closure of a seaway stratigraphic record and facies guadix basin southern spain during the late tortonian upper miocene the guadix basin in s spain formed one of the betic corridors that connected the mediterranean sea with the atlantic ocean the closure of this connection occurred in a series of steps documented by three sedimentary units a lower unit consisting of basinal marls shallow water calcarenites and sands records the formation of a wide seaway during deposition of the following unit this narrowed to a strait no more than 2 km in wide triggering an intensification of currents that caused migration of submarine dunes preserved as giant cross beds in bioclastic sands and conglomerates current flowed from the mediterranean to the atlantic the third unit constitutes the youngest marine episode of the filling of the guadix basin at this stage the connection between the mediterranean sea and the atlantic ocean was broken and a system of coastal coral reefs was established in the northern part of the basin

jebar bottom pressure torque and gulf stream separation abstract a diagnostic finite element barotropic ocean model has been used to simulate the mean circulation in the north atlantic with the inclusion of the joint effect of baroclinicity and relief jebar the gulf stream is found to separate at the correct latitude 35 n off cape hatteras results suggest that the jebar term in three key regions offshore of the separation point in the path of the main jet along the slope region of the north atlantic bight and in the central irminger sea is crucial in determining the separation point the transport driven by the bottom pressure torque component of jebar dominates the solution except in the subpolar gyre and is also responsible for the separation of the gulf stream excluding high latitudes in the deep water formation regions density variations in the upper 1000 m of the water column govern the generation of the necessary bottom pressure torque in our model examination of results from the world ocean circulation experiment community modelling

observations of east coast upwelling conditions in synthetic aperture radar imagery seasonal coastal upwelling in the u s mid atlantic coastal ocean normally occurs during the summer months because of generally alongshore southerly wind episodes southerly winds force an offshore surface ekman flow over the inner continental shelf colder and nutrient rich waters from below upwell toward the surface replacing offshore flowing surface waters synthetic aperture radar sar observations from the european remote sensing ers satellite ers 2 before and after upwelling favorable wind episodes in early summer 1996 along the new jersey coast are presented lower backscatter conditions appearing in the sar imagery after the onset of upwelling demonstrate the influence of the upwelling regime on the sea surface roughness satellite sea surface temperature sst observations and in situ sea temperature vertical profiles confirm upwelling conditions three key mechanisms are suggested to explain the lower radar returns observed under upwelling conditions an increase in the atmospheric marine boundary layer stability an increase in the viscosity of surface waters and the presence of biogenic surfactants in the upwelling region

modeling substorm current systems using conductivity distributions inferred from de auroral images images of auroral emissions observed with dynamics explorer 1 de 1 are used to calculate ionospheric conductivities over the polar region the combination of ground based magnetometer data and the inferred conductivities enables us to estimate on a global scale the distributions of ionospheric electric fields and currents and field aligned currents as well as the joule heating production rate with a time resolution of 12 min although our inference of the conductivity distribution requires further improvements the following conclusions may be drawn from this work 1 the westward electrojet is in general collocated with the region of high auroral luminosity while the region of relatively low luminosity in the evening sector is collocated with the eastward electrojet 2 the upward field aligned currents exist in the brightest auroral region on the poleward side of the evening auroral oval and on the equatorward side of the morning oval however the magnitudes of these upward currents are not in proportion to the auroral luminosities suggesting that the characteristic energies of precipitating electrons carrying the upward currents and generating the auroral luminosities may be different 3 a significant amount of ionospheric currents can flow in regions where there are no bright auroral emissions an example of this effect is found over the poleward half of the westward electrojet in the morning sector where the electric field is the main contributor to the ionospheric currents 4 the distribution of calculated field aligned currents displays many localized structures which characterize the development of the substorm current system previous satellite observations may represent gross time averages of such complicated distributions

climate stability in central anatolia during the messinian salinity crisis abstract deposition of large amounts of evaporites and erosion of deep canyons within the mediterranean basin as a result of reduced basin connectivity with the atlantic ocean and the epicontinental paratethys sea characterized the messinian salinity crisis msc 5 97 5 33 ma the influence of the msc on mediterranean environmental conditions within the basin itself has been intensely studied from marine records but reconstructing the impact of the msc on circum mediterranean continental climate has been hampered by the absence of continuous sedimentary archives that span the duration of the event here we report results of a continental record of carbon 13c and oxygen 18o isotopes from lake carbonates framed by new magnetostratigraphic and 40ar 39ar dating as well as by existing mammal stratigraphy kangal basin central anatolia the sampled section records continuous fluvio lacustrine sedimentation from 6 6 ma to 4 9 ma which spans the msc and the miocene pliocene boundary this dataset so far represents the only continuous continental paleoenvironmental record of the msc in the circum mediterranean realm the kangal basin isotope record indicates a low degree of evaporation furthermore covariance between 13c and 18o suggests a coupling between lake water balance and biologic productivity variations in 13c and 18o therefore likely reflect changes in the amount of incoming precipitation rather than changes in 18o values of incoming precipitation the most prominent spike in 13c and 18o occurs during the acme of the msc and is therefore interpreted to have resulted from a decrease in the amount of incoming moisture correlative to a period of vigorous erosion and sea level lowering in the mediterranean basin major sea level lowering of mediterranean basin waters during the acme of the msc could have therefore led to slightly dryer conditions over anatolia which is also suggested by modeling studies overall changes in 13c and 18o values are small therefore we surmise that the msc had limited effects on the paleoenvironmental and paleoclimatic conditions in the anatolian interior

enhancement of wind driven upwelling and downwelling by alongshore bathymetric variability steady wind driven flow along a shelf of changing width is described with a frictional barotropic model valid in the limit of small rossby and burger number in these limits an alongshore wind drives enhanced onshelf transport in a coastal ocean if the shelf widens downwind and the change in shelf width only affects the flow in the direction of kelvin wave propagation downwave from the change in shelf width there is enhanced onshore transport of cold nutrient laden bottom water if the winds favor upwelling and the shelf narrows in the direction of kelvin wave propagation this enhanced transport extends a considerable distance away from the change in shelf width but becomes concentrated near the shelf break far from the change in width isobath curvature on the scale of the shelf width significantly modifies local cross shelf transport the cross shelf transport of nutrient rich water during upwelling is expected to be enhanced from point eugenia to la jolla san luis obispo to monterey and point reyes to cape mendocino on the west coast of north america

climate variability during the last 2000 years in the tagus prodelta western iberian margin benthic foraminifera and stable isotopes abstract a high resolution sedimentary sequence recovered in the tagus prodelta has been studied in order to reconstruct paleoenvironmental conditions on the western iberian margin portugal through the last ca 2000 years including the historical time when anthropogenic influence became significant benthic foraminiferal assemblages as well as stable isotopic composition of the benthic foraminifera uvigerina sp were investigated considerable environmental fluctuations are indicated by all these proxies between ad 400 and 1400 1550 550 cal year bp during a period including the medieval warm period bottom water temperatures as reconstructed from uvigerina sp were high 13 3 c in this time interval species typical for shelf environments cassidulina laevigata nonion asterizans and hyalinea balthica maintained a high abundance along with opportunistic species like bolivina dilatata and bolivina pacifica the most abundant species in the record a faunal change occurred at around ad 1300 1400 650 550 cal year bp at the beginning of the little ice age after this the environment became more variable in the tagus prodelta as reflected by a decrease in faunal diversity and benthic foraminiferal composition and flux values after about ad 1800 150 cal year bp bottom water temperatures rose to maximum values of the record the disappearance of certain benthic taxa and the appearance of the species saidovina karreriana indicate a change in bottom water conditions during the last 100 years possibly induced by anthropogenic pollution

modeling study of variable upwelling circulation in the east china sea response to a coastal promontory abstracta three dimensional high resolution numerical model is used to investigate processes and dynamics of an intensified upwelling that is induced by a coastal promontory over the east china sea ecs shelf the center of the intensified upwelling around the promontory has been constantly observed but so far it has been dynamically unexplained forced by an idealized southeasterly wind stress the model results well capture the observed upwelling at the lee of the coastal promontory the intensified upwelling is formed by a strengthened shoreward transport downstream of the promontory as the upwelling jet veers shoreward the jet is mainly controlled by a cross shore geostrophic balance and is largely modulated by both centrifugal acceleration associated with nonlinear advection and by bottom stress the strengthened shoreward transport is mainly attributed to the cross shore geostrophic current that is induced by a countercurrent negative pressure gradient force pgf and partly attributed to th

ground based imaging of detached arcs ripples in the diffuse aurora and patches of 6300 a emission a period of coordinated multidiagnostic observations of the subauroral ionosphere conducted in april 1985 resulted in a series of optical and plasma characterizations of three distinct phenomena arcs detached from the diffuse aurora undulations in the equatorward edge of the diffuse aurora and isolated patches of emission in the f region trough the optical features were observed by the 6300 a imaging system in boston university s mobile ionospheric observatory located at the millstone hill observatory plasma observations were made by the millstone incoherent scatter radar air force geophysics laboratory satellite radio beacon polarimeters and the defense meteorological satellite program dmsp energetic particle detectors the detached arc observations showed that strong f region enhancements occured in both 6300 a emission and total plasma content suggesting an electron precipitation source essentially similar to the plasma sheet population that causes the diffuse aurora and the poleward wall of the f region trough the rippled features along the equatorward edge of the diffuse aurora were associated with strong electric fields and large radial ion temperature gradients topics discussed in detail in a companion paper the isolated and long lived patches of 6300 a emission have no corresponding f region plasma enhancements but are associated with enhanced radar returns from the e region nearly simultaneous dmsp observations point to the importance of ion precipitation effects as a cause for these f region optical and e region plasma enhancements the entire set of observations detached arc ripples and patches show that ground based imaging and radio techniques can provide detailed spatial and temporal coverage of phenomena hitherto observed by satellite only

the mesolithic neolithic transition in southern iberia new data and a review of historiographic information from neolithic sites of the malaga and algarve coasts southern iberian peninsula and from the maghreb north africa reveal the existence of a neolithic settlement at least from 7 5 cal ka bp the agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the mesolithic populations the timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems including upwelling intensity sea level changes and increased aridity in the sahara and along the iberian coast these changes likely impacted the subsistence strategies of the mesolithic populations along the iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the mesolithic neolithic transition the rapid expansion and area of dispersal of the early neolithic traits suggest the use of marine technology different evidences for a maghrebian origin for the first colonists have been summarized the recognition of an early north african neolithic influence in southern iberia and the maghreb is vital for understanding the appearance and development of the neolithic in western europe our review suggests links between climate change resource allocation and population turnover

