oxygen and carbon isotopes in modern fresh water ostracod valves assessing vital offsets and autecological effects of interest for palaeoclimate studies abstract the isotopic composition of modern benthic ostracod and mollusc carbonate the oxygen isotope composition of lake water 18ow the carbon isotope composition of dissolved inorganic carbon 13cdic and water temperatures were monitored during a year at different water depths in two lakes ammersee and starnberger see southern germany the aim was to test whether the valves are built in isotopic equilibrium and how seasonal water temperatures are recorded in the shells we find systematic offsets between 18o of valve carbonate compared to 18o expected for a theoretical calcite formed in isotopic equilibrium offsets are higher than 2 for different species of the candona group 1 5 for cytherissa lacustris and around 0 8 for limnocythere inopinata and darwinula stevensoni they seem to be constant for all instars of a species and temperature independent mean water temperatures of the calcification period are readily reflected in the valve 18o if corrected for the offsets 13c of valve carbonate is mainly controlled by 13c of the dissolved carbonate in ambient lake water but seems to be biased by micro habitat effects and vital offsets the study provides information on the seasonality of valve formation thus potentially allowing the quantification of temporal and spatial water temperature gradients from specific 18o records

relationships between interannual variability of glacier mass balance and climate the interannual variability of glacier mass balance is expressed by the standard deviation of net balance which varies from about 0 1 to 1 4 m a for a sample of 115 glaciers with at least 5 years of record the standard deviation of net balance is strongly correlated with the mass balance amplitude half the difference between winter and summer balances for 60 glaciers so the amplitude can be estimated from net balance standard deviation for the other 55 glaciers where winter and summer balances are unavailable the observed and calculated mass balance amplitudes for the 115 glaciers show contrasts between the arctic and lower latitudes and between maritime and continental regions the interannual variability of mass balance means that balances must be measured for at least a few years to determine a statistically reliable mean balance for any glacier the net balance of the greenland ice sheet is still not accurately known but its standard deviation is here estimated to be about 0 24 m a 1 in agreement with other arctic glaciers mass balance variability of this magnitude implies that the ice sheet can thicken or thin by several metres over 20 30 years without giving statistically significant evidence of non zero balance under present climate

late quaternary paleohydrology in the north american great plains inferred from the geochemistry of endogenic carbonate and fossil ostracodes from devils lake north dakota usa abstract devils lake north dakota is a closed basin lake in which water chemistry is responsive to hydrological changes making it a valuable resource for documenting paleoclimate conditions ostracode trace element and bulk carbonate geochemistry in a core are used to generate a 12 000 year record of salinity fluctuations the relative amounts of sr ca and ba in the bulk carbonate fraction can be linked mechanistically to changes in sediment mineralogy calcite aragonite and or solute chemistry whereas the elemental geochemistry of ostracode valves reflect solute chemistry associated minima in sr ca and maxima in mg ca in ostracode valves from the devils lake core may be due to aragonite mediation of sr chemistry during the precipitation of multiple mineral phases during more saline intervals the devils lake record can be divided into four hydrological periods on the basis of the geochemical proxies a 12 5 9 k y low salinity b 9 5 4 5 k y fluctuating saline conditions with a maximum at about 8 k y c 4 5 3 5 k y low salinity phase but probably not as fresh as at 12 5 9 k y d 3 5 k y present saline phase although generally less so than 9 5 4 5 k y however a large degree of variability characterizes the entire record suggesting the absence of long term climatic stability in this region

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

recent changes 1991 2010 in glacier mass balance and air temperature in the european alps we estimate temperature sensitivity of observed mass balance for glaciers in the alps to compare with our earlier estimates from modelling we treat 1961 1990 as our reference period and compare mass balance for 1991 2010 with this reference period there are eight alpine glaciers with long enough records the mean mass balance for the eight glaciers is close to zero for the reference period very negative for 1991 2010 and highly negative in the exceptionally warm year 2003 mass balance changes are compared with 1991 2010 temperature anomalies to give an average temperature sensitivity of about 0 7 0 2 m w e a 1 k 1 for the eight glaciers there is considerable variation between individual glaciers with higher sensitivity for western glaciers and lower sensitivity for more eastern glaciers temperature sensitivity for the eight glaciers is strongly correlated with the standard deviation of observed mass balance which from earlier work is known to be correlated with winter balance the mean temperature sensitivity for observed mass balance is in reasonable agreement with values from earlier models but changes in glacier hypsometry during 1991 2010 may have further increased observed mass loss

temperature reconstruction from the length fluctuations of small glaciers in the eastern alps northeastern italy in this study a linear model computing the air temperature fluctuations from the measured glacier snout fluctuations has been applied for the first time to three small glaciers in the western tauern alps eastern alps in the period 1929 2011 the considered glaciers with areas between 0 2 and 1 3 hbox km 2 are characterized by relevant time variations of their morphology length and slope the model requires the knowledge of two parameters the glacier climate sensitivity c s and the glacier response time tau both depending on the glacier morphological characteristics and on the precipitation applied to the glaciers assuming c s and tau as in the original formulation it underestimates the temperature increase of approx 1 8 circ hbox c derived over the whole period from the in situ data given the characteristics of these small glaciers these parameters have been recalibrated by means of a non linear least square regression using an independent set of glaciers their mean value is of about 210 m k and 3 8 years respectively with the recalibrated values of the new glacier climate sensitivity c s and response time tau the temperature fluctuations derived by the model reproduce well those obtained from the observed temperatures computed over the hydrological year with linear correlations between 0 8 and 0 9 the increase of the modeled mean temperature over the whole period fits in with that derived from observed temperature considering that the length fluctuations of these small glaciers affect significantly their slope and length we tested the impact in the model of a time dependent formulation of c s and tau the results indicate slight improvements both in the values of the correlation between the reconstructed and the observed temperature fluctuations and in the global temperature increase given the above value of climate sensitivity the large retreat of the small alpine glaciers threatens their survival within a few decades but the morphological changes in progress may counteract the glacier disappearance

positive degree day factors for ablation on the greenland ice sheet studied by energy balance modelling ice ablation is related to air temperature by the positive degree day factor variations of the positive degree day factor in west greenland are studied using an energy balance model to simulate ablation under different conditions degree day factors for simulated and measured ice ablation at nordbogletscher and qaman rssup sermia agree well with values around 8 mm d 1 c 1 degree day factors for snow are less than half those for ice energy balance modelling shows that degree day factors vary with summer mean temperature surface albedo and turbulence but there is only evidence of large positive degree day factors at lower temperatures and with low albedo 0 3 the greatest effect of albedo variations 0 3 0 7 is at lower temperatures while variations in turbulence have greater effect at higher temperatures current models may underestimate runoff from the greenland ice sheet by several tenths because they use a degree day factor for melting ice that is too small for the colder parts of the ice sheet i e the upper ablation area and the northerly margin

geochemistry of ostracode calcite part 2 the effects of water chemistry and seasonal temperature variation on candona rawsoni abstract reconstruction of lake paleochemistry from the isotope and trace element composition of fossil ostracodes requires an understanding of geochemical variations induced by the seasonality of shell formation monthly field collections of live candona rawsoni from two hyposaline lakes in the eastern dakotas reveal large variations in 18 o values 2 5 o and mg ca and sr ca ratios up to 35 among individual adults within the same assemblage because the measured variations in water chemistry were small the amplitude of ostracode 18 o and mg ca variations must result from seasonal temperature variation ostracode sr ca ratios which should be temperature independent shows strong positive covariance with shell mg ca these results imply that sr uptake in ostracode calcite increases with the mg content of the shell the partitioning coefficient for mg on the other hand appears to decreases at high values of mg ca in the host water the geochemical variability in the field collections indicates that c rawsoni populations are composed of multiple overlapping generations that attain maturity at different times many juveniles apparently undergo several molts in mid summer and persist as penultimate instars a 1 into the following spring geochemical analysis of late instar juvenile c rawsoni from lacustrine sedimentary records is likely to provide information on mid summer conditions large numbers of fossil ostracodes should be analyzed from each stratigraphic interval to eliminate seasonal noise from the paleochemistry records of temperate region lakes

