wintertime winds and coastal sea level fluctuations in the northeast china sea part ii numerical model abstract as a sequel to data analysis reported in part i a numerical model of the wintertime wind driven circulation of the northeast chine sea is developed with the primary purpose of achieving an understanding of the underlying dynamics to several observed features of the coastal sea level behavior the model is linear and pertains to the vertically integrated balance of momentum and mass in a well mixed shallow ocean the model bathymetry incorporates a realistic shelf embayment and an open ocean region of a depth so limited that observed sea level differences across open boundaries in the deep western pacific do not result in unreasonably large model transports from results of model runs for the 1980 81 winter it is found that 1 along the west coast of south korea sea level setup to the south is a consequence chiefly of the presence at the end of the korean peninsula of relatively deep offshore water that is less responsive to wind forcing than the shallow shelf water 2 pressure gradient forc

recent current observations in the eastern yellow sea observations of current velocity pressure and temperature in the eastern yellow sea from january 10 through april 12 1986 together with geostrophic winds calculated from surface atmospheric pressure distributions are analyzed for a study of the synoptic band response of the yellow sea to the wintertime winds north wind pulses in the winter monsoon are found to give rise to northward flow bursts in the yellow sea trough which appear to peak just as the wind relaxes and to be driven by a synoptic band north to south rise in bottom pressure synchronous with the north wind pulses the existence of a similar rise in coastal sea level indicates that the observed southward pressure rise is but an offshore extension of a setup along the west coast of south korea forced by the north wind pulses the advection by northward flow bursts of warm water from the south apparently causes the measured temperature to be substantially higher in the trough than in coastal waters at the same latitude and the observed rate of cooling in the trough to be less than half of that in coastal waters to the east a winter to spring transition is also found in the bottom pressure records obtained in the trough in which the mean north to south gradient in winter reverses suddenly in early march a similar reversal also appears in sea level records along the west coast of south korea the reversal appears to be triggered by the weakening of the north winds at the arrival of spring

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

an asymmetric upwind flow yellow sea warm current 2 arrested topographic waves in response to the northwesterly wind 1 a warm and salty water mass exists along the yellow sea trough yst in winter this oceanic water mass is distinct from the ambient shelf water and is distributed on the western side of the yst it has long been reasoned that a yellow sea warm current yswc must exist a recent observational study indeed supports the existence of the yswc and shows that its position moved progressively westward as the warm water intrudes further shoreward toward the northwest in this paper we explain mechanisms for sustaining the yswc and for its westward displacement the northwesterly monsoonal wind prevails in the winter and is directed against the yswc the cross trough scale is small compared with the spatial scale of monsoonal variation so one can assume to the first order that the wind stress is uniform across the trough the curl of depth averaged wind stress has opposite signs on the two sides of the trough consequently two oppositely rotating gyres develop initially and they converge along the trough giving rise to a barotropic upwind flow but this upwind flow lasts only for a few days as the two gyres evolve and propagate as topographic waves for a northerly wind both gyres move westward since the positive negative potential vorticity flux on the western eastern side of the trough pushes the water toward shore trough if the bottom friction is negligible the steady response becomes a large anticyclonic gyre over the trough and the upwind current is squeezed toward the shore line in this case no yswc is sustained along or near the trough this runaway warm current can be arrested by a moderate bottom friction we therefore propose that the yswc is actually arrested topographic waves in response to local wind stress forcing

implications for post comminution processes in subglacial suspended sediment using coupled radiogenic strontium and neodymium isotopes abstract enhanced physical weathering rates in subglacial systems promote high levels of comminution transport and deposition of fine grained sediment within the subglacial drainage network the impact of shifts in sediment loads from variations in meltwater flux and their effects on downstream ecosystems remains poorly quantified and places a fundamental importance on our ability to characterize subglacial depositional environments here for the first time we assess the seasonal evolution of the subglacial suspended sediment using coupled radiogenic strontium 87 sr 86 sr and neodymium 143 nd 144 nd isotopic ratios with elemental ratios and in situ measurements weathering rates in fluvial and riverine systems have been traditionally assessed using radiogenic isotopic tracers 143 nd 144 nd ratios relate to the crustal age whereas 87 sr 86 sr ratios relate to age and preferential mineral dissolution thus relative shifts in these ratios will allow us to characterize distinct sediment transport networks we apply this technique to the lemon creek glacier lcg alaska usa and to the athabasca glacier ag alberta ca at the lcg the 143 nd 144 nd values range from e nd of 4 6 0 9 to 8 7 0 2 which suggests a poorly mixed sediment flux however the greatest period of variability may correlate with the drainage of a supraglacial lake and suggests caution should be exerted in time scale 143 nd 144 nd provenance studies that may be affected by climatic disturbances in contrast limited variation is observed within the ag 143 nd 144 nd seasonal record a consistent direct relation between the rb sr elemental ratio and the 87 sr 86 sr ratio proves interesting as it enables us to unravel incongruent weathering trends in the radiogenic sr record correlation between the 87 sr 86 sr and total discharge suggests that the process is partially controlled by mantling of the bedrock which can be detected using post comminution ages while the subglacial structure may be enabled by the subglacial till beneath the ag our study supports the use of sr nd as a new proxy in the subglacial environment

study of the dynamics of wind driven transports into the yellow sea during winter synoptic wind stresses and surface heat flux force a three dimensional numerical ocean model of the yellow sea east china sea dynamics the basin response to winter winds is examined through the model output fields northerly wind bursts are a frequent winter occurrence in this region the wind bursts develop a southward flowing current along the chinese coast as the wind stress forces fluid out of the bohai sea a north south pressure gradient develops as surface water travels from the bohai sea southward decreasing the elevation in the north relative to the elevation in the south also a westward pressure gradient across the yellow sea basin develops in response to the wind forcing the southward pressure gradient forces a bottom flow in the direction opposite to the wind stress this return flow is concentrated in a deep trough located on the eastern side of the basin after the northerly wind ceases the northward transport increases pressure in the north with the result of slowing or stopping the flow northward at times pressure increases in the north sufficiently to force a southward flow in the trough following strong northerly wind events northward transport into the yellow sea occupies the entire trough and may extend into the northern yellow sea bohai sea during periods of calm winds northward flow usually does not penetrate beyond 34 n in the yellow sea this flow is northward on the western side of the island of cheju the flow turns eastward north of cheju and then southward passing through the cheju korea strait the wind stress along the korean coast often deviates from the northerly wind stress over the rest of the yellow sea thus the flow along the korean coast is not as closely related to the northerly wind bursts as the flow along the chinese coast the winter circulation in the yellow sea is predominately a barotropic response to winds with fluctuations due to ekman flow

determination of 88sr 86sr mass dependent isotopic fractionation and radiogenic isotope variation of 87sr 86sr in the neoproterozoic doushantuo formation abstract we measured both mass dependent isotope fractionation of 88sr 88sr 86sr and radiogenic isotopic variation of sr 87sr 86sr for the neoproterozoic doushantuo formation that deposited as a cap carbonate immediately above the marinoan related nantuo tillite the 88sr and 87sr 86sr compositions showed three remarkable characteristics 1 high radiogenic 87sr 86sr values and gradual decrease in the 87sr 86sr ratios 2 anomalously low 88sr values at the lower part cap carbonate and 3 a clear correlation between 87sr 86sr and 88sr values these isotopic signatures can be explained by assuming an extreme greenhouse condition after the marinoan glaciation surface seawater mixed with a large amount of freshwater from continental crusts with high 87sr 86sr and lighter 88sr ratios was formed during the extreme global warming after the glacial event high atmospheric co2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87sr 86sr and lighter 88sr ratios subsequently the mixing of the underlying seawater with unradiogenic sr isotope compositions and normal 88sr ratios probably caused gradual decrease of the 87sr 86sr ratios of the seawater and deposition of carbonate with normal 88sr ratios the combination of 87sr 86sr and 88sr isotope systematics gives us new insights on the surface evolution after the snowball earth