dynamics of intensified downwelling circulation over a widened shelf in the northeastern south china sea abstractthis study reveals the dynamics behind the intensified downslope cross isobath transport over a widened shelf narrowing downwave in the northeastern south china sea nscs during a downwelling event utilizing a three dimensional numerical model over an idealized nscs shelf this study identified the forcing process and derived an analytical understanding of the invoked dynamics for the intensified downslope cross isobath transport this study found that the transport was formed by an amplified geostrophic transport because of an increased positive along isobath pressure gradient force pgf py and by an enhanced bottom ekman transport due to converging flow over the widened shelf based on the depth integrated vorticity dynamics py was linked with net frictional stress curl in the water column and the curl was primarily associated with the shear vorticity field induced by downwelling jet the increased positive vorticity seaside of the jet provided positive py for the downslope geostrop

progress on upwelling studies in the china seas east asian marginal seas surrounding china exhibit rich ocean upwelling mostly in response to the southwesterly summer monsoon upwelling in the china seas namely the south china sea the taiwan strait the east china sea the yellow sea and the bohai sea has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem socioeconomic and climate impacts this paper reviews the progress of upwelling studies in the china seas since the year 2000 by presenting the principal characteristics and new understanding of 12 major upwelling regions in the china seas upwelling exhibits long term variability at intraseasonal to multi decadal scales as well as short term variability frequently caused by tropical cyclones it is also associated with the el nino southern oscillation local environmental variation and biogeochemical factors the coastal upwelling around hainan island and the upwelling or cold dome northeast of taiwan island are specifically highlighted because they have attracted great interest for decades this paper summarizes upwelling mechanisms in terms of wind topography tide stratification and background flow with applications mostly to the china seas finally we propose some topics for future upwelling research i e potential intensification of coastal upwelling under global climate change downwelling intrusion of upwelling into coastal embayments and the influence of upwelling on fishery and biogeochemical processes

high altitude energy source s for stable auroral red arcs stable auroral red sar arcs have been viewed across the midlatitude night sky with interest since their discovery in 1956 this relatively late discovery compared to the poleward aurora is a direct consequence of the subvisual levels of the delicate and diffuse light that makes up the sar arc except in rare instances when the emissions actually crossover the threshold to visible levels optical instruments are required to register their presence and document their morphology and occurrence frequency sar arcs are seen as relatively featureless slowly changing bands of red light that can extend across the entire night sky early observations from the ground and from satellites established the relationship between sar arcs and magnetic disturbances in near earth space involving the ring current a population of high energy ions trapped in the earth s magnetic field the long lived soft red glow of sar arcs reflects the slow energy loss from the ring current ions as they bounce back and forth in the earth s confining field geometry but the exact sequence of physical processes that feed a portion of the ring current energy to the sar arc region is a matter of continuing debate the midlatitude location of the sar arc bands mirrors the high altitude location of the outer portion of the ring current torus but exactly how this positioning is related to gradients or enhancements in the high altitude extension of the cold ionospheric plasma remained an open question our knowledge of sar arcs and associated signatures now spans more than two full solar cycles detailed observations of the high altitude space environment overlying the sar arc region have been made indicating that heavy ions from the lower atmosphere energized by the solar wind interaction with the magnetosphere play an important role in the sar arc process sophisticated models of the coupled high and low altitude regions involved in sar arc formation paint an interesting picture of the flow of energy between the atmosphere and near earth space this energy flow culminates in the sar arc s glowing red bands which act in turn as sensitive markers of the interaction regions and processes this emerging view of the sar arc process and the new observational information that provided the underpinnings of its development from a rich framework of past theoretical and observational work is the subject of the present review

upwelling off yangtze river estuary in summer 1 the mechanisms of upwelling off the yangtze river estuary yre and in the adjacent waters in boreal summer are studied using numerical modeling first the persistent feature of this phenomenon is confirmed using cruise observations satellite sea surface temperature sst and sst climatologic data then the masnum marine science and numerical modeling wave tide circulation coupled numerical model is employed to simulate the upwelling patterns on the basis of the simulation a set of numerical experiments are designed to explore the main mechanisms inducing the upwelling the results suggest that tidal mixing plays a predominant role in inducing the upwelling in offshore waters strong tidal mixing results in considerable horizontal density gradient across tidal fronts upwelling is induced as a branch of the secondary circulation which is stimulated by the cross frontal density gradient topography also exerts profound influences on upwelling by steering bottom currents to ascend upward and regulating tidal fronts in both location and intensity besides the tides and topography other dynamical factors also alter the strength of upwelling locally the yangtze river discharge yrd and taiwan warm current twc account partly for the upwelling off the yre and near zhoushan islands respectively the influence of wind on upwelling is small in the coastal waters near zhoushan islands the wind forcing exerts negative influences on upwelling by weakening the encroachment of twc onto the continental shelf which may exceed the positive effects of ekman pumping

diatoms as upwelling and river discharge indicators along the portuguese margin instrumental data linked to proxy information high resolution diatom and phytolith quantitative and assemblage analyses have been conducted on two box cores from the tagus pro delta sw portuguese margin in order to compare these common palaeoceanographic proxies to instrumental data describing the upwelling regime and the freshwater input of the tagus river the western portuguese margin is affected by seasonal coastal upwelling controlled by northerly winds and by strong freshwater input through the tagus river which is controlled by precipitation over the whole iberian peninsula for both upwelling and freshwater input instrumental data such as river flow and an upwelling index are available for the last 100 and 50 yr respectively diatoms and phytoliths are used as proxies for salinity and productivity changes resulting from river input and upwelling variability comparison of the proxy and instrumental records confirms that diatom abundance and in particular the genus chaetoceros ehrenberg traces the main periods of intense upwelling

an upwelling case study on florida s west coast using a combination of satellite sea surface temperature imagery in situ currents temperature and sea level data and a numerical circulation model we describe an upwelling event observed along florida s west coast although ubiquitous features of continental shelves descriptions of coastal upwellings or downwellings are generally complicated by the continuum of processes in which they occur for the case study presented the winds were light and the baroclinic background currents were steady for several days prior to the event these conditions allow the evolution of a specific winddriven upwelling event to be viewed as an initial value problem the data and the numerical model analysis show that the route of adjustment by the sea level and currents is a classical ekman geostrophic one sea level drops due to an offshore ekman transport causing a geostrophic alongshore jet and the associated onshore flow within the bottom ekman layer accounts for the appearance of cold water at the surface this surface manifestation occurs as an elongated feature centered about the 25 m isobath that spans roughly half of the florida peninsula from just north of tampa bay to key west the coldest water is observed offshore from tampa bay and we explain this region of locally maximum upwelling on the basis of the coastline and isobath geometries

correlation of late miocene to early pliocene sequences between the mediterranean and north atlantic ocean drilling program odp site 982 in the north atlantic contains a complete latest miocene to early pliocene section that was tuned to the astronomical timescale by correlating the record of gamma ray attenuation gra bulk density to summer insolation at 65 n and the benthic 18o signal to orbital obliquity for the interval from 4 6 to 7 5 ma the astronomical tuning of the site 982 record permits a direct bed to bed correlation to the cyclostratigraphy of messinian sections in the mediterranean krijgsman et al 1999a 2001 the benthic 18o signal at site 982 records a latest miocene glacial period that lasted from 6 26 to 5 50 ma and consisted of 18 glacial to interglacial oscillations that were controlled by the 41 kyr cycle of obliquity although the intensification of glaciation at 6 26 ma may have contributed to the restriction of the mediterranean it preceded the depositional onset of the lower evaporite unit at 5 96 ma by some 300 kyr the transition from stage tg12 to tg11 at 5 5 ma marks the end of the latest miocene glacial period and precedes the miocene pliocene boundary by 170 kyr although benthic 18o values are relatively low and 18o of bulk carbonate reaches a minimum at the miocene pliocene boundary at 5 33 ma there is no single event that would indicate deglaciation and sea level rise as the cause of the reflooding of the mediterranean we conclude that glacioeustatic changes alone were not responsible for either the start or end of evaporite deposition during the messinian suggesting that tectonic or local climate changes in the mediterranean region were the dominant cause s

dynamics of wind driven upwelling off the northeastern coast of hainan island both observational and reanalysis sea surface temperature data reveal that upwelling occurs frequently off the northeastern coast of hainan island downstream of the change in topography off tongluo cape which cannot be attributed to the along shelf wind alone to identify dynamics of the upwelling we conduct a numerical experiment using an idealized topography that is simplified from the actual topography off the eastern and northeastern coasts of hainan island the result indicates that the upwelling downstream of the change in topography is associated with onshore cross isobath transport analysis of the vertically integrated momentum balance shows that the upwelling linked onshore transport is primarily intensified by the along isobath barotropic pressure gradient force pgt but is weakened by the along isobath baroclinic pressure gradient force pgc the along isobath pgt is linked to the advection of relative vorticity the bottom stress curl and the gradient of momentum flux in vorticity equation on the other hand the pgc related process is diagnosed by potential vorticity pv balance similar to the negative pv term from wind stress the negative pv terms of the joint effect of baroclinicity and relief and the baroclinic bottom pressure torque weaken the upwelling linked onshore transport downstream of the change in topography the onshore transport is enhanced by the positive pv from bottom stress in addition the cross isobath forces play an important role in upwelling intensification in the shallow nearshore region

physical oceanography of the western iberia ecosystem latest views and challenges the present review is focused on the mesoscale physical processes recognized in the western iberia ecosystem complementing earlier reviews dedicated to larger scales recent studies support the idea that the mesoscale processes superimposed on the larger scale variability are the major factor controlling the ecosystem functioning in the region a complex structure of interleaved alongshore slope shelf and coastal currents that interact with eddies buoyant plumes upwelling filaments and fronts surface layer expressions of the subsurface circulation and internal waves is revealed by the latest research all of these contribute in different ways to have an effect on the ecosystem the supposedly less variable winter circulation also exhibits significant mesoscale activity in the form of eddy shedding from the poleward slope current intermittent upwelling events and transient nearshore poleward flows the present incomplete knowledge of this complex system presents a number of challenges and questions that must be addressed if we are to arrive at a satisfactory understanding and predictive capability for the system as a whole 2007 elsevier ltd all rights reserved