analyses of recent observations of urumqi glacier no 1 chinese tianshan mountains as a reference glacier in the world glacier monitoring service urumqi glacier no 1 is the best observed glacier in china and provides the longest glaciological and climatological monitoring record a topographic survey was carried out in 2012 using the real time kinematic global positioning system glacier thickness was surveyed using ground penetrating radar in the same year in addition glacier terminus change and mass balance were surveyed every year until 2014 the glacier area was totally 1 59 km2 and the east and west branches occupied 1 02 and 0 57 km2 in 2012 respectively the glacier area had decreased by 0 31 km2 from 1962 to 2012 average ice thickness was 44 50 m in 2012 and had thinned by 0 34 m a 1 over 1981 2012 the shrinkage of this glacier is mainly due to climate warming especially summer temperature rise topographic characteristics resulted in a difference in terminus retreat thickness decrease and area shrinkage between the east and west branches of this glacier the analysis suggests that this glacier will possibly continue to shrink in future at least in a coming decade since it needs a response time to previous warming

homogenization of long term mass balance time series the re analysis of long term mass balance time series is important to provide bias corrected mass balance data for climate change impact studies a method to homogenize time series of compre hensive mass balance monitoring programmes is presented and applied to the nearly 50 year mass balance records of griesgletscher and silvrettagletscher switzerland using a distributed mass balance model in daily resolution we correct the mass balance data for varying observation dates direct point measurements are combined with independent geodetic mass changes a prerequisite for a thorough homogenization of mass balance records differences between mass balance evaluated in the hydro logical year or according to the measurement period and the stratigraphic system are analyzed and may be up to 0 5 m w e a 1 cumulative mass balance of both glaciers based on the glaciological method generally agrees well with geodetic mass change on the investigated glaciers however for silvretta gletscher a significant bias of 0 37 m w e a 1 has been detected and corrected for since 1994

multi component stable isotope records from late weichselian and early holocene lake sediments at imiolki poland palaeoclimatic and methodological implications late weichselian and early holocene climatic and environmental changes are inferred from stable carbon and oxygen isotope records obtained on bulk and biogenic carbonates from the sediment sequence of lake lednica western poland along with sediment and pollen stratigraphic data a wide range of carbonate components occurring in the sediments was analysed for delta c 13 and delta o 18 including shells of several gastropod species and the bivalve genus pisidium carapaces of the ostracod subfamily candoninae and oogonia of the aquatic macrophyte genus chara the development of catchment soils and the onset of authigenic carbonate production in response to the climatic amelioration during the late weichselian are clearly reflected by rising carbonate content distinct isotopic shifts in bulk carbonates and decreasing delta c 13 values of bulk organic matter in the sediments the gi 1 gs 1 the bolling allerod interstadial complex younger dryas stadial and the gs 1 preboreal transitions are marked by significant shifts in delta o 18 values of 2 3 parts per thousand as well as by distinct changes in carbonate content indicative of a decrease and a subsequent increase in mean annual temperature corresponding delta c 13 records reflect primarily changes in aquatic productivity with favourable conditions for phytoplankton and macrophytes during gi 1 and the preboreal resulting in persistent c 13 enrichment the younger dryas stadial is characterised by depletions in c 13 and o 18 with indications of a climatic tripartition consistent offsets in delta c 13 and delta o 18 between records obtained on specific carbonate components reflect vital effects in combination with seasonal characteristics and habitat preferences of the respective carbonate precipitating biota largely parallel first order variations in delta c 13 and delta o 18 of the different carbonate components demonstrate that individual isotope records may provide important palaeoclimatic information although more detailed reconstructions can be obtained from multi component analysis copyright c 2009 john wiley sons ltd

modelling the evolution of vadret da morteratsch switzerland since the little ice age and into the future we use a 3 d higher order glacier flow model for vadret da morteratsch engadin switzerland to simulate its strong retreat since the end of the little ice age lia and to project its future disintegration under a warming climate the flow model coupled to a 2 d energy balance model is initialized with the known maximum glacier extent during the lia and subsequently forced with mean monthly precipitation and temperature records to correctly reproduce the observed retreat of the glacier front for the period 1864 2010 additional mass balance perturbations are required to account for uncertainties in the initial state the mass balance model and climate variations not captured by the ambient meteorological records changes in glacier volume and area are in good agreement with additional information from historical topographic maps under constant 2001 10 climate conditions a strong retreat and mass loss continue and vadret da morteratsch disconnects from its main tributary vadret pers before 2020 the future glacier evolution is analysed in detail to understand the timing and rate of retreat and to assess the role of ice dynamics assuming a linearly increasing warming of 3 c by 2100 only isolated and largely stagnant ice patches remain at high elevation

lakewater paleothermometry from deep lake minnesota during the deglacial holocene transition from combined δ18o analyses of authigenic carbonate and aquatic cellulose abstract carbonate cellulose and bulk organic isotope data from varved sediments of deep lake minnesota provide a record of paleohydrologic and paleoclimatic change during the deglacial holocene transition from 12 000 to 7500 cal bp deep lake became enriched in 18 o in response to increased influence of maritime tropical moisture from the gulf of mexico between 12 000 and 9500 cal bp culminating in regional expansion of pinus and quercus and then again as a result of increased aridity with the establishment of more zonal circulation and prairie vegetation by 8500 cal bp summer lake water temperatures simultaneously increased during the deglacial holocene transition as suggested by decoupling of carbonate 18 o and cellulose inferred lake water 18 o values between 11 000 and 9500 cal bp and then declined briefly around 8600 cal bp possibly in response to the cooling event associated with the final drainage of glacial lakes agassiz and ojibway into the labrador sea although the carbonate cellulose paleothermometer generated unrealistically high values these can readily be explained by imposing kinetic effects that occur during rapid carbonate precipitation and conservative estimates of a seasonal lag effect in the synthesis of cellulose with respect to carbonate these new results suggest that climatic variations during the deglacial holocene transition in northwestern minnesota were driven mainly by changes in large scale atmospheric circulation and that lake agassiz played a comparatively minor role except during its final drainage

pleistocene paleoenvironmental evolution at continental middle latitude inferred from carbon and oxygen stable isotope analysis of ostracodes from the guadix baza basin granada se spain abstract a representative paleoenvironmental reconstruction of continental middle latitude from ca 2 my to the upper part of middle pleistocene 279 77 ky was obtained from the carbon and oxygen stable isotopes analyzed in ostracode shells cyprideis torosa recovered in the guadix baza basin se spain an intramontaneous closed depression filled by alluvial and lacustrine sediments this study was performed along a 356 m thick composite section dated previously by paleomagnetism and the amino acid racemization method 13c and 18o profiles reflected changes in temperature the evaporation infill ratio in the water bodies and the amount of rain 13c is also affected by changes in plant biomass periods with high 13c and 18o values are associated with warm and dry regimes and with less vegetation which in some cases coincide with the development of displacive gypsum crystals whereas low 13c and 18o values correlate with cold and humid episodes which cause more vegetation biomass and therefore increasing the input of isotopically light carbon intermediate 18o values are linked to temperate dry or humid episodes when they coincide with high or low 13c values respectively 86 paleoclimatic events were distinguished in the pleistocene record from the 13c and 18o profiles from both the statistical analysis of the geochemical data and the geological observations four cold and humid long periods low 18o and four warm and dry long periods high 18o were defined this differs with respect to the paleoclimatological behavior established for the northern hemisphere where during cold periods glacial no water was available while permafrost conditions persisted whereas in warm episodes interglacial higher precipitation rates occurred good correspondences between the guadix baza basin paleoclimatic record and a marine oxygen isotope sequence two continental cores and other long mediterranean paleoenvironmental records pollen sequences from israel were found which suggested that climate changes in the guadix baza basin were in tune with global climatic changes

glaciological conditions in seven contrasting regions estimated with the degree day model we apply the degree day model to seven glacial regions that offer contrasting conditions and are well documented in the world glacier inventory the regions are axel heiberg island in arctic canada svalbard northern scandinavia southern norway the alps the caucasus and new zealand we estimate the average equilibrium line altitude ela for each half degree latitude longitude grid square from the median elevations of glaciers within the square and we extrapolate temperature from the uea cru climate research unit of the university of east anglia gridded climatology using the degree day model we calculate annual accumulation at the ela equal to ablation at the ela and other quantities like summer mean temperature length of melt season balance gradients and the sensitivity of mass balance to temperature and or precipitation changes glaciers can be characterized on a scale from cold dry axel heiberg island to warm wet new zealand corresponding to the contrast between maritime and continental climates mass balance sensitivities to temperature and or precipitation changes are relatively small for dry cold climate and relatively high for warm wet climate we could extend the approach to other glacier regions but we note that there are large areas for which ela data are not available as they are still not covered by the world glacier inventory

