the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland

holocene glacier variability and neoglacial hydroclimate at alfotbreen western norway abstract glaciers and small ice caps respond rapidly to climate perturbations mainly winter precipitation and summer temperature and the mass balance of glaciers located in western norway is governed mainly by winter precipitation pw records of past pw can offer important insight into long term changes in atmospheric circulation but few proxies are able to accurately capture winter climate variations in scandinavia reconstructions of equilibrium line altitude ela variations from glaciers that are sensitive to changes in pw therefore provide a unique opportunity to quantify past winter climate in this region here we present a new holocene glacier activity reconstruction for the maritime ice cap alfotbreen in western norway based on investigations of distal glacier fed lake sediments and modern mass balance measurements 1963 2010 several lake sediment cores have been subject to a suite of laboratory analyses including measurements of physical parameters such as dry bulk density dbd and loss on ignition loi geochemistry xrf surface magnetic susceptibility ms and grain size distribution to identify glacial sedimentation in the lake both radiocarbon ams 14 c and 210 pb dating were applied to establish age depth relationships in the sediment cores a novel approach was used to calibrate the sedimentary record against a simple ela model which allowed reconstruction of continuous ela changes for alfotbreen during the neoglacial when alfotbreen was present i e the last 1400 years furthermore the resulting ela variations were combined with an independent summer temperature record to calculate neoglacial pw using the liestol equation the resulting pw record is of higher resolution than previous reconstructions from glaciers in norway and shows the potential of glacier records to provide high resolution data reflecting past variations in hydroclimate complete deglaciation of the alfotbreen occurred 9700 cal yr bp and the ice cap was subsequently absent or very small until a short lived glacier event is seen in the lake sediments 8200 cal yr bp the ice cap was most likely completely melted until a new glacier event occurred around 5300 cal yr bp coeval with the onset of the neoglacial at several other glaciers in southwestern norway alfotbreen was thereafter absent or very small until the onset of the neoglacial period 1400 cal yr bp the little ice age lia 650 50 cal yr bp was the largest glacier advance of alfotbreen since deglaciation with a maximum extent at 400 200 cal yr bp when the ela was lowered approximately 200 m relative to today the late onset of the neoglacial at alfotbreen is suggested to be a result of its low altitude relative to the regional ela a synthesis of neoglacial ela fluctuations along the coast of norway indicates a time transgressive trend in the maximum extent of the lia which apparently seems to have occurred progressively later as we move northwards we suggest that this trend is likely due to regional winter precipitation differences along the coast of norway

holocene glacier activity at the southwestern part of hardangerjokulen central southern norway evidence from lacustrine sediments lacustrine sediments from lake isdalsvatn downstream from the southwestern margin of the plateau glacier hardangerjokulen central southern norway show that the lake received glacial meltwater until 7890 95 bp a thin bluish grey minerogenic silt layer probably reflects a short glacial re advance between 7005 90 and 6835 150bp after the latter date inflow of glacial meltwater ceased indicating that small or more probably no glaciers existed on the southwestern hard angerjokulen plateau a drop in organic content and a slight increase in detrital content inferred from magnetic susceptibility at 120cm depth in the core may indicate some glacier activity in the catchment from about 3400 bp textural changes at 50cm depth indicate increased neoglacial activity in the upper catchment area from 2265 80 bp differences in glacier chronologies between the southern and northern sectors of hardangerjokulen may be explained partly by different glacier responses to the precipitation and wind distribu

multicomponent paleomagnetic data from the nosoni formation eastern klamath mountains california cratonic permian primary directions with jurassic overprints paleomagnetic data from the guadelupian upper permian nosoni formation of the redding section rs consistently exhibit two directional components of magnetization in addition to a late quaternary normal weathering overprint six sites in ash flow tuffs and tuffaceous sedimentary rocks spanning 200 m of section yield data that allow precise characterization of all components two additional sites in calcareous mudstones were too heavily overprinted to yield stable paleomagnetic directions thermal demagnetization of the tuffaceous samples in 16 18 steps between natural remanent magnetization and 660 c provides a detailed data base from which to calculate directional components analysis of demagnetization trends identifies a prefolding reversed direction carried by both magnetite and hematite and a postfolding normal direction carried by hematite only petrologic considerations suggest paragenesis of these oxides in the permian primary magnetite and hematite and early middle jurassic metamorphic hematite least squares analysis of progressively demagnetized vector endpoint trends between 540 and 600 c yields a formation mean direction in magnetite having d 156 4 i 29 7 k 101 95 7 6 this result is in close agreement with the composite prefolding direction d 160 3 i 31 5 carried by both magnetite and hematite determined by the intersection of remagnetization circles the postfolding hematite carried overprint direction calculated by the latter technique has d 352 3 i 35 0 paleopoles corresponding to these two directions are located at 57 6 n 103 0 e magnetite formation mean and 67 0 n 104 1 e hematite overprint coinciding within error to upper permian and early jurassic respectively reference poles from the north american craton these data indicate no significant rotation or latitudinal translation of the sample sites with respect to cratonic north america since the permian this conclusion contrasts with seemingly reliable paleomagnetic results from elsewhere in the rs which indicate major post permian clockwise rotations these rotations are evidently specific to individual structural domains and are probably manifestations of oroclinal bending about vertical axes

