weathering and the mobility of phosphorus in the catchments and forefields of the rhone and oberaar glaciers central switzerland implications for the global phosphorus cycle on glacial interglacial timescales abstract in this study we evaluate the dynamics of the biophile element phosphorus p in the catchment and proglacial areas of the rhone and oberaar glaciers central switzerland we analysed erosion and dissolution rates of p containing minerals in the subglacial environment by sampling water and suspended sediment in glacier outlets during three ablation and two accumulation seasons we also quantified biogeochemical weathering rates of detrital p in proglacial sedimentary deposits using two chronosequences of samples of fresh suspended material obtained from the oberaar and rhone water outlets little ice age lia moraines and younger dryas yd tills in each catchment subglacial p weathering is mainly a physical process and detrital p represents more than 99 of the precipitation corrected total p denudation flux 234 and 540 kg km 2 yr 1 for the rhone and oberaar catchments respectively the calculated detrital p flux rates are three to almost five times higher than the world average flux the precipitation corrected soluble reactive p srp flux corresponds to 1 88 1 99 kg km 2 yr 1 rhone and 2 12 2 44 kg km 2 yr 1 oberaar respectively these fluxes are comparable to those of tropical rivers draining transport limited tectonically inactive weathering areas in order to evaluate the efficiency of detrital p weathering in the rhone and oberaar proglacial areas we systematically graded apatite grains extracted from the chronosequence in each catchment relative to weathering induced changes in their surface morphologies grades 1 4 fresh apatite grains are heavily indented and dissolution rounded grade 1 lia grains from two 0 10 cm deep moraine samples show extensive dissolution etching similar to surface grains from the yd profile mean grades 2 7 3 5 and 3 5 respectively in these proglacial deposits the weathering front deepens progressively as a function of time due to biocorrosion in the evolving acidic pedosphere with mechanical indentations on grains acting as sites of preferential dissolution we also measured iron bound organic and detrital p concentrations in the chronosequence and show that organic and iron bound p has almost completely replaced detrital p in the top layers of the yd profiles detrital p weathering rates are calculated as 310 and 280 kg km 2 yr 1 for lia moraines and 10 kg km 2 yr 1 for yd tills during the first 300 years of glacial sediment exposure p dissolution rates are shown to be approximately 70 times higher than the mean global dissolved p flux from ice free continents after 11 6 kyr the flux is 2 5 times the global mean these data strengthen the argument for substantial changes in the global dissolved p flux on glacial interglacial timescales a crude extrapolation from the data described here suggests that the global dissolved p flux may increase by 40 45 during the first few hundred years of a deglaciation phase

solute provenance transport and denudation in a high arctic glacierized catchment recent understanding of chemical weathering in glacierized catchments has been focused on mid latitude alpine catchments comparable studies from the high latitudes are currently lacking this paper attempts to address this deficiency by examining solute provenance transport and denudation in a glacierized catchment at 78 n in the svalbard high arctic archipelago representative samples of snow glacier ice winter proglacial icing and glacier meltwater were obtained from the catchment during spring and summer 1993 and analysed for major ion chemistry seasonal variations in the composition of glacier meltwater occur and are influenced by proglacial solute acquisition from the icing at the very start of the melt season and subsequently by a period of discharge of concentrated snowmelt caused by snowpack elution weathering within the ice marginal channels that drain the glacier particularly carbonation reactions continues to furnish solute to meltwater when suspended sediment concentrations increase later in the melt season partitioning the solute flux into its various components sea salt crustal aerosol and atmospheric sources shows that c 25 of the total flux is sea salt derived consistent with the maritime location of the glacier and c 71 is crustally derived estimated chemical denudation 160 meq m 2 a 1 sea salt corrected cation equivalent weathering rate is somewhat low compared with other studied glacierized catchments estimates in the range 450 1000 meq m 2 a 1 which is probably attributable to the relatively short melt season and low specific runoff in the high arctic a positive relationship was identified between discharge and co 2 drawdown owing to carbonation reactions in turbid meltwater

