on the relationship between southern ocean overturning and acc transport the eddy field in the southern ocean offsets the impact of strengthening winds on the meridional overturning circulation and antarctic circumpolar current acc transport there is widespread belief that the sensitivities of the overturning and acc transport are dynamically linked with limitation of the acc transport response implying limitation of the overturning response here an idealized numerical model is employed to investigate the response of the large scale circulation in the southern ocean to wind stress perturbations at eddy permitting to eddy resolving scales significant differences are observed between the sensitivities and the resolution dependence of the overturning and acc transport indicating that they are controlled by distinct dynamical mechanisms the modeled overturning is significantly more sensitive to change than the acc transport with the possible implication that the southern ocean overturning may increase in response to future wind stress changes without measurable changes in the acc transport it is hypothesized that the dynamical distinction between the zonal and meridional transport sensitivities is derived from the depth dependence of the extent of cancellation between the ekman and eddy induced transports

numerical modeling of flow processes over gravelly surfaces using structured grids and a numerical porosity treatment this article describes the development and validation of a method for representing the complex surface topography of gravel bed rivers in high resolution three dimensional computational fluid dynamic models this is based on a regular structured grid and the application of a porosity modification to the mass conservation equation in which fully blocked cells are assigned a porosity of zero fully unblocked cells are assigned a porosity of one and partly blocked cells are assigned a porosity of between 0 and 1 according to the percentage of the cell volume that is blocked the model retains an equilibrium wall function and an rng type two equation turbulence model the model is combined with a 0 002 m resolution digital elevation model of a flume based water worked gravel bed surface acquired using two media digital photogrammetry and with surface elevations that are precise to 0 001 m the model is validated by comparison with velocity data measured using a three component acoustic doppler velocimeter adv model validation demonstrates a significantly improved level of agreement than in previous studies notably in relation to shear at the bed although the resolution of model predictions was significantly higher than the adv measurements making model assessment in the presence of strong shear especially difficult a series of simulations to assess model sensitivity to bed topographic and roughness representation were undertaken these demonstrated inherent limitations in the prediction of 3 d flow fields in gravel bed rivers without high resolution topographic representation they also showed that model predictions of downstream flux were more sensitive to topographic smoothing that to changes in the roughness parameterization reflecting the importance of both mass conservation i e blockage and momentum conservation effects at the grain and bed form scale model predictions allowed visualization of the structure of form flow interactions at high resolution in particular the most protruding bed particles exerted a critical control on the turbulent kinetic energy maxima typically observed at about 20 of the flow depth above the bed

terrain analysis for urban stormwater modelling a geographic information system arc info is used to develop a model of the urban environment for storm drainage analysis the drainage system is divided into surface terrain stormwater intakes and the drainage network the intakes hydrologically connect surface and subsurface flow elements the drainage network consists of both man made structures pipes and channels and overland flow paths that connect them the land surface terrain is defined by a triangulated irregular network tin which is used to determine necessary parameters for design flow calculations each of the three basic elements of the urban terrain representation inlets defined as points drainage network defined as lines and surface terrain defined as tins has its own specific data structure the three databases are fully integrated and the stored information is used to determine whether inlets and pipes can convey 10 and 25 year design flows using the rational method an intelligent network builder is developed using the nexpert object expert system shell to test for completeness of databases and flow paths prior to hydrological computations if necesssary the intelligent network builder starts up arc info procedures that fill in missing links in the drainage network and missing flow properties of its components an example application is made to the drainage system of a section of city of asheville north carolina

determination of recent 238u 234u and 230th mobility in granitic rocks application of a natural analogue to the high level waste repository environment abstract the isotope activity ratios 234u 238u and 230th 234u have been investigated in drill core samples up to 1300 m depth in three granitoids from australia to identify the nature of possible recent 1 0 which has generated excess 230th these enriched ground waters do not appear to have penetrated below 530 m depth and 230th excess indicates bulk loss of u the observed disequilibria indicate that significant radionuclide mobilisation has occurred in these rocks during the recent past

review of the modelling of radionuclide transport from u series disequilibria and of its use in assessing the safe disposal of nuclear waste in crystalline rock abstract u series disequilibia from crystalline rocks and u deposits have been used to estimate the timing of hydrogeological events for u and ra mobility and to model the transport rates of u and ra both with some sucess unfortunately activity ratio data alone are not unique to a given process or model and it is shown how inappropriate choice of the model can have quite diverse consequences for interpretation of the data information from other sources is needed to help minimise these non uniqueness problems but as yet the state of methodology is unadequate to assess completely the validity of the models in particular the rate of deposition of u in fractures seems highly dependent upon the availability of trivalent fe and other low temperature minerals whose rates of formation are largely unknown this review reinforces the need to assess closely the suggestion that chemisorption is an effective retardant of fracture borne borne repository source radionuclides

comparison of 226ra 238u and 228th 228ra disequilibrium with weathering indices in beach sand sediments from greece weathering indices can be used to quantify weathering of rocks at various stages of weathering processes and provide a better understanding of element mobility during weathering various weathering indices have been proposed in the literature worldwide in the present work radioactive secular disequilibrium has been used to determine weathering extent thirty seven samples from kavala and thirty from sithonia beach sands all of them being the weathering products of the local granitic plutons are studied for their secular disequilibrium in both 238u and 232th series 226ra 238u and 228ra 228th respectively the results are compared to weathering indices already in use worldwide and suggest a consistent correlation with wip alkaline and alkaline earth element leaching and pwi silica leaching for the well and very well sorted sands and for the heavy minerals of kavala this study suggests that with an appropriate choice of the weathering index and samples both u series and weathering index can recover the extent of chemical weathering

separating the influence of projected changes in air temperature and wind on patterns of sea level change and ocean heat content we present ocean model sensitivity experiments aimed at separating the influence of the projected changes in the thermal near surface air temperature and wind near surface winds forcing on the patterns of sea level and ocean heat content in the north atlantic the distribution of sea level change is more due to the thermal forcing whereas it is more due to the wind forcing in the north pacific in the southern ocean the thermal and wind forcing have a comparable influence in the ocean adjacent to antarctica the thermal forcing leads to an inflow of warmer waters on the continental shelves which is somewhat attenuated by the wind forcing the structure of the vertically integrated heat uptake is set by different processes at low and high latitudes at low latitudes it is dominated by the heat transport convergence whereas at high latitudes it represents a small residual of changes in the surface flux and advection of heat the structure of the horizontally integrated heat content tendency is set by the increase of downward heat flux by the mean circulation and comparable decrease of upward heat flux by the subgrid scale processes the upward eddy heat flux decreases and increases by almost the same magnitude in response to respectively the thermal and wind forcing regionally the surface heat loss and deep convection weaken in the labrador sea but intensify in the greenland sea in the region of sea ice retreat the enhanced heat flux anomaly in the subpolar atlantic is mainly caused by the thermal forcing

radioactive disequilibria in mineralised fracture samples from two uranium occurrences in northern sweden abstract mineralised fractures from two uranium occurrences in northern sweden were examined mineralogically and isotopically to establish the presence or absence of radioactive equilibrium that may indicate recent rock water interaction processes based on the natural mobility of uranium i e during the last 0 5 ma the results show evidence of radioactive disequilibrium in six of the nine samples investigated disequilibria are attributable to solution to solid 234 u recoil gain weakly mineralised zones adjacent to the main mineralisation and solid to solution 234 u recoil loss moderate to highly mineralised zones the absence of significant 238 u loss in the samples emphasises the reducing conditions at the sampled depths

calibration of a two dimensional finite element flood flow model using satellite radar imagery the application of numerical models of free surface flow to fluvial flood prediction is currently hampered by the lack of distributed calibration and validation data we address this shortcoming by the use of satellite borne synthetic aperture radar imagery to map a flood on a 15 km reach of the river thames england a finite element numerical model of shallow water flow is constructed over the reach and analysis shows that floodplain friction is the dominant factor affecting inundation extent when compared to channel friction turbulence parameterization and downstream boundary conditions the area of the domain correctly classified by the model is maximized with the constraint of uniform floodplain friction 77 at maximum compared with 70 for a simple planar model of the water free surface a simple distributed calibration scheme is also tested with a minor improvement over the uniform parameterization

simple spatially distributed models for predicting flood inundation a review abstract in this paper we review recent progress in the use of reduced complexity models for predicting floodplain inundation we review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one dimensional shallow water equations we then review how such schemes can be applied in practice and consider issues of space discretization time discretization and model parameterisation before going on to consider model assessment procedures we show that a key advantage of reduced complexity codes is that they force modellers to think about the minimum process representation necessary to predict particular quantities and act as a check on any tendency to reductionism at the same time however the use compared to standard hydraulic codes of strong simplifying assumptions requires us to also address the question how simple can a model be and still be physically realistic we show that by making explicit this debate about acceptable levels of abstraction reduced complexity codes allow progress to be made in addressing a number of long standing debates in hydraulics

