source type and extent of inorganic contamination within the birmingham urban aquifer system uk a survey of the inorganic quality of the groundwater of the birmingham triassic sandstone aquifer was carried out by sampling seventy 80 150 m deep industrial abstraction boreholes 11 shallow monitoring piezometers two submerged tunnels and two flooded industrial basements and a set of trial pits borehole logging and historical data were also obtained given that the city of birmingham is as long established as most industrial conurbations in the world the degree of groundwater inorganic contamination as indicated by abstraction well samples is not excessive out of the 28 determinands measured only no 3 and ba2 consistently approach and exceed their european community maximum admissible concentrations standards for drinking water and the barium is being supplied by the aquifer rather than having an anthropogenic source however a few abstraction boreholes have highly contaminated groundwaters with for example milligram per litre levels of heavy metals in addition there is a correlation between land use and chemistry with the highest salinity sulphate chloride sodium boron and total heavy metal concentrations being associated with metal working sites high concentrations of heavy metals and nh 4 are unexpected in the near neutral ph triassic sandstone groundwaters given the high sorption capacity of the sandstone it is concluded that one reason for the occasionally high concentrations observed is the presence of very locialized high concentration recharge data from shallow piezometers confirm the considerable degree of heterogeneity in groundwater quality on a small scale the pollution is mainly from point sources sampling from piezometers tunnels and basements demonstrates that the groundwater concentrations at shallow depths are often much higher than the pumped water analyses suggest however nitrate groundwaters appear to vary much less with depth than other species reflecting a longer history of supply and a wider range of sources geophysical logging and sampling of well columns and other observations indicate that the intermittent pumping of abstraction wells results in the pumped water quality being biased towards the shallower high concentrations groundwaters rather than being a uniform mixture from all screened depths historical data show various trends and these can be related to local hydrogeology land use and abstraction history comparisons of organic and inorganic pollution show that distributions are very different reflecting differences in physical transport processes chemical interactions and histories of chemical usage

dust deposition pulses to the eastern subtropical north atlantic gyre does ocean s biogeochemistry respond 1 enhancement of primary and export production following dust deposition pulses is well established for high nutrient low chlorophyll regions but the effect of atmospheric dust on the biogeochemistry of oligotrophic gyre regions remains unclear here we report atmospheric dust concentrations measured on gran canaria canary islands concomitantly with upper water biogeochemistry at the oligotrophic time series station estoc european station for time series in the ocean canary islands during a 2 year period from winter 1997 to 1999 estoc is located in the eastern subtropical atlantic gyre about 100 km north of gran canaria and 500 km west of the sahara and receives aeolian dust episodically mainly in winter and summer we found a close correlation of the magnitude of atmospheric dust concentration in winter with the magnitude of downward particle flux at estoc mainly due to a relative increase in lithogenic matter and carbonate sedimentation higher aerosol concentration was not accompanied by higher primary or export production however indicating that phytoplankton production remained unaffected by atmospheric nitrogen supply on a seasonal or yearly timescale however by estimating bioavailable iron input and the need of the phytoplankton population we found that the highly episodic dust pulses might exert a feast and famine effect on the phytoplankton despite the high lithogenic matter input carbonate mainly stemming from coccolithophorids exceeded in importance the role of lithogenic matter as ballasting agent of sinking organic matter

a combined in situ oxygen silicon isotopic and fluid inclusion study of a chert sample from onverwacht group 3 35ga south africa new constraints on fluid circulation abstract cherts have been extensively used as a proxy of precambrian environmental conditions of the earth cherts from the onverwacht group 3 5 3 3 ga south africa are considered as well preserved and have been used as a paleo oceanic thermometer especially by using the oxygen isotope composition of the chert nevertheless there are several lines of evidence size and number of the quartz veins that fluids circulated through these cherts after their deposition these cherts are composed mainly of microquartz with large quartz veins 100 m and iron carbonates as ankerites a combined study of oxygen silicon and fluid inclusions study have been performed on one chert sample from the onverwacht group in order to assess the effect of these fluid circulations on the chert oxygen and silicon isotopic compositions in situ oxygen and silicon isotopic compositions on microquartz and vein quartz were measured at high spatial resolution using a multicollector cameca 1270 ion probe crpg cnrs nancy moreover fluid inclusions present in the quartz veins are considered to determine the origin and conditions of the fluid circulation three types of primary fluid inclusions carbonic lc aqueous carbonic fluids lc w and aqueous fluid lw have been observed the temperatures of this fluid circulation were determined by microthermometry and using quartz carbonate pair thermometry at between 200 c and 300 c fluid pressures range from 100 mpa to 30 mpa which correspond to depths ranging from 4 to 1 km this evolution could be related to an exhumation associated with a dilution and cooling process this fluid circulation could be associated to the gold bearing fluid responsible of the sheba fairview ore system dated at 3074 6 ma the results of the isotopic study show that these fluid circulations homogenised the oxygen isotope composition but not the entire silicon isotope composition of the microquartz the 18 o value calculated for the fluid show that it equilibrated with carbonate rocks and is similar to the composition of the gold bearing fluid the silicon isotope composition of the microquartz allows determination of the initial 30 si of the microquartz precursor this precursor has been precipitated from a hydrothermal fluid hence a combined 18 o 30 si and fluid inclusion study allows the conditions of the fluid circulation to be constrained and the origins of chert to be determined

transport and dispersal of organic debris peat blocks in upland fluvial systems this paper assesses the mechanisms and pathways by which peat blocks are eroded and transported in upland fluvial systems observations and experiments from the north pennines uk have been carried out on two contrasting river systems mapping of peat block distributions and appraisal of reach based sediment budgets clearly demonstrates that macro size peat is an important stream load component in small streams block sizes can approximate the channel width and much of the peat is transported overbank local peat jams and associated mineral deposition may provide an important component of channel storage in larger systems peat blocks rapidly move down channel and undergo frequent exchanges between bed and bank storage results of peat block tracing using painted blocks indicate that once submerged blocks of all sizes are easily transported and blocks break down rapidly by abrasion vegetation and bars play an important role in trapping mobile peat in smaller streams large block transport is limited by channel jams smaller blocks are transported overbank but exhibit little evidence of downstream fining in larger rivers peat blocks are more actively sorted and show downstream reduction in size from source a simple model relating peat block diameter dp to average flow depth d suggests three limiting transport conditions flotation dp d 2 and deposition dp d 2 experiments demonstrate that peat block transport occurs largely by rolling and floating and the transport mechanism is probably controlled by relative flow depth d dp ratio transport velocity varies with transport mechanism rolling is the slowest mode and transport lengths increase as flow depth increases abrasion rates vary with the transport mechanism rolling produces greater abrasion rates and more rounded blocks abrasion rates vary from 0 to 10 g m 1 for blocks ranging in mass from 10 to 6000 g copyright 2001 john wiley sons ltd

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

effect of surface roughness on bidirectional reflectance of antarctic snow the angular pattern of sunlight reflected by snow is altered by surface roughness which in the interior of antarctica is usually in the form of meter scale longitudinal erosional features sastrugi whose axes align with the direction of strong winds the bidirectional reflectance distribution function brdf changes over the course of a day as the solar azimuth changes relative to the sastrugi axis the normalized brdf or anisotropic reflectance factor r was measured at south pole station from a 22 m tower at 600 660 and 900 nm wavelengths the r pattern was similar at the three wavelengths it probably varies little from 300 to 900 nm measurements were made at solar zenith angles 0 from 67 to 90 over the full range of viewing zenith angle r azimuth angle between sun and view and azimuth angle between sun and sastrugi sas variation of r with sas was notable sastrugi oriented perpendicular to the solar beam cause a reduction of the forward peak and sastrugi at an oblique angle cause r to lose its symmetry about the solar azimuth however the effects of sastrugi are mostly restricted to large viewing zenith angles so remote sensing of albedo and atmospheric properties can be carried out accurately without knowledge of sastrugi height and orientation if only near nadir views are used this recommendation is opposite that for observations of broken clouds over dark surfaces for which large r is preferred a parameterization of r is developed valid for viewing angles r 50 sastrugi can cause a reduction of the snow albedo by altering the angle of incidence and by trapping of photons for the small sastrugi of the antarctic plateau the albedo is unaffected at visible wavelengths but can be reduced by a few percent at near infrared wavelengths when the sun is low

sediment delivery from agricultural land to rivers via subsurface drainage diffuse sources of sediment and sediment associated nutrients are of increasing environmental concern because of their impacts on receiving water courses the aim of the research reported here was to monitor the outflow from four field land drains at two farms in the english midlands in order to estimate the quantity of sediment delivered to the local rivers and the most likely sources and processes involved a multiparameter sediment unmixing model was employed using environmental magnetic geochemical and radionuclide tracers in order to determine the most likely origin of sediments transported through the drains results demonstrated that there was a generally linear relationship between drainflow sediment loss and drainflow volume and that the majority 70 of the sediment exported from the drains was derived from topsoil macropore flow through heavily cracked soils is supported by the data to be the most likely means of sediment delivery to the drains in one catchment drains contributed over 50 of the annual sediment budget spatial and temporal variations in the sources of sediment reaching one drain outlet were investigated in detail a link between soil moisture deficit smd and the frequency of high intensity rainfall events was used to explain the appearance and persistence of a new sediment source in this drain after october 1998 it is concluded that field drains have the potential to be significant conduits of sediment and agrochemicals in a wide variety of environments in the uk it is also suggested that this potential may increase if projected climate change leads to more intense rainfall events and increases in smd across a greater area of the uk