global chemical erosion during the last glacial maximum and the present sensitivity to changes in lithology and hydrology geographically based calculations for 18 000 years ago 18 ka and today were made to examine the potential effects on terrestrial chemical erosion of changes in lithology and hydrology on glacial interglacial timescales runoff fields were derived from general circulation model predictions of precipitation minus evaporation then global lithologic maps were prepared so that empirical relationships for runoff versus bicarbonate flux for different rock types could be used to calculate global chemical erosion rates assuming that significant chemical erosion does not occur beneath ice sheets we find that chemical erosion in ice free areas at 18 ka was only slightly greater than today this result arises because the amount of land covered by ice sheets is roughly compensated for by exposed shelf areas and because there is little difference in global runoff the small 20 increase in the global chemical erosion rate during glacial conditions is due to exposure on the shelves of a relatively high proportion of carbonates which weather faster than average data on glacial interglacial movements of the calcite compensation depth ccd are inconclusive but seem to indicate little change whereas even a 20 increase in the riverine bicarbonate flux should cause an observable deepening if the ccd did not indeed change then our predicted increase in the bicarbonate flux from land during glaciations would have to be accommodated by other means such as increased carbonate productivity about half of the observed decrease in atmospheric pco2 at 18 ka could be explained if increased silicate chemical erosion accompanied increased total chemical erosion in ice free areas consideration of the maximum possible effect of meltwater at ice margins leads to an 80 increase in the global chemical erosion rate at 18 ka such an increase would lead to a larger and faster drop in atmospheric pco2 but also to an excessive deepening of the global ccd this scenario seems unrealistic our results are contrary to interpretations of a much higher silicate chemical erosion rate during glaciations based on recently published records of quaternary marine sr isotopic ratios therefore if these records are indeed globally representative and entirely due to increased silicate chemical erosion as opposed to changes in source areas or hydrothermal inputs then other factors such as a shift in the global weathering regime which we do not explicitly consider here may be involved sensitivity tests show that considering spatial heterogeneities in lithology and runoff leads to lower predictions of global chemical erosion rates than what one would obtain by considering only global averages in a non spatially resolved calculation

the sulphur isotope and hydrochemical characteristics of skeiðararsandur iceland identification of solute sources and implications for weathering processes the hydrochemistry of sulphur in the active outwash plain of skeioararsandur se iceland shows considerable variety reflecting differences in sources and processes and is investigated in this article using 34 s values of dissolved sulphate and igneous sulphide minerals 18 o h2o and ionic concentrations in waters seawater derived sulphate is a notable component only in the lower sandur 34 s so4 6 8 vcdt 34 s so4 in the skeioara glacial melt river range from 3 4 to 8 8 34 s the higher values occur during a flood event and reflect geothermal sulphate contributions from the grimsvotn caldera kettle hole lakes formed since the november 1996 jokulhlaup form important ecological niches and show evidence of coupled sulphide oxidation and carbonate and possibly silicate dissolution and have the lowest 34 s so4 values average 0 8 attributed to higher proportions of sulphide oxidation derived so 4 2 and or bacterially mediated sulphide oxidation the hydrochemistry of eastern sandur groundwater is influenced by a hydrothermal source of reduced sulphur from the grimsvotn caldera or a localized area of geothermal springs and contrasts with the hydrochemistry of the majority of groundwaters and the sula and gigjukvisl rivers in western and central skeioararsandur these have lower ca 2 mg 2 na k and so 4 2 concentrations and 34 s values consistent with sulphate derived from the oxidation of igneous sulphides in comparison to catchments dominated by atmospherically transported sulphate catchments such as this where the sulphur system is dominated by internal sources rock derived and geothermal will not be sensitive to the temporal decreasing trends in contributions from long range airborne sulphate resulting from reductions of sulphur emissions in north america and europe

