influences of sea ice on the eastern bering sea ncar cesm simulations and comparison with observations abstract we examine the influences of sea ice on the eastern bering sea ebs regional oceanography on seasonal and inter annual time scales using the national center for atmospheric research community earth system model ncar cesm simulations comparing the modeling results with satellite and in situ observations when possible while the modeled mean seasonal cycle of ice cover in the ebs middle shelf is generally within the uncertainty range of satellite observations in the northern domain north of 59 n the simulation reaches its annual maximum in april instead of in march as observed by satellite remote sensing modeled ice reduction in late spring in the region is also slower than observations despite this bias the simulation captures the observed seasonal transit of freshwater from the north to the south via ice advection en route the sea ice melts cooling and freshening the local water column on inter annual time scales modeling results suggest that extensive ice cover persisting into spring in the central ebs leads to cold anomalies in the bottom water especially on the middle and inner shelves of the southern domain the corresponding salinity anomalies are positive in the northern coastal domain and weak but negative in the southern middle shelf the associated 10 m ocean current anomalies are southward on the shelf and directed offshore in the slope region comparing years 1961 2005 versus years 2005 2050 the probability distribution function of ice cover on the ebs middle shelf shifts northward by 2 latitude

hydrological factors in the interpretation of stable isotopic proxy data present and past a european perspective in the context of this paper stable isotopic proxies are those preserving directly or via known or calculable fractionation factors a record of 18o 16o and or 2h 1h in the water which contributed to their growth suitable proxies include amongst others tree ring cellulose bone phosphate lake sediment minerals and speleothem fluid inclusions a principal aim of studying isotopic proxies is to gain more information about past climates through a knowledge of how rainfall isotope compositions have changed over time however converting back from proxy to rainfall is not necessarily straightforward because however well the isotopic fractionation due to proxy growth or formation is understood a variety of modifying processes may have intervened between this and the actual rainfall events three main reservoirs of environmental water may contribute to the isotopic compositions of terrestrial proxy indicators surface waters soil moisture and groundwater each of these can in principle be isotopically modified compared to rainfall in the locality this review examines these effects and how they may change under different european climate types at the present day it is concluded that while groundwater isotopic compositions typically represent closely the bulk composition of rainfall under a variety of climatic regimes soil and particularly lake waters require detailed study if their isotope systematics are to be adequately understood the review also finds that to a large extent the present is the key to the past in terms of recharge processes during the late pleistocene though glaciation may have had profound isotopic consequences in certain areas while a more general aridity led to the apparent absence of recharge in most areas for much of the late devensian

global glacial isostatic adjustment palaeogeodetic and space geodetic tests of the ice 4g vm2 model analyses of the global process of glacial isostatic adjustment and post glacial relative sea level change continue to deliver important insights into earth system form and process one successful model of the related phenomenology is based upon a spherically symmetric internal viscoelastic structure for the solid earth which has been denoted vm2 and a model of the most recent deglaciation event of the current ice age denoted ice 4g the primary purpose of this paper is to describe several new a posteriori tests that have recently been performed to further investigate the quality of this global solution to the inverse problem for both mantle viscosity and deglaciation history that is posed by the observables associated with this large scale geodynamic phenomenon i focus especially upon the misfits of observations to the theoretical predictions of this model which i am currently using to further refine its properties and upon predictions made using it of geophysical signals that should soon become visible in the context of the gravity recovery and climate experiment grace satellite mission among the required refinements to ice 4g one that is necessary to eliminate a recently revealed misfit to space geodetic constraints on the present day rate of radial motion at the yellowknife location well to the west of hudson bay and a similar misfit to absolute gravity measurements to the southwest of the bay is the insertion of a keewatin dome of thick ice centred over yellowknife with a ridge of ice extending to the south east in the geomorphological literature the existence of such a keewatin dome previously has been hypothesised but chronological control was lacking on the surface features that suggested its former existence an important additional constraint that requires the late glacial existence of this important feature consists of new inferences of the last glacial maximum lowstand of the sea from sites in the far field of the main concentrations of land ice copyright 2002 john wiley sons ltd

winter currents and hydrographic conditions on the northern central bering sea shelf current observations obtained from the northern bering shelf region in winter 1984 1985 indicate that midwinter circulation patterns differed from those during the rest of the year annual mean circulation in this region is dominated by vigorous northward currents from 10 cm s in shpanberg strait to more than 50 cm s in bering strait these northward currents are accompanied by a weak northwestward coastal flow south of st lawrence island in february april 1985 however flow was weakly 0 5 cm s southward through shpanberg strait and southeastward south of st lawrence island while remaining northward through anadyr and bering straits comparison with current data obtained from previous years suggests that midwinter reversal of flow in shpanberg strait is a recurrent winter feature it generally occurs at about the same time that the winter ice cover undergoes its major advance and it is associated with strong northerly winds northward flow through anadyr strait persists conversely through the winter and is the northward extension of a western intensified northward flow over the bering shelf its source is bering sea water farther south rather than water from the northern central shelf the resultant trapping of shelf water on the northern central shelf coupled with intensive regional ice formation during the same period as the flow reversal led in 1985 to significant about 1 5 brine enrichment this salinity increase agrees qualitatively with historical data which suggest that the northern central bering shelf is the site both of sluggish winter circulation and of elevated salinities due to brine enrichment from ice formation

radial profile of mantle viscosity results from the joint inversion of convection and postglacial rebound observables we present new inferences of the radial profile of mantle viscosity that simultaneously fit long wavelength free air gravity harmonics associated with mantle convection and a large set of decay times estimated from the postglacial uplift of sites within previously glaciated regions hudson bay arctic canada and fennoscandia the relative sea level variation at these latter sites is constrained by age height pairs obtained by geological survey rather than the subjective trends which are commonly used in glacial isostatic adjustment gia studies our viscosity inferences are generated using two approaches first we adopt a relative viscosity profile which is known to provide a good fit to the free air gravity harmonics and determine an absolute scaling which yields a best fit to the gia decay time constraints second we perform an iterative nonlinear joint inversion of the two data sets in both cases our inferred profiles are characterized by a significant increase of viscosity 2 orders of magnitude with depth to values of 1022 pa s in the bottom half of the lower mantle the new viscosity profiles are shown to satisfy constraints based on the postglacial uplift of both fennoscandia the classic haskell 1935 number and hudson bay which have commonly been invoked to argue for an isoviscous mantle furthermore the models are used to predict a set of long wavelength signatures of the gia process these include predictions of gia induced variations in 1 the length of day over the late holocene period 2 the earth s precession constant and obliquity over the last 2 6 myr and 3 the present day zonal harmonics of the geopotential jl l 7 the predictions 1 and 3 bound the late holocene and ongoing mass flux between the large polar ice sheets greenland and antarctic and the global oceans to small values 0 4 mm yr equivalent eustatic sea level rise

recharge sources and hydrogeological effects of irrigation and an influent river identified by stable isotopes in the motril salobrena aquifer southern spain measurement of the stable isotopes oxygen 18 and deuterium in water is an important tool to characterize aquifer recharge sources in the driest areas of the mediterranean this application is of special interest due to the scarcity of water and the resulting common incidence of human influence on natural hydrological systems the motril salobrena detrital aquifer southern spain is a clear example of such an impact as inhabitants have designed irrigation systems and a dam was recently built across the course of the guadalfeo river which feeds the aquifer the sampling of river or ground water has allowed the determination of stable isotope contents oxygen 18 and deuterium both temporally and spatially and the relative importance of the main recharge sources in certain sectors in addition we were able to infer seasonal trends and to improve existing knowledge of the main flow paths and the position of a seasonal groundwater divide data analysis shows evaporation plays a minor role despite the high temperatures in the zone scarce rainwater influence and the overwhelming contribution of recharge from the guadalfeo river and from the carbonate aquifer escalate aquifer in contact with the motril salobrena aquifer irrigation return flow during the summer months comprises the main recharge due to the significant volumes of water that infiltrate the construction of the dam will almost certainly entail great changes in the current dynamics of the hydrogeology of the motril salobrena aquifer therefore knowledge of its behaviour is crucial in order to carry out sustainable use of its groundwater resources copyright 2011 john wiley sons ltd

rheology of the upper mantle a synthesis rheological properties of the upper mantle of the earth play an important role in the dynamics of the lithosphere and asthenosphere however such fundamental issues as the dominant mechanisms of flow have not been well resolved a synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the earth s upper mantle the hot and shallow upper mantle flows by dislocation creep whereas cold and shallow or deep upper mantle may flow by diffusion creep when the stress increases grain size is reduced and the upper mantle near the transition between these two regimes is weakened consequently deformation is localized and the upper mantle is decoupled mechanically near these depths

currents and transport on the eastern bering sea shelf an integration of over 20 years of data abstract more than 20 years of data from moorings satellite tracked drifters and hydrographic surveys are integrated to provide a comprehensive view of currents and transport on the eastern bering sea shelf the major sources of water onto the eastern bering sea shelf are north pacific water flowing through unimak pass and bering slope water flowing onto the shelf usually via the canyons that intersect the shelf break absolute geostrophic transport through unimak pass varies from an average of 0 25 106 m3 s 1 sv in the warm months to 0 43 sv in the cold months flow along the 50 m isobath is weak with a transport of 13 months and from amukta pass to bering strait via the bering slope current is 8 months consequently the source of most of the heat transported into the arctic through bering strait is a result of air sea interactions local to the northern bering sea analysis of the currents and water properties on the southern shelf indicates that 50 of the shelf water is exchanged with slope water during october january each year this exchange elevates the october mid shelf average nitrate level from 6 m to 14 16 m by the end of january

