a 5500 year oxygen isotope record of high arctic environmental change from southern spitsbergen the oxygen isotope composition of chironomid head capsules in a sediment core spanning the past 5500 years from lake svartvatnet in southern spitsbergen was used to reconstruct the oxygen isotope composition of lake water 18olw and local precipitation the 18olw values display shifts from the baseline variability consistent with the timing of recognized historical climatic episodes such as the roman warm period the dark ages cold period and the little ice age the highest values of the record ca 3 above modern 18olw values occur at ca 1900 1800 cal yr bp three negative excursions increasing in intensity toward the present at 3400 3200 1250 1100 and 350 50 cal yr bp are tentatively linked to roughly synchronous episodes of increased glacier activity and general cold spells around the northern north atlantic their manifestation in the svartvatnet 18olw record not only testify to the sensitivity and potential of high arctic lacustrine 18ochir records in tracking terrestrial climate ev

preservation of glaciochemical time series in snow and ice from the penny ice cap baffin island a detailed investigation of major ion concentrations of snow and ice in the summit region of penny ice cap pic was performed to determine the effects of summer melt on the glaciochemical time series while ion migration due to meltwater percolation makes it difficult to confidently count annual layers in the glaciochemical profiles time series of these parameters do show good structure and a strong one year spectral component suggesting that annual to biannual signals are preserved in pic glaciochemical records

a record of holocene summer climate from a canadian high arctic ice core melt layers in ice cores are formed by melting on the snow pack surface which produces water that percolates down and refreezes in the colder snow layers below melt layers are distinguished by their bubble texture because more ice forms in the snow pack in warm summers than in cool summers the changing concentration with depth of melt layers in snow pits1 2 and ice cores3 5 is an indicator of past summer climate here we report on studies of melt layers in two canadian high arctic surface to bedrock ice cores although changes in elevation of the drill site owing to isostatic depression and uplift may contribute up to 40 of the total climatic signal recorded in the melt layers we interpret their varying concentrations in terms of changing summer temperatures over the past 10 000 years the warmest summers occurred 8 10 kyr ago and the coldest only 150 years ago the summers over the past 100 years have been the warmest for more than 1 000 years but are still not as warm as those of the early holocene the melt layer record is in broad agreement with geological records of glacier retreat during the holocene6 8 indicating that these data also contain information of regional significance

isotope thermometry in melt affected ice cores 1 a statistically significant relationship is observed between stable water isotopes 18o and melt amounts in a melt affected firn core ssummit taken from the prince of wales icefield ellesmere island canada by contrast a low melt firn core taken from a higher elevation higher latitude location on the same icefield shows no relationship between these variables we interpret this as evidence for meltwater induced isotopic enrichment at ssummit a percent melt based correction slope is applied to isotopic values from ssummit uncorrected and corrected temperature records derived from the raw and corrected 18o values are compared to bias corrected temperature data from the ncep reanalysis improvements are observed in the isotopic reconstruction of ssummit annual precipitation weighted temperatures when we correct for meltwater enrichment with a reduction from 0 6 c to 0 0 c in the mean annual error and a decrease in root mean square error from 1 8 c to 1 6 c the correction factor appears to overcorrect isotopic modification during high melt years such as 1999 during which ssummit experienced nearly 70 more melt than the average from 1975 to 2000 excluding 1999 data from the correction analysis results in a slight reduction in mean absolute error from 1 4 c to 1 3 c these results suggest that melt induced isotopic modification cannot be corrected in very high melt years

115 year ice core data from akademii nauk ice cap severnaya zemlya high resolution record of eurasian arctic climate change from 1999 to 2001 a 724 m deep ice core was drilled on akademii nauk ice cap severnaya zemlya to gain high resolution proxy data from the central russian arctic despite strong summertime meltwater percolation this ice core provides valuable information on the regional climate and environmental history we present data of stable water isotopes melt layer content and major ions from the uppermost 57 m of this core covering the period 1883 1998 dating was achieved by counting seasonal isotopic cycles and using reference horizons multi annual 18 o values reflect eurasian sub arctic and arctic surface air temperature variations we found strong correlations to instrumental temperature data from some stations e g r 0 62 for vardo northern norway the 18 o values show pronounced 20th century temperature changes with a strong rise about 1920 and the absolute temperature maximum in the 1930s a recent decrease in the deuterium excess time series indicates an increasing role of the kara sea as a regional moisture source from the multi annual ion variations we deduced decreasing sea salt aerosol trends in the 20th century as reflected by sodium and chloride whereas sulphate and nitrate are strongly affected by anthropogenic pollution

seismic depth imaging of iron oxide deposits and their host rocks in the ludvika mining area of central sweden abstract the development of cost effective and environmentally acceptable geophysical methods for the exploration of mineral resources is a challenging task seismic methods have the potential to delineate the mineral deposits at greater depths with sufficiently high resolution in hardrock environments which typically host the majority of metallic mineral deposits seismic depth imaging workflows are challenged by steeply dipping structures strong heterogeneity and the related wavefield scattering in the overburden as well as the often limited signal to noise ratio of the acquired data in this study we have developed a workflow for imaging a major iron oxide deposit at its accurate position in depth domain while simultaneously characterizing the near surface glacial overburden including surrounding structures like crossing faults at high resolution our workflow has successfully been showcased on a 2d surface seismic legacy data set from the ludvika mining area in central sweden acquired in 2016 we applied focusing prestack depth imaging techniques to obtain a clear and well resolved image of the mineralization down to over 1000 m depth in order to account for the shallow low velocity layer within the depth imaging algorithm we carefully derived a migration velocity model through an integrative approach this comprised the incorporation of the tomographic near surface model the extension of the velocities down to the main reflectors based on borehole information and conventional semblance analysis in the final step the evaluation and update of the velocities by investigation of common image gathers for the main target reflectors were used although for our data set the reflections from the mineralization show a strong coherency and continuity in the seismic section reflective structures in a hardrock environment are typically less continuous in order to image the internal structure of the mineralization and decipher the surrounding structures we applied the concept of reflection image spectroscopy to the data which allows the imaging of wavelength specific characteristics within the reflective body as a result conjugate crossing faults around the mineralization can directly be imaged in a low frequency band while the internal structure was obtained within the high frequency bands

glaciochemistry of polar ice cores a review human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world the study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past this paper deals with the chemistry of polar ice focused on the soluble mineral na nh4 k ca mg h f cl no3 so4 and h2o2 and organic methanesulfonate ch3so3 formate hcoo acetate ch3coo and formaldehyde hcho species and their interpretation in terms of past atmospheric composition aerosols and water soluble gaseous species we discuss ice core dating the difficulties connected with trace measurements and the significance of the ionic composition of snow we examine temporal from the last decades back to the last climatic cycle and spatial including examples from coastal as well as central areas of greenland and antarctica variations in the ionic budget of the precipitation and evaluate ice core studies in terms of the chemical composition of our past atmosphere we review 1 how greenland and antarctic ice cores that span the last few centuries have provided information on the impact of human activities and 2 how the chemistry of deep ice cores provides information on various past natural phenomena such as climatic variations glacial interglacial changes el nino volcanic eruptions and large boreal forest fires