the hydrochemistry of meltwaters draining a polythermal based high arctic glacier south svalbard i the ablation season solute and runoff time series at finsterwalderbreen svalbard provide evidence for considerable basal routing of water and the existence of at least two contrasting subglacial chemical weathering environments the hydrochemistry of a subglacial upwelling provides evidence for a snowmelt fed subglacial reservoir that dominates bulk runoff during recession flow high concentrations of cl and crustal ions high pco2 and ratios of so2 4 so2 4 hco 3 close to 0 5 indicate the passage of snowmelt through a subglacial weathering environment characterized by high rock water ratios prolonged residence times and restricted access to the atmosphere at higher discharges bulk runoff becomes dominated by icemelt from the lower part of the glacier that is conveyed through a chemical weathering environment characterized by low rock water ratios short residence times and free contact with atmospheric gases these observations suggest that icemelt is routed via a hydrological system composed of basal ice marginal englacial and supraglacial components and is directed to the glacier margins by the ice surface slope upwelling water flows relatively independently of icemelt to the terminus via a subglacial drainage system possibly constituting flow through a sediment layer cold basal ice at the terminus forces it to take a subterranean routing in its latter stages the existence of spatially discrete flow paths conveying icemelt and subglacial snowmelt to the terminus may be the norm for polythermal based glaciers on svalbard proglacial mixing of these components to form the bulk meltwaters gives rise to hydrochemical trends that resemble those of warm based glaciers these hydrochemical characteristics of bulk runoff have not been documented on any other glacier on svalbard to date and have significance for understanding interactions between thermal regime and glacier hydrology 1998 john wiley sons ltd

enhancement of glacial solute fluxes in the proglacial zone of a polythermal glacier annual proglacial solute fluxes and chemical weathering rates at a polythermal high arctic glacier are presented bulk meltwater chemistry and discharge were monitored continuously at gauging stations located at the eastern and western margins of the glacier terminus and at the outlet 2 5 km downstream where meltwaters discharge into the fjord fluxes of non snowpack hco 3 so 4 2 ca 2 and mg 2 increase by 30 47 between the glacier terminus and the outlet indicating that meltwaters are able to access and chemically weather efflorescent sulphates carbonates and sulphides in the proglacial zone smaller increases in the fluxes of non snowpack derived na k and si indicate that proglacial chemical weathering of silicates is less significant en3hanced solute fluxes in the proglacial zone are mainly due to the chemical weathering of active layer sediments the pco 2 of active layer ground waters is above atmospheric pressure this implies that solute acquisition in the active layer involves no drawdown of co 2 the annual proglacial chemical weathering rate in 1999 is calculated to be 2600 meq m 2 this exceeds the chemical weathering rate for the glaciated part of the catchment 790 meq m 2 by a factor of 3 3 hence the proglacial zone at finster walderbreen is identified as an area of high geochemical reactivity and a source of co 2

comparison of radio echo sounding 30 1000 mhz and high resolution borehole temperature measurements at finsterwalderbreen southern spitsbergen svalbard