position of the polar front along the western iberian margin during key cold episodes of the last 45 ka 1 this paper documents the migration of the polar front pf over the iberian margin during some of the cold climatic extremes of the last 45 ka it is based on a compilation of robust and coherent paleohydrological proxies obtained from eleven cores distributed between 36 and 42 n planktonic 18o globigerina bulloides ice rafted detritus concentrations and the relative abundance of the polar foraminifera neogloboquadrina pachyderma sinistral were used to track the pf position these three data sets compared from core to core show a consistent evolution of the sea surface paleohydrology along the iberian margin over the last 45 ka we focused on five time slices representative of cold periods under distinct paleoenvironmental forcings the 8 2 ka event and the younger dryas two recent cold events occurring within high values of summer insolation heinrich events 1 and 4 reflecting major episodes of massive iceberg discharges into the north atlantic and the last glacial maximum typifying the highest ice volume accumulated in the northern hemisphere for each event we generated schematic maps mirroring past sea surface hydrological conditions the maps revealed that the polar front presence along the iberian margin was restricted to heinrich events the sea surface conditions during the last glacial maximum were close to those at present day except for the northern sites which briefly experienced subarctic conditions

productivity and paleoceanographic implications on the tore seamount iberian margin during the last 225 kyr foraminiferal evidence foraminifera counts and climatic assemblages from the tore seamount are used to approach the glacial and interglacial changes in temperature and productivity on the iberian margin over the last 225 kyr chronostratigraphy is based on globigerinoides ruber and globigerina bulloides oxygen isotopes and supported by foraminifera and carbonate stadial fluctuations foraminifera indicate cooling from late interglacial stage 5 to the beginning of termination i ti neogloboquadnna pachyderma s reflects cold conditions during glacial stages 4 2 in contrast glacial stage 6 is dominated by warmer n pachyderma d and dutertrei and a restricted arctic assemblage past sea surface temperatures confirm the general cooling reaching 4 3 c simmax 28 during stage 2 multiple productivity proxies such as organic carbon productivity related foraminifera and 13c constrain the changes observed a productivity increase occurs after interglacial stage 5 enhanced from late glacial stage 3 to ti present day satellite detected phytoplankton plumes off portugal would have accounted in the past glacial stages for the general productivity increase over the tore on top of this welldefined peaks of organic carbon and productivity related foraminifera correspond with heinrich events 1 4

high frequency surface water changes in the tagus prodelta off lisbon eastern north atlantic during the last two millennia abstract a high resolution sedimentary sequence recovered from the tagus prodelta has been studied with the objective to reconstruct multi decadal to centennial scale climate variability on the western iberian margin and to discuss the observations in a wider oceanographic and climatic context between ca 100 bc and ad 400 the foraminiferal fauna and high abundance of globorotalia inflata indicate advection of subtropical waters via the azores current and the winter time warm portugal coastal current between ca ad 400 and 1350 encompassing the medieval climate anomaly mca enhanced upwelling is indicated by the planktonic foraminiferal fauna in particular by the high abundance of upwelling indicator species globigerina bulloides relatively light 18o values and high sea surface temperature sst reconstructed from foraminiferal assemblages point to upwelling of subtropical eastern north atlantic central water between ca ad 1350 and 1750 i e most of the little ice age relatively heavy 18o values and low reconstructed sst as well as high abundances of neogloboquadrina incompta indicate the advection of cold subpolar waters to the area and a southward deflection of the subpolar front in the north atlantic as well as changes in the mode of the north atlantic oscillation in addition the assemblage composition together with the other proxy data reveals less upwelling and stronger river input than during the mca stronger azores current influence on the iberian margin and strong anthropogenic effect on the climate after ad 1750 is indicated by the foraminiferal fauna the foraminiferal assemblage shows a significant change in surface water conditions at ca ad 1900 including enhanced river runoff a rapid increase in temperature and increased influence of the azores current the tagus record displays a high degree of similarity to other north atlantic records indicating that the site is influenced by atmospheric oceanic processes operating throughout the north atlantic as well as by local changes

remote sensing observation and numerical modeling of an upwelling jet in guangdong coastal water 1 an upwelling event that occurred in guangdong coastal water on july 14 16 2003 is observed by using satellite multisensor data including the moderate resolution imaging spectroradiometer modis sea surface temperature sst and quikscat ocean surface winds successive modis sst images reveal expansion process of a jet like upwelling cold water body in surface layer the regional ocean model system roms is used to explore the upwelling dynamics the modeling successfully reproduces the jet like shape of the surface upwelling water as well as the upwelling developing process analyses of modeling momentums reveal that the large offshore transport appeared on the west side of honghai bay as a result of high alongshore pressure gradient and nonlinear advections and the enhanced horizontal advection also played an important role in developing the prominent upwelling in honghai bay a numerical experiment is conducted to confirm that it was the wind driven upwelling rather than the wind induced vertical turbulent mixing that induced the surface cold water further numerical analyses suggest that strong internal tides occurred in honghai bay caused by the local bottom topography the interaction between the upwelling and internal tides enhances the bottom water uplifting the offshore expansion of the upwelling water is controlled by the cross shore topography slope a gentle and offshore extended slope helps the bottom water climbing up to the surface in a wide range in cross shore direction whereas a steep and narrow slope restricts the expansion of the upwelling water and confines the cold water in a narrow band along the shore

the messinian marine to nonmarine gypsums of jumilla northern betic cordillera se spain isotopic and sr concentration constraints on the origin of parent brines the origin of the messinian hoya de la sima hs gypsum betic foreland is constrained using 87sr 86sr 34s sr concentration and petrographic data the lower and middle hs units consist of subaqueous vertically aligned and stromatolitic selenites the latter containing unusual microbial depositional textures the upper unit consists of very shallow water bioturbated lenticular gypsum with paracamelus ichnites 87sr 86sr and 34s indicate precipitation from predominantly marine waters with upward increasing continental influence mixing models between messinian seawater and continental water that dissolved triassic evaporites show that the percentages of seawater required to explain the measured 87sr 86sr are analogous to the percentages obtained using 34s supporting precipitation from such mixtures 87sr 86sr and 34s of lower hs selenites resemble those of the primary lower gypsum plg of the messinian salinity crisis msc in both cases indicating precipitation from seawater continental water mixtures in which most sr and so4 were supplied by messinian seawater in the lower hs selenites sr concentrations indicate contributing continental waters with sr ca ratios similar to seawater however sr concentrations of plg selenites from other betic basins bajo segura sorbas indicate parent waters with sr ca ratios lower than seawater if the sr contents of the betic plg selenites are representative it is unlikely that the lower hs selenites represent the plg however we cannot completely discard that option since different lpg subbasins could have had variable sr ca the hs gypsums formed coevally to diapirism of triassic evaporites in a restricted lagoonal basin developed during or slightly after a phase of strike slip faulting in the betic cordillera more general implications of this work are that sr concentrations combined with 87sr 86sr and 34s data provide key constraints on the origin of parent brines and using sr concentrations as paleosalinity proxy in gypsum precipitated from seawater continental water mixtures is inconclusive because they largely depend on the initial sr ca ratio of the brine this study also illustrates that the electron microprobe is ideal to obtain reliable spatially resolved sr concentration data in selenitic gypsum these data in combination with fluorescence petrography provide valuable criteria to discriminate primary depositional from diagenetic gypsum a critical step in the interpretation of geochemical data

late miocene turnover in the spanish mammal record in relation to palaeoclimate and the messinian salinity crisis abstract the latest miocene and earliest pliocene is a period of marked changes in geography and climate in the circum mediterranean area its geographical situation gives spain a key position and its fossil mammal record reflects these important geographical and climatic changes particularly well the spanish mammal record shows a gradual change of composition towards the typical pleistocene and recent fauna marked by several extinction and dispersal events these events have the effect that northern eurasian elements increase while taxa that locally go extinct may live on in tropical areas superposed on this large scale trend there are some events of short lived incursions of animals of african or south asian origins which seem to reflect a short reversal of this tendency and temporary geographical changes related to the messinian crisis these latter incursions are detected very well in spain but also in other parts of southern europe the messinian salinity crisis is caused by interplay of tectonics and global sea level variations which in turn depend on climate while some of these changes were permanent causing the replacement of central italian insular faunas by mainland faunas others were temporary probably allowing the short lived incursions of african mammals into sw europe and certainly allowing for mammals to reach the balearics corsica and sardinia we document an important event around 6 1 ma of mammals adapted to dry or open environments dispersing from africa and se europe to sw europe during the messinian desiccation phase animals adapted to more humid environments reached some of the west mediterranean islands suggesting that at least during part of the desiccation phase a part of the former sea bottom was not desertic between 6 3 and 5 3 ma tectonics united the island of toscany to the european mainland thereby closing a seaway of some 10 km wide and 100 m deep

magnetostratigraphic biostratigraphic and stable isotope stratigraphy of an upper miocene drill core from the sale briqueterie northwestern morocco a high resolution chronology for the messinian stage we report a high resolution stable isotope carbonate magnetostratigraphic and biostratigraphic record from a 175 m drill core from the sale briqueterie which is part of the bou regreg section in northwestern morocco the sale drill core spans the interval from paleomagnetic chron c4n partim to c3r earliest gilbert which represents the time leading up to and including the isolation and desiccation of the mediterranean i e the messinian salinity crisis during chrons c3an and c3ar 6 935 to 5 894 ma the isotope and carbonate signals display quasi periodic variations with estimated periods of 40 and 100 kyr respectively we interpret the 40 kyr 18o variations as reflecting changes in global ice volume caused by obliquity induced changes 41 kyr in solar insolation in polar regions the 100 kyr carbonate variations probably represent long term modulation of the amplitude of the precessional cycle 21 kyr which is not resolved by our sampling frequency the cyclic nature of the oxygen isotope signal permits us to extend the isotope nomenclature of shackleton et al 1994a from stage tg24 in chron c3r earliest gilbert to stage c3ar 18o 18 at the base of chron c3ar 6 935 ma a major change in paleoceanographic conditions is recorded across the tortonian messinian boundary which we correlate to chron c3bn at 7 04 ma benthic foraminiferal 18o values increased by an average of 0 4 in two steps at 7 17 ma and 6 8 ma and 13c values decreased by 0 7 0 8 between 7 1 and 6 8 ma representing the late miocene carbon shift the first step in 18o values coincides with an inferred reversal in deep water circulation through the rifian corridor and the second correlates with the base of the tripoli formation and onset of crisis conditions in the mediterranean we suggest that the increase in 18o values represents at least in part an increase in global ice volume that lowered sea level and contributed to the establishment of a negative water budget in the mediterranean average 18o values remained high throughout most of chrons c3ar and c3an reaching maximum 18o values during isotope stages tg20 and 22 in chron c3r earliest gilbert the glacio eustatic falls associated with these events may have resulted in the complete isolation of the mediterranean from the world ocean shackleton et al 1994a following stage tg12 in the sale record there exists a trend toward progressively lower 18o values that may represent a series of marine transgressions that eventually reflooded the mediterranean and ended the salinity crisis