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

reconstruction of three centuries of annual accumulation rates based on the record of stable isotopes of water from lomonosovfonna svalbard we use the upper 81 in of the record of stable isotopes of water from a 122 in long ice core from lomonosovfonna central spitsbergen svalbard to construct an ice core chronology and the annual accumulation rates over the icefield the isotope cycles are counted in the ice core record using a model that neglects short wavelength and low amplitude cycles we find approximately the same number of delta 18 o cycles as years between known reference horizons and assume these cycles represent annual cycles testing the validity of this assumption using cycles in deltad shows that both records give similar numbers of cycles using the delta 18 o chronology and decompressing the accumulation records using the nye flow model we calculate the annual accumulation for the ice core site back to ad 1715 we find that the average accumulation rate from 1715 to 1950 was on average 0 30 in w e accumulation rates increased about 25 during the later part of the 20th century to an average of 0 41 in w e for the period 1950 97 the accumulation rates show highly significant 2 1 and 21 year periodicities which gives credibility to our time scale

lomonosovfonna and holtedahlfonna ice cores reveal east west disparities of the spitsbergen environment since ad 1700 an ice core extracted from holtedahlfonna ice cap western spitsbergen record spanning the period 1700 2005 was analyzed for major ions the leading empirical orthogonal function eof component is correlated with an index of summer melt log na mg 2 from 1850 and shows that almost 50 of the variance can be attributed to seasonal melting since the beginning of the industrial revolution the holtedahlfonna d 18 o value is less negative than in the more easterly lomonosovfonna ice core suggesting that moist air masses originate from a closer source most likely the greenland sea during the little ice age the lower methanesulfonic acid msa concentration and msa non sea salt sulfate fraction are consistent with the greenland sea as the main source for biogenic ions in the ice cores both the melt index and the msa fraction suggest that the early decades of the 18th century may have exhibited the coldest summers of the last 300 years in svalbard ammonium concentrations rise from 1880 which may result from the warming of the greenland sea or from zonal differences in atmospheric pollution transport over svalbard during winter neutralized aerosols are trapped within the tropospheric inversion layer which is usually weaker over open seas than over sea ice placing holtedahlfonna within the inversion more frequently than lomonosovfonna

stratigraphic analysis of an ice core from the prince of wales icefield ellesmere island arctic canada using digital image analysis high resolution density past summer warmth reconstruction and melt effect on ice core solid conductivity 1 high resolution 1 mm stratigraphic information was derived from digital image analysis of an ice core from the prince of wales pow icefield central ellesmere island canada following careful image processing a profile of ice core transmitted light was derived from the greyscale images and used to reconstruct high resolution density variations for the unfractured sections of the core images were further classified into infiltration and glacier ice using an automatic thresholding procedure and were converted to a high resolution melt percentage index the mean annual melt percentage over the last 580 years was 9 and melting occurred in 8 years out of 10 melting obliterated most of the original depositional sequence and seasonal density cycles were mostly unrecognizable the ice core solid conductivity was greater and more variable in melt features than in glacier ice owing to washout of strong acids by meltwater elution and chemical enrichment upon refreezing this hindered the identification of acid volcanic layers and further compromised dating by annual layer counting comparison of the melt record with those from other arctic ice caps shows that the melt temperature relationship on pow icefield is site specific we speculate that this is due to the peculiar position of the icefield which rests on the periphery of the baffin bay maritime climate zone and to the proximity of the north open water polynya which controls snow accumulation variability on the icefield and affects the melt percentage index

areal distribution of the oxygen isotope ratio in greenland mean values of the oxygen isotope ratio relative to standard mean ocean water 8 180 in 0 reported for 46 sites on the greenland ice sheet are compiled together with data on mean annual surface temperature latitude 8180 elevation and mean annual shor test distance to the open ocean denoted by the 10 sea ice concentration boundary stepwise regression analyses with 8180 as the dependent variable define two robust models in the forward mode at the 99 9 confidence level only temperature enters the model in the backward mode at the 95 con fidence level only temperature latitude and distance to the open ocean remain in the model inversions of the models on the basis of 160 gridpoint locations 100 km apart in the area delimited by the surface equilibrium line produce four contoured distributions of b iho two distributions are based on the bivariate model and two on the multivariate modcl the sccond distribution for each model is obtained substituting mean annual surfa ce tempe ratu re values obtained from the nim bus 7 temperature humidity infrared radiometer thir database all four distribu tions are considered valid and differences between them are evaluated using contoured anomaly maps it is suggested that the inversion o the multivariate model using thir data pro ides the more reliable pattern for stu dies of atmospheric advection or for the derivation of ice flow adjustments for 81ho series obt ained from deep core or ablation zone sites

some comments on climatic reconstructions from ice cores drilled in areas of high melt poor consideration has been given in many arctic circum polar ice core studies to the effect of summer snow melt on chemistry stable isotope concentrations and time scales many of these corps are drilled close to the firn line where melt is intense some come from below the firn line where accumulation is solely in the form of super imposed ice in all cases seasonal signals are reduced or removed and in some time gaps develop during periods of excessive melting which situate the drill site in the ablation zone consequently cross correlations of assumed synchronous events among the cores are invalid so that time scales along the same cores differ between authors by factors of over 2 many so called climatic signals are imaginary rather than real by reference to published analyses of cores from the superimposed ice zone on devon ice cap koerner 1970 and meighen ice cap koerner and paterson 1974 it is shown how melt affects all the normally well established ice core proxies and leads to their misinterpretation despite these limitations the cores can give valuable low resolution records for all or part of the holocene they show that the thermal maximum in the circum polar arctic occurred in the early holocene this maximum effected negative balances on all the ice caps and removed the smaller ones cooler conditions in the second half of the holocene have caused the regrowth of these same ice caps

a new ice core record from lomonosovfonna svalbard viewing the 1920 97 data in relation to present climate and environmental conditions in 1997 a 121 m ice core was retrieved from lomonosovfonna the highest ice field in spitsbergen svalbard 1250 m a s l radar measurements indicate an ice depth of 126 5 m and borehole temperature measurements show that the ice is below the melting point high resolution sampling of major ions oxygen isotopes and deuterium has been performed on the core and the results from the uppermost 36 rn suggest that quasi annual signals are preserved the 1963 radioactive layer is situated at 18 5 18 95 m giving a mean annual accumulation of 0 36 m we for the period 1963 96 the upper 36 rn of the ice core was dated back to 1920 by counting layers provided by the seasonal variations of the ions in addition to using a constant accumulation rate with thinning by pure shear according to nye 1963 the stratigraphy does not seem to have been obliterated by meltwater percolation in contrast to most previous core sites on svalbard the anthropogenic influence on the svalbard environment is illustrated by increased levels of sulphate nitrate and acidity both nitrate and sulphate levels started to increase in the late 1940s remained high until the late 1980s and have decreased during the last 15 years the records of delta o 18 msa methanesulphonic acid and melt features along the core agree with the temperature record from longycarbyen and the sea ice record from the barents sea at a multi year resolution suggesting that this ice core reflects local climatic conditions

