evolution of a surge type glacier in its quiescent phase kongsvegen spitsbergen 1964 95 kongsyegen is a 102 km 2 sub polar polythermal surge type glacier in northwest spitsbergen svalbard it surged just before 1948 and is currently in its quiescent phase measurements of surface geometry since 1966 show a retreat of the front and strong thinning of up to 75 m in the ablation area and a build up of up to 32 m in the accumulation area present day annual velocities along the glacier are low from 1 4 up to 3 6 m a 1 the measured mean net balance for the period 1987 94 and the balance reconstructed back to 1967 show a weak positive balance of about 0 1 m w e the measured actual ice flux is low and the mass transfer down glacier at the ela is only about 3 20 of that required for steady state thus the glacier is building up towards a new surge the total thickening rate on kongsvegen is somewhat higher than in other cases from svalbard but it is small compared with other well studied surge type glaciers in alaska and he pamirs this relatively low rate of change is a function of the low accumulation rate and the relatively cold climate compared to other areas and is common for surge type glaciers in svalbard

seismic measurements reveal a saturated porous layer beneath an active antarctic ice stream seismic reflection studies recently conducted on ice stream b part of the marine ice sheet of west antarctica show a metres thick layer immediately beneath the ice in which both compressional p and shear s wave speeds are very low these low wave speeds imply that the material in the layer is highly porous and is saturated with water at a high pore pressure from this and from arguments presented in an accompanying paper1 to the effect that the layer would be too weak to support the shear stress exerted by the overlying ice we conclude that the layer is deforming and that the ice stream probably moves principally by such deformation

the behavior of u and th series nuclides in the estuarine environment rivers carry the products of continental weathering and continuously supply the oceans with a broad range of chemical constituents this erosional signature is however uniquely moderated by biogeochemical processing within estuaries estuaries are commonly described as complex filters at land sea margins where significant transformations can occur due to strong physico chemical gradients these changes differ for different classes of elements and can vary widely depending on the geographic location u and th series nuclides include a range of elements with vastly different characteristics and behaviors within such environments and the isotopic systematics provide methods for investigating the transport of these nuclides and other analog species across estuaries and into the coastal ocean there are numerous types and definitions of estuaries see dyer 1973 in this paper it is simply considered to be a region where freshwater and seawater mix to emphasize the chemical focus of the issues involved here this region can either be contained within a river channel or extend onto the shelf with effects often extending well into an adjoining ocean basin fairbridge 1980 these are complex ecological biogeochemical and hydrodynamic systems with strong gradients in the concentrations and composition of micro and macro particulate matter as well as dissolved organic and inorganic species particle reactive radionuclides and trace elements being transported across estuaries are subject to partitioning between the dissolved colloidal and particulate phases the variable chemical nature of the u and th series radionuclides is evident in their distributions in an estuarine environment such radionuclides can effectively serve as tracers to identify the sources fate and transport of particles and colloids as well as other pollutants that behave similarly to these nuclides these nuclides also have a wide range of half lives that can be used to examine processes over various time scales for example th and ra daughter isotopes have

modeling radium distribution in coastal aquifers during sea level changes the dead sea case abstract we present a new approach to studying the behavior of radium isotopes in a coastal aquifer in order to simulate radium isotope distributions in the dynamic flow field of the dead sea aquifer a multi species density dependent flow model sutra ms was used field data show that the activity of 226 ra decreases from 140 to 60 dpm l upon entering the aquifer from the dead sea and then further decreases linearly due to mixing with ra poor fresh water on the other hand an increase is observed in the activity of the shorter lived isotopes up to 52 dpm l 224 ra and 31 dpm l 223 ra which are relatively low in dead sea water up to 2 5 dpm l 224 ra and 0 5 dpm l 223 ra the activities of the short lived radium isotopes also decrease with decreasing salinity which is due to the effect of salinity on the adsorption of radium the relationship between 224 ra and salinity suggests that the adsorption partition coefficient k is linearly related to salinity simulations of the steady state conditions show that the distance where equilibrium activity is attained for each radium isotope is affected by the isotope half life k and the groundwater velocity resulting in a longer distance for the long lived radium isotopes k affects the radium distribution in transient conditions especially that of the long lived radium isotopes the transient conditions in the dead sea system with a 1 m yr lake level drop together with the radium field data constrains k to be relatively low 226 ra cannot be explained by adsorption and it is better explained by removal via coprecipitation probably with barite or celestine

sediment deformation beneath glaciers rheology and geological consequences experiments beneath breidamerkurjokull in iceland have led to development of flow laws for the subglacial till relating strain rate to shear stress and effective pressure and assuming either bingham fluid or nonlinearly viscous fluid behavior water pressures in the till are less than ice pressures and it is suggested that this may lead to infiltration of ice into the sediment which inhibits sliding at the ice sediment interface where water pressures are equal or near to ice pressures infiltration does not occur and sliding may result a one dimensional theory of subglacial deformation is developed in which the empirical flow law is coupled with a model of subglacial hydrology and consolidation this predicts stable states in which subglacial sediment either does not deform or a dilatant deforming horizon forms with positive effective pressures at the ice bed interface or unstable states where zero or negative effective pressures are predicted time dependent analyses show that response times following perturbations of the system may be of the order of 103 years and thus that unsteady behavior may be normal on glaciers flowing over unlithified sediment beds it is suggested that the natural variability of material properties in subglacial sediment beds leads to the development of drumlins on the glacier bed it is suggested that unstable deformation at zero or negative effective stress leads to piping in subglacial sediments at the glacier terminus and the growth of sediment floored subglacial tunnels their frequency is that which is sufficient to draw down subglacial water pressures so as to prevent unstable deformation where they discharge large water volumes subglacial sediments flow laterally toward them producing tunnel valleys this sediment is then removed by water flowing along the axial tunnel tunnel valleys can be regarded as the equivalent in soft sediment areas of eskers in bedrock areas

an improved method for ra isotope 226ra 228ra 224ra measurements by gamma spectrometry in natural waters application to co2 rich thermal waters from the french massif central abstract an improved method was developed to measure 226 ra 228 ra and 224 ra in freshwaters by gamma spectrometry radium was selectively extracted from acidified samples using specific filters 3m empore radium rad disks the latter was subsequently analysed by gamma spectrometry simultaneous and direct determination of the activities of the three isotopes was performed by comparison of gamma rays of the radium rad disks with those of a calibrated standard disk this efficient and reliable method allowed a reduction of sample processing to a few hours this technique was applied to analyse the ra isotope compositions of several co 2 rich hydrothermal springs of the western border of the limagne graben french massif central the studied springs emerge from a succession of granitic outcrops lined up along a major fault their chemical compositions evolve from calcic and magnesian chloro bicarbonated to sodic bicarbonated all the springs display high ra activities probably linked to high co 2 content and or high cation content of these waters with various ra isotope ratios 226 ra activity ranges from 588 to 2287 mbq l and 228 ra activity from 260 to 1590 mbq l whereas 224 ra displays an activity between 245 and 1808 mbq l four of the six analysed springs have 228 ra 226 ra activity ratios lower than 0 7 thus significantly lower than the ratio expected from an interaction with a calc alkaline granitoid typically having 232 th 238 u activity ratio between 1 and 2 low 228 ra 226 ra ratio 0 27 of the northern water montpensier suggests the existence in this area of a zone of u concentration possibly resulting from u mobilization and accumulation induced by previous hydrothermal events the 224 ra 228 ra ratios display smaller variations they suggest short transit times from the zone of ra leaching to the surface a few days or a very shallow addition of 224 ra e g from a localised zone where 228 th could be preferentially adsorbed on the mineral surfaces in some cases these ratios might be used to infer differences in transit times of waters between neighboring springs