upwelling induced by the frictional stress curl and vertical squeezing of the vortex tube over a submerged valley in the east china sea we conducted a process oriented modeling study to investigate the characteristics and dynamics of the prominent upwelling over a vast submerged valley in the east china sea ecs the valley is inversely funnel shaped with the west bank and the east bank oriented in the north south direction a cross bank upward transport occurred along the west bank it intensified northward and peaked around the head of the valley an along bank southward pressure gradient force pgf formed the cross bank geostrophic transport for the upwelling over the valley the pgf reached its maxima at the head of the valley our momentum and vorticity dynamic analyses revealed that a bottom stress curl mainly contributed the pgf along the west bank at the same time both the bottom stress curl and the nonlinear vorticity advection contributed to the pgf around the head the bottom stress curl was due to the bottom shear vorticity of the coastal current and the curvature vorticity around the head the nonlinear vorticity advection formed because of the vertical squeezing of vortex tube as the current flowed over the valley the nonlinearity mainly affected the pgf around the head whereas the bottom stress curl contributed to the pgf over the entire valley the ratio of the nonlinear to frictional contributions to the pgf increased as the coastal current intensified our study demonstrates that the pgf that drives the upwelling over the valley is the combined result of the nonlinearity due to vertical squeezing of vortex tube and bottom frictional effects

shallow marine sediment cores record climate variability and earthquake activity off lisbon portugal for the last 2000 years abstract sea surface temperature sst river discharge and biological productivity have been reconstructed from a multi proxy study of a high temporal resolution sedimentary sequence recovered from the tagus deposition center off lisbon portugal for the last 2000 years sst shows 2 c variability on a century scale that allows the identification of the medieval warm period mwp and the little ice age lia high iron fe and fine sediment deposition accompanied by high n alkane concentrations and presence of freshwater diatoms during the lia 1300 1900 ad science 292 2001 662 suggest augmented river discharge whereas higher total alkenone concentrations point to increased river induced productivity during the mwp 550 1300 ad science 292 2001 662 larger mean grain size and low values of magnetic susceptibility and concentrations of fe n alkanes and n alcohols are interpreted to reflect decreased runoff at the same time increased benthic and planktonic foraminifera abundances and presence of upwelling related diatoms point to increased oceanic productivity on the basis of the excellent match found between the negative phases of the north atlantic oscillation nao index and the intensified tagus river discharge observed for the last century it is hypothesized that the increased influx of terrigenous material during the lia reflects a negative nao like state or the occurrence of frequent extreme nao minima during the milder few centuries of the mwp stronger coastal upwelling conditions are attributed to a persistent positive nao like state or the frequent occurrence of extreme nao maxima the peak in magnetic susceptibility centered at 90 cm composite core depth ccd is interpreted as the result of the well known 1755 ad lisbon earthquake the lisbon earthquake and accompanying tsunami are estimated to have caused the loss of 39 cm of sediment 355 years of record most of the lia and the instantaneous deposition of a 19 cm sediment bed

sar arcs we have seen evidence for variability in stable auroral red arcs since 1987 an all sky airglow imaging system has operated from a site at the millstone hill haystack observatory in westford ma during the 2 5 solar cycles from 1987 to 2014 many studies using all sky images in conjunction with incoherent scatter radar and satellite data described subauroral ionospheric disturbances observed during individual geomagnetic storms the most prominent storm time optical feature from a subauroral site is a stable auroral red sar arc the standard use of a sar arc s position is to locate the ionospheric footprint of the narrow plasmapause ring current interaction region where heat conduction from the inner magnetosphere excites emission within the f layer trough when mapped from an emission altitude of 400 km to the geomagnetic equatorial plane sar arcs from millstone hill give the location of the plasmapause at radial distances between 2 to 4 5 earth radii a total of 314 sar arcs have been observed during the 27 years of imaging at millstone hill we find no single morphology for all sar arcs but rather patterns that occasionally depart from stability in space and time we have classified these into five categories longevity multiplicity zonal structure latitudinal inhomogeneity and tilt with respect to geomagnetic coordinates in each case the implications for the inner magnetosphere sources that drive sar arcs are explored while individual sar arc variability characteristics have been noted in previous studies here we describe for the first time all five types from the same site an aspect not yet addressed in either magnetosphere or ionosphere modeling studies

evaporitic sedimentation in the southeastern anatolian foreland basin new insights on the neotethys closure abstract we integrate stratigraphic petrographic and geochemical analysis of subsurface data wells together with field surveys to study the sedimentation of a marginal miocene sub basin of the southeastern anatolian foreland basin seafb se turkey this sub basin located in the batman siirt region is characterized by the existence of evaporites carbonates sulphates and chlorides and alluvial detritus which were divided in the following five lithostratigraphic members from older to younger lower and upper yapilar and lower middle and upper sulha these members deposited in an epicontinental mudflat during the early miocene both the bromine content and the sulphur and oxygen isotope composition 34 s v cdt and 18 o v smow of halite and sulphates samples respectively also suggest a marine origin of the precipitation brines however influence of geothermal fluids and dissolution and re precipitation of evaporites from uplifted areas in these brines such as the early miocene members and or triassic units is interpreted comparing and integrating our results with data documented in previous works it is here recognized that the depositional model of the studied sub basin differs from that which explain the coeval sedimentation of units situated in the western part of the seafb moreover our model shows some depositional and paleoenvironmental similarities with miocene evaporites located in the mesopotamian foreland basin this work provides valuable insights on the middle miocene salinity crisis which is related to the evolution of the neotethys closure

the european record of the gerbil myocricetodon rodentia mammalia and its bearing on the messinian salinity crisis abstract the gerbillid myocricetodon is mainly known from the miocene of africa and asia but some small samples of this genus have been identified in southwestern europe interpreted as immigrants driven by the messinian salinity crisis however the specific determination of these european populations and their relationships with african forms have proved controversial the population from negratin 1 guadix basin southern spain was attributed to the african species myocricetodon jaegeri but other european samples have still not been determined at the specific level here we describe the material of myocricetodon from almenara m eastern spain which represents the most abundant sample of the genus known from europe confirming its assignation to m jaegeri we also analyze material from salobrena pino mojon southern spain and castelnou 3 southern france concluding that these samples belong to the same species the presence of these coeval and conspecific populations of myocricetodon is explained by a single migratory event from northern africa the occurrence of myocricetodon interpreted as an indicator of warm and arid conditions is restricted to southern and eastern spain and the southeastermost extreme of france being mainly limited to the mediterranean coast it is absent in other iberian areas such as the granada cabriel and teruel basins despite their rich and well studied record of late miocene mammals this distribution suggests the existence of different environmental more humid conditions in those areas during the latest miocene as already proposed for the granada basin our data also indicate that the presence of myocricetodon in europe was limited to a short interval close to the miocene pliocene boundary contrarily to other gerbils namely debruijnimys which persisted during the pliocene this suggests that myocricetodon could be extremely sensitive to environmental factors and its occurrence in europe was linked to a specific moment of arid conditions

topographically generated subinertial flows within a finite length canyon abstract the presence of a canyon cutting the continental shelf has been observed to enhance wind driven upwelling in particular in the vicinity of juan de fuca canyon at the mouth of the juan de fuca strait an eddy containing deep water from a depth of approximately 450 m has been documented strong upcanyon flows have been observed within numerous canyons including astoria canyon which cuts the shelf offshore of the mouth of the columbia river the author develop a linear theory for wind driven flow over an infinitesimally thin but finite length canyon to illustrate the basic mechanism two regimes are considered the initial growing velocity field and a later steady velocity field the flow toward the shore is enhanced by o 10 by the presence of the canyon in a homogeneous fluid the presence of stratification introduces smaller horizontal length scales the baroclinic rossby radius and allows further enhancement of the upcanyon flow numerical simulations show that the linear theory is a reaso

the onset of the messinian salinity crisis in the eastern mediterranean pissouri basin cyprus the pissouri basin in cyprus contains one of the most suitable sedimentary successions with which to study the onset of the messinian salinity crisis in the eastern mediterranean exposures along the new paphos limassol motorway near pissouri exhibit distinct cyclic bedding which permits the construction of a chronology based on orbital tuning biostratigraphic results reveal 10 planktonic foraminifera events that have been astronomically dated in other mediterranean sections and as such provide an excellent first order age control magnetostratigraphic results are in good agreement with the biostratigraphic data and show that all magnetic chrons between c4n 1n and c3an 1n are present the pattern of sedimentary cycles generally fits well with the insolation curve astronomical tuning of the succession shows that the first gypsum bed at pissouri overlies a 40 60 kyr stromatolite bearing transitional interval and correlates with the amplitude increase in insolation at 5 96 ma as in the western mediterranean this indicates that the onset of evaporite precipitation was synchronous right across the entire mediterranean basin fl 2002 elsevier science b v all rights reserved

upwelling in the continental shelf of northern south china sea associated with 1997 1998 el nino 1 a strong upwelling off the continental shelf of the northern south china sea scs in 1998 summer is reinvestigated using a suite of new satellite measurements and numerical modeling previous studies indicate that the upwelling in the western scs especially off the vietnam coast almost disappears during 1998 summer following the el nino because of the weakened southwest monsoon this study identifies that the coastal upwelling in the adjacent northern scs nscs is significantly strengthened during 1998 summer and the alongshore wind stress is dramatically enhanced over the region as a result the offshore ekman transport in 1998 summer is the strongest almost twice the average of the other 17 years during 1997 2007 the chl a concentrations in the representative upwelling regions are much higher than any in other years further analysis suggests that two adjacent basin scale upwellings in the scs have different responses and maintaining mechanisms because of the anticyclonic atmospheric circulation anomaly over the scs and northwest pacific the northern flank of the atmospheric circulation anomaly intensifies the monsoonal winds off the nscs coast while the southern flank suppresses the southwesterly winds along the vietnam coast

simultaneous observations of sar arc and its ionospheric response at subauroral conjugate points l 2 5 during the st patrick s day storm in 2015