effect of topographic data geometric configuration and modeling approach on flood inundation mapping summary technological aspects of producing delivering and updating of flood hazard maps in the us have has gone through a revolutionary change through federal emergency management agency s map modernization program in addition the use of topographic information derived from light detection and ranging lidar is enabling creation of relatively more accurate flood inundation maps however lidar is not available for the entire united states even for areas where lidar data are available the effect of other factors such as cross section configuration in one dimensional 1d models mesh resolution in two dimensional models 2d representation of river bathymetry and modeling approach is not well studied or documented the objective of this paper is to address some of these issues by comparing newly developed flood inundation maps from lidar data to maps that are developed using different topography geometric description and modeling approach the methodology involves use of six topographic datasets with different horizontal resolutions vertical accuracies and bathymetry details each topographic dataset is used to create a flood inundation map for twelve different cross section configurations using 1d hec ras model and two mesh resolutions using 2d feswms model comparison of resulting maps for two study areas strouds creek in north carolina and brazos river in texas show that the flood inundation area reduces with improved horizontal resolution and vertical accuracy in the topographic data this reduction is further enhanced by incorporating river bathymetry in topography data overall the inundation extent predicted by feswms is smaller compared to prediction from hec ras for the study areas and that the variations in the flood inundation maps arising from different factors are smaller in feswms compared to hec ras

the role of vertical eddy flux in southern ocean heat uptake 1 the role of changing vertical eddy heat flux on southern ocean heat uptake is investigated in an idealized eddy permitting ocean model enhanced air sea heat flux drives deep reaching southern warming due to a reduction in the isopycnal meridional temperature gradient and therefore decreased upward eddy heat flux this mechanism is qualitatively similar in models with either permitted or parameterized eddies due to its dependence on the isopycnal temperature gradient rather than the dynamical response of the eddy field in contrast increased wind stress drives mid depth southern ocean cooling through an enhancement of the eddy field and resultant eddy heat divergence the transient cooling extends over multiple decades while the mean flow adjusts to balance the faster eddy response this wind driven cooling mechanism has not been captured by coarse resolution models with fixed eddy parameterizations and is a possible candidate for the recent cooling observed in the southern ocean

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

southern ocean eddy phenomenology mesoscale eddies are ubiquitous features in the southern ocean yet their phenomenology is not well quantified to tackle this task we use satellite observations of sea level anomalies and sea surface temperature sst as well as in situ temperature and salinity measurements from profiling floats over the period 1997 2010 we identified over a million mesoscale eddy instances and were able to track about 105 of them over 1 month or more the antarctic circumpolar current acc the boundary current systems and the regions where they interact are hot spots of eddy presence representing also the birth places and graveyards of most eddies these hot spots contrast strongly to areas shallower than about 2000 m where mesoscale eddies are essentially absent likely due to topographical steering anticyclones tend to dominate the southern subtropical gyres and cyclones the northern flank of the acc major causes of regional polarity dominance are larger formation numbers and lifespans with a contribution of differential propagation pathways of long lived eddies areas of dominance of one polarity are generally congruent with the same polarity being longer lived bigger of larger amplitude and more intense eddies extend down to at least 2000 m in the acc eddies show near surface temperature and salinity maxima whereas eddies in the subtropical areas generally have deeper anomaly maxima presumably inherited from their origin in the boundary currents the temperature and salinity signatures of the average eddy suggest that their tracer anomalies are a result of both trapping in the eddy core and stirring

metrics for quantifying anthropogenic impacts on geomorphology road networks this work tests the capability of a recently published topographic index the slope local length of auto correlation sllac to portrait and delineate anthropogenic geomorphologies the patterns of the anthropogenic pressure are defined considering the road network density and the urban complexity index uci first the research investigates the changes in the sllac in two derived parameters average sllac and the sllac surface peak curvature spc per km2 connected to the increasing of the anthropogenic structures next natural and anthropogenic landscapes are clustered and classified the results show that there is a direct correlation between the road network density and the uci and the mean sllac per km2 however the spc is inversely correlated with the anthropogenic pressure network density and urban complexity this shows that the surface morphology slope of regions presenting anthropogenic structures tends to be well organized low spc and in general self similar at a long distance higher average sllac the results of the clustering approach show that the procedure can correctly depict anthropogenic landscapes having a road network density greater than about 3 km km2 also in areas covered by vegetation this latter result is promising for the use of such a procedure in regions that cannot be seen directly from orthophotos or satellite images the proposed method can actively capture the alteration produced by road networks on surface morphology identifying different signatures of urban development exploration and densification networks that are responsible for increasing the local density of the network and expanding the network into new areas respectively the effects of this alteration on surface processes could be significant for future research creating new questions about differences due to human or landscape forcing on earth surface processes copyright 2015 john wiley sons ltd

a simple raster based model for flood inundation simulation in this paper the development of a new model for simulating flood inundation is outlined the model is designed to operate with high resolution raster digital elevation models which are becoming increasingly available for many lowland floodplain rivers and is based on what we hypothesise to be the simplest possible process representation capable of simulating dynamic flood inundation this consists of a one dimensional kinematic wave approximation for channel flow solved using an explicit finite difference scheme and a two dimensional diffusion wave representation of floodplain flow the model is applied to a 35 km reach of the river meuse in the netherlands using only published data sources and used to simulate a large flood event that occurred in january 1995 this event was chosen as air photo and synthetic aperture radar sar data for flood inundation extent are available to enable rigorous validation of the developed model 100 50 and 25 m resolution models were constructed and compared to two other inundation prediction techniques a planar approximation to the free surface and a relatively coarse resolution two dimensional finite element scheme the model developed in this paper outperforms both the simpler and more complex process representations with the best fit simulation correctly predicting 81 9 of inundated and non inundated areas this compares with 69 5 for the best fit planar surface and 63 8 for the best fit finite element code however when applied solely to the 7 km of river below the upstream gauging station at borgharen the planar model performs almost as well 83 7 correct as the raster model 85 5 correct this is due to the proximity of the gauge which acts as a control point for construction of the planar surface and the fact that here low lying areas of the floodplain are hydraulically connected to the channel importantly though it is impossible to generalise such application rules and thus we cannot specify a priori where the planar approximation will work simulations also indicate that for this event at least dynamic effects are relatively unimportant for prediction of peak inundation lastly consideration of errors in typically available gauging station and inundation extent data shows the raster based model to be close to the current prediction limit for this class of problem q 2000 elsevier science b v all rights reserved

the accuracy of sequential aerial photography and sar data for observing urban flood dynamics a case study of the uk summer 2007 floods in this paper we examine for the first time the potential of remote sensing to monitor flood dynamics in urban areas and constrain mathematical models of these processes this is achieved through the development of a unique data set consisting of a series of eight space borne synthetic aperture radar sar and aerial photographic images of flooding of the uk town of tewkesbury acquired over an eight day period in summer 2007 previous observations of urban flooding have used single image and wrack mark data and have therefore been unable to adequately chart the propagation and recession of flood waves through complex urban topography by using a combination of space borne radar and aerial imagery we are able to show that remotely sensed imagery particularly from the new terrasar x radar can reproduce dynamics adequately and support flood modelling in urban areas we illustrate that image data from different remote sensing platforms reveal sufficient information to distinguish between models with varying degrees of channel floodplain connectivity particularly toward the end of the recession phase of the event for this test case our results also show that high resolution sar imagery even when acquired from satellites can reveal important hydraulic characteristics difficult to simulate with current dynamic flood models hence it is established at least for this test case and event that sar imagery from as far as several hundred kilometers from the earth s surface can deliver important information about floodplain dynamics that can be used to identify and help build suitable models even in built up environments

