the effects of a lateral variation in lithospheric strength on foredeep evolution implications for the east carpathian foredeep abstract lateral variations in lithospheric strength have been adopted often in flexural modeling both 2d and 3d to better fit the observed basement deflections typically supported by gravity data this approach provides essentially a snap shot of the role of lithosphere strength in determining the present day geometry in contrast we investigate and quantify the effects of a lateral change in lithospheric strength on the evolution of the foredeep in front of an advancing orogen transitions in lithospheric strength are common in the foreland of orogens and show large variations in the width of the transition zone and the strength difference former passive margins for instance will display strength changes distributed over several tens to hundreds of kilometers other transitions may originate from juxtaposition or accretion of pieces of lithosphere with different properties and may be characterized by a much smaller width than former passive margins in our modeling a constant load representing an advancing orogenic belt is displaced towards and across a transition from a weak to a strong plate in a 2d elastic thin plate model the effect of different transition widths and strength contrasts on foredeep geometry and bending stress is investigated interference of flexural wavelengths across the transition affects foredeep geometry by causing rapid basin widening oscillation of the bulge and volume increase the bending stresses are found to concentrate and amplify around the strength transition large transition gradients i e large strength contrast or small transition width cause the highest rates of change basin widening caused by the orogenic load advancing towards the transition between the east european craton and the moesian platform appears to control the sarmatian transgression over the east carpathian foreland in romania

life cycle of the east carpathian orogen erosion history of a doubly vergent critical wedge assessed by fission track thermochronology apatite fission track b t thermochronology applied to the east carpathian fold and thrust belt in romania constrains the interaction between the erosion history and the tectonic evo lution of the orogen the long lived constant asymmetric topography of the orogen and the erosion pattern as inferred from apatite ft data are in agreement with the style of evolution predicted by doubly vergent critical coulomb wedge models during the miocene up to 4 km of erosion took place over the actively deforming orogen and the erosion patterns forms a mirrored image of the subsurface deforming wedge the erosion products are deposited in flanking molasse basins which subsided contemporaneously due to the growing topographic weight of the wedge deformation of the wedge was presumably active from the early to late miocene but apatite ft ages between 14 and 9 ma and track length modeling predict an acceleration of erosion rates 0 5 0 3 mm yr ini tially in the middle to late miocene 3 2 ma the onset of erosion coincides with the last phase of convergence and a climax in the deformation history these features are interpreted to have been caused by underplating of the european continental margin convergence ceased before the pliocene according to the activity of thrust faults during the pliocene and quaternary up to 2 km of overburden was removed by erosion leading to isostatic rock uplift of the entire region the use of apatite fission track minimum ages supports the general idea that the orogen has a di achronous evolution from north to south the orogen in the southern bend zone has a more juve nile tectonic character and the main erosion phase took place during the pliocene and quaternary 5 0 ma the integrated approach of large scale morphology and fission track analysis confirms the applicability of the theoretical coulomb wedge mechanics to a natural compressive fold and thrust belt the study complements the geometric features of the orogenic wedge with quantified erosion histories and illustrates the effects of orogen evolution on vertical movements in the entire convergent setting

late miocene to pliocene palaeogeography of the paratethys and its relation to the mediterranean abstract the palaeogeographic evolution of the paratethyan and mediterranean realms are reconstructed with three maps ranging from the late miocene to the middle late pliocene the maps are based on the facial analysis of selected deposits clastic input slope slide process analyses as well as biogeographic data of the planktic benthic and terrestrial biota characteristic fossil assemblages are used for palaeobathymetric and palaeohydrologic interpretations restoration of palaeogeographic connections the palaeogeographic reconstructions are palinspastically restored after dercourt j ricou l e vrielynck b eds 1993 atlas tethys palaeoenvironmental maps gauthier villars paris pp 1 307 14 maps the paleogeographic atlas of northern eurasia 1997 inst tectonics lithospheric plates moscow 26 maps with modifications maps have been prepared for the terminal tortonian early messinian late pannonian early maeotian late messinian pontian salinity crisis time and piacenzian gelasian akchagilian they illustrate the neogene palaeogeographic evolution during and after the attic orogenesis though the emerging mountain system of the alpine foldbelt increasingly separated the paratethys from the mediterranean tethys paratethys connections remained extant and sufficiently effective for limited communication between both basins they governed many features of the cyclic depositional history and biogeographic evolution of the eastern paratethys

thinning and volume loss of the arctic ocean sea ice cover 2003 2008 1 we present our best estimate of the thickness and volume of the arctic ocean ice cover from 10 ice cloud and land elevation satellite icesat campaigns that span a 5 year period between 2003 and 2008 derived ice drafts are consistently within 0 5 m of those from a submarine cruise in mid november of 2005 and 4 years of ice draft profiles from moorings in the chukchi and beaufort seas along with a more than 42 decrease in multiyear my ice coverage since 2005 there was a remarkable thinning of 0 6 m in my ice thickness over 4 years in contrast the average thickness of the seasonal ice in midwinter 2 m which covered more than two thirds of the arctic ocean in 2007 exhibited a negligible trend average winter sea ice volume over the period weighted by a loss of 3000 km3 between 2007 and 2008 was 14 000 km3 the total my ice volume in the winter has experienced a net loss of 6300 km3 40 in the 4 years since 2005 while the first year ice cover gained volume owing to increased overall area coverage the overall decline in volume and thickness are explained almost entirely by changes in the my ice cover combined with a large decline in my ice coverage over this short record there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the arctic ocean ice cover seasonal ice having surpassed that of my ice in winter area coverage and volume became the dominant ice type it seems that the near zero replenishment of the my ice cover after the summers of 2005 and 2007 an imbalance in the cycle of replenishment and ice export has played a significant role in the loss of arctic sea ice volume over the icesat record

the roussillon basin s france a case study to distinguish local and regional events between 6 and 3 ma the roussillon basin is a non silled miocene sedimentary basin filling a late oligocene early miocene graben the basin was intensively impacted by the 2 messinian fluvial erosion as evidenced in exposed sections in seismic profiles and in deep boreholes drilled for hydrocarbon exploration as the basin was open to the mediterranean sea the huge drop in sea level at the peak of the messinian salinity crisis is clearly recorded along with the subsequent sudden marine reflooding and the resulting prograding sedimentary filling particularly in gilbert type fan deltas here the messinian erosional surface mes is accurately mapped in a high resolution document which corrects the confusion resulting from the set of 1 50 000 scale regional maps aim of the 3d reconstruction of the mes is to modernize geological mapping a crucial challenge for mediterranean and peripheral areas thanks to a reliable chronostratigraphy provided by planktonic foraminifers calcareous nannofossils micro and macro mammal remains paleomagnetism and a 10 be cosmogenic nuclide derived study our reconstruction is one of the most comprehensive models of changes in sea level from 6 to 3 ma after the marine reflooding of the mediterranean basin at 5 46 ma the fluctuations in sea level recorded in the roussillon basin were forced by global changes following reflooding the prades large olistostrome collapsed prepared by the previous exhumation along the canigou fault the olistostrome is a good example of a local accident resulting from messinian events the exceptional changes in sea level at the peak of the messinian salinity crisis deeply marked the roussillon basin momentarily overprinting the pyrenean orogenesis key words roussillon basin messinian subaerial erosion zanclean sedimentary filling prades olistostrome

the messinian problem in the pannonian basin eastern hungary insights from stratigraphic simulations abstract earlier studies revealed a prominent unconformity in the messinian stratigraphic record of the lacustrine pannonian basin but it was unclear what factors were responsible for the formation of this unconformity and thus its origin remained controversial the problem was further complicated by the fact that stratal patterns in the messinian varied significantly along the paleo margins of the lake our study introduces quantitative stratigraphic simulations to analyze the role of subsidence sediment supply and lake level changes in the formation of the unconformity and the various architectural patterns that evolved in response to the messinian events the results suggest that a relative lake level fall occurred in the messinian accompanied and followed by tectonic inversion in several parts of the basin since the rate of tectonic subsidence and or uplift varied in space and time the size of the relative lake level fall varied significantly across the basin while various stratal architectural patterns formed in the same time interval the age of the unconformity was estimated based on seismic correlations with paleomagnetic chronozones to be between 5 6 ma which was refined by stratigraphic simulations galeacysta etrusca cysts were found in the unconformity which confirmed its late messinian age the surface is called the intra messinian unconformity imu in this paper seismic interpretations and simulations of stratal architecture led to the formulation of a basin fill model and identification of four stratigraphic architectural patterns related to messinian events including a major lake level fall and coeval and subsequent uplift events in certain parts of the basin