a middle pleistocene northeast atlantic coccolithophore record paleoclimatology and paleoproductivity aspects abstract changes in paleoclimate and paleoproductivity patterns have been identified by analysing in conjunction with other available proxy data the coccolithophore assemblages from core md03 2699 located in the portuguese margin in the time interval from the marine isotope stage mis 13 14 boundary to mis 9 535 to 300 ka during the mid brunhes event the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate nar values and by the blooming of the opportunistic genus gephyrocapsa changes in coccolithophore abundance are also related to glacial interglacial cycles higher nar and numbers of coccoliths g mainly occurred during the interglacial periods while these values decreased during the glacial periods superimposed on the glacial interglacial cycles climatic and paleoceanographic variability has been observed on precessional timescales the structure of the assemblages highlights the prevailing long term influence of the portugal pc and iberian poleward ipc currents following half and full precession harmonics related to the migration of the azores high ah pressure system small gephyrocapsa and coccolithus pelagicus braarudii are regarded as good indicators for periods of prevailing pc influence gephyrocapsa caribbeanica syracosphaera spp rhabdosphaera spp and umbilicosphaera sibogae denote periods of ipc influence our data also highlights the increased percentages of coccolithus pelagicus pelagicus during the occurrence of episodes of very cold and low salinity surface water probably related to abrupt climatic events and millennial scale oscillations of the ah icelandic low il system

regional climate and glacial control on high resolution oxygen isotope records from ain el beida latest miocene northwest morocco a cyclostratigraphic analysis in the depth and time domain 1 high resolution benthic and planktonic stable oxygen isotope records are presented for the upper miocene ain el beida aeb section in northwestern morocco and reveal the clear imprint of the climatic precession obliquity and eccentricity cycles in the interval between 6 5 and 5 5 ma the 18o depth series were transformed into time series using astronomical tuning of the sedimentary color cycles to the 65 n summer insolation curve of the la93 solution with present day values for tidal dissipation and dynamical ellipticity spectral analysis and band pass filtering show that the ratios of the astronomically related spectral peaks are not consistent in the depth and time domain the inconsistencies are mainly due to variations in sedimentation rate that are positively correlated with precession amplitude i e modulated by eccentricity in addition they result from a long term trend in sedimentation rate a simple model of nonlinear response of the sedimentation rate to the eccentricity modulation of precession was used to simulate the observed shifts in the relative position of the spectral peaks in the depth domain cross spectral analysis was carried out on the 18o time series and a combined eccentricity tilt obliquity and precession etp curve the precession controlled 18o signal varies in phase with etp partly as a result of the tuning procedure while the obliquity related signal reveals a small lag of 2 3 kyr relative to obliquity this lag is slightly reduced at the time of the messinian salinity crisis msc and increases to 5 6 kyr if the tidal dissipation term in the astronomical solution is reduced to half its present day value the obliquity related lag is most likely associated with the slow buildup of ice caps whereas the precession signal is interpreted as to dominantly reflect regional climate changes comparable to those associated with mediterranean sapropels finally the benthic 18o record is compared with open ocean records and discussed in terms of an astronomically tuned oxygen isotope stratigraphic framework

identification of upwelling areas on sea surface temperature images using fuzzy clustering abstract sixteen sea surface temperature sst images obtained over the coastal ocean of portugal during the period september 1992 september 2003 were used aiming to identify automatically the areas covered by upwelling waters suitable high resolution colour scales were applied to the sst images in order to enhance the thermal patterns and easily identify the waters with a coastal upwelling origin the automatic identification of the areas covered by upwelling waters was developed by the authors in a previous work through the application of fuzzy clustering and validation indexes and here is explored as an oceanographic application to the portuguese coastal upwelling the fuzzy c means fcm algorithm showed to be able to find partitions that closely defined the upwelling areas and the visualization of the fuzzy c partitions was achieved through the application of a colour scale the xie beni validation index was used to select the c partition that best represented the stage of the upwelling event and showed an agreement with the oceanographic interpretation in 10 of the 14 sst segmented images used in this work two sst images without upwelling were also used in order to check the response of the algorithm to the absence of the phenomena the computation of the matching rate between a c partition and the two areas split by the hand contoured upwelling boundary also allowed the evaluation of how closely the obtained segmentation reproduced the shape of the areas covered by upwelling waters this method successfully identified the upwelling boundary regions in 10 of the 14 sst images the values obtained for the matching rate were higher than 0 77 thus indicating the good quality of the fuzzy partitions the segmented images with 3 or 4 clusters were the most suitable ones to reproduce the areas covered by upwelling waters but it was also shown that for some cases the upwelling areas could be reasonably well reproduced by the fcm 2 partition images while in the latter the area covered with upwelling waters was coincident with the first cluster in the former the segmented image showed two clusters within the upwelling area the first cluster coincided with the area occupied by the most recently upwelled waters near the coast while the second cluster was coincident with the area occupied by the older upwelling waters with its extensions offshore the so called cold filaments the fcm algorithm revealed to be a promising technique in the automatic identification of upwelling areas on sst images

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

coral reefs in coarse terrigenous sedimentary environments upper tortonian granada basin southern spain abstract during the upper tortonian coral reefs developed on fan deltas and braid deltas along the active eastern edge of the granada basin the corals grew in environments characterized by deposition of coarse sands and conglomerates frequency of sedimentation together with sea level rises controlled reef development and determined the architecture and composition of the carbonate deposits in direct contrast to these reefs others flourished at the same time along stable coastal margins of the basin their structure was influenced mainly by periodic rises in sea level the mapping of all these reefs serves as an accurate guide to the upper tortonian geography of the granada basin

late miocene stratigraphy and palaeogeographic evolution of the intramontane guadix basin central betic cordillera spain implications for an atlantic mediterranean connection abstract the guadix basin is an intramontane basin located in the central sector of the betic cordillera its late miocene stratigraphic record is divided into three depositional sequences limited by unconformities representing tectonic and or eustatic events depositional sequence i late tortonian is composed by two systems tracts the lower marks the beginning of marine sedimentation in the basin and comprises three retrograding lithological complexes or depositional systems coastal shallow platform and pelagic basin and is interpreted as a transgressive systems tract the upper systems tract consists of a shallow shelf prograding into a pelagic basin this systems tract exhibits a typically regressive pattern and was deposited during high sea level and is therefore interpreted as a highstand systems tract depositional sequence ii late tortonian is composed of both continental alluvial cones and shallow marine gilbert type delta shallow shelf and reef depositional systems the deposits of this sequence record a significant fall in sea level and are interpreted as a lowstand systems tract depositional sequence iii late turolian ventian or late tortonian messinian was formed of solely retrograding continental depositional systems alluvial fan lacustrine fan delta mud flat and lacustrine with this sequence begins the continental sedimentation in guadix basin in an endorheic context the palaeogeographic evolution of the guadix basin during the late miocene can thus be divided into three stages the first corresponds to depositional sequence i and is characterised by the development of shallow marine environments on the basin margins and deep water deposits in its centre during this stage the basin was connected to the west with the atlantic ocean via the granada and guadalquivir basins and toward the east with the mediterranean sea through the almanzora and campo coy basins in the second stage represented by depositional sequence ii most of the basin was occupied by shallow marine environments during this stage the connection with the atlantic and mediterranean was only open through the guadalquivir and campo coy basins respectively finally the third and last stage corresponding to depositional sequence iii is characterised by the development of continental environments throughout the basin this stage records the definitive closing of the connections with the atlantic ocean and the mediterranean sea

paleoenvironmental evolution of the eastern mediterranean during the messinian constraints from integrated microfossil data of the pissouri basin cyprus abstract integrated data of calcareous nannofossils as well as planktonic and benthic foraminifera from the pissouri motorway section on cyprus allow the reconstruction of surface and bottom water paleoenvironments of the eastern mediterranean during the interval preceding the messinian salinity crisis msc contrary to deeper water locations where benthic foraminifera faunas are suppressed or absent just after the tortonian messinian boundary sediments deposited at intermediate water depths do contain benthic assemblages from the earliest messinian onwards a development towards increasingly unfavourable paleoenvironments is reflected in the planktonic and benthic microfossil records of the pissouri section and proceeds with rather discrete time steps that can be correlated to sequences throughout the mediterranean shortly after the tortonian messinian boundary a transition is recorded in the sedimentology and the open marine deeper water taxa disappear from the benthic foraminifera assemblages subsequently the diversity of all fauna groups diminishes the changes recorded at species level in both surface water and sea floor dwelling taxa suggest decreasing circulation of the bottom waters associated with changes in the surface waters most likely due to increasing stratification from 6 73 ma onwards our data indicate a prominent change to more restricted conditions and increasing salinity at the sea floor together with intermittently rising surface water salinity the dominance of oligotypic and monospecific assemblages and the frequent shifts in assemblage compositions of all microfossil groups indicate severely stressed environments after 6 4 ma probably related to increased salinity the major changes in paleoenvironmental conditions including oxygen deprivation due to stagnation and hypersalinity can be explained by hydrographical changes in the mediterranean basin which are probably caused by tectonic movements in the rif corridor acting in concert with astronomical cyclicity evaluation of the paleodepth proxies indicates that the depth of the pissouri basin remained rather constant at 300 500 m with a minimum of 200 m until deposition of the barre jaune the transitional interval towards the evaporites and that early shallowing to neritic depths as was proposed before is highly unlikely

late cenozoic base level variations of the caspian sea a review of its history and proposed driving mechanisms abstract the caspian sea is characterized by significant variations in its base level during the late cenozoic and provides an important repository for long term records of both regional climate and tectonics due to its position within the interior of the eurasian continent and at the northern margin of the ongoing arabia eurasia collision zone the caspian also serves as an important moisture source for eastern eurasia including the northern tibetan plateau and thus the history of caspian base level variations represents an important and poorly understood constraint on paleoclimate reconstructions throughout eurasia prior work in the caspian region has largely focused on developing biostratigraphic age divisions and investigating the history of connection between the caspian black and mediterranean seas as well as the global ocean recent geochronologic work in the caspian and related basins has questioned previous correlations of hydrologic events in these different basins as a result prior estimates of the chronology and magnitude of caspian sea level variations may be incorrect here we synthesize previous work to develop a new caspian base level curve starting at the beginning of the meotian regional stage 7 ma we also present a new synthesis of potential driving mechanisms for the large variations in caspian base level and speculate on a possible cause for the enigmatic akchagyl transgression this synthesis highlights the dynamic range of caspian sea level which varied from 200 m above to in excess of 1000 m below its current level during the late cenozoic and provides a basis for future work investigating the tectonic and climatic drivers behind variations in caspian base level

the messinian diatomite deposition in the mediterranean region and its relationships to the global silica cycle abstract diatomites constitute a widely represented lithology in the messinian sections of the circum mediterranean neogene marginal basins although traditionally interpreted as genuine evidence of the gradually restricted conditions that characterized the mediterranean just before the messinian salinity crisis their coeval occurrence with a global intensification of the opaline production in the world oceans late miocene early pliocene biogenic bloom suggests that an integrative analysis of the origins of these sediments is necessary a comprehensive analysis of the geological and paleontological records suggests that the synergistic intervention of abiotic tectonic and climate reconfigurations and biotic expansion of grass dominated opal rich biomes controlling factors may have promoted a remarkable enhancement of silica flux from continents to oceans which in turn can explain the opaline burst that occurred during the late miocene at both the global and mediterranean scale the finely laminated pattern and the rich fossil content of diatomaceous deposits that are usually considered to be byproducts of anoxic conditions are briefly discussed some studies seem to indicate that instead of anoxia the aggregation and sedimentation of diatom tests may play a critical role in these processes the lower messinian diatomites of the mediterranean region are generally interbedded with organic rich sediments sapropels clearly attesting prolonged precessionally controlled periods of basin stratification and bottom water anoxia or hypoxia a causal relationship between sapropel and diatomite deposition in the mediterranean is proposed considering the possible interplay between stratification adapted diatoms and anaerobic bacteria and their respective role in influencing the marine silica cycle