scandinavian glacial and climatic fluctuations during the holocene abstract historical documents and lichenometric studies give a detailed picture of the little ice age in scandinavia there was a large advance in norway which has been dated at a few places to 1750 small readvances during the retreat occurred around a d 1780 1810 1840 1850 1850 1870 1890 1910 and 1930 in sweden most of these advances have been recognized and in addition extensive advances are dated by lichenometry to around a d 1600 1650 and 1700 1720 soils buried beneath moraines often yield radiocarbon dates that are much too old methods dependent on these must therefore be used with care evidence for pre little ice age advances are often considered equivocal the most reliable information is probably provided by studies of lacustrine sediments combining information from all sources the most significant pre little ice age glacier advances most likely occurred in 7 5 5 1 4 5 3 2 2 8 2 2 1 9 and 1 5 1 1 radiocarbon ka bp advances that were less extensive or for which there is less evidence occurred around 6300 5600 2500 940 600 560 and 380 bp

proglacial lakes character behaviour and geological importance proglacial lakes are ubiquitous within the quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information present deglaciation is increasing the number and size of proglacial lakes around the world this study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective we show how ice marginal or ice contact lakes and other distal proglacial lakes can be distinguished from each other by geomorphological sedimentological chemical and biological characteristics the key controls on proglacial lake geomorphology and sedimentology are outlined and discussed proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation proglacial lakes interrupt meltwater flux and are very efficient sediment traps hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the quaternary overall analyses of proglacial lakes can provide a valuable insight into i patterns character and behaviour of mountain glaciers ice sheets and glaciations and ii the impacts of past present and future deglaciation

paleomagnetic study of the eastern klamath terrane california and implications for the tectonic history of the klamath mountains province paleomagnetic study of permian through jurassic volcanic and sedimentary strata of the eastern klamath terrane has shown the remanent magnetization of many of these rocks to be prefolding and most likely primary similarities in magnetic declinations recorded by coeval strata over a broad area are consistent with the hypothesis that the terrane in general has behaved as a single rigid block paleomagnetic data indicate that the volcanic island arc represented by this terrane the nucleus of the province was facing toward the present southwest during late paleozoic time although its orientation during earlier periods is unknown whether the arc was separated from the north american craton by a small marginal basin or originated far offshore cannot be determined from paleomagnetic data the declination anomalies for both permian and triassic strata are similar average 106 12 so we infer that clockwise rotation of the late paleozoic arc did not begin until latest triassic or earliest jurassic time the arc may have completed its initial rotation with respect to stable north america by middle jurassic time after some retrograde motion the arc was again facing west by the late jurassic by which time some of the more westerly terranes of the province had become attached to the eastern klamath terrane the composite klamath mountains terranes continued to rotate until the final 60 of clockwise rotation was nearly complete by the early cretaceous coincidence of the waning stages of rotation at about 136 ma with the beginning of deposition of the basal great valley sequence onto the klamath basement probably represents the completion of accretion of the klamath mountains terranes to the north american continent nearly all the rotation occurred while the klamath mountains terranes were part of a converging oceanic plate with only about 20 of rotation in mid tertiary time during basin and range extension no data currently available show evidence for any significant latitudinal displacement of any klamath mountains terranes relative to cratonic north america

structural study of intra oceanic thrusting in the klamath mountains northern california implications on accretion geometry the kinematics of the basal intra oceanic thrust of the trinity preston peak seiad and josephine ultramafic bodies of the klamath mountains are deduced from microstructural and mineral preferred orientation studies when corrected of possible postthrusting rotations these kinematics are thought to reflect the paleoconvergence geometry of the pacific plate relative to the north american continent at the time of intra oceanic thrusting we first detail the kinematics of thrusting for each studied massif these results are then integrated in a plate tectonics reconstruction and a model of continuous ne sw convergence for mesozoic times is proposed

holocene climatic change in swedish lapland inferred from an oxygen isotope record of lacustrine biogenic silica holocene climatic variability was studied in a 9500 year lake sediment sequence from the abisko region in swedish lapland using the oxygen isotope ratio in diatom biogenic silica d 18 osi oxygen and hydrogen isotope ratios of waters from the abisko area suggest that in this region the evaporative flux is small and the isotopic composition of most lakes reflects that of the local precipitation the hydrological setting of the region and sensitivity analysis of isotopic response to changing climatic parameters such as humidity inflow and evaporation show that the downcore diatom d18osi record is primarily controlled by changes in the summer isotopic composition of the lake water the overall 3 5 depletion in d 18 osi since the early holocene is interpreted as an increase in the influence of the arctic polar continental air mass that carries depleted precipitation we estimate that this change is associated with a 2 5 4 c cooling that has occurred since the early holocene in general the diatom d 18 osi record resembles the average annual air temperature reconstructed for the greenland ice core gisp2 especially during the past 4000 years with a pronounced cooling starting at 2000 years bp

experimental studies of seismoelectric conversions in fluid saturated porous media when seismic waves generate a relative fluid solid motion in a fluid saturated porous medium the moving charges streaming current in the electric double layer induce an electromagnetic em field this paper first experimentally confirms that the coupling between the seismic wave and the electromagnetic field in the kilohertz range is electrokinetic in nature seismoelectric signals are measured in homogeneous cylindrical porous rock samples and multilayered models the seismoelectric signals in homogeneous rock are electric fields that move along with the acoustic wave the mechanism of the seismoelectric conversion is completely different from the piezoelectric effect of quartz grains the seismoelectric sensitivity with respect to salinity of the saturant has been experimentally determined the amplitude of seismoelectric signals increases as the saturant conductivity decreases the seismoelectric effects are generated by two different mechanisms both the em radiation and the electric potential generated at an interface and within a porous medium respectively were measured as the p wave at ultrasonic frequencies passes through the layered models our experimental results demonstrate that seismoelectric effects exist and are measurable in the kilohertz range the paper concludes with a comparison of experimental data and modeled data in a three layer porous model seismoelectric measurements could be an effective means of obtaining transport coefficients such as hydraulic permeability and other porous rock properties