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

the potential of rotary wing uav based magnetic surveys for mineral exploration a case study from central sweden abstract unmanned aerial vehicle uav based geophysical surveys are attractive for land mineral exploration and are gradually opening extraordinary opportunities in providing high resolution definition of geologic structures and for direct targeting of mineral deposits there are however challenges such as electromagnetic noise from the uav limited load capacity and short flight times if these are overcome there will be a new era in using uav based geophysical systems for mineral exploration and for a number of mining related purposes in this study we have tested the potential of rotary wing uav systems given their flight flexibility and robustness for direct targeting of iron oxide deposits in central sweden a walking mode high precision overhauser magnetometer was reassembled so that it could be lifted by the rotary wing system successful backyard tests were performed but during the real experiment several issues related to high uav noise level and extreme magnetic field from the mineraliza

cross profile seismic data acquisition imaging and modeling of iron oxide deposits a case study from blotberget south central sweden cross profile seismic data acquisition imaging and modeling of iron oxide deposits a case study from blotberget south central sweden

reconstruction of the historical temperature trend from measurements in a medium length borehole on the lomonosovfonna plateau svalbard a medium length ice core was drilled at the ice divide on the lomonosovfonna plateau 1230 m a s l svalbard in may1997 as part of this project temperature measurements were performed in the 120 m deep borehole at this site the ice thickness based on radar measurements is 126 5 m and the mean annual accumulation rate is 380 kg m 3 the measurements over the 15 120 m depth interval show a nearly isothermal profile with a mean value of 2 8 c and a standard deviation of 0 2 c the measurements reveal a temperature minimum at approximately 70 m depth and a temperature gradient of 0 011 0 004 c m 1 near the bottom the temperature minimum and relatively low temperature gradient cannot be explained in terms of a steady state climate numerical calculations with a simple onedimensional diffusion advection model show that the temperature increased at a maximum rate of 0 02 0 025 k a 1 over the last 100 years the total temperature increase amounting to 2 0 3 0 k forcing the model with the observed record at svalbard airport revealed that in the 19th century the surface temperature was at most 2 5 k lower and that the instrumental observations started during a period with temperatures comparable to the end of the 19th century the data are of particular interest for historical simulations since often no other temperature data are available in polar areas

laboratory study of the migration of methane sulphonate in firn two 10cm lengths of firn core from the dyer plateau 700 3l s 65 0l w antarctic peninsula were used to carry out a laboratory experiment to investigate the migration of methane sulphonate the anion of methane sulphonie acid msa in natural fim each length was cut vertically into tour pieces and a dopant solution containing cl no3 so4 2 f and msa pipetted onto the top of three sections the fourth being kept as a blank the doped sections were stored vertically with the doped end uppermost for r months at a range of temperatures nominally 5 10 and 22 c before subsampling at 1em resolution and analysis by ion chromatography the two firn lengths were treated identically and the results were consistent profiles of the doped fim sections showed that cl no3 so4 2 remained in the uppermost subsample although the no3 concentrations were variable compared to the blank the yo profile shows slightly elevated concentrations in the second sample down compared to the blank at temperatures of l0 c and above the msa showed higher concentrations in the second third and fourth samples down at 10 c and above which indicates that some percolated downwards from its original position at the top of the core this experiment shows that msa is mobile in warm fim even over a short period of time we propose that the mechanism tor the mobility of msa in natural fim is via liquid msa drainage though we cannot yet discount vapour phase transport

determination of firn density in ice cores using image analysis this study presents a simple and inexpensive method for deriving a high resolution density proxy record for the firn part of an ice core using digital images the image data have better resolution and are less sensitive to core quality than is density derived through dielectric profiling dep simple image analysis is thus suitable to derive a density proxy record in the firn section of ice cores drilled in the percolation or wet snow zone and to better interpret the results of a dep record the images may be used as a permanent record when evaluating other types of ice core data suggestions are provided to improve data quality and decrease post processing time of the image analysis in future studies

seasonal evolution of aerosol stratigraphy in urumqi glacier no 1 percolation zone eastern tien shan china the processes involved in the evolution of vertical profiles of mg 2 c a 2 and microparticle concentrations as well as their seasonal variation in surface snow were studied by weekly sampling from september 2003 to september 2004 of a snow pit on urumqi glacier no 1 eastern tien shan china the development of the microparticle and mg 2 and ca 2 stratigraphy in the snow pit is closely related to the physical development of the snow firn pack the sampling site is located at 4130 m a s l in the percolation zone of the glacier and in addition to the effects of sublimation and wind erosion melting plays a crucial role in both the physical and chemical evolution processes during the winter soluble aerosol concentrations in the surface layers are altered slightly by sublimation and wind erosion and the concentrations are further modified as the wet season begins in late april in contrast soluble aerosol stratigraphy in the deeper layers remains relatively unchanged through the winter in early summer as melting occurs in the upper part of the snow firn pack meltwater carries chemical species to different depths in the underlying snow firn layers such that at the end of the ablation season all of the surface cations might be leached out from the upper layers in addition the possible source of calcium and magnesium is discussed in this paper

reflection seismic investigations in the dannemora area central sweden insights into the geometry of polyphase deformation zones and magnetite skarn deposits the bergslagen region is one of the most ore prospective districts in sweden presented here are results from two nearly 25 km long reflection seismic profiles crossing this region in the dannemora

svalbard summer melting continentality and sea ice extent from the lomonosovfonna ice core we develop a continentality proxy 1600 1930 based on amplitudes of the annual signal in oxygen isotopes in an ice core we show via modeling that by using 5 and 15 year average amplitudes the effects of diffusion and varying layer thickness can be minimized such that amplitudes then reflect real seasonal changes in 18o under the influence of melt a model of chemical fractionation in ice based on differing elution rates for pairs of ions is developed as a proxy for summer melt 1130 1990 the best pairs are sodium with magnesium and potassium with chloride the continentality and melt proxies are validated against twentieth century instrumental records and longer historical climate proxies in addition to summer temperature the melt proxy also appears to reflect sea ice extent likely as a result of sodium chloride fractionation in the oceanic sea ice margin source area that is dependent on winter temperatures we show that the climate history they depict is consistent with what we see from isotopic paleothermometry continentality was greatest during the little ice age but decreased around 1870 20 30 years before the rise in temperatures indicated by the 18o profile the degree of summer melt was significantly larger during the period 1130 1300 than in the 1990s

determination of timing and location of water movement and ice layer formation by temperature measurements in sub freezing snow measurements of temperature in snow along a vertical profile during the onset of spring melting are used to calculate spatial and temporal temperature gradients and terms of the conduction equation with an internal energy production term are calculated heat transfer information is combined with stratigraphic observations made during melting and allow detailed determination of the timing and location of heterogeneous water movement and of refreezing internal energy production is interpreted as latent heat of refreezing of percolated meltwater times and locations of flow and refreezing of meltwater are calculated and compared to stratigraphic observations of layering and changes in density and liquid water content sequences of melt piping layering and refreezing seen in calculations and in stratigraphy demonstrate retarded flow at fine to coarse transitions flow along such transitions and refreezing at the transitions to form ice layers downslope flow is also observed in the absence of an impermeable horizon to redirect flow from the vertical