glacial effects on weathering processes new insights from the elemental and lithium isotopic composition of west greenland rivers greenland is by far the dominant source of glacial runoff to the oceans but the controls on the chemical and isotopic composition of this runoff are poorly known to better constrain glacial effects on weathering processes we have conducted elemental and lithium isotope analyses of glacial and non glacial rivers in gneiss catchments in west greenland the glacial rivers have high total suspended solids 0 5 g l 1 and low total dissolved solids 12 scm 1 relative to the non glacial rivers and they contain a higher proportion of dissolved ca2 and k because of subglacial preferential weathering of trace carbonates and biotite the glacial rivers also have high so42 because of the oxidation of trace sulphides under the ice both glacial and non glacial rivers have high 7li respectively not vert similar 26 and not vert similar 30 relative to the rocks from which the li is derived not vert similar 8 saturation state modelling suggests that this is due to the formation of fe oxyhydroxides in the non glacial rivers with preferential uptake of 6li during inner sphere sorption of li on the fe oxyhydroxide surface glacial rivers however are undersaturated with respect to clay minerals and fe oxyhydroxides nevertheless leaching of suspended sediments indicates that not vert similar 65 of the li in these sediments is associated with fe oxyhydroxide phases and the 7li value of this li is low not vert similar 5 these results suggest that these fe oxyhydroxides formed under the ice as a product of sulphide oxidation with preferential uptake of 6li onto the mineral surface solubilisation of li from these fe oxyhydroxide phases is unlikely to represent a significant flux of li to the oceans moreover because the difference between the 7li values of glacial vs non glacial rivers is small glaciation has not had a significant impact on the li isotopic composition of the riverine flux delivered to the oceans in the past even at the height of the last deglaciation

evidence for stable sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern taiwan abstract radiogenic sr isotopes 87 sr 86 sr are robust for provenance identification in hydrology affected mainly by the age of background lithologies and the degree of chemical weathering however there is limited knowledge concerning the fractionation mechanism of stable sr isotopes 88 sr 86 sr in rivers in this study river water was collected on a weekly to monthly basis throughout dry and wet seasons furthermore to study the variations of radiogenic and stable sr isotopes during intense weathering a major flooding event 2000 mm precipitation in three days typhoon morakot water was captured within a small drainage catchment system 161 km 2 along the hou ku river in southwestern taiwan for a better constraint on the end member compositions bedload sediments suspended particles and several host rocks were sampled for a systematic investigation the carbonate and silicate phases of these solids were chemically separated dissolved major elements indicate that the watersheds were predominated by silicate weathering stable sr isotopes show no significant variation 88 sr 0 24 0 31 temporally and spatially with an average of 0 28 additionally all solids showed lower 88 sr values than the river water while the host rocks had higher 88 sr values 88 sr 0 20 0 26 than the residual weathering products 88 sr 0 08 0 22 indicating preferential leaching of heavy sr into the hydrosphere and leaving light sr in the residual solids results of laboratory acid leaching experiments reveal that dissolution of high 88 sr value minerals occurred at an early stage of weathering the variation of weathering intensity does not alter stable sr isotopes in silicate weathering dominated river water which contains higher stable sr isotopes than the associated sediments the silicatic sedimentary rocks preferentially released higher stable sr isotopes into the hydrosphere during chemical weathering thus leaving lower stable sr isotopes in the residual solids

calcium isotope fractionation in modern scleractinian corals the 44ca 40ca ratios of cultured acropora sp and open ocean pavona clavus porites sp tropical reef corals are positively correlated with growth temperature the slope of the temperature fractionation relation is similar to inorganic aragonite precipitates however 44 40ca of the coral aragonite is offset from inorganic and sclerosponge aragonite by about 0 5 this offset can neither be explained by the very fast biologically controlled calcification of scleractinian corals nor as a consequence of calcification from a partly closed volume of fluid as corals actively transport calcium through several cell layers to the site of calcification the most likely explanation for the offset is a biologically induced fractionation our results indicate a limited use of ca isotopes in scleractinian corals as temperature proxy

climate versus geological controls on glacial meltwater micronutrient production in southern greenland abstract low concentrations of micronutrients in subarctic north atlantic surface waters limit phytoplankton growth iron phosphorous and silicon are all potentially bio limiting nutrients iron is the most well documented in the subarctic north atlantic manganese nickel copper and zinc are also essential trace metals for phytoplankton cell function however the spatial and temporal variability in the flux of these elements to the subarctic north atlantic is undercharacterized here we show new data from the meltseason peak in 2013 indicating that glacial meltwater from the southern tip of greenland has elevated dissolved major and trace metal concentrations compared to glacial meltwater draining shorter melt season glacial catchments to the north fe concentrations range from 0 13 to 6 97 m zn from 4 to 95 m and si from 4 to 36 m all higher than the depleted surface waters of the subarctic north atlantic measured hydrochemical data modeled by phreeqc indicates meltwater is undersaturated in pyrite and silicate phases but supersaturated with respect to oxyhydroxides hematite and goethite all phases that precipitate fe as colloids of which the nanoparticle phases should remain biologically available the variability in geologic units between the sites indicates that subglacial lithology is a minor but not the dominant control on meltwater chemistry the disparity in concentrations is directly correlated with climate and an extended melt season suggesting that future warming in greenland will lead to increased trace element and potential micronutrient flux to the subarctic north atlantic surface waters

a numerical study of currents heat advection and sea level fluctuations in the yellow sea in winter 1986 abstract a vertically integrated model that incorporates horizontal temperature variations is used to study the circulation of the yellow sea in a wintertime period for which velocity and temperature measurements are available at several moorings locations along a central trough the model features realistic bottom topography and is forced with wind stress and heat flux fields from 13 january to 22 february 1986 the model also incorporates as a boundary condition sea level fluctuations derived from coastal and insular tide gauge stations along model boundaries in open waters the model reproduces well sea level fluctuations along the coasts of both china and korea the hindcast velocity time series particularly for the north south component track those obtained from direct measurements at the moorings the model momentum balance indicates that the northward flow in the trough is driven by a sea level setup to the south in response to northerly wind bursts in the winter monsoon the sea level fluctuat

strontium isotope composition of runoff from a glaciated carbonate terrain abstract the relationship between subglacial chemical weathering processes and the sr isotope composition of runoff from robertson glacier alberta canada is investigated this glacier rests on predominantly carbonate bedrock of upper devonian age but silicate minerals are also present the provenance of solute in meltwaters is found to vary systematically with solute concentration and by inference subglacial water residence time in dilute waters the principal process of solute acquisition is calcite dissolution fueled by protons derived from the dissolution of co 2 and subsequent dissociation of carbonic acid at higher solute concentrations dolomite dissolution coupled to sulfide oxidation is more important sr concentration is found to increase with total solute concentration in two separate meltwater streams draining from the glacier but 87 sr 86 sr only increases in the eastern melt stream carbonate and k feldspar sources are shown to dominate the sr content of the western stream irrespective of concentration they also dominate the sr content of the eastern stream at low and intermediate concentrations but at higher concentrations muscovite with high 87 sr 86 sr is also an important sr source this reflects the outcrop of muscovite bearing lithologies in the catchment of the eastern stream and an increase in the rate of weathering of k silicates relative to that of carbonates as more concentrated solutions approach saturation with respect to carbonates nonstoichiometric release of 87 sr 86 sr and preferential release of sr over k from freshly ground k silicate surfaces may also occur this may help to explain the radiogenic nature of runoff from distributed subglacial drainage systems which are characterized by long water rock contact times and water flow through environments in which crushing and grinding of bedrock are active processes although the exchangeable sr in tills has higher 87 sr 86 sr than local carbonate bedrock only the more concentrated meltwaters from the eastern stream display similarly high values the most dilute waters which probably transport the bulk of the dissolved sr flux from the glacier have 87 sr 86 sr characteristic of local carbonate bedrock thus the results suggest that although enhanced weathering of silicate minerals containing radiogenic sr such as muscovite does occur in glaciated carbonate terrains it is unlikely to contribute to any enhanced flux of radiogenic sr from glaciated continental surfaces to the oceans