glacier hydrology in svalbard norwegian high arctic abstract progress in glacier hydrology has focused on temperate glaciers although partly or wholly non temperate glaciers are found in many parts of the world and significant areas of former ice sheets were probably non temperate it has usually been assumed that drainage from non temperate glaciers consists of relatively dilute and invariable supraglacial runoff in this paper the hydrology of glaciers in the high arctic archipelago of svalbard is examined variations in the thermal regimes of glaciers and their implications for drainage are first addressed results from svalbard concerning meltwater discharge and storage and solute and suspended sediment dynamics are then reviewed in general meltwater penetration of non temperate ice is limited and drainage from non temperate glaciers in svalbard has many of the characteristics of sub aerial drainage however it would be erroneous to view this drainage simply as dilute supraglacial runoff as significant material transport occurs in suspension and solution furthermore twentieth century climate change has probably led to changes in the thermal regimes of some svalbard glaciers such that relict drainage structures are sometimes observed while meltwater yields are augmented by runoff which can be attributed to the loss of mass from glaciers at large spatial scales turbid plumes observed at the marine margins of polythermal ice caps indicate that meltwater can be routed subglacially through non temperate ice

positive mass balance during the late 20th century on austfonna svalbard revealed using satellite radar interferometry determining whether increasing temperature or precipitation will dominate the cryo spheric response to climate change is key to forecasting future sea level rise the volume of ice contained in the ice caps and glaciers of the arctic archipelago of svalbard is small compared with that of the greenland or antarctic ice sheets but is likely to be affected much more rapidly in the short term by climate change this study investigates the mass balance of austfonna svalbard s largest ice cap equilibrium line fluxes for the whole ice cap and for individual drainage basins were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio echo sounding these fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was 5 6 2 0 10 8 m 3 a 1 three basins in the quiescent phase of their surge cycles contributed 75 of this accumulation the remaining volume may be attributable either to as yet unidentified surge type glaciers or to increased precipitation this result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere

evaluation of lacustrine groundwater discharge and associated nutrients trace elements and dic loadings into qinghai lake in qinghai tibetan plateau using radium isotopes and hydrological methods abstract qinghai lake the largest lake in china with a surface area of 4260 km2 lies in the northeastern qinghai tibet plateau qtp at a mean altitude of 3194 m above sea level the lake has a water volume of 71 6 109 m3 a salinity ranges of 4 18 0 14 ppt to 12 3 0 14 ppt during sampling period which is about a half of typical seawater the aquifer systems at the lake shoreline have obvious saline water and freshwater mixing zones with similar hydrogeological and biogeochemical settings to coastal aquifers this study aims to estimate lacustrine groundwater discharge lgd and the associated chemical loadings to western qinghai lake naturally occurring radium isotopes 223ra 224ra 226ra and 228ra nutrients heavy metals and dissolved inorganic carbon dic were systematically investigated in different water endmembers of western qinghai lake lgd was estimated with radium inventory model and radium eddy diffusion model leading to a lgd estimate of 7 67 106 m3 d 1 and 8 52 106 m3 d 1 respectively the fresh groundwater discharge obtained based on regional water budget is about 5 97 106 m3 d 1 during sampling period accounting for 73 74 ranging from 53 22 to 80 43 of total lgd this study reveals that the fresh groundwater component is dominant in lgd of qinghai lake which is quite different from most coastal scenarios furthermore the chemical loadings derived from fresh lgd and recirculated lgd are evaluated the preliminary results indicate that fresh lgd is an important source of nutrient barium strontium uranium and dic to the lake and may significantly impact biogeochemical and ecological processes in the lake this study presents the first lgd estimate in the largest qtp saline lake in china and would be instructive to further similar studies in saline lakes in qtp and elsewhere in the world

226ra and 228ra in the mixing zones of the pee dee river winyah bay yangtze river and delaware bay estuaries 226ra and 228ra have non conservative excess concentrations in the mixing zones of the pee dee river winyah bay estuary the yangtze river estuary and the delaware bay estuary laboratory experiments using pee dee river sediment indicate desorption of 226ra to increase with increasing salinities up to 20 in winyah bay desorption from river borne sediments could contribute almost all of the increases for both isotopes desorption adds only a portion of the excess 228ra measured in the yangtse river and adjacent shelf waters and delaware bay in the yangtze river the mixing zone extends over a considerable portion of the continental shelf where 228ra is added to the water column by diffusion from bottom sediments while 226ra concentrations decrease from dilution diffusion of 228ra from bottom sediments in delaware bay primarily occurs in the upper part of the bay 22 water where fine grained sediments predominate a diffusive flux for 228ra of 0 33 dpm cm 2 year was determined for delaware bay

quantifying saline groundwater flow into a freshwater lake using the ra isotope quartet a case study from the sea of galilee lake kinneret israel we investigated the ra isotope quartet in order to quantify the discharge of saline groundwater into a freshwater lake the activities of 226ra 228ra 223ra and 224ra were measured in the sea of galilee israel surrounding saline springs and the jordan river coupled with u th and 226ra measurements in sediment cores and laboratory ra adsorption experiments under different salinity conditions the 226 ra activity 0 007 0 008 bq l 21 and 226 ra cl ratio in the lake were significantly lower than those of the inflowing saline springs indicating that 75 86 of the incoming 226 ra is removed from the lake water this missing ra is likely adsorbed onto suspended particles given the observed differential depletion of ra isotopes we present a model consisting of adsorption desorption recoil and decay of the short lived 224 ra and 223 ra isotopes we predict a removal time of 2 weeks for ra inferring the apparent residence time of suspended matter in the lake a mass balance calculation of the different 226ra inventories reveals a saline groundwater flux of 44 61 3 109 ly r 21 for fuliyatype water the residence time of dissolved 226ra in the lake is estimated as 3 4 yr the 228ra 226ra ratio of the lake water and a mass balance calculation show that 228ra arrives from regeneration though bottom sediments in addition to groundwater flux mass balance calculations of the expected saline fluxes before the diversion of saline inflows to the lake early 1960s provide 226ra activity estimates in the lake 0 018 0 020 bq l21 that are similar to the value 0 018 6 0 0001 bq l21 measured in the lake in 1962