formation of ice layers by infiltration and refreezing of meltwater melt layer frequency and magnitude in polar and sub polar ice cores have been interpreted as measures of past summer temperature and calibrations have been proposed relating frequency of occurrence of ice layers in ice cores to past summer temperatures but observations in the percolation facies in greenland and an analysis of the combined processes of meltwater infiltration and refreezing of water in snow indicate that in addition to unusually high rates of meltwater input formation of ice layers will also be facilitated by unusually cold initial conditions or early onset of melt uniform warming of both summer and winter conditions has the opposite effect and suppresses ice layer formation in favor of uniform wetting and refreezing of the snowpack numerical modeling of infiltration and refreezing at a stratigraphic fine to coarse transition allows quantification of the effects of significant parameters initial temperature grain size and density contrast across the stratigraphic transition water input rate and minimum impermeable layer thickness calculations are made to distinguish threshold values of parameters at which infiltration progresses faster than refreezing resulting in a break through of water across the stratigraphic transition from values leading to the formation of an ice layer when refreezing progresses faster than infiltration

separation of melting and environmental signals in an ice core with seasonal melt we examine the impact of melt water percolation on the soluble ion chemical record from the lomonosovfonna ice core principle component analysis shows that melting produces only simple changes bet

sulfate source inventories from a svalbard ice core record spanning the industrial revolution 1 the 800 year sulfate record from lomonosovfonna was analyzed by a novel multiple linear regression algorithm that attempts to explain sulfate variability in terms of other chemical species measured in the core and sulfur emission inventories we use three statistical approaches to determine sulfate sources we examine trends using singular spectrum analysis with confidence intervals finding clear evidence that anthropogenic sources are important but not dominant we use cross wavelet coherence to examine significant multidecadal covariance in terrestrial sulfate but our main tool is multiple regression analysis of the sulfate dependency on other ions and anthropogenic emission inventories models are fitted in a moving time window of typically 50 years length explaining 80 of the sulfate variance a suite of model predictors are examined and the variation in relative magnitudes of the model coefficients along the core can be used to infer variations in the strength of various sulfate sources we observe large changes in sulfate sources at the end of the little ice age associated with changes in barents sea marine productivity changes in north atlantic sulfate input and a long lasting period of disturbance caused by the large laki volcanic eruption modeling sulfur emission inventories shows that western europe contributes about 15 of the sulfate budget with essentially no input from other regions in contrast with predictions from global circulation models incorporating sulfur chemistry multidecadal cycles are mainly confined to the little ice age and most likely associated with increased storminess and enhanced deposition of both marine aerosol and biogenic sulfate from the atlantic ocean the model residuals do not show a normal distribution but display very large spikes unexpectedly those significant at the 99 level can be closely matched to major volcanic eruptions using independent dating methods the 20th century sulfate in the core is inventoried as sea salt 15 terrestrial 10 volcanic 5 10 western european anthropogenic 10 25 barents sea biogenic 20 40 and atlantic biogenic 10 15

comparison of techniques for dating of subsurface ice from monlesi ice cave switzerland the presence of cave ice is documented in many karst regions but very little is known about the age range of this potential paleoclimate archive this case study from the monlesi ice cave swiss jura mountains demonstrates that dating of cave ice is possible using a multi parameter approach ice petrography debris content and oxygen isotope composition have the potential for identification of annual growth layers but require a continuous core from the ice deposits limiting application of this approach furthermore complete melting of ice accumulations from individual years may occur causing amalgamation of several annual bands use of 3 h content of the ice and 14 c dating of organic debris present in the ice proved to be of limited utility providing rather broad bounds for the actual age initial estimates based on 210 pb analyses from clear ice samples gave results comparable to those from other methods the most reliable techniques applied were the determination of ice turnover rates and the dating of anthropogenic inclusions a roof tile in the ice these suggest respectively that the base of the cave ice was a minimum of 120 and a maximum of 158 years old therefore our data support the idea that mid latitude and low altitude subsurface ice accumulations result from modern deposition processes rather than from presence of pleistocene relict ice

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

fresnel volume migration of single component seismic data standard implementations of kirchhoff prestack depth migration psdm distribute the recorded wavefield along two way traveltime isochrons and an image is generated by constructive interference of these isochrons along the actual reflector elements beside the recent developments of wave equation based approaches kirchhoff psdm is still considered widely as a state of the art technique in obtaining high quality images of the subsurface particularly for highly irregular survey layouts and target oriented imaging tasks however for sparse sampling or limited aperture the resulting image is affected by significant migration noise as a result of limited constructive interference of the back propagated wavefield some modifications have been proposed to reduce these artifacts these modifications include constructing a specular path of wave propagation derived from estimates of the emergent angle of coherent phases in the seismogram section and the mainly heuristic restriction of the imaging operator to the neighborhood of that wavepath our approach uses fresnel volumes to restrict the migration operator in a physically frequency dependent way using the emergent angle at the receiver determined by a local slowness analysis a ray is propagated into the subsurface the back propagation of the wavefield is restricted to the vicinity of this ray according to its approximated fresnel volume this so called fresnel volume migration approach enhances image quality significantly compared with standard kirchhoff psdm because of the inherent focusing and the restriction of the back propagation to the region around the actual reflection point

reflection image spectroscopy across the andean subduction zone abstract this paper presents new insights into the south american subduction zone from reprocessed seismic images we applied a 3d kirchhoff prestack depth migration scheme to data sets containing different narrow frequency ranges in order to extract additional details from seismic reflection images this approach accounts for the effects of scattering on the seismic image especially for structures below a heterogeneous overburden the reflection image in such environments will differ significantly when focusing on different frequency ranges due to the frequency dependence of scattering that is likely to be present the narrow frequency range images uncover reflectors in one frequency range that are masked in another range furthermore the images enable for instance the characterization of the medium in terms of scatterer concentration and thus improve the structural interpretation the analysis of these images might help to distinguish between small scale structures in the high frequency band and large scale structures in the low frequency band we call this imaging approach reflection image spectroscopy ris we applied the ris approach to the ancorp 96 data set an onshore deep seismic reflection profile across the south american central andes the narrow frequency range images revealed additional details that we interpret as features directly linked to fluid migration processes in the subduction zone furthermore structural details of the oceanic crust and the overlying mantle and crust are revealed from the narrow frequency range images we interpret that the top of the so called nazca reflector at 70 km depth marks the upper limit of the hydrated mantle wedge whereas the bottom of the reflector represents the top of the subducted oceanic crust the compilation of our results with local earthquake data confirms this interpretation similar features observed in another deep seismic profile precorp 95 support this interpretation too furthermore the ris images show a highly reflective heterogeneous zone between the nazca reflector at 70 km depth and a prominent mid crustal bright spot quebrada blanca bright spot at about 30 km depth we associate this zone with a complex network of ascending fluids or partial melts initiated by ascending fluids released from the subducted oceanic plate this observation links the quebrada bright spot directly to the dehydrating oceanic plate