regional isostatic response to messinian salinity crisis events abstract the salinity crisis of the mediterranean during messinian time was one of the most dramatic episodes of oceanic change of the past 20 or so million years resulting in the deposition of kilometer thick evaporitic sequences a large and rapid drawdown of the mediterranean water level caused erosion and deposition of non marine sediments in a large lago mare basin both the surface loading by the lower messinian evaporites and the removal of the water load resulted in isostatic flexural rebound that significantly affected river canyons and topographic slopes we use flexure models to quantitatively predict possible signatures of these events and verify these expectations at well studied margins the highly irregular shape of the reconstructed basin calls for a three dimensional model near basin margins plate bending effects are most pronounced which is why flexure is particularly important for a relatively narrow basin like the mediterranean we focus on one specific sea level scenario for the messinian salinity crisis where most of the evaporite load was deposited during a sea level highstand followed by a rapid desiccation evaporite loading at current sea level is expected to cause subsidence of the deep basins by hundreds of meters and simultaneous uplift of continental parts of the margins differential uplift may lead to significant slope angle changes and thus gravity flows the relative scarcity of lower evaporite sequences along the margins may be a result of these phenomena normal faulting of lower evaporite and older sediments and rocks is expected on the margins desiccation enhances erosion of the freshly exposed continental shelf and slope subsidence and riverbed sedimentation occurs on the continental margins and significant uplift towards the basin center reverse faulting is predicted at the margins finally regional isostatic uplift following zanclean flooding is predicted to destabilize margin slope deposits and to cause marginal uplift river down cutting and normal faulting

messinian crisis what happened around the northeastern aegean abstract the effects of the severing of the atlantic mediterranean connection during the 400 000 year messinian event are also observed around the northern aegean during this time a sea of brackish water character developed between paratethys in the north and the mediterranean in the south this sea is named here egemar this basin was principally fed by surrounding rivers and by paratethyan waters that entered egemar via a connection through the sea of marmara which was then a bay of the paratethys the sedimentary sequence deposited in egemar is principally composed of limestones containing brackish water fauna paratethyan however there are some intercalations containing mediterranean species five intercalations of mediterranean character are found within the sedimentary sequence of egemar indicating the re establishment of an atlantic mediterranean connection from time to time and thus replenishment of marine waters the turolian is represented by continental clastics which interdigitate with the brackish water cycles implying a number of regressions egemar eventually became part of the eastern mediterranean due to a major transgression during the early pliocene

paratethyan mediterranean connectivity in the sea of marmara region nw turkey during the messinian the sea of marmara region is thought to have been a gateway between paratethys and the mediterranean since the middle miocene and is therefore an important control on water mass exchange between the two realms the miocene successions in the northeastern aegean and northwestern marmara regions indicate that the first mediterranean marine transgression to affect these areas occurred during the late serravallian in the northeastern aegean region frequent marine incursions occurred during the tortonian and messinian stages the messinian stage in this area is represented by a package of brackish to fresh water carbonates with some marine sandstone siltstone interbeds alcitepe formation which conformably overlies the tortonian kirazli formation the messinian sequence is overlain with an erosional contact by a shallow marine siliciclastic sequence goztepe formation of zanclean age with its brackish to fresh water carbonates and broadly constrained age the messinian sequence is interpreted as being coeval with the upper evaporite lago mare sequence observed in western mediterranean basins in the western marmara region the pontian messinian alcitepe formation consists of bioclastic and oolitic limestones with basal clastic rocks it conformably overlies the fluvio lacustrine siliciclastic sediments of the middle to upper miocene kirazli formation and is overlain by fluvio lacustrine sediments of the kimmerian 5 5 3 2 ma truva and tevfikiye formations with an erosional contact the bioclastic limestones of the alcitepe formation in the western marmara region contain a molluscan and ostracod fauna that are endemic to paratethys these fauna indicate deposition in a shallow brackish to fresh water environment faunal and paleomagnetic analyses of a section of the alcitepe formation at yenimahalle canakkale confirm that the formation is of pontian age and represents chron c3r 6 04 5 24 ma the ostracod analysis indicates that during deposition of the alcitepe formation salinity increased from brackish in the lower part to more saline conditions in the upper part ostracod valves have low 87sr 86sr values relative to coeval late miocene ocean water this indicates that exchange between the sea of marmara region and the global ocean was restricted throughout this period fossil and sr isotope evidence suggests however that there was a paratethyan marmara connection during the deposition of the lower part of the alcitepe formation with paratethyan influence reaching the north aegean connection via marmara between paratethys and the mediterranean was not re established until the late aktchagylian late pliocene the re connection was caused by both increased activity on the north anatolian fault and global sea level rise

evolution of directional wave spectra in the marginal ice zone a new model tested with legacy data abstractfield experimental data from a 1980s program in the greenland sea investigating the evolution of directional wave spectra in the marginal ice zone are reanalyzed and compared with the predictions of a new phase resolving three dimensional model describing the two dimensional scattering of the waves by the vast number of ice floes that are normally present the model is augmented with a dissipative term to account for the nonconservative processes affecting wave propagation observations reported in the experimental study are used to reproduce the ice conditions and wave forcing during the experiments it is found that scattering alone underestimates the attenuation experienced by the waves during their passage through the ice field with dissipation however the model can replicate the observed attenuation for most frequencies in the swell regime model predictions and observations of directional spreading are in agreement for short to midrange wave periods where the wave field quickly becomes

cenozoic evolution of the eastern black sea a test of depth dependent stretching models abstract subsidence analysis of the eastern black sea basin suggests that the stratigraphy of this deep extensional basin can be explained by a predominantly pure shear stretching history a strain rate inversion method that assumes pure shear extension obtains good fits between observed and predicted stratigraphy a relatively pure shear strain distribution is also obtained when a strain rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form the timing of opening of the eastern black sea which occupied a back arc position during the closure of the tethys ocean has also been a subject of intense debate competing theories called for basin opening during the jurassic cretaceous or paleocene eocene our work suggests that extension likely continued into the early cenozoic in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism further basin deepening also appears to have occurred in the last 20 myr this anomalous subsidence event is focused in the northern part of the basin and reaches its peak at 15 10 ma we suggest that this comparatively localized shortening is associated with the northward movement of the arabian plate we also explore the effects of paleowater depth and elastic thickness on the results these parameters are controversial particularly for deep water basins and margins but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy

flexure due to the messinian pontian sea level drop in the black sea paleowater depth observations suggest that a large sea level drop occurred in the black sea coeval with the messinian salinity crisis in the mediterranean sea this sea level drop would have induced vertical motions of the solid earth which influenced strait dynamics with major implications for the hydrological regime of the region using three dimensional flexure models we find that a sea level drop between 1730 and 2230 m is required to reproduce the observed paleowater depths the models predict that uplift reduced the seaway connectivity between the black sea and the mediterranean sea aegean region and between the black sea and the caspian sea stavropol highlands the miocene paratethys sea consequently became fragmented and the remaining subseas likely became more sensitive to climate change this agrees with the discovery of erosional surfaces in the caspian sea and in the pannonian basin to explain the synchronicity of the sea level lowering in the black sea and the mediterranean we speculate that a regional shift toward a drier climate occurred in response to the messinian salinity crisis in the mediterranean which led to a fall in sea level within the black sea