u th ra fractionation during weathering and river transport the potential of radioactive disequilibria as tracers and chronometers of weathering processes has been recognised since the 1960 s e g rosholt et al 1966 hansen and stout 1968 this interest results from the dual property of the nuclides of the u and th radioactive series 1 to be fractionated during water rock interactions and 2 to have radioactive periods of the same order of magnitude as the time constants of many weathering processes and chemical transfers to ground and river waters therefore the study of radioactive disequilibria in surface environments should help to bring information about the nature the intensity but also the time scale of the water rock interactions produced during weathering and related chemical transfers these different properties have justified many of the studies on u th series in weathering profiles and river waters rosholt 1982 scott 1982 and osmond and ivanovich 1992 gave a synthesis of the studies of u series in weathering and surface hydrology up to the 1980 s and the 1990 s respectively here we present the main directions taken in these domains over the last decade they were partly stimulated by the analytical developments made in the measurement of the medium half life nuclides of 238u series i e 234u 230th 226ra in the mid 1980 s namely the use of thermal ionisation mass spectrometry tims e g chen et al 1986 edwards et al 1987 cohen et al 1991 chabaux 1993 chabaux et al 1994 and more recently the use of mc icp ms turner et al 2001 robinson et al 2002 for u and th isotope analysis details of these developments are given in this volume goldstein and stirling 2003 compared to the radioactive counting methods previously used the new techniques permit 1 a reduction by one order of magnitude or more of the size of the sample required for

determination of water ages and flushing rates using short lived radium isotopes in large estuarine system the yangtze river estuary china abstract we investigated the spatial and temporal distribution of naturally occurring short lived radium isotopes 224 ra t 1 2 3 6 d and 223 ra t 1 2 11 d to examine coastal water mixing dynamics of the third world largest estuary yangtze river estuary yre during two field trips in april 2010 and may 2011 distributions of the 224 ra 223 ra activity ratios within the yre area were used to calculate apparent estuarine water ages field derived results were then compared to hydrodynamic assessments obtained by a lagrangian particle tracking simulation experiment performed using the princeton ocean model pom water ages obtained via both geotracers and particle tracking agree very well during both field trips an anomalously younger water mass low salinity and higher radium activities was observed at about 90 170 km offshore distance from the mouth of the river suggesting an additional terrestrial water source influenced this area the temporal distribution of the radium isotopes indicated a semi diurnal tidal pattern in the yre with relatively constant isotopic composition of less than a 20 variation during our observations an integrated water flushing rate based on our observations excluding the additional anomalous source area was 8 4 km day 1

radium isotopes in the orinoco estuary and eastern caribbean sea radium isotopes provide a means of identifying the source of freshened waters in the ocean and determining the time elapsed since these waters were in the estuary we present evidence that during april waters from the amazon mixing zone pass within 50 km of the mouth of the orinoco river these amazon waters are characterized by a lower 228ra 226ra activity ratio ar than are waters from the orinoco at similar salinities during autumn the increased discharge of the orinoco displaces the freshened amazon waters seaward yet the two can be distinguished clearly within the caribbean sea waters of orinoco origin carry a characteristic radium signature including excess activities of 224ra this isotope may be used to estimate the time elapsed since the waters were removed from contact with sediments current speeds based on 224ra dating ranged from 15 to 33 cm s during april the radium isotopes also provide an assessment of sediment mixing in the estuary during low discharge april considerable mixing of older sediment by physical or biological processes or dredging maintained high activities of 228ra in the estuary and produced the highest 228ra 226ra ar s yet measured in any estuary during high discharge september a large fraction of the 228ra was derived from desorption from fresh sediment rather than mixing of older sediments activities of 224ra were high in the estuary during both high and low discharge indicating that considerable mixing of recently introduced sediment must occur during each period the high 224ra 228ra ar s measured in september imply that the same sediments were being resuspended during high discharge and that there was little exposure of older sediments which had been stored in the estuary for months to years during april 224ra and 228ra activities in the water were about equal indicating that most of the sediment being resuspended had been stored in the estuary long enough to reestablish radioactive equilibrium in the 232th decay series i e 20 years

using the radium quartet to quantify submarine groundwater discharge and porewater exchange abstract the specific ingrowth rates of different radium isotopes make them valuable tracers to distinguish processes occurring at different temporal scales here we demonstrate the use of the radium quartet 223ra 224ra 226ra and 228ra to differentiate flows of submarine groundwater discharge and porewater exchange to a coastal embayment alfacs bay nw mediterranean sea based on the assumption that these processes occur on different time scales in order to evaluate the seasonal dynamics of groundwater and porewater inputs to the bay we conducted three seasonal samplings at alfacs bay during which samples for ra isotopes were collected from bay waters groundwater springs porewaters and irrigation channels activities of short lived ra isotopes in the bay showed a strong seasonality e g average 224ra activities in summer 32 dpm 100 l 1 up to 4 times higher than in winter 8 dpm 100 l 1 in contrast the activities of the long lived ra isotopes were fairly constant throughout the year e g activities of 226ra were 16 and 14 dpm 100 l 1 in summer and winter respectively the relatively short exposure to sediments of recirculation fluxes resulted in porewaters significantly enriched in short lived ra isotopes relative to the long lived ones e g 224ra 1100 1300 dpm 100 l 1 226ra 17 99 dpm 100 l 1 whereas coastal groundwaters were enriched in all the ra isotopes e g 224ra 120 150 dpm 100 l 1 226ra 200 400 dpm 100 l 1 the distinct signatures of different sources allowed us to construct seasonal ra mass balances to estimate both groundwater discharge which ranges from 40 60 103 m3 d 1 in summer to 310 200 103 m3 d 1 in winter and porewater exchange fluxes ranging from 1200 120 103 m3 d 1 in summer to 270 40 103 m3 d 1 in winter whereas the seasonal variability of groundwater inputs is likely governed by the terrestrial hydraulic gradient a qualitative evaluation of the drivers of porewater exchange suggested that the strong seasonality of the seawater recirculation inputs is likely mediated by seasonal cycles on the activity of benthic infauna ra isotopes are thus valuable tracers to differentiate fluxes of both submarine groundwater discharge and porewater exchange allowing a more accurate evaluation of the fluxes of freshwater and solutes to coastal ecosystems as well as their implications for coastal biogeochemical cycles

groundwater ages and reaction rates during seawater circulation in the dead sea aquifer the dead sea system provides a unique opportunity to study flow velocities and reaction rates during seawater circulation in the aquifer we present here a novel application of calculating groundwater age and velocity along the flow path of the hypersaline water from the dead sea into the aquifer using the buildup rate of 228 ra in this water the calculated circulation velocities are 1 10 m y which is in agreement with estimates based on the na cl ratios in this water 1 5 4 m y the latter is unique to the dead sea aquifer system where the na cl ratio has been decreasing during the past 50 years due to the precipitation of halite in the lake the velocity estimates facilitated the calculation of the rates of water rock interactions in the dead sea aquifer