transport of 234u in the opalinus clay on centimetre to decimetre scales the opalinus clay formation in north switzerland is a potential host rock for a deep underground radioactive waste repository the distribution of u 238 u 234 and th 230 was studied in rock samples of the opalinus clay from an exploratory borehole at benken canton of zurich using mc icp ms the aim of u 234 was to assess the in situ long term migration behaviour in this rock very low hydraulic conductivities of the opalinus clay reducing potential of the pore water and its chemical equilibrium with the host rock are expected to render both u 238 and th 230 immobile if u is heterogeneously distributed in the opalinus clay gradients in the supply of u 234 from the rock matrix to the pore water by the decay of u 238 will be established diffusive redistribution separates u 234 from its immobile parent u 238 resulting in bulk rock u 234 u 238 activity disequilibria these may provide a means of estimating the mobility of u 234 in the rock if the diffusion rate of u 234 is significant compared to its decay rate sampling was carried out on two scales drilling of cm spaced samples from the drill core was done to study mobility over short distances and elucidate possible small scale lithological control homogenized 25 cm long portions of a 2 m long drill core section were prepared to provide information on transport over a longer distance variations in u and or th content on the cm scale between clays and carbonate sandy layers are revealed by beta scanning which shows that the dominant clay is richer in both elements samples were digested using aqua regia followed by total hf dissolution yielding two fractions in all studied samples u was found to be concentrated in the hf digestion fraction it has a high u th ratio and a study by sem eds points to sub mu m up to several mu m in size zircon grains as the main u rich phase this fraction consistently has u 234 u 238 activity ratios below unity the minute zircon grains constitute the major reservoir of u in the rock and act as constant rate suppliers of u 234 into the rock matrix and the pore water the aqua regia leach fraction was found to be enriched in th and complementary to the hf fraction having u 234 u 238 activity ratios above unity it is believed that these u activity ratios reflect the surplus of having u 234 delivered from the zircon grains some cm spaced samples show bulk rock u 234 u 238 activity ratios that are markedly out of equilibrium in most of them a striking negative correlation between the total u content and the bulk rock u 234 u 238 activity ratios is observed this is interpreted to indicate net u 234 transfer from regions of higher supply of u 234 towards those of lower supply which is in most cases equivalent to transfer from clayey towards carbonate sandy portions of the rock in contrast the 25 cm averaged samples all have uniform bulk rock u 234 u 238 activity ratios in equilibrium indicating u immobility in the last 1 1 5 ma on this spatial scale it is concluded that the small scale lithological variations which govern u spatial distribution in the opalinus clay are the major factor determining u 234 in situ supply rates regulating its diffusive fluxes and controlling the observed bulk rock u 234 u 238 activity ratios a simple box model is presented to simulate the measured bulk rock u 234 u 238 activity ratios and to give an additional insight into the studied system c 2008 elsevier ltd all rights reserved

element mobility studies of two drill cores from the gotemar granite krakemala test site southeast sweden abstract a pilot study was carried out on two relatively deep drill cores 600 m from the gotemar granite massif in s e sweden this granite is typical of the 1400 ma anorogenic granites of the northern hemisphere samples from representative unfractured parts of the cores together with four samples taken along a profile tangential to a fracture plane at 280 m depth were investigated chemically mineralogically and isotopically the results show that after crystallisation subtle and pervasive open system modifications of the trace element chemistry of the granite took place whereas the major element chemistry and minera logical data emphasised the relative homogeneity of the gotemar granite samples investigated trace elements such as u rb and pb revealed irregular distributions which are probably the result of large scale hydrothermal alteration processes this conclusion is supported by isotopic studies which indicate that whole rock samples were open to a gain or loss of pb and possibly u at 420 171 ma ago in addition isotopic data for u pb and u ra are consistent with a recent minor loss of u the pervasive alteration and the more recent mobilisation of u are evident to a depth of at least 600 m the effects are most prevalent along major fracture zones and within the upper 250 300 m of one drill hole where a high frequency of crush zones has been noted higher fe oxidation ratios higher rb contents lower u contents and correspondingly higher th u ratios all characterise this zone

high resolution two dimensional spatial modelling of flow processes in a multi thread channel this paper describes application and testing of a two dimensional numerical flow model in a multi thread reach of a proglacial stream the model solves the depth averaged form of the navier stokes equations for open channel flow incorporating a two equation turbulence closure an analytical correction for the effects of secondary circulation and a rigid lid approximation the model requires as input the channel bed topography the water surface bed roughness and inflow discharge information and predicts the spatial distribution of depth averaged velocity and eddy viscosity the results have been subjected to intensive testing using simple assessment of numerical performance e g conservation of mass and momentum numerical convergence distributed sensitivity analysis and comparison of model predictions with field measurements of velocity the results are encouraging particularly given some of the difficulties in obtaining accurate distributed cross stream and downstream velocities distributed sensitivity analysis allowed more detailed consideration of the necessary development of the model this suggested that significant errors in the velocity predictions were largely a result of uncertainty in the specification of both the magnitude and the spatial variation of bed roughness secondly the two equation turbulence closure was observed to have little effect upon model predictions except in the vicinity of the side walls in applications of models of this type to irregular coarse bedded channels improvements in the specification of the topographic boundary condition specification and bed roughness are likely to be more important than a sophisticated turbulence closure scheme thirdly although the secondary circulation correction was observed to reproduce some of the expected streamwise transfer of momentum the effects were seen to be relatively small given the intensity of secondary circulation defined in field contexts the inability of the model to correct effectively for the momentum transfer associated with secondary circulation processes related to topographic discordance and shear generated turbulence suggests that further work is required in this respect 1998 john wiley sons ltd

the role of isotope geochemistry studies in the canadian nuclear fuel waste management program abstract the objective of the canadian nuclear fuel waste management program is to develop and assess a method for the safe disposal of used nuclear fuel wastes from canadian nuclear power generating facilities the concept that is being developed involves the disposal of these wastes in a cavity mined at a depth of 500 1000 m in a plutonic rock formation both in the assessment of this concept and in any possible future site selection the geochemistry of the rock formation and of the groundwater plays a significant role isotope geochemistry studies involve the determination of the distribution and behaviour of stable and radioactive isotopes in the groundwater and in the rock matrix this information can be used to shed light on the geochemical history of the rock formation under investigation and increase the understanding of the geochemical processes that govern the evolution of these rock formations the information can in principle also be used to date the various geological events and processes that have led to the distribution of radioactive isotopes in the rock and in the groundwater

terrain representation impact on periurban catchment morphological properties modelling the hydrological behaviour of suburban catchments requires an estimation of environmental features including land use and hydrographic networks suburban areas display a highly heterogeneous composition and encompass many anthropogenic elements that affect water flow paths such as ditches sewers culverts and embankments the geographical data available either raster or vector data may be of various origins and resolutions urban databases often offer very detailed data for sewer networks and 3d streets yet the data covering rural zones may be coarser this study is intended to highlight the sensitivity of geographical data as well as the data discretisation method used on the essential features of a periurban catchment i e the catchment border and the drainage network three methods are implemented for this purpose the first is the dem for digital elevation model treatment method which has traditionally been applied in the field of catchment hydrology the second is based on urban database analysis and focuses on vector data i e polygons and segments the third method is a tin or triangular irregular network which provides a consistent description of flow directions from an accurate representation of slope it is assumed herein that the width function is representative of the catchment s hydrological response the periurban chezine catchment located within the nantes metropolitan area in western france serves as the case study the determination of both the main morphological features and the hydrological response of a suburban catchment varies significantly according to the discretization method employed especially on upstream rural areas vector and tin based methods allow representing the higher drainage density of urban areas and consequently reveal the impact of these areas on the width function since the dem method fails tins seem to be more appropriate to take streets into account because it allows a finer representation of topographical discontinuities these results may help future developments of distributed hydrological models on periurban areas

development of a three dimensional unstructured mesh finite element model for flood propagation abstractin this paper a three dimensional 3d finite element model for flooding has been developed which can be applied to different types of flooding the theoretical methodology has been intro

modelling floodplain flows using a two dimensional finite element model a prototype two dimensional finite element flow model for depth averaged free surface flows was developed for floodplain environments limited refinement of the model s physical representation was undertaken and the enhanced scheme applied to an 11 km river channel floodplain reach in the u k preliminary model results indicate that this modelling approach can be used to identify dynamic variations in the flow field parameters over length scales of the order of 10 100 m potentially such data have the ability to permit detailed analysis of short term floodplain sedimentary dynamics

oceanic isopycnal mixing by coordinate rotation abstract current numerical models of oceanic circulation differentiate between the eddy diffusion and viscosity transport along the geopotential horizontal and vertical directions only in order to model the effect of anisotropic turbulence as diffusive transport along and across density surfaces the isopycnal mixing tensor has been transformed from a diagonal second rank tensor in the isopycnal coordinate system to a tensor containing off diagonal elements in the geopotential coordinate system

