the hafnium neodymium isotopic composition of atlantic seawater the first full water column hafnium isotopic compositions of atlantic seawater have been obtained at seven locations from the labrador sea to the drake passage despite subpicomolar concentrations in seawater a precision of the hf isotopic measurements of 03 epsilon hf units was achieved an overall epsilon hf range between 3 1 in the labrador sea and 4 4 in antarctic bottom water was determined the distribution of which broadly reflects continental weathering inputs within particular water column profiles significant differences of up to 4 epsilon hf units occur combined with nd isotope data of the same samples it is evident that the hf isotopic composition of seawater is too radiogenic for a given nd isotopic composition and that the largest difference between expected and measured hf isotopic compositions in seawater occurs near the oldest continental crust in the labrador sea this corroborates the previous proposition which was mainly based on ferromanganese crust data that the hf isotopic composition of seawater is controlled by incongruent weathering of continental crust and possibly to some extent by hydrothermal contributions hafnium concentrations in the ocean do not increase along the deep ocean conveyer indicating an oceanic residence time of only a few hundred years which is significantly shorter than previously assumed the hf isotopic composition of past seawater can therefore serve as a proxy for short distance basin scale mixing processes and the regime and intensity of nearby continental weathering processes c 2009 elsevier b v all rights reserved

origin of freshwater and polynya water in the arctic ocean halocline in summer 2007 extremely low summer sea ice coverage in the arctic ocean in 2007 allowed extensive sampling and a wide quasi synoptic hydrographic and 18o dataset could be collected in the eurasian basin and the makarov basin up to the alpha ridge and the east siberian continental margin with the aim of determining the origin of freshwater in the halocline fractions of river water and sea ice meltwater in the upper 150 m were quantified by a combination of salinity and 18o in the eurasian basin two methods applying the preformed phosphate concentration po and the nitrate to phosphate ratio n p were compared to further differentiate the marine fraction into atlantic and pacific derived contributions while po based assessments systematically underestimate the contribution of pacific derived waters n p based calculations overestimate pacific derived waters within the transpolar drift due to denitrification in bottom sediments at the laptev sea continental margin within the eurasian basin a west to east oriented front between net melting and production of sea ice is observed outside the atlantic regime dominated by net sea ice melting a pronounced layer influenced by brines released during sea ice formation is present at about 30 to 50 m water depth with a maximum over the lomonosov ridge the geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the transpolar drift the ratio of sea ice derived brine influence and river water is roughly constant within each layer of the arctic ocean halocline the correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea ice formation within the arctic ocean over the open ocean or in polynyas at the continental slope where relatively small amounts of river water are found sea ice formation results in a linear correlation between brine influence and river water at salinities of about 32 to 34 in coastal polynyas in the shallow regions of the laptev sea and southern kara sea sea ice formation transports river water into the shelf s bottom layer due to the close proximity to the river mouths this process therefore results in waters that form a second linear correlation between brine influence and river water at salinities of about 30 to 32 our study indicates which layers of the arctic ocean halocline are primarily influenced by sea ice formation in coastal polynyas and which layers are primarily influenced by sea ice formation over the open ocean accordingly we use the ratio of sea ice derived brine influence and river water to link the maximum in brine influence within the transpolar drift with a pulse of shelf waters from the laptev sea that was likely released in summer 2005

neodymium isotopes in seawater from the barents sea and fram strait arctic atlantic gateways abstract the neodymium concentration c nd and isotopic composition e nd in seawater have been determined in the water column at five sites in the barents sea fram strait area where most of the water exchange between the arctic ocean and the north atlantic takes place in the main arctic ocean inflow branch across the barents sea the concentration and isotopic composition c nd 15 5 pmol kg and e nd 10 8 are similar to those reported for the northeastern nordic seas which is consistent with this region being a source area for the arctic inflow due to the addition of nd from svalbard shelf sediments the c nd in the surface waters above 150 m in the fram strait inflow branch is higher by a factor of 2 and the e nd is shifted to lower values 11 8 in the stratified nansen basin where cold low salinity water overlies warmer atlantic water the c nd and e nd do not vary with the vertical temperature salinity structure but are essentially constant and similar to those of the atlantic inflow throughout the entire water column down to 3700 m depth which indicates that the nd is to a large extent of atlantic origin compared to the atlantic inflow water the nd in the major arctic ocean outflow the fram strait show higher c nd in the surface waters above 150 m and a higher e nd 9 8 throughout the entire water column down to 1300 m depth sources for the more radiogenic nd isotopic composition in deep water of the fram strait outflow most likely involve boundary exchange with sediments on the shelf and slope as the water passes along the canadian archipelago river water is a possible source in the surface water but it also seems likely that pacific water nd modified by interactions on the shelf is an important component in the fram strait surface outflow changes in the relative proportions of inflow of river water and flow of pacific water through the arctic ocean could thus influence the isotopic composition of nd in the north atlantic