measurement and parameterization of albedo variations at haut glacier d arolla switzerland spatial and temporal variations of surface albedo on haut glacier d arolla switzerland during the 1993 and 1994 ablation seasons are described correlation and regression analyses are used to explain the albedo variations in terms of independent meteorological and surface property variables parameterizations are developed which allow estimation of albedo variation in surface energy balance models snow albedo is best estimated from accumulated daily maximum temperatures since snowfall on deep snow 0 5 cm w e depth a logarithmic function is used while on shallow snow 0 5 cm w e depth an exponential function is used to enable the albedo to decay to the underlying ice or debris albedo the transition from deep to shallow snow is calculated as a function of decreasing snow depth combined r 2 0 65 this new parameterization performs better than earlier schemes because accumulated daily maximum temperatures since snowfall correlate strongly with snow grain size and impurity concentration the main physical controls on snow albedo ice albedo may be parameterized by its relationship to elevation r 2 0 28 but this approach results in only a small improvement over the assumption of a constant mean ice albedo

spatial and temporal variations of albedo on nine glaciers in western china from 2000 to 2011 this research demonstrates the spatiotemporal variations of albedo on nine glaciers in western china during 2000 2011 by the albedo derived from two types of datasets landsat tm etm images and mod10a1 product then the influence factors of glacier albedo and its relationship with glacier mass balance are also analyzed by the correlation approach which is frequently used in geostatistics the paper finds that there are different spatiotemporal variations over the glaciers in western china 1 for a single glacier the albedo varies gently with altitude on its tongue and increases fast in the middle part while in the accumulation zones the albedo value appears in the form of fluctuation this could provide a quantitative method to retrieve the snowline by determining the threshold albedo value of snowpack and bare ice 2 for the glaciers in western china the albedo decreases with distance to the center of tibetan plateau tp this may relate to the elevation of glacier for the speed of glacier retreat highly depends on air temperature 3 in the summer period albedo on most glaciers declines over the last 12years and it decreases much faster in southeastern tp than other regions for which air temperature overwhelms the black carbon concentration in addition the trend of glacier albedo in summer is greatly correlated with that of measured glacier mass balance which implies that the long term albedo datasets by remote sensing technology could be used to monitor and predict the change of glacier mass balance in the future 2013 john wiley sons ltd

convergent tracer tests in multilayered aquifers the importance of vertical flow in the injection borehole 1 a mathematical model describing the steady state flows in a forced gradient tracer test between an injection and pumping borehole in a multilayered sandstone aquifer has been developed that includes the effect of vertically variable background heads a second model describing the recovery of tracer from a layer in which there are discharges due to vertical flow in the injection borehole is also presented application of the models to field tracer test data indicates that the observed recoveries which are not proportional to the abstraction rate in each layer are consistent with the hydraulic behavior of the aquifer when natural vertical head gradients are taken into account investigation with the models illustrates that the vertical distribution of tracer recovery depends strongly upon the background heads and that tracer tests conducted in the same aquifer but at different times may interrogate different aquifer layers it is also shown generally that for a given abstraction rate the vertical distribution of tracer recovery in small scale tracer tests is controlled largely by the transmissivity distribution but that as the spatial scale of the test increases the distribution of recovery becomes proportional to the discharges from the injection borehole because of vertical flows within it which may be natural or induced by pumping in the monitoring borehole uncertainties inherent in the design of forced gradient tracer tests in multilayered aquifers and the problems of applying the results of such tests to natural gradient contaminant migration are discussed

effects of clay minerals on the aggregation and subsequent settling of marine synechococcus cyanobacteria are considered to play an important role in the oceanic biological carbon pump especially in oligotrophic regions but as single cells are too small to sink their carbon export has to be mediated by aggregate formation and possible consumption by zooplankton producing sinking fecal pellets here we study the aggregation and subsequent settling of the ubiquitous marine picocyanobacterium synechococcus as a model organism in roller tanks and investigate the effects of the clays kaolinite and bentonite in a series of concentrations we found that 1 synechococcus cells formed aggregates as large as 1 4 mm in diameter that sank at velocities of up to 440 m d 21 and 660 m d 21 with and without ballasting clays respectively 2 clay minerals increased the number and reduced the size of aggregates and their ballasting effects increased the excess density and sinking velocity of aggregates 3 kaolinite with its lower cation exchange capacity resulted in smaller and slower sinking aggregates compared to bentonite and 4 based on our experimental conditions synechococcus could potentially export carbon 2 3 times of that contained in their cells via aggregation likely due to the scavenging of transparent exopolymer particles and dissolved organic matter the presented results have relevance for our understanding of the role of cyanobacteria in the ecology and biogeochemistry in today s ocean and also elucidate mechanisms of carbon export in the early proterozoic ocean

retreating alpine glaciers increased melt rates due to accumulation of dust vadret da morteratsch switzerland the automatic weather station aws on the snout of the vadret da morteratsch switzerland has delivered a unique 12 year meteorological dataset from the ablation zone of a temperate glacier this dataset can be used to study multi annual trends in the character of the surface energy budget since 2003 there has been a substantial darkening of the glacier tongue due to the accumulation of mineral and biogenic dust the typical surface albedo in summer has dropped from 0 32 to 0 15 we have analysed the implications of the lowered albedo for the energy balance and the annual ablation for the 4 year period 2003 06 the decreased albedo caused an additional removal of about 3 5 m of ice calculations with an energy balance model show that the same increase in ablation is obtained by keeping the ice albedo fixed to 0 32 and increasing the air temperature by 1 7 k our analysis confirms that for retreating glaciers the deposition of dust from exposed side moraines on the glacier surface constitutes an important feedback mechanism the mineral dust stimulates the growth of algae lowers the surface albedo enhances the melt rates and thereby facilitates the further retreat of the glacier snout

recharge velocity and geochemical evolution for the permo triassic sherwood sandstone northern ireland the triassic sherwood sandstone group is a major european aquifer system it is also the principal groundwater source in northern ireland however key aspects of its regional hydrogeology such as age distribution and geochemical evolution remain largely unknown here the groundwater geochemistry and isotopic composition were investigated in order to evaluate groundwater recharge and flow processes in a complex regional hydrogeological setting the dominant geochemical processes such as dissolution of carbonate cements were determined from the major and trace element chemistry stable and radio isotope measurements were taken as residence time and flow path indicators and together with physical and geochemical groundwater modelling revealed groundwater ages of up to 9000 years the importance of infiltration from overland flow from springs deriving water from the adjacent cretaceous chalk aquifer and subsequently re infiltrating into the sherwood sandstone was confirmed in addition evidence was found of a slow recharge component through low conductivity mudstones that yielded significant groundwater resident times throughout the lagan valley these findings provide improved understanding of groundwater flow processes in northern ireland and serve as an example of methods that can be applied to water management elsewhere

mechanisms controlling the silicon isotopic compositions of river waters it has been proposed that silicon si isotopes are fractionated during weathering and biological activity leading to heavy dissolved riverine compositions in this study the first seasonal variations of stable isotope compositions of dissolved riverine si are reported and compared with concomitant changes in water chemistry four different rivers in switzerland were sampled between march 2004 and july 2005 the unique high resolution multi collector icp ms nu1700 has been used to provide simultaneous interference free measurements of 28si 29si and 30si abundances with an average limiting precision of 0 04 on 30si this precision facilitates the clarification of small temporal variations in isotope composition the average of all the data for the 40 samples is 30si 0 84 0 19 1 sd despite significant differences in catchment lithologies biomass climate total dissolved solids and weathering fluxes the averaged isotopic composition of dissolved si in each river is strikingly similar with means of 0 70 0 12 for the birs 0 95 0 22 for the saane 0 93 0 12 for the ticino and 0 79 0 19 for the verzasca however the 30si undergoes seasonal variations of up to 0 6 comparisons between 30si and physico chemical parameters such as the concentration of dissolved si and other cations the discharge of the rivers and the resulting weathering fluxes permits an understanding of the processes that control the si budget and the fate of dissolved si within these rivers the main mechanism controlling the si isotope composition of the mountainous verzasca river appears to be a two component mixing between the seepage of soil ground waters with heavier si produced by clay formation and superficial runoff associated with lighter si during high discharge events a biologically mediated fractionation can be excluded in this particular river system the other rivers display increasing complexity with increases in the proportion of forested and cultivated landscapes as well as carbonate rocks in the catchment in these instances it is impossible to resolve the extent of the isotopic fractionation and contributed flux of si contributed by biological processes as opposed to abiotic weathering the presence of seasonal variations in si isotope composition in mountainous rivers provides evidence that extreme changes in climate affect the overall composition of dissolved si delivered to the oceans the oceanic si isotope composition is very sensitive to even small changes in the riverine si isotope composition and this parameter appears to be more critical than plausible changes in the si flux therefore concurrent changes in weathering style may need to be considered when using the si isotopic compositions of diatoms sponges and radiolaria as paleoproductivity proxies

characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks summary accurately identifying the position of vertical hydraulic conductivity k v contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow high resolution head profiles have identified the position and thickness of k v contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks this paper describes an experiment in which head profiles with the highest technically feasible resolution were obtained using westbay multilevel systems mls installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions mlss were installed to maximum depths between 90 and 260 m with 2 5 monitoring zones per 10 m head profiles were measured over multiyear periods the vertical component of hydraulic gradient i e vertical gradient was calculated for each pair of adjacent monitoring intervals in every mls and then categorized based on its repeatability to facilitate interpretation of k v contrasts and comparisons within boreholes between boreholes at the same site and between sites the head and vertical gradient profiles from all three sites display systematic i e simple geometric shapes defined by repeatable intervals of no to minimal vertical gradient indicating relatively high k v units bounded by shorter depth intervals with large up to 50 m m vertical gradients indicating relatively low k v units the systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations the low k v units were typically thin with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic geophysical and horizontal hydraulic conductivity data hence the position and thickness of units with contrasting k v would not be evident if mlss with the conventional number of monitoring zones had been used furthermore the detailed profiles can be strongly diagnostic of hydrogeologic unit boundaries or layers and can be used to improve the quantitative assessment of flow system conditions that is foundational to understanding contaminant plume migration