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

history of actinide and minor element mobility in an archean granitic batholith in manitoba canada abstract surface and borehole core samples from the lac du bonnet granite manitoba canada have been analysed for major element concentrations fe 3 fe total ratios rare earth element ree content and actinide isotopic abundances this work forms part of the geological investigations of the canadian nuclear fuel waste management program performed by atomic energy of canada limited aecl the study attempts to understand the history of and processes governing mobilisation of elements and naturally occurring radionuclides during high and low temperature alteration events in fluid bearing fractures in the granite one surface sample and two core samples from 150 m and 730 m are each in contact with fractures in the granite and show evidence of alteration events that penetrated the rock matrix over distances of at least 3 cm loss of ca and na is seen in cores from a depth of 150 m from the highly altered hematite rich rock adjacent to sub horizontal fracture zones at the underground research laboratory url of aecl near lac du bonnet in contrast k fe fe 3 fe and u concentrations increase towards the fracture surface due to formation of illite and association of u with hematite and the illite at the fracture surface u continues to increase but fe and thefe 3 fe ratio decrease indicating fe removal by reduction the ree also show some enrichment in more altered rock at intermediate depths but the total ree concentration is lower than in the surface and deep core samples no clear trends are visible for parent and fracture surface ree in surface and deep core samples however disequilibrium values of 234 u 238 u and 230 th 234 u ratios in surface and intermediate depth core samples indicate that u has been mobilised in recent geological time the last ma but th has remained relatively immobile high th u and 230 th 234 u ratios in surface samples are indicative of rapid leaching of u but little isotopic fractionation probably within the last 10 5 a apparently unaltered rock several centimetres distant from the fracture in surface and intermediate depth samples has lost appreciable u but evidence from u series disequilibrium studies suggests that this process occurred more than one million years ago perhaps during deuteric or hydrothermal alteration core from a fracture at depth in the granite shows little hematite or clay formation and lacks evidence of ree and recent or ancient actinide mobilisation the u series results are correlated with the observed concentrations and isotope activity ratios of u in groundwaters sampled from the same or adjacent fractures analyses of samples of highly altered rubble recovered from centre portions of fracture zones at the url show both excesses and deficiencies of 234 u and 230 th in neighbouring locations possibly due to the presence of a redox front whose position is controlled by modern groundwater composition the implications of these results are discussed for the concept of disposal of nuclear fuel waste at depth in plutonic rock on the canadian shield

role of mesoscale eddies in cross frontal transport of heat and biogeochemical tracers in the southern ocean abstractthis study examines the role of processes transporting tracers across the polar front pf in the depth interval between the surface and major topographic sills which this study refers to as the pf core a preindustrial control simulation of an eddying climate model coupled to a biogeochemical model gfdl climate model version 2 6 cm2 6 simplified version of the biogeochemistry with light iron nutrients and gas minibling 0 1 ocean model is used to investigate the transport of heat carbon oxygen and phosphate across the pf core with a particular focus on the role of mesoscale eddies the authors find that the total transport across the pf core results from a ubiquitous ekman transport that drives the upwelled tracers to the north and a localized opposing eddy transport that induces tracer leakages to the south at major topographic obstacles in the ekman layer the southward eddy transport only partially compensates the northward ekman transport while below the ekman layer the sout

on the possibility of determining rates of removal of uranium from crystalline igneous rocks using u series disequilibria 1 a u leach model and its applicability to whole rock data the removal of u from granitic rocks is characterised by234u 238u 1 and 230th 234u 1 it is notable from weathered eye dashwa lakes canada granite samples and from the published data that230th 234u ratios seldom exceed a limiting value of about 2 a u leach model is discussed in detail which may account for these observations the model assumes that 230th is practically immobile and that the removal of u can then be measured against the decay rate of the unsupported230th a property of the model is that the isotope ratios reach constant values reflecting a kind of secular equilibrium and this implies that u is seldom removed faster than the decay of230th if the limited230th 234u ratios from the data correspond to secular equilibrium ratios then this allows simple calculation of u leach rates from any given subsurface sample a test for the model using235u 231pa ratios is suggested a comparison of leach rates derivable from u th pb systematics of colorado and wyoming granite samples with the corresponding estimates from the model shows that the latter are high by a factor of 10 50 data from rapidly weathered surface rinds suggests that the presence of labile u restricts the application of the model to subsurface low weathered zones

the relative mobility of u th and ra isotopes in the weathered zones of the eye dashwa lakes granite pluton northwestern ontario canada radioisotope activity ratios of weathered surface rocks from the eye dashwa lakes granite pluton show that in the 238u decay series 226ra has been leached more rapidly than the grandparent 234u and 238u isotopes the observation of 238th232th disequilibria in the 232th decay series shows that either 228th half life of 1 9 yrs or 228ra half life of 5 75 yrs have been removed from these rocks very rapidly indeed isotope ratios of separated mineral fractions appear to show that whereas uranium tends to be removed from all mineral fractions ra is strongly readsorbed onto feldspars presumably as these undergo alteration to clay minerals this necessitates making a distinction between intermineral mobility of u or ra and the net loss of u or ra from the whole rock an attempt has been made to model quantitatively the transport rate of ra though with little success failure of the modelling appears to indicate that the mobility of 228ra is higher than might be predicted by the mobility of 226ra that is the two isotopes are not strict analogues of one another in their response to initial weathering

urban fluvial flood modelling using a two dimensional diffusion wave treatment part 2 development of a sub grid scale treatment this paper develops and tests a sub grid scale wetting and drying correction for use with two dimensional diffusion wave models of urban flood inundation the method recognizes explicitly that representations of sub grid scale topography using roughness parameters will provide an inadequate representation of the effects of structural elements on the floodplain e g buildings walls as such elements not only act as momentum sinks but also have mass blockage effects the latter may dominate especially in structurally complex urban areas the approach developed uses high resolution topographic data to develop explicit parameterization of sub grid scale topographic variability to represent both the volume of a grid cell that can be occupied by the flow and the effect of that variability upon the timing and direction of the lateral fluxes this approach is found to give significantly better prediction of fluvial flood inundation in urban areas than traditional calibration of sub grid scale effects using manning s n in particular it simultaneously reduces the need to use exceptionally high values of n to represent the effects of using a coarser mesh process representation and increases the sensitivity of model predictions to variation in n

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

changing uranium distributions during weathering of granite abstract changes in uranium distribution during chemical weathering were investigated in three granitoid types from the new england district new south wales australia over a range of samples from unweathered rock to profoundly weathered material uranium fission track micromapping was used to characterise the three principal modes of u abundance in unweathered granitoid rock low concentrations of background u in fine fractures in quartz and in deuterically altered feldspar biotite and hornblende interstitial u in concentrations between 140 and 1500 g g 1 principally in hydrated fe oxide mn oxide and clay minerals and the greatest proportion as resistate u 90 4000 g g 1 located in the accessory minerals during low temperature chemical weathering a significant net u loss occurs and the remaining u is redistributed amongst the three modes background u is depleted and the mobilised u is adsorbed by interstitial aggregates thereby increasing interstitial u concentrations resistate u is also depleted as sphene zircon monazite and acicular apatite retain their initial u concentrations but are reduced in modal abundance prismatic apatite fluorite and allanite are progressively removed the significant net loss of u during chemical weathering provides uranium for potential secondary sedimentary mineralisation and implies that weathered granitoid rock is not an appropriate element in the geological barrier for nuclear waste

vertical heat flux in the ocean estimates from observations and from a coupled general circulation model the net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically generally it is necessary to rely on global climate models to study these processes in detail in the present study it is shown that a key component of the vertical heat flux namely that associated with the large scale mean vertical circulation can be diagnosed over extra tropical regions from global observational data sets this component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance combined with estimates of absolute geostrophic flow results are compared with the output of a non eddy resolving coupled atmosphere ocean general circulation model reasonable agreement is found in the latitudinal distribution of the vertical heat flux as well as in the area integrated flux below about 250 m depth the correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation the vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the southern hemisphere in particular the southern ocean this is driven by the ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth the results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean

evidence for the stability of the potential nuclear waste host sphene over geological time from uranium lead ages and uranium series measurements abstract a sphene based glass ceramic material is being investigated as a potential host for canadian nuclear fuel recycle waste the ability of sphene to retain certain radionuclides over geological time is examined using observed properties and age measurements of natural sphenes the long term stability of sphene is determined by comparing u th pb isotopic age data for sphene from the literature with ages determined for zircon and other minerals better internal agreement is found between u th pb sphene ages than for zircon ages indicating the resistance of sphene to daughter radionuclide loss over periods as long as 3000 ma excellent agreement was observed between sphene ages and the estimated age of crystallization of the host rocks or vein infillings except where subsequent metamorphim had reset the sphene age complete lead loss was generally found to accompany high grade metamorphic conditions when temperatures exceeded 500 c stability over shorter periods of geological time was found for vein infilling and mineral separates of sphene using uranium series disequilibrium analysis conditions of secular equilibrium in the decay chain 238 u 234 u 230 th 226 ra were observed for most of the 21 sphenes studied indicating that no radionuclide migration had occurred over periods as long as the last 1 ma exceptions to this were four sphenes that had 234 u deficiencies between 6 and 24 and two sphenes that showed 226 ra 230 rh disequilibrium no correlation was found between the extent of radiation damage suffered by the sphenes and the presence of uranium series disequilibrium the presence of alteration products in three sphenes did correlate however with measured disequilibrium indicating that some 234 u and 226 ra had been lost or gained by these samples in the last 1 ma and 8 ka respectively