wind and buoyancy induced transport of the norwegian coastal current in the barents sea 1 the focus of this study is on the fluxes and forcing of the norwegian coastal current ncc at the entrance to the barents sea the structure and dynamics of the ncc which consists of a slope branch and an offshore branch are investigated using 1 a recent 1 year full depth current meter record in the core of the slope region 2 repeated hydrographic data at an inshore monitoring station 3 broader regional hydrographic surveys and 4 atmospheric reanalysis data the total fluxes are estimated to 1 8 sv for volume and 26 msv for freshwater relative to a reference salinity of 34 8 with the largest contributions from baroclinic offshore branch the heat flux calculated for the slope branch only is 34 tw these estimates are higher compared to earlier estimates but are based on more comprehensive data the major mode of variability in the slope branch is consistent with a continental shelf wave on time scales in the range of 3 16 days forced by the along coast component of the wind stress maximum along slope currents during fall winter corresponding to the stronger wind forcing during these seasons suggest that the observed seasonality in the ncc can be attributed to a similar mechanism

water mass transformation in the barents sea inferred from radiogenic neodymium isotopes rare earth elements and stable oxygen isotopes abstract nearly half the inflow of warm and saline atlantic water aw to the arctic ocean is substantially cooled and freshened in the barents sea which is therefore considered a key region for water mass transformation in the arctic mediterranean am numerous studies have focused on this transformation and the increasing influence of aw on arctic climate and biodiversity yet geochemical investigations of these processes have been scarce using the first comprehensive data set of the distributions of dissolved radiogenic neodymium nd isotopes expressed as nd rare earth elements ree and stable oxygen isotope 18o compositions from this region we are able to constrain the transport and transformation of aw in the barents sea and to investigate which processes change the chemical composition of the water masses beyond what is expected from circulation and mixing inflowing aw and norwegian coastal water ncw both exhibit distinctly unradiogenic nd signatures of 12 4 and 14 5 respectively whereas cold and dense polar water pw has considerably more radiogenic nd signatures reaching up to 8 1 locally formed barents sea atlantic water bsaw and barents sea arctic atlantic water bsaaw are encountered in the northeastern barents sea and have intermediate nd values resulting from admixture of pw containing small amounts of riverine freshwater from the ob this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

south pacific dissolved nd isotope compositions and rare earth element distributions water mass mixing versus biogeochemical cycling despite its enormous extent and importance for global climate the south pacific has been poorly investigated in comparison to other regions with respect to chemical oceanography here we present the first detailed analysis of dissolved radiogenic nd isotopes end and rare earth elements rees in intermediate and deep waters of the mid latitude 40 s south pacific along a meridional transect between south america and new zealand the goal of our study is to gain better insight into the distribution and mixing of water masses in the south pacific and to evaluate the validity of nd isotopes as a water mass tracer in this remote region of the ocean the results demonstrate that biogeochemical cycling scavenging processes in the eastern equatorial pacific and release of lrees from the sediment clearly influence the distribution of the dissolved ree concentrations at certain locations nevertheless the nd isotope signatures clearly trace water masses including aaiw antarctic intermediate water average end 8 2 0 3 lcdw lower circumpolar deep water average end 8 3 0 3 npdw north pacific deep water average end 5 9 0 3 and the remnants of nadw north atlantic deep water average end 9 7 0 3 filtered water samples taken from the sediment water interface under the deep western boundary current off new zealand suggest that boundary exchange processes are limited at this location and highlight the spatial and temporal variability of this process these data will serve as a basis for the paleoceanographic application of nd isotopes in the south pacific

