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

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

holocene glacier activity reconstructed from proglacial lake gjoavatnet on amsterdamoya nw svalbard well dated and highly resolved paleoclimate records from high latitudes allow for a better understanding of past climate change lake sediments are excellent archives of environmental change and can record processes occurring within the catchment such as the growth or demise of an upstream glacier here we present a holocene length multi proxy lake sediment record from proglacial lake gjoavatnet on the island of amsterdamoya northwest svalbard today gjoavatnet receives meltwater from the annabreen glacier and contains a record of changes in glacier activity linked to regional climate conditions we measured changes in organic matter content dry bulk density bulk carbon isotopes elemental concentrations via itrax core scanning and diatom community composition to reconstruct variability in glacier extent back through time our reconstruction indicates that glacially derived sedimentation in the lake decreased markedly at 11 1 cal kyr bp although a glacier likely persisted in the catchment until 8 4 cal kyr bp during the mid holocene 8 4 1 0 cal kyr bp there was significantly limited glacial influence in the catchment and enhanced deposition of organic rich sediment in the lake the deposition of organic rich sediments during this time was interrupted by at least three multi centennial intervals of reduced organic matter accumulation 5 9 5 0 2 7 2 0 and 1 7 1 5 cal kyr bp considering our chronological information and a sedimentological comparison with intervals of enhanced glacier input we interpret these intervals not as glacial advances but rather as cold dry episodes that inhibited organic matter production in the lake and surrounding catchment at 1 0 cal kyr bp input of glacially derived sediment to gjoavatnet abruptly increased representing the rapid expansion of the annabreen glacier

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

over 400 previously undocumented svalbard surge type glaciers identified abstract identifying glaciers that exhibit surge type behavior is important when using evidence of ice front fluctuations as a proxy for reconstructing past climate oscillations this study identifies previously undocumented surge type glaciers in svalbard based on the presence of crevasse squeeze ridges in glacier forelands crevasse squeeze ridges are landforms suggested to be unique to surging glacier land systems estimates vary greatly as to the actual percentage of surge type glaciers in svalbard and consequently their distribution pattern is poorly understood a detailed survey of recent 2008 2012 high resolution aerial imagery from toposvalbard provided by the norwegian polar institute allowed for a survey of all the glacier forelands in svalbard before our study 277 individual glaciers in svalbard have been documented to exhibit surge behavior by using crevasse squeeze ridges as indicators of surge behavior we have identified 431 additional glaciers that have surged we suggest that this is a modest value as the unique surge landforms were not visible in approximately one third of the forelands with documented surge histories limits to the crevasse squeeze ridge technique are presented and potential controlling factors for crevasse squeeze ridge formation preservation are discussed

synchronizing ice cores from the renland and agassiz ice caps to the greenland ice core chronology 1 four ice cores from the agassiz ice cap in the canadian high arctic and one ice core from the renland ice cap in eastern greenland have been synchronized to the greenland ice core chronology 2005 gicc05 which is based on annual layer counts in the dye 3 grip and ngrip ice cores volcanic reference horizons seen in electrical conductivity measurements ecm have been used to carry out the synchronization throughout the holocene the agassiz ice cores have been matched to the ngrip ice core ecm signal while the renland core has been matched to the grip ice core ecm signal thus tying the cores to gicc05 furthermore it has been possible to synchronize the renland ice core to ngrip gicc05 in the glacial period back to 60 000 years b2k years before a d 2000 on the basis of a matching of transitions between stadials and interstadials this work brings the total number of ice core records that have been rigorously tied to the gicc05 timescale up to nine renland annual layer thicknesses are increasing with depth during the period from 7 to 8 5 ka b2k a highly unusual observation only matched by a similar thickness increase in the glacial section of the renland core some 60 ka ago annual layer thicknesses in the agassiz ice cores point to a well developed raymond bump in the agassiz ice cap