downhole physical property logging for iron oxide exploration rock quality and mining an example from central sweden abstract several physical properties obtained from geophysical logging and laboratory measurements were analyzed in order to characterize iron oxide mineralization and host rocks in the blotberget mining area of central sweden seven boreholes intersecting the mineralization between 300 and 600 m depth in a volcano sedimentary setting were downhole logged for this purpose the downhole logging included full waveform triple sonic natural gamma magnetic susceptibility formation resistivity fluid temperature and conductivity while laboratory measurements consisted of density rock quality designation and magnetite content measurements full waveform sonic data were used for rock quality assessments of the mineralized zones and their host rocks and proved their potential to be used for mine planning purposes the ore bearing rocks are primarily distinguished by increased density and dynamic elastic moduli estimated from the full waveform sonic logging although seismic velocities do not follow a linear increase with the density for the mineralized rocks as expected for igneous rocks it is observed that a strong seismic signal from the mineralization can be expected primarily due to their high density in addition the full waveform sonic data could be used as a proxy for fracture delineations and in situ rock quality assessment for example zones of washed up amplitudes in these data correlate well with zones of poor quality rocks identified by core logging based on the full waveform sonic data seismic attenuation and its reciprocal the seismic quality factor were calculated a decrease in the seismic quality factor was observed at zones with low rock quality designation but also correlated with the mineralized zones suggesting several fracture zones in the mineralization and that the ore bearing rocks might be less competent than the surrounding host rocks eventual rock support and reinforcement might be required for future mining operations full waveform sonic data have the potential to improve rock quality assessments for mine planning and exploration purposes

ratios of mg2 na in snowpack and an ice core at austfonna ice cap svalbard as an indicator of seasonal melting snowpack and ice core samples were collected from the dome of austfonna ice cap svalbard in the spring of both 1998 and 1999 the samples were analyzed for anions cations ph liquid electrical conductivity and oxygen isotopes concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack there was a clear difference between mg 2 na ratios previously in melted snowpack 0 011 0 02 and in unmelted snowpack 0 11 0 02 we propose that the mg 2 na ratio can be used as an indicator of whether or not firn or bubbly ice in the austfonna ice core has experienced melt percolation the mg 2 na ratio indicates that firn or bubbly ice prior to ad 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920

the 800 year long ion record from the lomonosovfonna svalbard ice core we present a high resolution record of water soluble ion chemistry from a 121 m ice core spanning about 800 years the core is well dated to 2 3 depth using cycle counting and reference horizons and a simple but close fitting model for the lower 1 3 of the core this core suffers from modest seasonal melt and so we present concentration data in decadal running means to minimize percolation effects sea salt ions na cl mg2 and k account for more than 70 of all ions in general sea salt ion concentrations are rather variable and have no clear association with climatic variations sulfate with 74 being from non sea salt sources has higher concentrations than seen on vestfonna ice cap but lower than in ny alesund aerosols suggesting central spitsbergen receives more marine westerly air masses than ny alesund but more sulfate enriched easterly air masses than nordaustlandet clear anthropogenic impacts are found for sulfate nitrate and ammonium and probably excess chloride after the mid twentieth century with sulfate showing a significant rise by the end of the nineteenth century sulfate and methanesulfonate concentrations correlate well during the twentieth century and it is clear that most of the preindustrial sulfate is of biogenic origin terrestrial component ca2 has the highest concentrations in the coldest part of the little ice age suggesting more windy conditions transporting local terrestrial dust to the ice cap all ion concentrations decrease at the end of the twentieth century which reflects loss of ions by runoff with non sea salt magnesium being particularly sensitive to melting

improved structural characterization of the earth s crust at the german continental deep drilling site using advanced seismic imaging techniques this paper describes the principles of three novel seismic imaging techniques and their application to two deep seismic reflection data sets from the vicinity of the german continental deep drilling site ktb these imaging techniques are based on kirchhoff prestack depth migration and use an inherent restriction of the migration operator to focus the wavefield to its actual reflection point for fresnel volume migration the emergent angle at the receivers is estimated and then used to propagate the wavefield back into the subsurface along which the fresnel volume is determined the migration operator is restricted to this volume thereby focusing the image to the part of the isochrone which physically contributes to the reflection for coherency migration the coherency of the wavefield at neighboring traces is calculated and used as a weighting factor within the migration integral leading to a comparable focusing to the reflection point for coherency based fresnel volume migration both approaches are combined resulting in an even more focused seismic image with significantly increased image quality we applied these methods to two seismic data sets from the area around the ktb a survey with standard split spread geometry ktb8502 and a sparse data set with a small number of source points in combination with short receiver lines instruct93 the focusing approaches yield major improvements in the final images for both data sets incoherent noise and migration artifacts are reduced and the visibility of crustal structures is strongly enhanced allowing for an improved geologic and tectonic characterization

magnetic characterisation of magnetite and hematite from the blotberget apatite iron oxide deposits bergslagen south central sweden rock magnetic measurements were carried out on drill core material and hand specimens from the blotberget apatite iron oxide deposit in the bergslagen ore province south central sweden to chara

the exploration of sedimentary bauxite deposits using the reflection seismic method a case study from the henan province china abstract sedimentary bauxite usually occurs in gently dipping or monoclinic folded formations the roof of syncline bauxite tends to be flat and the bottom appears to be similar to a concave bucket until recently mainly non seismic geophysical exploration methods such as gravity magnetic and electrical methods have been used in the exploration of syncline bauxite deposits however both the thickness and depth of bauxite deposits can vary significantly therefore gravity magnetic electrical and other non seismic methods have technical limitations especially when planning exploration drill targets by contrast seismic methods have advantages in the exploration of concealed bauxite deposits due to their high vertical resolution in this study reflection seismics are adopted to detect bauxite layers in china s henan province it is observed that strong reflection interfaces positive phases appeared on the top surfaces of the bauxite layers meanwhile weak reflection interfaces both positive and negative phases are recorded appeared on the upper surface of the lower overlying limestone layer seismic reflection methods cannot only define the shape and structure of the bauxite layers but also indicating their relative depth and thickness respectively importantly subsequent exploration drilling confirmed our seismic interpretation