submarine groundwater discharge is an important net source of light and middle rees to coastal waters of the indian river lagoon florida usa abstract porewater i e groundwater samples were collected from multi level piezometers across the freshwater saltwater seepage face within the indian river lagoon subterranean estuary along florida s usa atlantic coast for analysis of the rare earth elements ree surface water samples for ree analysis were also collected from the water column of the indian river lagoon as well as two local rivers eau gallie river crane creek that flow into the lagoon within the study area concentrations of rees in porewaters from the subterranean estuary are 10 100 times higher than typical seawater values e g nd ranges from 217 to 2409 pmol kg 1 with submarine groundwater discharge sgd at the freshwater saltwater seepage face exhibiting the highest ree concentrations the elevated ree concentrations for sgd at the seepage face are too high to be the result of simple binary mixing between a seawater end member and local terrestrial sgd instead the high ree concentrations indicate that geochemical reactions occurring within the subterranean estuary contribute substantially to the ree cycle a simple mass balance model is used to investigate the cycling of rees in the indian river lagoon and its underlying subterranean estuary mass balance modeling reveals that the indian river lagoon is approximately at steady state with respect to the ree fluxes into and out of the lagoon however the subterranean estuary is not at steady state with respect to the ree fluxes specifically the model suggests that the sgd nd flux for example exported from the subterranean estuary to the overlying lagoon waters exceeds the combined input to the subterranean estuary from terrestrial sgd and recirculating marine sgd by on average 100 mmol day 1 the mass balance model also reveals that the subterranean estuary is a net source of light rees lree and middle rees mree to the overlying lagoon waters but acts as a sink for the heavy rees hree geochemical modeling and statistical analysis further suggests that this fractionation occurs in part due to the coupling between ree cycling and iron redox cycling within the indian river lagoon subterranean estuary the net sgd flux of nd to the indian river lagoon is 7 fold larger than the local effective river flux to these coastal waters this previously unrecognized source of nd to the coastal ocean could conceivably be important to the global oceanic nd budget and help to resolve the oceanic nd paradox by accounting for a substantial fraction of the hypothesized missing nd flux to the ocean

the sedimentary flux of dissolved rare earth elements to the ocean abstract we determined pore fluid rare earth element ree concentrations in near surface sediments retrieved from the continental margin off oregon and california usa these sites represent shelf to slope settings which lie above within and below the oxygen minimum zone of the northeast pacific the sediments are characterized by varying degrees of net iron reduction with pore fluids from the shelf sites being generally ferruginous and the slope sediments having less pronounced iron reduction zones that originate deeper in the sediment package ree concentrations show maxima in shallow upper 2 10 cm subsurface pore fluids across all sites with concentrations that rise more than two orders of magnitude higher than seawater these pore fluid enrichments highlight the importance of a sedimentary source of rees to the ocean s water column here we use our measurements to estimate the diffusive flux of nd out of ocean sediments resulting in a global flux between 18 and 110 10 6 mol nd yr 1 while we do assume that our pore fluid profiles as well as the very limited data previously published are representative of a wide array of ocean environments this calculated flux can account for the modeled missing nd source flux 76 10 6 mol nd yr 1 in global budgets arsouze et al 2009 pore fluid normalized ree patterns show distinct variation in the middle ree and heavy ree enrichments with sediment depth and amongst sites these patterns show that the heavy ree enrichment of pore fluids at our deep slope site 3000 m water depth is closest to the heavy ree enrichment of seawater this observation supports the view that ree cycling within the upper ten centimeters of deep sea marine sediments as opposed to shallower continental shelf and slope sediments plays a significant role in controlling the integrated global ree flux from the pore fluids and consequently the broad scale ree pattern in seawater