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

northern latitude chemical weathering rates clues from the mackenzie river basin canada abstract the main scope of this study is to investigate parameters controlling chemical weathering rates for a large river system submitted to subarctic climate more than 110 river water samples from the mackenzie river system northern canada have been sampled and analyzed for major and trace elements and sr isotopic ratios in the dissolved phase the three main morphological units are reflected in water chemistry rivers from the canadian shield are very dilute dominated by silicate weathering millot et al 2002 whereas the rivers of the rocky and mackenzie mountains as well as the rivers of the sedimentary interior platform are dominated by carbonate weathering and are so 4 rich compared to the rivers of the mackenzie and rocky mountains the rivers of the interior plains are organic silica and na rich and constitute the dominant input term to the mackenzie river mainstream rivers of the canadian shield area do not significantly contribute to the mackenzie river system using elemental ratios and sr isotopic ratios a mathematical inversion procedure is presented that distinguishes between solutes derived from silicate weathering and solutes derived from carbonate weathering carbonate weathering rates are mostly controlled by runoff which is higher in the mountainous part of the mackenzie basin these rates are comparable to the carbonate weathering rates of warmer areas of the world it is possible that part of the carbonate weathering is controlled by sulfide oxidative weathering but its extent remains difficult to assess conversely to what was stated by edmond and huh 1997 overall silicate weathering rates in the mackenzie basin are low ranging from 0 13 to 4 3 tons km 2 yr na k ca mg and confirm the negative action of temperature on silicate weathering rates for river basins in cold climates in contrast to what has been observed in other large river systems such as the amazon and ganges rivers silicate weathering rates appear 3 to 4 times more elevated in the plains than in the mountainous headwaters this contradicts the raymo hypothesis raymo and ruddiman 1992 isotopic characterization of suspended material clearly shows that the higher weathering rates reported for the plains are not due to the weathering of fine sediments produced in the mountains e g by glaciers and deposited in the plains rather the relatively high chemical denudation rates in the plains are attributed to lithology uncompacted shales high mechanical denudation and the abundance of soil organic matter derived from incomplete degradation and promoting crystal lattice degradation by element complexation the three to fourfold factor of chemical weathering enhancement between the plains and mountains is similar to the fourfold factor of enhancement found by moulton et al 2000 between unvegetated and vegetated watershed this study confirms the negative action of temperature on silicate weathering for cold climate but shows that additional factors such as organic matter associated with northern watersheds are able to counteract the effect of temperature this acceleration by a factor of 4 in the plains is equivalent to a 6 c increase in temperature

the behaviour of magnesium and its isotopes during glacial weathering in an ancient shield terrain in west greenland the magnesium mg isotope composition of rivers is sensitive to changes in the balance of primary mineral dissolution and secondary mineral formation as these processes are regulated by climate then changes to the earth s climate system such as the onset of glaciation could potentially alter the isotopic behaviour of mg in rivers to investigate how mg isotopes behave during glacial weathering we have determined the mg concentration and mg isotope ratio for the dissolved suspended and bedload phases of glacial and non glacial rivers in west greenland this region is essentially monolithological and there is little biological activity hence isotope variations largely result from differences in weathering processes dissolved mg in rivers is always enriched in the light mg isotopes relative to the bedload 26mg 0 4 and the glacial rivers have lighter mg isotope compositions 26mg 1 to 1 3 than the non glacial rivers 26mg 0 6 enrichment of light mg in the dissolved load is consistent with the preferential uptake of heavy mg from solution during the formation of secondary silicate minerals however evidence from saturation state modelling suggests that little secondary mineral formation is likely to have occurred in the glacial rivers because the concentration of dissolved solids is very low moreover the glacial derived suspended sediment has identical mg isotope ratios to the bedload these observations suggest that the formation of secondary weathering minerals is not controlling the behaviour of mg isotopes in these rivers rather variations in the 26mg value of the dissolved load are attributed to incongruent weathering of the solid phase preferential dissolution of carbonate minerals which have low 26mg 1 1 to 5 2 imparts a more negative 26mg signal to the glacial river waters although our study indicates that the mg isotopic composition of the dissolved load is sensitive to changes in weathering congruence it is unlikely that glaciation will result in major changes in the 26mg composition of continental runoff

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

sr stable isotope composition of earth the moon mars vesta and meteorites abstract high precision stable sr isotopic variations 88 sr 86 sr are reported in a variety of terrestrial samples martian and lunar meteorites hed undifferentiated primitive meteorites chondrules and refractory inclusions almost all the whole rock samples are isotopically indistinguishable at a 50 parts per million ppm level the exceptions are cv and co chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material five separated chondrules and one refractory inclusion from allende are isotopically light with 88 86 sr fractionations up to 1 73 whereas the matrix is enriched in the heavy isotopes 88 86 sr 0 66 the depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in sr however in that case more than 60 of the original material would be unaccounted we propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy sr from neutral sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix we conclude that cv and co chondrites are not the primary building blocks for earth and mars

high precision radiogenic strontium isotope measurements of the modern and glacial ocean limits on glacial interglacial variations in continental weathering existing strontium radiogenic isotope 87sr 86sr measurements for foraminifera over quaternary glacial interglacial climate cycles provide no evidence for variations in the isotope composition of seawater at the 9 13 ppm level of precision however modelling suggests that even within this level of uncertainty significant up to 30 variations in chemical weathering of the continents are permitted accounting for the longer term rise in 87sr 86sr over the quaternary and the apparent imbalance of sr in the oceans at the present day this study presents very high precision 87sr 86sr isotope data for modern seawater from each of the major oceans and a glacial interglacial seawater record preserved by planktic foraminifera from ocean drilling program odp site 758 in the north east indian ocean strontium isotope 87sr 86sr measurements for modern seawater from the atlantic pacific and indian oceans are indistinguishable from one another 87sr 86sr 0 7091792 0 0000021 n 17 at the level of precision obtained in this study 4 9 ppm 2 this observation is consistent with the very long residence time of sr in seawater and underpins the utility of this element for high precision isotope stratigraphy the 87sr 86sr seawater record preserved by planktic foraminifera shows no resolvable glacial interglacial variation 87sr 86sr 0 7091784 0 0000035 n 10 and limits the response of seawater to variations in the chemical weathering flux and or composition to 4 9 ppm or less calculations suggest that a variation of 12 around the steady state weathering flux can be accommodated by the uncertainties obtained here the new data cannot accommodate a short term weathering pulse during de glaciation although a more a diffuse weathering pulse accompanying protracted ice retreat is permissible however these results still indicate that modern weathering fluxes are potentially higher than average over the quaternary and such variations through glacial cycles can also account for the longer term rise in 87sr 86sr over this time interval the very high precision measurements made for the marine 87sr 86sr record in this study place clear limits on the magnitude and timing of changes in the chemical weathering flux during glacial interglacial cycles further constraints must be sought from even higher precision measurement or elements with shorter residence times in the ocean such as osmium os that have the capacity to respond to short term variations in input

strontium isotope variation and carbonate versus silicate weathering in rivers from across alaska implications for provenance studies abstract the characterization of strontium sr isotopic 87 sr 86 sr variation in surface waters of alaska ak has significant implications for provenance studies aiming to track movement patterns of animals this study presents 87 sr 86 sr ratios concentrations of sr ca mg na and k and selected molar ratios sr na ca na mg na and ca sr from 61 rivers from across ak to characterize regional patterns in i 87 sr 86 sr variation and ii carbonate versus silicate weathering influencing 87 sr 86 sr ratios 87 sr 86 sr ratios range from 0 70422 0 74041 0 00009 rivers north of the denali fault exhibit more radiogenic and variable 87 sr 86 sr ratios 0 70763 to 0 74041 than rivers to the south 0 70422 to 0 70895 reflecting the tectonic growth of southern ak via accretion of relatively young mafic rich exotic island arcs along north america s continental margin during the mesozoic within interior ak an east west gradient exists radiogenic 87 sr 86 sr ratios 0 725 in east central ak and relatively low ratios 0 711 than lowland rivers 87 sr 86 sr ratios in high relief watersheds north of the denali fault and in watersheds of south central ak elemental and 87 sr 86 sr ratios indicate silicate weathering is important across ak but is most influential in lowland basins north of the denali fault and in southwestern ak this study illustrates the large sr isotopic heterogeneity across ak on multiple spatial scales and provides necessary baseline information for provenance studies