10be in the akademii nauk ice core first results for ce 1590 1950 and implications for future chronology validation temporal variations of the radionuclide 10be are broadly synchronous across the globe and thus provide a powerful tool to synchronize ice core chronologies from different locations we compared the 10be record of the akademii nauk an ice core russian arctic for the time period ce 1590 1950 to the 10be records of two well dated greenland ice cores dye3 and ngrip a high correlation r 0 59 was found between the an and dye3 records whereas the correlation with ngrip was distinctly lower r 0 45 sources of deviations may include local fluctuations in the deposition of 10be due to changes in the precipitation patterns and artefacts due to the core sampling strategy in general the existing age model was validated confirming the an ice core to be a unique and welldated source of palaeoclimate parameters for the russian arctic we further used numerical simulations to test the influence of the core sampling strategy on the results and derived an optimized sampling strategy for the deeper parts of the ice core

improved target illumination at ludvika mines of sweden through seismic interferometric surface wave suppression in mineral exploration new methods to improve the delineation of ore deposits at depth are in demand for this purpose increasing the signal to noise ratio through suitable data processing is an

high frequency observations of melt effects on snowpack stratigraphy kahiltna glacier central alaska range with an increased volume of melt on many of the world s glaciers study of how meltwater affects the properties of glacial snowpack becomes essential to our understanding of how glaciers will respond to climate change we address this problem by studying how snow properties changed on sub daily timescales on the kahiltna glacier alaska between may 26 and june 10 2010 during this period we dug 1 8 m deep snow pits twice daily to record the stratigraphy of melt layers snow hardness grain size and density and sampled for hydrogen isotopic composition d on four occasions from these data we show that 65 of the melted surface snow infiltrates and refreezes in the snowpack this leads to a densification of the snow a 729 increase in volume of melt layers and a homogenization of isotopic and physical snow properties from visual and stratigraphic observations we show that meltwater flow within the snowpack is conducted primarily along lenses and pipes where melt layers later form but that more homogeneous capillary based flow is also important finally we show using isotope ratios that post depositional alteration is exacerbated with increased melt extent using the d profile below a volcanic ash layer as a case study in the future similar studies would benefit from this high frequency monitoring approach to assessing snowpack evolution as it allows for a greater understanding of short duration processes new directions for study would include longer term monitoring efforts over a wider spatial snow pit network copyright 2012 john wiley sons ltd

nonlinear refraction traveltime tomography a few important issues for performing nonlinear refraction traveltime tomography have been identified they include the accuracy of the traveltime and raypath calculations for refraction the physical information in the refraction traveltime curves and the characteristics of the refraction traveltime errors consequently we develop a shortest path ray tracing method with an optimized node distribution that can calculate refraction traveltimes and raypaths accurately in any velocity model we find that structure ambiguity caused by short and long rays in the seismic refraction method may influence the inversion solution significantly therefore we pose a nonlinear inverse problem that explicitly minimizes the misfits of the average slownesses ratios of traveltimes to the corresponding ray lengths and the apparent slownesses derivatives of traveltimes with respect to distance as a result we enhance the resolution as well as the convergence speed to regularize our inverse problem we use the tikhon

using high resolution tritium profiles to quantify the effects of melt on two spitsbergen ice cores ice cores from small ice caps provide valuable climatic information additional to that of greenland and antarctica however their integrity is usually compromised by summer meltwater percolation

assessing source areas of pollutants from studies of fly ash charcoal and pollen from svalbard snow and ice 1 temporal variations in the quantities of pollen charcoal and scp spheroidal carbonaceous particles contained in the lomonosovfonna ice core from svalbard and in the surface snow of the ice cap are presented the abundance of these microparticles is illustrated for the period a d 1850 1997 from the ice core together with detailed snow pit stratigraphies for summer 2001 to spring 2002 viewing scp and pollen together is a new approach with relevance for tracing the possible origin of contaminants the scp are related to the pollution source while the pollen gives an indication of the vegetation at the point of origin the deposition of scp on the ice is also compared with deposition of scp in northern fennoscandia for the period a d 1982 1997 the quantity of pollen and the pollen types recorded suggest an origin in fennoscandia rather than in north america the temporal pattern of both scp and charcoal deposition reflects that of europe but may also contains a local signal

man s footprint on the arctic environment as revealed by analysis of ice and snow abstract the date of the definitive start to the anthropocene is still under debate and although a lot of progress has been made currently available data is not precise enough to define the start of the human dominated geological epoch we know that during and after the industrial revolution humans started having a much greater impact on the earth s environment increases in population have led to increases in resource and fossil fuel use leaving a marked impact on our planet this impact in the northern hemisphere is effectively recorded in the snow and ice of the arctic human activity has changed various biogeochemical cycles to such an extent that the climate has started to change this has disturbed the biosphere pushing it to adapt in response to these changes through evolutionary pressure the arctic is a particularly vulnerable environment and mankind is having a profound impact on its fragile equilibrium higher concentrations of heavy metals organic compounds and radionuclides have been detected in ice cores as well as snow although climatic changes are evident on a global scale in the arctic these changes have been amplified advances in laboratory analysis methods have been applied to ice cores and surface snow samples to help us understand the mechanisms governing this fragile environment and to evaluate the impact and amplitude of human activity despite these advances the fluxes and distributions over time of anthropogenic organic compounds is largely unknown hopefully advances in analytical methods will mean that this is not the case in the future

surface wave analysis for static corrections in mineral exploration a case study from central sweden in mineral exploration increased interest towards deeper mineralizations makes seismic methods attractive one of the critical steps in seismic processing workflows is the static correction which

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

methanesulfonic acid in a svalbard ice core as an indicator of ocean climate methanesulfonic acid msa is an atmospheric oxidation product of dimethyl sulfide produced by marine biota msa preserved in a svalbard glacier between 1920 and 1996 is compared with the sea surface temperature sst and sea ice extent of the surrounding ocean over the same period on decadal timescales high msa concentrations are found to be associated with warm sst and reduced sea ice extent msa appears to be influenced by climatic changes related to variations in the import of warm atlantic water to the barents sea atlantic water plays an important role in the arctic climate system therefore msa concentrations may indirectly reflect larger scale changes in the region and may be useful as a proxy for past climate

ice core net snow accumulation and seasonal snow chemistry at a temperate glacier site mount waddington southwest british columbia canada a 141m ice core was recovered from combatant col 51 385 n 125 258 w 3000ma s l mount waddington coast mountains british columbia canada records of black carbon dust lead and water stable isotopes demonstrate that unambiguous seasonality is preserved throughout the core despite summer surface snowmelt and temperate ice high accumulation rates at the site 4 m ice eq a 1 limit modification of annual stratigraphy by percolation of surface meltwater the ice core record spans the period 1973 2010 an annually averaged time series of lead concentrations from the core correlates well with historical records of lead emission from north america and with ice core records of lead from the greenland ice sheet the depth age scale for the ice core provides sufficient constraint on the vertical strain to allow estimation of the age of the ice at bedrock total ice thickness at combatant col is 250 m an ice core to bedrock would likely contain ice in excess of 200 years in age accumulation at combatant col is significantly correlated with both regional precipitation and large scale geopotential height anomalies

deep reflection seismic imaging of iron oxide deposits in the ludvika mining area of central sweden abstract reflection seismic data were acquired within two field campaigns in the blotberget ludvika mining area of central sweden for deep imaging of iron oxide mineralization that were known to extend down to 800 850 m depth the two surveys conducted in years 2015 and 2016 one employing a seismic landstreamer and geophones connected to wireless recorders and another one using cabled geophones and wireless recorders aimed to delineate the geometry and depth extent of the iron oxide mineralization for when mining commences in the area even with minimal and conventional processing approaches the merged datasets provide encouraging information about the depth continuation of the mineralized horizons and the geological setting of the study area multiple sets of strong reflections represent a possible continuation of the known deposits that extend approximately 300 m further down dip than the known 850 m depth obtained from historical drilling they show excellent correlation in shape and strength with those of the blotberget deposits furthermore several reflections in the footwall of the known mineralization can potentially be additional resources underlying the known ones the results from these seismic surveys are encouraging for mineral exploration purposes given the good quality of the final section and fast seismic surveys employing a simple cost effective and easily available impact type seismic source