static mass balance sensitivity of arctic glaciers and ice caps using a degree day approach the purpose of this study is to enhance our understanding of the response of glaciers to climate change global sea level is affected by changes in glacier ice volume and melt water from glaciers is a principal water source in many regions this study applies glacier mass balance modelling with varying complexity and spatial resolution ranging from individual glaciers to regional and global assessments of glacier mass losses glaciers located in maritime environments generally show considerably higher mass balance sensitivities than those in continental settings on average an assumed increase in annual precipitation of 10 tends to offset the effect of an annual temperature change of 1 k by roughly 20 two case studies at storglaciaren sweden and hofsjokull iceland involve model results of future mass balance change and glacier melt induced changes in runoff applying a temperature and precipitation scenario for iceland in 2050 results in increased total runoff from hofsjokull by roughly one third and results emphasize the role of the firn layer in delaying water flow through glaciers yielding a redistribution of discharge within the year based on a global gridded data set of glacierized area the sea level equivalent from all mountain glaciers and ice caps outside the ice sheets in greenland and antarctica during 1961 2004 caused by changes in temperature and precipitation is estimated to be 0 58 0 34 mm a 1 the mountain glaciers and ice caps around antarctica alone contribute almost 40 of the global estimate and hence their contribution is considerably larger than previously assumed

ordovician carboniferous tectono sedimentary evolution of the north nuratau region uzbekistan westernmost tien shan abstract the tien shan is a c 2500 km long orogenic belt of which the nuratau region of eastern uzbekistan forms the western part petrographical and field analysis of the ordovician carboniferous succession in the north nuratau region provided the basis for a reconstruction of the depositional settings along part of the northern margin of the alai continent and their evolution during the period of closure of the turkestan ocean which separated the alai and the kazakh kyrgyz continents initial sedimentation ordovician was broadly carbonate dominated although by mid late ordovician times siliciclastic input predominated in some areas these variations between clastic and carbonate dominated regions may have been related to tectonic activity within the alai continent carbonate sedimentation was reestablished in the wenlock with broad shelf systems forming along the continental margin volcanic activity in the early devonian records a period of tectonic instability and this was followed by the reestablishment of the carbonate mosaic albeit with a greater degree of instability as indicated by stratigraphic gaps than in the silurian this pattern extended up into the carboniferous culminating in backarc related magmatic activity final closure of the turkestan ocean involved significant folding and thrusting as well as a major change from compressional to strike slip movement

mid holocene drought and lake level change at elk lake clearwater county minnesota evidence from chirp seismic reflection data despite many studies of holocene paleoclimate records from small lakes in the mid continent of north america direct estimates of lake level changes associated with mid holocene aridity are rare varved sediments from elk lake clearwater county minnesota are among the best studied in terms of paleoenvironmental proxies yet the sedimentary architecture of those sediments has not been previously studied and the hydrological responses of the lake changes in level and volume are poorly known high resolution seismic reflection chirp profiles of elk lake reveal complex sedimentary basins in the lake a pattern of nearshore onlap of sediments onto older substrates and the focusing of sediments into several deep basins biogenic gas obscures sediments in the deepest parts of the basins but beneath the rest of the lake a three part holocene sequence is clear the transitions between these parts are correlated with lithological changes defined in earlier core studies sediments of the modern stage are

holocene climate in the northern great plains inferred from sediment stratigraphy stable isotopes carbonate geochemistry diatoms and pollen at moon lake north dakota abstract seismic stratigraphy sedimentary facies pollen stratigraphy diatom inferred salinity stable isotope 18 o and 13 c and chemical composition sr ca and mg ca of authigenic carbonates from moon lake cores provide a congruent holocene record of effective moisture for the eastern northern great plains between 11 700 and 9500 14 c yr b p the climate was cool and moist a gradual decrease in effective moisture occurred between 9500 and 7100 14 c yr b p a change at about 7100 14 c yr b p inaugurated the most arid period during the holocene between 7100 and 4000 14 c yr b p three arid phases occurred at 6600 6200 14 c yr b p 5400 5200 14 c yr b p and 4800 4600 14 c yr b p effective moisture generally increased after 4000 14 c yr b p but periods of low effective moisture occurred between 2900 2800 14 c yr b p and 1200 800 14 c yr b p the data also suggest high climatic variability during the last few centuries despite the overall congruence the biological diatom sedimentological isotopic and chemical proxies were occassionally out of phase at these times the evaporative process was not the only control of lake water chemical and isotopic composition

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

chemical and particle size evidence for addition of fine dust to soils of the midwestern united states significant long term atmospheric dust additions to soils are well documented in many parts of the world but not in the midwestern united states we investigated elemental mass fluxes associated with soil development in late wisconsinan loess in illinois and minnesota using zr as a stable index element positive mass fluxes of al fe and ti can most plausibly be explained by additions to these soils of fine far traveled dust with higher al zr fe zr and ti zr ratios than the coarser locally derived loess high resolution particle size analyses support this explanation the proposed dust influx will complicate efforts to quantify weathering processes in these soils far traveled dust influx could have occurred simultaneously with the final phase of local loess deposition and or later in the holocene depending on the timing of dust influx many other soils of the region may have been affected by it

paleolimnological records of climatic change in north america lacustrine fossil records provide long time series of data on limnological and climatic conditions these data are useful for establishing natural patterns of climate variability and for generating testable hypotheses about atmospheric circulation and climate ecosystem linkages shoreline features can indicate past lake level fluctuations that may reflect changes in moisture balance but often these records are discontinuous and are evidence of only extreme conditions the organisms geochemistry and sedimentology of lake sediments may provide a more continuous sequence of direct and indirect lake climate interactions in the past the most clearly interpretable paleolirnnological records of climatic change are those that use several lines of evidence to corroborate a climatic hypothesis and are from sites near an ecotone or in regions of extreme climate in all cases hydrologic setting mediates a lake s response to climate and must be considered in interpreting sedimentary sequences discussion of the impact of recent and future climatic changes necessitates a baseline against which the magnitude of observed or predicted changes can be measured commonly we look to recent history as a reference point for comparison however the landscape of recent decades or in some cases even centuries has been altered greatly by human activities thus to determine whether recent or future climatic change is unique or unusual we need long natural preanthropogenic time series against which observed or predicted climatic states and variability can be compared paleolimnological archives are a tool for looking at environmental patterns prior to anthropogenic impact and show a range of climatic states far greater than those documented by written records former strand lines of pluvial lakes bonneville and lahontan in the western u s for example testify to moisture extremes unsurpassed in recent centuries or even millennia in addition one can us the paleolimnological record as an independent climatic proxy against which patterns and rates of terrestrial response to climatic change can be compared here i present a broad overview of paleoclimatic reconstruction in north america from lacustrine records with a focus on the late quaternary the review is limited to climatic inference from paleolirnnological records a term i use in a restrictive sense to refer to records of past lake states physical biological and geochemical as opposed to records of past stream hydrology e g ely et al 1993 knox 1993 or terrestrial conditions i summarize paleolimnological tools available for reconstruction of past climate the capabilities and limitations of these tools

reconstruction of hydrological changes and response to effective moisture variations from north central usa lake sediments abstract ratios of the stable isotopes of oxygen and carbon in benthic ostracodes and marl from cores taken from two lakes in north central minnesota reflect holocene hydrological and vegetation changes oxygen isotopes show that williams and shingobee lakes located in the same watershed but with different positions along a hydrologic gradient were connected before 9 8 ka as part of a larger lake lake willobee from 9 8 7 7 ka the level of lake willobee fell as a result of glacial retreat and increasing evaporation leaving small separated basins further decreases in lake level after 7 7 ka due to increasing aridity triggered the inflow of ground water in williams lake at about 7 ka and in shingobee lake at about 5 ka after 4 ka effective moisture increased the carbon isotope record reflects changes in vegetation with higher 13 c values during the prairie period 7 7 4 ka and lower values during preceding and succeeding forest periods the differences in timing of hydrological events show that the biotic and geochemical response of the lakes to climate variations is mediated by their hydrologic systems the response may be strongly spatially heterogeneous and can result in contrasting information from geochemical and biotic proxies from the same paleorecord