lake sediment studies of holocene glacial activity in the karsa valley northern sweden contrasts in interpretation a multidisciplinary study of lake sediments deposited in lake basins in the karsa valley northern sweden suggests the complete disappearance of the karsa glacier during the early and mid holocene glacier reformation indicated by the deposition of sediment with a fine particle size distribution and low organic content in the three lakes took place at c 3000 14 c years bp this interpretation contrasts with a study based on the weight loss on ignition of the same sediments which suggests several glacier advances throughout the entire holocene the contrasting interpretation is due to different methodological approaches single core site studies should be avoided in the future and only features that are consistently reproducible and can be dated in spatially distributed cores should be interpreted in terms of variations in glacial activity environmental conditions and ultimately climate

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

glacial activity reflected in a continuous lacustrine record since the early holocene from the proglacial laigu lake on the southeastern tibetan plateau abstract the southeastern tibetan plateau is an important area of monsoonal maritime glaciation and it serves as a watershed for several major asian rivers including the brahmaputra river and the lantsang river glacial activity is sensitive to climate change in this area however due to high annual ablation and accumulation in this region ice cores over long time scales are difficult to retrieve in addition reconstructed glacial activity from moraine dates is usually discontinuous here we use a sediment core retrieved from laigu lake which is a proglacial lake located in the headwaters of the parlung zangbo river the largest tributary of the brahmaputra river to reflect glacial activities over the last 8000 years in this area samples of the sediment core were analyzed for magnetic susceptibility xrf x ray florescence scanned elemental concentration and grain size the results indicated that the magnetic susceptibility and cps peak area counts per second of strontium sr could be used as proxies for glacial activity the cps of sr and the magnetic susceptibility were lower and the glacial activity was weak before 4 3 cal ka bp expansion of the glaciers in this area began from 4 3 cal ka bp and continued to develop after 3 3 cal ka bp from 2 2 cal ka bp to 1 6 cal ka bp the glaciers retreated substantially followed by another development period until the onset of modern global warming based on our findings and other climate records we concluded that glacial activity in the southeastern tibetan plateau areas was mainly influenced by northern hemisphere temperatures and summer insolation over a sub orbital time scale but did not respond to the indian monsoon

bayesian inversion of joint sh seismic and seismoelectric data to infer glacier system properties abstract in glacial studies properties such as glacier thickness and the basement permeability and porosity are key to understand the hydrological and mechanical behaviour of the system the seismoelectric method could potentially be used to determine key properties of glacial environments here we analytically model the generation of seismic and seismoelectric signals by means of a shear horizontal seismic wave source on top of a glacier overlying a porous basement considering a one dimensional setting we compute the seismic waves and the electrokinetically induced electric field we then analyse the sensitivity of the seismic and electromagnetic data to relevant model parameters namely depth of the glacier bottom porosity permeability shear modulus and saturating water salinity of the glacier basement moreover we study the possibility of inferring these key parameters from a set of very low noise synthetic data adopting a bayesian framework to pay particular attention to the uncertainty of the model parameters mentioned above we tackle the resolution of the probabilistic inverse problem with two strategies 1 we compute the marginal posterior distributions of each model parameter solving multidimensional integrals numerically and 2 we use a markov chain monte carlo algorithm to retrieve a collection of model parameters that follows the posterior probability density function of the model parameters given the synthetic data set both methodologies are able to obtain the marginal distributions of the parameters and estimate their mean and standard deviation the markov chain monte carlo algorithm performs better in terms of numerical stability and number of iterations needed to characterize the distributions the inversion of seismic data alone is not able to constrain the values of porosity and permeability further than the prior distribution in turn the inversion of the electric data alone and the joint inversion of seismic and electric data are useful to constrain these parameters as well as other glacial system properties furthermore the joint inversion reduces the uncertainty of the model parameters estimates and provides more accurate results

diatom oxygen isotopes in pro glacial lake sediments from northern sweden a 5000 year record of atmospheric circulation we use a pro glacial oxygen isotope record of diatom silica 18odiatom and a sedimentary proxy for glacier flutuations to determine centennial millennial scale climate change during the last 5000

holocene multi proxy environmental reconstruction from lake hakluytvatnet amsterdamoya island svalbard 79 5 n high resolution proxy records of past climate are sparse in the arctic due to low organic production that restricts the use of radiocarbon dating and challenging logistics that make data collection difficult here we present a new lake record from lake hakluytvatnet at amsterdamoya island 79 5 n the northwesternmost island on svalbard multi proxy analyses of lake sediments in combination with geomorphological mapping reveal large environmental shifts that have taken place at amsterdamoya during the holocene a robust chronology has been established for the lake sediment core through 28 ams radiocarbon ages and this gives an exceptionally well constrained age control for a lake at this latitude the holocene was a period with large changes in the hakluytvatnet catchment and the onset of the neoglacial ca 5 ka marks the start of modern day conditions in the catchment the neoglacial is characterized by fluctuations in the minerogenic input to the lake as well as internal productivity and we suggest that these fluctuations are driven by atmospherically forced precipitation changes as well as sea ice extent modulating the amount of moisture that can reach hakluytvatnet