glacial interglacial changes in ocean surface conditions in the southern hemisphere the stable isotope signatures of oxygen and hydrogen in the water of preserved ice and snow are both widely used to infer local temperatures of past environments a derived quantity based on these two signatures the deuterium excess 1 provides additional palaeoclimatic information2 3 4 as this parameter depends on the meteorological and oceanic characteristics of the water s source regions in particular their temperature2 3 and relative humidity4 published studies mainly focus on records from the past 40 000 years here we present a deuterium excess history obtained from ice cores from vostok east antarctica spanning the full glacial interglacial cycle of the past 150 000 years the deuterium excess record shows a strong anticorrelation with the earth s orbital obliquity 41 000 year periodicity and values are markedly higher during the cold stage 5d following the last interglacial than during the other cold stages we interpret the relationship with obliquity as resulting from changes in the latitudinal insolation gradient affecting ocean surface conditions and thus the delivery of moisture to the polar region we argue that the high 5d values relative to other cold stages are driven by relatively less moisture delivered from high latitudes and more from low latitudes the deuterium excess in antarctic precipitation thus provides long term spatially integrated information on ocean surface conditions and ocean atmosphere circulations in the southern hemisphere

the methanesulfonic acid msa record in a svalbard ice core svalbard ice cores have not yet been fully exploited for studies of climate and environmental conditions in one recently drilled ice core from lomonosovfonna we have studied the methanesulfonic acid msa records in relation to temperature and sea ice under the present climatic conditions msa appears to be negatively correlated with the sea ice conditions in the barents sea and positively correlated with the instrumental temperature record from svalbard however prior to about 1920 the msa concentrations were about twice as high despite the more extensive sea ice coverage after exploring different possibilities we suggest that msa concentrations were higher in the 19th century than in the 20th century due to increased primary production in response to increased vertical stability of the sea surface layers caused by increased meltwater production from the more extensive sea ice cover thus the msa record from lomonosovfonna probably both is a measure of the regional sea ice variability on the multi decadal scale and reflects locally favorable conditions for marine biogenic dimethyl sulfide dms production on the sub decadal scale

fresnel volume migration of multicomponent data if the aperture of a seismic reflection experiment is strongly limited kirchhoff migration suffers from strong artifacts attributable to incomplete summation this can be overcome by restricting the migration operator to the region that physically contributes to a reflection event examples of such limited aperture experiments include data acquisition in boreholes tunnels and mines we present an extension to three component 3c kirchhoff prestack depth migration where the migration operator is restricted to the fresnel volume of the specular reflected raypath we use the measured polarization direction at a 3c receiver to determine points of specular reflection in homogeneous media the polarization angle of 3c data can be used directly to decide whether a certain image point belongs to the fresnel volume of a specular reflection in heterogeneous media the fresnel volume around an image point is approximated by means of paraxial ray tracing the method is tested on a synthetic vertical seismic profiling experiment with strongly limited aperture migration artifacts and crosstalk effects from converted waves are strongly reduced compared with standard migration schemes the method is successfully applied to seismic data acquired in a tunnel

the effects of meltwater percolation on the seasonal isotopic signals in an arctic snowpack we investigate the evolution of snow temperature water content density and stable water isotopes of 18 o at four arctic snow pit sites during early season melt in order to understand the effects of melt on snowpack stratigraphies and seasonal isotopic signals we relate isotopic changes observed at these sites to temperature reconstructions derived from a 33 year firn core record drilled on the same icefield decreases in seasonal isotopic amplitudes observed at all but one snow pit site coincide with the percolation of more enriched meltwater into the snowpack suggesting that meltwater percolation is the dominant process causing isotopic redistribution in arctic snowpacks during the melt season the decrease in isotopic range was accompanied by increases in mean 18 o values at all snow pit sites positive degree day pdd calculations are used to relate the amount of melt observed at the low elevation snow pit sites to the firn core site results based on pdd values suggest an average overestimation of 1 1 c in average annual temperature reconstructions from the firn core site from 1967 to 2006 with the possibility of errors in excess of 3 c during high melt years

statistical extraction of volcanic sulphate from nonpolar ice cores 1 ice cores from outside the greenland and antarctic ice sheets are difficult to date because of seasonal melting and multiple sources terrestrial marine biogenic and anthropogenic of sulfates deposited onto the ice here we present a method of volcanic sulfate extraction that relies on fitting sulfate profiles to other ion species measured along the cores in moving windows in log space we verify the method with a well dated section of the belukha ice core from central eurasia there are excellent matches to volcanoes in the preindustrial and clear extraction of volcanic peaks in the post 1940 period when a simple method based on calcium as a proxy for terrestrial sulfate fails due to anthropogenic sulfate deposition we then attempt to use the same statistical scheme to locate volcanic sulfate horizons within three ice cores from svalbard and a core from mount everest volcanic sulfate is 5 of the sulfate budget in every core and differences in eruption signals extracted reflect the large differences in environment between western northern and central regions of svalbard the lomonosovfonna and vestfonna cores span about the last 1000 years with good extraction of volcanic signals while holtedahlfonna which extends to about ad1700 appears to lack a clear record the mount everest core allows clean volcanic signal extraction and the core extends back to about ad700 slightly older than a previous flow model has suggested the method may thus be used to extract historical volcanic records from a more diverse geographical range than hitherto

the derivation of an anisotropic velocity model from a combined surface and borehole seismic survey in crystalline environment at the cosc 1 borehole central sweden the scandinavian caledonides provide a well preserved example of a palaeozoic continent continent collision where surface geology in combination with geophysical data provides information about th

first ice core records of no3 stable isotopes from lomonosovfonna svalbard samples from two ice cores drilled at lomonosovfonna svalbard covering the period 1957 2009 and 1650 1995 respectively were analyzed for no 3 concentrations and no3 stable isotopes n 15