controls on the solute geochemistry of subglacial discharge from the russell glacier greenland ice sheet determined by radiogenic and stable sr isotope ratios abstract we used radiogenic and stable sr isotope ratios 87sr 86sr and 88 86sr to examine controls on solute acquisition in subglacial discharge from the russell glacier a land terminating lobe of the greenland ice sheet gris located in western greenland the study focused on two melt seasons in 2014 and 2015 subglacial discharge 87sr 86sr ratios are 13 000 ppm higher than those measured for bedload and suspended sediment digests and are more similar to those of bedload sediment leachates these results point to the preferential dissolution of minerals with high 87sr 86sr ratios analyses of mineral separates from bulk rocks demonstrate that biotite chlorite hornblende and k feldspar have relatively high 87sr 86sr ratios subglacial discharge 88 86sr values are 0 10 higher than those for bedload and suspended sediment digests isotope fractionation during secondary mineral formation and or adsorption cannot account for the difference between subglacial discharge and bedrock 88 86sr values as suspended and bedload sediment leachates and digests produced similar 88 86sr values and are within the range for bulk silicate earth consistent with the interpretation of 87sr 86sr ratios we attribute the difference to the preferential dissolution of minerals with high 88 86sr values mineral separates display a wide range of 88 86sr values 0 40 those having high 88 86sr values include hornblende and k feldspar as well as apatite and titanite taken together the preferential weathering of predominately silicate minerals explains the sr isotope geochemistry of subglacial discharge subglacial discharge from the russell glacier feeds the proglacial akuliarusiarsuup kuua river akr along a 32 km transect of the akr from the gris margin toward the coast riverine 87sr 86sr ratios increase from 0 722 to 0 747 in an approximately step wise pattern that corresponds to point source inputs of additional subglacial discharge major cation concentrations and 87sr 86sr ratios minimally vary along lengths of the transect with no hydrological inputs this suggests that proglacial chemical weathering is negligible and likely does not contribute significantly to gris solute fluxes in general this study supports the recent contention that silicate mineral weathering dominates the solute geochemistry of gris subglacial discharge in contrast to valley glaciers which typically show substantial contributions from carbonate and sulfide weathering regardless of primary bedrock composition ice sheet subglacial chemical weathering may therefore have a greater impact on long term atmospheric co2 drawdown than previously realized

numerical investigation of the generation of continental shelf waves and their role in the westward shift of the yellow sea warm current abstract the yellow sea warm current yswc which carries warm saline water into the yellow sea ys exhibits a typical northward upwind flow during winter observations have shown that the path of the yswc has shifted to the west from the deep trough and it has been suggested that continental shelf waves csws may play an important role in this westward shift however the source of southward propagating csws that drive the westward shift of the yswc remains unclear the objective of this study is to reveal the generative mechanism of csws and their role in driving the westward shift of the yswc numerical models with an idealised topography show that the westward shift of the northward flow propagates southward along the western slope offshore of china with a typical speed of 2 99 m s 1 comparable to the theoretical phase speed of a first mode csw csws driving the westward shift are generated on the northern slope primarily by the scattering of kelvin waves that develop due to northerly winds and propagate northward into the ys along the eastern boundary of the korean peninsula model experiments with a realistic topography consistently support the idea that kelvin wave scattering is a primary source of the southward propagation of the csws that drive the westward shift of the yswc

calcium isotopes in a proglacial weathering environment damma glacier switzerland the biogeochemical cycling and isotopic fractionation of calcium during the initial stages of weathering were investigated in an alpine soil chronosequence damma glacier switzerland this site has a homogeneous silicate lithology and minimal biological impacts due to sparse vegetation cover calcium isotopic compositions obtained by tims using a 43ca 46ca double spike were measured in the main ca pools during this very early stage of weathering the young soils which have formed 44 42ca 0 44 44 42ca 0 44 were indistinguishable to the rocks from which they were derived 44 42ca 0 44 44 42ca 0 44 and stream water 44 42ca 0 48 44 42ca 0 48 was also within error of the average rock this lack of variation indicates that the dissolution of the bulk silicate rock does not strongly fractionate ca isotopes the only ca pool which was strongly fractionated from bulk rock was vegetation which exhibited an enrichment of light ca isotopes significant ca isotope fractionation between bulk rock and the dissolved flux of ca is likely to only occur where the ca biogeochemical cycle is dominated by secondary processes such as biological cycling adsorption and secondary mineral precipitation

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

behaviour of lithium and its isotopes during weathering in the mackenzie basin canada we report li isotopic compositions for river waters and suspended sediments of about 40 rivers sampled within the mackenzie river basin in northwestern canada the aim of this study is to characterize the behaviour of li and its isotopes during weathering at the scale of a large mixed lithology basin the mackenzie river waters display systematically heavier li isotopic compositions relative to source rocks and suspended sediments the range in delta li 7 is larger in dissolved load from 9 3 parts per thousand to 29 0 parts per thousand compared to suspended sediments from 1 7 parts per thousand to 3 2 parts per thousand which are not significantly different from delta li 7 values in bedrocks our study shows that dissolved li is essentially derived from the weathering of silicates and that its isotopic composition in the dissolved load is inversely correlated with its relative mobility when compared to na the highest enrichment of li 7 in the dissolved load is reported when li is not or poorly incorporated in secondary phases after its release into solution by mineral dissolution this counterintuitive observation is interpreted by the mixing of water types derived from two different weathering regimes producing different li isotopic compositions within the mackenzie river basin the incipient weathering regime characterizing the rocky mountains and the shield areas produces li 7 enrichment in the fluid phase that is most simply explained by the precipitation of oxyhydroxide phases fractionating li isotopes the second weathering regime is found in the lowland area and produces the lower delta li 7 waters but still enriched in li 7 compared to bedrocks and the most li depleted waters compared to na fractionation factors suggest that the incorporation of li in clay minerals is the mechanism that explains the isotopic composition of the lowland rivers the correlation of boron and lithium concentrations found in the dissolved load of the mackenzie rivers suggests that precipitation of clay minerals is favoured by the relatively high residence time of water in groundwater in the shield and rocky mountains li isotopes suggest that clay minerals are not forming and that secondary minerals with stronger affinity for li 7 appear although the weathering mechanisms operating in the mackenzie basin need to be characterized more precisely the li isotope data reported here clearly show the control of li isotopes by the weathering intensity the spatial diversity of weathering regimes resulting from a complex combination of factors such as topography geology climate and hydrology explains in fine the spatial distribution of li isotopic ratios in the large drainage basin of the mackenzie river there is no simple relationship between li isotopic composition and chemical denudation fluxes in the mackenzie river basin

riverine behaviour of uranium and lithium isotopes in an actively glaciated basaltic terrain this study presents u and li isotope and major and trace element data for the dissolved load suspended particulates and bedload for icelandic rivers draining predominantly basaltic catchments physical erosion rates range from 920 to 2084 t km2 yr with the higher values associated with glacier fed rivers chemical erosion rates range from 45 to 91 t km2 yr with lower rates being associated with glacier fed rivers uranium activity ratios 234u 238u are close to secular equilibrium in the suspended and bedloads but all dissolved load samples show values greater than unity ranging from 1 13 to 2 41 the highest 234u 238u values are found in glacier fed rivers and can be attributed to recoil effects as grinding by glaciers locally enhances rates of physical weathering activity ratios in glacial rivers decrease with distance from the glacial source due to input from non glacial tributaries which have high levels of dissolved uranium and lower activity ratios in contrast in non glacial rivers uranium activity ratios increase with distance downstream due to continued weathering in soils and of bedrock the 7li value of the suspended load is always lower than that of the bedload due to preferential retention of 6li in secondary minerals during weathering in turn the 7li value of the dissolved load is always greater than that of the bedload ranging from 17 0 to 43 7 7li for the dissolved load decreases with increasing levels of dissolved silicon and the saturation index of secondary minerals which suggests that 7li decreases with increasing chemical weathering there is no correlation between 7li values and uranium activity ratios for the dissolved load for non glacial rivers but for glacier fed rivers there is an increase in 7li with increasing 234u 238u suggesting that where physical comminution of mineral grains by glaciers is high chemical weathering is suppressed and vice versa

experimental investigations of the weathering of suspended sediment by alpine glacial meltwater the magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments constrained by field data from haut glacier d arolla valais switzerland the effects of the water to rock ratio particle size crushing repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated these free drift experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment these data have important implications for hydrological interpretations based on the solute content of glacial meltwater mixing model calculations geochemical denudation rates and solute provenance studies