solute generation and transfer from a chemically reactive alpine glacial proglacial system the environs of the glacier de tsanfleuron switzerland was used as a study site to investigate the controls on the relative efficiency of solute generation and removal from glacial and proglacial environments here a 1500 m wide glacier forefield consists of a karstic limestone plateau flanked to the north by a till floored valley bedrocks and glacial debris are composed of chemically reactive pure and impure mesozoic and tertiary limestones with accessory pyrite spot sampling of ice snow and meltwaters in the late melt season was supplemented by systematic measurements of the main meltstream including during periods of rainfall and simple laboratory leaching and weathering experiments isotopic parameters were used to investigate water sources most meltwater and glacier ice samples lay close to a meteoric water line d 8 3 18o 14 defined by waters from small tributary streams heavy isotopic excursions of bulk meltwater chemistry were caused by rainfall events recovering within days to a 18o baseline around 12 permil no regular diurnal variations in 18 o were apparent the atmosphere is the source of cl and most na but the bulk of other solutes are generated in the environment ion loads of up to 1 meq l 1 are rapidly attained by calcite dissolution over periods of weeks to months pyrite oxidation generates sulphate and acidity that drives further calcite dissolution low water rock ratio weathering environments have characteristically high so42 mg2 sr2 and ratios of these species to calcium the characteristic cation ratios are influenced by non congruent calcite dissolution the ratio of sulphate to other species is highest where water rock contact times are highest although this relationship is complicated by spatial variations in pyrite abundance meltstream time series illustrate that 90 per cent of daily ion yields in fine weather are concentrated in the 12 h time period of higher discharge ion yields increase downstream mainly by a combination of dissolution of calcareous suspended sediment and input from tributaries and seepage from the till banks rainstorms lead to increased solute concentrations and resulting hourly fluxes can match daily fine weather ion fluxes excess nitrate appears to be largely sourced from the proglacial surface the capacity of the proglacial environment for yielding significant subsurface water as a result of the storm seems low unlike non glacial environments this implies that most of the excess solutes mobilized by storms comes from subglacial sources increased efficiency of yield of solutes from low water rock ratio subglacial weathering environments persists after the isotopic signature of the rainfall event has died away a simple conceptual model of the sources of water and solutes agrees with conclusions from attempts at hydrograph separation that mixing of water reservoirs of fixed solute composition cannot be used for quantitative descriptions of the system estimated annual solute yields 17 ton per km2 per m precipitation are high but cannot be readily expressed in purely areal terms because of likely significant losses to the underlying karstic system a tentative conclusion is that the proglacial environment is overall less efficient at producing solutes than the glacial environment but more information is required on processes in the early melt season to substantiate this statement copyright 1999 john wiley sons ltd

a comparison of the styles of deformation associated with two recent push moraines south van keulenfjorden svalbard in this paper two push moraine systems associated with two small subpolar glaciers finsterwalderbreen and penckbreen were investigated this study showed that at these glaciers the push moraines were formed in association with surges which produced a different style of moraine depending on the rheology of the deformed material and the glacial history the moraines are similar in that they are formed by folded outwash sediments and contain little till however the forms of these moraines are very different the penckbreen moraine is composed of a lower shallow marine sand silt and clay and an upper fluvial sand and gravel deformation at this site led to the formation of large anticlines in the silts and clays with disharmonic smaller folds and thrusts in the upper gravels above a detachment surface between the fine grained and overlying coarse grained lithologies this deformation decreases towards the foreland with marine and fluvial sediments responding differently because of their different rheological properties this moraine was formed during one surge event which occured during the early 19th century in contrast the finsterwalderbreen moraine is composed of outwash sand and gravel and was formed as the result of a series of surge events these advances all reached a similar limit and occurred at regular intervals 1997 john wiley sons ltd

correlation between iron and magnesium and its significance on the distribution of heavy metals in deep sea cherts abstract concentrations of fe mg ca sr mn zn and other heavy metals were analyzed by atomic absorption spectrometry in 27 chert samples from the pacific deep sea 17 chert samples from land and 4 associated sediments from the pacific ocean among the elements fe and mg concentrations are highly correlatable as are the relationships between ca and sr or between ca and co 2 the correlation between fe and mg is particularly high for pacific deep sea flints and cherts and for cherts of deep sea origin from outcrops on land enrichments in heavy metals were recognized in some deep sea cherts volcanogenic cherts are enriched in fe a chert nodule containing basaltic fragments is enriched in zn and cr and biogenically enclosed carbonates in flint nodules are enriched in mn the correlation of fe and mg and their constant ratio mg fe of around 0 33 might be characteristic features in the pelagic clays contained in deep sea flints and cherts and the concentrations of heavy metals in them would be controlled by the concentrations of fe mg correlated clays although the mineralogical nature of the fe mg clay in deep sea cherts was not clarified by dissolution experiments on opaline minerals in chert the high concentrations of fe montmorillonite and fine grained olivine or other ferromagnesian silicate minerals in the clay may result in the high correlations between fe and mg