3 d water properties and geostrophic circulation on the eastern bering sea shelf abstract the national oceanic and atmospheric administration s noaa alaska fisheries science center bottom trawl survey samples demersal fish at over 350 sites on the eastern bering sea continental shelf each summer on a 37 37 km 2 grid rugged conductivity temperature depth sensors ctds were added to the net hauls to obtain gridded data sets of temperature and salinity measurements for 2008 2010 results reveal the three dimensional thermohaline structure of the shelf including the cold pool and areas of fresher water around st matthew island and in bristol bay horizontal gradients are often strongest roughly along the 50 m and 100 m isobaths that traditionally separate the inner and outer shelf from the middle shelf centered along the 70 m isobath the summer mixed layer depth is less than 30 m over much of the region it reaches the bottom along the alaska peninsula in water depths greater than 70 m showing that the boundary of the well mixed inner shelf is not always at the 50 m isobath the greatest upper to lower layer density difference is found across the shelf north of 59 n the salinity difference is the main contributor to this density difference over most of the region in 2008 and 2010 but the temperature difference dominates in 2009 due to decreased ice melt and reduced freshening near st matthew island the geostrophic velocity relative to the bottom shows northwestward flow seaward of the 100 m isobath and northwestward transports integrated across the shelf of 0 10 0 25 10 6 m 3 s in 2008 and 2010 there was clockwise circulation in a region of less saline water around st matthew island in 2009 that fresher lens did not exist and flow was more concentrated along the 100 m isobath bringing saltier water across the shelf

observed increases in bering strait oceanic fluxes from the pacific to the arctic from 2001 to 2011 and their impacts on the arctic ocean water column 1 mooring data indicate the bering strait throughflow increases 50 from 2001 0 7 sv to 2011 1 1 sv driving heat and freshwater flux increases increase in the pacific arctic pressure head explains two thirds of the change the rest being attributable to weaker local winds the 2011 heat flux 5 1020j approaches the previous record high 2007 due to transport increases and warmer lower layer ll temperatures despite surface temperature sst cooling in the last decade warmer ll waters arrive earlier 1 6 1 1 days yr though winds and sst are typical for recent decades maximum summer salinities likely set in the bering sea remain remarkably constant 33 1 psu over the decade elucidating the stable salinity of the western arctic cold halocline despite this freshwater flux variability strongly driven by transport exceeds variability in other arctic freshwater sources remote data winds sst prove insufficient for quantifying variability indicating interannual change can still only be assessed by in situ year round measurements

circulation on the north central chukchi sea shelf abstract mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central chukchi shelf previous studies indicated that pacific waters crossed the chukchi shelf through herald valley in the west and barrow canyon in the east we find a third branch through the central channel onto the outer shelf the central channel transport varies seasonally in phase with bering strait transport and is 0 2 sv on average although some of this might include water entrained from the outflow through herald valley a portion of the central channel outflow moves eastward and converges with the alaskan coastal current at the head of barrow canyon the remainder appears to continue northeastward over the central outer shelf toward the shelfbreak joined by outflow from herald valley the mean flow opposes the prevailing winds and is primarily forced by the sea level slope between the pacific and arctic oceans current variations are mainly wind forced but baroclinic forcing associated with upstream dense water formation in coastal polynyas might occasionally be important winter water mass modification depends crucially on the fall and winter winds which control seasonal ice development an extensive fall ice cover delays cooling limits new ice formation and results in little salinization in such years bering shelf waters cross the chukchi shelf with little modification in contrast extensive open water in fall leads to early and rapid cooling and if accompanied by vigorous ice production within coastal polynyas results in the production of high salinity 33 shelf waters such interannual variability likely affects slope processes and the transport of pacific waters into the arctic ocean interior

oxygen and hydrogen isotopes for the characteristics of groundwater recharge a case study from the chih pen creek basin taiwan assessing the seasonal variation of groundwater recharge is important for effective management of groundwater resources stable isotopes of oxygen and hydrogen were used to estimate the sources of groundwater and seasonal contributions of precipitation to groundwater recharge in chih pen creek basin of eastern taiwan based on the isotopes of precipitation n 177 two different local meteoric water regression lines lmwl can be obtained for the different seasons d 8 0618o 10 08 for wet season precipitation may through october and d 8 65 18o 17 09 for dry season precipitation november through april the slope and intercept of regression line for wet season precipitation are virtually identical to the global meteoric water line gmwl of craig 1961 in contrast to during dry season precipitation due to evaporation effect the intercept of 17 09 is much higher than of the gmwl of 10 the results show the stable isotopes compositions of precipitation decrease with increasing rainfall amount and air temperature due to the amount effect of precipitation is pronounced the amount effect is clearly but do not show the temperature effect from january to december 2007 using a mass balance equation a comparison of deuterium excess or d values of precipitation and groundwater indicates the groundwater consist of 76 wet season precipitation and 24 dry season precipitation representing a distinct seasonal variation of groundwater recharge in study area about 79 of the groundwater is recharged from the river water of the mountain watershed and 21 is from the rain that falls on the basin

mantle viscosity and ice age ice sheet topography ice age paleotopography and mantle viscosity can both be inferred from observations of earth s response to the most recent deglaciation event of the current ice age this procedure requires iterative application of a theoretical model of the global process of glacial isostatic adjustment results demonstrate that the iterative inversion procedure converges to a paleotopography that is extremely close to that from the ice 4g model the accompanying mantle viscosity profile is furthermore shown to reconcile the requirements of aspherical geoid anomalies related to the mantle convection process thus resolving a fundamental issue concerning mantle rheology the combined model also explains postglacial sea level histories for the east coast of the united states

rainfall recharge relationships within a karstic terrain in the eastern mediterranean semi arid region israel δ 18o and δd characteristics annual rainfall variations and processes in the upper vadose zone exert a profound influence on the chemical and isotopic compositions of waters of carbonate aquifers in semi arid climatic zones in order to define these processes we have studied the surface temperatures during rainfall events the isotopic composition of rain infiltrating and groundwaters this study was carried out within a karstic terrain soreq cave israel located in cenomanian dolomitic rocks approximately 40 km inland of the mediterranean sea and 400 m above sea level the climate is typical of the eastern mediterranean semi arid conditions with a rainy winter and dry summer and the average annual rainfall in the area is 500 mm close monitoring indicates that the d and 18o values of individual rainstorm events decrease with increasing rainfall annual average isotopic values of years with rainfall of 500 600 mm do not vary systematically years with extreme rainfall values define a negative covariation between the 18o and rainfall the d 18o relationship of all rain events of more than 20 mm fall on the mediterranean meteoric water line mmwl with a slope of 8 and d excesses of 20 30 these rain events occur when mid winter surface temperatures are 5 to 10 c rainfall events of less than 20 mm mainly occurring at above 10 c have slopes of less than 8 and smaller d excess as a consequence of evaporation processes beneath the clouds two main water types infiltrating into the cave are recognized slow and fast drip slow drip occurs from the tips of stalactites and takes place throughout the year these waters represent seepage water that remains in the upper vadose zone for up to several decades fast drip emanates from fissures in the cave roof during the winter seasons these waters represent vadose flow with a short residence time of less than 1 year the infiltration of the fast drip water into the cave depends on the fracture system of the rock cover and on the intensity of the rainstorms in the inner parts of the cave where the rock cover is thick fast drip starts only after several massive 20 mm rainstorms whereas below a thin roof the response time of fast drip is a few hours to a few days after intensive rainstorms both fast and slow drip water fall on the mmwl indicating that they are derived mainly from the relatively intensive rainstorms that compose about 23 of the annual rainfall although fast dri water represents massive rainstorms their 18o and d values are nonetheless higher by 1 and 10 respectively relative to the average rainwater compisition this indicates that the fast drip water consists predominantly of water derived from intensive rainstorms admixed with a minor component of isotopically 18o and d enriched water which is represented by the slow drip waters the fast drip waters are derived mainly from massive rain events at surface temperatures of 5 to 10 c which thermally equilibrate with the host rock and upon reaching the cave they have already acquired the mean temperature 20 c of the cave

withdrawn monthly isotopes δ18o and δd variations of meteoric waters in el kef region northwestern tunisia implications for changes of moisture sources

northward flow in the bering and chukchi seas the ocean circulation on the bering and chukchi sea shelves is investigated using a barotropic numerical model in the presence of the winter seasonal wind stress from the northeast observed northward transport through bering strait of 0 6 sv for the 8 month winter season 1981 1982 can be driven by a sea level difference of 0 4 m between the pacific and arctic oceans this sea level difference between basins is in agreement with hydrographic estimates in the absence of wind stress a 0 4 m sea level difference drives a northward transport through bering strait of 1 1 sv maximum transport through bering strait is geostrophically limited not frictionally or inertially limited major qualitative circulation features of the region are evident in the simulations westward intensification of the northward transport across the bering sea shelf is confirmed with the major transport occurring in the relatively deep gulf of anadyr in the absence of wind anadyr strait contributes 72 of the northward transport through bering strait with northeasterly winds there is a net clockwise circulation around saint lawrence island within the 20 m isobath norton and kotzebue sounds are little influenced by the general circulation northward transport in the chukchi sea bifurcates in the vicinity of point hope the predominant branch is directed toward the northwest in a broad canyon feature south of herald shoal and the balance becomes the alaskan coastal current between cape lisburne and point barrow

temporal gravity variations near shrinking vatnajokull ice cap iceland repeated gravity measurements were carried out from 1991 until 1999 at sites se of vatnajokull iceland to estimate the mass flow and deformation accompanying the shrinking of the ice cap published gps data show an uplift of about 13 5 mm a near the ice margin a gravity decrease of 2 1 gal a relative to the hofn base station was observed for the same sites control measurements at the hofn station showed a gravity decrease of 2 0 5 gal a relative to the station rvik 5473 at reykjavik about 250 km from hofn this is compatible as a bouguer effect with a 10 3 mm a uplift rate of the igs point at hofn and an uplift rate of 20 mm a near the ice margin although the derived gravity change rates at individual sites have large uncertainties the ensemble of the rates varies systematically and significantly with distance from the ice the relationship between gravity and elevation changes and the shrinking ice mass is modelled as response to the loading history the gps data can be explained by 1 d modelling i e an earth model with a 15 km thick elastic lithosphere and a 7 1017 pa s asthenosphere viscosity but not the gravity data based on 2 d modelling the gravity data favour a low viscosity plume in the form of a cylinder of 80 km radius and 1017 to 1018 pa s viscosity below a 6 km thick elastic lid embedded in a layered prem type earth although the elevation data are less well explained by this model strain porosity hydrology effects are likely to enhance the magnitude of the gravity changes but need verification by drilling more accurate data may resolve the discrepancies or suggest improved models