seasonal sensitivity of weathering processes hints from magnesium isotopes in a glacial stream seasonal changes in river chemistry offer the potential to assess how weathering processes respond to changing meteorological parameters and ultimately how chemical weathering might respond to climatic parameters systematic seasonal variations in magnesium isotope ratios the 26mg 24mg ratio expressed as 26mg in per mil units are reported in stream waters from a mono lithological granitic weathering limited first order catchment from the swiss alps damma glacier rain ground and pore waters in addition to plants rocks mineral separates and soil are also reported the concentration response of the river waters is attenuated compared to the large changes in discharge however the systematic trends in the isotope data imply that either the source of the mg changes in a systematic manner or that the process by which mg is released into solution changes as a function of discharge the two first order observations in the data that need to be explained are 1 the systematic enrichment in 24mg in the stream waters compared to the granitic rocks they drain and 2 a systematic increase in 26mg in the waters during the summer melt season both observations which are similar to many other rivers draining silicate rock can either be accounted for by 1 conservative mixing between at least two different sources of mg in addition to precipitation inputs or 2 process related fractionation if the stream water compositions can be rationalised by multi component mixing there is at least one unidentified component with a 26mg 1 2 this is considered unlikely multiple physicochemical processes could fractionate mg isotope ratios such as 1 preferential leaching of 24mg 2 exchange of mg onto or from mineral surfaces and into interlayer sites of clays 3 uptake by plants and 4 26mg could be preferentially retained during the formation of secondary phases such as clays amorphous phases or oxides these processes are not mutually exclusive and distinguishing between them at a field scale is not trivial but significant biological uptake is improbable at this site unless there is a non identified external input of mg 26mg must be accumulating in solid phase residues in the catchment because of at least one physicochemical process such processes are likely well described at least in the first order by a rayleigh distillation model simple calculations illustrate how much 26mg would accumulate in the catchment per unit time in the first order the isotopic enrichments in the solids are so small that they would not be detectable for the time scales that are relevant to this field site in spite of the marked impact on the water chemistry the seasonal signal detected by mg isotope ratios is promising for using them with a better understanding of fractionation mechanisms to quantify how specific weathering processes impact upon both export fluxes and retention of elements within catchments

the ubiquitous nature of accessory calcite in granitoid rocks implications for weathering solute evolution and petrogenesis calcite is frequently cited as a source of excess ca sr and alkalinity in solutes discharging from silicate terrains yet no previous effort has been made to assess systematically the overall abundance composition and petrogenesis of accessory calcite in granitoid rocks this study addresses this issue by analyzing a worldwide distribution of more than 100 granitoid rocks calcite is found to be universally present in a concentration range between 0 028 to 18 8 g kg 1 mean 2 52 g kg 1 calcite occurrences include small to large isolated anhedral grains fracture and cavity infillings and sericitized cores of plagioclase no correlation exists between the amount of calcite present and major rock oxide compositions including cao ion microprobe analyses of in situ calcite grains indicate relatively low sr 120 to 660 ppm negligible rb and 87sr 86sr ratios equal to or higher than those of coexisting plagioclase solutes including ca and alkalinity produced by batch leaching of the granitoid rocks 5 co2 in di water for 75 d at 25 c are dominated by the dissolution of calcite relative to silicate minerals the correlation of these parameters with higher calcite concentrations decreases as leachates approach thermodynamic saturation in longer term column experiments 1 5 yr reactive calcite becomes exhausted solute ca and sr become controlled by feldspar dissolution and 87sr 86sr by biotite oxidation some accessory calcite in granitoid rocks is related to intrusion into carbonate wall rock or produced by later hydrothermal alteration however the ubiquitous occurrence of calcite also suggests formation during late stage subsolidus magmatic processes this conclusion is supported by petrographic observations and 87sr 86sr analyses a review of thermodynamic data indicates that at moderate pressures and reasonable co2 fugacities calcite is a stable phase at temperatures of 400 to 700 c

dissolved oxygen variations in alpine glacial meltwaters recent models of chemical weathering in alpine glacial meltwaters suggest that sulphide oxidation is a major source of solute in the distributed component of the subglacial hydrological system this reaction requires o2 and may lower dissolved oxygen levels to below saturation with respect to the atmosphere this should result in an inverse association between so72 and dissolved oxygen saturation however measurements of o2 saturation in bulk meltwaters draining the haut glacier d arolla switzerland show that there is a positive association between so42 and o2 saturation the o2 content of glacial meltwaters depends on the initial content of snow and icemelt which may be controlled by the rate of melting and the kinetic balance between o2 losses e g sulphide oxidation microbial respiration and gains e g diffusion of o2 into solution

tsushima current water at the entrance of the korea strait in autumn abstract hydrographic data gathered at 32 5 34 5 n 123 5 128 5 e in autumn 1986 show the similarity to the mean condition for 1961 1983 korean coastal water and hwanghae cold water are found to the north of 33 5 n coastal water of the china continent is confined to the west of 125 e between tsushima current water and two coastal waters a horizontal thermohaline front is located in the direction of southwest northeast a westward extension of tsushima current water from south of cheju island is found as a typical feature of the hydrography and it is directed toward the yellow sea after reaching 124 e

an asymmetric upwind flow yellow sea warm current 1 new observations in the western yellow sea 1 the winter water mass along the yellow sea trough yst especially on the western side of the trough is considerably warmer and saltier than the ambient shelf water mass this observed tongue shape hydrographic feature implies the existence of a winter along trough and onshore current often referred to as the yellow sea warm current yswc however the yswc has not been confirmed by direct current measurements and therefore skepticism remains regarding its existence some studies suggest that the presence of the warm water could be due to frontal instability eddies or synoptic scale wind bursts it is noted that in situ observations used in most previous studies were from the central and eastern sides of the yst even though it is known that the warm water core is more pronounced along the western side data from the western side have been scarce here we present a set of newly available chinese observations including some from a coordinated effort involving three chinese vessels in the western yst during the 2006 2007 winter the data show unambiguously the existence of the warm current on the western side of yst both the current and hydrography observations indicate a dominant barotropic structure of yswc the westward deviation of yswc axis is particularly obvious to the south of 35 n and is clearly associated with an onshore movement of warm water to the north of 35 n the yswc flows along the bathymetry with slightly downslope movement we conclude that the barotropic current is mainly responsible for the warm water intrusion while the ekman and baroclinic currents play an important but secondary role these observations help fill an observational gap and establish a more complete view of the yswc

high temperature strontium stable isotope behaviour in the early solar system and planetary bodies abstract this study presents comprehensive strontium stable isotope 88sr 86sr data measured by multiple collector inductively coupled plasma mass spectrometry mc icp ms for a suite of carbonaceous chondrites differentiated meteorites lunar martian and terrestrial samples carbonaceous chondrites comprise a mixture of refractory inclusions and chondrules that have light 88sr values between 0 35 to 0 05 and matrix material that possesses a heavy 88sr composition of 0 65 confirming the results of earlier studies consequently bulk carbonaceous chondrites are relatively heterogeneous in composition ranging from 0 12 to 0 35 most likely reflecting clast matrix variability the light 88sr compositions of the refractory inclusions are consistent with mass dependent fractionation of other refractory elements ca and eu and are most likely produced by non equilibrium fractionation undercooling in the nebula gas during condensation of hibonite from the solar nebula simon and depaolo 2010 stable calcium isotopic composition of meteorites and rocky planets earth planet sci lett 289 457 466 carbonaceous chondrites angrites and martian meteorites have indistinguishable compositions at the level of analytical uncertainty of this study however statistical analysis indicates that melts derived from the earth s mantle have heavier 88sr values than bulk carbonaceous chondrites and martian meteorites but compositions indistinguishable from eucrites 88sr 0 26 0 12 moreover terrestrial basalts and andesites have restricted 88sr values 0 30 0 07 suggesting that mantle melting delivers rather homogenous melts to the earth s surface with respect to 88sr in contrast glasses from evolved terrestrial rocks and lunar basalts extend to very light 88sr values 0 20 the sr stable isotope composition covaries with europium anomaly eu eu as an index of plagioclase fractionation and 88sr can be successfully modelled by the heavy isotopes of sr being preferentially partitioned into plagioclase with a fractionation factor of 1 0007 for 88sr 86sr our results demonstrate that sr stable isotopes may be significantly fractionated at high temperatures and their measurement can provide insights into planetary evolution and magmatic processes

a silicate weathering mechanism linking increases in marine 87sr 86sr with global glaciation the 87sr 86sr ratio of sea water is generally regarded as a proxy for the rate of chemical weathering of the continents interpretation of the 87sr 86sr record in marine limestones requires an understanding of how changes in this quantity are linked to climate and tectonic events a connection between the strontium isotope record and the extent of global glaciation has been proposed1 8 but without a well established mechanism glaciation may influence marine 87sr 86sr by changing global riverine sr fluxes that is rock weathering rates and or 87sr 86sr ratios that is relative mineral weathering rates here we investigate how the 87sr 86sr release from silicate weathering is affected by glaciation using the sr isotope systematics of granitoid soils on alpine glacial moraines in the wind river range wyoming we observe a negative correlation between the 87sr 86sr ratio of exchangeable sr in soils and the soil age indicating that the 87sr 86sr ratio of sr released in the early stages of weathering is significantly higher than in later stages we estimate that this mechanism can increase global riverine 87sr 86sr by an average of 0 0002 during periods of glacial interglacial cycling when superimposed on long term trends controlled by tectonic processes2 7 9 10 this shift can account for the correlation between the rate of change of marine 87sr 86sr and the intensity of glaciation over at least the past 10 myr

