacial interglacial model must be addressed local winds and regional atmospheric pressure systems which are the forcing factors for circulation and exchange with the atlantic control the fertile systems of the alboran basin

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

remotely sensed sea surface thermal patterns in the gulf of cadiz and the strait of gibraltar variability correlations and relationships with the surface wind field satellite image sequences covering periods of a few days throughout the annual cycle of the waters off southern iberia have been analyzed in conjunction with concurrent surface wind speed data from coastal stations qualitative analysis reveals a large degree of temporal and spatial variability in the thermal signature of the sea surface over periods of both a few days and several months during the summer a cool seasurface temperature signature extends from the western iberian coast around cape st vincent and eastward as far as faro at the same time a warm signature originating on the iberian coast between faro and cadiz extends into the strait of gibraltar these two features are shown to sometimes adopt more westerly positions and the strait experiences regions of cool thermal signature originating at its southern side during winter the surface flow into the mediterranean through the strait of gibraltar is anomalously warm and appears to come from the interior of the gulf of cadiz quantitative measurements show that temporal variability over timescales of a few days at individual sites is maximum in midsummer spatial thermal variability over the whole region is found to peak toward the end of the summer statistical analyses of the data reveal the coupling between the surface wind field in the gulf of cadiz and the surface thermal pattern especially during the summer wind induced across stream upwelling in the strait of gibraltar although dynamically subordinate to tidal and density driven processes is shown to occasionally dominate the surface thermal signature

significance of bottom currents in deep sea morphodynamics an example from the alboran sea we present an interdisciplinary study of the geomorphology sedimentology and physical oceanography of the alboran sea south western mediterranean sea to evaluate the potential role of bottom currents in shaping the spanish and moroccan continental margins and adjacent basins bathymetric and seismic data have allowed the recognition of the contourite deposits including depositional plastered sheeted channel related mounded confined elongated and separated drifts erosive moats channels and furrows and mixed terraces and scarps features hydrographic data offer new insights into the distribution of the mediterranean water masses and reveal that bottom circulation of the western intermediate water wiw and the levantine intermediate water liw interact with the spanish slope and the western mediterranean deep water wmdw on the moroccan slope spanish base of slope and deep basins the integration of distinct datasets and approaches allows a proposal of a new sedimentary model for the alboran sea that details the significance of bottom current processes in shaping deep sea morphology this model considers the bottom circulation of water masses governs physiography that interface positions of water masses with contrasting densities sculpt terraces on a regional scale and that the morphologic obstacles play an essential role in the local control of processes and water mass distributions our findings demonstrate the pivotal role of bottom water circulation in seafloor shaping and sedimentary stacking patterns for continental margins establishing a new outlook for future studies of deep marine sedimentation

cause of the rupture and distribution of broken submarine carbonate chimneys in the gulf of cadiz southwestern spain abstract during the 2000 and 2001 r v cornide de saavedra cruises a vast field of hydrocarbon derived carbonate chimneys was discovered and sampled along the cadiz contourite channel and guadalquivir diapiric ridge photographs taken on board using an underwater camera revealed a spectacularly high density of pipe like chimneys lying on the sea floor though some of them were also found protruding from muddy sediment the major axes of the fallen chimneys which can be as long as 1 m exhibit a regular spatial distribution showing a conspicuous nw se trend furthermore their basal morphology shows a characteristic angular breakage associated to a flexo traction process both the uniform distribution of the major axis and the basal morphology of the chimneys imply that the cause of the rupture could be related either to strong bottom sea currents or to inertia forces associated with oscillatory ground motion due to seismic shaking the preferential orientation of the broken chimneys their mechanical properties the geological and topographical conditions of the area in relation to seismic ground motion amplification and the flow speed of the mediterranean outflow water mow along the cadiz contourite channel suggest that the most probable cause of the chimneys rupture was an earthquake the minimum magnitude of this seismic event is estimated to be more than 7 0 the causative fault being located directly under the chimney field or as far as 30 60 km away the chimneys rupture took place between ca 5 ka to present

paleobathymetric history of the western mediterranean sea shelf during the latest glacial period and the holocene quantitative reconstructions based on foraminiferal transfer functions abstract we present results of the palaeobathymetric evolution in cool water shelf carbonate environments of the western mediterranean sea during the latest glacial period and the holocene for this quantitative approach we used the weighted averaging partial least squares wa pls regression method for the development of benthic foraminifera based transfer functions and the modern analog technique mat to test the robustness of the models transfer functions were created on the basis of recent benthic foraminiferal assemblages in surface samples modern data sets and were then applied to fossil samples in sediment cores from the alboran platform the oran bight and the mallorca shelf the performance of the wa pls transfer functions suggests a close relationship between the observed and estimated water depths in the modern data sets with a precision of 11 m root mean squared error of prediction rmsep within water depths ranging from 38 to 160 m the estimated relative sea level histories of the alboran platform and the mallorca shelf show a total relative sea level rise of 50 m with sample specific errors of approximately 7 m and generally match the global and regional mediterranean sea records inconsistencies in the paleobathymetric estimates are strongly attributed to redeposition processes dating problems and to minor effects of an under representation of modern samples from shallower water depths