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

twentieth century warming and hydrographical changes in the tagus prodelta eastern north atlantic pluri annualproxyrecordsofmarinesedimentcoresfromthetagusprodeltaofflisbon portugal havebeengeneratedtogaininsightintotheclimaticandhydrographicchangesintheareaduringthetwentieth century thestudyincludesbenthicandplanktonicforaminiferalfaunasandthestableisotopiccompositionof one benthic uvigerina celtica and two planktonic globigerina bulloides and globorotalia inflata foraminiferal species sea bottom and surface water temperatures were estimated based on the 18 o values of

intensified upwelling over a widened shelf in the northeastern south china sea 1 observational and three dimensional modeling studies reveal that the intensified upwelling in the northeastern south china sea nscs is formed as a result of intensified upslope advection of dense deep waters that cross the middle shelf toward the inner shelf over a distinctly eastward widened shelf the strongest advection occurs over the converging isobaths near the head of the widened shelf as these dense deep waters advance shoreward they are advected downstream by the quickly developed upwelling current over the inner shelf and eventually outcropped at the lee of a coastal cape dynamically the shoreward cross isobath transport over the widened shelf is geostrophically enhanced by a quasi barotropic negative westward along isobath pressure gradient force as a result of the net rate of the momentum influx and by an intensified bottom frictional transport owing to the flow confluence near the head of the widened shelf a negative pressure gradient also exists at the lee of the coastal cape over the inner shelf and locally amplifies shoreward motion induced by the respective widened shelf and the coastal promontory the along isobath variations of cross isobath transport in the water column over the middle and inner shelves interactively characterize intensified upwelling in the nscs

hydrographic conditions along the western iberian margin during marine isotope stage 2 the surface water hydrography along the western iberian margin as part of the north atlantic s eastern boundary upwelling system consists of a complex seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions such as during marine isotope stage mis 2 and how north atlantic meltwater events especially heinrich events affected them to help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern iberian margin md95 2040 md95 2041 md99 2336 and md99 2339 the records reveals that with the exception of the heinrich events and greenland stadial gs 4 hydrographic conditions along the western iberian margin were not much different from the present during the last glacial maximum lgm subtropical surface and subsurface waters penetrated poleward to at least 40 6 n site md95 2040 export productivity was in general high on the western margin during the lgm and low in the central gulf of cadiz in agreement with the modern situation during the heinrich events and gs 4 on the other hand productivity was high in the gulf of cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling heinrich event 1 had the strongest impact on the hydrography and productivity off iberia and was the only period when subarctic surface waters were recorded in the central gulf of cadiz south of lisbon 39 n the impact of the other heinrich events was diminished and not all of them led to a significant cooling in the surface waters thus climatic impacts of heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region

the messinian guadalhorce corridor the last northern atlantic mediterranean gateway miocene tectonics with the last survi ving gateway occurring during the early messinian north west of malaga in the region of the guadalhorce river valley the guadalhorce gateway pro vided a significant control on messin ian pre evaporitic oceanic circulation in the mediterranean sea it acted as a major outflow channel of mediterra nean water into the atlantic and its closure induced water mass restriction and stratification in the western medi terranean immediately prior to the messinian salinity crisis abstract messinian marine deposits of the guadalhorce river valley in southern spain record evidence of the last northern gateway that existed between the mediterranean and the atlantic they comprise sandstones and conglomerates with unidirectional cross bed sets up to nearly 1 km long in their down sedimen tary dip direction these cross bed sets relate to extremely fast 1 0 1 5 m s 1 bottom currents flowing from the mediterra nean into the atlantic the guadalhorce gateway which had a maximum width of 5 km and a maximum water depth of 120 m was an important element controlling the messinian pre evaporitic oceanic circulation in the mediterranean sea as it acted as a major outflow channel its closure limited the exchange of water between the atlantic and the mediterranean to the rifian corridors of morocco inducing water mass restriction and stratification in the western mediterranean immediately prior to the messinian salinity crisis

satellite derived phytoplankton pigment structures in the portuguese upwelling area a series of 25 nimbus 7 coastal zone color scanner images obtained from july 1981 to september 1983 in portuguese coastal waters was analyzed in order to study the space time distribution of phytoplankton pigment in the images from winter and spring the phytoplankton distributions showed no significant spatial patterns during the upwelling season from late june to october several recurrent patterns were observed filaments of high pigment concentration extended zonally 200 km off the west coast of portugal north of lisbon pigment rich plumes were observed south of capes along the west coast south of lisbon and parallel to the south coast of portugal the location of the filaments and plumes coincided with topographic features such as submarine ridges south of lisbon the location of plumes was also related to coastal morphology the temporal variability of the pigment patterns was compared with the wind induced offshore ekman transport calculated from measurements made at two meteorological stations located at lisbon and faro on the south coast a significant relationship was found well developed phytoplankton structures were generally related to moderate or intense offshore transport whereas the absence of plumes corresponded to either weak offshore transport or coastal convergence for each of the three coastal areas in this study scatter plots showed linear relationships between digital counts of phytoplankton concentration and sea surface temperature the spatial variation of the temperature range decreased in time after the onset of an upwelling event one cause of this variation could be the north south change in temperature of the upwelled eastern north atlantic central water along the portuguese coast

the inner shelf response to wind driven upwelling and downwelling abstract a two dimensional numerical model is used to study the response to upwelling and downwelling favorable winds on a shelf with a strong pycnocline during upwelling or downwelling the pycnocline intersects the surface or bottom forming a front that moves offshore the characteristics of the front and of the inner shelf inshore of the front are quite different for upwelling and downwelling for a constant wind stress the upwelling front moves offshore at roughly a constant rate while the offshore displacement of the downwelling front scales as t because the thickness of the bottom layer increases as the front moves offshore the geostrophic alongshelf transport in the front is larger during downwelling than upwelling for the same wind stress magnitude because the geostrophic shear is near the bottom in downwelling as opposed to near the surface in upwelling during upwelling weak stratification is maintained over the inner shelf by the onshore flux of denser near bottom water this weak stratif

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

spatiotemporal evolution of upwelling regime along the western coast of the iberian peninsula 1 the spatial and temporal variability of upwelling regime along the western coast of the iberian peninsula ip has been analyzed by means of two different but complementary databases quikscat satellite database which is available from mid 1999 with a high spatial resolution 0 25 0 25 and pacific fisheries environmental laboratory pfel database with a coarser spatial resolution 1 1 but extending back to 1967 the combined use of both databases allows determination of the spatial variability of ekman transport and pumping and identification of temporal trends in upwelling signal upwelling favorable conditions are observed during spring and summer apart from this well known seasonality on upwelling regime along the western coast of the ip some other features have been identified 1 upwelling occurs simultaneously along the entire western coast of the ip but is undoubtedly more complex closer to particular features of the shoreline 2 positive ekman pumping is more intense near capes sao vicente and rocha during spring summer and near cape finisterre all over the year 3 more favorable upwelling conditions have been observed in february and november during the last decade this result is corroborated by sea level pressure composites which show the existence of abnormally high pressures close to the ip during the last decade compared to the historical records 1948 2006 4 the decadal variability of ui is higher in autumn winter than in spring summer 5 monthly upwelling trends indicate a weakening in upwelling intensity during most of the year with the exception of february june and july

west florida shelf response to local wind forcing april 1998 we compare west florida shelf velocity and sea level data with a model simulation for april 1998 responses for three upwelling and three downwelling favorable wind events are documented along shelf jets accompanied by oppositely directed upper and lower layer across shelf flows with connecting vertical velocity comprise the fully three dimensional inner shelf responses which are sensitive to stratification with an initial density field representative of april 1998 the model simulates velocity and sea level variations in general agreement with the observations whereas substantial mismatches occur without stratification despite the winds being the primary motive agent for the inner shelf the stratification dependence requires that model density fields be maintained through a combination of adequate initial conditions surface offshore and land derived buoyancy inputs and data assimilation dynamical analyses define the inner shelf as the region where the surface and bottom boundary layers are important in the momentum balance kinematically this is where surface ekman layer divergence fed by the bottom ekman layer convergence or conversely sets up the across shelf pressure gradient stratification causes a response asymmetry wherein the offshore scale and magnitude of the upwelling responses are larger than those for the downwelling responses this asymmetry is attributed to thermal wind effects across the bottom ekman layer buoyancy torque by isopycnals bending into the bottom adds constructively destructively with planetary vorticity tilting under upwelling downwelling favorable winds and this may have important implications for nutrients and other material property distributions on the shelf