episodic neoglacial snowline descent and glacier expansion on svalbard reconstructed from the 14c ages of ice entombed plants abstract the response of the northern hemisphere cryosphere to the monotonic decline in summer insolation and variable radiative forcing during the holocene has been one of irregular expansion culminating in the little ice age when most glaciers attained their maximum late holocene dimensions although periods of intervening still stand or ice retreat can be reconstructed by direct dating of ice recessional features defining times of neoglacial ice growth has been limited to indirect proxies preserved in distal archives here we report 45 precise radiocarbon dates on in situ plants emerging from beneath receding glaciers on svalbard that directly date the onset of snowline descent and glacier expansion entombing the plants persistent snowline lowering occurred between 4 0 and 3 4 ka but with little additional persistent lowering until early in the first millennium ad populations of individual 14 c calendar age results and their aggregate calendar age probabilities define discrete episodes of vegetation kill and snowline lowering 240 340 ad 410 540 ad and 670 750 ad each with a lower snowline than the preceding episode followed by additional snowline lowering between 1000 and 1220 ad and between 1300 and 1450 ad snowline changes after 1450 ad including the maximum ice extent of the little ice age are not resolved by our collections although snowlines remained lower than their 1450 ad level until the onset of modern warming a time distance diagram derived from a 250 m long transect of dated ice killed plants documents ice margin advances 750 1100 and after 1500 ad concordant with distributed vegetation kill ages seen in the aggregate data set supporting our central thesis that vegetation kill ages provide direct evidence of snowline lowering and cryospheric expansion the mid to late holocene history of snowline lowering on svalbard is similar to ela reconstructions of norwegian and svalbard cirque glaciers and consistent with a cryospheric response to the secular decline of regional summertime insolation and stepped changes in nearby surface ocean environments the widespread exposure of entombed plants dating from the first millennium ad suggests that svalbard s average summer temperatures of the past century now exceed those of any century since at least 700 ad including medieval times

a new late weichselian and holocene marine chronology for the western svalbard slope 30 000 0 cal years bp abstract data have been compiled from eleven sediment cores from 76 to 80 n on the western svalbard slope the cores are from water depths between 630 and 1880 m and show clear similarities in lithology and magnetic susceptibility all cores penetrated into mass transported sediments from glacigenic debris flow events and turbidity flow events the mass transport probably occurred when the ice reached the shelf edge the deposits date between 24 080 150 and 23 550 185 calibrated cal years bp the records also include laminated fine grained sediments interpreted as deposits from sediment laden meltwater plumes dated between 14 780 220 and 14 300 260 cal years bp in holocene sediments a diatom rich fine grained layer dates 10 100 150 to 9840 200 cal years bp the eleven cores have been stacked into one record with absolute age control from 35 ams14c dates together with oxygen isotope stratigraphy and contents of ice rafted detritus the stacked record provides a useful chronology tool for cores on the western svalbard slope our study improves the age control of earlier well documented glacial events and shows that the maximum glacial state and the onset of the deglaciation both occurred 2500 3000 years earlier than previously reconstructed for the western svalbard margin the results indicate that during the last 30 000 years advance and retreat of the svalbard barents sea ice sheet was closely linked to the flow of atlantic water and polar water over the margin

holocene glacial and climatic variations on spitsbergen svalbard holocene glacial and climatic variations have been inferred from investigations of sediment cores from the proglacial lake linnevatnet western spitsbergen a low content of glacially derived coal absence of regular laminations and a slow sedimentation rate in the lower part of the lacustrine sediments indicate that the former glaciers that existed within the catchment area during the last ice age melted quickly away as a result of the younger dryas holocene warming and during the next 6000 years there were no glaciers in the valley increasing coal content incipient laminations and rising sedimentation rates indicate that the glacier linnebreen started to form 4000 5000 years ago probably as a response to the late holocene cooling the holocene maximum extent of the glacier occurred during the little ice age starting with a pronounced ice advance in the thirteenth or fourteenth century a well dated core from billefjorden which is assumed to reflect glacial fluctuations in the inner part of the i

landscape imprints of changing glacial regimes during ice sheet build up and decay a conceptual model from svalbard the behaviour of ice sheets and their geologic imprints in fjord regions are often multifaceted fjords which were temporarily occupied by fast flowing ice streams during major glaciations and inter fjord areas which were covered by less active ice show different signatures of past glaciations the land and marine records of glaciations over the western svalbard fjord region have been extensively studied during the last few decades we have re examined ice flow records from stratigraphic and geomorphic settings and propose a succession of ice flow events that occurred repeatedly over glacial cycles the maximum the transitional and the local flow style the differently topographically constrained segments of the ice sheet switched behaviour as glacial dynamics developed through each glacial cycle these segments as well as the different flow styles are reflected differently in the offshore stratigraphic record we propose that the glacial geomorphological signatures in the inter ice stream areas mostly developed under warm based conditions during a late phase of the glaciations and that the overall glacial imprints in the landscape are strongly biased towards the youngest events