geochemical weathering at the bed of haut glacier d arolla switzerland a new model waters were sampled from 17 boreholes at haut glacier d arolla during the 1993 and 1994 ablation seasons three types of concentrated subglacial water were identified based on the relative proportions of ca 2c h co 3 and so4 2 to si type a waters are the most solute rich and have the lowest relative proportion of si they are believed to form in hydrologically inefficient areas of a distributed drainage system most solute is obtained from coupled sulphide oxidation and carbonate dissolution so cd it is possible that there is a subglacial source of o2 perhaps from gas bubbles released during regelation because the high so4 2 levels found up to 1200 eq l are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 c c 414 eq l a more likely alternative is that sulphide is oxidized by fe 3c in anoxic environments if this is the case exchange reactions involving fe iii and fe ii from silicates are possible these have the potential to generate relatively high concentrations of hco3 with respect to so4 2 formation of secondary weathering products such as clays may explain the low si concentrations of type a waters type b waters were the most frequently sampled subglacial water they are believed to be representative of waters flowing in more efficient parts of a distributed drainage system residence time and reaction kinetics help determine the solute composition of these waters the initial water rock reactions are carbonate and silicate hydrolysis and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites hydrolysis is followed by so cd the so4 2 concentrations usually are 414 eq l although some range up to 580 eq l which suggests that elements of the distributed drainage system may become anoxic type c waters were the most dilute yet they were very turbid their chemical composition is characterized by low so4 2 h co3 ratios and high ph type c waters were usually artefacts of the borehole chemical weathering environment true type c waters are believed to flow through sulphide poor basal debris particularly in the channel marginal zone the composition of bulk runoff was most similar to diluted type b waters at high discharge and was similar to a mixture of type b and c waters at lower discharge these observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric co2 t he progression of reactions is from carbonate and silicate hydrolysis through sulphide oxidation by first oxygen and then fe iii which drives further carbonate and silicate weathering a crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 1 we speculate that microbial oxidation of organic carbon also may occur both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions hence we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric co2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity which catalyses the reduction of fe iii and the oxidation of fes2 copyright 2002 john wiley sons ltd

precambrian scotland as a laurentia gondwana link origin and significance of cratonic promontories refinement of the supercontinental reconstruction for the latest precambrian that places the labrador greenland promontory of laurentia within the arica embayment along the margin of the gondwana craton juxtaposes the rockall microcontinent and northwestern british isles with the continental margin of peru the conjugate cratonic margin to the northwest caledonian foreland the hebridean shield may have been amazonia possible south american correlatives of the precambrian moinian and dalradian complexes of the scottish highlands can be identified in the reconstruction notably there are possible equivalents of the older granites within the moinian and of dalradian glacial deposits therefore the well studied precambrian rocks of the scottish highlands provide critical tests for the suggested reconstruction the latest precambrian setting of the arequipa massif with respect to the gondwana craton margin and the paleozoic intracratonic basin of peru bolivia bears a striking similarity to the early mesozoic setting of the rockall plateau and northwestern british isles with respect to the european continental margin and the north sea western approaches graben system in each case rifting appears to have been controlled by the youngest and presumably weakest lithosphere but the extremity of the labrador scotland greenland promontory was detached during final continental separation in vendian to earliest cambrian time to form the arequipa massif and in jurassic time to form the hebridean shield the promontory may have played an important tectonic role through at least 1 b y of earth history including influence on the development of the andean cordillera features of this type likely have played a major role in the development of orogenic belts of all ages

variability in the chemical composition of in situ subglacial meltwaters meltwaters collected from boreholes drilled to the base of the haut glacier d arolla switzerland have chemical compositions that can be classified into three main groups the first group is dilute whereas the second group is similar to though generally less concentrated in major ions than contemporaneous bulk glacial runoff the third group is more concentrated than any observed bulk runoff including periods of flow recession waters of the first group are believed to represent supraglacial meltwater and ice melted during drilling limited solutes may be derived from interactions with debris in the borehole the spatial pattern of borehole water levels and borehole water column stratification combined with the chemical composition of the different groups suggest that the second group represent samples of subglacial waters that exchange with channel water on a diurnal basis and that the third group represent samples of water draining through a distributed subglacial hydraulic system high no 3 concentrations in the third group suggest that snowmelt may provide a significant proportion of the waters and that the residence time of the waters at the bed in this particular section of the distributed system is of the order of a few months the high no 3 concentrations also suggest that some snowmelt is routed along different subglacial flowpaths to those used by icemelt the average so2 4 hco 3 so2 4 ratio of the third group of meltwaters is 0 3 suggesting that sulphide oxidation and carbonate dissolution which gives rise to a ratio of 0 5 cannot provide all the hco 3 to solution hence carbonate hydrolysis may be occurring before sulphide oxidation or there may be subglacial sources of co2 perhaps arising from microbial oxidation of organic c in bedrock air bubbles in glacier ice or pockets of air trapped in subglacial cavities the channel marginal zone is identified as an area that may influence the composition of bulk meltwater during periods of recession flow and low diurnal discharge regimes 1997 by john wiley sons ltd