association of sinking organic matter with various types of mineral ballast in the deep sea implications for the rain ratio 1 we compiled and standardized sediment trap data below 1000 m depth from 52 locations around the globe to infer the implications of the armstrong et al 2002 ballast model to the ratio of organic carbon to calcium carbonate in the deep sea the rain ratio we distinguished three forms of mineral ballast calcium carbonate opal and lithogenic material we concur with armstrong et al 2002 that organic carbon sinking fluxes correlate tightly with mineral fluxes based on the correlations seen in the trap data we conclude that most of the organic carbon rain in the deep sea is carried by calcium carbonate because it is denser than opal and more abundant than terrigenous material this analysis explains the constancy of the organic carbon to calcium carbonate rain ratio in the deep sea today and argues against large changes in the mean value of this ratio in the past however sediment trap data show variability in the ratio in areas of high relative calcium carbonate export mass caco3 mass ratio 0 4 unexplainable by the model leaving open the possibility of regional variations in the rain ratio in the past

pollution related acidification in the urban aquifer birmingham uk abstract comparison of groundwater quality data ten years apart and sampling of shallow level water and soil gas co 2 indicates that the groundwaters below birmingham are becoming more acidic six potential causes are considered 1 rise of water level into the carbonate poor upper levels of the sandstone aquifer 2 oxidation of the quaternary deposits overlying the aquifer 3 inorganic acid spills 4 other acidic recharge 5 oxidation of inorganic pollutants 6 degradation of industrial organic pollutants chemical and hydrogeological data suggest that 3 5 and 6 are dominant in different parts of the city the rate of fall in ph of 0 6 units over ten years is worrying with regard to increased solubility of toxic metals

spatial distribution of surface ablation in the terminus of rhonegletscher switzerland the spatial pattern of glacier surface melt was measured with a resolution of 20 100 m within a region extending 1 km up glacier from the terminus of rhonegletscher switzerland the melt rate was monitored from 6 july to 6 september 2009 using 44 ablation stakes we also measured the surface albedo near the stakes to investigate the importance of this parameter for the melt rate distribution the melt rate varied from 32 8 to 71 9 mm w e d 1 in the study area our measurements suggest that the spatial variation of the melt rate can be explained by 1 shading of the ice surface by neighbouring mountains 2 surface albedo and 3 effects of microclimate e g radiation from side walls on the surface energy balance the observed melt rate distribution was compared to the results of a temperature index melt model which takes into account shading of direct solar illumination but not the other two effects the model reproduces some important features of the field data but its spatial variations are generally less than the measured values our study shows the importance of albedo and other local conditions in the accurate estimation of the small scale melt rate distribution

a method for monitoring glacier mass balance using satellite albedo measurements application to vatnajskull iceland we compare satellite albedo images of vatnajokull iceland with mass balance measurements for the years 1991 99 we find that the equilibrium line is mostly not visible when it is located above its position of the previous year s equilibrium line detection is further hindered by clouds and a gradual transition between ice and firn or snow consequently firn line elevation at the end of the melting season is not particularly useful for estimating the annual mass balance instead we propose to study the mean albedo of the entire ice cap throughout the melting season so that all available information about the surface albedo is taken into account the mean net potential global radiation which can be estimated from the mean surface albedo alone both depends on and influences summer melt it also depends on winter precipitation and integrated over the melting season is found to relate linearly to the specific mass balance b r 0 87 and 0 94 for different outlets of vatnajokull b can be estimated quantitatively when this relation is known and qualitatively when it is not the uncertainty in the satellite derived value of b is 0 5 0 8 m w e which for vatnajokull corresponds to about 27 of the interannual variability of b

descending particles from the atmosphere to the deep ocean a time series study in the subtropical ne atlantic 1 the transport ways of organic matter into the deep ocean are still under debate lithogenic particles deliver nutrients to the surface boost biological production and impact on carbon export this study focuses on the transfer of lithogenic particles from the atmosphere to the deep ocean and its physical and biological interactions during their descent through the water column a clear coupling between atmospheric dust occurrence and deep sea lithogenic particle fluxes at 2000 m depth was observed in the subtropical ne atlantic 33 n 22 w this has never been demonstrated before for this site far away from the african continental slope and with no lateral influx of particles present the atmospheric signal transmission to the deep ocean lies in the range of one to two months the presented data demonstrate the dependence of lithogenic deep sea fluxes on the positioning in the ocean and on particle residence times in the water column

distributed modeling of ablation 1996 2011 and climate sensitivity on the glaciers of taylor valley antarctica here the mcmurdo dry valleys of antarctica host the coldest and driest ecosystem on earth which is acutely sensitive to the availability of water coming from glacial runoff we modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass balance observations collected in taylor valley sublimation was the primary form of mass loss over much of the ablation zones except for near the termini where melt primarily below the surface dominated microclimates in 10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces in contrast the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation the model systematically underpredicted ablation for the final 5 years studied possibly due to an increase of windblown sediment surface mass balance sensitivity to temperature was 0 02 m w e k 1 which is among the smallest magnitudes observed globally we also identified a high sensitivity to ice albedo with a decrease of 0 02 having similar effects as a 1 k increase in temperature and a complex sensitivity to wind speed

mineral ballast and particle settling rates in the coastal upwelling system off nw africa and the south atlantic the ocean off nw africa is the second most important coastal upwelling system with a total annual primary production of 0 33 gt of carbon per year carr in deep sea res ii 49 59 80 2002 deep ocean organic carbon fluxes measured by sediment traps are also fairly high despite low biogenic opal fluxes due to a low supply of dissolved silicate from subsurface waters the ocean off nw africa is characterized by predominantly carbonate secreting primary producers i e coccolithophorids these algae which are key primary producers since millions of years are found in organic and chlorophyll rich zooplankton fecal pellets which sink rapidly through the water column within a few days particle flux studies in the mauretanian upwelling area cape blanc confirm the hypothesis of armstrong et al deep sea res ii 49 219 236 2002 who proposed that ballast availability e g of carbonate particles is essential to predict deep ocean organic carbon fluxes the role of dust as ballast mineral for organic carbon however must be also taken into consideration in the coastal settings off nw africa there high settling rates of larger particles approach 400 m day 1 which may be due to a particular composition of mineral ballast an assessment of particle settling rates from opal production systems in the southern ocean of the atlantic sector in contrast provides lower values consistent with the assumptions of francois et al global biogeochem cycles 16 4 1087 2002 satellite chlorophyll distributions particle distributions and fluxes in the water column off nw africa as well as modelling studies suggest a significant lateral flux component and export of particles from coastal shelf waters into the open ocean these transport processes have implications for paleo reconstructions from sediment cores retrieved at continental margin settings

vertical groundwater flow in permo triassic sediments underlying two cities in the trent river basin uk the vertical component of groundwater flow that is responsible for advective penetration of contaminants in sandstone aquifers is poorly understood this lack of knowledge is of particular concern in urban areas where abstraction disrupts natural groundwater flow regimes and there exists an increased density of contaminant sources vertical hydraulic gradients that control vertical groundwater flow were investigated using bundled multilevel piezometers and a double packer assembly in dedicated boreholes constructed to depths of between 50 and 92 m below ground level in permo triassic sediments underlying two cities within the trent river basin of central england birmingham nottingham the hydrostratigraphy of the permotriassic sediments indicated by geophysical logging and hydraulic packer testing demonstrates considerable control over observed vertical hydraulic gradients and hence vertical groundwater flow the direction and magnitude of vertical hydraulic gradients recorded in multilevel piezometers and packers are broadly complementary and range within error from 0 1 to 2 0 7 groundwater is generally found to flow vertically toward transmissive zones within the hydrostratigraphical profile though urban abstraction from the sherwood sandstone aquifer also influences observed vertical hydraulic gradients bulk downward darcy velocities at two locations affected by abstraction are estimated to be in the order of several metres per year consistency in the distribution of hydraulic head with depth in permo triassic sediments is observed over a one year period and adds support the deduction of hydrostratigraphic control over vertical groundwater flow q 2003 elsevier b v all rights reserved

interactive aggregation and sedimentation of diatoms and clay sized lithogenic material monospecific diatom cultures thalassiosira punctigera and skeletonema costatum were incubated in rotating cylinders together with clay suspensions present in a range of concentrations 5 100 mg kaolinite l 21 and as different minerals 50 mg l 21 kaolinite smectite illite and clay sized quartz powder the addition of lithogenic suspensions to diatom cultures accelerated the formation of visible aggregates in the roller tanks by a factor of 3 aggregate size decreased and density increased proportionally to the amount of kaolinite added to the diatom cultures in the presence of kaolinite and illite aggregate sizes were smaller and sinking rates lower than in the presence of smectite and quartz the influence of lithogenic matter on the sinking velocities of aggregates was ambiguous compound aggregates sank faster with increasing amounts of lithogenic matter present in cultures of t punctigera until a certain ratio between lithogenic and biogenic material was reached further increasing the amount of lithogenic matter did not increase sinking rates significantly in contrast increasing the concentration of kaolinite added to cultures of s costatum could decrease sinking velocities of the evolving compound aggregates this nonlinear behavior is argued to be primarily a function of aggregate composition on aggregate sizes and excess densities although the possibility of a mutual acceleration of vertical flux of algae and clay is confirmed the results show that the presence of lithogenic material could also decrease the downward flux of phytoplankton biomass rapid sinking of phytoplankton derived organic carbon via sedimentation of aggregates contributes significantly to the vertical transport of marine particulate organic carbon poc a process known as the biological pump volk and hoffert 1985 rapid sinking of clay sized lithogenic material can be inferred from sediment trap data wefer 1989 laboratory studies on marine aggregate formation and properties have focused on pure phytoplankton aggregates kiorboe et al 1990 riebesell et al 1991 kiorboe and hansen 1993 or on monomineralic clay aggregates kranck 1973 however coaggregation of phytoplankton and clay is a familiar phenomenon in aquatic environments first drawings of marine snow show sundry marine organisms and mineral grains embedded in a mucous matrix which dominates the aggregates by volume and appears to hold the solid compounds together tsujita 1953 avnimelech et al 1982 described enhanced floc formation and sedimentation of freshwater algae in the presence of clay and vice versa the fact that lithogenic and biogenic particles are often found in deep sediment traps during the same time interval in spite of independent occurrence in the surface water also suggests coaggregation and cosedimentation of these particles deuser et al 1983 wefer 1989 ittekkot 1993 while small amounts of both biogenic and lithogenic particles are present in all marine environments areas with elevated concentrations of lithogenic particles often show a high phytoplankton abundance at the same time and are thus particularly interesting in terms of interaction between phytoplankton and lithogenic material examples for marine en