episodic surface intrusions in the yellow sea during relaxation of northerly winds the surface currents over the yellow and east china seas are mapped from the geostationary ocean color imager goci based on a composite of six intrusion events in january april the strong northward surface current in the yellow sea is shown to be concentrated along the deep trough accompanied by a broad northward surface current over the east china sea from the corresponding surface winds the episodic northward surface flow bursts appear to be associated with abrupt changes from the strong northerly winds to weak southerly winds during cold front passages a three dimensional model driven with observed surface winds is used to simulate the observed shelf wide response to northerly winds there is an outstanding agreement between the simulated and observed surface currents the surface intrusion in the yellow sea is shown to be driven primarily by a barotropic longitudinal surface slope while the strong northward current in the east china sea is associated with a coastal trapped wave moreover the surface intrusion is associated with a large volume transport suggesting that the transient intrusions could be important in the northward heat transport the unprecedented capability of goci satellite in providing a regional circulation pattern in conjunction with complementary model simulations could contribute greatly to understanding of the dynamics of the yellow and east china seas

reassessing the stable δ88 86sr and radiogenic 87sr 86sr strontium isotopic composition of marine inputs the stable strontium isotope system 88 86sr has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system the principal output flux of oceanic sr however in order to be able to interpret carbonate driven variations in 88 86srseawater a robust understanding of 88 86srinput is required surprisingly only a limited amount of 88 86sr data currently exists for rivers and hydrothermal fluids thus this study assesses the variability of 88 86sr and 87sr 86sr in global rivers hydrothermal fluids and porewaters as well as minor marine sr sources such as continental dust rainwater and glacial ice our analyses broadly confirm the findings of krabbenhoft et al 2010 and reveal flux weighted 88 86srriverine and 87sr 86srriverine compositions of 0 32 and 0 71299 respectively the hydrothermal fluids analysed in this study are consistent with an end member 88 86srhydrothermal composition that is the same as the oceanic crust at 0 24 although three samples that display 88 86sr compositions offset from the seawater hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive 88 86srhydrothermal to higher values porewater fluids obtained from sediment cores in the atlantic and pacific oceans have 88 86sr compositions within error of seawater 0 39 implying that the diagenetic flux of sr may not significantly affect the 88 86sr composition of seawater continental loess samples have 88 86sr compositions that are consistently lighter than or equal to terrestrial silicates with their tendency to lower values thought to reflect the preferential removal of heavier sr isotopes into solution during weathering finally rainwater and glacial ice samples have 88 86sr compositions that are also isotopically lighter than their associated water sources a factor that may be attributed to interaction with isotopically light loess and additional sr contributions from the bedrock together the principal marine inputs define flux weighted oceanic 88 86srinput and 87sr 86srinput compositions of 0 32 and 0 71161 these values are consistent with an elevated supply of riverine sr to the oceans due to increased post glacial weathering but require the enhanced weathering of exposed carbonate shelves during glacial periods or significant changes in the rate of carbonate burial to match observed changes in the 87sr 86sr ratio of seawater our results confirm that providing a diagenetically robust proxy can be found the 88 86sr and 87sr 86sr isotope systems should provide a useful proxy for investigating changes in the marine carbonate system through time

weathering processes catchment geology and river management impacts on radiogenic 87sr 86sr and stable δ88 86sr strontium isotope compositions of canadian boreal rivers abstract radiogenic 87sr 86sr and stable 88 86sr strontium isotope compositions spanning a calendar year are reported for rivers from across subarctic canada that drain contrasting lithologies ranging from precambrian bedrock koksoak great whale and la grande rivers of northern quebec to carbonate and clastic phanerozoic sedimentary rocks of the western interior platform nelson river of central and western canada the 87sr 86sr isotopic compositions of the river waters reflect the underlying geology with rivers draining the precambrian shield having higher 87sr 86sr ratios 0 727 0 734 than the phanerozoic dominated nelson river 0 713 the stable strontium isotope values 88 86sr range from 0 26 to 0 39 with the values for the nelson river overlapping those of the other three rivers that have not been developed for hydroelectric power show a seasonal variation in the 87sr 86sr ratios whereas those that have been diverted or dammed show little or no seasonal variation due to increased residence time of their water in hydroelectric reservoirs the three rivers from northern quebec show discrete ranges in their 87sr 86sr and 88 86sr isotope compositions that correlate with the ca sr and na sr ratios of the river water these correlations are interpreted to reflect differential chemical weathering of felsic versus mafic source rocks and or of surficial sediment vs bedrock sources

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

strontium isotope fractionation of planktic foraminifera and inorganic calcite we have investigated the strontium isotope fractionation 88 86srcarb aq between inorganic calcite and aqueous sr2 ions by precipitation experiments at a constant temperature of 25 c and precipitation rates r ranging from 102 3 to 104 2 mol m2 h strontium isotope ratios were measured using the 87sr 84sr double spike technique it was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate view the mathml source the measured 88 86sr values are significantly correlated with previously measured 44 40ca and sr ca values of the same calcite samples 88 86srcarb aq 0 18 44 40cacarb aq 0 01 view the mathml source the slope of 88sr 86sr versus 44ca 40ca fractionation is 0 18 0 04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions but not with isotope fractionation in a diffusive boundary layer using published equilibrium 44 40cacarb aq and view the mathml source values we estimate the equilibrium isotope fractionation of strontium to be very close to zero 88 86sreq carb aq 0 01 0 06 this estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust the results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera specimens of two warm water species globigerinoides ruber and globigerinoides sacculifer were picked from the holocene section of a caribbean sediment core we found no significant difference in 88 86sr between the two species in addition g ruber specimens from marine isotope stage 2 in the same core show 88 86sr values identical to the holocene specimens the strontium isotopes of both foraminifera species are strongly fractionated 88 86srcarb aq 0 248 0 005 when compared to published data of other major marine calcifiers applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates comparable in magnitude to rates known from scleractinian reef corals this interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by kisakurek et al 2011 which was based on calcium isotopes and elemental sr ca ratios

strontium isotopes trace biological activity in the critical zone along a climate and vegetation gradient abstract weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock the geogenic nutrient pathway however the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter the organic nutrient cycle isotope ratios of strontium sr an element that behaves similarly to ca in ecosystems confer two types of information radiogenic sr isotopes inform as to the sources of sr and the degree of weathering while stable sr isotopes constrain partitioning between compartments of the critical zone bedrock water secondary solids and plants to date however neither the reactions nor the mass balance between compartments that fractionate sr isotopes nor the fractionation factors involved are well understood here we present geochemical budgets of sr using radiogenic and stable sr isotopes and ca sr ratios at four sites along a substantial climate and primary production gradient in the coastal mountains of chile we found that sr release through weathering is isotopically congruent and released sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool despite this the 88sr 86sr ratio of bio available sr which should reflect the ratio of dissolved sr is higher than that of rock and regolith we propose that this offset is caused by plants while 88sr 86sr in plant organs at the four study sites systematically increased from roots towards their leaves whole plant sr isotope compositions indicate preferential uptake of light sr into plants with a fractionation of up to 0 3 relative to the bio available pool despite this strong biological fractionation 88sr 86sr ratios in bio available sr do not covary with biomass production across our study sites because with greater plant growth sr is recycled more times after release by weathering an isotope neutral process rather the loss of sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio available sr organic solids thus appear to constitute a significant export path of elements released during weathering with the removal of solid plant debris reducing the recycling factor of sr and possibly that of other mineral nutrients too