towards an astrochronological framework for the eastern paratethys mio pliocene sedimentary sequences of the focsani basin romania abstract a reliable geological timescale for the neogene sedimentary deposits of the romanian carpathian foredeep did not exist so far due to the lack of accurate isotopic datings and straightforward magnetostratigraphic correlations here we present a new chronology for the upper miocene to pliocene deposits of the westernmost part of the eastern paratethys based on high resolution magnetostratigraphic data from the focsani basin the thick and continuous river sections of putna 2 35 km and rimnicu s rat 7 32 km yield excellent magnetostratigraphic results and allow an unambiguous correlation to the polarity timescale for the interval between 7 and 2 5 ma the new age control permits the calculation of accumulation rates for each polarity zone which shows a significant increase at approximately 5 8 6 my the upper miocene to pliocene sedimentary rocks of the focsani basin display cyclic alternations of sandy units and finer intervals the calculated values for the average duration of the observed sedimentary cycles are very close to the average duration of precession 21 7 ky which indicates that the sedimentary cycles from the eastern carpathian foredeep deposits are astronomically forced we show that the usage of the unambiguous time control offered by magnetic polarity stratigraphy would give a more realistic picture of the processes that have taken place in this tectonically active region

measurement of arctic sea ice thickness by submarine 5 years after scicex in april 2004 the royal navy submarine hms tireless became the first uk submarine to conduct environmental monitoring in the arctic ocean since 1996 as the last us scicex scientific ice expeditions cruise was in 2000 this has been the only opportunity for a civilian scientist to carry out measurement of ice draft and oceanography over a wide area of the arctic this paper presents preliminary results and compares them with similar investigations in the 1970s 90s the route of tireless covered a large area of the european sector of the arctic from 58 et o 628 w transects were carried out from the marginal ice zone in fram strait up to the north pole and along the 858 n parallel north of greenland as part of work for the european commission iris project image intensity from the advanced synthetic aperture radar instrument on the european space agency s envisat satellite has been compared with ice draft from the submarine the raw data were found to be highly variable so a moving average was applied producing a correlation of 0 79 tireless carried a full oceanographic sensor suite and expendable probes for investigation into changes in the arctic ocean the results from these show further erosion of the arctic cold halocline layer by advancing atlantic water compared to previous climatologies and fieldwork expeditions preliminary ice draft data from 858 n show deeper ice keels than those encountered by a submarine on the same route in 1987

changes in the thickness distribution of arctic sea ice between 1958 1970 and 1993 1997 1 submarine sonar data collected in the central arctic basin during middle and late summer were used to examine differences in the sea ice thickness distribution function g h between the periods 1958 1970 and 1993 1997 cruises during the former period were made in july and august whereas the 1993 1997 cruises were made in september and october seasonal correction was applied to adjust for the differences in thickness while ice drafts were from only seven submarine cruises and somewhat spatially limited results indicate that the fractional area covered by open water and first year ice increased from 0 19 to 0 30 during the time interval this was balanced by an 11 reduction of level multiyear and ridged ice substantial losses occurred in ice thicker than 2 m with an increase in the amount of 1 2 m ice the volume of ice less than 4 m thick remained nearly the same and the total volume decreased about 32 losses in the volume of thicker ice increased with increasing thickness part of the change in g h is likely caused by increased ice area export through fram strait in the late 1980s and early 1990s because decadal variations in the north atlantic oscillation and arctic oscillation indices correlate with ice export anomalies export induced changes in g h probably tend to be cyclical in nature however a substantial shift in the peak of g h suggests that changes in thermal forcing were also a major factor in the observed thinning

messinian event in the black sea evidence of a messinian erosional surface in 1975 sediment cores from leg dsdp 42b sites 380a and 381 revealed a thin sediment layer in the black sea basin which points to a shallow water environment at the miocene pliocene boundary with these facts and in the wake of hypothesis of the messinian salinity crisis msc it was proposed that the black sea like the mediterranean sea suffered a desiccation period at the end of the messinian hsu k j and giovanoli f 1979 messinian event in the black sea palaeogeography palaeoclimatology palaeoecology 29 75 93 whereas the main topics of the msc in the mediterranean sea is now widely accepted the lack of evidence for a messinian erosional surface in the black sea left the debate about the messinian desiccation of this basin open until today the analysis of high resolution multi channel seismic data acquired during the blason surveys brings important new elements for this scientific debate 1 down the slope offshore the bosporus we show a clear erosional surface correlated to the top of the upper miocene shallow water environment unit of site dsdp 381 the overlying lower zanclean unit inevitably dates this erosional surface of the messinian event 2 a wide intra pontian erosional surface ipu is evidenced on the romanian shelf the ipu is characterized by a sharp decrease in the incision rate from outer deep canyons to inner shelf superficial incisions network according to the most recent paratethyan and mediterranean stratigraphic scale correlations the ipu erosional surface is considered as the analogue to the messinian erosional surface described down the slope offshore the bosporus in addition to recently discovered inland erosional signature the wide regional erosional surface we underline on the western black sea margins validates the black sea messinian desiccation hypothesis we also demonstrate that evaporative draw down of the black sea implied the installation in the basin of a negative hydrologic budget during the messinian the lack of a major messinian danube canyon on the romanian shelf supports the hypothesis of a messinian danube trapped in the dacic basin however the presence of a messinian superficial incision network connecting the location of the modern danube delta to deeply incised messinian canyons on the outer shelf ipu makes the hypothesis of a danube reaching the partially desiccated black sea still possible

calcareous nannofossil biostratigraphy and magnetostratigraphy of the upper miocene and lower pliocene of the northern aegean orphanic gulf strimon basin areas greece abstract the transitional position of the northern aegean makes it an important area for studying the relation between the mediterranean and the eastern paratethys a chronostratigraphic framework has been obtained for the late neogene deposits along the orphanic gulf and in the strimon basin of northern greece by analysing calcareous nannofossil data and paleomagnetic results from eight sections the local formations and major lithological units have been correlated with the upper miocene and lower pliocene stages furthermore the obtained framework has facilitated a more detailed reconstruction of the effects of the messinian salinity crisis on the sedimentary record magnetostratigraphic data from the strimon basin result in an age estimate of 6 3 ma for the dafni choumnikon formation transition between normal polarity subchrons c3an 2n and c3an 1n since this late miocene age estimate corresponds closely to estimates of the maeotian pontian boundary in the eastern paratethys dacic basin we believe this transition from marine to brackish conditions corresponds to this latter boundary the gypsiferous unit in the basal part of the choumnikon equivalent beds along the orphanic gulf can then be correlated with the evaporites in the northern aegean and the lower evaporites of the mediterranean basin consequently we assume that these northern aegean evaporites have been deposited between 5 96 and 5 59 ma freshwater deposits above the evaporites are easily traceable across the orphanic gulf area as a gravel or sandstone unit topped by a travertine marker bed and have a wide lateral continuation since their position is intermediate between the shallow marine gypsum anhydrite and the more open marine clastics of the pliocene we argue that these beds correlate with the desiccation phase of the mediterranean and black sea basins this intra messinian event probably occurred between 5 59 and 5 50 ma thus predating the upper evaporites or lago mare of the mediterranean a clear recognition of the miocene pliocene boundary remains problematic in the orphanic gulf area nannofossil assemblages in the sections suggest a higher position of the local base of the pliocene than indicated by the level with the first appearance of planktonic and benthic foraminifera discontinuous occurrences of levels containing nannofossil assemblages of zone mnn11b c are found between the travertine unit and the lowermost pliocene beds representing brief marine ingressions the latter show that in the latest messinian presumably temporary connections of atlantic mediterranean waters with the northern aegean basin existed these marine ingressions likely extended further into the eastern paratethys as demonstrated by the presence of nannofossil assemblages in the middle and upper pontian of the dacic and euxinic basins the events around the miocene pliocene transition resulted in a fairly abrupt change from brackish to open marine conditions in a relative deep basin which was subject to increased rates of subsidence from the onset of evaporite deposition in the late messinian onward