reduced complexity strategies for modelling urban floodplain inundation abstract significant advances in flood inundation modelling have been made in the last decade through the use of a new generation of 2d hydraulic numerical models these offer the potential to predict the local pattern and timing of flood depth and velocity enabling informed flood risk zoning and improved emergency planning with the availability of high resolution dems derived from airborne lidar these models can theoretically now be routinely parameterized to represent considerable topographic complexity even in urban areas where the potential exists to represent flows at the scale of individual buildings currently however computational constraints on conventional finite element and volume codes typically require model discretization at scales well below those achievable with lidar and are thus unable to make optimal use of this emerging data stream in this paper we review two strategies that attempt to address this mismatch between model and data resolution in an effort to improve urban flood forecasts the first of these strives for a solution by simplifying the mathematical formulation of the numerical model by using a computationally efficient 2d raster storage cell approach coupled to a 1d channel model this parsimonious model structure enables simulations over large model domains offering the opportunity to employ a topographic discretization strategy which explicitly represents the built environment the second approach seeks to further reduce the computational overhead of this raster method by employing a subgrid parameterization to represent the effect of buildings and micro relief on flow pathways and floodplain storage this multi scale methodology enables highly efficient model applications at coarse spatial resolutions while retaining information about the complex geometry of the built environment these two strategies are evaluated through numerical experiments designed to reconstruct a flood in the small town of linton in southern england which occurred in response to a 1 in 250 year rainfall event in october 2001 results from both approaches are encouraging with the spatial pattern of inundation and flood wave propagation matching observations well both show significant advantages over a coarse resolution model without subgrid parameterisation particularly in terms of their ability to reproduce both hydrograph and inundation depth measurements simultaneously without need for recalibration the subgrid parameterization is shown to achieve this without contributing significant computational complexity and reduces model run times by an order of magnitude

evidence of a southward eddy corridor in the south west indian ocean mesoscale eddies and meanders have been shown to be one of the dominant sources of flow variability in the world s ocean one example of an isolated eddy hotspot is the south west indian ridge swir several investigations have shown that the swir and the corresponding planetary potential vorticity field f h exert a strong influence on the location and dynamics of the antarctic circumpolar current acc resulting in substantial fragmentation of the jets downstream of the ridge the easterly extension of this eddy corridor appears to be restricted to the deep channel separating the conrad rise from the del cano and crozet plateau however while the fate of eddies formed at the swir has been widely investigated and the frontal character of this eastward extension is well known the zone of diminishing variability that extends southwards to approximately 60 s remains poorly sampled using a combination of argo aviso and ncep ncar datasets the character of this eddy corridor as a conduit for warm core eddies to move across the acc into the antarctic zone is investigated in this study we track a single warm core eddy as it moves southwards from an original position of 31 e 50 20 s to where it dissipates 10 months later in the enderby basin at 56 20 s an argo float entrained within the eddy confirms that its water masses are consistent with water found within the antarctic polar frontal zone north of the apf latent and sensible heat fluxes are on average 8w m2 and 10w m2 greater over the eddy than directly east of this feature it is estimated that the eddy lost an average of 5w m2 of latent heat and 5w m2 of sensible heat over a 1 year period an amount capable of melting approximately 0 92m of sea ice in addition using an eddy tracking algorithm a total of 28 eddies are identified propagating southwards 25 of which are anti cyclonic in rotation based on the new argo float data combined with aviso and ncep ncar datasets these results suggest that the southward passage of warm core eddies act as vehicles transporting heat salt and biota southwards across the acc and into the eastern boundary of the weddell gyre

226ra 238u and 228th 228ra disequilibrium as weathering indices in beach sand sediments associated with granitoids from cyclades greece abstract radioactive secular disequilibrium measured as the absolute difference from 1 of the 226ra 238u and 228ra 228th ratios have been used to determine weathering extent twenty eight samples from beach sands of cyclades islands all of them being the weathering products of the local granitic plutons are studied for their secular disequilibrium in both 238u and 232th series 226ra 238u and 228th 228ra respectively the results are compared to weathering indices already in use worldwide and suggest a significant linear correlation of u series disequilibrium with wip alkaline and alkaline earth element leaching and pwi silica leaching for the beach sands studied and significant non linear correlations with cia chemical index of alteration and pia plagioclase index of alteration considering only the heavy mineral enriched samples significant correlations exist between u series disequilibrium and cia ciw chemical index of weathering and pia therefore with an appropriate choice of the weathering index and samples both u series and weathering index can recover the extent of chemical weathering on the other hand the use of th series disequilibrium as a weathering index is limited due to 228th and 228ra geochemistry and especially due to their short radionuclide half lives u series disequilibrium can therefore be used as a relatively sensitive weathering index in sediments consistent with cia ciw and pia indices however the mineralogical composition must be considered more specifically the mineral content of the sediments should involve considerable amounts of sensitive to weathering minerals e g fe mg minerals as well as feldspars

frontal movements and property fluxes contributions to heat and freshwater trends in the southern ocean we examine the synoptic variability of temperature and salinity in the southern ocean using a static gravest empirical mode gem mapping based on historical hydrography and a time evolving projection of the gem created using satellite altimetry satgem the gem and satgem projections allow the separation of observed trends into a component due to a shift of the circumpolar fronts adiabatic using the satgem and a component due to changes in water masses diabatic expressed as a temporal trend in residual between historical hydrography and the static gem the mean southward movement of the antarctic circumpolar current acc fronts drives an adiabatic warming of 1 196 0 090 w m 2 distributed over most of the acc and at all depths this is strongest where the meridional temperature gradient is largest such as in the upper 1000 dbar of the subantarctic front saf there is a weak adiabatic freshening of 6 57 0 18 mm yr 1 m 2 concentrated mainly below the antarctic intermediate water and south of the saf residuals between historical hydrography and the static gem field driven by diabatic changes in the water mass structure have temporal trends in temperature and salinity when these trends are integrated over the whole acc there is a net cooling of 0 628 0 129 w m 2 and strong freshening of 30 27 0 70 mm yr 1 m 2 by combining the diabatic and adiabatic components and integrating over the acc the net increase in heat and freshwater in the region is 0 570 0 099 w m 2 and 36 91 0 72 mm yr 1 m 2 respectively the sum of the adiabatic and diabatic changes are consistent with previous trends inferred from observations

predicting floodplain inundation raster based modelling versus the finite element approach we compare two approaches to modelling floodplain inundation a raster based approach which uses a relatively simple process representation with channel flows being resolved separately from the floodplain using either a kinematic or diffusive wave approximation and a finite element hydraulic model aiming to solve the full two dimensional shallow water equations a flood event on a short c 4 km reach of the upper river thames in the uk is simulated the models being validated against inundation extent as determined from satellite synthetic aperture radar sar imagery the unconstrained friction parameters are found through a calibration procedure where a measure of fit between predicted and observed shorelines is maximized the raster and finite element models offer similar levels of performance both classifying approximately 84 of the model domain correctly compared with 65 for a simple planar prediction of water surface elevation further discrimination between models is not possible given the errors in the validation data the simple raster based model is shown to have considerable advantages in terms of producing a straightforward calibration process and being robust with respect to channel specification copyright 2001 john wiley sons ltd

comparing the performance of a 2 d finite element and a 2 d finite volume model of floodplain inundation using airborne sar imagery the performances of a finite volume model sfv and finite element model telemac 2d in reproducing inundation on a 16 km reach of the river severn united kingdom are compared predicted inundation extents are compared with 4 airborne synthetic aperture radar images of a major flood event in november 2000 and these are used to calibrate 2 values of manning s n for the channel and floodplain the four images are shown to have different capacities to constrain roughness parameters with the image acquired at low flow rate doing better in determining these parameters than the image acquired at approximately peak flow this is assigned to the valley filling nature of the flood and the associated insensitivity of flood extent to changes in water level the level of skill demonstrated by the models when compared with inundation derived using a horizontal water free surface also increases as flow rate drops the two models show markedly different behaviours to the calibration process with telemac showing less sensitivity and lower optimum values for manning s n than sfv when the models are used in predictive mode calibrated against one image and predicting another sfv performs better than telemac copyright 2007 john wiley sons ltd