a complete record of holocene glacier variability at austre okstindbreen northern norway an integrated approach arctic glaciers are currently undergoing major changes but accurate knowledge about how they varied during the entire holocene is still scarce here we present a new complete glacier record from austre okstindbreen in nordland northern norway this reconstruction is based on a number of short and long cores retrieved from several downstream basins which have been analyzed by a suite of methods including geochemical elements xrf rock magnetic properties dry bulk density dbd and loss on ignition loi lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar gpr independently lichen dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210pb dated lake sediment chronology this integrated approach reveals that austre okstindbreen is the first known glacier in scandinavia to possibly have survived the holocene thermal optimum it also brackets the four largest glacier advances to c 7400 7000 1400 1200 900 700 and 300 150 years before ad 2000 b2k in contrast to most reconstructed glaciers in scandinavia the largest glacier advance was not associated with the little ice age but rather to an earlier period centred at 1300 b2k both the moraine chronology and the lacustrine records document this neoglacial advance compared to other glacier reconstructions from the northern hemisphere we identify near synchronous glacier advances occurring roughly at 4000 b2k 2700 b2k 1300 b2k and during the little ice age these correlative advances across the northern hemisphere suggest that these observed centennial scale events are a shared feature regardless of the large geographical distances separating them some minor discrepancies between different geographical areas may be caused by lack of precise dating but local climatic conditions may play a role as well

slow retreat of a land based sector of the west greenland ice sheet during the holocene thermal maximum evidence from threshold lakes at paakitsoq abstract records from two connected proglacial threshold lakes at paakitsoq west greenland have been analyzed in order to investigate the response of a land based ice sheet margin to holocene climate change the results are used to test whether or not the land terminating margin at paakitsoq behaved synchronously with the nearby marine terminating jakobshavn isbrae during the holocene the radiocarbon dated lake sediment cores indicate that the ice margin retreated to its present position 6 5 ka ago and thereafter maintained a relatively stable configuration similar to the present for 1000 years despite summer temperatures 2 c higher than today the lakes became non glacial after 5 4 cal ka bp when the ice margin retreated behind a drainage divide situated 1 5 km inland of the present margin by this time jakobshavn isbrae had already reached its minimum configuration the paakitsoq ice margin remained 1 5 km inland of its present margin until after 240 20 cal yr bp after this time both paakitsoq ice margin and jakobshavn isbrae reached their holocene maxima during the later stage of the little ice age our results suggest that the present ice margin position at paakitsoq is relatively stable in a warming climate but after a total retreat of 1 5 km behind the present margin position it may become marine based and more unstable due to marine melting and calving processes

millennial scale climate changes on south georgia southern ocean abstract the location of south georgia 54 s 36 w makes it a suitable site for the study of the climatic connections between temperate and polar environments in the southern hemisphere because the mass balance of the small cirque glaciers on south georgia primarily responds to changes in summer temperature they can provide records of changes in the south atlantic ocean and atmospheric circulation we use grey scale density weight loss on ignition and grain size analyses to show that the proportion of glacially eroded sediments to organic sediments in block lake was highly variable during the last 7400 cal yr b p we expect that the glacial signal is clearly detectable above noise originating from nonglacial processes and assume that an increase in glacigenic sediment deposition in block lake has followed holocene glacier advances we interpret proglacial lake sediment sequences in terms of summer climate warming and cooling events prominent millennial scale features include cooling events between 7200 and 7000 5200 and 4400 and 2400 and 1600 cal yr b p and after 1000 cal yr b p comparison with other terrestrial and marine records reveals that the south georgian record captures all the important changes in southern hemisphere holocene climate our results reveal a tentative coupling between climate changes in the south atlantic and north atlantic because the documented temperature changes on south georgia are anti phased to those in the north atlantic

temporal evolution of sediment supply in lago puyehue southern chile during the last 600 yr and its climatic significance short term climate changes in southern chile are investigated by a multi proxy analysis of a 53 cm long sedimentary sequence selected among eight short cores retrieved in lago puyehue chile 40 s this core contains a 600 yr long undisturbed record of paleo precipitation changes two measurement methods for sediment density organic matter and biogenic silica contents are compared and the most appropriate techniques are selected together with aluminium and titanium concentrations grain size and geochemical properties of the organic matter these proxies are used to demonstrate paleo precipitation changes around 40 s increase of terrigenous particle supply between a d 1490 and a d 1700 suggests a humid period contemporaneously y 13 c data show increasing lake productivity in response to the high nutrient supply the a d 1700 1900 interval is characterized by a decreasing terrigenous supply and increasing y 13 c values interpreted as a drying period the magnetic susceptibility signal reflecting the terrigenous biogenic ratio demonstrates that similar variations occur in all the undisturbed sedimentary environments of lago puyehue the a d 1490 1700 wet period is associated with the onset of the european little ice age lia andinterpreted asits local signature this worksupports the fact that the liawasaglobal event not only restricted to thenorthern hemisphere d 2005 university of washington all rights reserved

paleomagnetic data from the redding section of the eastern klamath belt northern california a paleomagnetic analysis of units of devonian to triassic age within the redding section of the eastern klamath mountains indicates clockwise rotation of 83 116 with respect to stable north america in the kinematic model presented here shear zones within the franciscan complex with separation antithetic to the san andreas are used to effect this rotation