low sea level rise projections from mountain glaciers and icecaps under global warming the mean sea level has been projected to rise in the 21st century as a result of global warming such projections of sea level change depend on estimated future greenhouse emissions and on differing models but model average results from a mid range scenario a1b suggests a 0 387 m rise by 2100 refs 1 2 the largest contributions to sea level rise are estimated to come from thermal expansion 0 288 m and the melting of mountain glaciers and icecaps 0 106 m with smaller inputs from greenland 0 024 m and antarctica 0 074 m here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise excluding those in greenland and antarctica we provide the first separate assessment of melt contributions from mountain glaciers and icecaps as well as an improved treatment of volume shrinkage we find that icecaps melt more slowly than mountain glaciers whose area declines rapidly in the 21st century making glaciers a limiting source for ice melt using two climate models we project sea level rise due to melting of mountain glaciers and icecaps to be 0 046 and 0 051 m by 2100 about half that of previous projections

physical and chemical predictors of diatom dissolution in freshwater and saline lake sediments in north america and west greenland diatom dissolution in surface sediment samples from two regional lake datasets in the northern great plains ngp n 5 64 and west greenland n 5 40 is assessed using a morphological approach categorizing valves during routine diatom analysis two dissolution indices are derived to parameterize diatom dissolution and when compared between two analysts in a blind test show good correspondence and are closely correlated to diatom fragmentation we explore the relationships between hydrochemical and physical lake parameters including meromixis on dissolution within both lake regions using multivariate methods and modeled with logistic regression salinity is the sole significant predictor of dissolution in west greenland but salinity carbonate concentration co3 22 and meromixis are significant predictors in the ngp limnological parameters explain 40 59 of variation in dissolution in both regions for both dissolution indices the dissolution index methodology is applied to a short sediment sequence from devils lake north dakota where diatom inferred salinity inferences can be compared with a historical record of salinity fluctuations over the 20th century absolute errors in paleosalinity estimates are strongly correlated with diatom dissolution with salinity overestimated in 8 out of 11 poorly preserved samples preservation does appear to constrain the reliability of the inferred paleosalinity at this site and may also affect the quality of diatom based paleoenvironmental inferences elsewhere including estimates of biogenic silica where preservation state is often not explicitly considered

mid holocene climate in northern minnesota abstract study of holocene ostracodes and diatoms from elk lake in north central minnesota indicates that the local climate of the mid holocene can be subdivided into three intervals throughout interval 1 ca 7800 to 6700 yr b p climate was colder and much drier than today during intervals 2 and 3 ca 6700 to 4000 yr b p average mean annual air temperatures approached the modern mean 3 7 c but warm summers persisted throughout interval 2 whereas during interval 3 warm summers fell into discrete episodes furthermore average mean annual precipitation was about 85 and 90 of modern during intervals 2 and 3 respectively transition times between the principal intervals were less than 50 yr the expected effects of a retreating laurentide ice sheet that initially maintained a winter style circulation followed by transitional climate states and finally a near modern circulation pattern may explain these local climatic events

centennial eolian cyclicity in the great plains usa a dominant climate pattern of wind transport over the past 4000 years proxy evidence at decadal resolution from late holocene sediments from pickerel lake northeastern south dakota shows distinct centennial cycles 400e700 years in magnetic susceptibility contents of carbonate organic carbon and major elements abundance in ostracodes and d 18 o and d 13 c values in calcite proxies indicate cyclic changes in eolian input productivity and temperature maxima in magnetic susceptibility are accompanied by maxima in aluminum and iron mass accumulation rates mars and in abundances of the ostracode fabaeformiscandona rawsoni this indicates variable windy and dry conditions with westerly wind dominance including during the medieval climate anomaly maxima in carbonates organic carbon phosphorous and high d 13 c values of endogenic calcite indicate moister and less windy periods with increased lake productivity including during the little ice age and alternate with maxima of eolian transport times of the maunder sporer and wolf sunspot minima are characterized by maxima in d 18 o values and aluminum mars and minima in d 13 c values and organic carbon content we interpret these lake conditions during sunspot minima to indicate decreases in lake surface water temperatures of up to 4e5 c associated with decreases in epilimnetic productivity during

influence of terrestrial vegetation on sediment forming processes in kettle lakes of west central minnesota the composition magnetic characteristics and pollen content of sediments from two small kettle lakes near the prairie forest border in west central minnesota were used to infer changes in terrestrial vegetation shoreline erosion eolian inputs carbonate deposition and aquatic productivity several important changes in sediment stratigraphy coincide closely with changes in the terrestrial pollen assemblage accumulation rates of organic inorganic and carbonate sediment fractions as well as the concentration of magnetic particulates increased abruptly as prairie replaced pine forest and decreased gradually throughout the subsequent transitions to oak scrub and later mixed woodland results suggest that by its mediation of wind exposure local vegetation may affect 1 influx of eolian particulates 2 erosion of shorelines 3 water circulation and 4 carbonate equilibria in addition low rates of accumulation of organic matter and increased humidicity during periods of conifer vegetation suggest that humic matter leached from forest soils may influence lake water chemistry and reduce productivity changes in lake level caused by differential rates of evapotranspiration of the various vegetation types conifer forest deciduous hardwood forest brush scrub and prairie could not be detected sediment forming processes can therefore be altered by changes in local terrestrial vegetation through several mechanisms that are independent of changes in lake level

100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation thirty new 100 year records of glacier surface mass balance accumulation and melt in the swiss alps are presented the time series are based on a comprehensive set of field data and distributed modeling and provide insights into the glacier climate linkage considerable mass loss over the 20th century is evident for all glaciers but rates differ strongly glacier mass loss shows multidecadal variations and was particularly rapid in the 1940s and since the 1980s mass balance is significantly anticorrelated to the atlantic multidecadal oscillation amo index assumed to be linked to thermohaline ocean circulation we show that north atlantic variability had a recognizable impact on glacier changes in the swiss alps for at least 250 years citation huss m r hock a bauder and m funk 2010 100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation geophys res lett 37 l10501 doi

altitudinal gradient of mass balance sensitivity to climatic change from 18 years of observations on glacier d argentiere france assessment of the contribution of small glaciers to sea level rise or the reconstruction of past glacial mass balance requires knowledge of mass balance sensitivity to climatic variations the aim of this paper is to clarify this relation the mass balance fluctuations analyzed from measurements on glacier d argentiere mont blanc massif france between 1850 and 2700 m a s l were compared with climatic variations at a nearby meteorological station statistical study of the data shows that 1 the annual mass balance fluctuations are dependent on elevation and 2 the mass balance sensitivity to temperature decreases with altitude and diverges from current model results consequences of a temperature variation of 1 c for global volume variations are significant a simple calculation on glacier des bossons mont blanc massif france shows that the sensitivity from the model can lead to volume variations twice as high as results compatible with our observations

estimating equilibrium line altitude ela from glacier inventory data a glacier s most fundamental altitude is the equilibrium line altitude ela because it divides the glacier into ablation and accumulation areas the best parameterization of the ela for glacier inventory is the balanced budget ela we discuss direct estimation of balanced budget ela from mass balance data for individual glaciers and indirect estimation of balanced budget ela from simple topographic parameters available from the world glacier inventory wgi i e the area median and maximum and minimum altitudes mass balance and ela for individual glaciers are usually strongly correlated and we calculate balanced budget ela from the regression equation linking the two we then compare balanced budget ela with area median and mid range altitudes for the 94 glaciers for which we have all the necessary data the different ela estimates agree well enough 82 to 125 m to describe geographical variations in ela and for application of glacier climate models to glacier inventory data mid range and area median altitudes are already available for tens of thousands of glaciers in the current wgi and should be evaluated in future inventories

early holocene change in atmospheric circulation in the northern great plains an upstream view of the 8 2 ka cold event elk lake in northwestern minnesota contains numerous proxy records of climatic and environmental change contained in varved sediments with annual resolution for the last 10 000 years these proxies show that about 8200 calendar years ago 8 2 cal ka 7300 radiocarbon years elk lake went froma well stratified lake that was wind protected in a boreal forest to a wellmixed lake in open prairie savanna receiving northwesterly wind blown dust probably from the dry floor of lake agassiz this change in climate marks the initiation of the widely recognized mid holocene altithermal in central north america the coincidence of this change with the so called 8 2 cal ka cold event recognized in ice core and other records fromthe circum north atlantic and thought by some to be caused by catastrophic discharge of freshwater from proglacial lakes agassiz and ojibway suggests that the two events might be related our interpretation of the elk lake proxy records and of other records from less accurately dated sites suggests that change in climate over north america was the result of a fundamental change in atmospheric circulation in response to marked changes in the relative proportions of land water and especially glacial ice in north america during the early holocene this change in circulation probably post dates the final drainage of proglacial lakes along the southern margin of the laurentide ice sheet and may have produced a minor perturbation in climate over greenland that resulted in a brief cold pulse detected in ice cores r 2002 elsevier science ltd all rights reserved