in situ radionuclide transport and preferential groundwater flows at ineel idaho decay series disequilibrium studies uranium and thorium decay series disequilibria in groundwater occur as a result of water rock interactions and they provide site specific natural analog information for assessment of in situ long term migration of radionuclides in the far field of a nuclear waste disposal site in this study a mass balance model was used to relate the decay series radionuclide distributions among solution sorbed and solid phases in an aquifer system to processes of water transport sorption desorption dissolution precipitation radioactive ingrowth decay and recoil isotopes of u 238u 234u th 232th 230th 228th 234th ra 226ra 228ra 224ra and rn 222rn were measured in 23 groundwater samples collected from a basaltic aquifer at the idaho national engineering and environmental laboratory ineel idaho the results show that groundwater activities of th and ra isotopes are 2 4 orders lower than those of their u progenitors which average 1 35 0 40 dpm 238u l with 234u 238u ratios of 1 6 3 0 222rn activities range from 20 to 500 dpm l modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water rock interaction at ineel 1 time for sorption is minutes for ra and th time for desorption is days for ra and years for th and time for precipitation is days for th years for ra and centuries for u 2 retardation factors due to sorption average 106 for 232th 104 for 226ra and 103 for 238u 3 dissolution rates of rocks are 70 to 800 mg l y 4 ages of groundwater range from 10 to 100 years contours of groundwater age as well as spatial patterns of radionuclide disequilibria delineate two north south preferential flow pathways and two stagnated locales relatively high rates of dissolution and precipitation and recoil of 222rn occur near the groundwater recharging sites as well as in the major flow pathways decay of the sorbed parent radionuclides e g 226ra and 228ra on micro fracture surfaces constitutes an important source of their daughter 222rn and 228th activities in groundwater

large scale floodplain modelling a two dimensional horizontal finite element numerical model rma 2 was applied to a 24 km river channel floodplain reach in west germany initial results indicate that finite element schemes may successfully estimate inundation in large scale floodplain applications potentially the resulting detailed velocity vector distributions and identification of inundation zones throughout storm events could provide an insight into the present day sedimentary environment on the floodplain

impact of mesoscale eddy transfer on heat uptake in an eddy parameterizing ocean model abstractusing a set of experiments with an eddy parameterizing ocean model it is found that the strength of the atlantic meridional overturning circulation amoc intensifies with the decrease of

a mechanism of mixed layer formation in the indo western pacific southern ocean preconditioning by an eddy driven jet scale overturning circulation abstractthe formation of a narrow band of the deep winter mixed layer hereinafter mixed layer wedge in the indo western pacific southern ocean is examined using an eddy resolving parallel ocean program pop model simulation the mixed layer wedge starts to deepen in june centered at 47 5 s with a meridional scale of only 2 latitude its center is located 1 north of the model s subantarctic front saf the argo based observed mixed layer is similarly narrow and occurs adjacent to the observed saf in the small sector of 130 142 e where the saf is persistent and the mixed layer is deepest the formation of the narrow mixed layer wedge coincides with destratification underneath the mixed layer this destratification can be attributed primarily to the downwelling branch of a jet scale overturning circulation jsoc the jsoc which was reported in an earlier study by the authors is driven by eddy momentum flux convergence and is therefore thermally indirect its descending branch occurs on the

floodplain friction parameterization in two dimensional river flood models using vegetation heights derived from airborne scanning laser altimetry two dimensional 2 d hydraulic models are currently at the forefront of research into river flood inundation prediction airborne scanning laser altimetry is an important new data source that can provide such models with spatially distributed floodplain topography together with vegetation heights for parameterization of model friction the paper investigates how vegetation height data can be used to realize the currently unexploited potential of 2 d flood models to specify a friction factor at each node of the finite element model mesh the only vegetation attribute required in the estimation of floodplain node friction factors is vegetation height different sets of flow resistance equations are used to model channel sediment short vegetation and tall and intermediate vegetation the scheme was tested in a modelling study of a flood event that occurred on the river severn uk in october 1998 a synthetic aperture radar image acquired during the flood provided an observed flood extent against which to validate the predicted extent the modelled flood extent using variable friction was found to agree with the observed extent almost everywhere within the model domain the variable friction model has the considerable advantage that it makes unnecessary the unphysical fitting of floodplain and channel friction factors required in the traditional approach to model calibration copyright 2003 john wiley sons ltd

uranium series disequilibrium studies of granitic rocks abstract igneous plutons of the canadian shield which are to be considered as possible storage sites for radioactive waste should be free from any evidence of past mobility of chemical species through the rock however cores taken from some plutons to depths of up to 1 km reveal the presence of hydrous low temperature alteration along joints and fractures and within the body of the rock to test whether such rocks or any others have been subjected to chemical transport in geologically recent times we may study the state of radioactive equilibrium between 238 u 235 u and 232 th and their short lived daughterisotopes members of the decay series of these parent isotopes have half lives ranging from a few hours to 0 25 ma also the chemical characteristics of the various daughters vary significantly allowing us to test the mobility of isotopes of similar half life but differing chemistry if the rock has been chemically undisturbed for 10 ma or more then the activity in d p m g of each daughter in these decay schemes will be equal to that of its parent isotope conversely if the rock was chemically disturbed 10 n a ago then some daughter isotopes with half lives t 10 n a will be out of equilibrium with their parents preliminary results are presented showing disequilibrium effects in samples from atikokan ontario

actinide and rare earth element characteristics of deep fracture zones in the lac du bonnet granitic batholith manitoba canada the history of major trace and actinide element mobility and fluid infiltration has been studied in two deep fractures 1 km in the lac du bonnet batholith as part of the canadian nuclear fuel waste management program core samples collected from two fracture zones fr1 and fr2 1175 m deep containing saline groundwater tds 50 g l were investigated mineralogically chemically and isotopically 238u series o and h several sequentially overprinting alteration stages were identified from early high temperature to later low temperature hydrothermal alteration k feldspar illite chlorite and later kaolinite formed during these stages subsequent infiltration of oxidizing fluids produced alteration of the chlorite to hydrous iron oxides fracture zone fr1 contains predominantly hematite coating fracture zone fr2 is characterized by the formation of a breccia and by an intense alteration of the granite in contact with this breccia to illitic clay alteration occurred during infiltration either of formation brines or of isotopically evolved meteoric water where 18o 8 to 12 and d 65 to 20 at calculated temperatures between 250 and 25 c loss of ca na and sr and to some extent ba was observed in all the altered samples relative to fresh granite a sharp increase in k mg u th and ree was observed in the illitic clay rich zone pronounced disequilibria of 234u238u 0 5 230th234u 0 7 and 226ra230th 0 9 exist in the illitic clay indicating loss of 234u 230th and 226ra to the groundwater within the last 1 5 ma in contrast an excess of 234u 230th and 226ra was measured in the brecciated samples the disequilibria are consistent with a model involving loss of 234u 230th and 226ra to groundwater by recoil from u deposited on the illitic clay surfaces these radionuclides were deposited subsequently in the nearby brecciated zone

urban fluvial flood modelling using a two dimensional diffusion wave treatment part 1 mesh resolution effects high resolution data obtained from airborne remote sensing is increasing opportunities for representation of small scale structural elements e g walls buildings in complex floodplain systems using two dimensional 2d models of flood inundation at the same time 2d inundation models have been devel oped and shown to provide good predictions of flood inundation extent with respect to both full solution of the depth averaged navier stokes equations and simplified diffusion wave models however these models have yet to be applied extensively to urban areas this paper applies a 2d raster based diffusion wave model to determine patterns of fluvial flood inundation in urban areas using high resolution topog raphic data the aim of this paper is to explore the effects of spatial resolution upon estimated inundation extent and flow routing process this is important as the complexity of urban surfaces is such that chang ing data resolution may have a major effect upon surface representation and hence flow routing similarly few applications to date have explicitly considered the timing of the inundation process the model assumes that the prime source of the flood is fluvial pluvial floods and floods associated with urban drainage systems are not addressed the topographic data are based upon airborne laser altimetry li dar obtained for the city of york u k a series of image processing steps are used to pre prepare the topographic data a one dimensional hydraulic model of the ouse from skelton upstream of the city through to naburn weir downstream of the city is used to provide estimates of flux from the river to the floodplain for a major flood inundation event estimated to have a return period of greater than 100 years in november 2000 validation data were available in the form of inundation patterns obtained using aerial photography at a point on the falling limb of the flood event model response shows that even relatively small changes in model resolution have considerable effects on the predicted inundation extent and the timing of flood inundation timing sensitivity would be expected given the relatively poor representation of inertial processes in a diffusion wave model compared with previous work sensitivity to inundation extent is more surprising and is associated with three connected effects 1 the smoothing effect of mesh coarsening upon input topographical data 2 poorer representation of both cell blockage and surface routing processes as the mesh is coarsened where the flow routing is especially complex and 3 the ef fects of 1 and 2 upon water levels and velocities which in turn determine which parts of the floodplain the flow can actually travel to the combined effects of wetting and roughness parameters can compen sate in part for a coarser mesh resolution however the coarser the resolution the poorer the ability to control the inundation process as these parameters not only affect the speed but also the direction of wet ting thus high resolution data will need to be coupled to more sophisticated representation of the inun dation process in order to obtain effective predictions of flood inundation extent this is explored in a companion paper