horizontal mixing of great barrier reef waters offshore diffusivity determined from radium isotope distribution the great barrier reef gbr northern australia is the largest coral reef system in the world and provides habitat for highly diverse tropical marine ecosystems mixing in the coastal waters of the gbr is an important parameter influencing the health of these ecosystems we have used the distribution of the four naturally occurring radium isotopes to determine the rate of mixing of nearshore waters of the central part of the gbr lagoon with water from the coral sea the observed radium distribution is modeled using a one dimensional diffusion model the model improves on previous radium offshore mixing models by incorporating the benthic flux of radium diffusing across the sediment water interface and offshore changes in water column depth we find that the inner lagoon diffusivity 20 km offshore is best estimated using the short lived isotopes 224ra and 223ra the concordance of k x estimated using the two different isotopes and the apparent consistency between measured riverine inflows to the lagoon and inflows inferred from the modeled salinity distribution provide confidence in the results the mean value of k x for the inner lagoon region of the southern central zone between latitudes 15 8 s and 19 0 s 265 36 m2 s 1 is more than twice that in the northern central zone 14 3 s to 15 8 s this difference likely reflects the different reef matrix density in the two zones the distribution of the longer lived isotope 228ra indicates more rapid mixing in the middle and outer lagoon these results indicate that central gbr water within 20 km of coast is flushed with outer lagoon water on a timescale of 18 45 days with the flushing time increasing northward

application of radon and radium isotopes to groundwater flow dynamics an example from the dead sea abstract this study presents the behavior of radon and radium isotopes and their application to groundwater age and flow dynamics the research was conducted in the complex dead sea groundwater system which includes a large variety of sediments groundwater salinities flow mechanisms and groundwater ages groundwater around the dead sea contains high activities of radon up to tens of thousands dpm l and radium up to hundreds dpm l adsorption of radium which is partially salinity controlled is an important source of unsupported 222 rn which is used for estimating the adsorption partition coefficient of radium in addition to salinity the concentration of mn and fe oxides and aquifer heterogeneity are important factors controlling the adsorption partition coefficient the different nature of the rocks on both sides of the dead sea transform with lower th u ratios in the carbonate rocks on the western catchment of the dead sea compared to higher ratios in the sandstone aquifer east of the dead sea is reflected in a higher 228 ra 226 ra activity ratio in the eastern compared with the western groundwaters averages of 0 76 and 0 15 respectively the different groundwater groups around the dead sea contain secular or non secular equilibrium ratios which depend on the age of the groundwater the time since the groundwater entered the aquifer or whether the groundwater system is in a steady state the age of the groundwater system young groundwater such as the dead sea water that circulates in the aquifer or freshwater springs is depleted in the long lived radium isotopes compared to the short lived isotopes whereas old groundwater contains relatively high activity of 226 ra 500 dpm l and the radium activity ratios are close to secular equilibrium the common secular equilibrium ratios between all four radium isotopes in the dead sea groundwaters suggest that many of the groundwater flow paths did not change significantly during the past 8000 years

the behavior of u and th series nuclides in groundwater groundwater has long been an active area of research driven by its importance both as a societal resource and as a component in the global hydrological cycle key issues in groundwater research include inferring rates of transport of chemical constituents determining the ages of groundwater and tracing water masses using chemical fingerprints while information on the trace elements pertinent to these topics can be obtained from aquifer tests using experimentally introduced tracers and from laboratory experiments on aquifer materials these studies are necessarily limited in time and space regional studies of aquifers can focus on greater scales and time periods but must contend with greater complexities and variations in this regard the isotopic systematics of the naturally occurring radionuclides in the u and th decay series have been invaluable in investigating aquifer behavior of u th and ra these nuclides are present in all groundwaters and are each represented by several isotopes with very different half lives so that processes occurring over a range of time scales can be studied table 1 within the host aquifer minerals the radionuclides in each decay series are generally expected to be in secular equilibrium and so have equal activities see bourdon et al 2003 in contrast these nuclides exhibit strong relative fractionations within the surrounding groundwaters that reflect contrasting behavior during release into the water and during interaction with the surrounding host aquifer rocks radionuclide data can be used within the framework of models of the processes involved to obtain quantitative assessments of radionuclide release from aquifer rocks and groundwater migration rates the isotopic variations that are generated also have the potential for providing fingerprints for groundwaters from specific aquifer environments and have even been explored as a means for calculating groundwater ages view this table table 1 radionuclides important in groundwater studies the highly fractionated nature of the

evaluating the source and seasonality of submarine groundwater discharge using a radon 222 pore water transport model article i nfo pore water radon 222 rn distributions from indian river lagoon florida are characterized by three zones a lower zone where pore water 222 rn and sediment bound radium 226 ra are in equilibrium and concentration gradients are vertical a middle zone where 222 rn is in excess of sediment bound 226 ra and concentration gradients are concave downward and an upper zone where 222 rn concentration gradients are

occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers sr s o h ra rn abstract salinization in groundwater systems can induce water rock interaction including the release of naturally occurring trace elements of health significance such as radium ra with possible implications for the usability of water resources in addition to the increase of dissolved solids tds concentrations in general radium mobility is limited by chemical removal mechanisms including adsorption onto clays and or mn and fe oxides exchange processes and coprecipitation with secondary barite in order to examine the effect of aquifer salinity gradients on the distribution of naturally occurring ra in fresh to saline groundwater and the relationship to water rock interaction and ra removal mechanisms two contrasting systems were investigated the shallow unconfined coastal aquifer in agadir southwestern morocco and the confined cretaceous cape fear and pliocene yorktown aquifers of the atlantic coastal plain north carolina usa geochemical and isotopic indicators of salinity sources e g cation ratios 18o 2h br cl 34 s so 4 2 18 o so 4 2 were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water rock interaction radium activities 224ra 226ra 228ra radon 222 alkaline earth metal mg ca sr ba concentrations and ratios and 87sr 86sr ratios were analyzed to identify water rock interaction processes affecting alkaline earth metals including ra the morocco coastal aquifer is generally oxic exhibits a range of salinity and water types cl 163 2120 mg l median 932 mg l and exhibits ca na ratios above the seawater value typical of monovalent divalent cation exchange base exchange reactions in coastal aquifers in contrast the atlantic coastal plain aquifers are anoxic sulfate reducing cover a wider salinity range cl 5 9890 mg l median 800 mg l representing a transition between na hco 3 and na cl waters and exhibit ca na ratios below that of modern seawater typical of reverse base exchange reactions possible salinity sources in the morocco coastal aquifer include seawater intrusion mesozoic evaporites other natural saline waters and or wastewater whereas the atlantic coastal plain is primarily affected by old seawater present in the aquifer system radium activities are generally low and vary significantly within each aquifer for example 226ra ranges from 1 8 27 7 mbq l in the morocco coastal aquifer median 8 1 mbq l and 1 9 214 mbq l in the atlantic coastal plain median 18 9 mbq l the highest ra activities were observed in the most saline wells sampled in the atlantic coastal plain at total dissolved solids tds concentrations above an apparent threshold of 5000 mg l radium activities increase in a generally linear fashion with salinity in the atlantic coastal plain broadly comparable to previous studies indicating a threshold range of 3000 10 000 mg l at lower tds concentrations water rock interaction processes that vary with local aquifer conditions appear to control ra distribution rather than merely salinity in the morocco coastal aquifer adsorption of ra and coprecipitation with secondary barite are apparently favorable to control ra levels in groundwater radium removal in the anoxic atlantic coastal plain aquifers appears to be associated with adsorption and or exchange processes with the additional possibility of barite precipitation in the cape fear aquifer indicated by barite saturation overall the locally variable factors that can control ra sources and mobility in fresh to brackish groundwater at near neutral ph include variation in solid phase radioactivity redox state affecting adsorption sites availability of competing divalent cations and barite saturation