residence time indicators in groundwater the east midlands triassic sandstone aquifer the east midlands triassic sherwood sandstone aquifer which has been the subject of detailed radiometric age studies is used to investigate both inert and reactive constituents of groundwater as indicators of residence time detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data though without radiocarbon several inert indicators are defined including the isotopic ratios 18o 2h 36cl noble gas ratios as well as the halogen elements cl br f i and their element ratios these form a group of essentially unreactive tracers primarily reflecting changing rainfall inputs and palaeoclimatic conditions except at outcrop where human impacts are also seen clearly the concentrations of cl mainly from atmospheric sources remain below 25 mg l 1 cl over a distance of some 30 km from outcrop reactive indicators the result of time dependent water rock interactions include 13c mg ca sr ca na cl and show diagnostic trends along the flow lines however the concentrations of certain trace elements li rb cs mn and mo which are not limited by solubility constraints show linear trends along the present day flow gradient this water rock interaction is taking place in groundwaters with low total mineralisation and it can be demonstrated that reactions involving these elements and isotopes are occurring entirely within the aquifer since high salinity groundwaters are found below the sherwood sandstone there is good correlation between some of the elements and 14c activities in the 1977 data set and this has been used to derive a concentration age relationship for the 1992 set of data a chemical timescale for the aquifer is then established using a li and b a combination of five trace elements the age of the fresh groundwater is thus shown to be up to 100 ka bp indicating the likelihood of semi continuous recharge during the devensian glacial period preceding the glacial maximum when no recharge occurred 10 20 ka bp this approach may be of value in extending groundwater dating beyond the radiocarbon timescale as well as interpreting sites where no radiocarbon data are available the scatter from the mean age line indicates those groundwaters which are derived from either rapid or slower than average flow zones within the aquifer as well as age stratification this stratification is borne out by a depth profile of groundwater from a new borehole near to outcrop which is shown by a combination of chemical and isotopic tracers to contain holocene overlying late pleistocene water

estimating the mass balance of vatnajokull iceland from noaa avhrr imagery we investigate the possibility of obtaining the mass balance of vatnajo kull iceland from us national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr albedo images for the years 1991 2002 de ruyter de wildt and others 2002 demonstrated that the mean potential absorbed radiation averaged over the melting season correlates well with the mean specific mass balance and that can be estimated from the evolution of the surface albedo here we improve the retrieval method of de ruyter dewildt and others 2002 by introducing the more realistic 6s atmospheric transfer model and by adding the latest narrowto broadband ntb albedo conversion equations bidirectional reflectance distribution functions for both ice and snow are used where appropriate we show that the choice of the ntb conversion equations greatly influences the calculated measured mass balance correlates well with if enough cloud free images can be found through the year and if the spatial variation in measured mass balances is high enough the correlation coefficient for all drainage basins combined is 0 92 with a residual standard deviation of 0 18mw e we present an estimated mass balance series for the whole of vatnajo kull based on our findings switching between different avhrr instruments over time may cause serious errors in the calculated mass balance

migration of contaminants in groundwater at a landfill a case study 2 groundwater monitoring devices abstract six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the borden landfill these include standpipe piezometers water table standpipes an auger head sampler suction type and positive displacement type multilevel point samplers and bundle piezometers with the exception of the first two each of these devices provides a means of obtaining vertical sample profiles of groundwater from a single borehole the auger head sampler which is a device that is attached to the cutting head of conventional continuous flight hollow stem augers yields samples from relatively undisturbed aquifer zones as the augers are advanced downward in the borehole from one depth of sampling to another this method is a rapid means of aquiring water quality profiles for mapping the distribution of a contaminant plume the other three profiling devices can be used to establish permanent networks for groundwater quality monitoring a suction type multilevel sampler consists of twenty or more narrow polyethylene or polypropylene tubes contained in a pvc casing that is capped at the bottom each tube extends to a different depth and is attached to a small screened sampling point that extends through the casing to draw water from the aquifer when suction is applied a positive displacement multilevel sampler is similar except that each sampling point is connected to a positive displacement pumping device located inside the pvc casing adjacent to the screen use of the suction type multilevel sampler is limited to zones where the water table is less than the suction lift depth of 8 or 9 m the positive displacement sampler can be used even if the water table is at a much greater depth a bundle piezometer consists of 1 2 cm o d flexible polyethylene tubes each with a short screened section at the bottom fastened as a bundle around a semi rigid center piezometer constructed of thick walled 2 cm o d pvc pipe in shallow water table areas water is withdrawn from each of the tubes and from the pvc piezometer by suction in areas with a deep water table samples are obtained by bailing with a narrow tube with a check valve on the bottom or by displacement using a double or triple tube gas drive sampler the positive displacement multilevel sampler or use of the gas drive samplers in the bundle piezometers provide the best opportunities for collecting samples that can be filtered and have preservatives added without the water being influenced excessively by degassing or by oxygen invasion networks of these three types of devices for multilevel groundwater monitoring were installed in the borden aquifer by means of hollow stem augers the devices are particularly well suited for use in aquifers composed of cohesionless sand or gravel that have little or no clay and groundwater flow that is primarily horizontal when 8 cm diameter hollow stem augers are used as many as eight polyethylene tubes are included conveniently in each bundle piezometer if augers with a larger hollow stem are used more tubes can be assembled in each bundle

lead contamination of fluvial sediments in an eroding blanket peat catchment over the last few years there has been growing concern over the mobilisation of anthropogenically derived atmospherically deposited pb from upland blanket peat soils to receiving surface waters the near surface layer of blanket peat soils of the peak district southern pennines uk is severely contaminated with high concentrations of pb erosion of peat soils in this upland area may be releasing large quantities of previously deposited pb into the fluvial system samples of fluvial sediments suspended floodplain streamside fan trash line and channel bed were collected from a severely eroding blanket peat catchment in the peak district in order to investigate pb contamination of fluvial sediments to determine the mechanism for fluvial pb transport and to determine if erosion of contaminated peat soils in the catchment is releasing pb into the fluvial system concentrations of pb associated with fluvial sediments are considerably higher than those in the catchment geology but not as high as those in peat soils in the catchment intra and inter storm variability in the pb content of suspended sediments can be explained by differences in organic matter content of these sediments and differences in erosion processes operating within the catchment high pb concentrations are associated with suspended sediments that have a high organic matter content the results of this study suggest that organic matter is the principle vector for sediment associated pb in the fluvial system erosion of contaminated peat soils in the peak district is releasing pb into the fluvial system the extent to which this is a problem in other peatland environments is an area requiring further research

evaluation of topographic effects in remotely sensed data abstract remotely sensed data are generally analyzed assuming flat terrain as the spectral signature of the ground depends upon the orientation of the surface slope the topography has to be considered for efficient radiometric corrections in mountainous regions in this paper we present a modelization of the atmospheric downward radiance at the ground level which gives us the relative contributions of the direct solar beam and of the diffused radiation for different atmospheric turbidities and different solar incidence angles lastly we estimate the influence of the topography on these contributions to show up which effects can be neglected

seasonality of surface water properties and particle flux along a productivity gradient off nw africa abstract three stations along a productivity gradient north of the canary islands were investigated for surface water properties particle flux and composition biogenic and lithogenic components and stable nitrogen isotope composition 15n and export production investigation sites along the east west transect off the nw african upwelling margin included the european station for time series in the ocean canary islands estoc one location contiguous to the nw african upwelling zone in the eastern boundary current ebc and one station north of the island la palma lp the seasonality of surface water properties along the transect was mainly influenced by the winter cooling and simultaneous phytoplankton maximum and in addition at ebc by nearby upwelling accordingly particle flux and composition along the transect were closely linked to the winter bloom sedimentation and upwelling related enhanced plankton biomass stemming from the primary upwelling and the cape yubi filament at ebc during all seasons particle flux was highest at ebc and had the highest contribution of biogenic opal and lithogenic components and the lowest 15n compared to the offshore stations but contrary to what would be expected from the productivity gradient particle flux did not decrease from estoc to lp below the upper several hundred meters particle flux was enhanced by additional particle input along the entire transect manifested by an increase of flux with depth and lower 15n values we offer a scenario in which intermediate nepheloid layers originating from the primary upwelling as well as particle dispersion from upwelling filaments mainly the cape ghir filament impact on the trap stations as far as 700 km into the open ocean this study contributes to our understanding of the poorly resolved biogeochemical transition between the productive shelf and subtropical gyre provinces

hydrochemical evidence of the depth of penetration of anthropogenic recharge in sandstone aquifers underlying two mature cities in the uk pollution of urban groundwater is routinely reported but the profile of contamination with depth in urban aquifers is rarely resolved this limits understanding of the depth of penetration of urban recharge and contaminants and use of urban groundwater penetration of anthropogenic solutes major ions trace metals in permo triassic sandstone aquifers underlying two mature conurbations in the uk was investigated through depth specific groundwater sampling of dedicated multilevel piezometers identification of solute origin and biogeochemical processes e g denitrification mineral dissolution was aided by use of stable isotope ratios 34 s 32 s 18 o 16 o 15 n 14 n 13 c 12 c and chemical speciation modelling phreeqc depth profiles of aquifer hydrochemistry reveal penetration of anthropogenic solutes to depths of between 30 and 47 m below ground in the unconfined sandstone and confirm the contributions of faecal and industrial effluents to urban recharge they also highlight the complexity of solute loading and difficulty resolving solute origin from the range of potential sources in urban groundwater faecally derived no3 is the most pervasive contaminant exceeding drinkingwater quality guidelines and is associated with elevated concentrations of b and so4 elevated concentrations of li b cr and co are observed at depth in groundwater contaminated by long term industrial land use metalworking observed penetration of anthropogenic solutes in the unconfined sandstone is consistent with post development recharge of urban groundwater residence times 230 a indicated by flow modelling and suggests tentatively that urban abstraction to depths of up to 50 m below ground in the unconfined permo triassic sandstone is required to scavenge contaminated groundwater