probabilistic evaluation of flood hazard in urban areas using monte carlo simulation the goal of the presented research was the derivation of flood hazard maps using monte carlo simulation of flood propagation at an urban site in the uk specifically an urban area of the city of glasgow a hydrodynamic model describing the propagation of flood waves based on the de saint venant equations in two dimensional form capable of accounting for the topographic complexity of the area preferential outflow paths buildings manholes etc and for the characteristics of prevailing imperviousness typical of the urban areas has been used to derive the hydrodynamic characteristics of flood events i e water depths and flow velocities the knowledge of the water depth distribution and of the current velocities derived from the propagation model along with the knowledge of the topographic characteristics of the urban area from digital map data allowed for the production of hazard maps based on properly defined hazard indexes these indexes are evaluated in a probabilistic framework to overcome the classical problem of single deterministic prediction of flood extent for the design event and to introduce the concept of the likelihood of flooding at a given point as the sum of data uncertainty model structural error and parameterization uncertainty copyright 2011 john wiley sons ltd

uranium series radionuclide and element migration around the sanerliu granite hosted uranium deposit in southern china as a natural analogue for high level radwaste repositories abstract the sanerliu uranium deposit located in hunan province south china has a number of features analogous to aspects considered in the performance assessment of concepts for the disposal of high level radwaste deep in granite the deposit is hosted by medium to coarse grained porphyritic granite with a rb sr isochron age of 215 2 6 3 ma the orebodies have a burial depth of more than 160 400 m under the surface of the ground the major uranium mineralizations have u pb ages pitchblende of 103 2 0 6 88 3 0 5 and 51 2 0 4 ma and a hydrothermal origin the isotopic data show that the rb sr systems in the whole rock samples of less and un fractured host granite around the orebodies have been little disturbed since the altered granite formed 132 ma ago such samples have close to secular equilibrium activity ratios for 234 u 238 u 230 th 234 u and 226 ra 230 th indicating that obvious water rock interactions have not taken place in them within the interval of at least the last 1 ma the migration of uranium thorium and most trace elements in the ores and the host granite are limited often less than 30 35 m over 51 ma the alpha activity ratios 234 u 238 u 230 th 234 u and 226 ra 230 th for the samples from the fracture zones show obvious deviations from secular equilibrium indicating the deposition of uranium during the last 1 ma and of radium during the last 10 3 yr the fracture zones are channels for groundwater flow however the migration of uranium series radionuclides along the fracture zones is limited by adsorption onto the clays this is confirmed by the absence of any hydrogeochemical indication on the ground surface of the orebodies the ores have been well preserved in a natural aquifer system without any specially designed artificial barriers the migration behavior of radionuclides in the ores of the sanerliu deposit may be termed a worse case scenario for the safety assessment of a high level radwaste disposal repository hosted by granitic rocks

an analogue validation study of natural radionuclide migration in crystalline rocks using uranium series disequilibrium studies abstract concentrations and isotope ratios of natural decay series radionuclides have been studied in three contrasting crystalline rock drillcore sections intersecting water conducting fractures deep in the bedrock radioactive disequilibria resulting from rock water interactions were observed in two of the cores these indicated u migration along distances of 40 cm or more on a time scale of 1 myr in conjunction with th immobility under the same conditions fracture surface minerals showed a high affinity for radionuclide retardation and a limit of 3 cm is suggested for the migration of radionuclides from fracture fluids into the saturated rock this limit may correspond to enhanced matrix porosities resulting from earlier hydrothermal activity along the same channels

circumpolar response of southern ocean eddy activity to a change in the southern annular mode 1 analysis of satellite altimeter data reveals anomalously high eddy kinetic energy eke in the antarctic circumpolar current acc during the period 2000 2002 around 2 3 years earlier 1998 the circumpolar eastward wind stress as quantified by the southern annular mode sam showed a significant positive peak and we have shown previously that the acc peaked around 1998 in response an eddy resolving ocean model is used to investigate the delay between wind forcing and the eddy response and demonstrates that the lag is due to the time taken to influence the deep circulation of the acc winds over the southern ocean have shown a strong climatic increase over the past few decades if this increase in winds is also reflected as an increase in eddy activity as our analysis suggests it might then the increased poleward heat flux may have played a significant role in the observed warming of the southern ocean citation meredith m p and a m hogg 2006 circumpolar response of southern ocean eddy activity to a change in the southern annular mode geophys res lett 33 l16608 doi 10 1029 2006gl026499

vertical heat transport in eddying ocean models 1 the effect of mesoscale eddies on the vertical heat transport of the ocean is examined using two eddy resolving numerical models the global heat transport by the mean flow and diffusion are both downwards and are balanced by an upward eddy heat flux mean and eddy advective heat fluxes dominate the subpolar regions while diffusive flux is important primarily in the subtropics in the subtropical abyss the mean advective heat flux is balanced by a combination of eddy and diffusive fluxes and the classical munk type advective diffusive heat balance must be modified the munk and wunsch 1998 expression for the vertical turbulent diffusivity over estimates the diffusivity by as much as a factor of four near the base of the main thermocline this implies that the mixing required to close the meridional overturning circulation determined by munk and wunsch 1998 may be an over estimate due to the neglect of mesoscale eddies

uranium series disequilibrium in tuffs from yucca mountain nevada as evidence of pore fluid flow over the last million years abstract samples of tuff from boreholes drilled into fault zones in the exploratory studies facility esf and relatively unfractured rock of the cross drift tunnels at yucca mountain nevada have been analysed by u series methods this work is part of a project to verify the finding of fast flow paths through the tuff to esf level indicated by the presence of bomb 36cl in pore fluids secular radioactive equilibrium in the u decay series i e when the radioactivity ratios 234u 238u 230th 234u and 226ra 230th all equal 1 00 might be expected if the tuff samples have not experienced radionuclide loss due to rock water interaction occurring within the last million years however most fractured and unfractured samples were found to have a small deficiency of 234u weighted mean 234u 238u 0 95 0 01 and a small excess of 230th weighted mean 230th 234u 1 10 0 02 the 226ra 230th ratios are close to secular equilibrium weighted mean 0 94 0 07 these data indicate that 234u has been removed from the rock samples in the last 350 ka probably by pore fluids within the precision of the measurement it would appear that 226ra has not been mobilized and removed from the tuff although there may be some localised 226ra redistribution as suggested by a few ratio values that are significantly different from 1 0 because both fractured and unfractured tuffs show approximately the same deficiency of 234u this indicates that pore fluids are moving equally through fractured and unfractured rock more importantly fractured rock appears not to be a dominant pathway for groundwater flow otherwise the ratio would be more strongly affected and the th and ra isotopic ratios would likely also show disequilibrium application of a simple mass balance model suggests that surface infiltration rate is over an order of magnitude greater than the rate indicated by other infiltration models and that residence time of pore fluids at esf level is about 400 a processes of u sorption precipitation and re solution are believed to be occurring and would account for these anomalous results but have not been included in the model despite the difficulties the u series data suggest that fractured rock specifically the sundance and drill hole wash faults are not preferred flow paths for groundwater flowing through the topopah spring tuff and by implication rapid flow within 50 a from the surface to the level of the esf is improbable

integration of high resolution topographic data with floodplain flow models two dimensional hydraulic models of floodplain flow are at the forefront of current research into flood inundation mechanisms but they are however currently constrained by inadequate parameterization of topography and friction primarily due to insufficient or inaccurate data this paper reviews the effects of topographic representation on flood inundation extent prediction and presents initial results of a flood simulation using a new topographic parameterization surface produced from airborne lidar laser induced direction and ranging data copyright 2000 john wiley sons ltd