the decline in arctic sea ice thickness separating the spatial annual and interannual variability in a quarter century of submarine data 1 naval submarines have collected operational data of sea ice draft 93 of thickness in the arctic ocean since 1958 data from 34 u s cruises are publicly archived they span the years 1975 to 2000 are equally distributed in spring and autumn and cover roughly half the arctic ocean the data set is strong we use 2203 values of mean draft each value averaged over a nominal length of 50 km these values range from 0 to 6 m with a standard deviation of 0 99 m multiple regression is used to separate the interannual change the annual cycle and the spatial field the solution gives a climatology for ice draft as a function of space and time the residuals of the regression have a standard deviation of 0 46 m slightly more than the observational error standard deviation of 0 38 m the overall mean of the solution is 2 97 m annual mean ice draft declined from a peak of 3 42 m in 1980 to a minimum of 2 29 m in 2000 a decrease of 1 13 m 1 25 m in thickness the steepest rate of decrease is 0 08 meters per year m a in 1990 the rate slows to 0 007 m a at the end of the record the annual cycle has a maximum on 30 april and a peak to trough amplitude of 1 06 m 1 12 m in thickness the spatial contour map of the temporal mean draft varies from a minimum draft of 2 2 m near alaska to a maximum just over 4 m at the edge of the data release area 200 miles north of ellesmere island

mechanisms of summertime upper arctic ocean warming and the effect on sea ice melt 1 in this study we use a numerical sea ice ocean model to examine what causes summertime upper ocean warming and sea ice melt during the 21st century in the arctic ocean our first question is what causes the ocean to warm in the pacific sector during the summer we find that about 80 of total heating over this region comes from ocean surface heat flux with the remaining 20 originating in ocean lateral heat flux convergence the latter occurs mostly within a few hundred kilometers of the northwest alaskan coast in the summer of 2007 the ocean gained just over twice the amount of heat it did over the average of the previous 7 years our second question is what causes sea ice to melt in the pacific sector during summer our analysis shows that top melt dominates total melt early in the summer while bottom melt and in particular bottom melt due to ocean heat transport dominates later in the summer as atmospheric heating declines bottom melt rates in summer 2007 were 34 higher relative to the previous 7 year average the modeled partition of top versus bottom melt closely matches observed melt rates obtained by a drifting buoy bottom melting contributes about 2 3 of total volume melt but is geographically confined to the marginal ice zone while top melting contributes a lesser 1 3 of volume melt but occurs over a much broader area of the ice pack

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

modelling depositional shifts between sedimentary basins sediment pathways in paratethys basins during the messinian salinity crisis the evolution of sedimentary basins separated by uplifted topographic barriers is characterised by gradual regressive deposition until one of the basins is filled and its sedimentation bypasses to the adjacent basin defining a depositional shift one of the critical parameters controlling these depositional shifts is sea level variation its drop potentially triggering a depositional shift by cancelling the available accommodation space conversely a sea level rise can create new accommodation space resulting in a depositional shift towards a previously overfilled basin here we use a three dimensional numerical model to study the sedimentary response to sea level variations of a system of two basins in this model a single mountainous source area is feeding an intra continental basin that is separated by a submarine barrier from another basin with normal marine bathymetry the sedimentary response is modelled during a cycle of sea level drop and subsequent rebound that exposes the barrier to sub aerial erosion the examined parameters are the barrier height magnitude and duration of sea level change climate and flexural rigidity modelling demonstrates that shifting the bulk of sedimentation from the continental basin to the open marine environment requires some minimum magnitudes and durations of sea level drop moreover given the specific geometry and parameters of our model an intervening barrier causes a delay of up to 0 35 myr depending on the magnitude and duration of sea level change to the onset of an outward depositional shift when compared to a situation without a barrier these depositional shifts depend on changes in climate magnitude and duration of sea level change model results are applied to the connectivity between the black sea and the dacic basin suggesting that depositional shifts observed during the messinian salinity crisis can be explained by a sea level drop of 1000 m in the black sea

role of the 3 d distributions of load and lithospheric strength in orogenic arcs polystage subsidence in the carpathians foredeep abstract it has been widely documented that the depth of foredeeps does not always reflect the topography of the neighboring orogens in many cases the topographic load is insufficient to explain basin subsidence such is the case of the se carpathians where an anomalously deep almost 13 km foreland basin has evolved since the middle miocene badenian a peculiar feature of this basin is its position relative to the orogen in contrast to typical foredeeps which deepen towards the belt the maximum depth of this basin is 10 20 km out of the orogen the subsidence in the carpathians bend foreland is characterized by two stages the first is middle miocene badenian in age and is related to ne sw extension when fault bounded basins were formed modeling shows that the foreland underwent small pre orogenic uniform thinning the modeling also predicts

sea ice topography of the arctic ocean in the region 70 degrees w to 25 degrees e in october 1976 a cooperative experiment was made to survey the sea ice topography in the european sector of the arctic ocean h m submarine sovereign acquired 4000 km of ice draft data by using an upward looking sonar while a canadian forces aircraft flew along the submarine s track and acquired 2200 km of ice elevation data by using a laser profilometer the two types of profile were processed in corresponding 100 km section lengths and the following statistical analyses and comparisons were made i probability density functions o f ice draft and elevation each distribution shows a peak for young ice and for undeformed multi year ice at large ice thicknesses the distributions take the analytical form of a negative exponential the mean drafts enable two distinct geographical ice regimes to be identified there is an offshore zone of very heavy pressure ridging extending up to 400 km from the coasts of ellesmere island and of north greenland with mean ice draft in the range 5 0 to 7 5 m while out in the central arctic ocean the mean ice draft is lower 3 9 5 1 m and the characteristics of the ice cover remain homogeneous over a length scale of 1000 km the transition between the two regimes is abrupt taking place in less than 25 km data from the same part of the central arctic taken in march 1971 showed a mean ice draft 0 3 m lower while data from the central beaufort sea showed a mean draft more than 0 8 m lower ii level ice distributions ice with a local gradient of less than 1 in 40 was defined as level ice and used as an indicator of the quantity and thickness distribution of undeformed i e thermodynamically grown ice in the arctic ocean the distribution has a mode at 3 0 3 1 m draft and level ice percentages are in the range 30 40 bottom side and 70 80 top side in the offshore zone and 45 55 bottom and 85 95 top in the central arctic thus about half of the arctic ice cover consists of deformed ice iii pressure ridge spacings the spacings of ridge keels fit a negative exponential distribution characteristic of randomness except at close spacings where there is a deficit of keels explained as a geometrical effect and at very large spacings where there is an excess due to the contribution of polynyas the distribution of sail spacings exhibits these two effects but also differs from a random distribution at moderate sail separations iv ridge elevations and drafts keel drafts fit a law of form p h d oc exp ah 2 d h except for an excess of keels at drafts beyond 20 m there is a positive correlation between mean keel draft and keel frequency there are 3 5 4 5 keels per kilometre with draft exceeding 9 m in the offshore zone and 2 3 in the central arctic sail elevations fit a law of form p h d h x exp a h d h with a positive correlation between mean sail elevation and sail frequency the sail elevation and ice elevation distributions can be related by assuming that all thick ice is contained in pressure ridges of triangular cross section v keel sail comparison for the 21 corresponding 100 km sections there are positive correlations between mean sail height and mean keel draft and between keel frequency and sail frequency from these it is possible to convert a sail distribution computed from a laser profile into a keel distribution enabling sea ice bulk characteristics to be derived from airborne surveys alone vi leads and polynyas a lead was defined as a continuous sequence of depth points greater than 5 m long and not exceeding 1 m draft the number density n d of leads per kilometre of width d m fits the power law n d 15 d 2 exceptionally wide leads were concentrated in the offshore zone and in the marginal ice zone close to the open water of the greenland sea

decline in arctic sea ice thickness from submarine and icesat records 1958 2008 1 the decline of sea ice thickness in the arctic ocean from icesat 2003 2008 is placed in the context of estimates from 42 years of submarine records 1958 2000 described by rothrock et al 1999 2008 while the earlier 1999 work provides a longer historical record of the regional changes the latter offers a more refined analysis over a sizable portion of the arctic ocean supported by a much stronger and richer data set within the data release area dra of declassified submarine sonar measurements covering 38 of the arctic ocean the overall mean winter thickness of 3 64 m in 1980 can be compared to a 1 89 m mean during the last winter of the icesat record an astonishing decrease of 1 75 m in thickness between 1975 and 2000 the steepest rate of decrease is 0 08 m yr in 1990 compared to a slightly higher winter summer rate of 0 10 0 20 m yr in the five year icesat record 2003 2008 prior to 1997 ice extent in the dra was 90 during the summer minimum this can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to 55 during the record setting minimum in 2007 this combined analysis shows a long term trend of sea ice thinning over submarine and icesat records that span five decades

