minor and trace element export from a glacierized alpine headwater catchment haut glacier d arolla switzerland major ion concentrations in meltwaters draining glacial environments have been widely reported however concentrations of minor and trace elements have received scant attention this study presents trace and minor element variations in bulk meltwaters draining haut glacier d arolla switzerland based on twice daily sampling throughout the 1999 ablation season which represents the most detailed meltwater quality dataset to date in order to assess the mode of export from the catchment these elements are partitioned into i dissolved and ii particulate associated minor and trace element components a computer based speciation model phreeqci was applied to the bulk meltwater data suggesting that ba be cd cu li rb and sr exist primarily as mobile monovalent or divalent dissolved cations which may be involved in interactions with suspended sediment surfaces conversely the model predicts the precipitation of fe al mn and cr oxi hydroxides suggesting these species may be predominantly transported as colloids which may remove other minor and trace elements from solution by co precipitation reactions laboratory leaching experiments on suspended sediments and fresh rock powder suggests that minor and trace element concentrations may also be influenced by oxy hydroxide precipitation and adsorption desorption reactions with suspended sediment surfaces the quantity and transport mode of trace and minor elements may influence their bioavailability downstream of glacierized headwater catchments further the enrichment of many dissolved minor and trace elements in meltwaters compared with world stream waters coupled with the timing of water and sediment delivery during the summer months may have implications for downstream aquatic environments copyright 2001 john wiley sons ltd

large values of hydraulic roughness in subglacial conduits during conduit enlargement implications for modeling conduit evolution hydraulic roughness accounts for energy dissipated as heat and should exert an important control on rates of subglacial conduit enlargement by melting few studies however have quantified how subglacial conduit roughness evolves over time or how that evolution affects models of conduit enlargement to address this knowledge gap we calculated values for two roughness parameters the darcy weisbach friction factor f and the manning roughness coefficient n using dye tracing data from a mapped subglacial conduit at rieperbreen svalbard values of f and n calculated from dye traces were compared with values of f and n calculated from commonly used relationships between surface roughness heights and conduit hydraulic diameters roughness values calculated from dye tracing ranged from 75 0 97 for f and from 0 68 0 09 s m 1 3 for n equations that calculate roughness parameters from surface roughness heights underpredicted values of f by as much as a factor of 326 and values of n by a factor of 17 relative to values obtained from the dye tracing study we argue these large underpredictions occur because relative roughness in subglacial conduits during the early stages of conduit enlargement exceeds the 5 range of relative roughness that can be used to directly relate values of f and n to flow depth and surface roughness heights simple conduit hydrological models presented here show how parameterization of roughness impacts models of conduit discharge and enlargement rate we used relationships between conduit relative roughness and values of f and n calculated from our dye tracing study to parameterize a model of conduit enlargement assuming a fixed hydraulic gradient of 0 01 and ignoring creep closure it took conduits 9 25 days to enlarge from a diameter of 0 44 m to 3 m which was 6 7 fold longer than using common roughness parameterizations copyright 2013 john wiley sons ltd

modeling the diurnal variation of tracer transit velocity through a subglacial channel 1 tracer injections into a moulin connecting to a subglacial channel at unteraargletscher were repeated at intervals of about two hours over two diurnal discharge cycles in august and september 2000 the pronounced hysteresis in the relationships between tracer transit velocity and proglacial discharge may be explained by adjustments of the channel cross section in response to discharge variations or alternatively by modulation of inflow from the tributary moulin into a main subglacial channel to test these hypotheses we employ a physically based time dependent model of channelized subglacial drainage in a series of numerical experiments we explore the general characteristics of each mechanism before the model is applied to diurnal discharge variations measured during the tracer tests at unteraargletscher we found that the ability of a rothlisberger channel to adjust its size to the prevailing hydraulic conditions can contribute to the hysteresis in the velocity discharge relationships however using plausible parameter values r channel hydraulics alone is not satisfactory in reproducing the magnitude of observed transit velocities the model further confirms that retardation of the tracer in the tributary moulin due to inflow modulation has major effects on transit velocities both in magnitude and timing with appropriate assumptions on channel sinuosity and moulin size a combination of both mechanisms can be found that is capable of reproducing the observed transit velocities

geometry bed topography and drainage system structure of the haut glacier d arolla switzerland as part of an integrated study of the hydrology meltwater quality and dynamics of the haut glacier d arolla switzerland the glacier s drainage network structure was determined from patterns of dye recovery in 342 injection experiments conducted from 47 moulins distributed widely across the glacier this structure was compared with theoretical predictions based upon reconstructed patterns of water flow governed by a the subglacial hydraulic potential surface and b the subglacial bedrock surface these reconstructions were based on measurements of ice surface and bedrock topography obtained by a combination of ground survey and radio echo sounding techniques the two reconstructions simulate the drainage system structures expected for a closed channels in which water is pressurized by the overlying ice and b gravity driven open channel flow the closed channel model provides the best fit to the observed structure even though theoretical calculations suggest that under summer discharge conditions open channel flow may be widespread beneath the glacier possible reasons for this apparent discrepancy are discussed

an integrated approach to modelling hydrology and water quality in glacierized catchments the results are summarized of an integrated investigation of glacier geometry ablation patterns water balance meltwater routing hydrochemistry and suspended sediment yield the ultimate objective is to evaluate the assumptions of lumped two component mixing models as descriptors of glacier hydrology and to develop a semi distributed physically based model as an alternative the results of the study demonstrate that a reconstruction of probable subglacial drainage alignments can be achieved through a combination of terrain modelling based on estimated potential surface and dye tracing experiments recession curve analysis evidence of the seasonal instability of the englacial and subglacial electrical conductivities assumed in a mixing model evidence of the non conservative behaviour of water chemistry in the presence of suspended sediment and evidence of the seasonal evolution of the subglacial drainage system based on dye tracing all indicate that an alternative to a lumped static model of the hydrology is necessary the alternative presented in this paper is based on the combination of an energy balance model for surface melt which operates on an hourly time step and accounts for the changing spatial distribution of melt through the day as shading patterns change and routing procedures that transfer surface melt to moulins on the basis of glacier surface gradients then route water through reconstructed conduit systems using a hydraulic sewer flow routing procedure