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

groundwater development effects on different scale hydrogeological systems using head hydrochemical and isotopic data and implications for water resources management the selva basin ne spain hydrogeological resources in regional large scale groundwater systems are conditioned by their specific geological setting which defines their capacity to supply human demand and their potential to recover from human induced stress factors such as water withdrawal in this paper the hydrogeology of a range and basin hydrogeological system is described based on potentiometric hydrochemical and isotopic data in order to fulfill a twofold objective to characterize the alteration brought about in the hydrogeological system by intensive groundwater withdrawal where tectonic elements such as fault zones play a significant role in the flow behaviour and to define groundwater hydrodynamics under current human pressures as a necessary step to achieve appropriate groundwater management hydraulic head data indicate the relationships between geological formations in the range areas and the sedimentary infill of the basin in this set up fault zones and a fracture network have a direct effect on the recharge and allow upward vertical flow from the basement to the sedimentary aquifers hydrochemical and isotopic data support this observation the use of fluoride and nitrate as tracers for the contribution of deep and shallow flow systems provides a detailed portrait of the effects of pumping on the flow path distribution isotopic data depict seasonal trends in the water captured by wells in this connection we can differentiate between two distinct flow systems a regional large scale longer residence time system originating in the surrounding ranges and a local flow system constituted by infiltration in the lower areas of the basin the two systems with specific water qualities contribute differently to the resources that are withdrawn and their specific contributions in the frame of the basin water budget determine the potential for present sustainable water exploitation

unsaturated hydraulic conductivity in limestone dolines influence of vegetation and rock fragments abstract vegetation and rock fragments have a profound impact on runoff generation in the dolines of the sierra de gador southeastern spain this study investigated the effect of vegetation and rock fragments on unsaturated hydraulic conductivity k h in three limestone dolines and examined whether variation in k h was consistent with differences in runoff from simulated rainfall tension infiltrometers were used to measure unsaturated hydraulic conductivity at three pressure heads h of 30 60 and 120 mm at 70 locations within the three dolines generally the trends of the k h were consistent with the simulated rainfall data and accounted for difference in runoff for the vegetated surfaces vegetation resulted in high infiltration with unsaturated hydraulic conductivities at 30 and 60 mm are significantly greater for the vegetated surface than for the rock fragment covered surface and bare soil surface rock fragments had no obvious effect on soil hydraulic conductivity as compared with bare soils the k h of the non crusted soil were 2 5 times higher than that of the crusted soil the k h decreased with increasing tensions k 60 and k 120 were only 8 4 and 0 89 respectively of k 30 for the vegetated surfaces and were about 30 and 8 7 respectively of k 30 for both rock fragment covered surfaces and bare soils suggesting that pores in the 0 5 to 1 mm diameter range dominate flow under unsaturated conditions there were significant differences in k h among the different topographic units of the dolines and k h tended to be higher in the upper position than in the lower position of the doline

interannual variability of summer biochemical enhancement in relation to mesoscale eddies at the shelf break in the vicinity of the pribilof islands bering sea abstract this study examined variability of the eddy field and primary production over the bering sea s eastern shelf break area during summer using a satellite multi sensor data set the eddy field and on shelf nutrient flux below 50 m water depth were also investigated using a numerical model the satellite altimeter data analysis and numerical experiments indicated that the eddy field was induced by perturbations of the bering slope current system and or instabilities in the bering sea basin via flow through the aleutian passes the distribution of high primary production roughly coincided with the high variability area of the eddy field numerical experiments showed a 70 increase in net on shelf flux and 54 increase in net on shelf transport by the generation propagation of eddies along the shelf break at pribilof canyon towed ctd fluorometer measurements during the summer of 2003 revealed a stable water column and high fluorescence 10 g l 1 in the area between the 200 and 1000 m isobaths at a time when there was a low level of on shelf flux regardless of the eddy field conversely the eddy induced on shelf flux and stable water column can enhance primary production from spring to summer at the shelf break moreover the eddy induced on shelf nutrient flux probably contributes to the primary productivity at the western shelf of the pribilof islands where the bering sea ecosystem is very dynamic this eddy related shelf break process can be applied to not only the bering sea shelf break but also all shelf break areas in which propagating eddies are found

intensive agriculture wetlands quarries and water management a case study campo de dalias se spain the intensive agricultural activities that have developed over the last 50 years in the campo de dalias almeria region have required large quantities of gravel and clay as the basic materials for the substrate over which crops are raised with this motive numerous gravel pits have been opened that have extracted several million cubic metres of material in recent years similar quantities of clay have been extracted from the distal sectors of the alluvial fans that descend from the sierra de gador and from within a large endoreic basin in the latter quarries some wetlands have developed probably because of the rise in the water table level in the aquifer over which they lie the gravel pits are situated in the apical sectors of the alluvial fans overlying hydrogeological units that are widely overexploited for this reason the gravel pits could be used for artificial recharge in addition to increasing the availability of water in the aquifer the risk of catastrophic flooding would also be reduced

origin of the groundwater salinity and geochemical processes in detrital and carbonate aquifers case of chougafiya basin central tunisia summary comprehensive investigations of groundwaters were performed in the detrital and carbonate aquifers of the chougafiya basin central tunisia in the present review hydrochemistry and isotopic tools were combined to get an insight into the processes controlling mineralization recharge conditions flow pattern of groundwater and c chemistry in the investigated hydrological system analysis of the dissolved constituents revealed that several processes controlled the observed chemical composition i the dissolution of evaporitic minerals ii cation exchange reactions iii sulfate reduction under anaerobic conditions iv incongruent dissolution of carbonate minerals calcite dolomite coupled with gypsum dissolution and calcite precipitation and v silicates weathering data inferred from 18o and deuterium isotopes in groundwater samples indicated recharge with modern rainfall water characterized by lower 18o and 2h values is interpreted as recharged by non evaporated rainfall originating from mediterranean and atlantic air masses however water with relatively enriched 18o and 2h contents is thought to reflect the occurrence of an evaporation process related to the long term practice of flood irrigation the radiogenic 3h isotope data provided insight into the presence of two recharge periods in the investigated groundwaters waters with 3h contents of 1 tu clearly suggested the occurrence of a contemporaneous recharge probably during the last two decades carbon isotopes provided some insights into the timescales of groundwater flow but mainly revealed that main sources of c are active in the system these are likely dissolved biogenic co2 carbonate dissolution and incongruent reaction of the carbonate matrix mean residence times were determined after correction of the initial activities for dead c from the rock matrix and suggest ages ranging from the present day to the holocene in both upper cretaceous and mio pliocene groundwaters

constraints on a plume in the mid mantle beneath the iceland region from seismic array data teleseismic p waves passing through low wave speed bodies in the mantle are refracted causing anomalies in their propagation directions that can be measured by seismometer arrays waves from earthquakes in the eastern pacific and western north america arriving at the norsar array in norway and at seismic stations in scotland pass beneath the iceland region at depths of 1000 2000 km waves arriving at norsar have anomalous arrival azimuths consistent with a low wave speed body at a depth of 1500 km beneath the iceland faeroe ridge with a maximum diameter of 250 km and a maximum wave speed contrast of 1 5 per cent this agrees well with whole mantle tomography results which image a low wave speed body at this location with a diameter of 500 km and a wave speed anomaly of 0 5 per cent bearing in mind that whole mantle tomography because of its limited resolution broadens and weakens small anomalies the observations cannot resolve the location of the body and the anomaly could be caused in whole or in part by larger bodies farther away for example by a body imaged beneath greenland by whole mantle tomography

dynamic topography of the ice covered arctic ocean from icesat 1 we construct the dynamic ocean topography dot of the arctic ocean for five icesat campaigns winter of 2004 2008 using sea surface height estimates in open leads results show that the mean winter dot over the arctic ocean varies by 1 m and features a distinct dome of 40 cm over the beaufort sea standard deviation of the mean field is 20 cm spatial coherence between the five winter dots is consistently high 0 9 whereas the coherence between the dots and the winter djfm sea level pressure fields over the arctic basin is variable this suggests persistence of the underlying hydrodynamic processes at interannual time scales compared to seasonal atmospheric forcing comparison of dynamic heights dh from hydrographic surveys and the dot in 2008 shows a remarkable correlation of 0 92 the geostrophic velocity fields computed from the dot and interpolated dh fields highlight the smaller scale oceanographic features in the satellite estimates

factors influencing physical structure and lower trophic levels of the eastern bering sea shelf in 2005 sea ice tides and winds abstract in spring and fall 2005 cross and along shelf transects were sampled to evaluate the influence of physical forcing including sea ice tides and winds on the lower trophic levels of the bering sea ecosystem the hydrography nutrients chlorophyll and zooplankton abundance and species composition were all affected by the presence or absence of sea ice on a north south transect along the 70 m isobath in may shelf waters between 59 n and 62 n were cold and relatively fresh and benthic invertebrate larvae and chaetognaths were a significant fraction of the zooplankton community while to the south the water was warmer saltier and the zooplankton community was dominated by copepods the position of the transition between ice affected and ice free portions of the shelf was consistent among temperature salinity nutrients and oxygen this transition in the hydrographic variables persisted through the summer but it shifted 150 km northward as the season progressed while a transition also occurred in zooplankton species composition it was farther north than the physical chemical transition and did not persist through the summer mooring data demonstrated that the change in the position of the transition in physical and chemical properties was due to northward or eastward advection of water onto and across the shelf from south to north along the 70 m isobath tidal energy decreased resulting in a less sharply stratified water column on the northern portion of the middle shelf as opposed to a well defined two layered system in the southern portion this more gradual stratification in the north permitted a greater response to mixing from winds which were homogeneous from north to south thus the physical and biological structure at any one location over the middle shelf is dynamic over the course of a year and results from a combination of in situ processes and climate mediated regional forcing which is dominated in most years by sea ice

glacio isostatic crustal movements caused by historical volume change of the vatnajokull ice cap iceland measurements of the lake level of lake langisjor at the sw edge of the vatnajokull ice cap indicate a tilt of 0 26 0 06 rad year away from the ice cap in the years 1959 1991 the tilt is too large to be explained as an elastic earth response to ice retreat this century or to be caused by change in the gravitational pull of the ice cap but it can be explained by sub lithospheric viscous adjustment regional subsidence in historical times in se iceland can similarly be attributed to viscous adjustment resulting from the increased load of vatnajokull during the little ice age the inferred sub lithospheric viscosity is 1 1018 5 1019 pa s

coastal fresh water discharge in the northeast pacific very high annual rates of precipitation in the coastal mountains that border the northeast pacific ocean produce large fresh water discharges 23000 m3 s 1 this discharge has been ignored previously since it does not enter the ocean in the form of large rivers but instead the water enters by way of numerous small rivers and streams thus it acts as a line source instead of a point source this coastal discharge contributes at least 40 of the fresh water that enters the northeast pacific from the atmosphere the discharge is comparable to the mean annual discharge of the mississippi river system the fresh water creates a cross shelf density gradient that drives an alongshore baroclinic jet the width of this jet is less than 25 km with speeds in excess of 100 cm s 1 it extends along the coast from southeast alaska to at least kodiak island apparently the flow is maintained as a narrow current adjacent to the coast by wind stress that causes downwelling conditions here throughout most of the year

iceland rising solid earth response to ice retreat inferred from satellite radar interferometry and visocelastic modeling a broad uplift occurs in iceland in response to the retreat of ice caps which began circa 1890 until now this deformation signal has been measured primarily using gps at points some distance away from the ice caps here for the first time we use satellite radar interferometry interferometric synthetic aperture radar to constrain uplift of the ground all the way up to the edge of the largest ice cap vatnajokull this allows for improved constraints on the earth rheology both the thickness of the uppermost earth layer that responds only in an elastic manner and the viscosity below it the interferometric synthetic aperture radar velocities indicate a maximum displacement rate of 24 4 and 31 4 mm yr at the edge of vatnajokull during 1995 2002 and 2004 2009 respectively the fastest rates occur at outlet glaciers of low elevation where ice retreat is high we compare the observations with glacial isostatic adjustment models that include the deglaciation history of the icelandic ice caps since 1890 and two earth layers using a bayesian approach we derived probability density functions for the average earth model parameters for three satellite tracks based on our assumptions the three best fit models give elastic thicknesses in the range of 15 40 km and viscosities ranging from 4 10 1018 pa s