chemical weathering in the foreland of a retreating glacier chemical denudation rates and strontium isotope ratios in streams vary substantially and systematically in the foreland of the retreating bench glacier in south central alaska to study weathering of young glacier sediments we sampled 12 streams draining a chronosequence of till and moraine soils derived from cretaceous metagraywacke metapelite bedrock both sediment age and vegetation cover increase with distance from the glacier cation denudation rates decline with increasing distance from the glacier whereas silica denudation rates increase carbonate dissolution and sulfide oxidation account for roughly 90 of the solute flux from the youngest sediments biotite alteration accounts for 5 11 of the solute flux its peak contribution is found in the glacier outlet stream silicate weathering is the dominant reaction only in the oldest sediments in a laboratory dissolution experiment using fresh glacial sediment carbonate dissolution dominated the solute flux during the first 700 hours paralleling the behavior of young sediments in the field in contrast to trends in the field the silica flux did not increase after the carbonate was exhausted from the reactor a possible reason for this difference is that establishment of vegetation causes an increase in silicate weathering the 87sr 86sr ratio in the glacier outlet stream is greater than that in proglacial streams and in bulk rock due to a greater contribution of biotite weathering in the outlet than in proglacial streams strontium isotope ratios decline with sediment exposure age in the proglacial streams and are consistent with a carbonate source because the dominant weathering reactions in the young sediments are of carbonate and sulfide rather than silicate minerals weathering at the glacier margin is not an important long term sink for atmospheric co2

iron and manganese speciation and cycling in glacially influenced high latitude fjord sediments west spitsbergen svalbard evidence for a benthic recycling transport mechanism abstract glacial environments may provide an important but poorly constrained source of potentially bioavailable iron and manganese phases to the coastal ocean in high latitude regions little is known about the fate and biogeochemical cycling of glacially derived iron and manganese in the coastal marine realm sediment and porewater samples were collected along transects from the fjord mouths to the tidewater glaciers at the fjord heads in smeerenburgfjorden kongsfjorden and van keulenfjorden along western svalbard solid phase iron and manganese speciation determined by sequential chemical extraction could be linked to the compositions of the local bedrock and hydrological weathering conditions below the local glaciers the concentration and sulfur isotope composition of chromium reducible sulfur crs in kongs and van keulenfjorden sediments largely reflect the delivery rate and isotope composition of detrital pyrite originating from adjacent glaciers the varying input of reducible iron and manganese oxide phases and the input of organic matter of varying reactivity control the pathways of organic carbon mineralization in the sediments of the three fjords high reducible iron and manganese oxide concentrations and elevated metal accumulation rates coupled to low input of fresh organic matter lead to a strong expression of dissimilatory metal oxide reduction evidenced in very high porewater iron up to 800 m and manganese up to 210 m concentrations in kongsfjorden and van keulenfjorden sediment reworking by the benthic macrofauna and physical sediment resuspension via iceberg calving may be additional factors that promote extensive benthic iron and manganese cycling in these fjords on going benthic recycling of glacially derived dissolved iron into overlying seawater where partial re oxidation and deposition occurs facilitates the transport of iron across the fjords and potentially into adjacent continental shelf waters such iron dominated fjord sediments are likely to provide significant fluxes of potentially bioavailable iron to coastal waters and beyond by contrast low delivery of reducible iron oxyhydr oxide phases and elevated organic carbon mineralization rates driven by elevated input of fresh marine organic matter allow organoclastic sulfate reduction to dominate carbon remineralization at the outer smeerenburgfjorden sites which may limit iron fluxes to the water column