common climatic signal from glaciers in the european alps over the last 50 years conventional glacier wide mass balances are commonly used to study the effect of climate forcing on glacier melt unfortunately the glacier wide mass balances are also influenced by the glacier s dynamic response investigations on the effects of climate forcing on glaciers can be largely improved by analyzing point mass balances using a statistical model we have found that 52 of the year to year deviations in the point mass balances of six glaciers distributed across the entire european alps can be attributed to a common variability point mass balance changes reveal remarkable regional consistencies reaching 80 for glaciers less than 10 km apart compared to the steady state conditions of the 1962 1982 period the surface mass balance changes are 0 85 m water equivalent w e a 1 for 1983 2002 and 1 63 m w e a 1 for 2003 2013 this indicates a clear and regionally consistent acceleration of mass loss over recent decades over the entire european alps

a petrological and fluid inclusion study of magnetite scheelite skarn mineralization at kara northwestern tasmania implications for ore genesis abstract the kara magnetite scheelite deposit is located about 40 km south of burnie in northwestern tasmania the deposit consists of a number of orebodies and the total mineable reserves are 1 7 mt of magnetite at 30 fe and 0 3 mt of scheelite at 0 52 wo3 the major orebodies at kara are hosted by the ordovician gordon limestone at the southern end of the devonian housetop granite adjacent to the granite or separated from it by the ordovician moina sandstone at least four paragenetic stages of skarn formation and ore deposition have been recognized stage i clinopyroxene garnet vesuvianite wollastonite quartz scheelite stage ii garnet vesuvianite magnetite scheelite apatite quartz stage iii magnetite amphibole epidote fluorite quartz chlorite garnet vesuvianite scheelite carbonate pyrite clinopyroxene and stage iv hematite fluorite calcite quartz fluid inclusions in clinopyroxene from stage i homogenize at 460 620 c mode 520 c stage ii gave homogenization temperatures of 349 578 c mode 500 c from scheelite and 360 570 c mode 500 c from vesuvianite the stage i clinopyroxene gave a salinity range of 10 0 12 0 equiv wt nacl with only one low value of 2 0 equiv wt nacl the stage ii mineral assemblages also showed moderate salinities of 12 0 and 17 8 equiv wt nacl from scheelite and vesuvianite fluid inclusions in quartz scheelite calcite and fluorite from the main scheelite mineralization phase stage iii homogenize at 230 360 c with a mode at 300 c and salinity varies from 0 2 to 19 8 equiv wt nacl the mineral paragenetic and fluid inclusion studies indicate that magnetite scheelite mineralization at kara was formed as a proximal skarn assemblage in carbonate host the skarn formation and ore deposition occurred in stages starting with prograde anhydrous clinopyroxene garnet metasomatism at relatively high temperatures 500 c this early assemblage was replaced by the subsequent retrograde deposition of hydrous mineral phases e g amphibole epidote and chlorite as temperatures decreased to 300 c or less deposition of scheelite predominantly occurred in association with hydrous minerals e g amphibole in stage iii the high temperature and moderate to high salinity ore fluids in early anhydrous skarn formation stages i and ii are consistent with fluids of magmatic origin in comparison the lower temperature and variable salinity from high 19 8 equiv wt nacl to as low as 0 2 equiv wt nacl in stage iii suggests a possible involvement of low salinity meteoric waters mixing with high salinity fluids originating from the nearby granite in the later hydrous skarn and ore formation

climatic and morphological controls on diachronous postglacial lake and river valley evolution in the area of last glaciation northern poland abstract the wda river valley in northern poland is a polygenetic valley located in a former subglacial meltwater channel that after ice sheet retreat hosted separate and then interconnected lake basins subsequently replaced by a river in one part of the river system an abandoned lateglacial valley is found this dry valley is a unique feature in the area located within the limit of the scandinavian ice sheet during the last glaciation in the central european lowland we investigated lacustrine and fluvial sediments and landforms in the valley and applied palynological analysis combined with radiocarbon dating to reconstruct the valley evolution from the early period of river inception in the lateglacial through the formation of lakes during the pleistocene holocene transition up to the establishment of a modern river system in the early holocene three coeval processes were identified 1 formation of lake basins in the subglacial channel connected by a river 2 erosion of the river bed between the lakes and 3 sediment deposition at the mouths of the channels in the lake basins first generating delta fans and eventually filling the lakes entirely the valley formation was associated with diachronous melting of dead ice blocks buried in the subglacial channel controlled by the capacity of the hydrological system to evacuate the meltwater most of the lake basins in the study area were formed during the bolling allerod period but one section of the subglacial channel not affected by thermokarst processes survived protected by dead ice blocks throughout the entire lateglacial accelerated dead ice decay at the beginning of the holocene triggered widespread lowering of the base level which caused lake disappearance and the formation of the modern river system the processes reconstructed in the central section of the wda river indicate a highly dynamic and diachronous river valley development during the lateglacial and early holocene whereby the valley formation was interwoven with the formation of lake basins within the valley triggered by melting of dead ice blocks in the substratum

ice ablation as evidence of climate change in the alps over the 20th century 1 over fifty years of cumulative annual mass balance data for several glaciers in the alps shows similar fluctuations which seem to provide evidence of a common climatic signal separate winter and summer mass balance measurements from the claridenfirn glacier in switzerland since 1914 and the sarennes glacier france since 1949 show that 1 the annual mass balance is primarily driven by the summer mass balance term and 2 melting rate variations with time are very similar for these two glaciers located 290 km apart the increase in the ablation rate of 0 5 cm w e day 1 between the two periods 1954 1981 and 1982 2002 over these two glaciers corresponds to a 20 wm 2 rise in the energy flux at the glacier surface these results suggest that a common summer melting rate change may have affected the alps as a whole detailed observations on the sarennes glacier show that the origin of this strong increase in summer ablation since 1982 is not only a rise in the summer melting rate but also an increase in the ablation period during the months of september and october

sensitivity of mass balance of five swiss glaciers to temperature changes assessed by tuning a degree day model a degree day model is used to assess the sensitivity of the mass balance of five swiss glaciers to temperature changes the model uses temperature data extrapolated from nearby climate stations and is tuned by varying precipitation to make the model fit the observed distribution of mass balance with altitude once the model is tuned the effect of temperature change is simulated by recalculating the mass balance with the same parameters as before but with a temperature increase of 1 c throughout the year the largest mass balance changes involving increased ablation of 1 m w e a 1 c 1 occur at the snout with a progressively smaller increase with altitude the area averaged sensitivities for the five glaciers are 0 7 to 0 9 m w e a 1 c 1 if annual precipitation also increased by 20 it would partly offset the effect of the 1 c higher temperatures but could not compensate for it

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

the lacustrine carbon cycle as illuminated by the waters and sediments of two hydrologically distinct headwater lakes in north central minnesota u s a abstract the accumulation rates of caco3 and organic carbon oc in lake sediments are delicately balanced between production in the epilimnion and destruction in the hypolimnion the cycling of these two forms of carbon makes a carbon pump that greatly affects the biogeochemical cycles of other elements to further understand these biogeochemical dynamics the lakes streams and wetlands of the shingobee river headwater area of north central minnesota have been subjected to intensive hydrologic and biogeochemical studies williams lake situated close to the highest point in the regional flow system is hydrologically closed with no surface inlet or outlet and ground water and precipitation as the only sources of water shingobee lake situated at the lowest point in the regional flow system has the shingobee river as an inlet and outlet the surface waters of both lakes are oversaturated and the bottom waters undersaturated with respect to caco3 during the summer the small amount of caco3 that is precipitated in the epilimnion of williams lake during the summer is dissolved in the undersaturated hypolimnion and sediments with the result that no caco3 is incorporated into the profundal surface sediments because of the high phytoplankton productivity of shingobee lake sufficient caco3 is produced in the epilimnion that large amounts survive the corrosive hypolimnion and sediments and an average of 46 wt accumulates in surface sediments another consequence of higher phytoplankton productivity in shingobee lake is that the hypolimnion becomes oxygen deficient within a month after overturn in both the spring and fall because of reducing conditions that develop in the hypolimnion of shingobee lake high concentrations of dissolved fe and mn accumulate there during summer stratification precipitation of fe and mn oxyhydroxides during periods of fall and spring overturn results in high concentrations of fe and mn in surface sediments in williams lake high concentrations of fe and mn do not build up in the hypolimnion the concentration of caco3 is about 80 wt in lower holocene sediments of both lakes the lower holocene sediments in both lakes also contain high concentrations of fe and mn and the lower holocene sediments of shingobee are laminated the waters of both lakes had identical values of 13c and 18o during the early holocene but the waters of williams lake evolved during the early holocene increasing about 10 in both 13c and 18o deposits of lacustrine marl occur as much as seven meters above the present elevation of williams lake the highest of the two lakes taken together these observations suggest that the lakes were once connected to form a larger lake called lake willobee with a hypolimnion that was anoxic at least seasonally