recharge sources and hydrogeochemical evolution of groundwater in semiarid and karstic environments a field study in the granada basin southern spain abstract the objective of this study is to refine the understanding of recharge processes in watersheds representative for karstic semiarid areas by means of stable isotope analysis and hydrogeochemistry the study focuses on the granada aquifer system which is located in an intramontane basin bounded by high mountain ranges providing elevation differences of almost 2900 m these altitude gradients lead to important temperature and precipitation gradients and provide excellent conditions for the application of stable isotopes of water whose composition depends mainly on temperature samples of rain snow surface water and groundwater were collected at 154 locations for stable isotope studies 18 o d and in the case of ground and surface waters also for major and minor ion analysis thirty seven springs were sampled between 2 and 5 times from october 2004 to march 2005 along an altitudinal gradient from 552 masl in the granada basin to 2156 masl in sierra nevada nine groundwater samples were taken from the discharge of operating wells in the granada basin which are all located between 540 and 728 masl the two main rivers were monitored every 2 3 weeks at three different altitudes rainfall being scarce during the sampling period precipitation could only be sampled during four rainfall events calculated recharge altitudes of springs showed that source areas of mainly snowmelt recharge are generally located between 1600 and 2000 masl the isotope compositions of spring water indicate water sources from the western mediterranean as well as from the atlantic without indicating a seasonal trend the isotope pattern of the quaternary aquifer reflects the spatial separation of different sources of recharge which occur mainly by bankfiltration of the main rivers isotopic signatures in the southeastern part of the aquifer indicate a considerable recharge contribution by subsurface flow discharged from the adjacent carbonate aquifer no evaporation effects due to agricultural irrigation were detected

stratification on the eastern bering sea shelf revisited abstract the timing and magnitude of stratification can have profound influences on the marine ecosystem on the eastern bering sea shelf in the absence of strong wind mixing stratification can be initiated by the melting of seasonal sea ice or by springtime warming of the surface temperature and salinity both influence the stratification of the eastern bering sea shelf with their relative importance varying spatially and temporally in the northern middle shelf domain north of 60 n salinity stratification is often as important as temperature stratification on the southern middle shelf while the influence of temperature on stratification dominates during summer the influence of salinity stratification plays a role in the interannual variability mooring 2 m2 56 9 n 164 1 w has been deployed at 70 m depth in the southern middle shelf domain since 1995 data from this mooring show that stratification typically begins to set up in may and to break down in september october but these dates can vary by 30 d while no trend is found in the timing of the spring setup the fall stratification breakdown exhibited a trend toward later breakdown 2 d later per year from 1996 to 2009 results suggest that it may be difficult to forecast stratification on the eastern bering sea shelf from climate models as simple indices of wind mixing or heat fluxes are not correlated with stratification contrary to intuition the strength of summer stratification is not correlated with depth averaged temperature warm years such as 2000 and 2001 can have low stratification and cold years such as 2007 can have very high stratification this decoupling of stratification and temperature has implications for forecasting the ecosystem in the face of climate change as we cannot assume that projections of a warmer climate simply imply higher stratification in the future

transport through unimak pass alaska we examined inflow through unimak pass 200 m deep which is the only major connection between the shelves of the north pacific ocean and the eastern bering sea geostrophic transport was generally northward from the gulf of alaska into the bering sea the flow through the pass appeared to be modulated by the seasonal cycle of freshwater discharge on shorter time scales transport also was affected by semi daily variations in tidal mixing this effect was significant and not anticipated near bottom currents measured from moorings were maximum during winter and significantly correlated r 0 7 with the alongshore winds although the flow through unimak pass transported some nutrients from the north pacific ocean the gulf of alaska shelf is not the major source of nutrients to the bering sea shelf

characteristics of isotope in precipitation river water and lake water in the manasarovar basin of qinghai tibet plateau the stable hydrogen and oxygen of lake river rain and snow waters were investigated to understand the water cycle characteristics of the drainage basin of manasarovar lake in tibet both d and 18o of river water are larger than those of lake water and the effect of altitude on both d and 18o is not very significant this phenomenon was suggested to occur because manasarovar basin is located in qinghai tibet plateau which has low latitude high altitude abundant glaciers thin air and intensive solar radiation resulting in higher evaporation in lake water

sea ice and water column structure on the eastern bering sea shelf abstract seasonal sea ice is a defining characteristic of the eastern bering sea shelf and plays a critical role in determining the vertical structure of temperature and salinity over this shelf ice movement relative to local winds ice composition and the impact of both arrival and retreat of ice on the water column at four mooring sites over the middle shelf are examined ice forms primarily in coastal regions and is advected over the southern and outer shelves ice drift from satellite data for two representative years 2003 and 2007 was 2 of local ncep wind speed and oriented 44 to the right of the winds r 2 0 25 measurements from 30 ice cores collected in 2006 2009 gave an average salinity of 5 62 0 88 and an average nitrate concentration of 0 99 0 83 m time series data collected at the biophysical moorings in the bering sea 1995 2012 were used to explore the evolution of the water column under ice at the northern mooring m8 the water column had mixed and cooled to 1 c prior to the arrival of ice little melt occurred after ice arrival at the other three moorings the ocean temperature was 2 4 c when ice arrived resulting in extensive melt melting ice freshened and cooled the upper water column resulting in stratification which persisted for 10 25 days wind induced water column mixing occurred more slowly under the ice than in ice free waters an estimated 1 4 m of ice melted with the first arrival of ice at the three southern moorings where the latent heat of fusion accounted for approximately half the observed cooling during ice retreat there appeared to be little ice melt around the southern two moorings but an estimated 0 8 m at m5 and m8 the extent of ice melt sets up the water column for the following summer

a benchmark study for glacial isostatic adjustment codes the study of glacial isostatic adjustment gia is gaining an increasingly im portant role within the geophysical community understanding the response of the earth to loading is crucial in various contexts ranging from the the interpretation of modern satellite geodetic measurements e g grace and goce to the projections of future sea level trends in response to climate change modern modeling approaches to gia are based on various techniques that range from purely analytical formulations to fully numerical methods despite various teams independently investigating gia we do not have a suitably large set of explicitly validated numerical results through which they may be validated a community benchmark data set would clearly be valuable following the example of the mantle convection community here we present for the first time the results of a benchmark study of codes designed to model gia the approaches benchmarked are based on significantly different codes and different techniques this effort is performed within the working group 4 wg4 of the esf cost action es0701 improved constraints on models of glacial isostatic adjustment our aims are i testing the codes currently in use by the various teams ii establish a sufficiently large set of agreed results iii correct possible systematic errors embedded in the various physical formulations or computer implementations and iv facilitate the dissemination of numerical tools for surface loading studies to the community and to young scientists the test computations are mainly based on models with spherical symmetry and maxwell rheology and include inputs from various different methods and solution techniques viscoelastic normal modes spectral finite elements and finite elements the tests involve the loading and tidal love numbers and their relaxation spectra the deformation and gravity variations driven by surface loads characterized by simple geometry and time history and the rotational fluctuations in response to glacial unloading in spite of the significant differences in the numerical methods employed the test computations show a satisfactory agreement between the results provided by the participants most of the existing misfits have been addressed during the preparation of the manuscript some others are currently the subject of analysis within the wg4 community

climate controls on rainfall isotopes and their effects on cave drip water and speleothem growth the case of molinos cave teruel ne spain the interpretation of stable isotopes in speleothems in terms of past temperature variability or precipitation rates requires a comprehensive understanding of the climatic factors and processes that influence the 18o signal in the way through the atmosphere to the cave where carbonate precipitates acquiring its final isotopic composition this study presents for the first time in the iberia peninsula an integrated analysis of the isotopic composition of rainfall 18op during 2010 2012 years and through a detailed monitoring survey the transference of the primary isotopic signal throughout the soil and epikarst into the molinos cave teruel ne spain both air temperature and amount of precipitation have an important effect on 18op values clearly imprinting a seasonal variability modulated by an amount effect when rainfall events are more frequent or intense air mass history and atmospheric circulation influences are considered through the study of weather types synoptic scale climate patterns and large scale atmospheric circulation indexes north atlantic oscillation and western mediterranean oscillation revealing a dominant source effect on 18op values in this region where tropical north atlantic and western mediterranean are the two moisture source regions a delay of 2 3 months occurs between the dripwater oxygen isotopic composition 18od respect to 18op values as a consequence of large residence time in the epikarst limited calcite precipitates are found from winter to spring when 18od values are less negative and dripwater rates are constant this study suggests that ne iberian 18ocalcite proxy records are best interpreted as reflecting a combination of parameters not just paleotemperature or paleorainfall and if extending present day situation towards the recent past a biased signal towards winter values should be expected in molinos speleothem records

using stable isotope analysis δd δ18o to characterise the regional hydrology of the sierra de gador south east spain water stress is rapidly increasing in many mediterranean coastal zones mainly due to expansion in agriculture and tourism in this paper we focus on the sierra de gador campo de dalias aquifer system southeastern spain in order to assess the capability of water stable isotope analysis deltad delta 18 o to refine the understanding on recharge of this karstic aquifer system different types of surface and groundwater were sampled along an altitudinal gradient from the recharge zone in the mountains to the coastal plain surface water is restricted to local runoff collected in closed reservoirs runoff amounts collected in three of these reservoirs were monitored together with the precipitation in their catchments meteorological maps were used to detect the origin of the precipitation generating the majority of the runoff the results were compared to literature data on local and regional precipitation the use of oxygen and hydrogen isotopic composition has proved to be a useful tool to explain the origin of groundwater in a mediterranean karstic system such studies are however not numerous and are often limited to local scale recharge for fast reacting systems this paper focuses on the delta 18 o deltad relationships of local precipitation to explain the isotopic variability of a large karstic aquifer system the isotopic compositions of groundwater sampled along an altitudinal gradient from the recharge zone to the coastal plain are well displayed in a deltad delta 18 o diagram on a mixing line connecting a pole of mediterranean waters to a pole of atlantic waters the atlantic signature predominates in the shallow groundwater of natural springs reflecting the rainfall which produced the local runoff sampled the mediterranean signature is mainly restricted to deep groundwater from boreholes in the coastal plain the existence of a degree of spatial separation of groundwater types demonstrates that groundwater flow in a complex karstic system is not always continuous the mediterranean signature of deep groundwater could be due to past extreme rainfall events during which connectivity between recharge and reservoir exists while at the same time the atlantic signature of recent winter rains dominates in shallow groundwater the assumption that an equilibrium in isotopic composition is established within a continuous aquifer and that therefore a slope lower than 8 in a deltad delta 18 o diagram indicates evaporation is not necessarily valid c 2002 elsevier science b v all rights reserved