oxygen dynamics in the north atlantic subtropical gyre dissolved oxygen do in the ocean is a tracer for most ocean biogeochemical processes including net community production and remineralization of organic matter which in turn constrains the biological carbon pump knowledge of oxygen dynamics in the north atlantic ocean is mainly derived from observations at the bermuda atlantic time series study bats site located in the western subtropical gyre which may skew our view of the biogeochemistry of the subtropical north atlantic this study presents and compares a 15 yr record of do observations from estoc european station for time series in the ocean canary islands in the eastern subtropical north atlantic with the 20 yr record at bats our estimate for net community production of oxygen was 2 3 0 4 mol o2 m 2 yr 1 and of oxygen consumption was 2 3 0 5 mol o2 m 2 yr 1 at estoc and 4 mol o2 m 2 yr 1 and 4 4 1 mol m 2 yr 1 at bats respectively these values were determined by analyzing the time series using the discrete wavelet transform dwt method these flux values agree with similar estimates from in situ observational studies but are higher than those from modeling studies the difference in net oxygen production rates supports previous observations of a lower carbon export in the eastern compared to the western subtropical atlantic the inter annual analysis showed clear annual cycles at bats whereas longer cycles of nearly 4 years were apparent at estoc the dwt analysis showed trends in do anomalies dominated by long term perturbations at a basin scale for the consumption zones at both sites whereas yearly cycles dominated the production zone at bats the long term perturbations found are likely associated with ventilation of the main thermocline affecting the consumption and production zones at estoc

a dual isotope approach to the nitrogen hydrochemistry of an urban aquifer the potential for exploitation of urban aquifers is partly dependent on understanding the distribution and fate of urban n sources such as sewage and fertilisers that can limit the use of groundwater for public supplies to investigate the application of the dual isotope approach to understanding the n hydrochemistry of urban groundwater this paper presents 15n no3 and 18o no3 data collected from two multi level piezometers in the sherwood sandstone aquifer beneath nottingham in the english midlands uk at one multi level piezometer old basford depth sample measurements of 15n no3 in the range 9 2 to 11 4 and 18o no3 in the range 8 2 to 10 9 together with no3 nitrate concentrations from 31 7 to 66 7 mg l are evidence for nitrification of sewage derived inputs in contrast at the other multi level piezometer the meadows isotopically enriched samples 15n no3 in the range 24 3 to 42 2 and 18o no3 in the range 20 5 to 29 4 are evidence for denitrification although the compositional range of 15n no3 does not identify the n source without corroborating data for the meadows location a cross plot of 15n no3 versus 18o no3 gave an enrichment of the 15n isotope relative to the 18o isotope by a factor of 1 9 within the range of 1 3 2 1 reported for denitrification in other studies this study has shown that the dual isotope approach provides improved understanding of n sources and fate in the urban environment but further work is required to identify nitrification pathways to provide more confidence in the application and interpretation of 18o no3 measurements

rapid melting dynamics of an alpine glacier with repeated uav photogrammetry abstract glacial retreat is a major problem in the alps especially over the past 40 years unmanned aerial vehicles uavs can provide an unparalleled opportunity to track the spatiotemporal variations in rapidly changing glacial morphological features related to glacial dynamics the objective of this study is to evaluate the potential of commercial uav platforms to detect the evolution of the surface topography and morphology of an alpine glacier over a short time scale through the repeated acquisition of high resolution photogrammetric data two high resolution uav surveys were performed on the ablation region of the morteratsch glacier swiss alps in july and september 2016 first structure from motion sfm techniques were applied to create orthophotos and digital surface models dsms of the glacial surface from multi view uav acquisitions the geometric accuracy of dsms and orthophotos was checked using differential global navigation satellite system dgnss ground measurements and an accuracy of approximately 17 cm was achieved for both models high resolution orthophotos and dsms made it possible to provide a detailed characterization of rapidly changing glacial environments comparing the data from the first and the second campaigns the evolution of the lower part of the glacier in response to summer ablation was evaluated two distinct processes were revealed and accurately quantified an average lowering of the surface with a mean ice thinning of 4 m and an average horizontal displacement of 3 m due to flowing ice these data were validated through a comparison of different algorithms and approaches which clearly showed the consistency of the results the melt rate spatial patterns were then compared to the glacial brightness and roughness maps derived from the september uav acquisition the results showed that the dsm differences describing the glacial melt rates were inversely related to the glacial brightness in contrast a positive but weaker relationship existed between the dsm differences and glacial roughness this research demonstrates that uav photogrammetry allows the qualitative and quantitative appreciation of the complex evolution of retreating glaciers at a centimetre scale spatial resolution such performance allows the detection of seasonal changes in the surface topography which are related to summer ablation and span from the processes affecting the entire glacier to those that are more local

urban groundwater baseflow influence upon inorganic river water quality the river tame headwaters catchment in the city of birmingham uk summary understanding the linkage between urban land groundwater baseflow and river contamination at the city scale is lacking this study evaluates the influence of inorganic major minor ions and metals groundwater contamination in the triassic sandstone quaternary deposits aquifer system underlying the city of birmingham uk upon the baseflow and water quality of the river tame baseflow water quality data have been collected from a riverbed piezometer network installed in the 7 4 km reach crossing the effluent unconfined sandstone aquifer and compared to river and aquifer water quality data overall the inorganic chemical quality of the baseflow was not as poor as potentially surmised from the urbanisation present baseflow impact upon river water quality was also low these conclusions were underpinned by evidences of limited river water quality changes along the reach some river concentrations being diluted by better quality baseflow only occasional breaching of water quality criteria limited impact upon river reach quality local to elevated baseflow dicharges natural attenuation occurrence within the riverbed and modest albeit somewhat uncertain baseflow mass fluxes baseflow fluxes to the reach were in the ranges 100 3500 t yr for major ions 1 50 t yr for minor ions and 1 500 kg yr for toxic metals with zinc and nickel most prominent the sporadic occurrence of elevated baseflow concentrations was ascribed to discrete groundwater plume discharges more detailed sub reach studies would be required to fully resolve discrete plume baseflow contributions and improve mass flux estimates not uncommonly the urban river studied was already contaminated and hence persistent baseflow fluxes may assume more importance if the river became cleaner through other control measures future research should hence consider the emergent significance of urban baseflows there are needs to conduct similar studies to investigate if city scale baseflow impacts are comparable elsewhere research the importance of spatially and temporally dynamic attenuation in the riverbed and develop improved baseflow mass flux estimation methods

assessment of the surface mass balance along the k transect greenland ice sheet from satellite derived albedos this paper explores the potential of using satellite derived albedos to estimate the surface mass balance of the kangerlussuaq transect k transect greenland ice sheet we first retrieved surface albedos from advanced very high resolution radar data by using among other techniques a new cloud detection algorithm based on the relation between brightness temperature and surface elevation we then computed the satellite derived mass balance bsat from the mean albedo for the transect by taking fixed values for atmospheric transmissivity and the longwave and turbulent fluxes we found that bsat explains 71 of the variance in 13 years of stake mass balance measurements bm our method also provides good estimates of the magnitude of the interannual variability in bm the performance of the method degrades considerably without correction for anisotropic reflection at the surface and recalibration of the satellite sensors with dry snow at the top of the ice sheet sensitivity tests indicate that the method s performance is hardly sensitive to uncertainties in parameters therefore we expect that the method could be successfully applied on other glaciers and parts of ice sheets and ice caps especially where accumulation rates are relatively small we show that the investigated method performs best just below the mean equilibrium line altitude

model study of the spatial distribution of the energy and mass balance of morteratschgletscher switzerland to investigate the spatial distribution of the energy and mass balance fluxes of a glacier a two dimensional mass balance model was developed and applied to morteratschgletscher switzerland the model is driven by meteorological input from four synoptic weather stations located in the vicinity of morteratschgletscher the model results were compared to observations made on the glacier the calculated mean specific mass balance is 0 47 m w e for 1999 and 0 23 m w e for 2000 net shortwave radiation shows a minimum at around 3350 m a s l due to the effects of shading slope aspect reflection from the slopes and obstruction of the sky ignoring these effects results in a 37 increase in the annual incoming shortwave radiation on the glacier causing 0 34 m w e more ablation a 1 c change in the air temperature results in a shift of 0 67 m w e in the mean specific mass balance while altering the precipitation by 10 causes a change of 0 17 m w e

short term sedimentation pulses recorded with a fluorescence sensor and sediment traps at 9 m depth in the canary basin we observed short term peaks in pigment fluorescence and backscattering using optical sensors combined with time series sediment traps at 900 m depth at an oligotrophic site in the canary island region these events were observed in late winter to early spring and lasted only a few hours to a few days the events generally coincided with late winter to early spring flux maxima recorded by the traps surprisingly microscopic analyses showed no evidence of sedimentation of intact phytoplankton cells during the fluorescence peaks however we observed well preserved zooplankton fecal pellets containing densely packed coccoliths and presumably large amounts of chlorophyll derived pigments