diurnal variability of subglacial drainage conditions as revealed by tracer experiments 1 the morphology of the drainage system of unteraargletscher switzerland and the diurnal variability of drainage conditions were investigated by conducting a series of tracer tests over a number of discharge cycles during the ablation season 2000 dye injections into a moulin were repeated at intervals of a few hours and were accompanied by simultaneous measurements of discharge of supraglacial meltwater draining into the moulin and bulk runoff in the proglacial stream fast transit velocities in conjunction with low dispersion values suggest that the tracer was routed through a hydraulically efficient channelized drainage system however detailed analyses reveal a large diurnal variability in terms of transit velocity and dispersion coefficient this finding underlines the difficulty of detecting a possible drainage system evolution based on single tracer tests conducted at coarse temporal intervals furthermore the obtained velocity discharge relationships display pronounced hysteresis we suggest that the evolution of the cross sectional area of an ice walled conduit and the modulation of inflow at the junction of a tributary moulin to a main subglacial channel are responsible for the observed behavior

the effect of the subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model in order to interpret observed short term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model in particular the transient stages of growing or shrinking water filled cavities at the ice bedrock interface were analysed it was found that the sliding velocity was larger when cavities were growing than when they had reached the steady state size for a given water pressure the smallest sliding velocities occurred while cavities were shrinking when cavitation is substantial a small drop of water pressure below the steady state value e g by 0 5 bar can temporarily cause backward sliding a limiting water pressure at which sliding becomes unstable is derived the consequences of more realistic assumptions than those of the model are discussed

numerical simulations of glacial valley longitudinal profile evolution glaciers shape alpine landscapes they broaden valley bottoms enhance local valley relief generate multiple steps overdeepen valley floors and cause tributary valleys to hang these distinctive glacial signatures result from 10 4 10 5 yr of erosion during which swings in climate drive advances and retreats of alpine glaciers we use a numerical model of glacial erosion to explore the development of the longitudinal profiles of glaciated valleys the model is driven by the past 400 k y of variable climate because both sliding speed which dictates abrasion rate and water pressure fluctuations which strongly modulate quarrying rate should peak at the equilibrium line altitude ela we expect the locus of most rapid erosion to follow the transient ela simulations of a single glacial valley show rapid flattening of the longitudinal profile inclusion of a tributary glacier creates a step immediately downvalley of the tributary junction that persists over multiple glaciations and commonly leaves the tributary valley hanging steps and overdeepenings result from an increase in ice discharge immediately below the tributary junction which is accommodated primarily by increased ice thickness and hence sliding rate the size of the step increases with the ratio of tributary to trunk ice discharge while the height of a hanging valley reflects the difference in the time integrated ice discharge in tributary and trunk valleys and therefore increases as the discharge ratio decreases

mixing law versus discharge and electrical conductivity relationships application to an alpine proglacial stream mixing laws have been used in hydrogeology for decades in glacial hydrology they are used to determine the contributions of the different reservoirs supplying the proglacial stream however some assumptions about discharge solute matter and discharge electrical conductivity ec relationships have led to erroneous conclusions analysis of a theoretical example indicated a hyperbolic relationship between discharge and solute matter concentration ec for two reservoirs we applied this approach to experimental data from the baounet glacier savoie france assuming that the proglacial stream is provided by a combination of watershed groundwater flow diurnally stable and with high ec and quick drainage from the glacier low ec and discharge that change very quickly applying mixing laws allowed us to characterise these two flows and to separate the quick flows glacial ablation and rainfalls copyright 2011 john wiley sons ltd

electrical resistivity imaging and dye tracer test for the estimation of water leakage paths from reservoir of akdegirmen dam in afyonkarahisar turkey the seepage occurrence from the reservoir on the right bank of the akdegirmen dam located in afyonkarahisar province in the turkey has been investigated when the reservoir began to fill with water a large amount of water seepage occurred at the dam the seepage developed at the base of the spillway and the right downstream slope of the dam the various attempts have been made to reduce the seepage using grouting although the additional grouting operations was reduced the seepage at the base of the spillway there has not been a reduction in seepage at the water outlet location at the downstream slope electrical resistivity measurements along the eight lines with the dipole dipole array and dye tracer tests were performed in order to identify the seepage locations the interpretation of electrical resistivity data showed the distribution of strata and the seepage zone along the right downstream of the dam groundwater flow rates calculated from dye tests indicated that there is an excessive seepage south eastwardly on the downstream slope of the dam integrated interpretation of resistivity data and dye tests indicate that the seepage paths are in the direction from nw to e and se

elucidating changes in the degree of tracer dispersion in a subglacial channel tracer injections into a subglacial channel at unteraargletscher switzer land were repeated at intervals of about 2 hours over two diurnal discharge cycles in august and september 2000 records of dye concentration reveal a pronounced hysteresis in the velocity dispersion relationship thereby indicating alterations in the drainage system theoretical considerations for ro thlisberger channels suggest an evolution of the conduit cross section in response to a diurnally varying discharge we studied the relation between conduit cross section and tracer dispersion with numerical tracerexperiments thevelocity fieldforsteady flow throughagivenconduitgeometry is calculated using a commercial flow solver tracer transport is represented by a scalar volume which is advected by the velocity field experiments were conducted for several scenarios by varying flow velocity conduit geometry and conduit roughness results show only a weak dependence of dispersion on conduit size in contrast changes in roughness of the conduit walls reveal a strong effect on tracer dispersion therefore to explain the observed hysteresis in the velocity dispersion relationship we suggest that the evolution of a subglacial flow path might involve changes in roughness