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

top bottom multisensor remote sensing of arctic sea ice the arctic sea ice cover has been studied using near simultaneous observations by passive and active synthetic aperture radar sar microwave sensors upward looking and sidescan sonars a lidar profilometer and an infrared sensor data from two aircraft and a submarine over an approximately 100 km track of central arctic sea ice were registered and analyzed to evaluate the characteristics of the ice cover and the utility of each sensor in ice studies the results of comparative and correlation analyses are as follows the probability density functions of ice draft from sonar and elevation from lidar were found to be almost identical when isostasy is taken into account this result suggests that the basic ice thickness distribution can be derived from the surface topography measurements alone reasonable correlation was found between sar backscatter and ice draft or elevation especially when scales were adjusted such that 15 20 sar pixels were averaged however surface roughness derived directly from standard deviations in the lidar elevation data was found to be poorly correlated to the sar backscatter these results indicate that the sar values are affected more by scattering from the ice than from the snow covered surface the active and passive microwave sensors are shown to generally complement each other as the two sensors are especially sensitive to different physical properties of the sea ice undeformed first year ice showed low backscatter values but high brightness temperatures while some multiyear ice showed high backscatter values and low brightness temperature however surfaces identified as multiyear ice by the passive system have a large spread in the unaveraged sar backscatter indicating limitations when using a one channel sar for ice type identification at the highest resolution also ridged ice identified by sonar and sar data covers a large range of passive microwave emissivity suggesting considerable variability in the age and salinity of this type of ice significant variations about 0 11 in the minimum emissivity of consolidated multiyear ice are observed in different regions of the arctic using the high resolution 30 m passive microwave data this suggests that regional variations in texture and scattering characteristics of multiyear ice in the arctic are present likely influenced by different histories of formation of the ice in different regions

characterizing horizontal variability and energy spectra in the arctic ocean halocline energy transfer from the atmosphere into the upper arctic ocean is expected to become more efficient as summer sea ice coverage decreases and multiyear ice thins due to recent atmospheric warming however relatively little is known about how energy is transferred within the ocean by turbulent processes from large to small scales in the presence of ice and how these pathways might change in future this study characterises horizontal variability in several regions of the eurasian arctic ocean under differing sea ice conditions historic along track ctd data collected by a royal navy submarine during summer 1996 allows a unique examination of horizontal variability and associated wavenumber spectra within the arctic ocean halocline spectral analysis indicates that potential energy variance under perennial sea ice in the amundsen basin is o 100 less than within the marginal ice zone miz of fram strait spectra from all regions show a transition in scaling at wavelengths of approximately 5 to 7 km at scales greater than the transition wavelength to 50 km energy spectra are consistent with a k 3 scaling where k is wavenumber and interior quasi geostrophic dynamics the scaling of spectra at these scales is extremely similar between regions suggesting similar dynamics and energy exchange pathways the k 3 scaling is steeper than typically found in regions of mid latitude open ocean at scales below the transition wavelength to 300 m spectra are close to a k 5 3 scaling or flatter indicating a change in dynamics which is potentially due to internal waves dominating variability at small scales this article is protected by copyright all rights reserved

elastic parabolic equation and normal mode solutions for seismo acoustic propagation in underwater environments with ice covers sound propagation predictions for ice covered ocean acoustic environments do not match observational data received levels in nature are less than expected suggesting that the effects of the ice are substantial effects due to elasticity in overlying ice can be significant enough that low shear approximations such as effective complex density treatments may not be appropriate building on recent elastic seafloor modeling developments a range dependent parabolic equation solution that treats the ice as an elastic medium is presented the solution is benchmarked against a derived elastic normal mode solution for range independent underwater acoustic propagation results from both solutions accurately predict plate flexural modes that propagate in the ice layer as well as scholte interface waves that propagate at the boundary between the water and the seafloor the parabolic equation solution is used to model a scenario with range dependent ice thickness and a water sound speed profile similar to those observed during the 2009 ice exercise icex in the beaufort sea

evolution of the north caucasus foredeep constraints based on the analysis of subsidence curves abstract using a database of more than 130 wells the alpine evolution of the north caucasus foredeep can be described in three main periods 1 the early jurassic to middle late cretaceous including the cenomanian relates to the initial rifting phase and was characterised by succession of comparatively high rates of subsidence and uplift during this stage many events in the eastern and western parts were synchronous whereas some of them appeared to be smoothed in the stavropol high the southern border of the area had a more complex behaviour often moving in the opposite direction relative to the rest of the area the main peculiarities of evolution of the great caucasus region can be explained if we adopt the hypothesis of stamply and pillevuit 1993 and suppose that the early jurassic extension of the trough was accompanied by a strong left lateral transform movement as a result the central part of the great caucasus trough formed as a pull apart basin analysis of the style of movements of the southern border of the scythian plate as well as data on tectonics and volcanism in the great and lesser caucasus showed that other regional compressional and extensional mesozoic events could also have a transform component shear stresses within the lithosphere of the great caucasus can be due to oblique subduction or even transform movements at the plate boundary to the south of the caucasus region dercourt et al 1993 2 the period from the late cretaceous to the middle eocene from the turonian to the bartonian relates to the oceanic suture of the lesser caucasus and was characterised in the great caucasus area by alternating subsidence and uplift events of considerably lower amplitude at least up to the maastrichtian beginning in the late paleocene subsidence curves for almost all the area reflect the same events but in the western part and also in the north of the central part the rate of movements was considerably higher and since the late paleocene short term events in this area took place on the background of rather fast subsidence at nearly constant rate we believe that this subsidence and formation of the east black sea depression have the same origin we consider strong differences in evolution of the eastern western and central parts during the second stage to be due to closure of the lesser caucasus oceanic basin and arrival of the nakhichevan block this led to changes of configuration of the plate boundary and resulted in reorganisation of stress and displacements within the caucasus region this reorganisation was a reason for the opening of the east black sea depression and rapid subsidence of the western and central parts of the area at the end of the second stage 3 the period from the middle eocene to the present relates to the development of a foreland basin coeval with shortening and uplift in the adjacent great caucasus range it was characterised by alternation of relatively short uplift and longer subsidence events an important feature of this stage is that although the amplitude of movements varied from place to place these events were synchronous in all parts of the foredeep at the stavropol region sediments preserved only for the beginning of this stage formation and evolution of the foredeep during the third stage can not be explained exclusively by elastic flexure to do this we used the model of a small scale convection within the asthenosphere mikhailov et al 1996 mikhailov et al 1999 by the comparison of numerical results with the data on the evolution of the north caucasus foredeep we concluded that there were four main stages of compression in the processes of formation of the great caucasus mountain belt the first compression took place before the maykopian between 39 5 and 36 0 ma the other three were in the tarkhanian 16 6 15 8 ma konkian early sarmatian 14 3 12 3 ma and pontian 7 0 5 2 ma the different width of the great caucasus trough by the beginning of the compression as well as variations in thickness of the lithosphere and a different thermal state can cause interruption of the formation of the foredeep at the stavropol high