the distribution of neodymium isotopes in arctic ocean basins nd concentration and isotope data have been obtained for the canada amundsen and makarov basins of the arctic ocean a pattern of high nd concentrations up to 58 pm at shallow depths is seen throughout the arctic and is distinct from that generally seen in other oceans where surface waters are relatively depleted a range of isotopic variations across the arctic and within individual depth profiles reflects the different sources of waters the dominant source of water and so nd is the atlantic ocean with lesser contributions from the pacific and arctic rivers radiogenic isotope nd signatures up to epsilon nd 6 5 can be traced in pacific water flowing into the canada basin waters from rivers draining older terrains provide very unradiogenic nd down to epsilon nd 14 2 that can be traced in surface waters across much of the eurasian basin a distinct feature of the arctic is the general influence of the shelves on the nd concentrations of waters flowing into the basins either from the pacific across the chukchi sea or from across the extensive siberian shelves water shelf interaction results in an increase in nd concentration without significant changes in salinity in essentially all waters in the arctic through processes that are not yet well understood in estuarine regions other processes modify the nd signal of freshwater components supplied into the arctic basin and possibly also contribute to sedimentary nd that may be subsequently involved in sediment water interactions mixing relationships indicate that in estuaries nd is removed from major river waters to different degrees deep waters in the arctic are higher in nd than the inflowing atlantic waters apparently through enrichments of waters on the shelves that are involved in ventilating the deep basins these enrichments generally have not resulted in major shifts in the isotopic compositions of the deep waters in the makarov basin epsilon nd similar to 10 5 but have created distinctive nd isotope signatures that were found near the margin of the canada basin with epsilon nd similar to 9 0 the deep waters of the amundsen basin are also distinct from the atlantic waters with epsilon nd 12 3 indicating that there has been limited inflow from the adjacent makarov basin through the lomonosov ridge c 2009 elsevier ltd all rights reserved

importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern indian ocean vertical profiles of dissolved rare earth elements rees were obtained in the bay of bengal and the andaman sea the ree concentrations at various depths in the bay of bengal are the highest in the indian ocean this is attributable ultimately to the large outflow of the ganges brahmaputra and irrawaddy rivers but the dissolved ree flux to surface waters alone cannot explain the large and near constant ree enrichment throughout the entire water column the underlying fan sediments serve as not a source but a sink for dissolved ree iii s absence of excess 228ra in the deep waters suggests that lateral input of dissolved rees from slope sediments is also small in these regions partial 0 3 dissolution of detrital particles which are carried by the rivers and lateral surface currents and subsequently settle through the water column appears to be a predominant source for the dissolved rees vertical profiles showing an almost linear increase with depth are common features for the light and middle rees everywhere but their concentration levels are variable from basin to basin and from element to element this suggests that their oceanic distributions respond quickly to the variation of particle flux and its ree composition through reversible exchange equilibrium with suspended and sinking particles much like the case for th the relative importance of the vertical geochemical processes of reversible scavenging over the horizontal basin scale ocean circulation with passive regeneration like nutrients decreases systematically from the light to the heavy rees using a model the mean oceanic residence times of rees in the bay of bengal are estimated to range from 37 years for ce to 140 1510 years for the strictly trivalent rees in the deep water of the andaman sea isolated from the bay of bengal by the andaman nicobar ridge maximum sill depth of 1800 m the ree concentrations are almost uniform presumably due to rapid vertical mixing the ree iii concentrations are similar to that of 1250 m depth water in the bay of bengal consistent with other oceanographic properties however the ree composition of the deep water appears to be altered slightly by preferential scavenging of the light ree iii at the bottom boundary of the basin

barents sea multidecadal variability 1 we present area averaged time series of temperature for the 100 150 m depth layer of the barents sea from 1900 through 2006 this record is dominated by multidecadal variability on the order of 4 c which is correlated with the atlantic multidecadal oscillation index

the norwegian atlantic current in the lofoten basin inferred from hydrological and tracer data 129i and its interaction with the norwegian coastal current 1 from three hydrological sections taken across the lofoten basin in may 2000 we estimated geostrophic transports of 7 2 sv sverdrup 106 m3 s 1 for the norwegian atlantic current nac and its division between northern 4 8 sv and eastern 2 4 sv branches from 129i 127i concentration ratio measurements and transport estimations we calculated 129i mass flux across the three sections it appears that in the lofoten basin a 129i tracer laden norwegian coastal current ncc is transporting northward 55 kg y of 129i assuming a volume flux of 0 7 sv b the estimated mass fluxes of 129i by the nac and the ncc are comparable c the total mass flux of 129i by the nac and ncc accounts only for about 1 3 of the 129i annual discharge 350 kg y from two reprocessing plants based in france and uk if these measurements are representative of annual mean it suggests an important transfer of 129i outside the nac ncc system