degree day glacier mass balance modelling with applications to glaciers in iceland norway and greenland a degree day glacier mass balance model is applied to three glaciers in iceland norway and greenland for which detailed mass balance measurements are available over a period of several years model results are in good agreement with measured variations in the mass balance with elevation over the time periods considered for each glacier in addition the model explains 60 80 of the year to year variance in the elevation averaged summer season mass balance measurements on the glaciers using a single parameter set for each glacier the increase in ablation on the glaciers due to a warming of 2 c is predicted to range from about 1 m w e year 1 at the highest elevations to about 2 5 m w e year 1 at the lowest elevations predicted changes in the winter balance measured between fixed date are relatively small except at the lowest elevations on the icelandic and norwegian glaciers where the winter balance is significantly reduced equilibrium line altitudes are raised by 200 300 m on the icelandic and norwegian glaciers except at the highest elevations the winter balance of the icelandic and norwegian glaciers is predicted to decrease even if the warming is accompanied by a 10 increase in the precipitation no firm evidence of a climate related variation in the degree day factors or in the temperature lapse rate on the same glacier could be found the model furthermore reproduces large variations in the mass balance with elevation and from year to year on each glacier using the same parameter set we assume therefore that these parameters will not change significantly for the climate scenarios considered here

formation of anhydrous and hydrous skarn in cu au ore deposits by magmatic fluids most skarn ore deposits are characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet and pyroxene forms from relatively high temperature hypersaline liquid a later retrograde stage with hydrous minerals such as epidote amphibole and chlorite plus sulfide ore minerals forms from lower temperature lower salinity fluids these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from two different skarn systems one being part of the world s largest cu au resource stable isotope compositions of anhydrous and hydrous alteration minerals from both deposits indicate a magmatic source for both the prograde and retrograde stages 18o averages 5 0 per mil for garnet range 3 4 7 2 6 5 per mil for pyroxene 4 3 8 2 and 7 1 per mil for amphibole 4 3 8 7 the d values of late amphibole are more complex with magmatic values 77 to 78 for one deposit and both magmatic and lighter values for another deposit that could be explained either by magmatic degassing or by limited mixing with meteoric water we conclude that the differences in fluid composition prograde versus retrograde stages resulted from a magmatic fluid that intersected its solvus during the early stage creating vapor and hypersaline liquid whereas in the later stage this magmatic fluid did not intersect its solvus because it followed a different cooling path this late low salinity liquid only boiled once its vapor pressure curve was reached causing sulfide ore to precipitate during the retrograde stage

statistical modelling of the surface mass balance variability of the morteratsch glacier switzerland strong control of early melting season meteorological conditions in this study we analyse a 15 year long time series of surface mass balance smb measurements performed between 2001 and 2016 in the ablation zone of the morteratsch glacier complex engadine switzerland for a better understanding of the smb variability and its causes multiple linear regressions analyses are performed with temperature and precipitation series from nearby meteorological stations up to 85 of the observed smb variance can be explained by the mean may june july temperature and the total precipitation from october to march a new method is presented where the contribution of each month s individual temperature and precipitation to the smb can be examined in a total sample of 2 24 16 8 million combinations more than 90 of the observed smb can be explained with particular combinations in which the may june july temperature is the most recurrent followed by october temperature the role of precipitation is less pronounced but autumn winter and spring precipitation are always more important than summer precipitation our results indicate that the length of the ice ablation season is of larger importance than its intensity to explain year to year variations the widely used june july august temperature index may not always be the best option to describe smb variability through statistical correlation

using structure from motion to create glacier dems and orthoimagery from historical terrestrial and oblique aerial imagery increased resolution and availability of remote sensing products and advancements in small scale aerial drone systems allows observations of glacial changes at unprecedented levels of detail software developments such as structure from motion sfm now allow users an easy and efficient method to generate three dimensional 3d models and orthoimages from aerial or terrestrial datasets while these advancements show promise for current and future glacier monitoring many regions still suffer a lack of observations from earlier time periods we report on the use of sfm to extract spatial information from various historic imagery sources we focus on three geographic regions the european alps high arctic norway and the nepal himalayas we used terrestrial field photographs from 1896 high oblique aerial photographs from 1936 and aerial handheld photographs from 1978 to generate digital elevation models dems and orthophotos of the rhone glacier broggerhalvoya and the lower khumbu glacier respectively our analysis shows that applying sfm to historic imagery can generate high quality models using only ground control points limited camera orientation information was largely reproduced using self calibrated model data using these data we calculated mean ground sampling distances across each site which demonstrates the high potential resolution of resulting models vertical errors for our models are 5 4 m 5 2 m and 3 3 m differencing shows similar patterns of thinning at lower rhone european alps and broggerhalvoya norway glaciers which have mean thinning rates of 0 31 m a 1 1896 2010 to 0 86 m a 1 1936 2010 respectively on these clean ice glaciers thinning is highest in the terminus region and decreasing up glacier in contrast to these glaciers uneven topography exposed ice cliffs and debris cover on the khumbu glacier create a highly variable spatial distribution of thinning the mean thinning rate for the khumbu study area was found to be 0 54 0 9 m a 1 1978 2015

century scale paleoclimatic reconstruction from moon lake a closed basin lake in the northern great plains estimates of past lake water salinity from fossil diatom assemblages were used to infer past climatic conditions at moon lake a climatically sensitive site in the northern great plains a good correspondence between diatom inferred salinity and historical records of mean annual precipitation minus evapotranspiration p et strongly suggests that the sedimentary record from moon lake can be used to reconstruct past climatic conditions century scale analysis of the holocene diatom record indicates four major hydrological periods an early holocene transition from an open freshwater system to a closed saline system by 7300 b p which corresponds with a transition from spruce forest to deciduous parkland to prairie and indicates a major shift from wet to dry climate a mid holocene period of high salinity from 7300 to 4700 b p indicating low effective moisture p et a transitional period of high salinity from 4700 to 2200 b p characterized by poor diatom preservation and a late holocene period of variable lower salinity during the past 2 200 yr indicating fluctuations in effective moisture

hydrologic variation in the northern great plains during the last two millennia abstract reconstructions of lake water salinity at decadal resolution for the last 2000 yr are compared among three lakes in north dakota to infer regional patterns of drought the intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change at one lake diatom inferred salinity and lake water mg ca inferred from ostracode shell chemistry are coherent both in terms of direction and magnitude of change indicating that each is a robust technique for reconstructing lake water chemistry the data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity suggesting shifts between dry and moist periods long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent thus indicating times when drought was more persistent than in the 20th century both the medieval period and little ice age were hydrologically complex and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long term patterns differences among the three sites may be attributed to variation in local hydrology and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data

ground water processes controlling a prairie lake s response to middle holocene drought lake response to climate forcing is commonly regarded as being controlled by within lake processes we present a case from the northern great plains in which holocene drought response recorded in lake sediments was determined by changes in chemical characteristics of source ground water middle holocene ostracode assemblages were dominated by halophylic limnocythere staplini indicating increased lake water salinity yet the oxygen isotope values in this period decreased by 2 to 3 contrary to expectations of evaporative dominance we infer from these proxy records and ground water flow model results that the paleoclimatic record in the lake was mediated by changes in ground water catchment area and by reduction in evapotranspiration accompanying desiccation of peripheral lake basins