the rate of chemical weathering beneath a quiescent surge type polythermal based glacier southern spitsbergen svalbard glacierized basins in the high arctic are believed to be regions of low chemical weathering rates despite the lack of pertinent data because it is believed that water does not flow in significant quantities through subglacial drainage systems we have calculated chemical weathering rates at finsterwalderbreen a polythermal surge type glacier in svalbard rates of 320 and 150 meq m 1 year 1 were measured in 1994 and 1995 respectively the corresponding water fluxes were 4 1 10 7 and 1 7 10 7 m 3 we estimate that we have measured 72 of the total annual discharge hence the true annual chemical weathering rates are 440 and 210 meq m 2 year 1 respectively this gives a mean annual chemical weathering rate of 330 meq m 2 year 1 which approximates the continental average of 390 meq m 2 year 1 and is intermediate between chemical weathering rates measured on cold based glaciers 110 160 meq m 2 year 1 and temperate glaciers 450 1000 meq m 2 year 1 this suggests that there may be a direct link between chemical weathering rates and thermal regime and that glacierized basins in the high arctic cannot necessarily be considered as regions of low chemical weathering and co 2 drawdown

hydrologic exchange and chemical weathering in a proglacial watershed near kangerlussuaq west greenland abstract the exchange of proglacial river water with active layer pore water could alter water chemical compositions in glacial outwash plains and oceanic solute fluxes to evaluate effects of this exchange we sampled watson river and adjacent pore water during the 2013 melt season at two sandurs in western greenland one in sandflugtdalen and the other near the confluence with sondre stromfjord we measured temperature specific conductivity and head gradients between the river and bank over a week long period at sandflugtdalen as well as sediment hydraulic conductivity and chemical compositions of waters from both sites specific conductivity of pore water is four to ten times greater than river water as solutes are concentrated from weathering reactions cryoconcentration and evaporation pore water compositions are predominantly altered by carbonate dissolution and sulfide mineral oxidation high concentrations of hco3 and so4 result from solute recycling and dissolution of secondary ca mg carbonate sulfate salts initially formed by near surface evaporation in the summer and at depth by freeze in of the active layer and cryoconcentration in the winter high hydraulic conductivity 10 5 to 10 4 m s and diurnal fluctuations of river stage during our study caused exchange of river and pore water immediately adjacent to the river channel with a net loss of river water to the bank pore water 6 m from the river continuously flowed away from the river approximately 1 8 of the river discharge through the sandflugtdalen was lost to the river bank during our 6 75 day study based on calculations using darcy s law although not sampled some of this water should discharge to the river during low river stage early and late in the melt season elevated pore water solute concentrations in sandurs and water exchange at diurnal and seasonal frequency should impact fluxes of solutes to the ocean although understanding the magnitude of this effect will require long term evaluation throughout the melt season

chemical weathering in glacial environments do glaciers enhance or inhibit chemical weathering rates relative to other environments the importance of glaciers in the global carbon cycle and climate change hinges on the answer we show that catchments occupied by active alpine glaciers yield cation denudation rates greater than the global mean rate but do not exceed rates in nonglacial catchments with similar water discharge silica denudation rates are distinctly lower in glacier covered catchments than in their nonglacial counterparts because sediment yields are high from glaciers this suggests that water flux rather than physical erosion exerts the primary control on chemical erosion by glaciers potassium and calcium concentrations are high relative to other cations in glacial water probably due to dissolution of soluble trace phases such as carbonates exposed by comminution and cation leaching from biotite preferential weathering of biotite may result in higher 87 sr 86 sr in glacial runoff than expected from whole rock compositions thus although glaciers do not influence total chemical denudation rates at a given runoff they may yield compositionally distinctive chemical fluxes to the oceans disruption of mineral lattices by grinding increases dissolution rates this and high surface area should make glacial sediments exceptionally weatherable weathering of glacial erosion products in environments beyond the glacier margin deserves attention because it may figure prominently in global chemical cycles