water masses and circulation in the western alboran sea and in the straits of gibraltar abstract some new elements of alboran sea circulation and water masses in close connection with flows through the straits of gibraltar are presented a general description is given of water masses found in 1981 during mediprod iv cruise from the gulf of cadiz to the gulf of lions followed by a brief review of the conditions found in the straits of gibraltar based on 1981 and 1961 observations the hydrological structure vertical and horizontal and surface and bottom currents typical of the western alboran sea are analysed we present some detailed observations about vertical currents in the deep waters near the straits and finally we analyse the characteristics of the mediterranean overflow through the straits our conclusions in part confirm those of bryden and stommel 1982 and in part shed light on the general pattern of the mediterranean currents entering the alboran sea from the east however considering the suggestion of stommel bryden and mangelsdorf 1973 that the deep currents in the interior of the western mediterranean basin are basically controlled by a bernoulli flow induced by the intense currents in the straits and the weak vertical stratification in the mediterranean we suggest that an interaction of a large scale circulation pattern and the topography of the alboran basin which is much shallower than the western mediterranean basin may play a major role in controlling hydraulically the deep mediterranean waters overflow a detailed water mass analysis of 1981 data and comparison with previous data revealed a time and space variability in the mediterranean waters the scales of this variability are unknown but the s variations make it difficult to make assumptions as to the depth of origin of the deep waters found in the alboran sea which flow into the atlantic ocean over the gibraltar sill

zinc isotope variations in deep sea carbonates from the eastern equatorial pacific over the last 175 ka the carbonate fraction of sediment core odp 849 leg 138 located in the eastern equatorial pacific mostly consisting of coccoliths was separated and analyzed for its zn isotopic composition the overall variation in zn isotopic composition as determined by multiple collector magnetic sector inductively coupled plasma mass spectrometry was found to be on the order of 1 expressed in 66zn where xzn xzn 64zn sample xzn 64zn standard 1 103 and x 66 67 or 68 over the last 175 ka the analytical precision was 0 04 and the overall reproducibility was usually better than 0 07 the zn isotopic composition signal exhibits several marked peaks and a high frequency variability a periodogram of the 66zn signal showed two periodicities of 35 2 and 21 2 ka we suggest that the latter is caused by the precession of the earth s axis of rotation the periodogram exhibits a minimum at 41 1 ka thus showing that the zn isotopic composition is independent of the obliquity in the eastern equatorial pacific the range of 66zn values observed for the carbonate fraction of odp 849 overlaps with the range observed for fe mn nodules in the world s oceans which suggests that seawater carbonate zn isotope fractionation is weak we therefore assume that most of the zn isotope variability is a result of the selective entrainment of the light isotopes by organic matter in the surface ocean the odp 849 66zn record seems to follow the changes in the insolation cycles changes in the late summer fall equatorial insolation modulate the intensity of the equatorial upwelling hence the mixing between deep and surface waters we propose that during decreased summer fall equatorial insolation when a steep thermocline can develop el nino like conditions the surface waters cannot be replenished by deep waters and become depleted in the lighter zn isotopes by biological activity thus resulting in the progressive increase of the 66zn values of the carbonate shells presumably in equilibrium with surface seawater

submesoscale tidally induced biogeochemical patterns in the strait of gibraltar abstract tidal forcing and its fortnightly variation are known to be one of the main regulating agents of physical and biogeochemical signatures in the strait of gibraltar and surrounding areas samples obtained during spring and neap tides in the region were analyzed to determine the influence of this tidal variation on the submesoscale distribution of water masses and biological elements during spring tides strong and intermittent mixing processes between mediterranean and atlantic waters occur in the vicinity of the camarinal sill together with an eastward advection of those mixed waters into the alboran sea furthermore the intense suction of surface coastal waters into the main channel of the strait was detected as chlorophyll patches in the alboran sea during spring tides in contrast the most characteristic phenomenon during neap tides was the arrival of pulses of relatively nutrient rich north atlantic central waters to the surface regions of the alboran sea in addition traces of the suction of coastal waters were observed for the first time during neap tides therefore our results show that submesoscale processes are crucial in the dynamics of the strait of gibraltar and they must be considered for the correct description of the biogeochemical features of alboran sea especially during an inactive period of the coastal upwelling

a four dimensional analysis of the thermal structure in the gulf of lion the theoretical and experimental tomography in the sea experiment thetis 1 took place in the gulf of lion to observe the evolution of the temperature field and the process of deep convection during the 1991 1992 winter the temperature measurements consist of moored sensors conductivity temperature depth and expendable bathythermograph surveys and acoustic tomography because of this diverse data set and since the field evolves rather fast the analysis uses a unified framework based on estimation theory and implementing a kaiman filter the resolution and the errors associated with the model are systematically estimated temperature is a good tracer of water masses the time evolving three dimensional view of the field resulting from the analysis shows the details of the three classical convection phases preconditioning vigourous convection and relaxation in all phases there is strong spatial nonuniformity with mesoscale activity short timescales and sporadic evidence of advective events surface capping intrusions of levantine intermediate water liw deep convection reaching 1500 m was observed in late february by late april the field had not yet returned to its initial conditions strong deficit of liw comparison with available atmospheric flux data shows that advection acts to delay the occurence of convection and confirms the essential role of buoyancy fluxes for this winter the deep mixing results in an injection of anomalously warm water t 0 03 to a depth of 1500 m compatible with the deep warming previously reported