the energetics of a collapsing meridional overturning circulation a well studied example of natural climate variability is the impact of large freshwater input to the polar oceans simulating glacial melt release or an amplification of the hydrological cycle such forcing can reduce or entirely eliminate the formation of deep water in the polar latitudes and thereby weaken the atlantic meridional overturning circulation moc this study uses a series of idealized eddy permitting numerical simulations to analyze the energetic constraints on the atlantic ocean s response to anomalous freshwater forcing inthismodel thechangesinmocarenotcorrelatedwiththeglobalinputofmechanicalenergy both kinetic energy and available potential energy ape increase with northern freshwater forcing while the moc decreases however a regional analysis of ape density supports the notion that local maxima in ape density control the response of the moc to freshwater forcing perturbations a coupling between ape input and changes in local density anomalies accounts for the difference in time scales between the recovery and collapse of the moc

a process based analysis of ocean heat uptake in an aogcm with an eddy permitting ocean component about 90 of the anthropogenic increase in heat stored in the climate system is found in the oceans therefore it is relevant to understand the details of ocean heat uptake here we present a detailed process based analysis of ocean heat uptake ohu processes in higem1 2 an atmosphere ocean general circulation model with an eddy permitting ocean component of 1 3 resolution similarly to various other models higem1 2 shows that the global heat budget is dominated by a downward advection of heat compensated by upward isopycnal diffusion only in the upper tropical ocean do we find the classical balance between downward diapycnal diffusion and upward advection of heat the upward isopycnal diffusion of heat is located mostly in the southern ocean which thus dominates the global heat budget we compare the responses to a 4xco2 forcing and an enhancement of the windstress forcing in the southern ocean this highlights the importance of regional processes for the global ocean heat uptake these are mainly surface fluxes and convection in the high latitudes and advection in the southern ocean mid latitudes changes in diffusion are less important in line with the cmip5 models higem1 2 shows a band of strong ohu in the mid latitude southern ocean in the 4xco2 run which is mostly advective by contrast in the high latitude southern ocean regions it is the suppression of convection that leads to ohu in the enhanced windstress run convection is strengthened at high southern latitudes leading to heat loss while the magnitude of the ohu in the southern mid latitudes is very similar to the 4xco2 results remarkably there is only very small global ohu in the enhanced windstress run the wind stress forcing just leads to a redistribution of heat we relate the ocean changes at high southern latitudes to the effect of climate change on the antarctic circumpolar current acc it weakens in the 4xco2 run and strengthens in the wind stress run the weakening is due to a narrowing of the acc caused by an expansion of the weddell gyre and a flattening of the isopycnals which are explained by a combination of the wind stress forcing and increased precipitation

contribution of enhanced antarctic bottom water formation to antarctic warm events and millennial scale atmospheric co2 increase abstract during marine isotope stage 3 the atlantic meridional overturning circulation amoc weakened significantly on a millennial time scale leading to greenland stadials ice core records reveal that each greenland stadial is associated with a warming over antarctica so called antarctic isotope maximum aim and that atmospheric co 2 increases with antarctic temperature during the long greenland stadials here we perform transient simulations spanning the period 50 34 ka b p with two earth system models loveclim and the uvic escm to understand the possible link between changes in the amoc changes in high latitude southern hemispheric climate and evolution of atmospheric co 2 we find that oceanic carbon releases due to the amoc resumption during stadial interstadial transitions lead to an atmospheric co 2 increase however the atmospheric co 2 increases observed during the first parts of aim12 47 6 ka b p and aim8 39 8 ka b p occur during periods of weak amoc hs5 and hs4 respectively and could instead be explained by enhanced antarctic bottom water transport enhanced antarctic bottom water formation is shown to effectively ventilate the deep pacific carbon and lead to co 2 outgassing into the atmosphere in addition changes in the amoc alone are not sufficient to explain the largest antarctic isotope maxima namely aim12 and aim8 stronger formation of antarctic bottom water during aim12 and aim8 would enhance the southern high latitude warming and lead to a better agreement with high southern latitude paleoproxy records the robustness of this southern warming response is tested using an eddy permitting coupled ocean sea ice model we show that stronger antarctic bottom water formation contributes to southern ocean surface warming by increasing the southern ocean meridional heat transport

the application of computational fluid dynamics to natural river channels three dimensional versus two dimensional approaches this paper addresses the recent trend in fluvial geomorphology towards using computational fluid dynamics to explore the adjustment between flow processes sediment transport and river channel morphology it aims to evaluate the extent to which three dimensional 3d models improve predictive ability and prediction utility compared to two dimensional 2d applications this is achieved through comparing the predictions of both 3d and 2d models with high quality field data identical boundary conditions obtained from a confluence within a gravel bed river system with high relative roughness are defined for each model evaluation of the 3d model suggests that there is a fundamental limitation upon model predictive ability due to problems of specifying topographic complexity however comparison with the 2d model shows that the 3d model has a higher predictive ability particularly if the 2d model is not corrected for the effects on flow structure of secondary circulation further the 3d model provides more reliable estimates of bed shear stress and other more useful information such as the three dimensional flow field important for mixing processes this suggests that there is significant merit in the move towards 3d models but that research is required to incorporate methods developed in other fields for dealing with boundary condition uncertainties

tracking geomorphic signatures of watershed suburbanization with multitemporal lidar abstract urban development practices redistribute surface materials through filling grading and terracing causing drastic changes to the geomorphic organization of the landscape many studies document the hydrologic biologic or geomorphic consequences of urbanization using space for time comparisons of disparate urban and rural landscapes however no previous studies have documented geomorphic changes from development using multiple dates of high resolution topographic data at the watershed scale this study utilized a time series of five sequential light detection and ranging lidar derived digital elevation models dems to track watershed geomorphic changes within two watersheds throughout development 2002 2008 and across multiple spatial scales 0 01 1 km 2 development induced changes were compared against an undeveloped forested watershed during the same time period changes in elevations slopes hypsometry and surface flow pathways were tracked throughout the development process to assess watershed geomorphic alterations results suggest that development produced an increase in sharp topographic breaks between relatively flat surfaces and steep slopes replacing smoothly varying hillslopes and leading to greater variation in slopes examinations of flowpath distributions highlight systematic modifications that favor rapid convergence in unchanneled upland areas evidence of channel additions in the form of engineered surface conduits is apparent in comparisons of pre and post development stream maps these results suggest that topographic modification in addition to impervious surfaces contributes to altered hydrologic dynamics observed in urban systems this work highlights important considerations for the use of repeat lidar flights in analyzing watershed change through time novel methods introduced here may allow improved understanding and targeted mitigation of the processes driving geomorphic changes during development and help guide future research directions for development based watershed studies

uranium thorium series radionuclides in brines and reservoir rocks from two deep geothermal boreholes in the salton sea geothermal field southeastern california naturally occurring u and th series radionuclides have been analyzed in high temperature brines 300 c 25 wt dissolved solids and associated rocks from two deep geothermal wells located on the northeastern margin of the salton sea geothermal field ssgf these data are part of a study of the ssgf as a natural analog of possible radionuclide behavior near a nuclear waste repository constructed in salt beds and permit evaluation of some characteristics of water rock interaction in the ssgf rock brine concentration ratios rc dpm g rock dpm g brine were found to vary from near unity for isotopes of ra pb and rn to about 5 105 for 232th the high sorptivity of 232th is closely followed by that of 238u and 234u rc 5 104 suggesting that u is retained in the 4 oxidation state by the reducing conditions in the brines the relatively high solubility of 210pb and 212pb is attributed to formation of chloride complexes while the high ra solubility is attributed to chloride complexing a lack of suitable adsorption sites due to the high brine salinity and temperature and the reducing conditions that prevent mno2 and raso4 from forming the 228ra226ra ratios in the brines are approximately equal to those of their parents 232th230th in associated rocks indicating that ra equilibration in the brine rock system is achieved within the mean life of 228ra 8 3 years the 224ra228ra ratios in these brines are about 0 7 indicating that either 1 brine composition is not homogeneous and 224ra decays in fracture zones deficient in ra and th as the brine travels to the wellhead or 2 ra equilibration in the brine host rock system is not complete within the mean life of 224ra 5 2 days because the desorption of 224ra from the solid phase is impeded the 228ac228ra activity ratio in the ssgf brines studied is 0 1 and from this ratio the residence time of 228ac in the brine before sorption onto solid surfaces is estimated to be 70 minutes indicating the potential for rapid removal of reactive isotopes fom brines the brine is greatly enriched in 226ra 2 3 dpm g about 104 105 times that of its parent 230th while reservoir rocks are about 10 deficient in 226ra relative to 230th material balance calculations for 2226ra and 18o suggest that brines reside in the reservoir for 102 103 years that the ssgf formed 10 000 40 000 years b p and that porosity cannot be more than 20