do debris covered glaciers demonstrate distinctive hydrological behaviour compared to clean glaciers abstract supraglacial debris is known to strongly influence the distribution of glacier surface melt since melt inputs drive the formation and evolution of glacial drainage systems it should follow that the drainage systems of debris covered glaciers will differ from those of debris free glaciers this would have implications for the proglacial runoff regime subglacial erosion and glacier dynamics this paper presents analysis of return curves from 33 successful dye injections into the extensively debris covered miage glacier italian alps it demonstrates that the spatial distribution of supraglacial debris influences the structure and seasonal evolution of the glacial drainage system where the debris cover is continuous melt is lower and the surface topography is chaotic with many small supraglacial catchments these factors result in an inefficient englacial subglacial drainage network beneath continuous debris which drains to the conduit system emanating from the upper ablation zone melt rates are high in areas of clean and dirty ice above the continuous debris runoff from these areas is concentrated by inter moraine troughs into large supraglacial streams which encourages the early season development of an efficient englacial subglacial conduit system downstream of this area drainage efficiency from the debris covered area increases over the melt season but dye trace transit velocity remains lower than from moulins on the upper glacier future runoff models should account for the influence of supraglacial debris on the hydrological system

geometry and flow conditions of subglacial water at south cascade glacier washington state u s a an analysis of tracer injections tracers were injected into south cascade glacier to determine the flow condition and geometry of the subglacial water system results indicate that two distincts drainage basins on the glacier feed the two main streams flowing from the glacier in the largest basin two parallel drainage networks exist one englacial and the other subglacial

velocity discharge relationships derived from dye tracer experiments in glacial meltwaters implications for subglacial flow conditions repeated dye tracer tests were undertaken from individual moulins at haut glacier d arolla switzerland over a number of diurnal discharge cycles during the summers of 1989 1991 it was hoped to use the concepts of at a station hydraulic geometry to infer flow conditions in subglacial channels from the form of the velocity discharge relationships derived from these tests the results however displayed both clockwise and anticlockwise velocity discharge hysteresis in addition to the simple power function relationship assumed in the hydraulic geometry approach clockwise hysteresis seems to indicate that a moulin drains into a small tributary channel rather than directly into an arterial channel and that discharges in the two channels vary out of phase with each other anticlockwise hysteresis is accompanied by strong diurnal variations in the value of dispersivity derived from the dye breakthrough curve and is best explained by hydraulic damming of moulins or sub englacial passageways despite the complex velocity discharge relationships observed some indication of subglacial flow conditions may be obtained if tributary channels comprise only a small fraction of the drainage path and power function velocity discharge relationships are derived from dye injections conducted during periods when the supraglacial discharge entering the moulin and the bulk discharge vary in phase analyses based on this premise suggest that both open and closed channel flow occur beneath haut glacier d arolla and that flow conditions are highly variable at and between sites

variability in ice motion at a land terminating greenlandic outlet glacier the role of channelized and distributed drainage systems we use a combination of field observations and hydrological modelling to examine the mechanisms through which variability in meltwater input affects ice motion at a land terminating greenlandic outlet glacier we find a close agreement between horizontal ice velocity vertical ice velocity and modelled subglacial water pressure over the course of a melt season on this basis we argue that variation in horizontal and vertical ice velocity primarily reflects the displacement of basal ice during periods of cavity expansion and contraction a process itself driven by fluctuations in basal water pressure originating in subglacial channels this process is not captured by traditional sliding laws linking water pressure and basal velocity which may hinder the simulation of realistic diurnal to seasonal variability in ice velocity in coupled models of glacial hydrology and dynamics

dye tracing a jokulhlaup i subglacial water transit speed and water storage mechanism we present results of an investigation of two j okulhlaups glacial lake outburst floods at gornergletscher switzerland using dye tracer experiments and complementary hydrological measurements repeated dye injections into moulins showed that tracer transit speeds were larger after the lake had emptied but when proglacial discharge was still high than during the main phase of the j okulhlaup this counter intuitive finding was modelled by tracer retardation inside the injection moulin this model together with an estimate of the maximum time the tracer takes to transit the injection moulin allows us to calculate bounds on the transit speed in the main drainage channel where the lake water flows these results indicate that the main drainage channel transit speeds are indeed highest during the peak of the flood moreover it is known from a previous study that water amounting to half of the lake volume is temporarily stored within the glacier during a gornergletscher j okulhlaup our observations suggest that this process occurred via lateral spreading of water at the glacier bed

subglacial drainage processes at a high arctic polythermal valley glacier dye tracer experiments undertaken over two summer melt seasons at polythermal john evans glacier ellesmere island canada were designed to investigate the character of the subglacial drainage system and its evolution over a melt season in both summers dye injections were conducted at several moulins and traced to a single subglacial outflow tracer breakthrough curves suggest that supraglacial meltwater initially encounters a distributed subglacial drainage system in late june the subsequent development and maintenance of a channelled subglacial network are dependent upon sustained high rates of surface melting maintaining high supraglacial inputs in a consistently warm summer 2000 subglacial drainage became rapidly and persistently channelled in a cooler summer 2001 distributed subglacial drainage predominated these observations confirm that supraglacial meltwater can access the bed of a high arctic glacier in summer and induce significant structural evolution of the subglacial drainage system they do not support the view that subglacial drainage systems beneath polythermal glaciers are always poorly developed they do suggest that the effects on ice flow of surface water penetration to the bed of predominantly cold glaciers may be short lived