patterns of bottom current flow deduced from dune asymmetries over the gulf of cadiz shelf southwest spain abstract the analysis of dune like morphologies on the gulf of cadiz continental shelf using high resolution seismic reflection profiles and sediment samples reveals a well defined distribution pattern controlled by the area s hydrodynamics these bedforms are considered to be modern features from the holocene and therefore they provide information about the bottom circulatory patterns established over the continental shelf most of the submarine dunes have been identified over a shallow physiographic feature named the barbate high the current flows that generate the bedform fields can be attributed to a complex interaction of several hydrodynamic agents in which the process of current direction reversal related to the tidal cycle in the straits of gibraltar seems to be involved eastward oriented submarine dunes located on the onshore zones of the inner shelf are generated by the atlantic inflow which over these shallow zones is mainly orientated towards the east during high tide conditions in the straits of gibraltar bedforms oriented westwards and west northwestwards in the offshore zones indicate that a previously undescribed flow occurs on the gulf of cadiz continental shelf this flow is attributed to the influence of ebb tidal currents which move preferentially towards the west over these zones as a result of this complex bottom flow pattern a clockwise sand transport pattern over the barbate high is established

a model analysis of the behavior of the mediterranean water in the north atlantic abstract the behavior of the mediterranean water in the north atlantic ocean sector of a global ocean general circulation model is explored starting from its entry point at the strait of gibraltar the analysis focuses primarily on one experiment in which explicit watermass exchange between the mediterranean sea and the atlantic at the strait of gibraltar is permitted the model produces an exchange rate of approximately 1 sv sv 106 m3 s 1 this is comparable to estimates derived from field measurements the density of the mediterranean outflow however is lower than observed mainly because of its high temperature more than 2 c higher than in reality the lower density of the outflow and the model s inadequate representation of the entrainment mixing in the outflow region cause the mediterranean water to settle in a depth range 800 1000 m in the north atlantic about 200 m shallower than observed here an interesting current system forms in response to the intrusion of the mediterranean water i

biological and geochemical signatures associated with the water circulation through the strait of gibraltar and in the western alboran sea previous hydrological investigations of the gibraltar strait have left some questions unanswered as regards the composition of the mediterranean outflow into the atlantic ocean in the present study nutrient oxygen and chlorophyll distributions are used to characterize the main water masses flowing through the strait of gibraltar and the alboran sea with particular reference to levantine intermediate water liw and western mediterranean deep water wmdw high chlorophyll a concentrations reaching 3 g l 1 at the subsurface are observed in the northern part of the anticyclonic alboran sea gyre the salinity subsurface minimum 36 located temporarily in the strait corresponds to high nutrient concentrations 7 8 g at l 1 diagram analysis shows that in the upwelling area off the spanish coast nutrients are largely transported into the photic zone and that photosynthetic nitrate consumption actually takes place consequently the formation of the alboran sea o2 extraminimum can be related to the enhanced new production most of the lowest o2 values 4 00 ml l 1 also correspond to a slight nutrient maximum po4 and no3 comparative diagram analysis of biologically affected parameters oxygen and nutrients versus salinity as a conservative property confirms and expands results from the classical s analysis oxygen and silicate exhibit the best tracer qualities for the circulation pattern demonstrating in particular that during the period of observations water rich in liw feeds the mediterranean outflow

southwest mallorca island a cool water carbonate margin dominated by drift deposition associated with giant mass wasting abstract by means of new high resolution parasound multi channel reflection seismic and multibeam swath bathymetry data we provide new insight into the sedimentation processes at the margin of a cool water carbonate ramp system off southwestern mallorca island western mediterranean sea here we mapped 7 depositional units which we tied to the messinian unconformity the oldest units 1 3 are deposited from late messinian to late pliocene during phases of extreme sea level fluctuations 2 4 ma ago with the global climate cooling when the estuarine water mass circulation switched into an anti estuarine pattern in the mediterranean sea and sea level highstands reached the today level bottom currents started to shape the distal deposits of the cool water carbonate system off southwestern mallorca represented by depositional units 4 7 although sediment supply from the carbonate shelf to the slope is low due to the insignificant input of terrigenous clastics and slow reef growth slope sediments reach thicknesses 140 m our study displays that the accumulation of sediments at the southwestern insular margin was mainly controlled by long lived bottom currents and giant submarine landslides the bottom currents formed elongated mounded drifts that contemporaneously developed in alongslope and upslope direction they are probably controlled by an isobath parallel bottom current in a present water depth of 350 550 m which we associate with the levantine intermediate water liw and an upslope current acting in 250 600 m associated with the algerian mesoscale gyres that enter the balearic straits from se several scarps at the present sea floor indicate the predominance of slope failures in the study area additionally mass transport deposits occur basinwards in almost all depositional units accordingly giant mass wasting events took place from the pliocene into recent times locally above the alongslope drift a field of sediment waves occurs in a water depth of 170 310 m they are oriented slightly oblique to the contour lines with their steep flank facing upslope showing wavelengths of 400 800 m and heights of 10 15 m we suggest that the waves migrate in upslope direction perpendicular to the main isobath parallel flow furthermore the results of this study indicate that sea level fluctuations have only a minor influence on drift deposition instead submarine landslides caused the creation of new drift units they significantly altered the relief of the sea floor and thereby initiate the realignment of the prevailing current pattern the fault scarps and detachment surfaces left behind were the nucleolus for the development of new drift units