modelling the effect of salinity on radium desorption from sediments abstract the desorption of the four naturally occurring radium isotopes 223 ra 224 ra 226 ra and 228 ra from estuarine sediments is investigated these isotopes are created within sediments by the radioactive decay of insoluble thorium parents due to competition from other ions for the occupation of adsorption sites on the sediment grains radium desorption is a function of salinity a model is developed to describe radium desorption as it is affected by salinity grain size and sediment concentration it is shown that to model the desorption of radium for a particular sediment requires the estimation of two independent parameters one of these parameters is the concentration of radium available for exchange on the sediment the other depends on major ion and radium exchange coefficients desorption experiments performed on sediments from the bed of the bega river australia are used to validate the model and to evaluate the parameters needed for model application

tidally regulated chemical fluxes across the sediment water interface in elkhorn slough california evidence from a coupled geochemical and hydrodynamic approach measurements of four ra isotopes ba mn u and dissolved nutrients were used in concert with hydrodynamic modeling to reveal a large tidally regulated sediment surface water exchange within elkhorn slough an estuary in monterey bay california hydrologic and oceanographic data from in situ sensors and geophysical surveys of estuarine bottom sediments were integrated with the chemical measurements to develop ra flux boundary conditions for a three dimensional hydrodynamic transport model of the estuary sediment and surface water exchange is the dominant source of ra isotopes within this system this process occurs without significant fresh terrestrial groundwater discharge a number of known solute transport and pore water flushing mechanisms can explain the 224ra input including diffusion evaporative transport bioirrigation and inundation and drainage of borrows and macropores the 226ra results suggest that some of these mechanisms or others are capable of mobilizing ra from deeper sediments the sediments supplying this flux may cover an area as large as the entire intertidal zone primarily salt marsh to a depth of 1 2 cm in addition the ra delivery to the estuary appears to be temporally regulated by the tidal inundation of the salt marsh and subsequent drainage through tidal creek channels these results illustrate the importance of the intertidal zone as a flowpath in the estuarine water cycle and the tidal phase lag that results when solute from this zone is transported into the estuary this process is essential to understanding estuarine biogeochemical budgets of elements with significant sedimentary sources among marine environments estuaries stand out for their high biologic productivity numerous societal functions and hydrologic and chemical complexity because of their complexity and variability estuaries are also challenging environments to study and even more so to predict large tidal excursions temporally variable freshwater inputs and stratification can confound efforts to relate water chemistry to anything but the largest features e g riverine inputs mixing processes and thus net tidal exchange are spatially and temporally variable in many estuaries uncles 2002 making it difficult to predict chemical exchange with the sea the complex morphology of intertidal salt marshes and mudflats results in irregularly flushed areas where evaporation and stagnation can alter the salinity trace element and nutrient chemistry of intertidal water such water is ultimately remixed back into the main estuary influencing surface water chemistry sediment pore waters also possess distinct chemical characteristics and can influence surface water chemistry through a variety of exchange processes huettel et al 1998 charette and sholkovitz 2006 in shelf sands intertidal sand flats and other permeable sediments the dominant solute exchange mechanism is pressure induced advection created by the interaction of currents waves

using ra isotopes to examine transport processes controlling benthic fluxes into a shallow estuarine lagoon measurements of the benthic flux of four naturally occurring radium isotopes in a shallow lagoon in the bega river estuary has provided information on the types and rates of transport processes operating in the lagoon sediments the measurement techniques included ra mass budgets of the lagoon ra fluxes into benthic chambers and modelling of the pore water and solid phase ra profiles in a sediment core the sediment profile of 210pb and the solid phase and pore water profiles of the longer lived ra isotopes 228ra half life 5 7 years and 226ra half life 1600 years indicate bioturbation to a depth of 10 cm a diffusion bioturbation model has been used to assess the relative importance of molecular diffusion and bioturbation as transport processes controlling the benthic flux of ra the flux of the shortest lived isotope 224ra half life 3 7 days is not significantly enhanced by bioturbation and its flux is consistent with diffusion controlled release however bioturbation enhances the 228ra flux by a factor of more than two over the flux due to molecular diffusion alone modelled pore water profiles and flux calculations are consistent with a bioturbation time scale between 0 5 and 2 years the measured benthic flux of 226ra is much greater than can be accounted for by the modelled profile and may be due to slow 226ra desorption from the sediment variable sediment accumulation rates or groundwater flow based on 226ra pore water and flux measurements at the time of this study groundwater flow has an upper limit of 0 3 cm d 1

assessing the paradigm shift deformable glacier beds abstract during the mid 1980s glaciologists recognised that many glaciers and ice masses overlie soft sediments rather than hard bedrock these sediments are typically weaker than glacier ice and may therefore deform this realisation was heralded as a paradigm shift in glaciology since this realisation a wide body of theoretical and field based research has been undertaken to assess the mechanical and hydrological significance of such substrates we review the techniques and results of this work and attempt to assess this paradigm shift in glaciology and in particular its importance for quaternary scientists we suggest areas of research that remain unanswered and identify those in which glacial geology in particular may be able to inform glaciologists

tracing the amazon component of surface atlantic water using 228ra salinity and silica high 228ra 226ra activity ratios characteristic of waters in the amazon estuary provide a sensitive indicator of the presence of these waters in the atlantic ocean a conservative mixing model utilizing the 228ra 226ra activity ratio ar tied to absolute measurements in the estuary allows us to estimate that 20 34 of the surface water east of the antilles during june 5 9 from the same area during december and 15 20 of the eastern caribbean surface water during december are derived from the amazon estuary differences in 228ra input occur in response to variable stratification of water near the river mouth during high discharge intense vertical mixing enriches the water in the estuary in 22sra a large fraction of this water moves to the north and east of the antilles where its relatively high 22sra 226ra ar distinguishes it over 1500 km from its source during low discharge northern hemisphere fall a significant fraction of river water passes northwest of the zone of intense mixing into a vertically stratified region where 228ra gain is lower this water is transported by the guiana current along the coast of south america and into the caribbean