on the role of mechanical energy in maintaining subglacial water conduits at atmospheric pressure recent theo retical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady state conditions this however is not necessarily the case where discharges are larger than a few tens of liters per second and the down glacier slope of the bed is more than a few degrees the potential energy released by water descending this slope may be capable of melting the walls of a subglacial conduit many times faster than the conduit can close by plastic flow of the ice as a result the pressure in such tunnels may normally be atmospheric or possibly even at the triple point pressure if there is no open connection to the glacier surface simple calcu lations suggest that such pressures in subglacial conduits may be more common than herclofore anticipated the positions of such open conduits may be unstable to small per turbations in discharge or ice veloci ty this is because the mechanical energy available in excess of that needed to balance closure can instead offset the gene ral flow of the ice cond ui ts can thus trend diago nally across the direction of ice aow if an increase in the angle which such a conduit makes with the ice flow direction also results in an increase in slope of he conduit more mechanical energy will become available resulting in a positive feedback process subglacial channels at atmospheric pressure may inauence the origin and morphology of certain glacial landforms such as eskers and plastically molded features resume sur le role de l inergie newtonnienne dam le maintien du riseau aquiflrl sous glaciaire cl la pression almosph irique de recentes etudes theoriques d hydrologie glaciaire ont suppose que le reseau sous glaci aire clait corn pletement rempli d eau en condition d cquil ibre stable ceci neanmoins n est pas necess airement le cas lorsque les debits sonl superieurs a quelques dizaines de litres par seconde et que la pente du lit du glacier est superieure a quelques degres i energie potentielle mise en oeuvre par i eau descendant celle pente peut ire capable de fondre les parois d un chenal sous glaciaire beaucoup plus vite que le chenal ne peut se refermer par le auage plastique de la glace il en resuhe que la pression dans de tels chenaux peut nor rnalement etre atrnospherique

structure morphology and water flux of a subglacial drainage system midtdalsbreen norway digital elevation models of the surface and bed of midtdalsbreen norway are used to calculate subglacial hydraulic potential and infer drainage system structure for a series of subglacial water pressure assumptions ranging from atmospheric to ice overburden a distributed degree day model is used to calculate the spatial distribution of melt on the glacier surface throughout a typical summer which is accumulated along the various drainage system structures to calculate water fluxes beneath the glacier and exiting the portals for the different water pressure assumptions in addition 78 dye tracing tests were performed from 33 injection sites and numerous measurements of water discharge were made on the main proglacial streams over several summer melt seasons comparison of the calculated drainage system structures and water fluxes with dye tracing results and measured proglacial stream discharges suggests that the temporally and spatially averaged steady state water pressures beneath the glacier are 70 of ice overburden analysis of the dye return curves together with the calculated subglacial water fluxes shows that the main drainage network on the eastern half of the glacier consists of a hydraulically efficient system of broad low channels average width height ratio 75 the smaller drainage network on the west consists of a hydraulically inefficient distributed system dominated by channels that are exceptionally broad and very low average width height ratio 350 the even smaller central drainage network also consists of a hydraulically inefficient distributed system dominated by channels that are very broad and exceptionally low average width height ratio 450 the channels beneath the western and central glacier must be so broad and low that they can essentially be thought of as a linked cavity system

seasonal changes in the morphology of the subglacial drainage system haut glacier d arolla switzerland dye tracing techniques were used to investigate the glacier wide pattern of change in the englacial subglacial drainage system of haut glacier d arolla during the ablation seasons of 1990 and 1991 analysis of breakthrough curve characteristics indicate that over the course of a melt season a system of major channels developed by headward growth at the expense of a hydraulically inefficient distributed system by the end of the melt season this channel system extended at least 3 3 km from the snout of the 4 km long glacier and drained the bulk of supraglacially derived meltwater passing through the glacier the upper limit of the channel system closely followed the retreating snowline up glacier rates of headward channel growth reached c 65 m d 1 although these rates decreased in the upper 1 km of the glacier where snowline retreat exposed a patchy firn aquifer it appears that the removal of snow with its high albedo and significant water storage capacity from the glacier surface resulted in a dramatic increase in the volume of runoff into moulins and in the peakedness of daily runoff cycles this induced transient high water pressures within the distributed drainage system which caused it to evolve rapidly into a channelised system it is therefore likely that at a local scale channel growth occurred down glacier from moulins and that the overall up glacier directed pattern of channel formation was caused by the retreating snowline exposing new moulins and crevasses to inputs of ice derived meltwater damping of diurnal melt inputs by storage in the firm aquifer accounts for the slowing of channel growth in the upper glacier 1998 john wiley sons ltd

hydrological controls on diurnal ice flow variability in valley glaciers 1 this paper uses a combination of field data and three dimensional modeling to investigate the spatial variability in basal conditions required to induce observed fluctuations in diurnal ice velocity at haut glacier d arolla switzerland a network of surface velocity markers was observed at intervals of as little as four hours over diurnal cycles in both winter and late summer winter motion showed limited diurnal variability presumably due to the absence of supraglacial meltwater inputs by contrast diurnal fluctuations in ice motion were recorded in summer across the lower and upper glacier in the lower glacier surface velocities were intimately linked to hydrological forcing in the vicinity of a subglacial channel previously observed diurnal excursions of meltwater away from the channel should reduce areas of basal drag adjacent to the channel thereby impacting on ice dynamics using a first order ice flow approximation we investigated the distribution of basal shear traction adjacent to the channel necessary to replicate the observed surface velocity field during periods of rapid ice motion the modeling suggests that the observed variations in diurnal velocity will only occur with extensive reductions in basal drag across a transverse zone of up to 560 m across well beyond the immediate vicinity and previously observed extent of diurnal excursions of meltwater away from the subglacial channel