late glacial to recent deep sea benthic foraminifera from the northeastern atlantic cadiz gulf and western mediterranean alboran sea paleooceanographic results abstract deep sea benthic foraminifera of the region of water exchange between the mediterranean and the atlantic ocean at the gibraltar strait show significant water mass relationships for the past 18 000 years cores used in this benthic foraminifera analysis were selected according to the context of the distribution of various deep bottom water masses on each side of the gibraltar strait 1 1 on the atlantic side of the strait two cores ks 8228 ks 8229 are located in the present day nadw and one kc 8221 in the upper part of the present mediterranean outflow water 2 2 on the mediterranean side of gibraltar two cores kc 8241 su 8107 are located in the deep water mass and one ks 8230 in the intermediate water mass in the two deep basins 1500 2800 m depth in the gulf of cadiz 1200 1300 m depth in the alboran sea the paleooceanographic changes appear to be in an opposite way for the past 18 000 years the alboran basin shows a paleooceanographic evolution from a well oxygenated nutrient rich environment at about 18 000 yr b p to a nutrient poor oxygen depleted environment from 13 000 to the present time moreover for the time span synchronous with the well known development of sapropels in the eastern mediterranean basins between 10 000 and 7000 yr b p the faunal assemblage shows most unusual characteristics implying drastic environmental conditions conversely in the gulf of cadiz the environment pass as from a biotope occupied by an oxygen depleted nutrient poor water mass at about 18 000 years b p to a biotope occupied by nadw since the younger dryas this agrees with previous data obtained in the northeastern atlantic ocean caralp 1987 in the epibathyal zones 550 800 m depth on both sides of the gibraltar strait paleohydrographic changes do not seem so important according to the present and very late holocene assemblages which are similar on both sides of the strait with a strong east west flow two other stratigraphic episodes have shown the same conditions of water exchanges the end of the isotopic stage 2 and the younger dryas conversely during the last glacial maximum the bolling allerod and the lower holocene westward water fluxes were probably lower at no time the hypothesis of a reversal or a stop in the east west exchanges between mediterranean and atlantic ocean may be justified

trace metal enrichments in waters of the gulf of cadiz spain dissolved cu cd and zn concentrations in continental shelf waters of the gulf of cadiz are much higher than reported for other coastal areas direct observations of the metal enrichments in this region were made in march april 1986 and october 1986 indirect observations in the alboran sea suggest similar enrichments occurred in june 1982 and september 1980 and it is probable that these enrichments are a persistent feature of the region zinc concentrations varied by more than two orders of magnitude between atlantic water entering the strait of gibraltar 1 nmol kg and spanish shelf water up to 160 nmol kg copper and cadmium were also highly enriched in spanish shelf water up to 47 and 1 3 nmol kg respectively and concentrations of these metals varied co linearly with zn chemical profiles show that metal enrichments over the spanish shelf extended from the surface down to about a 45 m depth in contrast ni phosphate silicate and 228ra 226ra all occurred at levels typical of other shelf waters copper cadmium and zinc concentrations in nearby moroccan shelf water were only a factor of 2 to 3 higher than off shore surface atlantic water a steep surface cu cd and zn concentration gradient was observed in the axis of the strait of gibraltar denoting the boundary between off shore atlantic and spanish shelf water metal metal and metal salinity relationships immediately west of the strait of gibraltar show that variations in the composition of surface water can be described by conservative mixing of three sources 1 metal depleted surface atlantic water 2 spanish shelf water highly enriched in cu cd and zn and 3 subsurface north atlantic central water enriched in cd and slightly enriched in ni because the atlantic inflow through the strait is the main water source for the mediterranean sea enrichments in the gulf of cadiz influence metal concentrations of the whole basin some temporal metal variation is observed in spanish shelf water zn concentrations decreased by a factor of two between april and october 1986 although metal concentrations increase systematically with decreasing salinity over the spanish shelf iberian rivers cannot account for the cu cd and zn enrichments an anthropogenic source of any type seems unlikely because the loss of cu cd and zn by entrainment of shelf water through the strait of gibraltar is equivalent to a significant fraction of total metal consumption on the iberian peninsula a diagenetic shelf sediment source may be more plausible but it would have to be of much greater magnitude than on other shelves one mechanism that may enhance metal fluxes from shelf sediments is a coastal metal trap driven by an estuarine type circulation pattern and biological production along the iberian coast this process is illustrated here by a simple box model if this process occurs along the whole iberian peninsula cd enrichments but perhaps only part of the observed cu or zn enrichments could be sustained against the considerable advective metal sink through the strait of gibraltar