evidence for thinning of the arctic ice cover north of greenland in may 1987 a british submarine carried out an ice profiling experiment in the arctic ocean in which the route closely approximated that of an earlier voyage in october 1976 over a zone extending more than 400 km to the north of greenland there is evidence of a significant decrease in mean ice thickness in 1987 relative to that found in 1976 this thinning amounts to a loss of volume of at least 15 over an area of 300 000 km2 the nature of the ice thickness distributions suggests that the thinning is primarily associated with the presence of a larger fraction of young and first year ice a consequence of wind driven divergence in the ice cover during the months preceding the 1987 observations such a large fluctuation in a region previously believed to possess consistently high ice thicknesses illustrates the importance of monitoring arctic ice thickness more systematically to determine whether such fluctuations fall within the limits of normal inter annual variability

thermo mechanical modelling of black sea basin de formation abstract we present the results of a thermo mechanical modelling study carried out to investigate the effect of pre rift rheology on subsequent basin de formation in the black sea area important differences are inferred for the bulk lithosphere structure and mechanical properties expressed in terms of different estimates for levels of necking in the western and eastern black sea respectively gravity data provide constraints on the mode of flexure in the black sea pointing to significant lateral variations in pre rift lithospheric strength these features strongly affect predictions for mesozoic cenozoic basin stratigraphy and have implications for the presence and development of rift shoulder topography on the margins of the black sea basins differences in lithosphere strength affect the mode of stress propagation from the basin margins into the central parts of the black sea basins during the post rift phase these post rift compressional stresses could be of key importance for long wavelength late neogene differential motions within the basins superimposed on vertical motions induced by rifting and subsequent sediment loading thermo mechanical modelling of integrated lithospheric strength points to a rapid increase of strength during the later stages of post rift evolution and the presence of relatively strong lithosphere in the centre of the basin these features predict preferential shortening induced by compressional activity of surrounding orogens to be primarily accommodated at the basins margins

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

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

application of gis and hydrogeochemistry of groundwater pollution status of nagapattinam district of tamil nadu india this study evaluated groundwater quality of the coastal aquifer in nagapattinam district with intensive agricultural activities in the southern part of india chemical components such as ph ec tds major cations and anions were used to identify seawater intrusion fifty two groundwater samples were collected from dug and bore wells in this region during summer and monsoon seasons 2011 ec tds na and cl were higher in summer than in monsoon the correlation and two way joining cluster analyses clearly show that groundwater quality is mainly controlled by seawater intrusion and other anthropogenic sources modified hill piper exhibits that most of the samples belong to water contaminated with gypsum sector the interpretation of gibbs plot represents the groundwater samples that fall in evaporation and rock weathering zone and other samples are affiliated to various anthropogenic activities based on na sar chloride hardness and wilcox classification the groundwater is moderately suitable for agriculture this region is vulnerable to seawater intrusion during summer due to the severe pumping of groundwater in groundwater quality maps produced by inverse distance weighting of arcgis some good and medium patches could be used for agriculture to a certain extent the northern southern and central parts of the study area fell in poor quality regions because of seawater intrusion and infiltration of irrigation water contaminated with pesticides and fertilizers

stratigraphic and structural characteristics of the romanian black sea shelf abstract the western black sea basin opened during cretaceous times by back arc rifting in association with a north dipping subduction at the rear of the cretaceous early tertiary pontide volcanic arc the sedimentary wedge developed on the shelf of the romanian black sea sector reflects a complex interplay between large scale rifting uplift of the orogenic flanks large scale post rift subsidence and sea level changes we examine the detailed structural configuration of this sector for a regional correlation with the adjacent offshore in ukraine and bulgaria the evolution of the western black sea basin started in the albian cenomanian times when two extensional phases with significantly different directions n s and subsequently e w lead to the formation of a complex interplay between isolated blocks organised in horsts and grabens generally deepening eastwards superposition of normal faults footwall blocks from the two extensional episodes generated a deeply subsided area with enhanced accommodation space i e the histria depression and consequently recorded a larger thickness of paleogene sediments in the post rift stage re activation of faults and associated folding reflects repeated inversion during the late cretaceous oligocene times associated with subsequent periods of non deposition and or erosion during moments of basin fill exposure these periods of inversion recorded in the black sea are controlled by coeval orogenic deformations taking place in the balkans pontides and the crimean thrust belt sea level fluctuations during the neogene and late alpine tectonics in the neighbouring orogens caused massive sedimentation followed by sediment starvation and or significant erosion large thicknesses of sediments accumulated during the pontian presumably associated with an extensional episode deepening the distal parts of the basin and with differential compaction structures the interpretation of a high quality seismic dataset combined with published data allowed the correlation of major structural units and lineaments defined onshore towards the carpathians with the ones deeply buried below the western black sea basin sediments unit correlations are furthermore used to derive an integrated tectonic image of the western black sea area

deterioration of perennial sea ice in the beaufort gyre from 2003 to 2012 and its impact on the oceanic freshwater cycle time series of ice draft from 2003 to 2012 from moored sonar data are used to investigate variability and describe the reduction of the perennial sea ice cover in the beaufort gyre bg culminating in the extreme minimum in 2012 negative trends in median ice drafts and most ice fractions are observed while open water and thinnest ice fractions 0 3 m have increased attesting to the ablation or removal of the older sea ice from the bg over the 9 year period monthly anomalies indicate a shift occurred toward thinner ice after 2007 in which the thicker ice evident at the northern stations was reduced differences in the ice characteristics between all of the stations also diminished so that the ice cover throughout the region became statistically homogenous the moored data are used in a relationship with satellite radiometer data to estimate ice volume changes throughout the bg summer solid fresh water content decreased drastically in consecutive years from 730 km3 in 2006 to 570 km3 in 2007 and to 240 km3 in 2008 after a short rebound solid fresh water fell below 220 km3 in 2012 meanwhile hydrographic data indicate that liquid fresh water in the bg in summer increased 5410 km3 from 2003 to 2010 and decreased at least 210 km3 by 2012 the reduction of both solid and liquid fresh water components indicates a net export of approximately 320 km3 of fresh water from the region occurred between 2010 and 2012 suggesting that the anticyclonic atmosphere ocean circulation has weakened

a numerical study of the climate response to lowered mediterranean sea level during the messinian salinity crisis abstract roughly six million years ago tectonic movements isolated the mediterranean sea ms from the atlantic ocean an event known as the messinian salinity crisis msc subsequent evaporative drawdown of the ms resulted in a subaerial depression with a depth between 1500 and 2500 m in this study five simulations are run using the national center for atmospheric research ncar community atmosphere model version 3 cam3 configured with the slab ocean model three simulations have been performed to test the climate impacts to desiccation and to changing the ms base level in this study the ms base level is reduced 750 m in the half land simulation hl and 1500 m in the lowered sea ls and lowered land ll simulations the hl and ll simulations differ from the ls in that the surface is converted to land representing the complete desiccation of the ms the substantial ms depression generates planetary scale atmospheric waves responsible for significant climate effects throughout the northern hemisphere a notable deepening of the aleutian low and a significant equatorward shift in the atlantic jet stream are evident in djf vertical ascent at the northern margin of the ms results in a 1 5 2 5 mm day 1 precipitation anomaly in the ls run over the alps consistent with proxy data annual mean area averaged ms evaporation is slightly higher than control conditions except when salinity is a substantial barrier to evaporation our results suggest that a partially filled basin cannot exist in equilibrium and the ms must either be partly connected to the atlantic ocean or completely desiccated base level lowering which alters the water budget must be taken into account when considering the freshwater budget during the msc

implications of outcrop geology for reservoirs in the neogene productive series apsheron peninsula azerbaijan the neogene sediments of eastern azerbaijan and western turkmenistan contain significant hydrocarbon reserves in deltaic reservoirs sedimentary logging of these reservoirs at outcrop in azerbaijan has outlined four facies associations that encompass a range of paleoenvironments from alluvial braided river sandstones and conglomerates to delta front siltstones and mudstones the facies associations suggest a river dominated braid delta and are arranged into an architecture controlled by base level changes parasequences parasequence sets and sequence boundaries are key elements the facies associations and stratigraphic architecture together with outcrop observations of cementation and faulting are summarized in terms of four idealized reservoir models fluvial delta plain proximal delta front and distal delta front each reservoir model has distinctive grain size and shale distributions comparison of nearby oil fields with the studied outcrops suggests that the outcrops form good analogs from which to model reservoir architecture barriers and baffles to fluid flow reservoir heterogeneity and reservoir quality variations