laminated sediments in glacimarine environments diagnostic criteria for their interpretation abstract fine grained laminated deposits are often reported from contemporary and ancient glacimarine sedimentary sequences laminated glacimarine sediments form by a variety of processes including suspension settling from turbid overflow plumes turbidity current deposition and contour current activity subglacial deformation of pre existing sediments may also produce laminated deposits in the form of glacitectonite and deformation till the development of diagnostic criteria for genetic discrimination of laminated glacimarine sediments is important both for their correct interpretation in sedimentary sequences and also for the accurate reconstruction of former glacier extent and geometry as laminated sediments may form in subglacial ice proximal and ice distal environments this paper reviews the processes by which laminated glacimarine sediments form and their resulting sedimentology the aim is to provide a synthesis of diagnostic sedimentological criteria for laminated glacimarine deposits that will assist in the interpretation of such sediments in the geological record laminated sediments are genetically differentiated on the basis of sedimentary structures bedding contacts stratigraphic relationships and macrofaunal content bioturbation these attributes also facilitate discrimination between glacimarine and glacilacustrine rhythmites the paper concludes by discussing the glaciological significance of laminated glacimarine sediments in terms of glacier hydrology reconstructions of former ice dynamics and basal thermal regime

the dynamics of ice sheet outlets a comparison of data from aircraft altimetry landsat imagery and radia echo sounding has shown characteristic surface topographies associated with sheet and stream flow the transition between the two is abrupt and occurs at a step in the subglacial topography this marks the onset of basal sliding and high velocities caused by subglacial water it results in crevassed amphitheatre like basins round the head of outlet glaciers it is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase this abrupt transition appears to be topographically controlled since basal temperatures are at the pressure melting point well inland of the change in regime the marie byrd land ice streams exhibit qualitative differences from other ice sheet outlets however the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice the repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion this is concentrated towards the heads of outlet glaciers up stream of the region where significant basal decoupling occurs this may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls

ra and th adsorption coefficients in lakes lake kinneret sea of galilee natural experiment the adsorption rate constants of ra and th were estimated from empirical data from a freshwater lake and its feeding saline springs we utilized the unique setting of lake kinneret sea of galilee northern israel in which most of the ra and th nuclides are introduced into the lake by saline springs with high 226 ra activities and a high 224 ra 228 ra ratio of 1 5 the mixing of the ra enriched saline waters and freshwater in the lake causes the 224 ra 228 ra ratio to drop down to 0 1 in the kinneret due to preferential adsorption of 228 th these conditions constitute a natural experiment for estimating adsorption rates we developed a simple mass balance model for the radionuclides in lake kinneret that accurately predicted the ra isotope ratios and the 226 ra activity in the lake the model is comprised of simultaneous equations one for each radionuclide the equations have one input term supply of radionuclides from the saline springs and three output terms adsorption on particles in the lake radioactive decay and outflow from the lake the redundancy in the analytical solutions to the mass balance equations for the relevant nuclides constrained the values of ra and th adsorption rate constants to a very narrow range our results indicate that the adsorption rate constant for ra is between 0 005 d 1 and 0 02 d 1 the rate constant for th is between 0 5 d 1 and 1 d 1 about fifty to a hundred times higher the estimated desorption rate coefficient for ra is about 50 100 times larger than its adsorption rate constant the mass balance equations show that the residence times of all ra isotopes 226 ra 228 ra 223 ra 224 ra and of 228 th in the lake are about 95 92 14 6 and 1 d respectively these residence

basaltic magmatism on the moon a perspective from volcanic picritic glass beads abstract it is widely accepted that basaltic magmas are products of partial fusion of periodotite within planetary mantles as such they provide valuable insights into the composition structure and processes of planetary interiors those compositions which approach primary melt compositions provide the most direct information about planetary interiors and serve as a starting point to understand basaltic evolution within the collection of lunar samples returned by the apollo and luna missions are homogeneous picritic glass beads of volcanic origin these picritic glasses are our closest approximations to primary magmas as such these glass beads provide a unique perspective concerning the origin of mare basalts the characteristics of the lunar interior and processes in the early differentiation of the moon we have obtained trace element data for these picritic glasses using sims techniques these data and literature isotopic and experimental data on the picritic glasses are placed within the framework of mare basaltic magmatism the volcanic glasses are very diverse in their trace element characteristics for example they have a wide range of ree pattern shapes and concentrations like the crystalline mare basalts all picritic glasses have a negative eu anomaly unlike the crystalline mare basalts there is little correlation between the size of the eu anomaly and overall ree concentrations trace element differences among the various glasses suggests that a kreep component was incorporated into their mantle source this implies large scale mixing of the lunar magma ocean derived cumulate pile subtle differences among glasses suggest that local mixing of sources may also have been an important process preservation of subtle chemical differences in the picritic glasses and crystalline basalts may be interpreted as indicating that they were produced by small to moderate degrees of partial melting and that the lunar mantle did not experience extensive melting during episodes of mare volcanism several lines of evidence are consistent with the view that the picritic glasses were derived from mantle sources that were compositionally distinct from the sources for crystalline mare basalts these are parallel but no common liquid lines of descent chemical differences between picritic glasses and the more primitive crystalline mare basalts experimental studies indicating that the picritic glasses are multiply saturated at depths greater than that of the mare basalts differences in lead isotopic data and the mode of eruption i e fire fountaining for glass beads these data also provide circumstantial evidence that suggests that the picritic glasses were derived from a source somewhat more volatile rich than that of the mare basalts several petrogenetic models are suggested by the trace element characteristics of the picritic glasses 1 1 partial melting of heterogeneous lunar mantle at depths greater than 300 km to produce the parental magmas picritic for both the mare basalts and picritic glasses picritic magmas represented by glass beads were erupted to the surface with small degrees of fractional crystallization while mare basalts were produced by larger degrees of fractional crystallization 15 30 of similar but not identical picritic magmas 2 2 picritic magmas represented by the glass beads were generated at depths greater than 400 km in a volatile enriched relative to the mare basalt source heterogeneous mantle while mare basalts are fractional crystallization products of picritic magmas generated at depths of less than 400 km 3 3 the picritic magmas represented by the glass beads represent polybaric melting that initiated at depths of at least 1000 km a primitive mantle component or less processed cumulate mantle components may have been involved in the generation of the picritic glasses in any of these models

determining groundwater ra end member values for the estimation of the magnitude of submarine groundwater discharge using ra isotope tracers radium isotopes 228ra and 226ra are excellent tracers of submarine groundwater discharge sgd to estimate sgd magnitudes information on the end member values of ra concentrations in groundwater is critical however the distribution characteristics of ra in coastal aquifers are poorly understood in this study we show that ra concentrations in coastal groundwater are primarily dependent on salinity based on the data n 500 obtained from global coastal aquifers although previous end member calculations averaged all ra concentrations without considering salinity if we assume that sgd is composed mainly of seawater infiltrating the aquifer previous estimates of sgd for the atlantic ocean and the global ocean were overestimated twofold to threefold this may be similar for other applications using different ra isotopes our study highlights that the end members of ra isotopes in groundwater should be carefully considered when estimating sgd using ra isotope mass balances in the ocean