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

high resolution bathymetric mapping reveals subaqueous glacial landforms in the arctic alpine lake tarfala sweden in arctic alpine regions glacio lacustrine environments respond sensitively to variations in climate conditions impacting for example glacier extent and rendering former ice contact lakes into i

magnetostratigraphic evidence that tiny wiggles in the oceanic magnetic anomaly record represent geomagnetic paleointensity variations the oceanic magnetic anomaly record contains low amplitude short wavelength anomalies tiny wiggles or cryptochrons of uncertain source a magnetostratigraphic investigation of their origin has been carried out in a 40 m long core the massicore drilled through the early oligocene grey greenscaglia cinerea marlstone and multi huedscaglia variegata limestone in the marches region of northern italy the massicore contains a complete magnetostratigraphy that matches the geomagnetic polarity sequence from chron c16n to chron c12r it contains no additional short polarity chrons that might account for tiny wiggles the marine magnetic record has several of these events within the chron sequence c13r c13n c12r these chrons fall in the 22 m thickscaglia cinerea part of the massicore this formation has a simple magnetic mineralogy dominated by magnetite and is suitable for paleointensity investigations magnetic susceptibility is rather uniform within the formation and is determined by paramagnetic minerals the intensities of natural nrm anhysteretic arm and isothermal irm remanent magnetizations vary coherently with depth power spectra of the arm irm and nrm variations show significant activity close to the 413 ka period of the earth s orbital elements arm and irm intensities are proportional except in two stratigraphic intervals the ratio of nrm intensity to arm intensity used as a proxy for relative variation of paleomagnetic field intensity fluctuates systematically its minimum values lie close to the reported positions of cryptochrons in the marine record the massicore results favour the interpretation that tiny wiggles represent paleointensity variations of the geomagnetic field rather than unresolved short polarity chrons

holocene paleomagnetic secular variation psv near 80 n northwest spitsbergen svalbard implications for evaluating high arctic sediment chronologies abstract we present a paleomagnetic study of two holocene lake sediment sequences from northwest spitsbergen on svalbard norway core hap 212 from lake hajeren preserves a rare combination of a well defined characteristic remanent magnetization chrm and robust age control defined by 21 terrestrial macrofossil derived radiocarbon dates providing a unique opportunity to assess the stratigraphic potential of high arctic holocene paleomagnetic secular variation psv close to 80 n core amp 112 from hakluytvatnet which is also well dated is a poor magnetic recorder and cannot be used for geomagnetic reconstruction comparison of the hap 212 psv record with poorly dated regional records show similar directional features suggesting that psv can be used for chronological synchronization comparison of the hap 212 psv with well dated records 1800 km to the southwest and southeast show that these records are in phase at millennial timescales within dating and magnetic uncertainties indicating that a consistent geomagnetic signal is recorded at these temporal and spatial scales these findings support the notion that psv when optimally recorded can be used to import chronologies from lower latitudes to the high arctic where low organic content hard water effects lack of datable material and other difficulties often preclude more conventional radiocarbon dating

from mountain top to the deep sea deglaciation in 4d of the northwestern barents sea ice sheet abstract the timing of the deglaciation of the northern barents sea ice sheet bsis documented in terrestrial and offshore records from the svalbard archipelago is reviewed we present new cosmogenic nuclide cn ages from formerly unexplored inland areas of northern svalbard to investigate the timing of thinning of past local ice domes cn data are compared with radiocarbon ages from marine and terrestrial deposits 10be isotope cn dates on erratic boulders from interior svalbard suggest that glacier surfaces in northern and western svalbard thinned 950 650 m from 26 4 ka and continued over an extended period until 16 ka initial ice retreat from the western outer to the inner shelf began at 20 5 ka and in storfjordrenna southwest of svalbard around 19 18 ka retreat of grounded ice from the northern outer to the inner shelf did not begin before 15 9 ka we therefore suggest increasing summer insolation and aridification due to atmospheric circulation changes and perennial sea ice cover as the main mechanisms for the ice thinning and grounded ice retreat from the outer shelves before and during the heinrich 1 event the frontal position of the grounded ice sheet however did not change during several millennia despite further thinning in interior northern svalbard the inner shelf areas rapidly deglaciated towards the fjord mouths along the western coasts between 15 and 14 ka and became ice free before and during meltwater pulse 1a mwp 1a the collapse of the ice shelves from the inner shelf towards the fjord mouths and inner fjords occurred on a decadal to centennial time scale based on overlapping radiocarbon ages from marine sediment cores in addition to cn data from erratic boulders in lowlands we suggest that additional mechanisms must have caused this rapid collapse together with reduced moisture supply in the accumulation areas we assume that subsurface warm atlantic water masses that reached the western shelf after 17 5 ka may have accelerated debuttressing of the ice shelves in addition to the bolling warming that kicked in around 15 1 ka due to increased insolation and the global sea level rise called mwp 1a conservative calculations estimate the contribution of only the northwestern part of the bsis to sea level rise with 0 0004 cm yr 1 between 26 and 16 ka and 0 02 cm yr 1 in assumed 300 years between 15 and 14 ka