kinematic models of plate boundary deformation in southwest iceland derived from gps observations 1 we use data from gps campaign and continuous measurements from 1992 to 2004 in sw iceland to map the surface velocity field from the reykjanes peninsula to the eastern volcanic zone we divide the time series into preseismic july 1992 to june 2000 and postseismic june 2000 to may 2004 time intervals and we estimate gps station velocities for each interval as well as coseismic offsets due to the june 2000 earthquake sequence in the south iceland seismic zone sisz in addition to the plate spreading the preseismic velocity field shows the effects of inflation at hengill and hekla volcanoes whereas the postseismic velocities show deformation following the june 2000 earthquakes we consider several kinematic models to explain the preseismic velocities our preferred model includes several dislocations and point sources in an elastic half space with left lateral slip along the plate boundary on the reykjanes peninsula and below the sisz opening across the reykjanes peninsula and the western and eastern rift zones the optimal model has a locking depth of about 8 km in the central and eastern part of the reykjanes peninsula with a deep slip rate of about 17 mm yr and an opening of about 9 mm yr this locking depth is in agreement with the thickness of the seismogenic crust on the reykjanes peninsula which appears to vary between 7 and 9 km for the sisz we obtain a deep slip rate of about 19 mm yr below 16 km depth which is considerably deeper than the earthquake hypocenter depths in the area

some controls on flow and salinity in bering strait 1 during 1993 1994 steric forcing of flow through bering strait represented a northward sea level drop of 0 7 m from the bering sea basin to the adjacent deep arctic ocean of which 2 3 was due to the salinity difference between the basins seasonal variability of steric forcing appears small 0 05 m in contrast to large seasonal wind effects interannual changes in steric forcing may exceed 20 however and warm inflow from the north atlantic accumulation of freshwater in the southwest canada basin and temperature and salinity changes in the upper bering sea have all contributed to recent changes the mean salinity balance in bering strait is primarily maintained by large runoff to the bering shelf dilute coastal inflow from the gulf of alaska and on shelf movement of saline and nutrient rich oceanic waters from the bering sea basin in bering strait therefore both the throughflow and its salinity are affected by remote events

on steady state heat flow and the rheology of oceanic mantle 1 a constraint on the rheology of oceanic mantle is derived on the basis of a recently established scaling law for the onset of convection with temperature dependent viscosity our approach is free from the assumption of statistically steady state convection which has commonly been employed in previous studies the estimated range of asthenospheric viscosity is 1 4 1019 pa s if the activation energy is 300 kj mol 1 and 4 1019 1020 pa s if the activation energy is 100 kj mol 1 the former range is consistent with laboratory data as well as geodynamic inference based on the geoid the latter is consistent with geodynamic inference based on seamount loading history different activation energies predict different temperature contrasts in convecting mantle seismic tomography has the potential to discriminate between these possibilities

land uplift near vatnajokull iceland as observed by gps in 1992 1996 and 1999 summary war ming of the climate in the 20th century has been manifested by an ablation of europe s largest ice cap vatnajokull in iceland the thin elastic lithosphere and the low viscosity as thenosphere are responding to the reduction in mass by current land uplift in the vicinity of the ice cap suggested to be of the order of 5 10 mm yr 1 lithosphere thickness and asthenosphere viscosities compatible with these values have been inferred from our repeated gps epoch campaigns in 1992 1996 and 1999 uplift rates are estimated to be of the order of 5 19 mm yr 1 and the uplift rate is decreasing by 0 11 0 01 mm yr 1 km 1 with radial distance from the centre of the ice cap these results deviate from previous earth rheology models estimated for the region our data indicate that the lithosphere thickness might be of the order of 10 20 km and the asthenosphere viscosity may be as low as 5 10 17 pa s but these parameters need a careful fitting to the estimated uplift rates

isotopic composition δ18o and δd of precipitation and groundwater in a semi arid mountainous area guadiana menor basin southeast spain we characterize the precipitation and groundwater in a mountainous peaks slightly above 3000 m a s l semi arid river basin in se spain in terms of the isotopes 18o and 2h this basin with an extension of about 7000 km2 is an ideal site for such a study because fronts from the atlantic and the mediterranean converge here much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs a total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed to sample precipitation we set up a network of 39 stations at different altitudes 800 1700 m a s l with which we were able to collect the rain and snowfall from 29 separate events between july 2005 and april 2007 and take monthly samples during the periods of maximum recharge of the aquifers to characterize the groundwater we set up a control network of 43 points 23 springs and 20 wells to sample every 3 months the main aquifers and both the thermal and non thermal groundwater we also sampled two shallow water sites a reservoir and a river the isotope composition of the precipitation forms a local meteoric water line lmwl characterized by the equation d 7 72 18o 9 90 with mean values for 18o and d of 10 28 and 69 33 respectively and 12 9 for the d excess value to correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line wlmwl characterized by the equation d 7 40 18o 7 24 which takes into account the quantity of water precipitated during each event these values of d d d 18o 8 and d excess d 8 18o 10 in each curve bear witness to the amount effect an effect which is more manifest between may and september when the ground temperature is higher other effects noted in the basin were those of altitude and the continental influence the isotopic compositions of the groundwater are represented by the equation d 4 79 18o 18 64 the groundwater is richer in heavy isotopes than the rainfall with mean values of 8 48 for 18o and 59 27 for d the isotope enrichment processes detected include a higher rate of evaporation from detrital aquifers than from carbonate ones the effects of recharging aquifers from irrigation return flow and or from reservoirs leakage and enrichment in 18o from thermal water copyright 2010 john wiley sons ltd

effects of climate variations on pelagic ocean habitats and their role in structuring forage fish distributions in the bering sea abstract this paper examines how climate variations influence the boundaries of suitable ocean habitat and how these changes affect the spatial distribution and interactions between forage fishes in the southeastern bering sea shelf the study focuses on the summer distributions of forage fish age 0 and age 1 walleye pollock theragra chalcogramma and capelin mallotus villosus observed during national marine fisheries service summer acoustic trawl surface trawl and bottom trawl surveys conducted in the bering sea between 2004 and 2009 we compare the responses of these forage fish to climate induced shifts in ocean habitats habitat boundaries were defined using key explanatory variables including depth bottom temperature and surface temperature using general additive models bathymetry bottom temperature and frontal zones formed boundaries between different groups of forage fishes age 0 pollock were dispersed throughout the middle domain 50 100 m depth in well stratified regions in cold years the highest densities of age 0s were found in the southern regions of the middle domain waters in waters warmer than approximately 1 c in contrast age 1 pollock were observed on the sea floor over the middle domain and in midwater in the northern outer domain in cold years and more broadly dispersed across the middle and outer domain in warm years the demersal concentrations of age 1 pollock in the middle domain shows age 1 pollock tolerate a wide range of bottom temperatures midwater and demersal distributions of age 1 pollock exhibited a patchier distribution than age 0 pollock midwater concentrations of age 1 pollock tended to be associated with the outer domain and regions where higher levels of lower trophic level production are expected capelin were concentrated in the inner domain a well mixed region the overlap of age 1 pollock and capelin was higher in cold years than in warm years

processes affecting groundwater quality in arid zones the case of the bou areg coastal aquifer north morocco abstract the coastal aquifer of bou areg morocco has been studied to identify the main processes causing groundwater salinization using a multi tracer general chemistry and isotopes 2h 18o 13c 15nno3 18ono3 geochemical approach groundwater is characterized by the widespread occurrence of brackish waters tds no 3 reaching a maximum of 208 mg l 1 and cl lagoon samples represent a mixture of fresh water and sea water showing a na cl ratio in agreement with that of sea water and an excess of ca the high ca values represent the main peculiarity of the groundwater lagoon water system two types of groundwater could be identified i freshwater separated from the whole system and located at the limit of the irrigated area characterized by low tds depleted isotopic composition and relatively high quality and ii water mainly recharged by mountain runoff interacting with local recharge and acquiring salinity from different sources thus creating a complex system of dilute waters hydrochemical results confirm that the high salinity of the aquifer is caused by the coexistence of dissolution of evaporate rocks and carbonates from miocene strata water rock interaction and human impacts due to agricultural return flows the latter represents the main contribution to groundwater salinization especially in the central part of the aquifer as well as one of the main causes of the general increase in no 3 concentrations only locally in the southern part of the aquifer close to the city of kariat arkmane the high salinization observed may be attributed to the presence of lagoon water intrusion the isotopic composition of dissolved no 3 indicates manure and septic effluents especially in urban areas and in the central part of the plain and synthetic fertilizers in the agricultural zone as the main drivers for human induced pollution the study shows that agricultural return flow has significantly modified the chemistry of the system and it is a prime example of the human induced changes over coastal environments saline water intrusion from the lagoon in the shallow aquifer is negligible while discharge of polluted groundwater into the lagoon has been found to partially alter its quality

clustering oxbow lakes in the upper tisza region on the basis of stable isotope measurements summary several times a year the river tisza floods areas between dikes fills the oxbow lakes on the floodplain and changes their water however the water addition in the oxbow lakes does not only take place through flooding it is also likely that water can seep under the surface through the gravelled layers of the old river beds and furthermore precipitation also plays a role our goal with this study is to acquire a full comprehensive picture of the water addition of the oxbow lakes in the upper tisza region surface and groundwater samples were taken from the river tisza the oxbow lakes and the boreholes around four oxbow lakes and stabile isotope ratios were measured we can get information on the origin the evaporation and the state of the waters and the depth of the water table with the help of 18 o vsmow and d vsmow during the examination the question we addressed was how oxbow lakes can be classified according to their water addition on the basis of their stable isotope ratios the results from the tisza and the oxbow lakes as well as the results from the oxbow lakes on the reclaimed side and the floodplain are also isolated

coupled wind forced controls of the bering chukchi shelf circulation and the bering strait throughflow ekman transport continental shelf waves and variations of the pacific arctic sea surface height gradient abstract we develop a conceptual model of the closely co dependent bering shelf bering strait and chukchi shelf circulation fields by evaluating the effects of wind stress over the north pacific and western arctic using atmospheric reanalyses current meter observations satellite based sea surface height ssh measurements hydrographic profiles and numerical model integrations this conceptual model suggests bering strait transport anomalies are primarily set by the longitudinal location of the aleutian low which drives oppositely signed anomalies at synoptic and annual time scales synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along strait meridional pressure gradient in particular we show that storms centered over the bering sea excite continental shelf waves on the eastern bering shelf that carry northward velocity anomalies northward through bering strait and along the chukchi coast the integrated effect of these storms tends to decrease the northward bering strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the aleutian basin and the western subarctic gyre ekman suction then increases the water column density through isopycnal uplift thereby decreasing the dynamic height sea surface height and along strait pressure gradient storms displaced eastward over the gulf of alaska generate an opposite set of bering shelf and aleutian basin responses while ekman pumping controls canada basin dynamic heights proshutinsky et al 2002 we do not find evidence for a strong relation between beaufort gyre sea surface height variations and the annually averaged bering strait throughflow over the western chukchi and east siberian seas easterly winds promote coastal divergence which also increases the along strait pressure head as well as generates shelf waves that impinge upon bering strait from the northwest

a relationship between heat transfer to sea ice and temperature salinity properties of arctic ocean waters it is demonstrated that the characteristic temperature salinity relationship shown by thermocline waters of the arctic ocean can be reproduced using a simple model based on transfer of heat directly from these waters to sea ice from this we deduce that there is direct sensible heat flux from waters of atlantic origin to the ice cover such interaction could play a major role in determining the physical properties of arctic water masses