magmatic hydrothermal evolution at the lyangar redox intermediate tungsten molybdenum skarn deposit western uzbekistan tien shan insights from igneous petrology hydrothermal alteration and fluid inclusion study abstract the lyangar w mo skarn deposit is situated in a metallogenic belt of w mo cu mo w au and au deposits and is related to an early permian multiphase monzodiorite granodiorite granite leucogranite pluton that was emplaced in a tectonic domain with possible ancient continental crust the latter coupled with an inferred ascent of hot asthenospheric material has defined an enrichment in mo and fluorine together with w and au to form a distinct metallogenic assemblage in a post collisional environment the parental moderately to high k transitional metaluminous to peraluminous weakly oxidized weakly reduced ilmenite titanite series granitoids are accompanied by hydrothermal alteration and mineralization that formed in redox intermediate environment the deposit incorporates prograde and retrograde pyroxene and garnet skarns composed of hedenbergitic pyroxene and grossular to almandine spessartine rich garnet respectively fluorite is present in the retrograde skarn together with scheelite and sulfides the latter including most abundant pyrrhotite and molybdenite hydrosilicate amphibole epidote chlorite quartz locally with albite sulfides and scheelite assemblage has limited development phyllic quartz sericite fe carbonate locally with albite fluorite scheelite and sulfides also bi and au minerals alteration assemblage partially overprints altered skarns and extends over much larger areas overall the deposit represents a superposition of the early w mo mineralization related to retrograde skarn and hydrosilicate alteration and the late au w cu bi mineralization in phyllic alteration assemblages prograde and retrograde skarns were formed from dominantly magnesian sodic chloride moderately saline 11 7 13 9 wt to 8 6 10 5 wt nacl eq high pressure 1500 to 1350 bars hot aqueous fluids that were followed by moderately saline 12 3 14 5 wt nacl eq ca rich lower pressure 600 bars fluids during deposition of most scheelite hydrosilicate propylitic assemblages were formed from boiling fluids at the temperatures of 380 430 c and pressures of 600 300 bars whereas phyllic alteration assemblages from boiling carbonic aqueous low salinity fluids at the temperatures of 300 320 c and pressures of 1000 bars 18oh2o values range from 7 8 to 8 6 for retrograde skarn and from 6 6 to 7 0 for phyllic alteration whereas 13cco2 from 3 3 to 0 5 for retrograde skarn and from 5 5 to 4 5 for phyllic alteration 34s increases from retrograde skarn 34s 2 0 to 2 3 to phyllic alteration 34s 4 3 to 4 6 stages

a method to estimate the ice volume and ice thickness distribution of alpine glaciers sound knowledge of the ice volume and ice thickness distribution of a glacier is essential for many glaciological applications however direct measurements of ice thickness are laborious not feasible everywhere and necessarily restricted to a small number of glaciers in this paper we present a method to estimate the ice thickness distribution and the total ice volume of alpine glaciers this method is based on glacier mass turnover and principles of ice flow mechanics the required input data are the glacier surface topography the glacier outline and a set of borders delineating different ice flow catchments three parameters describe the distribution of the apparent mass balance which is defined as the difference between the glacier surface mass balance and the rate of ice thickness change and two parameters define the ice flow dynamics the method was developed and validated on four alpine glaciers located in switzerland for which the bedrock topography is partially known from radio echo soundings the ice thickness along 82 cross profiles can be reproduced with an average deviation of about 25 between the calculated and the measured ice thickness the cross sectional areas differ by less than 20 on average this shows the potential of the method for estimating the ice thickness distribution of alpine glaciers without the use of direct measurements

holocene environmental and climatic change in the northern great plains as recorded in the geochemistry of sediments in pickerel lake south dakota the sediments in pickerel lake northeastern south dakota provide a continuous record of climatic and environmental change for the last 12000 yr sediments deposited between 12 and 6 ka radiocarbon show extreme variations in composition oxygen and carbon isotopic composition of bulk carbonate carbon isotopic composition of organic matter and magnetic susceptibility these variations re ect changes in sources of moisture regional vegetation types precipitation evaporation balance ground and surface water in ux water residence time erosion lake productivity water level and water temperature the total carbonate content of late pleistocene sediments steadily increased from 20 at the base of the core to as much as 80 in sediments deposited between 11 and 9 ka by about 8 ka the total carbonate content of the sediments had declined to about 40 where it remained with little variation for the past 8 kyr suggesting relatively stable conditions there are marked increases in values of d13c and d18 oi n bulk carbonate and d13c of organic matter in sediments deposited between 10 and 6 ka as evaporation increased and the vegetation in the watershed changed from forest to prairie this shift toward more 18o enriched carbonate may also re ect a change in source or seasonality of precipitation during this early holocene interval the organic carbon oc content of the sediments remained relatively low 2 3 but then increased rapidly to 4 5 between 7 and 6 ka re ecting the rapid transition to a prairie lake the oc content uctuates slightly between 4 and 6 in sediments deposited over the past 6 kyr like oc and total carbonate most variables measured show little variation in the 13 m of sediment deposited over the past 6 kyr particularly when compared with early holocene variations although the magnetic susceptibility of this upper 13 m of sediment is generally low 10 si units the upper six meters of the section is marked by striking 1 m cycles ca 400 500 yr periodicity in susceptibility these cycles are interpreted as being due to variations in the in ux of eolian detrital clastic material century scale cyclic variations in di erent proxy variables for aridity and eolian activity from sediments deposited over the past 2000 yr in other lakes in the northern great plains as well as in sand dune activity suggest that aridity cycles were the dominant feature of late holocene climate of the northern great plains 2000 elsevier

the response of two icelandic glaciers to climatic warming computed with a degree day glacier mass balance model coupled to a dynamic glacier model a degree day glacier mass balance model is coupled to a dynamic glacier model for temperate glaciers the model is calibrated for two outlet glaciers from the hofsjokull ice cap in central iceland it is forced with a climate scenario that has recently been defined for the nordic countries for the purpose of outlining the hydrological consequences of future greenhouse warming the scenario for iceland specifies a warming rate of 0 25 c per decade in mid summer and 0 35 c per decade in mid winter with a sinusoidal variation through the year the volume of the glaciers is predicted to decrease by approximately 40 over the next century and the glaciers essentially disappear during the next 200 years runoff from the area that is presently covered by the glaciers is predicted to increase by approximately 0 5 m a 1 30 years from now due to the reduction in the volume of the glaciers the runoff increase reaches a flat maximum of 0 5 2 0 m a 1 100 150 years from now and levels off after that the predicted runoff increase leads to a significant increase in the discharge of rivers fed by meltwater from the outlet glaciers of the ice cap and may have important consequences for the operation and planning of hydroelectric power plants in iceland

the chemical composition of lakes in the north central united states1 abstruct lake waters of the north central u s a arc classified into five groups based on increasing specific conductivity and changes in ionic composition from east to west from wisconsin through minnesota to north and south dakota the most dilute group of waters has specific condllctivities 29 pmhos cm at 25 c the most concentrated group has specific conductances that range from 7 000 to 73 000 pmhos as conductivity increases all major ions increase but there is a shift in cation dominance from ca2 to mg2 to na and in anion dominance from hc03 to sod2 this shift partly reflects a westward increase in climatic aridity and partly a westward sequence of glacial drifts from noncalcareous to calcareous and thence to calcareous with abundant sulfllr bearing minerals levels of ph k cl f b and sio also show a distinct westward increase concentrations of no and mn increase from east to west but the trend is less distinct concentrations of fe vary widely without any trend over the range of conductivity color mostly from dissolved organic matter is controlled chiefly by lake depth except for lakes with cxtcnsive peatlands in their drainage basins

interdecadal variability of degree day factors on vestari hagafellsjokull langjokull iceland and the importance of threshold air temperatures the skill of degree day glacier melt models is highly dependent on the choice of degree day factor ddf which is often assumed to remain constant in time here we explore the validity of this assumption in a changing climate for two locations on vestari hagafellsjokull 1979 2012 using a surface energy balance seb approach that isolates the effect of changes in the prevailing weather on the ddf at lower elevation we observe stable ddf during the period of study however at higher elevation ddf is noted to be more variable and a statistically significant downward trend is observed this is found to result from an inappropriate threshold air temperature t crit from which to initiate the positive degree day sum and is removed by setting t crit to 1 83 c rather than the usual value of 0 c used in degree day melt models the stationarity of ddf once t crit is adjusted contradicts previous research and lends support to the use of constant ddf for projecting future glacier melt optimizing t crit also improves the skill of melt simulations at our study sites this research thus highlights the importance of t crit for both melt model performance and the evaluation of ddf stationarity in a changing climate

early holocene limnological and climatic variability in the northern great plains information on the timing and direction of climatic and environmental change on a millennial scale exists for many regions of north america whereas little is known about decadal to centennial scale variability here we present a high resolution analysis of diatom inferred salinity from a site in the northern great plains to reconstruct multidecadal and centennial scale climatic patterns during the early holocene the diatominferred salinity indicates a transition from fresh to highly saline conditions between c 13 400 and 7700 cal yr bp which suggests a major shift in climate from wet to dry conditions the overall trend toward increasing salinity is interrupted by several freshwater intervals between c 9800 and 7950 cal yr bp which may be the result of an increase in the frequency of monsoonal flow from the gulf of mexico the early holocene is considered to be a time of rapid change in climate and vegetation within the holocene although rates of change in the moon lake diatom assemblages were hi