pacific freshwater river water and sea ice meltwater across arctic ocean basins results from the 2005 beringia expedition 1 pacific water sea ice meltwater and river water are the primary sources of freshwater in the arctic ocean we have determined their relative fractions on a transect across the arctic ocean section 2005 expedition onboard ib oden which took place from 21 august to 23 september 2005 the transect began north of alaska continued through the central canada basin to the alpha ridge and into the makarov basin and ended in amundsen basin pacific freshwater and river water were the major sources of freshwater throughout the central canada basin and into makarov basin with river water fractions sometimes considerably higher than pacific water in the top 50 m pacific freshwater extended to depths of about 200 m pacific water found over the alpha ridge and in the amundsen basin is suggested to have been transported there in the transpolar drift the inventories of pacific freshwater and river water were roughly constant along the section through most of the canada and makarov basins river water fractions were greater than those of pacific freshwater in the amundsen basin sea ice meltwater fractions were negative reflecting net ice formation or near zero throughout most of the section a comparison of freshwater inventories with those at stations occupied during expeditions in 1991 1994 and 1996 indicated an increase in river water inventories in the makarov and amundsen basins on the eurasian side of the arctic ocean

water mass distribution and polar front structure in the western barents sea the water mass distribution in the western barents sea the thermohaline structure of the western barents sea polar front and the local formation of a dense water mass are described on the basis of an analysis of historical hydrographic data this study concentrated on the frontal region between bjornoya and hopen island where arctic water is found on the spitsbergen bank and atlantic water in the bear island trough and hopen trench the distributions of atlantic and arctic waters in relation to topography were consistent with the hypothesis that the location of the polar front is fixed at about the 250 m isobath by the barotropic circulation of atlantic water within the bear island trough and hopen trench in winter vertical gradients of temperature and salinity were weak throughout the frontal region consistent with a barotropic topographically controlled front in summer vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh warm surface water produced by melting ice the topographic control of thermohaline properties at the surface was disrupted by the meltwater pool and the meltwater contributed to water mass modification in the frontal region the following seasonal cycle of water mass formation was hypothesized summer heating melts the sea ice on the spitsbergen bank and produces the surface meltwater pool this meltwater not only increases vertical thermohaline gradients on the bank but also crosses the front and freshens the surface layer throughout the western barents sea subsequent winter cooling which creates ice over the bank also forms dense water in the bear island trough and hopen trench by convective mixing of atlantic water and the overlying meltwater

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

recirculation of atlantic water in the western barents sea 1 in this article the atlantic inflow with the north cape current to the barents sea and potential recirculation of this water in the bear island trough is investigated this is resolved by combining continuous current meter and repeated hydrographic section data in the barents sea opening the estimated annual mean net fluxes when excluding the contribution from the norwegian coastal current are 1 1 sv and 39 tw estimated relative to a reference temperature of 0 c the estimated heat flux associated with the outflow in the bear island trough is relatively large 12 tw long term current meter records do not show a close relationship between variations in the inflow and the outflow one year low pass filtered variations in temperature and salinity of the outflowing waters in the bear island trough are positively correlated with variations of the inflowing atlantic water with a lag of about seven months on the basis of a simple mixing model the outflow water consists of about 80 atlantic water that is additionally cooled by 2 0 2 5 c by heat loss to the atmosphere by considering the relative weak mean currents in this region it can be inferred that the fraction of the atlantic water that recirculates follows a relatively short pathway in the bear island trough before returning to the norwegian sea

neodymium isotopic composition and rare earth element concentrations in the deep and intermediate nordic seas constraints on the iceland scotland overflow water signature neodymium isotopic composition and rare earth element concentrations were measured in seawater samples from eleven stations in the nordic seas these data allow us to study how the iceland scotland overflow water isow acquires its neodymium signature in the modern ocean the waters overflowing the faroe shetland channel are characterized by nd 8 2 0 6 in good agreement with the only other data point published 19 years ago in the greenland and iceland seas the water masses leading to the formation of the isow display lower neodymium isotopic composition with nd around 11 and 9 respectively since no water masses in the nordic seas are characterized by nd 8 the radiogenic signature of the isow likely reflects inputs from the highly radiogenic norwegian basin basaltic margins jan mayen iceland faroe with nd 7 in addition to the neodymium isotopic composition the rare earth element patterns suggest that these inputs occur via the remobilization which includes resuspension and dissolution of sediments deposited on the margins whereas the neodymium isotopic composition behaves conservatively in the oceans in the absence of lithogenic inputs and can be used as a water mass tracer these results emphasize the role of interactions between sediments deposited on margins and seawater in the acquisition of the neodymium isotopic composition of water masses these results should allow a better use of this parameter to trace the present and the past circulation in the north atlantic