climate footprint in karst aquifers derived from time series and spatial data the case of orce maria se spain the alignment of carbonates comprising the orce and maria mountain chains rides the surface hydrological divide between the catchment basins of the guadalquivir river and the segura river they are influenced by atlantic precipitation on the western side and mediterranean on the eastern side these circumstances cause differences in the precipitation recharge which are reflected in the groundwater and they can be studied in the recharge response recorded not only in piezometers but also in springs the hydrochemical and isotopic characteristics of the groundwater can also be conditioned by these different climate environments an analysis of piezometric and hydrometric series and of hydrochemical and isotopic data shows that the precipitation recharge with mediterranean influence is predominant despite the fact that only 30 of the outcrops are in that catchment basin in the main discharge zones are springs in carbonate outcrops and in outcrops associated with pliocene and quaternary material the data reveal a mixing of waters on the borders of the mountain chains deriving from the carbonate aquifer and from the pliocene and quaternary detrital sediments overlying the aquifers on its borders there are differences between the chemical compositions of the water circulating through the maria mountain and through orce mountain carbonates interpreted as the result of a greater or lesser presence of dolomites the isotopic data can be used to identify water infiltrating from mediterranean or atlantic areas of influence the values of 18o are between 9 38 and 6 46 and in the case of 2h between 61 73 and 44 46 in the maria mountains mediterranean influence the average is of 8 75 and 53 63 respectively and of 9 01 and 59 41 in samples related to the carbonates of the orce mountains atlantic influence the mean for the deuterium excess is of 15 8 in the first case and 13 4 in the second one

the north pacific a global scale estuary abstract the atmospheric net flow of water from the atlantic to the pacific ocean is supposed to maintain the salinity difference between the two oceans assuming the existence of a subsurface level of no horizontal pressure gradient in the ocean the mean sea level in the northern pacific must be higher than in the arctic ocean this mean sea level difference is supposed to drive the observed mean flow through the bering strait the estimated flow of freshwater through the bering strait is approximately equal to the estimated atmospheric net flow of water from the north atlantic to the north pacific this justifies the formulation of a simple estuary model for the north pacific in which the brackish water exits through the bering strait the salinity difference between the two oceans is shown to be controlled by the topography of the bering strait the estuary model gives residence times for water in the upper layer 1000 m thick of approximately 1000 years and in the lower layer of approximately 400

measuring postglacial rebound with gps and absolute gravity we compare vertical rates of deformation derived from continuous global positioning system gps observations and episodic measurements of absolute gravity we concentrate on 4 sites in a region of north america experiencing postglacial rebound the rates of uplift from gravity and gps agree within one standard deviation for all sites the gps vertical deformation rates are significantly more precise than the gravity rates primarily because of the denser temporal spacing provided by continuous gps tracking we conclude that continuous gps observations are more cost efficient and provide more precise estimates of vertical deformation rates than campaign style gravity observations where systematic errors are difficult to quantify

circulation and water mass transformation in a model of the chukchi sea 1 the circulation and water mass transformation in a regional ocean ice model of the chukchi sea are discussed the model has horizontal resolution of o 4 km is forced by fluxes derived from daily ncep reanalysis fields and has seasonally varying transport temperature and salinity imposed at bering strait many of the observed characteristics of the mean circulation and seasonal cycle in the chukchi sea are reproduced the discussion focuses on the branching of the inflow transport into pathways following herald canyon central channel and the alaskan coast the pattern of ice melt and the water mass transformation and formation of winter water and hypersaline water the ice melt pattern and timing is strongly influenced by advection through bering strait high frequency forcing results in a larger region of ice melt particularly over the shoals and in the northern chukchi sea compared to monthly mean forcing in the model the seasonal cycle of salinity in the southern and central chukchi sea is dominated by advection through bering strait while local atmospheric forcing and brine rejection are more important north of herald and hanna shoals and in barrow canyon however since the residence time in the chukchi sea is generally less than 1 year interannual variability in the bering strait salinity will be reflected in the salinity across the chukchi sea and at barrow canyon

satellite and hydrographic observations of the bering sea green belt abstract green belt is the aptly named region of high productivity occurring principally along and above the shelf slope boundary in the bering sea topex altimeter measurements of sea surface topography seawifs imagery of chlorophyll a concentration and shipboard measurements of salinity and fluorescence are used to describe the surface structure of the green belt and its relationship to the bering slope current eddy field during the 2000 2001 and 2002 spring blooms during spring 2000 high surface chlorophyll a concentrations 10 mg m 3 were observed within a 200 km wide band adjacent to and seaward of the shelf break in the northwest bering sea this high concentration chlorophyll band was associated with an anticyclonic eddy group that propagated along isobaths above the continental slope and entrained chlorophyll from the shelf slope front during spring 2001 anticyclonic eddies in the northwest bering sea had propagated off slope prior to the onset of the spring bloom and were too far from the shelf slope front to entrain frontal chlorophyll during the bloom a second chlorophyll front associated with the leading edge of the off slope eddies was observed between these two fronts was a region of relatively low chlorophyll a concentration 1 mg m 3 the eddy field during the 2002 spring bloom was observed to propagate northwestward adjacent to the shelf break and entrain chlorophyll from the shelf slope region in a manner similar to what was observed during the 2000 spring bloom these observations suggest that eddies are important if not the principal agents that cause variability in the distribution of chlorophyll during the spring bloom in the central bering sea

bering sea cyclonic and anticyclonic eddies observed during summer 2000 and 2001 abstract using satellite altimeter and ship data bering sea cyclonic and anticyclonic eddies were observed in summer 2000 and 2001 to examine their biological chemical and physical structures results from the ship transect revealed the interactions between the physical and biological conditions of bering sea eddies at the center of a cyclonic anticlockwise eddy upwelling was transporting nutrient no3 no2 rich water 25 m to the surface which resulted in relatively high chlorophyll a concentrations 1 0 mg m 3 developing under the pycnocline in contrast in the center of an anticyclonic clockwise eddy there was downwelling this downwelling of surface warm water was destroying a cold layer at about 150 m depth caused by winter convection however around the periphery of the anticyclonic eddy the isopycnals were tilted up and nutrient rich water was being transported along with them up into the euphotic zone so that high chlorophyll a concentrations were being developed above the pycnocline inside the anticyclonic eddy

comparison of warm and cold years on the southeastern bering sea shelf and some implications for the ecosystem the southeastern middle shelf of the bering sea has exhibited extreme variability in sea ice extent temperature and the distribution and abundance of species at multiple trophic levels over the past four decades from 1972 2000 there was high interannual variability of areal extent of sea ice during spring march april in 2000 this shifted to a 5 year 2001 2005 period of low ice extent during spring which transitioned to a 4 year 2007 2010 period of extensive sea ice high low areal extent of sea ice in spring was associated with cold warm water column temperatures for the following 6 7 months the ocean currents also differed between warm and cold years during cold years the monthly mean currents over the shelf were largely westward while in warm years the direction of currents was more variable with northward flow during december february and relatively weak flow during the remainder of the year the types and abundance of zooplankton differed sharply between warm and cold years this was especially true during the prolonged warm period 2001 2005 and cold period 2007 2010 and was less evident during the years of high interannual variability during the warm period there was a lack of large copepods and euphausiids over the shelf however their populations rebounded during cold period small crustacean zooplankton taxa did not appear to vary between and warm and cold years for both walleye pollock and pacific cod year class strength recruitment was low during the prolonged warm period but improved during the following cold period year class strength did not appear to vary as a function of warm and cold years during the period of high year to year variability also recruitment of arrowtooth flounder a predator of pollock and cod did not appear influenced by the warm or cold years finally the distribution and relative abundance of fin whales appeared to differ in warm and cold years with fewer whales on the southeastern middle shelf during warm years

shifts in the physical environment in the pacific arctic and implications for ecological timing and conditions abstract the northern bering sea and chukchi sea represent the gateway from the pacific to the arctic this contiguous marine system encompasses one of the largest continental shelves in the world and serves as the sole point of connection between the north pacific and arctic ocean this region has unique attributes and complex dynamics driven by the convergence of distinct water masses dynamic currents advection between pacific and arctic systems and important latitudinal gradients relevant to stratification and water mass structure water temperature and seasonal ice cover many processes and interactions in the region appear to be changing with important implications for both hydrography and ecology our analyses access remote and local data sources in us and russian waters to characterize oceanographic conditions and analyze the implications of dramatic shifts in recent years previously this region appeared resistant to trends apparent elsewhere in the greater arctic now the pacific arctic also appears to be in rapid transition the conditions observed in 2017 2019 are unprecedented we note important shifts in the phenology and magnitude of physical variables including sea ice extent concentration and duration as well as extreme reduction in the extent and intensity of the related bering sea cold pool we also note distinct regional dynamics in sea surface temperature in the bering chukchi system distinguishing western eastern and northern areas of the bering sea specifically our analyses distinguish the northern bering sea as an important transition zone between the pacific and arctic with higher frequency variability in sea surface temperature anomalies our results suggest that the strength and position of the aleutian low may be linked to warm and cold phases in the bering sea and has an important role in large scale circulation while cold winds out of the north are necessary to form ice in the northern bering sea strong winds may be associated with weak sea ice as wind action may break ice and enhance vertical mixing counteracting enhanced sea ice production from the advection of cold air research in this important region is complicated by international borders but may be enhanced through international collaboration this analysis represents an attempt to integrate data across russian and us waters to more fully represent system wide processes to contrast regional trends and to better understand physical interactions

glacial isostatic adjustment and the radial viscosity profile from inverse modeling 1 a formal inverse procedure is used to infer radial mantle viscosity profiles from several observations related to the glacial isostatic adjustment process the data sets consist of late pleistocene and holocene sea level data from scandinavia the barents sea central europe canada and the far field as well as observations of changes in the earth s rotation and gravitational field and present day uplift and gravity changes in scandinavia inferences of mantle viscosity are robust against assumptions such as the a priori viscosity model and model discretization however the quality of ice sheet reconstruction remains crucial for the inverse inference the importance to discuss regional mantle viscosity models in view of the lateral variability in mantle properties has been evident our inference suggests a two order of magnitude increase of mantle viscosity with depth and volume averaged upper and lower mantle viscosities around 7 1020 and 2 1022 pa s respectively mantle viscosity does not need to increase sharply across the 660 km seismic discontinuity the viscosity profiles suggested are also able to reconcile the large scale geoid anomaly related to mantle convection