character of the englacial and subglacial drainage system in the lower part of the ablation area of storglaciaren sweden as revealed by dye trace studies

minor and trace elements as indicators of solute provenance and flow routing in a subglacial hydrological system mitchell a c brown g h fuge r 2006 minor and trace elements as indicators of solute provenance and flow routing in a subglacial hydrological system hydrological processes 20 4 877 897 sponsorship university of wales aberystwyth studentship am university of wales aberystwyth research grants 56 95 and 36 96 ghb and rf and nerc grant no gr3 11216

an experimental investigation of agglutinate melting mechanisms shocked mixtures of sodium and potassium feldspars we report the results of an experiment designed to test the validity of the model for agglutinate formation involving fusion of the finest fraction or f3 papike et al 1981 impact glasses were formed from various mixes of orthoclase and albite powders which were used as analogs for soils with chemically contrasting coarse and fine fractions shock pressures ranged from 31 8 gpa to 78 0 gpa 318 780 kbar results show that the composition of the finest soil fraction is the dominant factor in displacing the composition of the impact melt agglutinate glass from that of the bulk other factors are degree of shock amount of melt and volatile loss a soil with no fine fraction displays only the effects of volatile loss whereas in other runs the glasses are compositionally displaced away from the bulk and toward the finest fraction as predicted by the model the lower pressure melts are the most fractionated higher pressure is accompanied by increased melting causing glass compositions to approach the bulk in general the systematics predicted by the model are observed and it appears that the fusion of the finest fraction model is valid

helium isotopes provide no evidence for deep mantle involvement in widespread cenozoic volcanism across central asia abstract small volume alkali basaltic volcanism has occurred intermittently for the past 30 my across a vast area of thick continental crust from southern siberia through mongolia to northeast china with a lack of evidence for basin and range type crustal extension or rifting models to explain the widely dispersed yet long lived volcanism tend to favour involvement of one or more mantle plume s we examine the range of 3he 4he isotope values in olivine phenocrysts from basalts and their entrained mantle xenoliths from hamar daban in southern siberia and hangai in central mongolia in order to examine whether upwelling lower mantle appears to be present beneath central asia and thus test the validity of the plume model for this region our results show that the maximum 3he 4he value for the siberian basalts is 8 12 0 2ra and the maximum value for mongolian basalts is 9 5 0 5ra these values suggest that there is no significant contribution from a high 3he 4he primordial component that would strongly argue a lower mantle source overlap with commonly reported values for morb leads us to propose that the source of the magmatism derives from the shallow asthenosphere alternative models to a deeply sourced mantle plume that may be able to explain the magmatism include a shallow thermal anomaly confined to the upper mantle but either fed laterally or caused by thermal blanketing of the large asian landmass replacement or delamination of the lowermost lithosphere in response to tectonic stresses or large scale mantle disturbance or overturn caused by a protracted history of subduction beneath central asia that ended regionally with the jurassic closure of the mongol okhotsk ocean but continues further afield with the present indo asia collision

lunar regolith petrology of the 10 μm fraction it has been known for some time that the part of the lunar regolith smaller than 10 micrometers 10 m is chemically distinct from the bulk soil specifically it is enriched in al ca na k light rare earth elements and th and depleted in mg fe mn and sc three models have been proposed to explain those systematics the exotic component model holds that a fine grained kreepy exotic component was distributed on a global scale perhaps by the imbrian impact in the simple comminution model the 10 m chemical systematics are due to differential comminution processes with fine grained melt rock mesostasis and feldspar concentrating in this fraction the soil mixing model states that the chemical systematics are due to mixing of compositionally distinct soils that have different grain size distributions to determine which model is correct modal petrographic data were obtained by scanning transmission electron microscopy with energy dispersive x ray analysis for the 10 m fractions of four apollo soils 10084 14163 15271 and 64501 modal results are consistent with chemical data regarding feldspathic and kreep enrichments in the finest fraction soil glass contents crystalline silica and plagioclase mafic mineral ratios are greater in the 10 m fraction than in the coarser fractions for all soils grain size distributions are inconsistent with a fine grained exotic component derived from distant sources comminution of local lithologies vertical mixing and local lateral transport control the 10 m soil composition

evolution of the subglacial drainage system beneath the greenland ice sheet revealed by tracers predictions of the greenland ice sheet s response to climate change are limited in part by uncertainty in the coupling between meltwater lubrication of the ice sheet bed and ice flow1 2 3 this uncertainty arises largely from a lack of direct measurements of water flow characteristics at the bed of the ice sheet previous work has been restricted to indirect observations based on seasonal and spatial variations in surface ice velocities4 5 6 7 and on meltwater flux8 here we employ rhodamine and sulphur hexafluoride tracers injected into the drainage system over three melt seasons to observe subglacial drainage properties and evolution beneath the greenland ice sheet up to 57 km from the margin tracer results indicate evolution from a slow inefficient drainage system to a fast efficient channelized drainage system over the course of the melt season further inland evolution to efficient drainage occurs later and more slowly an efficient routing of water was established up to 41 km or more from the margin where the ice is approximately 1 km thick overall our findings support previous interpretations of drainage system characteristics thereby validating the use of surface observations as a means of investigating basal processes