velocity field of the western entrance to the barents sea 1 by the use of 4 year long records from moored current meters between 71 30 n and 73 30 n of the western entrance to the barents sea the velocity field of the atlantic inflow is examined the mean velocity field shows the atlantic inflow as a wide core that occupies most of this section but the general picture is a velocity field that is dominated by large and frequent fluctuations the key parameter that to a large degree determines the spatial distribution of the velocity field is sea level changes within the section that are induced by the local wind field the main process is the ekman transport through its ability to accumulate water thereby creating strong gradients of barotropic pressure and associated currents southwesterly winds along the norwegian coast and southeasterly winds farther north will in general create wide inflows while northerly winds will result in wide outflows these flow regimes may be persistent for up to 2 3 weeks and are related to the relative strength and lateral extension of the icelandic low and the arctic high although the alignment of the local isobars must be considered in order to be able to describe the details of the flow

retrieving near surface soil moisture from radarsat sar data on the basis of six radarsat synthetic aperature radar sar images acquired over the paddle river basin alberta and 1350 field soil moisture data collected from nine selected sites of the basin in the same days this study demonstrated the feasibility of retrieving near surface soil moisture 5 10 cm depth from radarsat sar data between two retrieval algorithms a linear regression and the theoretical integral equation model iem of fung et al 1992 the results indicate that iem performed consistently better than the regression model however the performance of both models generally deteriorates when the basin is nearly saturated which is the case for september 10 and 27 1996 with a basin saturation level of 82 and 75 respectively with respect to radarsat s configuration and iem s surface parameters it is found that radar backscattering 0 is highly sensitive to the surface rms height especially for a relatively smooth surface and a gaussian correlation function from the semivariogram of measured soil moisture and 0 it is found that the homogeneity assumption of spatial interpolation as a function of distance lag breaks down only at a distance lag of about 200 275 m apparently spatial interpolation methods based on this assumption can only interpolate soil moisture meaningfully for single land use plots of several hundred meters in size

retrieving soil moisture over bare soil from ers 1 synthetic aperture radar data sensitivity analysis based on a theoretical surface scattering model and field data in order to assess the retrieval of soil moisture from ers 1 european remote sensing satellite synthetic aperture radar sar data an inversion procedure based oft the integral equation model iem fung et al 1992 is developed first the iem is used to analyze the sensitivity of radar echoes in terms of the backscattering coefficient 0 to the surface parameters roughness and dielectric constant under ers 1 sar configuration results obtained for random rough bare soil fields show that the effect of surface roughness is very strong particularly in the case of smooth surfaces and that the sensitivity of 0 to dielectric constant is independent of the radar configuration and the roughness conditions this means that the range of variation of backscattering with respect to the dielectric constant variation of dry to wet soil remains the same about 5 db for any roughness condition and radar configuration the possibility of applying the inversion procedure to retrieve soil moisture is investigated using a set of data collected in a test site situated near naples italy during the seie synthetic aperture radar experiment sesar campaign november 1993 simultaneous with ers 1 overpasses dielectric constant and roughness measurements were taken over two flat bare fields from this analysis it is found that the inversion of backscattering from ers 1 sar into soil moisture is not reliable without accurate information on roughness if the surface is smooth in this case it is observed that the sensitivity to the roughness parameters is much higher than the sensitivity to dielectric constant so that even a small error in the measurement of this parameter can affect the retrieved value of soil moisture significantly the inversion procedure provides more reliable soil moisture estimates when surfaces rougher than those analyzed in the field experiment are considered