a high resolution 1200 year lacustrine record of glacier and climate fluctuations in lofoten northern norway here we present the first high resolution late holocene glacier record from the lofoten archipelago in northern norway the study is based on analyses of lacustrine sediments from the distal glacier fed lake kveitvikvatnet 30 1 m a s l as well as glacial geomorphological mapping of the 4 2 km2 surrounding catchment the lake sediment cores have been examined for input of glacial derived sediments by using physical geochemical and magnetic sediment properties including x ray fluorescence xrf magnetic susceptibility ms grain size analyses dry bulk density dbd and loss on ignition loi former glacier extent has been reconstructed using aerial photography and glacial geomorphological mapping lichenometric dating has been used to construct a moraine chronology covering the recent fluctuations of the largest glacier back to ad 1740 ams radiocarbon dating reveals that the lake sediment record covers the last 1200 years thereby including both the little ice age lia and the medieval cl

rapid early holocene environmental changes in northern sweden based on studies of two varved lake sediment sequences mineral magnetic organic carbon and pollen studies of two varved holocene lake sediment sequences in the boreal forest of northern sweden indicate that significant environmental changes took place between c 6000 and 5700 bc this interval is characterized by an increase in mineral matter accumulation which is a proxy for winter snow accumulation and a statistically significant decrease in total pollen influx predominantly pinus betula and alnus which may reflect lower spring and summer temperatures and increased frost frequency notable increases in the influx of deciduous tree species including quercus and corylus suggest a rapid change to warmer conditions between 5700 and 5600 bc given dating errors associated with the varve chronologies and the greenland ice core timescales the cold interval can be considered to reflect a regional possibly global climatic cooling which is often referred to as the 8 2 kyr bp cooling event however the younger age of the cold event in northern sweden does not support the hypothesis of forcing by the sudden drainage of laurentide glacial lakes into the north atlantic unless a minimal 300 year delay in ocean atmospheric coupling is accepted the data contribute to a complex picture of early holocene environmental change in response to deglaciation of the northern hemisphere

reconstruction of glacier variability from lake sediments reveals dynamic holocene climate in svalbard abstract the arctic is warming faster than anywhere else on earth holocene proxy time series are increasingly used to put this amplified response in perspective by understanding arctic climate processes beyond the instrumental period however available datasets are scarce unevenly distributed and often of coarse resolution glaciers are sensitive recorders of climate shifts and variations in rock flour production transfer this signal to the lacustrine sediment archives of downstream lakes here we present the first full holocene record of continuous glacier variability on svalbard from glacier fed lake hajeren this reconstruction is based on an undisturbed lake sediment core that covers the entire holocene and resolves variability on centennial scales owing to 26 dating points a toolbox of physical geochemical xrf and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint glacier activity in addition to other processes affecting the sediment record evidence from variations in sediment density validated by changes in ti concentrations reveal glaciers remained present in the catchment following deglaciation prior to 11 300 cal bp culminating in a holocene maximum between 9 6 and 9 5 ka cal bp correspondence with freshwater pulses from hudson strait suggests that early holocene glacier advances were driven by the melting laurentide ice sheet lis we find that glaciers disappeared from the catchment between 7 4 and 6 7 ka cal bp following a late hypsithermal glacier reformation around 4250 cal bp marks the onset of the neoglacial supporting previous findings between 3380 and 3230 cal bp we find evidence for a previously unreported centennial scale glacier advance both events are concurrent with well documented episodes of north atlantic cooling we argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling these findings highlight the climate sensitivity of the small glaciers studied which rapidly responded to climate shifts the start of prolonged neoglacial glacier activity commenced during the little ice age lia around 700 cal bp in agreement with reported advances from other glaciers on svalbard in conclusion this study proposes a three stage holocene climate history of svalbard successively driven by lis meltwater pulses episodic atlantic cooling and declining summer insolation

environmental magnetism past present and future environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport deposition or transformation of magnetic grains is influenced by environmental processes in the atmosphere hydrosphere and lithosphere the first explicit description of environmental magnetism as a distinct field was in 1980 since that time environmental magnetism has become a broad field that is finding application in an ever increasing array of scientific disciplines in this review of the present state of environmental magnetic studies we divide the field into three broad but arbitrary categories the first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments this category includes the correlation of sediment cores using magnetic susceptibility measurements studies of geomagnetic field behavior the analysis of depositional and postdepositional mechanical processes that affect sediments and the examination of magnetic parameters that might represent proxies for paleoclimatic variation the second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment these provenance investigations include studies of changes in catchment derived sediment in lakes fluctuations in contributions from terrigenous aeolian and glaciogenic components in deep sea sediments and the origin of atmospheric particulates the final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments including pedogenesis authigenetic diagenetic formation of ferrimagnetic phases dissolution of magnetic minerals due to reductive diagenesis and contributions of biomagnetism to sedimentary magnetism because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques it is likely that the scope of environmental magnetism will continue to expand rapidly environmental magnetism is capable of providing important data for studies of global environmental change climatic processes and the impact of humans on the environment all of which are major research initiatives in the international scientific community these factors suggest that environmental magnetism has a bright and diverse future

reconstruction of former glacier equilibrium line altitudes based on proglacial sites an evaluation of approaches and selection of sites abstract various approaches are used to record variations in glacier activity and equilibrium line altitudes elas based on proglacial sites lacustrine and terrestrial these approaches are based on a conceptual model of glacier meltwater induced sedimentation in which the minerogenic nonorganic component of the sediments is related to the occurrence of a glacier in the catchment the principal coupling to former glacier activity and elas is common for these approaches however different methods and techniques may complement each other and both possibilities and limitations are demonstrated site selection for reconstructing variations in glacier activity elas is evaluated and critical factors are discussed rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on off signal for former glacier activity elas together with representative lateral moraines of known age local watersheds are important for calibrating reconstructed glacier activity elas based on a chain of proglacial lakes based on the modern analogue principle various proxies can record whenever glaciers existed in a catchment in a chain of proglacial lakes with different sensitivity to record variations in glacier activity elas these proxies can be calibrated against independent records for one site approaches however variations in glacier activity elas depend on the interpretation and sensitivity of the proxies used