electrical resistivity tomography ert applied to karst carbonate aquifers case study from amdoun northwestern tunisia the amdoun region is characterized by a high degree of karstification due to the climate impact 1500 mm year 1 and the development of fracture network survey using electrical resistivity tomography ert is deployed to provide a cost effective characterization of the subsurface karst environments a total of seven ert profiles with lengths of 315 m were evaluated at the beja governorate nw tunisia the area represents a small syncline of boudabbous limestone rocks lower eocene which is covered by a thin layer of clay in this study an ert survey was conducted to examine the spatial distribution and shape of underground cavities in the karst area in jebel sabah anticline and ain sallem zahret medien syncline in this study geological hydro geological and electrical resistivity tomography ert methods were applied to determine the geometry of the perched aquifer in the amdoun region nw tunisia the area is characterized by fractured and karstic limestone aquifer of late cretaceous abiod fm and lower eocene boudabbous fm the aquifers have a karstic functioning and drain aquifers of economical interest despite some wells exploiting them seven resistivity profiles were conducted along the survey area at three sites the orientation extension and the degree of inclination of those profiles are shown in the location map the correct resistivity data were interpreted using earth imager 2d software the results of the interpreted geo electrical sections showed that the resistivity of the carbonate aquifer varied between 2 5 to over 5794 m the thickness of the perched aquifer ranged from 15 to 50 m while its depth from the surface lies between 10 and 60 m the ert not only provided precise near surface information but was also very useful for establishing the 3d geometry and the position of several potential cavities and karts the results show the presence of small to large isolated cavities at various depths the low resistivity of cavities in the boudabbous formation has been explained by the groundwater saturation the ert technique could be effectively used for 3d detection of underground limestone cavities

spatial distribution of rock fragments in dolines a case study in a semiarid mediterranean mountain range sierra de gador se spain abstract rock fragments rfs at the soil surface have great effects on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments rf in the dolines which may be of importance in understanding overland flow and subsequent recharge in limestone karst landscapes this study analysed spatial variability of rf cover and size in different topographic positions top upper middle and lower position in three dolines in sierra de gador almeria province south east spain the results indicated that cover percentage of small rfs 5 20 mm increased but large rf cover 250 600 mm and 600 mm decreased from the upper position to the lower position of the dolines small rfs were usually resting on the soil surface while most large rfs tended to be partly embedded in the soil surface total rf cover and d 50 median diameter of the surface rfs greater than 5 mm tended to increase with slope gradient

current plate movements across the mid atlantic ridge determined from 5 years of continuous gps measurements in iceland 1 we analyze data spanning up to 5 years from 18 continuous gps stations in iceland computing daily positions of the stations with three different high level geodetic processing software packages we observe large scale crustal deformation due to plate spreading across iceland the observed plate divergence between the north american and the eurasian plates is in general agreement with existing models of plate motion spreading is taken up within a 100 150 km wide plate boundary zone that runs through the island of the two parallel branches of the plate boundary in south iceland the eastern volcanic zone is currently taking up the majority of the spreading and little is left for the western volcanic zone the plate boundary deformation field has been locally and temporarily affected in south iceland by two mw 6 5 earthquakes in june 2000 inflation at katla volcano during 2000 to 2004 and an eruption of hekla volcano in february 2000 all stations with significant vertical velocities are moving up relative to the reference station reyk with the highest velocity exceeding 20 mm yr in the center of the island

origin and type of rainfall for recharge of a karstic aquifer in the western mediterranean a case study from the sierra de gador campo de dalias southeast spain isotope signatures in precipitation from the global network for isotopes in precipitation around the mediterranean basin and literature data are compared with isotopic data from a large karstic aquifer in southeast spain to explain the origin and type of the precipitation events dominating recharge analysis of the deuterium excess d at the scale of the mediterranean basin and at the regional scale allows us to understand the isotopic context of the study area campo de dalias and the sierra de gador almerfa province the origin of precipitation can be determined from its d value the d value changes as a function of the initial evaporation condition it depends on the relative humidity and temperature during the evaporation producing the water vapour of the clouds the water vapour which dominates the study area is generated in two areas the atlantic ocean d 10 parts per thousand and the western mediterranean basin d 15 parts per thousand with increasing precipitation volume the western mediterranean character dominates these heavier storms contribute mainly to recharge as illustrated by the d value of 13 6 parts per thousand in deep groundwater of the campo de dalias weighted d values increase with the volume of precipitation giving a significant relationship for the southern and eastern coasts of the iberian peninsula this selectivity of d to monthly precipitation was used to estimate the return period of precipitation leading to aquifer recharge at 0 9 4 9 years moderate rainfall which occurs more frequently still represents similar to 60 90 of the total precipitation one of the challenges to meet ever growing water demands is to increase recharge from moderate events yielding intermediate quantities per event but forming the bulk of the annual precipitation copyright c 2006 john wiley sons ltd

post glacial rebound and asthenosphere viscosity in iceland during the weichselian glaciation iceland was covered with an ice cap which caused downward flexure of the earth s surface the post glacial rebound in iceland was very rapid being completed in about 1 000 years the length of this time interval constrains the maximum value of asthenosphere viscosity in iceland to be 1 times 10 sup 19 pa s or less further clarification of the ice retreat and uplift history may reveal lower viscosity current changes in the mass balance of icelandic glaciers must lead to measurable elevation changes considering this low viscosity expected current elevation changes around the vatnajoekull ice cap are of the order of 1 cm per year due to mass balance change in this century

swash aquifer interaction in the vicinity of the water table exit point on a sandy beach the coupling of sandy beach aquifers with the swash zone in the vicinity of the water table exit point is investigated through simultaneous measurements of the instantaneous shoreline swash front location pore pressures and the water table exit point the field observations reveal new insights into swash aquifer coupling not previously gleaned from measurements of pore pressure only in particular for the case where the exit point is seaward of the observation point the pore pressure response is correlated with the distance between the exit point and the shoreline in that when the distance is large the rate of pressure drop is fast and when the distance is small the rate decreases the observations expose limitations in a simple model describing exit point dynamics which is based only on the force balance on a particle of water at the sand surface and neglects subsurface pressures a new modified form of the model is shown to significantly improve the model data comparison through a parameterization of the effects of capillarity into the aquifer storage coefficient the model enables sufficiently accurate predictions of the exit point to determine when the swash uprush propagates over a saturated or a partially saturated sand surface potentially an important factor in the morphological evolution of the beach face observations of the shoreward propagation of the swash induced pore pressure waves ahead of the runup limit shows that the magnitude of the pressure fluctuation decays exponentially and that there is a linear increase in time lags behavior similar to that of tidally induced water table waves the location of the exit point and the intermittency of wave runup events is also shown to be significant in terms of the shore normal energy distribution seaward of the mean exit point location peak energies are small because of the saturated sand surface within the seepage face acting as a rigid lid and limiting pressure fluctuations landward of the mean exit point the peak energies grow before decreasing landward of the maximum shoreline position

modeling of storm surges in the bering sea and norton sound sea level currents and ice distribution are studied in the bering sea during storm events the ice and ice edge are incorporated into storm surge model the interaction of wind ice and water is expressed by the normal and tangential stresses a numerical grid is established for the bering sea and a second refined grid is constructed for norton sound construction of open boundary conditions for the water and ice motion and numerical questions related to the application of a large frictional coefficient for ice are also discussed storm events from february and march 1982 are analyzed and compared with observations of bottom pressure and ice motion made by noaa pacific marine environmental laboratory in the bering sea and sea level observations at stebbins alaska the influence of the ice on the storm surge propagaton is shown particularly that of the fast ice in norton sound the model reproduces several observed features of the ice distribution in the bering sea including the race track region off nome the polynya south of saint lawrence island and the movement of the ice edge

circulation on the central bering sea shelf july 2008 to july 2010 1 we examine the july 2008 to july 2010 circulation over the central bering sea shelf using measurements at eight instrumented moorings hindcast winds and numerical model results at sub tidal time scales the vertically integrated equations of motion show that the cross shelf balance is primarily geostrophic the along shelf balance is also mainly geostrophic but local accelerations wind stress and bottom friction account for 10 40 of the momentum balance depending on season and water depth the shelf exhibits highly variable flow with small water column average vector mean speeds 5 cm s 1 mean peak speeds in summer 3 6 cm s 1 10 30 cm s 1 are smaller than in winter and fall 6 12 cm s 1 30 70 cm s 1 low frequency flows 1 4 cpd are horizontally coherent over distances exceeding 200 km vertical coherence varies seasonally degrading with the onset of summer stratification because effects of heating and freezing are enhanced in shallow waters warm summers increase the cross shelf density gradient and thus enhance northward transport cold winters with increased ice production and brine rejection increase the now reversed cross shelf density gradient and enhance southward transport although the baroclinic velocity is large enough to influence seasonal transports wind forced ekman dynamics are primarily responsible for flow variations the system changes from strong northward flow with coastal convergence to strong southward flow with coastal divergence for northerly and easterly winds respectively under northerly and northwesterly winds nutrient rich waters flow toward the central shelf from the north and northwest replacing dilute coastal waters that are carried south and west

low frequency current regimes over the bering sea shelf abstract using direct current measurements made during the period 1975 81 we describe the general circulation over the southeastern bering sea and differentiate it by regimes related to depth and forcing mechanisms three regimes are present delineated by water depth z the coastal z 50 m the middle shelf 50 z 100 m and the outer shelf z 100 m these are nearly coincident with previously described hydrographic domains statistically significant mean flow 1 to 10 cm s 1 exists over the outer shelf generally directed toward the northwest but with a cross isobath component flow of similar magnitude 1 6 cm s 1 occurs in the coastal regime paralleling the 50 m isobath in a counterclockwise sense around the shelf mean flow in the middle shelf is insignificant kinetic energy at frequencies 0 5 cycle per day cpd is greater over the outer shelf than in the other two regimes suggesting that oceanic forcing is important there but does not affect the remainder of the shelf kinetic

contribution of environmental isotopes to the understanding of complex hydrologic systems a case study sierra de gador se spain determining the content of 18o and deuterium in the groundwater at the southern edge of the sierra de gador between october 1991 and march 1993 has enabled identification of the flow system of the waters the recharge and mixing processes and the possible mechanisms of salinization analysis of the precipitation indicates the dominant source and direction of the air masses the local meteoric water line that is established indicates a primarily mediterranean origin for the precipitation recharging the aquifers the variation of 18o content with altitude 0 35 per mille per 100 m enables an estimation of the principal recharge area which corresponds to a zone between 1200 and 1800 m a s l 1997 john wiley sons ltd

multi scale modeling of the north pacific ocean assessment and analysis of simulated basin scale variability 1996 2003 1 a primitive equation ocean general circulation model is used to investigate climate impacts in the north pacific ocean in the 1996 to 2003 period the objective is to assess the model ability to reproduce observed modes of variability and study their impact in the northeast pacific this work is done within the framework of the u s global ecosystem globec northeast pacific program studying the links between climate variability and ecosystem dynamics three large scale events are considered the 1997 1998 el nino the 1999 regime shift and the 2002 cold fresh subsurface anomalous water mass that was observed in the gulf of alaska and off the coast of oregon the circulation model is shown to generate the correct seasonal to interannual large scale variability and is able to represent the climatic signals of interest in the eastern pacific we show that the influence of the 1997 1998 el nino reached the coastal gulf of alaska and induced an increase in the upper ocean heat content along the coast of north america an analysis of the sea surface temperature for the model years shows agreement between model and data in the representation of the 1999 shift to a cold phase in the eastern and northern north pacific finally using the model results we speculate that the origin of the 2002 cold fresh anomaly in the northeast pacific was due to enhanced mixing during the preceding winter in the center of the alaska gyre owing to anomalous changes in the density structure of the upper ocean this water was able to move geostrophically toward the coast and it persisted in the northeast pacific below the mixed layer the following year