proxy calibration to instrumental data set implications for paleoceanographic reconstructions 1 high resolution proxy data analyzed on two high sedimentation shallow water sedimentary sequences po287 26b and po287 28b recovered off lisbon portugal provide the means for comparison to long term instrumental time series of marine and atmospheric parameters sea surface temperature sst precipitation total river flow and upwelling intensity computed from sea level pressure and the possibility to do the necessary calibration for the quantification of past climate conditions xrf fe is used as proxy for river flow and the upwelling related diatom genus chaetoceros is our upwelling proxy sst is estimated from the coccolithophore synthesized alkenones and u37k index comparison of the fe record to the instrumental data reveals its similarity to a mean average run of the instrumentally measured winter jfma river flow on both sites the upwelling diatom record concurs with the upwelling indices at both sites however high opal dissolution below 20 25 cm prevents its use for quantitative reconstructions alkenone derived sst at site 28b does not show interannual variation it has a mean value around 16 c and compares quite well with the instrumental winter spring temperature at site 26b the mean sst is the same but a high degree of interannual variability up to 4 c appears to be determined by summer upwelling conditions stepwise regression analyses of the instrumental and proxy data sets provided regressions that explain from 65 to 94 of the variability contained in the original data and reflect spring and summer river flow as well as summer and winter upwelling indices substantiating the relevance of seasons to the interpretation of the different proxy signals the lack of analogs and the small data set available do not allow quantitative reconstructions at this time but this might be a powerful tool for reconstructing past north atlantic oscillation conditions should we be able to find continuous high resolution records and overcome the analog problem

temperature and productivity changes off the western iberian margin during the last 150 ky abstract present day hydrographic conditions along the western iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters in order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky high resolution proxy records were generated in 3 cores su92 03 md95 2040 md95 2042 located along the iberian coast between 43 12 n and 37 48 n and forming a n s profile in all cores planktonic foraminifera census counts are used to reconstruct summer sea surface temperature sstsu and export productivity pexpsu using the modern analog technique simmax 28 sstsu and pexpsu values similar to the present are observed throughout the holocene and mis 5e periods for each site respectively indicating fairly stable conditions equivalent to the modern ones on glacial interglacial timescales sstsu increases by 2 3 c from the northern to southernmost site pexpsu on the other hand shows a decrease of 30 40 gc m2 yr from north to south at present time and during interglacial periods and no significant variation 90 100 gc m2 yr during glacial periods the northernmost core su92 03 reveals the coldest conditions with records more similar to md95 2040 than to md95 2042 the later of which is as at present more affected by subtropical waters core su92 03 shows higher interglacial productivity similar to open ocean mid to high latitude sites while the other two cores monitor higher glacial productivity conform with other upwelling sites off nw africa a boundary between differences in glacial interglacial productivity appears to be present in our study between 43 12 n and 40 35 n especially north of 40 n coldest sstsu and lowest pexpsu are found during heinrich events h 1 h8 and h10 h11 in contrast lowest pexpsu do not coincide with these events at site md95 2042 but appear to be related to the presence of relatively warm and nutrient poor subtropical eastern north atlantic central water advected with the azores current

evidence for african iberian exchanges during the messinian in the spanish mammalian record abstract the thick continental record in the fortuna basin enables the to establishment of an accurate chronology for the main mammalian events in the western mediterranean between 7 6 and 4 5 my thus covering the whole messinian interval a first mammalian event at about 7 2 my records a significant turnover in the muroid rodent associations a second mammalian event is characterized by the dispersal of the murid paraethomys and a number of large mammals which indicates a first african iberian exchange at about 6 2 my finally a third mammalian event dated between 5 9 and 5 3 my involved the dispersal from northern africa of the gerbil rodents this event is clearly associated with the mediterranean sea level drop following the messinian salinity crisis

evidence for an african iberian mammal dispersal during the pre evaporitic messinian the accurate timing of biogeographic dispersal can be determined by examining the age of fossiliferous strata on either side of a physical barrier here we show that african mammals migrated to iberia and european mammals migrated to north africa at the same time before isolation of the mediterranean sea during the messinian the fossil site of venta del moro spain exhibits western europe s most complete vertebrate fauna for the latest miocene its uniquely cosmopolitan assemblage is evidence of faunal dispersals from africa and asia to europe during the latest miocene glaciation a preliminary paleomagnetic study suggested an age of 5 8 ma for this site but our expanded magnetostratigraphy dates the site at 6 23 ma in addition we recalibrated the paleomagnetic age of the librilla site spain and the north africa site of afoud 1 morocco using the astronomical tuned neogene time scale our results show a two way african iberian mammal dispersal just before 6 2 ma these new ages indicate that an ephemeral land corridor existed between the two continents 250 k y before the onset of the messinian salinity crisis reflecting a tentative initial isolation of the mediterranean sea this corridor developed after tectonics closed the betic seaway at 6 3 ma and during the intensification of the latest miocene glaciation at 6 26 ma when water circulation in the mediterranean became very restricted

imaging magnetospheric boundaries at ionospheric heights 1 an all sky imager asi records atmospheric emissions from zenith to low on the horizon at all azimuths a region typically spanning millions of square kilometers each pixel with its unique elevation azimuth and emission height can be mapped along b field lines to the equatorial plane of the magnetosphere auroral and subauroral structures and boundaries seen in emission within the ionosphere thermosphere i t system can thus be related to source regions for a midlatitude site this i t to inner magnetosphere connection typically falls within the l 2 5 earth radii domain in this study we present the first case of a stable auroral red sar arc observed from three widely spaced asi sites europe north america new zealand sar arcs are produced during the main and recovery phases of a geomagnetic storm with emission driven by heat conduction from a very specific location in the magnetosphere the l value where the plasmapause and the inner edge of the ring current overlap using three site observations we show that this boundary can be followed for 24 consecutive hours simultaneous observations made by three satellites in the defense meteorological satellite program dmsp show that the lowest latitude peak in electron temperature can be used to map the same boundary a key structure of the inner magnetosphere that cannot be observed continuously from sensors orbiting within the magnetosphere is made continuously visible to ground based optical systems via effects caused by the drainage of small amounts of ring current energy into the i t system

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

early pliocene continental vertebrate fauna at puerto de la cadena se spain and its bearing on the marine continental correlation of the late neogene of eastern betics in this paper we synthesize sedimentological magnetostratigraphic and paleontological data from the continental vertebrate site of puerto de la cadena murcia se spain in order to clarify its age the study site is located on the northern edge of the carrascoy mountain range in the upper part of the cigarron unit the end messinian discontinuity has been detected at the base of this unit which indicates it has an early pliocene age abundant remains of small and large vertebrates including rodents lagomorphs primates carnivorans perissodactyls artiodactyls proboscideans testudines squamats and crocodiles have been found in this area some of these elements are of african origin such as debruijnimys sp macaca sp and sivatherium cf hendeyi and their presence is related to the messinian salinity crisis in addition remains found at this site verify the persistence of crocodylia in the european record beyond the late miocene the association includes typical elements of the early ruscinian terrestrial record mn14 like apocricetus cf barrierei sivatherium gazella aff baturra and hipparion fissurae the puerto de la cadena site is located in a reversed geomagnetic chron that has been correlated with c3n 3r from 4 997 to 4 896 ma according to this correlation the mn13 mn14 boundary has a minimum age of 4 9 ma

late cenozoic micromammal biochronology of northwestern africa abstract this synthesis aims to integrate former recent and unpublished data on fossil micromammals rodentia erinaceomorpha soricomorpha chiroptera from moroccan algerian and tunisian archeological and paleontological sites an updated biochronology of these taxa is established from the middle miocene to the holocene ten main biozones are defined they are characterized by specific faunal assemblages whose evolution and migrations were influenced by geologic and climatic events throughout the studied period during the miocene myocricetodontinae were dominant this period was followed by a progressive diversification among murinae gerbillinae and crocidurinae from the plio pleistocene onwards along with sporadic occurrences of european asian and sub saharan taxa before a decrease in small mammal diversity at the beginning of the late pleistocene while modern faunas stabilized overall the new biochronology matches well with the former ones however some slight discrepancies emerge notably because the former biochronologies were based on more sporadic data and often did not consider the whole small mammal faunas the present work represents the first complete biochronological synthesis of north african small faunas for the whole late cenozoic which should be useful for paleontologists and archeologists in providing an up to date framework into which future discoveries will easily find their place

summer upwelling and thermal fronts in the northwestern south china sea observational analysis of two mesoscale mapping surveys persistent coastal upwelling and upwelling induced thermal fronts in the northwestern south china sea are investigated using satellite measurements two intensive mesoscale mapping surveys and three bottom mounted adcps the results indicate that pronounced surface cooling and upwelling related fronts with a width of 20 50 km occur around hainan island and persist through the summer upwelling season driven by the prevailing southwesterly monsoon the subsurface cooling band is approximate to 6 degrees c colder than the water offshore of the east coast where the thermal gradients are generally more than 0 1 degrees c km the cold and nutrient rich coastal water is identified to be derived primarily from the deep water of the outer shelf at the same time the spatial structure of the upwelling and thermal front as well as the upwelling related coastal currents is significantly regulated by wind forcing a prominent lagged correlation between the moored temperature records and alongshore wind stress is detected in the east coast the correlation coefficient is 0 8 with the temperature lagging behind wind stress by 2 2 days indicating that the cooling band off the east coast is dominated mostly by the alongshore southwesterly monsoon during the upwelling season

inner shelf response to cross shelf wind stress the importance of the cross shelf density gradient in an idealized numerical model and field observations this study investigates the effects of horizontal and vertical density gradients on the inner shelf response to cross shelf wind stress by using an idealizednumericalmodel and observations from a mooredarray deployed south of martha s vineyard massachusetts in two dimensional no along shelf variation numerical model runs of an initially stratified shelf a cross shelf wind stress drives vertical mixing that results in a nearly wellmixed inner shelf with a cross shelf density gradient because of the sloping bottom the cross shelf density gradient causes an asymmetric response to on and offshore wind stresses for density increasing offshore an offshore wind stress drives a near surface offshore flow and near bottom onshore flow that slightly enhances the vertical stratification and the cross shelf circulation an onshore wind stress drives the reverse cross shelf circulation reducing the vertical stratification and the cross shelf circulation a horizontal richardson number is shown to be the nondimensional parameter that controls the dependence of the wind driven nondimensional cross shelf transport on the cross shelf density gradient field observations show the same empirical relationship between the horizontal richardson number and transport fraction as the model predicts these results show that it is the cross shelf rather than vertical density gradient that is critical to predicting the inner shelf cross shelf transport driven by a cross shelf wind stress

at the land s end marine resources and the importance of fluctuations in the coastline in the prehistoric hunter gatherer economy of portugal abstract this paper focuses on the importance of aquatic resources in economy and subsistence strategies during the middle and upper palaeolithic of portugal modern theoretical biases in archaeology have led to a marginalization of marine resources and a dismissal of their use by palaeolithic hunter gatherers geological and archaeological data show that changes in the position of the coastline had a direct impact on the visibility of marine resources in the archaeological record marine regressions and transgressions have significantly altered the record of pleistocene coastal settlement using recent studies on changes in upwelling intensity during the last glacial we offer a new perspective on palaeolithic hunter gatherer economy that emphasizes the importance of the coast as a focus of subsistence and settlement