the great tonalite sill emplacement into a contractional shear zone and implications for late cretaceous to early eocene tectonics in southeastern alaska and british columbia the late cretaceous to early tertiary great tonalite sill of southeast alaska and british columbia is a very long 1 000 km and thin 25 km orogen parallel composite batholith which lies between the insular superter rane including the alexander and wrangellia terranes and the intermontane superterrane including the stikine and cache creek terranes the batholith is delineated by many steep sheet like plutons which are dominated by northwest southeast striking concordant fabrics with steep lineations that formed during deformation in a country rock shear zone prior to the complete crystallization of the magmas deformation in this shear zone is dominated by northeast southwest directed contraction orthogonal to the orogenic strike associated with a component of northeast over southwest high angle shear the steep multiple dike like nature of the body and its emplacement during orogenic contraction imply that ascent and emplacement have been achieved by dike wedging mechanisms along the deep reaching shear zone the remarkable narrowness of the great tonalite sill is probably the result of melting at the base of a very localized zone of thickened crust produced by the associated narrow contractional shear zone extending along the orogen length such a shear zone of late cretaceous to early tertiary age lying along 800 km of the possible boundary between the insular and intermontane superterranes implies that it may represent the actual boundary between them if this hypothesis is correct it implies that the large scale tectonic regime during emplacement of the great tonalite sill was predominantly orthogonal and not obliquely dextral as has been indicated from paleomagnetic data

hydrogeochemistry of seasonal flow regimes in the chena river a subarctic watershed draining discontinuous permafrost in interior alaska usa abstract thawing of permafrost and a shift in the timing of major seasonal transitions spring melt and fall freeze up are two anticipated effects of climate warming in northern regions these fundamental changes in terrestrial ecosystems could have major ramifications for the timing and fluxes of carbon and nutrient exports from watersheds and the geochemical signatures of northern rivers discontinuous permafrost which underlies watersheds in interior alaska usa is expected to degrade rapidly in response to climate warming and this will likely alter subsurface flows and flow paths water residence times water soil and water rock interactions this study of the chena river in interior alaska was undertaken to quantify dissolved organic carbon doc total dissolved nitrogen tdn major ion strontium isotope and stable oxygen and hydrogen isotope values during two year long time series sampling periods our goal was to identify the hydrogeochemical signatures associated with the major seasonal flow regimes periods of increased discharge such as spring melt and major summer precipitation events yielded elevated doc and tdn concentrations diluted major ion concentrations and shifted stable oxygen and hydrogen isotope ratios from base flow toward precipitation values during dry summer periods nutrient concentrations decreased and strontium isotope values were indicative of a higher proportion of silicate versus carbonate mineral dissolution winter base flow had a unique geochemical signal with a slight increase in tdn concentrations compared to typical summer conditions and a lower proportion of silicate versus carbonate mineral dissolution since flow paths in subarctic watersheds can change dramatically over the course of a year we interpreted our results within the context of a schematic model for subsurface flow to identify how permafrost degradation might affect nutrient exports and hydrogeochemical patterns in these watersheds

hydrochemistry of carbonate terrains in alpine glacial settings nearly 200 analyses of meltwaters ice and snow from three alpine glacial sites in carbonate terrain are summarized and discussed in terms of sources of solutes and kinetic controls on the progress of weathering reactions most data derive from the swiss glacier de tsanfleuron which is based on cretaceous and tertiary pure and impure limestones two other sites marmolada italian dolomites and the saskatchewan glacier alberta are based on a mixed calcitic dolomitic substrate most solutes originate from carbonate dissolution moreover where pyrite is present its oxidation supplies significant sulphate and forces more dissolution of carbonate the ratios sr2 ca2 and mg2 ca2 are much higher in tsanfleuron melt waters than local bedrock a phenomenon that can be reproduced in the laboratory at small percentages of dissolution these anomalous ratios are attributed to incongruent dissolution of traces of the metastable carbonates mg calcite and aragonite these phases also provide na to solution k is argued to originate mainly by ion exchange on clays with solute ca2 quartz and very minor feldspar dissolution are also inferred locally enhanced input from atmospheric sources is recognized by high cl and associated na the progress of weathering reactions has been evaluated by the trends in the data computer modelling and some simple laboratory experiments the most dilute samples show a trend towards removal of co2 to low partial pressures c 10 5 5 atmospheres reflecting initially rapid carbonate dissolution and relatively slow dissolution of gaseous co2 later addition of atmospheric co2 or acid from pyrite oxidation allows further carbonate dissolution but solutions show a wide range of saturations and co2 pressures as high as 10 2 2 where pyrite oxidation is important in a carbonate terrain measurement of electroconductivity corrected to 25 c and alkalinity in the field allows the following preliminary deductions where meq stands for milliequivalents formula presented where s is the minimum meq ca2 mg2 produced by simple dissolution of carbonate unconnected with pyrite oxidation as with any proxy method these deductions do not remove the need for chemical analysis of waters in a given study area copyright 1994 john wiley sons ltd

tracing river chemistry in space and time dissolved inorganic constituents of the fraser river canada abstract the fraser river basin in southwestern canada bears unique geologic and climatic features which make it an ideal setting for investigating the origins transformations and delivery to the coast of dissolved riverine loads under relatively pristine conditions we present results from sampling campaigns over three years which demonstrate the lithologic and hydrologic controls on fluxes and isotope compositions of major dissolved inorganic runoff constituents dissolved nutrients major and trace elements 87 sr 86 sr d a time series record near the fraser mouth allows us to generate new estimates of discharge weighted concentrations and fluxes and an overall chemical weathering rate of 32 t km 2 y 1 the seasonal variations in dissolved inorganic species are driven by changes in hydrology which vary in timing across the basin the time series record of dissolved 87 sr 86 sr is of particular interest as a consistent shift between higher more radiogenic values during spring and summer and less radiogenic values in fall and winter demonstrates the seasonal variability in source contributions throughout the basin this seasonal shift is also quite large 0 709 0 714 with a discharge weighted annual average of 0 7120 2 s d 0 0003 we present a mixing model which predicts the seasonal evolution of dissolved 87 sr 86 sr based on tributary compositions and water discharge this model highlights the importance of chemical weathering fluxes from the old sedimentary bedrock of headwater drainage regions despite their relatively small contribution to the total water flux

constraining the marine strontium budget with natural strontium isotope fractionations 87sr 86sr δ88 86sr of carbonates hydrothermal solutions and river waters we present strontium sr isotope ratios that unlike traditional 87sr 86sr data are not normalized to a fixed 88sr 86sr ratio of 8 375209 defined as 88 86sr 0 relative to nist srm 987 instead we correct for isotope fractionation during mass spectrometry with a 87sr 84sr double spike this technique yields two independent ratios for 87sr 86sr and 88sr 86sr that are reported as 87sr 86sr and 88 86sr respectively the difference between the traditional radiogenic 87sr 86sr normalized to 88sr 86sr 8 375209 and the new 87sr 86sr values reflect natural mass dependent isotope fractionation in order to constrain glacial interglacial changes in the marine sr budget we compare the isotope composition of modern seawater 87sr 86sr 88 86sr seawater and modern marine biogenic carbonates 87sr 86sr 88 86sr carbonates with the corresponding values of river waters 87sr 86sr 88 86sr river and hydrothermal solutions 87sr 86sr 88 86sr hydend in a triple isotope plot the measured 87sr 86sr 88 86sr river values of selected rivers that together account for not vert similar18 of the global sr discharge yield a sr flux weighted mean of 0 7114 8 0 315 8 the average 87sr 86sr 88 86sr hydend values for hydrothermal solutions from the atlantic ocean are 0 7045 5 0 27 3 in contrast the 87sr 86sr 88 86sr carbonates values representing the marine sr output are 0 70926 2 0 21 2 we estimate the modern sr isotope composition of the sources at 0 7106 8 0 310 8 the difference between the estimated 87sr 86sr 88 86sr input and 87sr 86sr 88 86sr output values reflects isotope disequilibrium with respect to sr inputs and outputs in contrast to the modern ocean isotope equilibrium between inputs and outputs during the last glacial maximum 10 30 ka before present can be explained by invoking three times higher sr inputs from a uniquely glacial source weathering of shelf carbonates exposed at low sea levels our data are also consistent with the weathering peak hypothesis that invokes enhanced sr inputs resulting from weathering of post glacial exposure of abundant fine grained material