palaeoglaciology of an ice sheet through a glacial cycle the european ice sheet through the weichselian abstract satellite images provide unique means of identifying large scale flow generated lineations produced by former ice sheets they can be interpreted to reconstruct the major elements which make up the integrated large scale structure of ice sheets ice divides ice streams interstream ridges ice shelves calving bays the evolving palaeoglaciological structure of the european ice sheet during its decay from the last glacial maximum lgm is reconstructed by reference to these components and in the context of a new map showing isochrons of retreat during the retreat phase in particular the time dependent dynamic evolution of the ice sheet and the pattern of ice stream development are reconstructed crossing lineations are widespread the older ones are suggested to have formed during molten bed phases of ice sheet growth and preserved by frozen bed conditions during the glacial maximum particularly in areas which lay during deglaciation beneath ice divides and inter ice stream ridges both areas of slow flow and possibly frozen bed conditions four phases of growth a1 to a4 and five phases of decay r1 to r5 are used to describe the major climatically and dynamically determined stages in the evolution of the ice sheet through the last glacial cycle the growth and decay patterns are quite different and associated with major shifts in the ice divide reflecting growth from the fennoscandian mountains and decay away from marine influenced margins these patterns were determined by the locations of nucleation areas spatial patterns of climate and calving at marine margins the prevalence of streaming within the retreating ice sheet suggests that the mean elevation of the ice sheet was lower than predicted from glaciological models which do not include streaming and that this might reconcile glaciological models and earth rheology models which infer paleao ice sheet thickness by inverting sea level data

holocene glacier history of bjornbreen and climatic reconstruction in central jotunheimen norway based on proximal glaciofluvial stream bank mires abstract holocene variations of bjornbreen smorstabbtinden massif west central jotunheimen are reconstructed from the lithostratigraphy of two alpine stream bank mires flooded episodically by meltwater the approach uses multiple sedimentological indicators weight loss on ignition mean grain size grain size fractions bulk density moisture content and magnetic susceptibility an a priori model of overbank deposition of suspended glaciofluvial sediments a detailed chronology based on 56 radiocarbon dates and a little ice age sedimentological analogue rapid late preboreal deglaciation was indicated by immigration of betula pubescens by 9700 cal bp an interval of at least 3000 years in the early holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the finse event the first at ca 8270 7900 cal bp bjornbreen i event and the second at ca 7770 7540 cal bp bjornbreen ii event neoglaciation began shortly before ca 5730 cal bp with gradual build up to the maximum of the bjornbreen iii event at ca 4420 cal bp later maxima occurred at ca 2750 cal bp bjornbreen iv event and at 1300 1260 1060 and 790 cal bp all within the bjornbreen v event glaciers were smaller than today and possibly melted away on several occasions in the late holocene ca 3950 1410 and 750 cal bp minor maxima also occurred at ca 660 and 540 cal bp within the late mediaeval warm period and the early little ice age respectively the little ice age maximum was dated to 213 25 bp ca 205 cal bp the relative magnitudes of the main glacier maxima were determined erdalen event little ice age event bjornbreen vi bjornbreen i finse event bjornbreen ii bjornbreen v bjornbreen iv bjornbreen iii these episodic events of varying magnitude and abruptness were used in conjunction with an independent summer temperature proxy to reconstruct variations in equilibrium line altitude ela and a holocene record of winter precipitation since the preboreal ela varied within a range of about 390 m and winter precipitation ranged between 40 and 160 of modern values winter precipitation variations appear to have been the main cause of these century to millennial scale holocene glacier variations

influence of geomorphological setting fluvial glaciofluvial and mass movement processes on sedimentation in alpine lakes lacustrine sediments are often used for paleoclimate reconstructions as continuous archives of several physical and biological proxies the relation between autochthonous and allochthonous sedimentation in alpine lakes is a complex system that may cause difficulties when interpreting biological and physical parameters results from previous studies of alpine lakes in northern sweden have demonstrated that non glacial processes produce minerogenic lake deposits with similar physical characteristics density loi magnetic susceptibility grain size as those that have been associated with glacier fluctuations in proglacial lakes in this study of two consecutive proglacial alpine lakes we show that fluvial redeposition of alluvial fan deposits significantly affects the holocene lake sedimentation depending on the geomorphological setting such fluvial redeposition signals may actually overprint a glaciofluvial signal we also show that minerogenic laminations of fluvial origin are impossible to separate f

restricted impact of holocene climate variations on the southern greenland ice sheet abstract we use an ice marginal threshold lake lower nordboso in southern greenland to record episodes when the southern greenland ice sheet sgis was close to the present extent represented by beds of clastic sediments whereas gyttja deposition reflects periods when the glacier was behind the threshold and no glacial meltwater input the results show that the sedimentation was initiated at c 10 6 cal ka bp when the ice margin had reached the present extent following the deglaciation after this the ice margin remained close to the present extent until c 6 9 cal ka bp when it retreated behind the threshold and first reappeared with a clear glacial signal at c 3 0 2 8 cal ka bp and from c 0 5 cal ka bp until the present an overall good correlation between clastic input into lower nordboso and ird events from narsaq sound suggests that they represent a general glacial proximity signal of the sgis our data demonstrates that the sgis behaved less vigorously to holocene climate changes compared to previous reconstructions the ice sheet only retreated behind the present ice extent from c 6 9 to 3 0 cal ka bp and c 2 8 to 0 5 cal ka bp in the mountainous southern greenland whereas the more sensitive low lying qassimiut lobe was behind its present margin from c 9 ka until the little ice age accordingly the ice marginal behavior in southern greenland is not only governed by climate changes but also strongly influenced by the local topographic setting