nutrient inputs to the coastal ocean from submarine groundwater discharge in a groundwater dominated system relation to land use kona coast hawaii u s a we evaluated the magnitude and composition in terms of salinity 223ra and 224ra activity and nutrient concentrations of submarine groundwater discharge sgd fluxes at 11 sites on the kona coast of hawaii discharging groundwater was typically brackish to saline and had high ra activity relative to ocean water and fresher inland groundwater brackish sgd fluxes estimated using a mass balance approach based on excess coastal ocean 224ra activity ranged from 3 to 1300 l m21 of coastline min21 fluxes of the freshwater component of sgd calculated based on salinity ranged from 2 to 310 l m21 min21 nutrient fluxes into coastal waters from sgd varied by up to three orders of magnitude among sites nitrate nitrite n n phosphate and silica concentrations showed strong inverse linear correlations with salinity in coastal seawater and groundwater these correlations were consistent with previous work that documented conservative mixing between fresh highnutrient groundwater and saline low nutrient seawater at a few coastal ocean sites we extend this conservative relationship to more coastal ocean sites and to groundwater in the coastal aquifer n n concentrations in the fresh component of discharging groundwater were higher at sites near golf courses and those with a greater percentage of bare land within a 5 km radius and silica concentrations in the fresh component of discharging groundwater were higher at sites with more bare land and lower population densities however neither urbanization nor agriculture was significantly correlated with groundwater nutrient concentrations on this relatively undeveloped coast

groundwater transport and radium variability in coastal porewaters abstract radium isotopes 223 ra t 1 2 11 4 d 224 ra t 1 2 3 66 d 226 ra t 1 2 1600 y and 228 ra t 1 2 5 75 y are considered excellent tracers of groundwater movement and discharge in coastal systems however spatial and temporal variability in porewater radium activity have raised questions about the accuracy of these tracers to better understand the factors affecting radium variability in coastal systems measurements of porewater and surface water radium activity were made at an island in north inlet salt marsh in georgetown south carolina from november 2009 to february 2011 water salinity temperature ph and redox potential were also recorded and sediment samples were collected for analysis of bulk 228 ra and 226 ra activity hydraulic head observations during 2007 2008 from piezometers on the island were used to generate independent estimates of groundwater fluxes porewater radium activities decreased with depth below the marsh surface and increased with distance from the creek banks salinity measurements were lower and redox potential higher near the marsh creeks the stratigraphy of the island is typical of intertidal wetlands in the southeastern u s with a mud layer overlying a confined sandy aquifer the observed patterns in porewater radium salinity and redox potential were consistent with 1 shorter porewater residence times in the permeable sand aquifer than in the low permeability mud 2 differences in grain size between the mud and sand and 3 greater tidal exchange near the creeks temporal variations in porewater radium activity were not associated with salinity ph and redox potential although temperature provided significant control p 2 228 ra and 226 ra activity lower mean sea water levels resulted in greater calculated groundwater discharge and were also associated with lower average porewater 224 ra and 223 ra activity in that groundwater discharge variations strongly affected short lived radium activity at this site the 228 ra 226 ra activity ratios in the surface water and porewater signified that the confined aquifer rather than the surficial mud was the primary source of radium to the surface water our results highlight the importance of understanding the hydrology of any coastal system when interpreting radium results it is also essential to identify and measure the correct porewater end member s i e source aquifers when calculating radium budgets

calibrating a surface mass balance model for austfonna ice cap svalbard austfonna 8120 km 2 is by far the largest ice mass in the svalbard archipelago there is considerable uncertainty about its current state of balance and its possible response to climate change over the 2004 05 period we collected continuous meteorological data series from the ice cap performed mass balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground penetrating radar along several profile lines these data are used to drive and test a model of the surface mass balance the spatial accumulation pattern was derived from the snow depth profiles using regression techniques and ablation was calculated using a temperature index approach model parameters were calibrated using the available field data parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably testing model results against multiple criteria is an efficient method to cope with non uniqueness in doing so a range of different data and observations was compared to several different aspects of the model results we find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation which suggests that refreezing processes play an important role to represent these effects in the model a simple pmax approach was included in its formulation used as a diagnostic tool the model suggests that the surface mass balance for the period 29 april 2004 to 23 april 2005 was negative 318 mm w e

seasonal cycles in radium and barium within a subterranean estuary implications for groundwater derived chemical fluxes to surface waters abstract there is increasing evidence that submarine groundwater discharge sgd is an important source of water and dissolved materials to the ocean one of the primary tracers of this process is the quartet of radium isotopes 223 ra 224 ra 226 ra and 228 ra whereby excess activities in surface waters can often be attributed to an input supplied via sgd this approach requires the radium end member activity to be well constrained however natural variability in groundwater radium may span several orders of magnitude therefore this variability is usually the main driver of uncertainties in volumetric sgd estimates to investigate the physical and biogeochemical controls on groundwater radium activities we conducted a three year time series of radium and barium a chemical analogue for radium within the subterranean estuary of a coastal aquifer waquoit bay ma usa gonneea et al 2013 demonstrated that movement of the salinity interface within the subterranean estuary is driven by changes in the hydraulic gradient between groundwater level and sea level height for waquoit bay seasonal scale sea level change not groundwater level was the main driver in hydraulic gradient fluctuations seasonal changes in groundwater chemistry can be attributed to the resulting movement of the salinity transition zone between terrestrial and marine groundwater landward movement of the interface results in a large release of radium isotopes 226 ra 1400 dpm 100 l 1 and barium 3000 nmol kg 1 associated with an increase in groundwater salinity the magnitude of these releases cannot be explained by in situ production or weathering alone but is likely due to salinity driven desorption from surface bound sediment inventory the timing of these peak concentrations is not always in phase with model derived estimates of sgd as a result the groundwater concentration rather than the water flux is the main driver of ra and ba inputs to waquoit bay surface waters the behavior of the subterranean estuary as an ion exchange reservoir has important implications for the timing and flux of various nutrients and pollutants that transit this region prior to discharge in addition to modulating chemical fluxes via submarine groundwater discharge on seasonal time scales transgression of the subterranean estuary may alter the input of chemicals to the ocean on decadal and longer time scales during this study the observed excess flux of 226 ra and ba from the subterranean estuary can be accounted for with sorbed sediment pools and accelerating rates of sea level rise in this region

the surface topography of large ice masses from landsat imagery les images de landsat mss de l antarctique et du svalbard ont ete comparees a des mesures altimetriques effectuees a partir d avion