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

the sensitivity of the southwest monsoon phytoplankton bloom to variations in aeolian iron deposition over the arabian sea 1 a coupled 3 d biophysical ocean general circulation model is used to investigate how aeolian iron deposition affects the arabian sea ecosystem two separate aeolian iron deposition fields derived from the giss and gocart atmospheric transport models have been applied as surface boundary conditions the model results exhibit widespread biogeochemical sensitivity to the choice of deposition field with gocart deposition sw monsoon phytoplankton blooms in the western and central arabian sea are enhanced and exhibit greater realism the central arabian sea bloom is supported by supplemental input of horizontally advected iron from a pool that undergoes a yearlong progression that begins in the gulf of oman where the difference in aeolian iron enrichment between the two deposition fields is most prevalent the gocart enhanced blooms result in a more pronounced shift toward netplankton an increase in euphotic zone export flux of up to a 20 during the sw monsoon and an additional annual biogenic export of 3 5 tgc the potential ramifications of regional n cycle alteration through stimulation of n2 fixation that is promoted by significant aeolian mineral flux needs to be explored the canonical thinking that the northern arabian sea is invariably iron replete is now being challenged by both our model results and recent observational studies as well our results indicate that arabian sea iron concentrations are strongly modulated by the specific nature of aeolian mineral deposition thus climate or land use influences on dust mobilization could exercise leading order controls on regional biogeochemical variability metabolic status and air sea exchanges of co2

a distributed surface energy balance model for a small valley glacier i development and testing for haut glacier d arolla valais switzerland this paper describes the development and testing of a distributed surface energy balance model used to calculate rates of surface melting at haut glacier d arolla valais switzerland the model uses a digital elevation model dem of the glacier surface and surrounding topography together with meteorological data collected at a site in front of the glacier to determine hourly or daily totals of the energy balance components and hence of melting over the entire surface of the glacier with a spatial resolutio of 20 m the model can also be used to determine temporal and spatial variations in snow depth snow line position and glacier surface albedo calculations from the model are compared with observations made along the glacier centre line in 1990 and in general the model performs very well the correlation coefficients between calculated and measured snow line elevation albedo and ablation are 0 99 0 85 and 0 81 respectively the main source of error between modelled and measured values of these variables is probably inadequacies in the parameterization of albedo used in the model

comparison of avhrr derived and in situ surface albedo over the greenland ice sheet abstract this paper discusses a methodology for computing the clear sky surface albedo over the greenland ice sheet by using advanced very high resolution radiometer avhrr global area coverage visible and near infrared reflectances this approach is then used to map the monthly changes in albedo over the entire greenland ice sheet during the spring and summer months the methodology includes corrections for the intervening atmosphere by using the 6s radiative transfer model additional corrections for the anisotropic nature o f snow reflectance and the conversion from a marrow into a broadband albedo are made based on in site measurements from the swiss federal institute of technology university of colorado camp at 69 34 n 49 18 w comparison with surface albedo field ineasureinents indicates that before the onset of snoic melt agreement is good between the satellite derived and measured surface albedo after melt begins it is difficult to compare the satellite values with the field data owing to melt water ponding on the ice sheet surface with appropriate modifications the 6s radiative transfer model is suitable for atmospherically correcting avhrr visible and near infrared radiances atmospherically polar regions

the role of wildfire and gully erosion in particulate pb export from contaminated peatland catchments in the southern pennines u k the near surface layer of peatlands of the peak district southern pennines uk is severely contaminated with atmospherically deposited pb contemporary catchment soil pb inventories at upper north grain and torside clough reveal that 23 and 54 respectively of the potential store of pb in each catchment has been lost through erosion of the contaminated near surface peat layer soil pb inventories and the pb content of suspended sediments reveal that in both catchments the main mechanism for contemporary particulate pb export is gully erosion historical sheet erosion on bare peat flats at torside clough has released significant quantities of pb into the fluvial system triggered by the exposure of the near surface peat during an accidental wildfire in 1970 up to 32 of the total pb export from the catchment may have been released during a discrete erosion event soon after the wildfire accidental wildfires and the subsequent release of highly contaminated peat into the southern pennine fluvial system may increase under predicted climate change scenarios

chemical remobilization of contaminant metals within floodplain sediments in an incising river system implications for dating and chemostratigraphy metals such as pb zn cd and cu from historical mining activity have been used as stratigraphic markers for dating and provenancing vertically accreted fine grained floodplain overbank deposits this study presents evidence for chemical remobilization of these metals within overbank sediments in the tyne basin uk the evidence includes breakdown of metal bearing minerals sulphides carbonates iron and manganese oxyhydroxides shifts of chemical fractions within zones of relatively low ph towards more soluble and reactive phases and accumulation of secondary iron and manganese oxyhydroxides at levels related to fluctuating water table levels or to the breakdown of organic matter all of this suggests that fine centimetre scale chemostratigraphy using metal concentrations and ratios is unlikely to provide reliable data in river systems that have experienced or are experiencing major changes in water table levels or pedogenesis coarse tens of centimetre to metre scale chemostratigraphy when applied with caution may still provide a means of delineating contaminated units

retrieval of snow reflectance from landsat data in rugged terrain we developed a model to calculate the spectral reflectance of snow by normalizing the topographic effect and correcting the atmospheric effect simultaneously this model considers the shadowing effect of the surrounding terrain on both direct and diffuse irradiance by using the obstruction coefficient in sun ray direction and introducing the isotropic view factor in addition a new method to calculate the surrounding reflected irradiance by introducing the shape factor which can account for the radiation reflected from the surrounding pixels was developed the model was tested in the upper stream of the heihe river basin qilian mountains china using a subscene of a landsat enhanced thematic mapper plus etm image acquired on 20 april 2000 the result showed that the model could eliminate most of the shadowing effect of rugged terrain and could estimate snow reflectance correctly the problem of data saturation when retrieving snow reflectance is also discussed

spatial and temporal variations of the surface albedo and other factors influencing urumqi glacier no 1 in tien shan china glacier albedo controls the surface energy budget the variability of which affects the glacier surface melt rate and in turn impacts the mass balance of the glacier during 2013 and 2014 spatial and temporal variations of albedo were investigated using 18 landsat images of urumqi glacier no 1 factors influencing these spatiotemporal profiles were analyzed an established retrieval process including geolocation radiometric calibration atmospheric topographic and anisotropic correction and narrow to broadband conversion was applied for the first time to landsat 8 images differences between landsat image derived albedo values and albedo values measured using a handheld spectroradiometer ranged from 0 024 to 0 049 spatial and temporal variations of surface albedo were significant especially in the ablation area the variability of the values of ice albedo ranged from 0 06 to 0 44 due to topographic effects and light absorbing impurities the results suggest that this retrieval method can be used to investigate the spatial and temporal variability of surface albedo from landsat 8 images on mountain glaciers moreover as constant albedo values for ice and snow cannot be assumed the distribution of albedo was not completely dependent on altitude under conditions of more intense ablation and by reason of light absorbing impurities during the melt season

sediment budget for an eroding peat moorland catchment in northern england this paper describes a detailed contemporary sediment budget from a small peat covered upland catchment in upper teesdale northern england the sediment budget was constructed by measuring 1 sediment transfers on slopes 2 sediment flux on the floodplain and through the main stream channel and 3 sediment yield at the catchment outlet measurements were taken over a four year monitoring period between july 1997 and october 2001 when interannual variations in runoff were relatively small three sites were selected to represent the major erosion subsystems within the catchment an area of bare peat flats a pair of peat gullies and a 300 m channel reach collectively the sites allow detailed characterization of the main patterns of sediment flux within the catchment and can be scaled up to provide an estimate of the sediment budget for the catchment as a whole this constitutes the first attempt to provide a complete description of the functioning of the sediment system in eroding blanket peatlands results demonstrate that fluvial suspended sediment flux is controlled to a large degree by channel processes gully erosion rates are high but coupling between the slopes and channels is poor and therefore the role of hillslope sediment supply to catchment output is reduced consequently contemporary sediment export from the catchment is controlled primarily by in channel processes error analysis of the sediment budgets is used to discuss the limitations of this approach for assessing upland sediment dynamics a 60 per cent reduction in fluvial suspended sediment yield from rough sike over the last 40 years correlates with photographic evidence of significant re vegetation of gullies over a similar period this strongly suggests that the reduced sediment yields are a function of increased sediment storage at the slope channel interface associated with re vegetation copyright 2005 john wiley sons ltd

rapid calculation of terrain parameters for radiation modeling from digital elevation data digital elevation models are widely used to calculate terrain parameters to determine incoming solar and longwave radiation for use in surface climate models interpretation of remote sensing data and parameters in hydrologic models because of the large number of points in an elevation grid fast algorithms are useful to save computation time a description is given of rapid methods for calculating slope and azimuth solar illumination angle horizons and view factors for radiation from sky and terrain calculation time is reduced by fast algorithms and lookup tables

the surface albedo of the greenland ice sheet satellite derived and in situ measurements in the sondre stromfjord area during the 1991 melt season the temporal and spatial variation in the surface albedo of the greenland ice sheet during the ablation season of 1991 is investigated the study focuses on an area east of sondre stromfjord measuring 200 km by 200 km and centred at 67 5 n 48 13 w the analysis is based on satellite radiance measurements carried out by the advanced very high resolution radiometer avhrr the broad band albedo is estimated from the albedos in channel 1 visible and channel 2 near infrared the results are calibrated with the surface albedo of sea and dry snow satellite derived albedos are compared with gimex ground measurements at three stations there is a high degree of consistency in temporal variation at two of the three stations large systematic differences are attributed to albedo variations on subpixel scale in the course of the ablation season four zones appear each parallel to the ice edge it is proposed that these are in order of increasing altitude i clean and dry ice ii ice with surface water iii superimposed ice and iv snow an extensive description of these zones is given on the basis of the situation on 25 july 1991 zones i iii and iv reveal fairly constant albedos 0 46 0 65 and 0 75 on average whereas zone ii is characterised by an albedo minimum 0 34 survey of the western margin of the greenland ice sheet up to 71 n shows that the zonation occurs between 66 and 70 n

seasonal impact of mineral dust on deep ocean particle flux in the eastern subtropical atlantic ocean abstract seasonal lithogenic particle and al fluxes were obtained from a deep ocean sediment trap deployment during 1992 and 1993 off nw africa and were compared concurrently with atmospheric al concentrations and two dimensional backward trajectories of windfields from two barometric levels in the lower and mid troposphere marine al fluxes lithogenic particle fluxes and grain size distributions in the area were found to be directly linked to airmass pathways and surface mineral aerosol concentrations at 1000 m water depth highest al fluxes 10 77 mg m 2 day 1 lithogenic particle fluxes 99 25 mg m 2 day 1 and smallest mean grain sizes 11 9 m occurred during the winter and spring season concurrent with highest atmospheric dust load and al concentrations 15 300 ng m 3 in the lower troposphere a strong seasonal change of the main atmospheric dust transport from low altitude winds during winter spring to higher altitudes during summer is clearly reflected at depth by a significant coarsening of mean grain sizes 18 6 m and lowest al 0 81 mg m 2 day 1 and lithogenic particle fluxes 11 3 mg m 2 day 1 found in the sediment traps the comparison of marine atmospheric and model derived data used within this study highlights the close temporal coupling between atmospheric dust transport and the deep ocean particle stock