extension tectonics the neogene opening of the north south trending basins of central thailand paleomagnetic samples were collected from late neogene basalt flows from thailand all of these flows are horizontal and are relatively unaltered in thin section these rocks possess a stable magnetization which is believed to be primary samples from 48 lava flows were collected from sites located within the khorat plateau the chao phraya phitsanulok basin and the mountainous terrane west of the chao phraya phitsanulok basin these data were combined with previously reported late neogene data from five flows from western thailand although the average inclination from the 53 sites is indistiguishable from the expected dipole inclination the average declination has a net clockwise rotation of 13 5 5 8 from the geocentric dipole field furthermore the mean declination values from the 29 flows from the khorat plateau are indistinguishable from the present dipole field direction dm 4 3 7 5 and indistinguishable from the mean declination from 28 late neogene volcanic flows from vietnam in contrast the mean declinations from 24 flows collected from central and western thailand are deflected significantly clockwise dm 24 4 7 7 from the geocentric dipole field direction the differential rotation between western and central thailand versus the khorat plateau suggests that indochina is composed of at least two structural blocks which underwent a different rotational history these observations when combined with geologic and geophysical data from the chao phraya phitsanulok basin gulf of thailand and the intermontane basins of western thailand suggest that the rotations are recording a late neogene phase of e w extension of these basins we suggest that the formation of these basins and the related basaltic volcanism developed in reponse to subduction of the indian plate under western burma we envision the tectonics of this region is similar in style to the basin and range region of the western united states last we have observed field relationships from some of the rhyolites located in the central basin although these rhyolites are reported to be mesozoic or paleozoic in age our field observations and a k ar age date show that at least some of these rhyolites are younger than the basalts we suggest that the rhyolites form a bimodal suite with the basaltic rocks which were erupted in the later stages of the extension

holocene changes in atmospheric circulation recorded in the oxygen isotope stratigraphy of lacustrine carbonates from northern sweden the oxygen isotope composition of local precipitation delta 18 o p is reconstructed from carbonate lake sediment components in a sediment core covering the last 10000 calendar years from lake tibetanus a small hydrologically open groundwater fed take in the abisko area northern sweden comparison of the delta 18 o p history with a pollen based palaeotemperature record from the same core clearly reveals pronounced deviations from the normally expected temporal delta 18 o p temperature relation so called dansgaard relation that may be a function of changing oceanicity the transition from relatively moist maritime conditions in the early holocene to a much drier climate after 6500 cal bp is reflected by major changes in forest extent and composition as recorded by pollen and plant macrofossil data at the time of maximum influence of westerly air mass circulation high zonal index c 9500 cal bp brought about by high summer insolation and enhanced meridional pressure gradients delta 18 o p at lake tibetanus was about 2 higher than would be predicted by the modem isotope temperature relation the occurrence of long term changes in delta 18 o p temperature relations which are more sensitive measures of palaeoclimate than either delta 18 o p or temperature alone needs to be taken into account when extracting palaeoclimatic information from continental oxygen isotope records less

fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model the evolution of ice sheet configuration and flow pattern in fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model i e a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets the model uses mapped flow traces and deglacial melt water landforms as well as relative chronologies derived from cross cutting striae and till lineations as input data flow trace systems were classified into four types i time transgressive wet bed deglacial fans ii time transgressive frozen bed deglacial fans iii surge fans and iv synchronous non deglacial event fans using relative chronologies and aggregation of fans into glaciologically plausible patterns a series of ice sheet configurations at different time slices was erected a chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume geological evidence exists for several discrete ice sheet configurations centred over the scandinavian mountain range during the early weichselian the build up of the main weichselian fennoscandian ice sheet started at approximately 70 ka and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern norway this configuration had a flow pattern which is poorly reproduced by current numerical models of the fennoscandian ice sheet at the last glacial maximum the main ice divide was located overthe gulf of bothnia a major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the scandinavian mountain chain widespread areas of preserved pre late weichselian landscapes indicate that the ice sheet had a frozen bed core area which was only partly diminished in size by inward transgressive wet bed zones during the decay phase

a laboratory seismoelectric measurement for the permafrost model with a frozen unfrozen interface 1 in this study a laboratory seismoelectric measurement for the permafrost model with a frozen unfrozen interface is presented the measurements obtained experimentally confirms that an electric double layer can be formed at the interface due to the electric and mechanical differences of the frozen and unfrozen media and seismoelectric conversion em waves originted from the relative motion of the charges in the electric double layer can be observed at n 10 khz frequency band this suggests a potential application for non destructive detection of the frost depth

geophysical applications of electrokinetic conversion in volume 1 of geophysics 1936 r r thompson of humble oil and refining company proposed that the coupling of seismic and electrical energy can be used as an exploration tool subsequent efforts were directed toward using electric field antennas as geophones small scale studies concluded that antennas are not as sensitive as conventional geophones and their response is highly variable depending on the local soil conditions by 1959 martner and sparks of pan american petroleum reported in geophysics a systematic study of seismoelectric coupling using explosives at various depths their results were the first to show that the conversion of seismic to electromagnetic energy at the water table could be detected using surface antennas no studies have systematically explored the full potential of electroseismic methods using the same level of experimental sophistication used in seismic exploration