hydrochemistry of meltwaters draining a polythermal based high arctic glacier south svalbard ii winter and early spring the hydrochemistry of naled and upwelling water sampled from the forefields of finsterwalderbreen svalbard during spring are used for the first time to infer the hydrology of overwinter meltwaters at a polythermal based glacier hydrochemical variations in naled are explained in terms of different water sources and their chemical alteration during freezing two water sources to naled are identified surficially routed snowmelt and subglacial water naled that results from the freezing of the former is enriched in atmospherically derived ions such as na and cl and is believed to be formed during winter warm periods naled of subglacial origin contains relatively high proportions of crustally derived solute it reflects the freezing of subglacial meltwaters that continue to issue from a subterranean upwellling during winter an increasing dominance of so2 4 mg2 na and cl in subglacial naled with increasing distance from the upwelling reflects the progressive freezing of this water body and the associated removal of ca2 and hco by calcite precipitation these spatial trends are accentuated by the leaching of soluble ions from the naled close to its source by subsequent upwelling waters the chemistry of spring upwelling waters also of subglacial origin strongly reflects this process meltwater produced by geothermal heating of glacier basal ice is believed to be the principal source of water to the subglacial drainage system during winter solute acquisition by this meltwater is limited by a scarcity of proton suppliers evolution of this dilute meltwater carries an imprint of ion exchange processes some stored subglacial water from the end of the previous ablation season may supplement the basal meltwater component in early winter copyright 2000 john wiley sons ltd

hydrogeological implications of glacial landscape evolution at skeiðararsandur se iceland abstract patterns of groundwater recharge and flow in present day and palaeo glacial environments are governed by both geomorphology and subsurface sedimentology this paper assesses the hydrogeological implications of glacial landscape evolution and develops a conceptual model of glacial landscape evolution and hydrogeological interaction the ice marginal zone of skei ararsandur se iceland was selected as a case study of a temperate actively receding glacier landsystem that is affected by both surging behaviour and periodic glacier outburst floods jokulhlaups the groundwater table elevation was measured approximately every 2 5 days throughout two six week summer field seasons in 2000 and 2001 and once in march 2001 using a network of shallow piezometers and hydraulic conductivity was calculated based on grain size distribution analysis of sampled aquifer materials the hydraulic conductivity of the near surface aquifer at the study site spans three orders of magnitude and is highest and most varied in areas inundated by the november 1996 jokulhlaup the shallow water table in the study area responds dynamically to precipitation events with the greatest fluctuation in an enclosed moraine lake basin with a perched aquifer underlain by ice and in a zone of outwash fans proximal to the ice margin the seasonal decline in water table is greatest at the ice margin reflecting the reduced winter recharge from the stagnant ice zone landsystems with morainic relief are associated with localised moraine precipitation fed groundwater systems these localised groundwater systems are superimposed on the intermediate regional scale groundwater systems that discharge further down sandur and offshore and are dominated by the gently sloping geomorphologically uniform outwash plain groundwater fed lakes formed in depressions from ice blocks deposited during jokulhlaups may provide important ecological niches the investigations at this site demonstrate that glacial outburst floods and glacier margin fluctuations produce a suite of sediments landforms and environments that affect the hydrogeological system

rates of chemical denudation and co2 drawdown in a glacier covered alpine catchment solute fluxes from a glacier covered alpine catchment are partitioned into components derived from sea salt acid aerosol dissolution of atmospheric co2 and crustal weathering the bulk of solute is crustally derived coupled sulfide oxidation and carbonate dissolution so cd and carbonation of carbonate minerals generate approximately equal amounts of solute chemical denudation constitutes 1 5 of solid denudation but is significantly higher than the continental average co2 drawdown by weathering reactions varies directly with discharge and suspended sediment load and inversely with meltwater p co2 if it is generally true that flushing rates control co2 drawdown in glacier covered catchments then glacially driven chemical weathering could be a significant factor in carbon cycling and climate change on glacial interglacial time scales