climate sensitivity of glaciers in southern norway application of an energy balance model to nigardsbreen hellstugubreen and alfotbreen three glaciers in southern norway with very different massbalance characteristics are studied with an energy balance model of the ice snow surface the model simulates the observed mass balance profiles in a satisfactory way and can thus be used with some confidence in a study of climate sensitivity calculated changes in equilibrium line altitude for a 1 k temperature increase are 110 108 and 135 in for nigardsbreen hellstugubreen and alfotbreen respectively the corresponding changes in mass balance averaged over the entire glacier area are 0 88 0 715 and 1 11 in year water equivalent runs with an ice flow model for nigardsbreen to which calculated mass balance profiles are imposed predict that the front will advance by 3 km for a 1 k cooling and will retreat by as much as 6 5 km for a 1 k warming the response to a 10 increase in precipitation would be a 2 km advance of the snout whereas a 4 km retreat is predicted for a 10 decrease this large sensitivity as compared to many other glaciers is to a large extent due to the geometry of nigardsbreen

validation of avhrr and modis derived albedos of snow and ice surfaces by means of helicopter measurements we describe the validation of surface albedos of snow and glacier ice as derived from advanced very high resolution radiometer avhrr and moderate resolution imaging spectrometer modis satellite data for this purpose we measured surface albedos from a helicopter over vatnajokull iceland and the kangerlussuaq transect western part of the greenland ice sheet in thematic mapper tm bands 2 and 4 and avhrr bands 1 and 2 and converted these values to measured albedos in three modis bands relative to other validation methods our helicopter measurements have the advantages of larger spatial coverage and of almost direct measurements in satellite sensor spectral bands we found the smallest differences between the satellite derived and helicopter albedos for the kangerlussuaq transect for avhrr data a mean difference of 0 01 in both bands with the satellite in near nadir position and for two modis images a mean difference of 0 00 0 02 for bands 2 and 4 and 0 03 for band 1 for two avhrr images of vatnajokull we found mean differences of up to 0 06 differences are primarily due to errors in the satellite derived albedos which in turn are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice satellite data obtained from view zenith angles larger than 50 55 appeared to be unsuitable

heavy metal release by peat erosion in the peak district southern pennines uk upper north grain ung is a heavily eroding blanket peat catchment in the peak district southern pennines uk concentrations of lead in the near surface peat layer at ung are in excess of 1000 mg kg 1 for peatland environments these lead concentrations are some of the highest globally high concentrations of industrially derived atmospherically transported magnetic spherules are also stored in the near surface peat layer samples of suspended sediment taken during a storm event that occurred on 1 november 2002 at ung and of the potential catchment sources for suspended sediments were analysed for lead content and the environmental magnetic properties of anhysteretic remanent magnetization arm and saturation isothermal remanent magnetization sirm at the beginning of the storm event there is a peak in both suspended sediment and associated lead concentration sirm arm values for suspended sediment samples throughout the storm reveal that the initial lead flush is associated with a specific sediment source namely that of organic sediment eroded from the upper peat layer using the magnetic fingerprinting approach to discrimination of sediment sources this study reveals that erosion of the upper peat layer at ung is releasing high concentrations of industrially derived lead and by inference other toxic heavy metals associated with industrial particulates into the fluvial systems of the southern pennines climate change scenarios for the uk involving higher summer temperatures and stormier winters may result in an increased flux both of sediment associated and dissolved heavy metals from eroding peatland catchments in the southern pennines adversely affecting the quality of sediment and water entering reservoirs of the region copyright 2005 john wiley sons ltd

significance of vertical flow through low conductivity zones in bromsgrove sandstone aquifer abstract when water passes vertically through low conductivity zones in aquifers significant vertical head gradients occur the importance of such gradients is identified in a study of the bromsgrove sandstone aquifer unit a mathematical model incorporating the low conductivity layers has been developed to explain the changed conditions from 1900 when there were extensive spring flows to the present day when deep boreholes intercept much of the groundwater flow the mathematical model also helps in understanding the changing pumped drawdowns and water table elevations

tracing sources of carbon in urban groundwater using δ13ctdic ratios total dissolved inorganic carbon tdic and its stable isotope ratio 13ctdic are used to trace the evolution of the carbon system of groundwater in three uk permo triassic sandstone aquifers samples were collected from multilevel piezometers open boreholes and sewer sampling points in the british midlands nottingham birmingham and doncaster to evaluate both local and regional variations in 13ctdic 13c samples of matrix and pore water have also been analysed in each aquifer to further constrain the interpretations combining 13ctdic ratios with measurements of tdic and ph clearly distinguishes the principal processes underlying the geochemical evolution of groundwater in triassic sandstone aquifers where processes can be both natural e g carbonate dissolution and anthropogenic sewer derived recharge the paper shows that 13ctdic resolves ambiguities that arise from the interpretation of tdic and ph measurements in isolation field measurements demonstrate that under natural conditions the carbonate system evolves similarly in each aquifer an open system evolution during recharge largely saturates the groundwater with carbonate depending upon its availability in the sandstone matrix the contribution of sewer exfiltration to urban recharge is readily distinguished by lower ph and higher tdic values without significant changes in 13ctdic

temporal and spatial variation of the surface albedo of the morteratschgletscher switzerland as derived from 12 landsat images this investigation uses landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography morteratschgletscher switzerland our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo the correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0 10 depending on wavelength band solar zenith angle and surface type we analyzed the uncertainties in the retrieval method and mainly expect errors in satellite derived albedos for areas with large variation in topography and high albedos the latter is due to application of bidirectional reflectance distribution function brdf parameterizations for the anisotropic correction to albedos outside the parameterizations validity on average satellite derived albedos exceed the measured surface albedo by 0 03 the glacier tongue is characterized by bands of low and high albedo relating to ice with higher and lower concentrations of debris the ice albedo shows no dependence on altitude except at 2000 2200 m a s l it increases during summer which is likely associated with rainfall as concluded from a comparison between summer rainfall and measured albedos

blanket peat erosion in a mid wales catchment during two drought years the rate of blanket peat erosion was measured at an upland site in central wales during the 1983 1984 drought years erosion pins a peat surface sediment trap and sediment sampling in the effluent stream were used to estimate the rate of peat surface recession and the rate of organic sediment loss from the catchment an overall rate of surface recession of 16 mm y 1 on exposed peat faces was recorded this differed between faces of different aspects with the greatest recession on southwest faces eroding peat surfaces exhibited maximum recession during the summer but the peat surface sediment trap indicated that the highest rates of sediment loss from peat faces due to rain wash occurred during the autumn and early winter stream sediment sampling showed that the yield of organic sediment from the catchment was 34 4 t km 2 yr 1 with greatest losses also during the autumn and early winter the evidence suggested that the surface recession as measured on erosion pins included a wastage or shrinkage component which possibly accounted for as much as 80 per cent of the apparent loss direct and circumstantial evidence suggested that peat wastage during the summer months was the most important agent of surface recession in the study period which encompassed the two dry summers desiccation provided available sediment during the autumn but organic sediment supply became limited as the winter progressed despite the occurrence of frost heave

a 1 year record of global radiation and albedo in the ablation zone of morteratschgletscher switzerland we analyse data on solar radiation measured with an automatic weather station on morteratschgletscher switzerland for the period 1 october 1995 30 september 1996 the station is in the lower ablation zone due to shading by surrounding mountains and atmospheric attenuation only 49 of the annual extraterrestrial irradiance mean 292 w m 2 reaches the glacier surface about 48 of this is absorbed at the surface mean 79 w m 2 annual albedo of 0 53 we present a simple albedo scheme for use in glacier mass balance models we fit the model to the 1 year dataset by optimizing five control parameters optimal values in brackets albedo of snow 0 75 albedo of firn 0 53 albedo of ice 0 34 e folding constant for effect of ageing on snow albedo 21 9 days and e folding constant for effect of snow depth on albedo 3 2 cm the input consists of daily albedo snow depth and dates of snowfall events the correlation coefficient between observed and simulated albedo is 0 931 the corresponding rms difference being 0 067

spatial and temporal transferability of a distributed energy balance glacier melt model abstract modeling melt from glaciers is crucial to assessing regional hydrology and eustatic sea level rise the transferability of such models in space and time has been widely assumed but rarely tested to investigate melt model transferability a distributed energy balance melt model debm is applied to two small glaciers of opposing aspects that are 10 km apart in the donjek range of the st elias mountains yukon territory canada an analysis is conducted in four stages to assess the transferability of the debm in space and time 1 locally derived model parameter values and meteorological forcing variables are used to assess model skill 2 model parameter values are transferred between glacier sites and between years of study 3 measured meteorological forcing variables are transferred between glaciers using locally derived parameter values 4 both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other treating the second glacier

sediment yield and delivery in the blanket peat moorlands of the southern pennines in contrast to much previous research on blanket peat moorland which has concentrated upon studies of the form and causes of gully erosion this paper attempts to investigate sediment transport and to estimate both short term and long term sediment yields in such terrain the research was conducted on wessenden head moor to the west of huddersfield yorkshire where automatic stream sampling continued over a period of two years use of corrected rating curves ferguson 1988 provided a mean estimate of sediment yield over this period of 55 t km 2 yr 1 in addition an estimate of longer term sediment yield was derived from four reservoir sediment surveys in the wessenden valley total yield was 203 69 t km 2 yr 1 including an organic fraction of 38 82 t km 2 yr 1 stream sampling at three sites on shiny brook including headwaters and the outflow to the reservoir suggested that there is great temporal and spatial variability in mineral and organic inputs to the reservoirs although not excessive in gravimetric terms the low density of peat means that there is a serious erosion problem estimates of erosion rates for the peat gully network at shiny brook appear to confirm earlier evidence concerning the relatively recent occurrence of this erosion within the last two centuries