online preconcentration icp ms analysis of rare earth elements in seawater the rare earth elements rees with their systematically varying properties are powerful tracers of continental inputs particle scavenging intensity and the oxidation state of seawater however their generally low pmol kg concentrations in seawater and fractionation potential during chemical treatment makes them difficult to measure here we report a technique using an automated preconcentration system which efficiently separates seawater matrix elements and elutes the preconcentrated sample directly into the spray chamber of an icp ms instrument the commercially available seafast system elemental scientific inc makes use of a resin with ethylenediaminetriacetic acid and iminodiacetic acid functional groups to preconcentrate rees and other metals while anions and alkali and alkaline earth cations are washed out repeated measurements of seawater from 2000 m water depth in the southern ocean allows the external precision 2 of the technique to be estimated at 23 for all rees and 15 for most comparison of nd concentrations with isotope dilution measurements for 69 samples demonstrates that the two techniques generally agree within 15 accuracy was found to be good for all rees by using a five point standard addition analysis of one sample and comparing measurements of mine water reference materials diluted with a nacl matrix with recommended values in the literature this makes the online preconcentration icp ms technique advantageous for the minimal sample preparation required and the relatively small sample volume consumed 7 ml thus enabling large data sets for the rees in seawater to be rapidly acquired

soil moisture mapping over the central part of the tibetan plateau using a series of asar ws images abstract the wide swath ws and global monitoring gm modes of the advanced synthetic aperture radar asar provide for monitoring purposes a good compromise between the spatial coverage spatial resolution and revisit time similar imaging modes will be a part of the sentinel 1 sar sensing system a consequence of operating at the wider swath is however the rather large view angle range about 16 43 which needs to be corrected for if biophysical variables are to be retrieved from these data sets a soil moisture retrieval algorithm based on the integral equation method iem scattering model is presented that explicitly simulates the backscatter as a function of the incidence angle instead of normalizing this algorithm is applied to 150 asar ws scenes collected from april 2005 to september 2007 over the central part of the tibetan plateau we selected three of these images covering the study area at different view angles during the winter season for the iem roughness derivation subsequently soil moisture is retrieved from the entire o data sets via inversion of the iem model with the obtained roughness parameters as input the retrievals are validated against soil moisture measured from july 2006 to september 2007 at four sites representative for a 10 10 km 2 area further the uncertainties following from assumptions made for the development of the algorithm are also quantified

modelling nd isotopes with a coarse resolution ocean circulation model sensitivities to model parameters and source sink distributions the neodymium nd isotopic composition nd of seawater is a quasi conservative tracer of water mass mixing and is assumed to hold great potential for paleoceanographic studies here we present a comprehensive approach for the simulation of the two neodymium isotopes 143nd and 144nd using the bern3d model a low resolution ocean model the high computational efficiency of the bern3d model in conjunction with our comprehensive approach allows us to systematically and extensively explore the sensitivity of nd concentrations and nd to the parametrisation of sources and sinks previous studies have been restricted in doing so either by the chosen approach or by computational costs our study thus presents the most comprehensive survey of the marine nd cycle to date our model simulates both nd concentrations as well as nd in good agreement with observations nd covaries with salinity thus underlining its potential as a water mass proxy results confirm that the continental margins are required as a nd source to simulate nd concentrations and nd consistent with observations we estimate this source to be slightly smaller than reported in previous studies and find that above a certain magnitude its magnitude affects nd only to a small extent on the other hand the parametrisation of the reversible scavenging considerably affects the ability of the model to simulate both nd concentrations and nd furthermore despite their small contribution we find dust and rivers to be important components of the nd cycle in additional experiments we systematically varied the diapycnal diffusivity as well as the atlantic to pacific freshwater flux to explore the sensitivity of nd concentrations and its isotopic signature to the strength and geometry of the overturning circulation these experiments reveal that nd concentrations and nd are comparatively little affected by variations in diapycnal diffusivity and the atlantic to pacific freshwater flux in contrast an adequate representation of nd sources and sinks is crucial to simulate nd concentrations and nd consistent with observations the good agreement of our results with observations paves the way for the evaluation of the paleoceanographic potential of nd in further model studies