magnetostratigraphy and paleontology of ait kandoula basin high atlas morocco and the african european late miocene terrestrial fauna exchanges abstract a magnetostratigraphic study has been carried out on a middle miocene to upper pliocene lacustrine sedimentary deposit in the central part of the ait kandoula basin which contains micromammal faunas and is situated in the southern high atlas morocco in total 113 samples were subjected to paleomagnetic analysis 60 out of the 113 studied samples representing 52 different stratigraphic levels yielded a paleomagnetic direction and at least the polarity could be recognized in 42 specimens eleven specimens were submitted to af demagnetization the mean direction for normal polarity samples was d 349 4 i 50 7 n 36 95 4 5 k 27 and for reversed polarity samples d 191 2 i 53 4 n 16 95 12 32 k 9 these results yielded a polarity sequence which we interpret as spanning from chron c5n 2n to the beginning of chron c3n 4n this interpretation relies on biostratigraphic data previously proposed for a part of the continental fauna found in the basin this result is in agreement with the 40ar 39ar dating previously carried out on a volcanic ash layer which provided an age of 5 9 0 5 ma 1 and which is shown here to be reversely magnetized this layer is correlated here with the reverse polarity zone corresponding to chron c3r biostratigraphic studies on the same section have shown that the micromammal levels extend here only from middle vallesian to upper turolian upper miocene four localities have yielded western european species of micromammals indicating trans mediterranean terrestrial faunal exchanges between these two continents during the late miocene the european murid rodent occitanomys is recorded for the first time in north africa in level 8 of the afoud section an age younger than 5 32 ma being assigned to this level by the present study level 1 of the same section yields the lagomorph prolagus cf michauxi with an age of 6 1 ma the magnetostratigraphic data suggest therefore that the beginning of terrestrial faunal exchanges between north africa and western europe took place in subchron c3an 1n at about 6 1 ma some 0 4 myr before the beginning of the messinian salinity crisis

chronology of the late turolian deposits of the fortuna basin se spain implications for the messinian evolution of the eastern betics the magnetostratigraphy of the mammal bearing alluvial fan fan delta sequences of the fortuna basin se spain has yielded an accurate chronology for the late turolian messinian basin infill from early to late messinian at least between 6 8 and 5 7 ma the fortuna basin records the sedimentation of alluvial palustrine deposits over a confined shallow basin changing environmental conditions in the latest messinian are illustrated by the retreat of palustrine facies a rapid progradation of the marginal clastic wedges and the initiation of an efficient basin drainage at5 8 ma lower part of chron c3r most likely represents the onshore response to the drastic drop of base level taking place during the messinian salinity crisis this study further provides improved age estimates for the late turolian land mammal events in southern spain the oldest mn 13 locality in the studied sections is correlated to chron c3ar at an age of 6 8 ma the entry of camels and the murid paraethomys in southern spain occurs in chron c3an 1n at 6 1 ma and gives further support for land mammal exchange between africa and the iberian peninsula prior to the salinity crisis in good agreement with

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

global observations of a sar arc a sar arc has been observed at 630 nm with global auroral imaging instrumentation on board the spacecraft dynamics explorer 1 the arc is first detected at about 1908 ut on october 20 1981 and is then observed in four subsequent consecutive orbits spanning 28 hours

mesoscale patterns in the cape sao vicente iberian peninsula upwelling region 1 the coastal upwelling region near cape sao vicente the southwestern tip of the iberian peninsula where the southern zonal coast meets the meridional western coast was studied using over 1200 advanced very high resolution radiometer avhrr satellite images of sea surface temperature and time series of sea level height wind velocities and nearshore sea surface temperature recorded at coastal sites within 200 km of the cape summer upwelling is more intense and persistent off the western coast than off the southern coast where a recurrent warm coastal countercurrent flows westward and at times turns northward along the western coast after reaching the cape in this region the equatorward current jet of cold water upwelled off the western coast is no longer bounded by a coast three preferred directions for the spreading of this water are identified the most persistent is eastward along the southern shelf break and slope possibly merging with waters previously upwelled locally which becomes separated from shore by the coastal progression of the warmer counterflow the second preferred direction results in the southward development of a cold filament feature fed by cold waters upwelled farther north and represents the southernmost extent of the intense coastal upwelling jet which overshoots the cape the least frequent feature to develop is a cold filament that grows westward at the latitude of the cape appearing to result from the meandering of the equatorward jet the coastal countercurrent is seen to interact with the equatorward jet at times of relaxation not only by separating the cold upwelled water from the coast but when it is energetic enough breaking westward offshore through the equatorward cold flow and separating the eastward and southward cold features from the upcoast cold waters empirical evidence shows the presence of an alongshore pressure gradient stronger in summer driving the coastal progression of the warm counterflow wind forcing plays an important role in the circulation by augmenting or diminishing the effect of the preexisting alongshore pressure gradients the extent of the progression of the warm coastal countercurrent along the southern and western coast is dictated by the the strength of the upwelling favorable wind stress which is able to balance and reverse the alongshore flow at least in the upper layers

late neogene evolution of the taza guercif basin rifian corridor morocco and implications for the messinian salinity crisis abstract magnetostratigraphic and biostratigraphic results are presented from neogene deposits in the taza guercif basin located at the southern margin of the rifian corridor in morocco this corridor was the main marine passageway which connected the mediterranean with the atlantic during messinian times correlation of the biostratigraphy and polarity sequence of the taza guercif composite section to the astronomical time scale allows an accurate dating of three subsequent events in the rifian corridor 1 the oldest marine sediments marking the opening of the rifian corridor were deposited at 8 ma at this age a deep 600 m marine basin developed in the taza guercif area marked by deposition of precession controlled turbidite marl cycles 2 paleodepth reconstructions indicate that a rapid 5 m ka shallowing of the marine corridor took place at the tortonian messinian boundary at an age of 7 2 ma this shallowing phase is primarily related to active tectonics although a small glacio eustatic sea level lowering also took place 3 the taza guercif basin was emergent at an age of 6 0 ma and subsequently continental sedimentation continued well into the early pliocene we suggest that shallowing and restricting the marine passageway through the rifian corridor actually initiated the messinian salinity crisis well before the deposition of the messinian evaporites in the mediterranean

wind and topography influence on an upwelling system at the eastern hainan coast 1 during the summer monsoon an upwelling dominates east of hainan island which can be observed by means of field studies and satellite sea surface temperature images the centers of cold water at the surface always show a strong patchiness a 3 d high resolution model is applied to study the impact of the topography on the wind driven upwelling system the experiments show that the upwelling favoring wind is the main driving force and we concluded that the formation of the centers of cold water at the surface significantly depends on the strength of southwesterly and southerly winds moreover the internal waves are generated at the shelf break representing the most prominent interaction between inner shelf and open ocean the alongshore topographic variations play an important role in the distribution of the upwelling centers this combined effect of wind and topography leads to the following processes 1 when the southwesterly or southerly wind is strong enough topographic variations cause upwelling centers at the downstream side of topographic high and a downwelling center at the upstream side which in turn lead to density variations 2 these density variations cause additional pressure gradients which advect the upwelling centers toward the northeast 3 a longer period of upwelling favorable winds support the advection processes which cause an enlargement of the cold water centers all these processes together can explain the observed uneven distribution of upwelling centers

planktonic foraminifera from modern sediments reflect upwelling patterns off iberia insights from a regional transfer function abstract quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core top sediment samples collected along the western iberian margin were used to assess the latitudinal and longitudinal changes in surface water conditions and to calibrate a sea surface temperature sst transfer function for this seasonal coastal upwelling region q mode factor analysis performed on relative abundances yielded three factors that explain 96 of the total variance factor 1 50 is exclusively defined by globigerina bulloides the most abundant and widespread species and reflects the modern seasonal may to september coastal upwelling areas factor 2 32 is dominated by neogloboquadrina pachyderma dextral and globorotalia inflata and seems to be associated with the portugal current the descending branch of the north atlantic drift factor 3 14 is defined by the tropical sub tropical species globigerinoides ruber white globigerinoides trilobus trilobus and g inflata and mirrors the influence of the winter time eastern branch of the azores current in conjunction with satellite derived sst for summer and winter seasons integrated over an 18 year period the regional foraminiferal data set is used to calibrate a sst transfer function using imbrie kipp mat and simmaxndw techniques similar predicted errors rmsep correlation coefficients and residuals deviation from sst estimated for both techniques were observed for both seasons all techniques appear to underestimate sst off the southern iberia margin an area mainly occupied by warm waters where upwelling occurs only occasionally and overestimate sst on the northern part of the west coast of the iberia margin where cold waters are present nearly all year round the comparison of these regional calibrations with former atlantic and north atlantic calibrations for two cores one of which is influenced by upwelling reveals that the regional one attests more robust paleo ssts than for the other approaches

a separating coastal upwelling jet at cape blanco oregon and its connection to the california current system the coastal upwelling region near cape blanco oregon 433n o the west coast of the united states was studied using a towed ctd on seasoar a shipboard acoustic doppler current pro ler adcp satellite sea surface temperature maps and surface drifters during august 1995 the equatorward upwelling jet was inshore of the shelfbreak north of cape blanco meandered gently o shore around the cape and then veered sharply o shore just to the south of the cape analysis of vertical sections of density velocity and spicinessa con rmed the separation of an upwelling jet and front the jet was followed from over the shelfbreak north of the cape to 100 km o shore downstream of the cape the separating jet originates from the coastal upwelling jet leaving the shelf but is augmented by an o shore branching of the poleward undercurrent by combining information from adcp streamfunction maps with analysis of hydrographic data including distributions of the tracer like quantity spicinessa a conceptual model of the three dimensional circulation near the cape emerges a mid shelf upwelling jet encounters a coastal promontory then turns o shore stretching and deepening as it crosses the continental margin the jet then turns back shoreward cyclonically where the deepened equatorward ow encounters the top of the poleward undercurrent owing along the continental slope this causes a portion of the undercurrent to turn o shore to join and strengthen the equatorward transport in the separated jet throughout the separation process the coastal upwelling front and jet are continuous robust features separation of a coastal upwelling jet is an important mechanism for cross shelf transport from the coast to the deep ocean cape blanco appears to be the northernmost point where an equatorward jet regularly separates from the coast to become an oceanic jet and thus serves as the northern boundary of the region where an intense meandering current characteristic of the california current system