role of internal waves in the generation of nepheloid layers on the northwestern alboran slope implications for continental margin shaping 1 the role of internal waves in the sediment dynamics of the northwestern alboran continental slope was investigated in a selected area around the guadiaro submarine canyon nepheloid layer distribution was identified using closely spaced ctd transmissometer profiles collected during two hydrographic surveys a well defined pattern of suspended sediment distribution consisting of surface intermediate and near bottom nepheloid layers was found intermediate and bottom nepheloid layers were always observed within the canyon and on the adjacent continental slope spanning mainly from 200 to 500 m depth in addition a current meter with a turbidimeter was deployed in the lower section of the guadiaro canyon at 600 m depth 25 meters above the seafloor time series analysis indicated that the currents temperature and turbidity within the canyon fluctuate mainly at semidiurnal tidal frequencies suggesting the presence of semidiurnal internal tides affecting the near bottom suspended sediment concentration along the canyon axis high resolution bathymetry from the study area was used to evaluate the internal wave reflection conditions at semidiurnal tidal frequency for the entire continental slope region critical slope conditions were reached on the upper continental slope and along the canyon axis coinciding with the region in which nepheloid layers were observed this region also coincides with a zone of erosion on the upper continental slope of the study area previously identified by hernandez molina 1993 these results indicate that the generation of intermediate and bottom nepheloid layers as well as the erosion and shaping of the northwestern alboran continental slope may result from the interaction of internal waves and the seafloor morphology

yes some of the mediterranean outflow does come from great depth in 1973 stommel et al predicted that the western mediterranean deep water wmdw contributes directly to the mediterranean outflow through the strait of gibraltar strommel et al 1973 hydrographic data obtained in november 1985 showed unambiguous evidence of wmdw west of the major gibraltar sill thus confirming the prediction

accumulation rates of major constituents of hemipelagic sediments in the deep alboran sea a centennial perspective of sedimentary dynamics the accumulation rates of sediment and major constituents in three different geographic areas of the alboran sea have been assessed by means of 210pb and 137cs concentration profiles mixing is present in the top layer of the sedimentary column with mixing coefficients estimated to range from 0 2 to 15 cm2 yr 1 overall apparent sedimentation rates for the last 100 years range from 0 014 to 0 182 g cm 2 yr 1 and show a tendency to decrease with distance to the coast and water column depth however specific characteristics of the sea floor for each physiographic environment govern the actual patterns of sediment accumulation particularly noticeable are the feeding role of submarine canyons the trapping effect of slope terraces and the isolation caused by ridges sediment accumulation induced by turbiditic flows is also observed north of the almeria oran area excess 210pb inventories and surface concentrations reveal a net effect of sediment focussing and point to the role of bottom nepheloid layers in supplying a significant fraction of sediments to the deep areas this is also evidenced by comparison of bottom sediment with the sediment trap data available from the malaga area we estimate that the particle advective input below 30 m above the bottom accounts for as much as 50 70 of the material that is ultimately deposited onto the sea floor the greater abundance of lithogenic material in the malaga zone 80 reflects its larger input in the western alboran sea conversely carbonate contents increase from less than 20 in this area to about 30 in the almeria oran zone reflecting the lesser importance of the dilution by lithogenic components biogenic silica was only detected in some surface samples and no significant preservation was observed below the eh boundary abundance and accumulation rates of organic matter are in accordance with the spatial patterns of primary production in the alboran sea higher in the western part due to the presence of the western alboran gyre however near bottom redistribution leads to the homogenisation of organic matter concentrations in bottom sediments of any given area finally from comparisons with sediment trap data the degradation of organic matter has been estimated to be approximately 30 40 of what reaches the bottom

eddy transport of western mediterranean intermediate water to the alboran sea during the second cruise of the eu funded omega project the towed undulating vehicle seasoar was deployed to survey the upper 350 m of the water column in the eastern alboran sea and extreme western algerian basin with an effective along track resolution of 4 km the data sets enabled a detailed description of the different upper ocean water types and the fronts that separate them the almeria oran front forms at the eastern boundary of the alboran sea gyre system in the upper 150 200 m of the water column and separates waters of predominantly atlantic origin from those formed in the western mediterranean sea below these surface waters but above the levantine intermediate water western mediterranean intermediate waters believed to be formed to the north of the balearic sea are normally observed in this region however to our knowledge this is the first time a discrete eddy of western mediterranean intermediate water a weddy has been described in the extreme western algerian basin repeated surveys of the region allowed us to observe the evolution of the eddy over a period of 40 d a climatological analysis of historical data in the medar medatlas database provides evidence for the repeatability of this observation and the significance of the estimated transport

on the mediterranean water composition abstractthe mediterranean outflow water mow spills from the mediterranean sea east north atlantic basin west off the strait of gibraltar as mow outflows it entrains eastern north atlantic central waters enacw and intermediate waters to form the neutrally buoyant mediterranean water mw that can be traced over the entire north atlantic basin its high salinity content influences the thermohaline properties of the intermediate deep water column in the north atlantic and its dynamics here the composition of mw in its source region the gulf of cadiz west off strait of gibraltar is investigated on the basis of an optimum multiparameter analysis the results obtained indicate that mixing of mow 34 1 0 3 occurs mainly with overlying enacw 57 1 0 8 in a process broadly known as central water entrainment a diluted form 80 of dilution of the antarctic intermediate water aaiw reaches the region and also takes part in mw formation 8 3 0 5 finally the underlying labrador sea wat