temporal and spatial variations in spectral reflectance and characteristics of surface dust on gulkana glacier alaska range spectral reflectances in the visible to near infrared wavelength range 350 1050 nm were measured on the surface of gulkana glacier alaska range alaska usa at six different elevations from may to september 2001 the measurements showed variable spectral reflectances on the glacier surface and the spectra changed over time and elevation the spectra in may were those of a typical wet snow surface the reflectance ranged approximately from 0 4 to 0 8 and generally decreased as the wavelength increased as snowmelt proceeded the reflectance gradually fell and specific absorptions appeared in the spectrum at wavelength ranges of 400 600 and 670 680 nm corresponding to a red snow surface due to snow algal bloom as the ice surface was exposed the spectrum finally shifted to a lower 0 1 0 4 and flat reflectance curve typical of an ice surface contaminated with dust analyses of the dust on the glacier surface showed that its quantity and characteristics changed spatially and seasonally and were correlated with spectral albedo the results showed that the temporal and spatial variations in spectral reflectance on this glacier are due not only to physical properties of the glacier surface but also to biogenic materials on the surface e g red colored snow algal cells and cryoconite

elevational changes in meteorological variables along a midlatitude glacier during summer during the summer of 1994 a glaciometeorological experiment was carried out on the pasterze a glacier in austria this paper reports on the data from six energy balance stations ranging in altitude from 2075 to 3225 m above sea level asl the wind regime was dominated by the glacier wind on the tongue directional constancies ranged between 0 94 and 0 97 mean 2 m wind speed and specifie humidity were almost constant along the glacier the variation in the 2 m temperature along the glacier cannot be described by the usually assumed constant decrease with elevation on the tongue the 2 m temperature even increased with elevation a much better description of the temperature distribution is given by a linear relation between the potential temperature and the distance along the flow line this can be understood from a simple thermodynamic analysis of the glacier wind layer it is further shown that changes in clear sky global radiation with elevation are due mainly to changes in local albedo and relief and hardly at all to changes in absolute optical path length and atmospheric water vapor and aerosol content on the tongue the laterally averaged ice albedo is almost constant with elevation the flux of incoming long wave radiation during clear sky conditions at u2 2310 m asl was 48 w m2 higher than the flux at u5 3225 m asl on average more than half of the difference was due to systematic differences in the shape of the temperature profile probably the inversion depth is larger at u2 the rest can be ascribed to higher 2 m temperatures and larger amounts of upper hemisphere slopes at u2 the distributions of the meteorological variables and the parameterizations described in this paper might be incorporated in surface energy balance models designed to simulate the surface mass balance

composition age and provenance of organic matter in nw african dust over the atlantic ocean 1 eolian dust deposited on a meteorology buoy over the boreal winter and spring of 1992 1993 in the northeast atlantic off northwest africa 18 n 22 w afforded sufficient material for detailed assessment of its biogeochemical characteristics and provenance the sample was subjected to microscopic examination and bulk elemental isotopic black carbon and molecular lignin lipid analyses the bulk elemental composition and organic carbon oc content 1 02 dry weight establishes the dust s origin as continental upper crust and is typical of dusts that emanate from west africa these data are in accord with the extensive satellite imagery documenting the transit of dust clouds from the sahara and sahel regions e g nasa toms aerosol index microscopic examination reveals that charcoal like particles from vegetation fires black carbon bc are the most abundant morphologically distinct organic components accelerator mass spectrometry ams 14c analysis yields conventional 14c ages for bulk oc of 1260 40 years and bc of 2070 35 years taken together with corresponding stable carbon isotopic compositions 13c 18 9 and 15 1 respectively these results suggest the presence of biomass and burning residues derived from predominantly c4 vegetation that accumulated in soils over the late holocene molecular level measurements are also consistent with this scenario for example lignin derived phenols in the dustfall sample indicate a significant contribution of angiosperm grass type tissue the altered nature of the lignin suggests storage as residues in soils solvent extractable lipid constituents include a marked leaf wax type component with a molecular and stable carbon isotopic composition similar to those observed in surface marine sediments in this region the hydrocarbon fraction contained some diesel type contamination but the n alkanes c23 c33 retained a prominent odd even distribution with 13c ranging from 26 7 to 28 5 the suite of even carbon numbered n alkanols c22 c32 is 14c dated at 647 150 years with 13c values ranging from 23 9 to 30 4 the long chain n alkanoic acids c22 c32 exhibited 13c values ranging from 22 6 to 27 4 these waxes are evidently a mixed signal derived from contemporary c3 and c4 vegetation and from ablated soils and desiccated lake sediments of middle to late holocene age this molecular approach shows promise as a tool for continental paleoenvironmental assessment particularly with respect to past vegetation cover regional aridity and wind systems

hydrochemical evolution of the east midlands triassic sandstone aquifer england a detailed hydrogeochemical interpretation has been made of the red bed sherwood sandstone triassic aquifer of the east midlands of england on which a radiocarbon model has been used to establish a chronology of groundwaters along the flow line groundwater evolution is dominated by carbonate and sulphate mineral solution and precipitation and by redox reactions cation exchange reactions are negligible and the hydrogeochemistry has evolved in the absence of residual saline water three distinct zones are recognised 1 i recent groundwater mainly 100 y oxidising dominated by congruent dissolution of dolomite and by inputs from atmospheric and anthropogenic sources 2 ii groundwater age 103 104 y predominantly reducing dominated by incongruent dissolution of dolomite 3 iii groundwater age 104 y reducing conditions approach to isotopic and chemical equilibrium in the carbonate system dominance of gypsum dissolution the minor and trace element variation can be interpreted in relation to the principal geochemical reactions and recharge history na cl f and b are controlled by atmospheric inputs sr2 and mn2 trends can be explained by carbonate and sulphate mineral dissolution ba2 is derived from carbonates but controlled by barite equilibrium fe so42 no3 and u are strongly influenced by redox reactions the concentrations of transition metals and other elements remain very low only li and k are considered to represent additions by reaction of silicate minerals the extent of direct anthropogenic influence is probably limited to enhanced so4 no32 and possibly cu zn and pb in zone i

quantification of groundwater recharge in the city of nottingham uk groundwater is an important and valuable resource for water supply to cities in order to make full and wise use of the asset value a clear understanding of the quantities and sources of urban groundwater recharge is needed the water supply and disposal network is often an important source of recharge to urban groundwater through leakage from water mains and sewers an approach to establishing the spatial and temporal amounts of the three urban recharge sources precipitation mains and sewers is developed and illustrated using the nottingham uk urban aquifer a calibrated groundwater flow model is supplemented by calibrated solute balances for three conservative species cl so4 and total n thus providing four lines of evidence to use in the recharge estimation nottingham is located on a triassic sandstone aquifer with average precipitation of 700 mm year using the models current urban recharge is estimated to be 211 mm year of which 138 mm year 40 is from mains leakage and 10 mm year 100 is from sewer leakage the wide confidence intervals result from the scarcity of historical field data and the long turnover time in this high volume aquifer and should be significantly lower for many other aquifer systems

the control of sedimentary facies by climate during phases of crustal extension examples from the triassic of onshore and offshore england and northern ireland crustal extension controls the tectonic accommodation space available for sediments in rift settings and may be defined by the structural and depositional geometry of sedimentary successions observed on seismic data and the rate of subsidence through time as represented by the accommodation of sediment the characteristic features of each are dependant on three variables the time taken for deposition the interplay between tectonics and eustasy and the lithology thus facies of the succession observed the sherwood sandstone group has been considered to represent a syn rift phase of fluvial deposition throughout europe with the overlying mercia mudstone group interpreted as the succeeding phase of deposition in an evaporitic seaway during post rift thermal subsidence more recently however there has been the recognition that it is the mercia mst gp which is seen to thicken markedly into faults imaged on seismic data rather than the sherwood sandstone group this work demonstrates the mercia mst gp to be a syn rift phase of deposition with the fine grained nature of the sedimentary record at this time controlled by the prevailing arid climate such conditions were not conducive to the large scale and rapid movement of sediments from the hinterlands raised by relative footwall uplift thus the sediments are fine grained the minor thickening of the sherwood sst gp into faults is interpreted to be a combination of minor extension in the early triassic superimposed on thermal subsidence inherited from the important regional phase of extension in the early permian analysis of the timing of fault growth indicates a larger proportion of fault controlled synsedimentary movement occurred during the mid to late triassic mercia mst gp rather than the early triassic sherwood sst gp

radiosity approach for the shortwave surface radiation balance in complex terrain the influence of topography on the radiation balance in complex terrain has so far been investigated either with very simple or very sophisticated approaches that are limited respectively by an uncontrolled spatial representation of radiative fluxes or heavy computational efforts to bridge this gap in complexity this paper proposes the radiosity approach well known in computer graphics to study anisotropic reflections of radiation in complex terrain to this end the radiosity equation is rederived in the context of three dimensional radiative transfer the discretized equation is solved by means of an adapted version of progressive refinement iteration to systematically study terrain effects the geometrical disorder provided by the topography is considered in its simplest approximation by gaussian random fields these model topographies capture the most important length scales of complex terrain namely a typical elevation and a typical valley width via the variance and the correlation length of the field respectively the mean reflected radiation is computed as a function of these length scales and sun elevation thereby explicitly addressing finite system sizes and grid resolutions a comparison with an isotropic parameterization of terrain reflections reveals that mean values are similar whereas spatial distributions vary remarkably it is also shown that the mean reflected radiation in real topography is reasonably well characterized by the gaussian approximation as a final application of the method the effective albedo of a topography is shown to vary with sun elevation and domain averaged albedo leading to albedo differences up to 0 025