use of lacustrine sedimentary sequences as indicators of holocene glacial history banff national park alberta canada abstract bottom sediments from three lakes in the canadian rocky mountains were examined with the aim of evaluating the usefulness of downvalley sediment studies in reconstruction of holocene glacial histories analyses of organic carbon and carbonate contents of core sediments provide information on changing sedimentation rate and changing relative importance of glacial and non glacial sediment sources sedimentary histories of the three lakes are similar suggesting that they record regional glacial climatic forcing rather than localized events and thus that they may be useful in reconstructing holocene glacial history lacustrine sediments indicate a period of high sedimentation rates and relatively large glacial sediment contribution prior to 7500 7000 yr b p with much reduced rates and decreased glacial sediment contribution between about 6000 and 4000 yr b p possibly interrupted by a brief period of increased glacial sediment output shortly after 5000 yr b p sometime after 4000 yr b p sedimentation rates and glacial sediment output began to rise again reaching approximately present levels by 2750 2650 yr b p and have not since returned to low mid holocene levels in detail over the last 3000 yr there is some indication of a slight decrease in sedimentation rate for more than 1000 yr after about 2200 yr b p sedimentation rates and glacial sediment input into all three lakes rose between about 900 and 750 yr b p and have remained very high since if the lake sediments are interpreted as a proxy record of upvalley glacial activity they allow the development of a glacial chronology which is at once generally consistent with and more complete and easily datable than the surficial glacial record

late holocene glacier reconstruction reveals retreat behind present limits and two stage little ice age on subantarctic south georgia observational data show that climate in the southern ocean region is rapidly changing however past the instrumental period our understanding of climate variability in the region is limited by a scarcity of highresolution palaeoclimate records alpine glaciers present on many southern ocean islands may provide such data because changes in their mass balance extent and erosion rates often mark a response to climate shifts rock flour the fine grained fraction of the glacial erosion process is suspended in meltwater streams and transferred into the sediments of downstream lakes continuously recording glacier variations here we utilize this relationship to present a reconstruction of the late holocene glacier history of subantarctic south georgia using sediments from the glacier fed middle hamberg lake to fingerprint a glacial erosion size signal we used titanium counts validated against changes in sediment density and grain size allowing a continuous reconstruction of glacier variations over the past similar to 1250 years together with local moraine evidence and supporting evidence from other southern hemisphere glaciers on new zealand and in patagonia our findings reveal a series of consecutively diminishing late holocene advances in addition to a glacier maximum before 1250 cal a bp these include a twostage litle ice age with advances around 300 and 120 cal a bp in line with evidence from southern patagonia in addition we present evidence for an unreported retreat behind present limits around 500 cal bp

arctic holocene glacier fluctuations reconstructed from lake sediments at mitrahalvoya spitsbergen the arctic region has experienced a significantly larger warming during the last decades compared to the rest of the world and model simulations indicate a continued amplification of future global warming in the polar regions a better understanding of natural climate variability in the arctic is much needed to provide a better context for the observed warming trend by utilising proxy data it is possible to obtain palaeoclimatic records beyond the range of instrumental observations which increase our understanding of long term arctic climate change here a continuous record of past changes in equilibriumline altitude ela has been reconstructed for the alpine glacier karlbreen located on the northwest coast of spitsbergen 79 n based on sediment analyses from a distal glacier fed lake a multivariate statistical analysis suggests that the concentration of geochemical elements ti si and k in the lake sediments together with the physical parameter dry bulk density dbd reflect changes in the amount of inorganic detrital input to klosa which is closely linked to the size and ela of the upstream glacier karlbreen a linear regression model based on historically documented glacier extents was used to calculate continuous ela changes back to 3500 cal yr bp from about 9200 to 3500 cal yr bp the sedimentary record indicates that karlbreen was very small or had completely melted away karlbreen was probably close to its maximum holocene extent several times during the neoglacial first around 1700 cal yr bp then later at 225 and 135 cal yr bp an ice cored moraine system in front of karlbreen extends well into the main basin of klosa and it is difficult to explain how this moraine could have formed without disturbing the sedimentary record in the lake e g through slumping events the sedimentary record in klosa is continuous and undisturbed over the past 6700 years suggesting that the outermost moraine formed prior to this time and that it most likely survived the holocene thermal maximum on svalbard

seismoelectric and seismomagnetic measurements in fractured borehole models seismoelectric and seismomagnetic fields generated by seismic waves in fluid saturated fractured borehole models are experimentally investigated with an electrode and a hall effect sensor in a borehole with a horizontal fracture the stoneley and flexural waves induce seismoelectric and seismomagnetic fields on the borehole wall and an electromagnetic wave propagating at light speed at the horizontal fracture in a borehole with a vertical fracture the acoustic field generated by a monopole or dipole source is similar to that in a borehole without a vertical fracture however the acoustic wave propagating along the vertical fracture induces seismoelectric and seismomagnetic fields whose apparent velocities are equal to that of a stoneley wave experimental results show that two different kinds of electric and magnetic fields are generated by acoustic waves in borehole models with horizontal and or vertical fractures one is an electromagnetic wave propagating with light speed the second is a stationary or localized seismoelectric and seismomagnetic field seismoelectric and seismomagnetic measurements might be a new logging technique for exploring fractures in a borehole

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around