basal sediment evacuation by subglacial meltwater suspended sediment transport from haut glacier d arolla switzerland proglacial suspended sediment transport was monitored at haut glacier d arolla switzerland during the 1998 melt season to investigate the mechanisms of basal sediment evacuation by subglacial meltwater sub seasonal changes in relationships between suspended sediment transport and discharge demonstrate that the structure and hydraulics of the subglacial drainage system critically influenced how basal sediment was accessed and entrained under hydraulically inefficient subglacial drainage at the start of the melt season sediment availability was generally high but sediment transport increased relatively slowly with discharge later in the melt season sediment transport increased more rapidly with discharge as subglacial meltwater became confined to a spatially limited network of channels following removal of the seasonal snowpack from the ablation area flow capacity is inferred to have increased more rapidly with discharge within subglacial channels because rapid changes in discharge during highly peaked diurnal runoff cycles are likely to have been accommodated largely by changes in flow velocity basal sediment availability declined during channelization but increased throughout the remainder of the monitored period resulting in very efficient basal sediment evacuation over the peak of the melt season increased basal sediment availability during the summer appears to have been linked to high diurnal water pressure variation within subglacial channels inferred from the strong increase in flow velocity with discharge basal sediment availability therefore appears likely to have been increased by 1 enhanced local ice bed separation leading to extra channel flow excursions and sol or 2 the deformation of basal sediment towards low pressure channels due to a strong diurnally reversing hydraulic gradient between channels and areas of hydraulically less efficient drainage copyright 2005 john wiley sons ltd

application of ground penetrating radar to the identification of subsurface piping in blanket peat natural soil pipes are common and significant in upland blanket peat catchments yet there are major problems in finding and defining the subsurface pipe networks this is particularly important because pipeflow can contribute a large proportion of runoff to the river systems in these upland environments and may significantly influence catchment sediment and solute yields traditional methods such as digging soil pits are destructive and time consuming particularly in deep peat and only provide single point sources of information this paper presents results from an experiment to assess the use of ground penetrating radar gpr to remotely sense pipes in blanket peat the technique is shown to be successful in identifying most of the pipes tested in the pilot catchment comparison of data on pipes identified by gpr and verified by manual measurement suggests that pipes can be located in the soil profile with a depth accuracy of 20 to 30 cm gpr identified pipes were found throughout the soil profile however those within 10 20 cm of the surface could not be identified using the 100 or 200 mhz antennae due to multiple surface reflections generally pipes smaller than 10 cm in diameter could not be identified using the technique although modifications are suggested that will allow enhanced resolution future work would benefit from the development of dual frequency antennae that will allow the combination of high resolution data with the depth of penetration required in a wetland environment the gpr experiment shows that pipe network densities were much greater than could be detected from surface observation alone thus gpr provides a non destructive fast technique which can produce continuous profiles of peat depth and indicate pipe locations across survey transects copyright 2002 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

controls on stable strontium isotope fractionation in coccolithophores with implications for the marine sr cycle abstract the controls on stable sr isotope fractionation into the calcite produced by the coccolithophore species emiliania huxleyi coccolithus pelagicus spp braarudii and gephyrocapsa oceanica are investigated each species has been cultured under controlled laboratory conditions at a range of temperatures 10 25 c to test the potential of 88 86 sr as a proxy for growth rate and or sea surface temperature coccolithophores are one of the most abundant pelagic calcifiers since sr substitutes to some degree for ca in their calcite coccoliths coccolithophores represent a significant output of sr from seawater potentially influencing the 88 86 sr mass balance in the modern oceans the coccoliths are investigated for their 88 86 sr sr ca and 18 o measured as function of temperature as temperature is increased all species show a negative stable sr isotopic fractionation related to a temperature controlled growth rate we infer the shift of 88 86 sr to lighter values as indicative of a kinetic control on the isotope fractionation revealing the potential of 88 86 sr as a proxy for growth rate which in these experiments is primarily dictated by temperature the results from these experiments indicate that coccolithophore calcite incorporates sr with a very light 88 86 sr isotope composition as low as 0

water flow through temperate glaciers understanding water movement through a glacier is fundamental to several critical issues in glaci ology including glacier dynamics glacier induced floods and the prediction of runoff from glacierized drainage basins to this end we have synthesized a conceptual model of water movement through a temper ate glacier from the surface to the outlet stream pro cesses that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology where a glacier is covered by a layer of porous perme able firn the accumulation zone the flux of water to the glacier interior varies slowly because the firn tempo rarily stores water and thereby smooths out variations in the supply rate in the firn free ablation zone in con trast the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time water moves from the surface to the bed through an upward branching arborescent net work consisting of both steeply inclined conduits formed by the enlargement of intergranular veins and gently inclined conduits spawned by water flow along the bottoms of near surface fractures crevasses engla cial drainage conduits deliver water to the glacier bed at a limited number of points probably a long distance downglacier of where water enters the glacier englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn their size adjusts so that they are usually full of water and flow is pressurized in contrast water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms flow is otherwise in an open channel configuration the subglacial drainage system typically consists of several elements that are distinct both morphologically and hydrologically an up glacier branching arborescent network of channels in cised into the basal ice conveys water rapidly much of the water flux to the bed probably enters directly into the arborescent channel network which covers only a small fraction of the glacier bed more extensive spatially is a nonarborescent network which commonly includes cav ities gaps between the glacier sole and bed channels incised into the bed and a layer of permeable sediment the nonarborescent network conveys water slowly and is usually poorly connected to the arborescent system the arborescent channel network largely collapses during winter but reforms in the spring as the first flush of meltwater to the bed destabilizes the cavities within the nonarborescent network the volume of water stored by a glacier varies diurnally and seasonally small temper ate alpine glaciers seem to attain a maximum seasonal water storage of 200 mm of water averaged over the area of the glacier bed with daily fluctuations of as much as 20 30 mm the likely storage capacity of subglacial cavities is insufficient to account for estimated stored water volumes so most water storage may actually occur englacially stored water may also be released abruptly and catastrophically in the form of outburst floods

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

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

seasonal changes in the radiogenic and stable strontium isotopic composition of xijiang river water implications for chemical weathering seasonal changes in strontium sr isotopic systematics in large rivers can effectively track temporal variations in regional chemical weathering and help to better constrain the sr isotopic budget of global oceans however such records are scarce here we present a year long time series of both radiogenic and stable sr isotope measurements 87sr 86sr and 88sr from river water at guiping in the middle reaches of the xijiang river south china temporal changes in chemical weathering in the drainage basin were investigated by recording seasonal changes in the composition of both sr isotopes and major ions in the river water river water 87sr 86sr values range from 0 708487 to 0 710336 with most values being 0 7092 are generally accompanied by high rb sr ratios and low ph and 13c of dissolved inorganic carbo dic and occur during periods of large river flux this indicates that the contribution to the chemistry of river water from the weathering of silicate rocks is enhanced during rainy seasons seasonal variation in river water 88sr is large from 0 147 to 0 661 with higher 88sr values generally corresponding to higher 87sr 86sr values again low 88sr values 0 3 suggest a dominant contribution from the weathering of carbonate rocks whereas the high 88sr values may represent a contribution from intensive weathering of silicate rocks using the time series data we estimated the flux weighted averages of sr concentration 87sr 86sr and 88sr for the xijiang river to be 1 00 mol l 0 70960 and 0 38 respectively the sr concentration and 87sr 86sr results are close to previous estimates while the 88sr value is amongst the highest recorded for the large rivers of the world and is close to that of seawater our results indicate that large rivers draining through tropical sub tropical regions could play an important role in regulating the stable sr isotopic budget of global oceans

fluvial suspended sediment transport from cold and warm based glaciers in svalbard an analysis of temporal variability in proglacial suspended sediment concentration is undertaken using time series data collected from three svalbard basins which include one largely cold based glacier austre broggerbreen one largely warm based glacier finsterwalderbreen and one intermediate polythermal glacier erdmannbreen the temporal variability in proglacial suspended sediment concentration is analysed using multiple regression techniques in which discharge is supplemented by other predictors acting as surrogates for variability in sediment supply at diurnal medium term and seasonal timescales these multiple regression models improve upon the statistical explanation of suspended sediment concentration produced by simple sediment rating curves but need to account for additional stochastic elements within the time series before they may be considered successful an interpretation of the physical processes which are responsible for the regression model characteristics is offered as a basis for comparing the different arctic glaciofluvial suspended sediment transport systems with that of their better known temperate glaciofluvial counterparts it is inferred that the largely warm based glacier is dominated by sediment supply from subglacial reservoirs which evolve in a similar manner to temperate glaciers and which cause a pronounced seasonal exhaustion of suspended sediment supply the largely cold based glacier however is dominated by sediment supply from marginal sources which generate a responsive system at short time scales but no significant seasonal pattern the intermediate polythermal glacier basin which was anticipated to be similar to the warm based glacier instead shows a highly significant seasonal increase in suspended sediment supply from an unusual subglacial reservoir emerging under pressure in the glacier foreland the temperate model of glaciofluvial suspended sediment transport is therefore found to be of limited use in an arctic context copyright 1999 john wiley sons ltd