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

altimeter observations of the bering slope current eddy field topex altimeter data is analyzed to describe the mesoscale eddy field associated with the bering slope current in the central bering sea the observed eddy field is well defined seasonally modulated and interannually variable the most energetic mesoscale eddy activity typically occurs during the spring and summer months and is characterized by a peak along isobath wavelength of 212 km and a representative wave period of 4 months spatial variability of annual period phase indicates that the axis of bering slope current exhibits seasonal offshore migration

stable isotope evidences on sources and mechanisms of groundwater recharge in hohhot basin china it is extremely important for water resources management to understand the mechanisms of recharge to aquifer monitoring changes in stable isotopes 2h and 18o can be used to learn some information on groundwater recharge processes in this study the stable isotopes from precipitation and groundwater samples were employed to trace the recharge processes in hohhot area inner mongolia the recharge of shallow groundwater is mainly due to precipitation from the eastern mountain area in eastern and southeastern parts and from the northern mountain area in the northern and southwestern parts the recharge mechanisms for shallow groundwater are the infiltration of surface water in the piedmont area and lateral flow recharge the source of deep groundwater in confined aquifer is probably from precipitation in high altitude area or cold weather conditions which perhaps have the same recharge source as shallow groundwater in the northern and southwestern parts compared with the previous data from shao s geotech investig surv 4 41 43 1989 study the variation of groundwater recharge for nearly 30 years in the study area was inferred the recharge zone is the eastern and northern mountain areas the recharge way to shallow groundwater has changed into lateral recharge from surface runoff in the mountain area and from surface runoff and vertical rainfall infiltration in the piedmont area but the recharge mechanism for deep groundwater has a similar origin with the one for northern shallow groundwater namely the lateral recharge

glacial isostatic adjustment and the viscosity structure underlying the vatnajokull ice cap iceland we examine the dependence of glacial isostatic adjustment gia due to changes in the vatnajokull ice cap iceland on the underlying viscosity structure iceland offers a unique case study for gia research with a thinner elastic lithosphere underlain by a low viscosity zone or asthenosphere as opposed to regions such as fennoscandia or north america described by a thicker lithosphere while not necessarily featuring an asthenosphere

pathways of pacific water across the chukchi sea a numerical model study 1 pathways of pacific water flowing from the north pacific ocean through bering strait and across the chukchi sea are investigated using a two dimensional barotropic model in the no wind case the flow is driven only by a prescribed steady northward flow of 0 8 sv through bering strait the resulting steady state circulation consists of a broad northeasterly flow basically following the topography with a few areas of intensified currents about half of the inflow travels northwest through hope valley while the other half turns somewhat toward the northeast along the alaskan coast the flow through hope valley is intensified as it passes through herald canyon but much of this flow escapes the canyon to move eastward joining the flow in the broad valley between herald and hanna shoals another area of slightly intensified currents there is a confluence of nearly all of the flow along the alaskan coast west of pt barrow to create a very strong and narrow coastal jet that follows the shelf topography eastward onto the beaufort shelf thus in this no wind case nearly all of the pacific water entering the chukchi sea eventually ends up flowing eastward along the narrow beaufort shelf with no discernable flow across the shelf edge toward the interior canada basin travel times for water parcels to move from bering strait to pt barrow vary tremendously according to the path taken e g less than 6 months along the alaskan coast but about 30 months along the westernmost path through herald canyon this flow field is relatively insensitive to idealized wind forcing when the winds are from the south west or north in which cases the shelf transports tend to be intensified however strong northeasterly to easterly winds are able to completely reverse the flows along the beaufort shelf and the alaskan coast and force most of the throughflow in a more northerly direction across the chukchi sea shelf edge potentially supplying the surface waters of the interior canada basin with pacific water the entire shelf circulation reacts promptly to changing wind conditions with a response time of 2 3 days the intense coastal jet between icy cape and pt barrow implies that dense water formed here from winter coastal polynyas may be quickly swept away along the coast in contrast there is a relatively quiet nearshore region to the west between cape lisburne and icy cape where dense water may accumulate much longer and continue to become denser before it is carried across the shelf

chemical and isotopic δ18o δ2h δ13c 222rn multi tracing for groundwater conceptual model of carbonate aquifer gran sasso infn underground laboratory central italy summary a hydrochemical and isotope study was conducted on the drainage waters of an underground laboratory located inside the gran sasso massif central italy the study was expected to improve the conceptual model of groundwater circulation at the base of an over 1000 thick unsaturated zone in the gran sasso partitioned karst aquifer this lithostratigraphically and tectonically complex aquifer is typical of africa europe thrust and fold collision belt in the mediterranean area in this case investigations on water rock interactions during recharge in complex aquifers overlaid by a thick unsaturated zone have been made thanks to the strategic location of the gran sasso underground laboratories located in the core of a huge carbonate aquifer knowledge of the local basic hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study which was carried out at the aquifer scale and at the fine scale in the underground laboratories the water rock interaction processes were investigated both spatially and in temporal sequences analysing recharge waters and groundwater in the underground laboratories by multitracing techniques including major ions and 18o 2h and 13c stable isotopes use of 222rn provides information on transit time in the aquifer processes proved to be typical of carbonate rocks with clear influence of vertical movement of water on chemical physical parameters through the unsaturated zone conversely in the saturated zone these processes proved to be dominantly affected by local geological structural conditions a conceptual model with dual flow velocity is proposed directly related to the local geological structural setting 222rn decay enables to calculate an effective velocity of around 10 m day for the fracture network through the sequence of less permeable dolomites and underlying limestone lag time between recharge and chemical changes in the saturated zone testifies to an effective velocity of about 35 m day for fast flow through recent and active extensional faults

effects of a shelf polynya on flow and water properties in the northern bering sea we present long term 230 day measurements from three moorings in the vicinity of saint lawrence island on the northern bering sea shelf one mooring was deployed near the polynya which often exists south of the island these data confirm the existence of strong 0 15 m s 1 flow toward bering strait northwest of the island in anadyr strait and suggest that regional circulation results in a moderate 0 03 5 m s 1 mean flow eastward along the southern coast of saint lawrence island coherent variations in the regional circulation and variations in the geostrophic wind account for much of the low frequency current fluctuation south of saint lawrence island however there were 11 events when offshore northerly winds coincided with the temperature following the freezing point increasing salinity and reversal of the current this suggests that ice formation and the ensuing brine rejection affect flow in the vicinity of the polynya scaling of a simplified momentum equation indicates that the cross shelf density gradient was a possible mechanism for some of the reversals salinity data show a seasonal cycle as well as individual events of brine rejection during an average event time of 65 hours the salinity increased by 8 10 3 g kg 1 h 1 the heat flux can be estimated as 535 wm 2 these fluxes correspond to an ice production of 5 m during winter 1981 extrapolation of our results and comparison with the freshwater cycle suggest that brine rejection is an important component of the regional salt budget

characteristics and variability of the inner front of the southeastern bering sea the inner front of the southeastern bering sea shows marked spatial variability in frontal characteristics created by regional differences in forcing mechanisms differences in forcing mechanisms sea ice advance retreat and storm strength and timing and early spring water properties result in strong interannual variability in biological chemical and physical features near the front we have developed a simple model based on surface heat flux and water column mixing to explain the existence of cold belts cont shelf res 19 14 1999 1833 associated with such fronts hydrography fluorescence and nutrient observations show that pumping of nutrients into the euphotic zone occurs and this can prolong primary production at the inner front the effectiveness of this process depends on two factors the existence of a reservoir of nutrients in the lower layer on the middle shelf and the occurrence of sufficient wind and tidal energy to mix the water column

seasonal and interannual variability of the bering slope current abstract time series of sea surface height anomalies derived from satellite altimeters and absolute dynamic topography are used to examine variability in the geostrophic surface currents in the eastern bering sea the data suggest that the primary source of water to the eastern boundary currents of the bering sea is flow from the north pacific through amukta pass an aleutian pass located at 172 w the aleutian north slope current ansc is strongest and most variable in the winter months upon turning the corner to feed the bering slope current bsc the ansc bifurcates resulting in a westward flow at 54 n in addition to the northwestward flowing bsc this westward countercurrent has not been previously observed in the winter the bsc flows strongly to the northwest and is located near the shelf break during the rest of the year the mean flow is broadly northwestward but weaker and farther from the shelf break a continuous northwestward flowing current is rarely observed in the altimetry data except during winter months as it is overwhelmed by mesoscale variability the strength of the bsc in winter is correlated with the multivariate enso index and the north pacific index on interannual timescales

controls of infiltration runoff processes in mediterranean karst rangelands in se spain semiarid karst landscapes represent an important ecosystem surrounding the mediterranean basin for which little is known on runoff generation knowledge of the sources and patterns of variation in infiltration runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems the objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area sierra de gador se spain at micro plots and to investigate the integrated response of rainfall on a typical hillslope rainfall simulations in micro plots and natural rainfall runoff monitoring on a hillslope were carried out complementarily we investigated the role of soil surface components vegetation rock outcrop fracture and soil crust topographic position antecedent soil moisture and rainfall characteristics in regulating infiltration runoff processes results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape while bare patches and rock outcrops acted as sources for runoff all plots with 50 vegetation cover had no runoff with up to 55mmh 1 of simulated rain in contrast nearly all bare plots had runoff under the same simulated rain with runoff coefficients ranging from 3 1 to 20 6 on dry soil surface conditions and from 2 0 to 65 4 on wet soil surfaces runoff coefficients amounted to 59 0 79 5 for rock outcrops without cracks but were drastically reduced by the presence of cracks the surfaces with rock fragments resting on the soil generally located in the middle of the slopes prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil antecedent soil moisture had significant impact on runoff generation with wet soil having doubled runoff coefficient shortened time to runoff and increased runoff rate compared to the same but dry soil linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter plus rainfall intensity while the major controls for runoff coefficient were the bare soil and vegetation coverage plus rainfall intensity high infiltration rates measured at the micro plots agreed with low intra event runoff coefficients mostly below 1 observed under natural rainfalls at the hillslope runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth maximum hourly rainfall intensity and antecedent precipitation over 20days ap20 during the 1 5 year monitoring period from sep 2003 to mar 2005 the overall infiltration was 41 of the total rainfall amount and the maximum infiltration rate was almost 94 of the largest single rainfall event the results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas 2011 elsevier b v