thinning of arctic sea ice observed in fram strait 1990 2011 1 time series 1990 2011 of sea ice thickness observed by moored sonars in the transpolar drift in fram strait are examined contrasting the post 2007 years against the 1990s three remarkable changes in the monthly ice thickness distributions are highlighted 1 the thickness of old level ice modal thickness is reduced by 32 2 the old ice modal peak width is reduced by 25 and 3 the fraction of ridged ice thicker than 5 m is reduced by 50 the combined effect on the mean ice thickness is a reduction from an annual average of 3 0 m during the 1990s to 2 2 m during 2008 2011 most of the thinning took place after 2005 2006 while the old ice modal thickness and peak width show signs of recovery after 2008 the decreasing trend in fraction of ridged ice and mean ice thickness persists until the end of the record in 2011 the ice observed in fram strait carries an integrated signal of arctic change due to the advection of ice from many sites in the arctic based on concurrence in timing we conclude that much of the thinning quantified here is reflecting recent change in the age composition of the arctic ice cover toward younger ice the old level ice remains thin and as such the ice cover remains preconditioned for new summers of very low sea ice extent

sea ice thickness distribution in the greenland sea and eurasian basin may 1987 upward sonar data from a 3400 km track in the greenland sea and the eurasian basin of the arctic ocean obtained by a british submarine in may 1987 have been statistically analyzed mean ice thicknesses in the greenland sea show significant melting with downstream distance at an average rate of 0 38 m per degree of latitude equivalent to about 2140 km3 yr 1 of freshwater input between 80 n and 75 n in the region north of fram strait between 82 n and 80 n there is remarkable consistency between mean ice drafts in 1987 and in three previous cruises 1976 1979 1985 while between greenland and the north pole there was a significant thinning in 1987 relative to 1976 in fram strait the mean ice draft shows evidence of thinning within the region of influence of a semipermanent eddy ice draft distributions show that the probability density function of deformed ice follows a negative exponential distribution and that the change of shape of the distribution with downstream distance in the greenland sea is due to preferential melting of thicker ice pressure ridge draft distributions also fit a negative exponential while their spacings fit a lognormal distribution lead width distribution follows a power law with an exponent of 1 45 for narrow leads and 2 50 for wider leads if leads are defined as having a 1 m maximum draft 1 67 and 2 76 for a 0 5 m maximum draft lead spacings follow a negative exponential distribution for moderate spacings 400 1500 m but with an excess of lead pairs at small and very large spacings

thinning of the arctic sea ice cover comparison of sea ice draft data acquired on submarine cruises between 1993 and 1997 with similar data acquired between 1958 and 1976 indicates that the mean ice draft at the end of the melt season has decreased by about 1 3 m in most of the deep water portion of the arctic ocean from 3 1 m in 1958 1976 to 1 8 m in the 1990s the decrease is greater in the central and eastern arctic than in the beaufort and chukchi seas preliminary evidence is that the ice cover has continued to become thinner in some regions during the 1990s

on the uncertainty of sea ice isostasy during late winter 2007 coincident measurements of sea ice were collected using various sensors at an ice camp in the beaufort sea canadian arctic analysis of the archived data provides new insight into sea ice isostasy and its related r factor through case studies at three scales using different combinations of snow and ice thickness components at the smallest scale 1m point scale isostasy is not expected so we calculate a residual and define this as zjey to describe vertical displacement due to deformation from 1 to 10m length scales we explore traditional isostasy and identify a specific sequence of thickness calculations which minimize freeboard and elevation uncertainty an effective solution exists when the r factor is allowed to vary ranging from 2 to 12 with mean of 5 17 mode of 5 88 and skewed distribution at regional scales underwater airborne and spaceborne platforms are always missing thickness variables from either above or below sea level for such situations realistic agreement is found by applying small scale skewed ranges for the r factor these findings encourage a broader isostasy solution as a function of potential energy and length scale overall results add insight to data collection strategies and metadata characteristics of different thickness products

ocean waves across the arctic attenuation due to dissipation dominates over scattering for periods longer than 19 s the poorly understood attenuation of surface waves in sea ice is generally attributed to the combination of scattering and dissipation scattering and dissipation have very different effects on the directional and temporal distribution of wave energy making it possible to better understand their relative importance by analysis of swell directional spreading and arrival times here we compare results of a spectral wave model using adjustable scattering and dissipation attenuation formulations with wave measurements far inside the ice pack in this case scattering plays a negligible role in the attenuation of long swells specifically scattering dominated attenuation would produce directional wave spectra much broader than the ones recorded and swell events arriving later and lasting much longer than observed details of the dissipation process remain uncertain average dissipation rates are consistent with creep effects but are 12 times those expected for a laminar boundary layer under a smooth solid ice plate

circumpolar thinning of arctic sea ice following the 2007 record ice extent minimum september 2007 marked a record minimum in sea ice extent while there have been many studies published recently describing the minimum and its causes little is known about how the ice thickness has changed in the run up to and following the summer of 2007 using satellite radar altimetry data covering the arctic ocean up to 81 5 degrees north we show that the average winter sea ice thickness anomaly after the melt season of 2007 was 0 26 m below the 2002 2003 to 2007 2008 average more strikingly the western arctic anomaly was 0 49 m below the six year mean in the winter of 2007 2008 these results show no evidence of short term preconditioning through ice thinning between 2002 and 2007 but show that after the record minimum ice extent in 2007 the average ice thickness was reduced particularly in the western arctic citation giles k a s w laxon and a l ridout 2008 circumpolar thinning of arctic sea ice following the 2007 record ice extent minimum geophys res lett 35 l22502 doi 10 1029 2008gl035710

further evidence of ice thinning in the arctic ocean a sea ice thickness profile obtained in september 1996 from the eurasian basin of the arctic ocean between fram strait and the north pole was compared with a profile obtained in the same region in september october 1976 a decline in mean ice draft of 43 was observed over the 20 year interval in agreement with changes observed in other parts of the arctic ocean by rothrock et al 1999

choking the mediterranean to dehydration the messinian salinity crisis strait uplift due to isostasy played a pivotal role in the development and maintenance of a desiccated mediterranean basin during the late miocene messinian salinity crisis new three dimensional flexure models for the western mediterranean suggest that most of the giant evaporite body was deposited before sea level lowering any mechanism that subsequently caused a mediterranean sea level lowering by a few hundred meters during several thousand years sufficed to cause isostatic uplift and closure of the gateways thus choking the mediterranean to desiccation due to this isostatic feedback multiple desiccation and reflooding phases driven by milankovitch cycles are unlikely when the atlantic connection had been lost and sea level had dropped a sizeable regional uplift of the strait of gibraltar developed that presented a formidable obstacle to reflooding rollback and steepening of the gibraltar slab may have played a key role at the end of the miocene by dynamically lowering the sill region thus reinstating the oceanic connection

palaeogeographic environment during the desiccation of the black sea abstract during the latest chersonian about 10 3 m y ago tectonic movements took place leading to an elevation of the crimean caucasian chain and to an isolation of the fore caucasian part of the black sea basin this part of the basin had been draining the rivers of the russian platform and after the isolation it became desalinized while the main part of the black sea basin was almost desiccated and evaporites mainly dolomites formed in it due to the predominant calcium magnesium carbonate composition of the chersonian sea waters these dolomites are found in the drillings of dsdp leg 42b and are confirmed geophysically the tectonic movements during the latest chersonian led to the formation of a series of grabens along which the mediterranean sea invaded the north aegean area and a little later during the early maeotian the black sea