another description of the mediterranean sea outflow abstract papers about the outflow in the strait of gibraltar assume that i it is composed of only two mediterranean waters mws the levantine intermediate water liw and the western mediterranean deep water wmdw from the eastern and western basins respectively ii both mws are mixed near 6 w hence producing a homogeneous outflow that is then split into veins due to its cascading along different paths and to different mixing conditions with the atlantic water aw a re analysis of 1985 1986 ctd profiles gibraltar experiment indicates two other mws the winter intermediate water wiw from the western basin and the tyrrhenian dense water tdw basically originated from the eastern basin in the central alboran subbasin these four mws are clearly differentiated roughly lying one above the other in proportions varying from north to south proportions also vary with time so that the outflow can be mostly of either eastern or western origin while progressing westward the mws can still be differentiated and associated isopycnals tilt up southward as much as being in the sill surroundings roughly parallel to the moroccan continental slope where the densest mws are the mws at the sill are thus juxtaposed and they all mix with aw leading to an outflow that is horizontally heterogeneous just after the sill 5 45 w before progressively becoming vertically heterogeneous as soon as 6 15 w there can be little liw and or no wmdw outflowing for a while an analysis of new 2003 2008 time series from two ctds moored ciesm hydro changes programme at the sill 270 m and on the moroccan shelf 80 m confirms the juxtaposition of the mws their individual and generally intense mixing with aw as well as the large temporal variability of the outflow composition only liw and tdw were indicated at the sill while on the shelf only liw tdw sometimes denser there than 200 m below and wmdw were indicated but none of the mws has been permanently outflowing at one or the other place the available data can be analyzed coherently intermediate and deep mws are formed in both basins in amounts that although variable from year to year allow their tracing up to the strait four major mws circulate alongslope counterclockwise as density currents and as long as they are not trapped within a basin which is necessarily the case for the deep mws in the alboran the intermediate mws wiw liw and upper tdw circulate in the north while the deep mws lower tdw and wmdw are uplifted hence relatively motionless and mainly pushed away in the south since both the intermediate and deep mws outflow at the sill they are considered as light and dense mws the light dense mws interface possibly intersecting the aw mws interface in the sill surroundings considering an outflow east of the sill composed of only two light dense homogeneous layers gives significant results across the whole strait the outflow has spatial and temporal variabilities much larger than previously assumed the mws are superposed in the sea and lead at the sill to juxtaposed and vertically stratified suboutflows that will cascade independently before forming superposed veins in the ocean these veins can have similar densities and hydrographic characteristics even if associated with different mws which accounts for the features permanency assumed up to now the outflow structure downstream of the sill depends on its composition upstream and more importantly on that of aw in the sill surroundings where fortnightly and seasonal signals are imposed on the whole outflow

impact of the spatial distribution of the atmospheric forcing on water mass formation in the mediterranean sea the impact of the atmospheric forcing on the winter ocean convection in the mediterranean sea was studied with a high resolution ocean general circulation model the major areas of focus are the levantine basin the aegean cretan sea the adriatic sea and the gulf of lion two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared the first simulation med16 era40 was forced by air sea fields from era40 which is the ecmwf reanalysis the second simulation med16 ecmwf was forced by the ecmwf analyzed surface fields that have a horizontal resolution twice as high as those of era40 the analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns comparing the companion ocean simulation results with available observations in the adriatic sea and in the gulf of lion shows that med16 ecmwf is more realistic than med16 era40 in the eastern mediterranean although deep water formation occurs in the two experiments the depth reached by the convection is deeper in med16 ecmwf in the gulf of lion deep water formation occurs only in med16 ecmwf this larger sensitivity of the western mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time space resolutions of the forcing on the intense winter convection event in winter 1998 1999 the sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography which can only be reproduced in atmospheric models of sufficient resolution thus well positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter

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

western pacific modulation of large phytoplankton blooms in the central and eastern equatorial pacific 1 satellite observations show that large scale phytoplankton blooms increases in chlorophyll occurred in the equatorial pacific in 1998 2003 and 2005 following termination of the three most recent el nino events the occurrence of blooms following successive el nino events cannot be explained by local enhancement of vertical nutrient flux as evidenced by observations of equatorial winds thermocline depth and the depth and strength of the equatorial undercurrent euc which supplies the limiting nutrient iron to the euphotic zone however near the peak of each el nino event late in 1997 2002 and 2004 while the thermocline of the western equatorial pacific was anomalously shallow the flow of the new guinea coastal undercurrent ngcuc which is the primary source of iron enriched waters to the euc intensified and its core shoaled from 200 m to 100 m depth analysis of ngcuc variability using a high resolution terrain following three dimensional ocean circulation model simulation indicates that as the ngcuc shoals and intensifies it develops meanders and eddies that augment coupling of the new guinea shelf and upper slope to the euc we hypothesize that these changes in ngcuc circulation during el nino enhance iron transport from the new guinea margin into the euc and thereby trigger large scale blooms when iron enriched waters subsequently reach the euphotic zone along the equator the threefold to fourfold chlorophyll increases over large regions up to 5 105 km2 must have profound impacts on the equatorial ecosystem and biogeochemical cycles