facies analysis of a 1 9 ga continental margin back arc felsic caldera province with diverse zn pb ag cu au sulfide and fe oxide deposits bergslagen region sweden the bergslagen mining district in south central sweden has been a major metal producer for more than 1 000 years in geologic terms bergslagen is the intensely mineralized part of a large early proterozoic mainly 1 90 1 87 ga felsic magmatic region of mainly medium to high metamorphic grade in the baltic shield the district contains a diverse range of ore deposit types including banded iron formation magnetitecalc silicate skarn manganiferous skarn and carbonate hosted iron ore apatite bearing iron ore stratiform and strata bound zn pb ag cu au sulfide ores and w skarn most ore deposits occur in hydrothermally altered metavolcanic rocks and associated metalimestones and skarns this study is a field oriented regional facies analysis based on recognition of primary volcanic and sedimentary features through the strong overprints of hydrothermal alteration deformation and metamorphism the region is interpreted as an extensional probably back arc active continental margin magmatic region it evolved through stages of intense magmatism thermal doming and crustal extension followed by waning extension waning volcanism thermal subsidence reversal from extension to compressional deformation regional metamorphism and structural inversion the volcanic successions comprise interfingering proximal near vent medial volcano flanks and distal volcano margin facies associations of rhyolitic pyroclastic caldera volcanoes and subordinate dacite rhyolite complexes nonwelded to poorly welded pyroclastic flow and fallout units and their rapidly resedimented subaerial and subaqueous equivalents are the most abundant volcanic facies subvolcanic porphyritic intrusions and cryptodomes are also abundant the pyroclastic debris was shed from mainly shallow water and subaerial proximal areas to shallow and moderately deep water above and below storm wave base distal areas most ore deposits formed during the regional waning volcanic stage and occur in medial to distal facies associations that comprise rhyolitic ash siltstone limestone and vitric crystal sandstone and breccia these mineralized facies associations were deposited in subaqueous environments mainly below the fair weather wave base but locally above the storm wave base water depths are interpreted to have been mainly 10 to 500 m with local deeper areas although the ore deposits occur in medial to distal facies associations many occur above or laterally adjacent to subsided volcanic vent complexes this suggests a spatial temporal and possible genetic relationship between several ore deposit types and the late magmatic stage of these volcanic centers except for the apatite bearing iron deposits it is uncertain if the ores are genetically related to specific magmatic hydrothermal events from specific volcanoes this is possible especially for the base metal sulfide deposits which have intense localized footwall alteration in felsic volcanic rocks however an important role of the volcanic centers may have been to provide strong positive pertubations or magmatic hydrothermal input to the regional convective geothermal system the main zn pb ag cu au ore deposits span a range between two end member types stratiform ash siltstone hosted sea floor deposits that have similarities to some stratiform sediment hosted zn pb ag deposits especially the broken hill type deposits and strata bound volcanic associated limestone skarn subsea floor replacement deposits that more closely resemble felsic volcanic associated massive sulfide deposits facies models are presented for both the banded iron formations are interpreted as chemical suspension deposits rhythmically interbedded with rhyolitic ash siltstone the skarn iron ores are strata bound in limestones and include metamorphosed sedimentary ores and metasomatic replacements apatite bearing iron ores differ in setting from the other ores in being formed within a dacitic intrusive complex that may be the root zone of a dacite rhyolite volcanic center

effect of periodic melting on geochemical and isotopic signals in an ice core from lomonosovfonna svalbard 1 we examine the quality of atmospherically deposited ion and isotope signals in an ice core taken from a periodically melting ice field lomonosovfonna in central spitsbergen svalbard the aim is to determine the degree to which the signals are altered by periodic melting of the ice we use three diagnostics 1 the relation between peak values in the ice chemical and isotopic record and ice facies type 2 the number of apparent annual cycles in these records compared with independently determined number of years represented in the ice core and 3 a statistical comparison of the isotopic record in the ice core and the isotope records from coastal stations from the same region we find that during warm summers as much as 50 of the annual accumulation may melt and percolate into the firn in a median year this decreases to similar to25 as a consequence of percolation the most mobile acids show up to 50 higher concentrations in bubble poor ice facies compared with facies that are less affected by melt most of the other chemical species are less affected than the strong acids and the stable water isotopes show little evidence of mobility annual or biannual cycles are detected in most parameters and the water isotope record has a comparable statistical distribution to isotopic records from coastal stations we conclude that ice cores from sites like lomonosovfonna contain a useful environmental record despite melt events and percolation and that most parameters preserve an annual or in the worst cases a biannual atmospheric signal

reconstruction of the undiffused seasonal oxygen isotope signal in central greenland ice cores the climatologically important seasonal signal in ice core oxygen isotope records is altered by diffusion with time here we use the diffusion model of whillans and grootes 1985 to calculate the effects of isotopic diffusion in nine shallow ice cores recovered over a 150 150 km grid centered on summit greenland two different computational methods give similar results for the back diffused 18o seasonal extrema although back diffusing the ice core 18o records improves the correlations between the individual ice core oxygen isotope and greenland coastal temperature records the correlations remain poor particularly for the low accumulation sites stacking the back diffused isotopic records from several cores results in much higher correlations with a strong winter linkage between west coast stations and central greenland these correlations are also significantly greater than the correlations between the stacked measured diffused isotopic profiles and coastal temperatures our results indicate that the use of ice core isotopic records to identify anomalous seasons requires that diffusion effects be accounted for

deuterium excess record from a small arctic ice cap in this paper we present a deuterium excess d record from an ice core drilled on a small ice cap in svalbard in 1997 the core site is located at lomonosovfonna at 1255 m asl and the analyzed time series spans the period 1400 1990 a d the record shows pronounced multidecadal to centennial scale variations coherent with sea surface temperature changes registered in the subtropical to southern middle latitude north atlantic during the instrumental period we interpret the negative trend in the deuterium excess during the 1400s and 1500s as an indication of cooling in the north atlantic associated with the onset of the little ice age consistently positive anomalies of d after 1900 peaking at about 1950 correspond with well documented contemporary warming yet the maximum values of deuterium excess during 1900 1990 are not as high as in the early part of the record pre 1550 this suggests that the sea surface temperatures during this earlier period of time in the north atlantic to the south of approximately 45 degrees n were at least comparable with those registered in the 20th century before the end of the 1980s we examine the potential for a cold bias to exist in the deuterium excess record due to increased evaporation from the local colder sources of moisture having isotopically cold signature it is argued that despite a recent oceanic warming the contribution from this local moisture to the lomonosovfonna precipitation budget is still insufficient to interfere with the isotopic signal from the primary moisture region in the midlatitude north atlantic

a plot scale study of firn stratigraphy at lomonosovfonna svalbard using ice cores borehole video and gpr surveys in 2012 14 spatial heterogeneity of snow and firn properties on glaciers introduces uncertainty in interpretation of point and profile observations and complicates modelling of meltwater percolation and runof

tracking the multiple stage exhumation history and magmatic hydrothermal events of the west junggar region nw china evidence from 40 ar 39 ar and u th he thermochronology abstract to decipher cooling events in the west junggar region biotite and k feldspar 40ar 39ar and zircon and apatite u th he isotopic analyses of intrusive rocks were carried out previous u pb data showed that intrusive bodies in the baogutu area were emplaced at 315 310 ma u pb and zircon u th he dating results 313 241 ma suggest that a magmatic hydrothermal event lasted for 72 ma in the baogutu area of the west junggar region early stage high temperature alteration 900 300 c lasted for 6 2 ma and was followed by prolonged phyllic and argillic alteration lasting 67 63 ma between 350 and 200 c finally slower cooling occurred between 200 and 70 c accompanied by post mineralization uplift and erosion in this study three main episodes of relatively rapid cooling were distinguished in the west junggar region i e late carboniferous early permian 307 277 ma middle triassic 241 232 ma and early cretaceous 145 120 ma the first rapid cooling during the late carboniferous early permian was possibly associated with the release of magmatic heat the middle triassic and early cretaceous cooling and exhumation are interpreted as a response to collision s between the qiangtang and kunlun qaidam or lhasa blocks the cenozoic india eurasia collision however may have had little or no effect on modern tectonic reactivation of the west junggar region