subglacial meltwater discharge in the open marine tidewater glacier environment observations from nordaustlandet svalbard archipelago the ice proximal environment of the nordaustlandet tidewater ice cap svalbard archipelago is one of the best analogues for understanding glacial geologic processes of northern continental shelves during initial pleistocene deglaciation investigations of the proglacial region in 1980 1983 showed that the sedimentary environment is dominated by numerous meltwater outflows which discharge sediment laden water from subglacial meltwater streams during the summer two large stable meltwater outflows were observed in embayments along the southern part of the ice front landsat images show that both outflows have been in approximately the same position since at least 1976 they are located at the intersection of glacial drainage basins and centered over depressions in the underlying bedrock an outflow valley extending away from the ice front was observed in front of the western meltwater outflow sidescan sonar profiling along the glacier front showed a 200 m wide gap in acoustic reflection at the base of the western meltwater outflow probably caused by meltwater effluence enhanced sediment accumulations in this region observed as a 3 ms sediment drape in front of the outflow and large arcuate ridges in the outflow valley testify to the transport efficiency of the subglacial meltwater stream several mounds up to about 25 m high and 200 m wide are observed on sidescan and 3 5 khz profiles directly in front of the outflow although samples from these structures are absent they are most likely composed of sediment and are similar to beaded eskers observed in pleistocene glacimarine sequences indicating locally very high sedimentation rates fine grained components of the subglacial discharge incorporated in the buoyant meltwater plume are usually entrained in a westerly coastal current elevated suspended particulate material concentrations are observed within the coastal waters in a region extending about 15 km perpendicular to the glacier front and at least 60 km along the ice front extending into the northwestern barents sea

postglacial emergence of western franz josef land russian and retreat of the barents sea ice sheet uncertainty remains on the timing and extent of late weichselian glaciers over the qsr barents and kara sea shelves franz josef land russia is a critical area for deciphering the record of glacier fluctuations and postglacial relative sea level change coastal forelands on the archipelago are covered by a well preserved raised beach sequence containing abundant and pristine driftwood whalebone and shell 4c dating of these materials provides site specific emergence records for the archipelago and some of the oldest ages on deglaciation of 10 400 bp three apparent still stands in emergence are inferred from morphology of the raised beach sequence and 4c dating between 9900 and 6200 bp and at ca 5500 bp and 3500 bp the earliest sea level arrest after formation of the marine limit reflects a balance between glacio isostasy and eustasy concomitant with the final phase of global sea level rise the latter two sea level arrests during the middle to late holocene are less pronounced and may indicate increased height of the ocean surface with greater storminess and extended open water conditions raised beaches at 1 2 m a s l and j4c dated at 1000 to 2000 bp give contemporary emergence rates of 1 to 2 mm year the low current rates of emergence on franz josef land are similar to areas in fennoscandinavia that sustained modest late weichselian glacier loads 1500 m within a few 100s of km of the inferred ice sheet margin the pattern of postglacial emergence and strandline tilts indicates that past glacier loads were greater over the adjacent barents sea than franz josef land marine and terrestrial records from franz josef land place retreat of glaciers from coastal areas by 10 400 bp whereas the adjacent franz victoria trough was deglaciated by 13 000 bp retreat of the barents sea ice sheet was probably underway by 13 500 bp coincident with rising global sea level and elevated summer insolation we infer that iceberg calving through the deep troughs bordering the barents sea particularly with rapidly rising sea level ca 12 000 bp was an important process controlling the demise of the barents sea ice sheet copyright 1996 elsevier science ltd

subglacial till a physical framework for its properties and processes the continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized the proposed framework is provisional in two senses the constitutive description of till will require improvement and not all potentially significant processes have been included till is treated as a three component mixture of water clasts coarse grained solids and fine grained matrix solids these components obey mass balance equations and their behavior is subject to constitutive relations that describe such processes as darcian water transport fine grained sediment transport consolidation shear deformation dilatancy and comminution five state variables uniquely determine the compressibility permeability shear strength and other physical properties numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment

use of radium isotopes to examine pore water exchange in an estuary the measured distributions of four isotopes of ra along the estuary of the bega river are used to examine sediment water column exchange ra is created in estuarine sediments by the radioactive decay of insoluble th parents residing close to or on the surfaces of the sediment grains ra desorbed into the pore water is continuously lost to the water column due to the cyclical draining and filling of the sediments by the tides the distribution of ra in the estuary is governed by its rate of loss from the sediments its advection along the estuary resulting from river discharge into the estuary s head tidal mixing and radioactive decay these processes are all described in a model matching of model predicted ra concentrations with measurements allows an estimate of the effective depth in the sediments to which the pore water is exchanged every tidal cycle this depth is large 15 cm but it is shown to be reasonable for the bega estuary

submarine groundwater discharge in a subsiding coastal lowland a 226ra and 222rn investigation in the southern venice lagoon several recent studies have suggested that submarine groundwater discharge sgd occurs in the venice lagoon with discharge rates on the same order or larger than the surface runoff as demonstrated previously in several other coastal zones around the world here the first set of 222rn data along with new 226ra data are reported in order to investigate the occurrence and magnitude of sgd specifically in the southern basin of the lagoon the independent connection with the adriatic sea at the chioggia inlet in addition to the relative isolation of the water body from the main lagoon make this area an interesting case study there is probably only minimal fresh groundwater flux to the lagoon because the surrounding aquifer is subsiding and mainly has a lower hydraulic head than seawater the data show that the ra and rn activities are in slight excess in the lagoon compared to the open sea with values on the same order as those observed in the northern and central basins taking into account the water exchange rate between the lagoon and adjacent seawater provided by previous hydrodynamic numerical modelling it is shown that this excess cannot be supported at steady state by only riverine input and by diffusive release from the sediment interstitial water high activities observed in groundwater samples collected from 16 piezometers tapping into the shallow aquifer over the coastal lowland substantiate that the excess radioactivity in the lagoon may indeed be due to the advection of groundwater directly into the lagoon bottom water through the sediment interface however the data show that the groundwater composition is extremely heterogeneous with high ra activities concentrated within a narrow coastal strip where the contact between fresh and saline water takes place while rn strongly decreases when approaching the lagoon shore across the 20 km coastal plain assuming that the average groundwater activities measured in the coastal strip are representative of the sgd composition a sgd flux of 7 7 3 5 105 and 2 5 2 106 m3 d is calculated using a 226ra and 222rn budget respectively i e about 1 3 times the surface runoff substantially lower than in previous studies the influence of all assumptions on sgd estimates groundwater heterogeneity diffusive sediment flux one box versus multi boxes model calculations is discussed and a sensitivity analysis of the influence of imperfect exchange and mixing at the lagoon outlets that affects the lagoon composition is provided finally the results confirm that the sgd flux calculated with these assumptions is largely 80 composed of saline lagoon water circulating through the sediment under the lagoon margin and that the fresh water discharge associated with sgd is at most a minor term in the lagoon hydrologic balance