mesoscale variability in the alboran sea synthetic aperture radar imaging of frontal eddies in autumn 1992 the entire alboran sea western mediterranean was sampled by the spanish r v garcia del cid the incoming jet of atlantic water its associated meandering front and the two big anticyclonic gyres were described from conductivity temperature depth ctd and acoustic doppler current profiler adcp data smaller scale eddies were also observed additionally 36 ers 1 synthetic aperture radar sar scenes were obtained from mid september to mid october the sar images capture these features when wind conditions are suitable the current shear is mainly depicted as narrow lines of low backscatter because of the damping of waves by natural surface films these lines delineate the northern border of both gyres and the beginning of the alongslope algerian current at the eastern limit of the alboran sea adcp observations confirm that lines on sar imagery follow the direction of the surface currents the two gyres present high backscatter values in their center while their frontal boundaries appear modulated by the variation of the marine atmospheric boundary layer stratification due to the surface thermal front sar has observed small spiral eddies that were not evidenced by the almost contemporaneous but too coarse ctd in situ sampling good spatial correspondence between radar detected and in situ measured structures occurs when comparing sar images to the surface dynamic topography rather than strictly surface water characteristics

fingerprinting northeast atlantic water masses using neodymium isotopes dissolved neodymium nd isotopic composition expressed as end has been analysed for 82 seawater samples collected from 13 stations stretching from the alboran sea to the iceland basin the distribution of the end values of water masses was thus investigated for the first time along the western european margin in order to explore whether the water masses flowing in the eastern subpolar and subtropical atlantic reveal distinct isotopic patterns the modified atlantic water maw in the alboran sea displays end values between 9 2 0 2 and 8 9 0 2 that are significantly more radiogenic than those reported in previous studies 10 8 0 2 to 9 7 0 2 suggesting temporal variations in the nd isotopic composition of the water that enters the mediterranean sea from the strait of gibraltar the end value of the underlying modified winter intermediate water wiw has been established for the first time 9 8 0 3 and is compatible with a nd signature acquired from the sinking of maw in the northwestern mediterranean sea within the gulf of cadiz southern mediterranean sea water msw 10 6 0 2 differs slightly from the northern msw 9 9 0 4 owing to a significant contribution of modified east antarctic intermediate water eaaiw 10 9 0 2 in the northeast atlantic the north atlantic current surface water located in the inter gyre region north of 46 n displays end values of between 14 0 0 3 and 15 1 0 3 reflecting the subpolar gyre signature along the western european margin end values of surface water decrease toward the north from 10 4 1 6 to 13 7 1 0 in agreement with the gradual mixing between subtropical and subpolar water at intermediate depth end values decrease from 9 9 0 4 within the gulf of cadiz to 12 1 0 3 within the porcupine seabight indicating a strong dilution of the msw with subpolar water within the rockall trough and the iceland basin the more negative end values at mid depth 13 5 0 3 indicate that the msw has no influence even during periods of low nao index water masses deeper than 1200 m in the northeast atlantic are clearly influenced by the less radiogenic labrador sea water lsw 13 2 0 3 and 14 5 0 3 that mixes locally end between 10 3 0 2 and 11 3 0 3 in the iceland basin with the iceland scotland overflow water isow

determination of the copper isotope composition of seawater revisited a case study from the mediterranean sea abstract a new technique for the determination of dissolved copper isotope composition 65cu of seawater was applied to examine copper sources and internal cycling in the mediterranean sea along the geotraces ga04n transect a succession of chelating resin with nitrilotriacetic acid functional groups and strong base anion exchange resin together with optimization of the multi collector inductively coupled plasma mass spectrometry set up allowed to isolate copper from seawater matrix and to measure the 65cu 63cu ratios in seawater with an external precision of 0 06 2 s d this method was first applied for inter comparison measurements to surface and deep waters sampled at the bermuda atlantic time series station bats in the north atlantic ocean during the geotraces intercalibration cruise 1 disparities in 65cu reported here and in the literature over these samples showed a need to investigate whether a new inter comparison sample should be decided upon or whether the use of uv oxidation can also affect the measurement of 65cu we also measured total dissolved cu concentration dcu t and 65cu for 12 stations in the mediterranean sea the 65cu distribution showed significant variations in the euphotic zone at the chl a maximum and at bottom depths copper isotope ratios ranged from 0 21 to 0 76 0 06 2 s d yielding an average of 0 51 0 20 2 s d n 96 for the mediterranean sea a strong zonation between natural aerosol deposition to the south and anthropogenic aerosol deposition to the north was seen in the sample set dulaquais et al 2017 gerringa et al 2017 rolison et al 2015 natural dust deposits seemed to draw 65cu toward lower values and deeper in the euphotic zone whereas the impact of anthropogenic aerosols seemed restricted to an increase in dcu t at the chl a maximum 65cu showed significant increase which we attributed to scavenging on and or uptake by phytoplankton the isotope signature of cu sources to the mediterranean sea was also investigated and we inferred a significant source of isotopically heavy cu in the gibraltar area potentially originating from a release of cu sulfide leached in the mining area of southern spain i e iberian pyrite belt in rivers and transported to the mediterranean sea in surface by seasonal water mass circulation conversely marine sediments appear to be a source of isotopically light cu to deep waters this study provides new hints on the use of copper isotopes to study sources and sinks of cu in seawater this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