impact of subglacial hydrology on the release of water from temporary storage in an alpine glacier periods of storage and release of surface runoff that is routed englacially and subglacially are identified from a time series of cumulative water balance between 31 july and 11 september 1999 at findelengletscher switzerland the influence of subglacial hydrology on water routing within the glacier and therefore on trends of water storage and release is determined through comparisons of phase relationships between daily maxima daily minima and diurnal ranges of borehole water levels supraglacial runoff and proglacial discharge variations of water levels in 21 boreholes in the ablation zone suggest that although subglacial drainage is spatially dynamic hydrologically efficient tunnel conduit style drainage dominates diurnal cycles of water transfer through the glacier over longer periods however storage and release of subglacially routed water is greatly influenced by the coexistence of and temporary interconnections between hydrologically inefficient distributed drainage and the tunnel conduit network water levels in three boreholes indicate that after water storage increases in distributed drainage hydraulic gradients between the different drainage systems may increase sufficiently to cause connections that initiate release of water when 1 low maximum daily surface runoff causes low water pressures in the tunnel conduit system or 2 reorganization within distributed drainage causes spatially localized increases in water pressure

using concurrent dna tracer injections to infer glacial flow pathways author s dahlke he williamson ag georgakakos c leung s sharma an lyon sw walter mt abstract 2015 john wiley a sons ltd catchment hydrology has become replete with flow pathway characterizations obtained via combinations of physical hydrologic measurements e g streamflow hydrographs and natural tracer signals e g stable water isotopes and geochemistry in this study we explored how our understanding of hydrologic flow pathways can be improved and expanded in both space and time by the simultaneous application of engineered synthetic dna tracers in this study we compared the advective dispersive transport properties and mass recovery rates of two types of synthetic dna tracers one consisting of synthetic dna strands encapsulated into biodegradable microspheres and another consisting of free dna i e not encapsulated the dna tracers were also compared with a conservative fluorescent dye all tracers were injected into a small 3 2 km2 valley glacier storglaciaren in northern sweden seven of the nine dna tracers showed clear recovery during the sampling period and similar peak arrival times and dispersion coefficients as the conservative fluorescent dye however recovered dna tracer mass ranged only from 1 to 66 while recovered fluorescent dye mass was 99 resulting from the cold and opaque subglacial environment provided by the glacier mass loss associated with microbial activity and photochemical degradation of the dna is likely negligible leaving sorption of dna tracers onto suspended particles and loss of microtracer particles to sediment storage as probable explanations despite the difference in mass recovery the advection and dispersion information derived from the dna tracer breakthrough curves provided spatially explicit information that allowed inferring a theoretical model of the flow pathways that water takes through the glacier

bayesian inference of subglacial channel structures from water pressure and tracer transit time data a numerical study based on a 2 d geostatistical modeling approach

evolution of the internal drainage system in the lower part of the ablation area of storglaci aren sweden during the 1989 melt season ten tracer experiments were conducted to investigate seasonal diurnal and spatial variations in the internal drainage system in the ablation area of storglaciaren sweden dye was injected into moulins and dye concentration and discharge were monitored in two streams at the glacier terminus sydjakk and nordjakk dye emerged only in sydjakk transit velocities ranged from 0 07 to 0 29 m s implying that drainage was through a well defined conduit system velocity and discharge relations suggest that these conduits are part of a multi branched arborescent network of individually braided wide low passages a progressive decline in dispersivity during the early part of the melt season reflects structural changes in these conduits presumably including a decrease in the degree of braiding and an increase in size the system reached its late season configuration in early august by which time the energy dissipated by the flowing water would have sufficed to melt between 0 7 and 21 m 3 of ice per meter of conduit length depending on conduit size potential closure rates exceed melt rates on conduit walls throughout most of the drainage system and so conduits are probably full of water during periods of higher daily discharge with water pressures exceeding atmospheric pressure variations in tracer return curves and dispersivity on a diurnal time scale also appear to reflect changes in the degree of braiding in this case resulting from drowning of low divides between channels as discharge increases

insights into combined radiogenic and stable strontium isotopes as tracers for weathering processes in subglacial environments this study reports stable and radiogenic strontium isotope behaviour in the dissolved load and suspended sediments from the subglacial outflow of the lemon creek glacier juneau ice field alaska over a single melt season in situ measurements discharge total alkalinity ph and conductivity are combined with elemental concentrations x ray diffraction xrd analysis and radiogenic strontium isotope measurements to interpret the variations observed in stable strontium isotopic ratios the stable sr isotope composition 88sr 86sr ratio expressed as 88 86sr of the dissolved load averages 0 31 0 05 and is heavier than both the suspended sediment 0 18 0 03 as well as local bedrocks 0 20 to 0 26 we attribute the enrichment of heavier isotopes in the dissolved load to the uptake of lighter sr isotopes by secondary weathering minerals driving the dissolved load to heavier values x ray diffraction xrd analysis confirms the presence of clays in the suspended sediments and thermodynamic modelling suggests the presence of iron oxy hydroxide phases although it is not possible to completely rule out the effect of dissolution of primary minerals in controlling sr isotopic compositions of the dissolved load our data indicate that the extent of secondary mineral formation likely plays a significant role the preferential weathering of minerals such as biotite consistent with the mineralogical assemblages found in the suspended sediments as well as the potential presence of radiogenic calcites from metacarbonates derived from the yukon tanana terrain may be driving the small seasonal shifts in 87sr 86sr of the dissolved load to more radiogenic compositions from 87sr 86sr dl 0 71048 to 0 710647 using the combination of stable and radiogenic strontium isotopes to investigate weathering processes shows that radiogenic sr isotopes provide information regarding weathering of primary phases while the stable sr isotope data appear to record information regarding the extent of secondary mineral formation where secondary minerals incorporate the light isotopes driving the dissolved load to heavy values