climate sensitivity of a high precipitation glacier in new zealand the sensitivity of glaciers to climatic change is key information in assessing the response and sea level implications of projected future warming new zealand glaciers are important globally as an example of how maritime glaciers will contribute to sea level rise a spatially distributed energy balance model is applied to brewster glacier new zealand in order to calculate glacier mass balance run off and sensitivity to climate change the model successfully simulates four annual mass balance cycles close to half 52 of the energy available for melt on the glacier is supplied by turbulent heat fluxes with radiation less important except during the winter model sensitivity to temperature change is one of the largest reported on earth at 2 0 m w e a 1 8c 1 in contrast a 50 change in precipitation is required to offset the mass balance change resulting from a 18c temperature change meltwater run off sensitivity is also very high increasing 60 with a 18c warming the extreme sensitivity of mass balance to temperature change suggests that significant ice loss will occur with even moderate climate warming

a review of the tagus river tufa deposits central spain age and palaeoenvironmental record here we determined the aminostratigraphy and aminochronology of tufa deposits located in central spain associated w i t h the tagus river and some o f its tributaries the henares dulce cifuentes ruguilla trabaque escabas and guadiela rivers w e used aspartic acid and glutamic acid racemization ratios obtained from the ostracod herpetocypris reptans tufa accumulations were found to be of different origins those in t h e henares cifuentes and ruguilla rivers are of paludal origin w h i l e those in t h e dulce and tagus rivers are o f fluvial origin a generally g o o d correspondence was found b e t w e e n the age o f the deposits and the position of the terraces above the current thalweg however the geomorphological evolution of the henares cifuentes and ruguilla rivers infilling of pre existing valleys has produced deposits of distinct ages at the same elevation above the current river thalweg and sometimes older tufas are located b e l ow younger ones we distinguished eight main tufa deposition episodes these occurred predominantly during even marine isotopic stages mis at 4 0 6 90 mis 11 2 6 4 68 mis 7e 189 4 0 mis 7a 130 27 mis 6 5e 101 2 5 mis 5c 3 2 10 mis 3 1 4 4 mis 1 a n d 6 2 mis l k a these results are in agreement w i t h the dating of similar deposits from nearby areas and other zones of s p a i n a n d europe the tufa stable isotope compositions were similar to other examples in central and southern spain a n d their plot falls in the same field as other lowland european stream tufas o x y g e n stable isotopes were influenced mainly b y temperature a n d rainfall the 51 3c values indicated a major effect o f soil derived carbon rather t h a n carbon from the catchment area but moderated in each tributary b y evaporation flow regime and biological effects photosynthesis

derivation of melt factors from glacier mass balance records in western canada melt factors for snow k s and ice k i were derived from specific mass balance data and regionally interpolated daily air temperature series at nine glaciers in the western cordillera of canada fitted k s and k i were relatively consistent across the region with mean values standard deviations of 3 04 0 38 and 4 59 0 59 mm d 1 c 1 respectively the interannual variability of melt factors was investigated for two long term datasets calculated annually snow and ice melt factors were relatively stable from year to year standard deviations for snowmelt factors were 0 48 17 and 0 42 18 at peyto and place glaciers respectively while standard deviations of ice melt factors were 1 17 25 and 0 81 14 while fitted values of k s are comparable to those presented in previous observational and modeling studies fitted k i are substantially and consistently lower across the region fitted melt factors were sensitive to the choice of lapse rate used in the air temperature interpolation melt factors fitted to mass balance data from a single site place glacier provided reasonable summer balance predictions at most other sites representing both maritime and continental climates although there was a tendency for under prediction at several sites the combination of regionally interpolated air temperatures and a degree day model appears capable of generating first order estimates of regional summer balance which can provide a benchmark against which to judge the predictive ability of more complex e g energy balance models applied at a regional scale mass balance sensitivity analyses indicate that a temperature increase of 1 k will increase summer ablation in the region by 0 51 m w e a 1 on average

conventional versus reference surface mass balance glacier surface mass balance evaluated over the actual glacier geometry depends not only on climatic variations but also on the dynamic adjustment of glacier geometry therefore it has been proposed that reference surface balances calculated over a constant glacier hypsometry are better suited for climatic interpretation here we present a comparison of 82 year modelled time series 1926 2008 of conventional and reference surface balance for 36 swiss glaciers over this time period the investigated glaciers have lost 22 of their area and ice surface elevation close to the current glacier terminus has decreased by 78 m on average conventional balance in the last decade at 0 91 m w e a 1 is 0 14 m w e a 1 less negative than the reference surface balance about half of the negative stabilizing feedback on mass balance due to glacier terminus retreat is compensated by more negative mass balances due to surface lowering short term climatic variability is clearly reflected in the conventional mass balance series however the magnitude of the long term negative trend is underestimated compared to that found in the reference surface balance series both conventional and reference surface specific balances show large spatial variability among the 36 glaciers

20th century climate change inferred from four long term point observations of seasonal mass balance four long term time series of seasonal mass balance observations all starting in 1914 have been compiled for two stakes on claridenfirn and one stake on grosser aletschgletscher and silvrettagletscher switzerland these data represent the longest records of mass balance worldwide a mass balance model based on the temperature index approach is used to correct field data for varying observation dates and data gaps and to separate accumulation and ablation the homogenized continuous 93 year time series cover most of the 20th century and enable us to investigate temporal regional and altitudinal variability in mass balance and changes in the climatic forcing on glaciers a high altitude site shows summer balance trends opposite to those at three stakes located near the equilibrium line since 1975 melt rates have increased by 10 10 a 1 periods of enhanced climatic forcing are detected 1943 53 and 1987 2007 the energy consumed for melt was higher in the 1940s despite lower air temperatures compared to the years since 1987 we find evidence for a change in the glacier surface heat budget which has important implications for the long term stability of degree day factors in empirical temperature index modelling

human responses to middle holocene altithermal climates on the north american great plains abstract the climate of the great plains during the middle holocene varied considerably but overall it was marked by a north south gradient of increasingly warmer and drier conditions with a reduction in effective moisture surface water and resource abundance and an increase in resource patchiness sediment weathering erosion and aeolian activity pronounced drought conditions were most evident on the southern high plains understanding the human responses to middle holocene climates is complicated by a lack of archaeological data which is partly a result of geomorphic processes that removed or deeply buried sites of this age and by the varying adaptive responses of hunter gatherers during this period on the southern high plains where drought was most severe surface and groundwater sources dried and bison populations were diminished prompting substantial adaptive changes including local abandonment well digging to tap underground water and a widening of the diet breadth to incorporate higher cost lower return seed and plant resources sites of this age on the central and northern plains also show a possible increase in diet breadth with the incorporation of plant foods in the diet and perhaps changes in settlement mobility including possible shift into higher elevation areas or mapping on to extant rivers and springs but linking those changes to middle holocene drought is less straightforward

mass balance of rhonegletscher during 1882 83 1986 87 les bilans de masse effectues sur le glacier des sources du rhone alpes suisses pendant differentes periodes 1884 85 1908 09 1979 80 et 1981 82 sont presentes

comparison of multiple proxy records of holocene environments in the midwestern united states we compare four emerging approaches to reconstructing holocene vegetation and climate from south of the glacial border in northeastern iowa united states pollen plant macrofossils carbon isotopic 13 c values from alluvial organic matter and carbon isotopic values in stalagmites from a nearby cave all show similar paleovegetational and paleoclimatic trends during the holocene pollen and plant macrofossils show a rapid change from forest to prairie about 6000 cal yr b p followed by a return of oaks to a presumably savanna like community about 3500 cal yr b p the 13 c values in alluvial organic matter and the percentage of c 4 plants both increase ca 6300 cal yr b p and then decrease in the last 3500 years in the cave 13 c values rise beginning at 6000 cal yr b p to a broad peak ca 4500 to 3000 cal yr b p and decrease thereafter pollen and plant macrofossils record the composition of the vegetation that produced the isotopic signals and verify c 3 c 4 interpretations based on the isotopic records we demonstrate that these methods are complementary but that any single method will provide an accurate reconstruction of past environments