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

the deflection and division of an oceanic baroclinic jet by a coastal boundary a case study in the alboran sea abstract an oceanic baroclinic jet impinging on a coastal boundary represents a particular type of ocean coast interaction this specific oceanographic phenomenon is an example of the stagnation in line flows occurring in fluid dynamics with three additional features rotation stratification and a sloping boundary in this study the authors describe the density vorticity and deformation characteristics of an oceanic jet impinging on a sloping boundary the case study corresponds to the impinging process of the atlantic jet at the african coast alboran sea in the impinging region the acceleration field is divergent related to the fact that the magnitude of the deformation is larger than the magnitude of the rotation it is also found that the stagnation streamsurface does not lie in a vertical plane but tilts in the opposite direction to the tilt of the isopycnals the flow upstream of the stagnation point is characterized by backing speed convergence diffluence and negative streamwise vorticity

variable bottom water in the western mediterranean basin the deep water of the western mediterranean has long been considered to have practically constant values of s and between 1909 1910 the thor expedition and the 1970 cruise of the jean charcot the deep water at more than 1800 m depth showed very little variation the small changes which appeared through the years could be due in part to changes in instrumentation analysis and methods of sampling in 1972 and 1973 during the medoc cruises a bottom layer of 200 300 m thickness was found its temperature and salinity showed a small gradient producing at the bottom an increase of potential temperature of about 0 01 to 0 02 c and an increase in salinities of about 0 010 00 relative to a minimum of and s in the deep water at 1800 2000 m these minima of and s were found to be homogeneous horizontally at all stations occupied in the medoc area and in the ligurian sea in 1973 interestingly the bottom layer was not present in 1974 however in november 1981 during the cruise mediprod iv the variable bottom water was again present extending from the ligurian sea and medoc areas along the western coasts of corsica and sardinia to the eastern alboran sea in most cases the maximum values of and s were recorded at the bottom and were higher than the 1973 values by about 0 03 c and up to 0 0150 00 but with a rather high spatial variability by february 1982 cruise dyome ii the situation had become more complicated not only was a layer of minimum and s present but it was underlain by a layer of maximum and s below which a decrease appeared producing a new minimum at the very bottom in addition a number of stations displayed higher values of by about 0 05 c and of s by about 0 0150 00 in the layers of minimum and maximum characteristics as well as on the bottom in contrast to the situation in 1973 high spatial variability was found in the deep layering the variability may have been due to patchy deep convention activity possibly in the ligurian sea the phenomenon of variable bottom water and the processes which produce it may be relevant to our understanding of water mass formation

distribution of recent benthic foraminifera in shelf carbonate environments of the western mediterranean sea abstract the distribution of recent shallow water benthic foraminifera in surface sediment samples from cool water carbonate environments of the oran bight alboran platform and mallorca shelf in the western mediterranean sea was studied multivariate statistical analyses resulted in the identification of species assemblages representing different environmental settings in all three regions the assemblages show a distinct bathymetric zonation that is mainly attributed to the distribution of rhodoliths and related substrates but also to water turbulence and the availability of food at the sea floor the live assemblages rose bengal stained individuals are characterised by rather low diversity and low standing stocks likely reflecting seasonal population dynamics in the oran bight elevated standing stocks of high food taxa suggest the impact of anthropogenic eutrophication on the near coastal benthic ecosystems of this area the diversity of the dead assemblages is higher than in siliclastic shelf ecosystems of the mediterranean sea but lower when compared to carbonate environments of the levantine sea this regional difference is mainly attributed to lower sea surface temperatures and the lack of lessepsian invaders in the western mediterranean sea in all study areas a distinct faunal change occurs between approximately 80 90 m water depth this change coincides with the lower distribution limit of living rhodoliths at the shelf of mallorca providing coarse grained substrates that are dominated by attached taxa below this depth interval the fauna shows regional differences depending on the grain size and related accumulation of organic material fine grained substrates with infaunal niches are restricted to low energy environments on the deeper shelf southwest off mallorca

observation of a western alboran gyre migration event abstract in the western alboran sea light atlantic water and dense mediterranean waters meet this gives rise to intense density fronts and energetic mesoscale features such as two semi permanent anticyclonic vortices the western and eastern alboran gyres however the circulation in the alboran sea is strongly varying in time with episodes where neither the western alboran gyre nor the eastern alboran gyre are present in october 1996 four consecutive high resolution surveys of the western alboran gyre wag were carried out and lagrangian floats were released during the first survey the western alboran sea was occupied by the wag surrounded by the atlantic jet the following surveys showed the wag drifting eastward beginning a wag migration event as confirmed 15 days later by the lagrangian float tracks and the sst images to replace the old gyre one month later a new gyre was formed analysis of adcp velocities sst images and ts properties show a change between the first and the second survey in the atlantic inflow through the strait of gibraltar the relationships between this change in the atlantic inflow a drop in the atmospheric pressure at ceuta the tidal regime and the wag migration are discussed the existence of a high resolution sampling in space together with the possibility of addressing the temporal variability has allowed us to describe in detail and for the first time the time evolution of the western alboran sea during a wag migration event relating the migration to changes in the inflow through the strait of gibraltar