character of the subglacial drainage system in the ablation area of dokriani glacier india as revealed by dye tracer studies abstract the character of the subglacial drainage system is best determined by the dye tracer technique ten dye tracer experiments were conducted at three moulins at 930 1700 and 2300 m respectively from the measurement site on the dokriani glacier garhwal himalaya india the injections were made during july august and september 2000 in july the subglacial drainage appeared to be via efficient trunk channels which resulted in dye concentration curves with velocities between 0 37 and 0 47 m s 1 in august and september drainage was active mainly in the inefficiently distributed system as velocity declined and varied between 0 10 and 0 39 m s 1 probably the distributed system during august expanded to accommodate the increased runoff by the seasonal high discharges limited observations indicate that there was temporal switching between channelised and distributed drainage system

subglacial drainage system structure and morphology of brewster glacier new zealand a global positioning system and ground penetrating radar surveys is used to produce digital elevation models of the surface and bed of brewster glacier these are used to derive maps of subglacial hydraulic potential and drainage system structure using three different assumptions about the subglacial water pressure pw i pw ice overburden ii pw half ice overburden iii pw atmospheric additionally 16 dye tracing experiments at 12 locations were performed through a summer melt season dye return curve shape together with calculations of transit velocity dispersivity and storage are used to infer the likely morphology of the subglacial drainage system taken together the data indicate that the glacier is underlain by a channelised but hydraulically inefficient drainage system in the early summer in which water pressures are close to ice overburden by mid summer water pressures are closer to half ice overburden and the channelised drainage system is more hydraulically efficient surface streams that enter the glacier close to the location of major subglacial drainage pathways are routed quickly to the channels and then to the glacier snout streams that enter the glacier further away from the drainage pathways are routed slowly to the channels and then to the snout because they first flow through a distributed drainage system copyright 2008 john wiley sons ltd

diurnal hydrological physicochemical controls and sampling methods for minor and trace elements in an alpine glacial hydrological system summary we present diurnal i 0 45 and 0 1 m pore size filtered and ii operationally defined labile particulate associated major minor and trace element concentrations and fluxes in glacial outflow waters draining haut glacier d arolla switzerland we use speciation modelling phreeqci and water suspended sediment interaction experiments are utilised under conditions analogous to the subglacial channellised hydrological system in order to assess controls on and the most suitable sampling methods to investigate short term variations in the mode of major minor and trace element species export from a glacierised headwater catchment 0 45 m pore size filtered major ions sr and u are exported in glacial outflow waters predominately as mobile monovalent or divalent ions or as carbonate complexes and are controlled by hydrological variations over diurnal cycles exhibiting an inverse concentration with increasing meltwater discharge conversely 0 45 m pore size filtered concentrations of most minor and trace elements e g fe mn co ba and pb exhibit variations that are not strongly inter correlated with meltwater discharge or suspended sediment concentrations ssc over diurnal periods the use of 0 45 and 0 1 m pore size filter membranes indicates that significant colloidal material is not passing through the 0 45 m pore size filters and these unsystematic variations are not a result of colloid measurement speciation modelling applied to meltwaters and observations during water rock interaction experiments suggest that these unsystematic temporal variations reflect physicochemical controls this includes sorption and the oversaturation and precipitation of fe and al oxi hydroxides and the co precipitation of other species diurnal ph variations appear important in controlling such short term physicochemical controls which limits such species use for hydrological investigations the percentage of total elemental fluxes exported as the labile particulate associated flux paf for each minor and trace element changes dramatically between and during the diurnal cycles reflecting species specific sensitivity to hydrological and physicochemical controls hydrological interpretations of hydrochemical data must be made carefully when using chemical determinations by icp ms since we demonstrate that measurements will comprise of any material that passes through the filter this can lead to higher concentration measurements than if determined by ion chromatography which measures truly ionic dissolved species

quantifying the effects of glacier conduit geometry and recharge on proglacial hydrograph form summary the configuration of glacier hydrological systems is often inferred from proxy data such as hydrographs that are collected in proglacial streams seasonal changes in the peakedness of hydrographs are thought to reflect changes in the configuration of the subglacial drainage system however the amount of information that proglacial hydrographs contain about drainage system configurations depends critically on the degree to which the drainage systems modify recharge hydrographs if the drainage system does not modify recharge hydrographs then proglacial hydrographs primarily reflect the recharge conditions produced by supraglacial inputs here we develop a theoretical framework to determine the circumstances under which glacier drainage systems can modify recharge hydrographs and the circumstances under which recharge pulses pass through glaciers unchanged we address the capability of single conduits simple arborescent conduit networks and linked cavity systems to modify diurnal recharge pulses simulations of discharge through large sets of such systems demonstrate that unless large reservoirs or significant constrictions are present the discharge hydrographs of simple glacial conduit systems are nearly identical to their recharge hydrographs conduit systems tend not to modify hydrographs because the changes in storage within englacial and subglacial conduit networks on short time scales are typically small compared to their ability to transmit water this finding suggests that proglacial hydrographs reflect a variety of factors including surface melt rate surface water transfer and subglacial water transfer in many cases the influence of suglacial processes may be relatively minor as a result the evolution of proglacial hydrographs cannot be used unambiguously to infer changes in the structure or efficiency of englacial or subglacial hydrological systems without accurate knowledge of the nature of the recharge hydrograph driving the flow

evolution of drainage system morphology at a land terminating greenlandic outlet glacier 1 the influence of meltwater on the dynamics and geomorphic impact of the greenland ice sheet is strongly controlled by the morphology of the ice sheet s drainage system however this system and its evolution through the melt season remain poorly understood here we present the results of an intensive programme of dye tracing experiments undertaken along the lower 14 km of a land terminating greenlandic outlet glacier over a period of four months during the 2010 melt season these data are interpreted in conjunction with observations of proglacial discharge englacial water storage surface melt rates and ice velocity to produce a detailed picture of the changing hydrology of the glacier following the onset of melt in the spring inputs to the drainage system regularly exceed outputs causing the englacial water level to rise to the ice sheet surface during this time there is a rapid transition from distributed to channelized drainage in those parts of the drainage system closed by ice deformation over winter as the melt season progresses channel efficiency increases and englacial storage and ice velocity decrease high velocity events continue to be observed following the channelization of the drainage system however indicating that hydrological forcing of ice velocity occurs despite the existence of channels during periods when meltwater inputs exceed the capacity of the subglacial drainage system