on the spacing and draft distributions for pressure ridge keels the negative exponential distribution is reconsidered as a description of pressure ridge spacings and drafts it is found to give an excellent fit for drafts but not for spacings the spacing distribution is found to be fitted much better by a three parameter lognormal distribution of which the third parameter the threshold is dependent on the beam width of the instrument used to collect the ice bottom profile

arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects 1 a transect of the arctic ocean by the british submarine tireless in march 2007 enabled the thickness characteristics of the ice cover to be measured during the winter immediately preceding the exceptional retreat of summer 2007 in this paper we report on mean and modal drafts probability density functions of draft and the frequency and depth distribution of pressure ridges and we compare results with those from an earlier submarine cruise in winter 2004 which covered part of the same area in the region from north of fram strait to ellesmere island about 85 n 0 70 w we find no change in mean drafts between 2004 and 2007 though there is a change in ice composition with more ridging in 2007 but a lesser modal draft this agrees with the observations of younger ice being driven toward fram strait in 2007 the region north of ellesmere island continues to be a redoubt containing more thick deformed multiyear ice than any other part of the transect in the west the submarine profiled extensively under the sedna ice camp at 73 n 145 w this is in the same location as the 1976 aidjex ice camp and a sonar survey done by a u s submarine in april 1976 we found that a large decrease in mean draft had occurred 32 over 31 years and that in 2007 the sedna region contained the thinnest ice of any part of the arctic surveyed by the submarine this was a region from which the ice completely retreated during the subsequent summer of 2007

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

arctic sea ice retreat in 2007 follows thinning trend the minimum of arctic sea ice extent in the summer of 2007 was unprecedented in the historical record a coupled ice ocean model is used to determine the state of the ice and ocean over the past 29 yr to investigate the causes of this ice extent minimum within a historical perspective it is found that even though the 2007 ice extent was strongly anomalous the loss in total ice mass was not rather the 2007 ice mass loss is largely consistent with a steady decrease in ice thickness that began in 1987 since then the simulated mean september ice thickness within the arctic ocean has declined from 3 7 to 2 6 m at a rate of 0 57 m decade 1 both the area coverage of thin ice at the beginning of the melt season and the total volume of ice lost in the summer have been steadily increasing the combined impact of these two trends caused a large reduction in the september mean ice concentration in the arctic ocean this created conditions during the summer of 2007 that allowed persistent winds to push the remaining ice from the pacific side to the atlantic side of the basin and more than usual into the greenland sea this exposed large areas of open water resulting in the record ice extent anomaly

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

the long term strength of europe and its implications for plate forming processes field based geological studies show that continental deformation preferentially occurs in young tectonic provinces rather than in old cratons this partitioning of deformation suggests that the cratons are stronger than surrounding younger phanerozoic provinces however although archaean and phanerozoic lithosphere differ in their thickness and composition their relative strength is a matter of much debate one proxy of strength is the effective elastic thickness of the lithosphere te unfortunately spatial variations in te are not well understood as different methods yield different results the differences are most apparent in cratons where the bouguer coherence method yields large te values 60 km whereas the free air admittance method yields low values or 1 5 gyr old is much larger mean te 60 km than that of younger lithosphere mean te 30 km we propose that this strength difference reflects changes in lithospheric plate structure thickness geothermal gradient and composition that result from mantle temperature and volatile content decrease through earth s history

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

time dependent thermal state of the lithosphere in the foreland of the eastern carpathians bend insights from new geothermal measurements and modelling results summary the time dependent heat budget thermal evolution and rheology of the lithosphere in the last 13myr along a 120 km long profile in the foreland of the eastern carpathians bend is presented the study area a complex tectonic environment in the vicinity of the wellknown intermediate depth seismogenic vrancea zone includes the deepest sedimentary basin in romania 18 km with a recent rapid evolution in the last 13myr 8 km of sediments detailed high resolution temperature logs in the depth ranges from 0 700 m to 0 2400 m in eight thermally stabilized boreholes together with logging and geological information on structure lithology and time evolution of the sedimentary pile have been used to model the thermal evolution by means of a 2 d finite element model which includes sedimentation history sediment compaction lateral and vertical variation of thermal properties of sediments and consolidated crust modelling results have been compared to measured temperatures corrected for palaeoclimate effects in a trial and error iterative approach sedimentation palaeoclimate undercompaction and heat refraction effects on one hand and the heat generated in the upper crust on the other combine to explain the observed subsurface temperature field and in particular the pronounced curvature of the vertical temperature profiles the neogene quaternary sedimentation resulted in a rather uniform deficit of the surface heat flux of about 12 mw m 2 in the study area in spite of the marked lateral variation of the sedimentary pile thickness the palaeoclimate effect is responsible for a surface heat flux depression of 7 8 mw m 2 uniform along the study profile unlike older sedimentary basins in the study area transient sedimentation thermal effects add to palaeoclimate effects in establishing the temperature field in the depth range of geothermal measurements the lateral variation of the palaeoclimatically corrected surface heat flux from the centre of the focsani depression 40 mw m 2 to its margin and the foreland platform 70 mw m 2 is mainly the result of the lateral variation of the heat produced in the upper crust where thickness varies from 7 to 21 km respectively a heat production of 2 3 wm 3 for the southeastern end of the profile and of 2 15 wm 3 for the rest of it has been modelled as a result of the sedimentation process temperature variations as large as 70 100 c occurred in the pre neogene sediments and the crystalline crust immediately under the sedimentary pile with consequences on the metamorphic state and rheological behaviour of the foreland

the arctic ice thickness anomaly of the 1990s a consistent view from observations and models 1 observations of sea ice draft from submarine cruises in much of the arctic ocean show that the ice cover was unusually thin in the mid 1990s here we limit our examination to digitally recorded draft data from eight cruises spanning the years 1987 to 1997 and find a decrease of about 1 m over the 11 year span comparisons of our modeled draft with observed draft show good agreement in the temporal change comparing average draft over entire cruises the rms discrepancy between modeled and observed draft is 0 3 m and the correlation is 0 98 agreement in the spatial patterns of draft is somewhat lower the rms discrepancy of 50 km averages of draft is 0 7 m and the correlation is 0 73 we review reports of interannual variations of ice thickness or volume from other model studies all models agree that thickness decreased by between 0 6 and 0 9 m from 1987 to 1996 our model shows a modest recovery in thickness from 1996 to 1999 for the 1950s 1960s and 1970s models tend to disagree on the size and to a lesser extent the timing or phase of interannual variations

north atlantic control on precipitation pattern in the eastern mediterranean black sea region during the last glacial based on proxy records from western black sea cores we provide a comprehensive study of climate change during the last glacial maximum and late glacial period in the black sea region for the first time we present a record of relative changes in precipitation for nw anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration the good correspondence between reconstructed rainfall intensity in nw anatolia and past western mediterranean sea surface temperatures ssts implies that during the glacial period the precipitation variability was controlled like today by mediterranean cyclonic disturbances periods of reduced precipitation correlate well with low ssts in the mediterranean related to heinrich events h1 and h2 stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater sediment source concomitant to the meltwater inflow after 16 4 cal ka bp this change implies intensification of the northern sediment source and with other records from the mediterranean region consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the european continent the early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the mediterranean region leading simultaneously to more humid conditions in central and northern europe

reduced ice thickness in arctic transpolar drift favors rapid ice retreat 1 helicopter borne electromagnetic sea ice thickness measurements were performed over the transpolar drift in late summers of 2001 2004 and 2007 continuing ground based measurements since 1991 these show an ongoing reduction of modal and mean ice thicknesses in the region of the north pole of up to 53 and 44 respectively since 2001 a buoy derived ice age model showed that the thinning was mainly due to a regime shift from predominantly multi and second year ice in earlier years to first year ice in 2007 which had modal and mean summer thicknesses of 0 9 and 1 27 m measurements of second year ice which still persisted at the north pole in april 2007 indicate a reduction of late summer second year modal and mean ice thicknesses since 2001 of 20 and 25 to 1 65 and 1 81 m respectively the regime shift to younger and thinner ice could soon result in an ice free north pole during summer