neodymium budget in the modern ocean and paleo oceanographic implications the oceanic nd budget is calculated using a steady state 10 box model and a compilation of field data this is the first attempt to propose consistent estimates of the nd fluxes entering the ocean as well as indicating possible nd sources and the proportion of nd fluxes exchanged between dissolved and particulate fractions with presently available nd data the best estimates give a total nd influx of 9 x 10 9 g yr which leads to an oceanic nd residence time of 500 years from modeling tests we suggest that the authigenic nd scavenged by particulates is 100 remineralized in the deep ocean the total exchanged nd flux may be as high as 2 x 10 10 g yr the epsilon nd 0 values of the influxes are 22 11 1 and 4 for the north atlantic surface atlantic north pacific and surface indo pacific regions respectively atmospheric and riverine nd fluxes are insufficient to explain the magnitude and regional variability of calculated nd influxes and epsilon nd 0 we propose continental margins as an additional source supplying nd to the ocean using the model calibrated for nd we examine the sensitivity of deep water epsilon nd 0 to variations of nd inputs to the ocean deep water nd concentrations and epsilon nd 0 vary with the changes in nd influxes and their epsilon nd 0 as nd sources to the ocean may change during glacial interglacial periods the epsilon nd 0 shifts recorded in ferromanganese nodules and crusts do not necessarily reflect changes in paleoceanic circulation the effects of continental erosion should be considered in reconstructing patterns of ocean circulation using nd isotopes

separating biogeochemical cycling of neodymium from water mass mixing in the eastern north atlantic abstract the radiogenic neodymium nd isotope ratio 143nd 144nd expressed in e nd is being used as a tracer in paleo and modern ocean circulation however the mechanisms controlling input distribution and internal cycling are far from understood for example globally nd concentration nd commonly follows patterns of nutrient tracers generally increasing with depth below the thermocline while e nd tends to reflect the water masses which has often been referred to as the nd paradox here we present dissolved nd isotopes and concentrations at unprecedented vertical and spatial resolution from the eastern part of the us geotraces north atlantic zonal transect gulf of cadiz mauritanian shelf cape verde islands the nd of all samples ranges from 12 3 to 36 7 pmol kg with lowest nd usually found within the layer of highest chlorophyll a levels chl max suggesting removal through scavenging the nd isotope compositions range between e nd 13 4 and 9 9 with lower values at the surface within the extension of the saharan dust plume and a benthic nepheloid layer bnl less negative values are found in oligotrophic surface waters mediterranean outflow water mow and near the cape verde islands overall water mass mixing derived from e nd is best visible at the strait of gibraltar where mow enters the atlantic ocean most of the sub thermocline e nd varies within a small range with poor water mass distinction due to the dominance of north atlantic deep water high surface nd associated with more negative e nd is interpreted to be the result of dust deposition and dissolution local nd maxima with no apparent change in e nd compared to ambient seawater observed within a zone of minimum oxygen concentration omz at 500 m depth off mauritania suggest minor input of lithogenic nd but a rather high contribution through desorption of previously scavenged nd that is saharan dust in this area has only a minor influence on the isotope composition of water below the uppermost surface layer the low e nd values and elevated nd within the bnl on the other hand indicate release from detrital material our new high resolution dataset gives valuable insights into the nd distribution near continental margins influenced by high atmospheric inputs and changing oxygen conditions we show how vertical and lateral processes overlap to produce the observed nd distribution bringing us forward in understanding the nd paradox

regional seismic hazard posed by the mentawai segment of the sumatran megathrust several lines of evidence have indicated that the mentawai segment of the sumatran megathrust is very likely to rupture within the next few decades the present study is to investigate seismic hazard and risk levels at major cities in sumatra java singapore and the malay peninsula caused by the potential giant earthquakes three scenarios are considered the first one is an mw 8 6 earthquake rupturing the 280 km segment that has been locked since 1797 in the second scenario rupture oc curs along a 600 km segment covering the combined rupture areas of the 1797 and 1833 historical events producing an mw 9 0 earthquake and the third scenario has the same rupture area as the second scenario but with doubled slip amplitude resulting in an mw 9 2 earthquake simulation results indicate that ground motions produced by the hypothetical scenarios are strong enough to cause yielding to medium and high rise buildings in many major cities in sumatra it is vital to ensure that the overall strength stiffness and integrity of the structures are maintained throughout the entire duration of shaking however the ductile detailing in current practice is formulated based on an assumption that ground motions would last from 20 to 40 sec this has not been tested for longer durations of 3 5 min expected from giant earthquakes in singapore and kuala lumpur only medium and high rise buildings especially those located on soft soil sites are at risk given that seismic design has not been required in either city and thus the resulting structures are relatively brittle it is crucial to inves tigate their performance under moderate amplitude long duration ground motions the present study also points out that shifting the response spectrum toward a longer period range becomes significant for sites located far from potential seismic sources which should be carefully considered in formulation of future seismic codes