glacier meltwater hydrochemistry abstract glacierised areas present an ideal environment in which to study water rock interaction since chemical weathering rates are high and anthropogenic impacts are often minimal detailed investigations of meltwater quality variations have suggested the importance of these environments in estimates of terrestrial chemical erosion and global biogeochemical cycles most notably the role of meltwaters in co2 sequestration during episodes of deglaciation has attracted considerable attention since this may impact on climate at glacial interglacial timescales however there is still considerable uncertainty surrounding estimates of co2 drawdown by meltwaters which remains to be resolved water flow through glaciers exerts an important control on ice mass dynamics and influences the quantity and quality of water delivered to environments downstream of glacierised basins thus the study of the configuration and dynamics of subglacial drainage systems is important not only to enhance scientific understanding but also to allow effective water resource utilisation in glacierised headwater catchments bulk meltwater quality characteristics draining terrestrial ice masses also offer the potential to provide unique information on hydrological and hydrochemical processes operating in the inaccessible subglacial environment here significant advances have been made in understanding the controls on chemical weathering reactions based on the identification of key dissolved indicator species this has allowed water quality variations to be exploited as a tool for both subglacial hydrochemical and hydrological investigations as a result this area of glaciology has received considerable attention in recent years utilising an increasing range of dissolved ions and integrating field and laboratory studies however uncertainty still surrounds certain areas of meltwater quality science including the role of microorganisms in a system which to date has largely been viewed as abiotic a better understanding of the processes and rates of chemical weathering in glacierised environments has the potential to enhance our understanding of the environment and to facilitate the exploitation of water quality variations for both scientific and applied objectives in this paper the development and current state of meltwater quality science as a tool for investigating subglacial hydrology and geochemistry is detailed and problems and future directions identified this will hopefully stimulate wider interest in an important area of aquatic chemistry with significant applied implications

modelling the evolution of subglacial tunnels due to varying water input the time evolution ofa subglacial tunnel cross section is examined using a two dimensional finite element ice flow model coupled to an idealized drainage system simulations are driven by physically based calculations of surface water input variations at storglaciaren sweden highlights of the model are its ability to handle unsteady conditions and irregular tunnel shapes agreement between modelled water pressure and borehole water levels is good the following conclusions are reached i tunnels adapt to fluctuating inflow on time scales of days storms during which effective pressure ranges from 0 to 0 9 mpa cause significant adjustments but daily fluctuations due solely to meltwater inflow are minor ii open channel flow may become commonplace late in the ablation season iii initial tunnel shape influences subsequent tunnel evolution and seasonal water pressure variation over the course of a summer tunnels retain some of their initial shape though in all experiments the width to height ratio increased with time iv tunnel contraction forms broad low tunnels however v given two tunnels of equal initial area the higher narrower one expands more rapidly thus more semi circular tunnels may capture flow from broader neighbours early in the summer

initial results from a distributed physically based model of glacier hydrology this paper describes the development and testing of a distributed physically based model of glacier hydrology the model is used to investigate the behaviour of the hydrological system of haut glacier d arolla valais switzerland the model has an hourly time step and three main components a surface energy balance submodel a surface flow routing submodel and a subglacial hydrology submodel the energy balance submodel is used to calculate meltwater production over the entire glacier surface the surface routing submodel routes meltwater over the glacier surface from where it is produced to where it either enters the subglacial hydrological system via moulins or runs off the glacier surface the subglacial hydrology submodel calculates water flow in a network of conduits which can evolve over the course of a melt season simulation in response to changing meltwater inputs the main model inputs are a digital elevation model of the glacier surface and its surrounding topography start of season snow depth distribution data and meteorological data model performance is evaluated by comparing predictions with field measurements of proglacial stream discharge subglacial water pressure measured in a borehole drilled to the glacier bed and water velocities inferred from dye tracer tests the model performs best in comparison with the measured proglacial stream discharges but some of the substantial features of the other two records are also reproduced in particular the model results show the high amplitude water pressure cycles observed in the borehole in the mid melt season and the complex velocity discharge hysteresis cycles observed in dye tracer tests the results show that to model outflow hydrographs from glacierized catchments effectively it is necessary to simulate spatial and temporal variations in surface melt rates the delaying effect of the surface snowpack and the configuration of the subglacial drainage system itself the model s ability to predict detailed spatial and temporal patterns of subglacial water pressures and velocities should make it a valuable tool for aiding the understanding of glacier dynamics and hydrochemistry 1998 john wiley sons ltd

chemical models of solute acquisition in glacial melt waters chemical models for the evolution of bulk melt waters can be constructed by assuming that rock mineral weathering and solute acquisition are controlled by carbonate equilibria different open and closed system models are defined by variations in the rates of weathering relative to the rate of hydrogen ion supply by the dissolution and dissociation of co2 and can be recognized by characteristic ph and relationships the observed and inferred compositions of englacial and subglacial melt suggest that mixing is unlikely to be conservative and that closed system conditions result where post mixing weathering reactions occur the final composition of bulk melt waters is determined by the mixing ratio between englacial and subglacial melt the extent of post mixing evolution and opportunity for mixing with ground waters or re equilibration with the atmosphere

comments on character of the englacial and subglacial drainage system in the lower part of the ablation area of storglaciaren sweden as revealed by dye trace studies