utilizing physical sediment variability in glacier fed lakes for continuous glacier reconstructions during the holocene northern folgefonna western norway the maritime plateau glacier of northern folgefonna in western norway has a short subdecadal response time to climatic shifts and is therefore well suited for reconstructing high resolution glac

identifying fracture zone geometry using simulated annealing and hydraulic connection data a new approach is presented to condition geostatistical simulation of high permeability zones in fractured rock to hydraulic connection data a simulated annealing algorithm generates three dimensional 3 d realizations conditioned to borehole data inferred hydraulic connections between packer isolated borehole intervals and an indicator fracture zone or background k bedrock variogram model of spatial variability we apply the method to data from the u s geological survey mirror lake site in new hampshire where connected high permeability fracture zones exert a strong control on fluid flow at the hundred meter scale single well hydraulic packer tests indicate where permeable fracture zones intersect boreholes and multiple well pumping tests indicate the degree of hydraulic connection between boreholes borehole intervals connected by a fracture zone exhibit similar hydraulic responses whereas intervals not connected by a fracture zone exhibit different responses our approach yields valuable insights into the 3 d geometry of fracture zones at mirror lake statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture zone geometries that are consistent with hydraulic test data

the island of amsterdamoya a key site for studying past climate in the arctic archipelago of svalbard abstract this paper introduces a series of articles assembled in a special issue that explore holocene climate evolution as recorded in lakes on the island of amsterdamoya on the westernmost fringe of the arctic svalbard archipelago due to its location near the interface of oceanic and atmospheric systems sourced from arctic and atlantic regions amsterdamoya is a key site for recording the terrestrial response to marine and atmospheric changes we employed multi proxy approaches on lake sediments integrating physical biogeochemical and isotopic analyses to infer past changes in temperature precipitation and glacier activity the results comprise a series of quantitative holocene length paleoclimate reconstructions that reveal different aspects of past climate change each of the four papers addresses various facets of the holocene climate history of north western svalbard including a reconstruction of the annabreen glacier based on the sedimentology of the distal glacier fed lake gjoavatnet a reconstruction of changing hydrologic conditions based on sedimentology and stratigraphy in lake hakluytvatnet reconstruction of summer temperature based on alkenone paleothermometry from lakes hakluytvatnet and hajeren and a hydrogen isotope based hydrological reconstruction from lake hakluytvatnet we also present high resolution paleomagnetic secular variation data from the same lake which document important regional magnetic field variations and demonstrate the potential for use in synchronizing holocene sedimentary records in the arctic the paleoclimate picture that emerges is one of early holocene warmth from ca 10 5 ka bp interrupted by transient cooling ca 10 8ka bp and followed by cooling that mostly manifested as two stepwise events ca 7 and 4 ka bp the past 4ka were characterized by dynamic glaciers and summer temperature fluctuations decoupled from the declining summer insolation

denudation rates in the arctic estimated from lake sediments on spitsbergen svalbard a mean holocene denudation rate of 15 mm 1000 yr is calculated for the high arctic valley linnedalen western svalbard based on estimates of the total volume of lacustrine sediments deposited in lake linnevatnet thirty six sub bottom sediment profiles and 16 sediment cores have been used to map the postglacial sediments stored in the lake these reveal a lower marine unit overlain by lacustrine sediments the base and top of the marine sediments were radiocarbon dated to around 12 300 and 9600 yr b p respectively from isopach maps of the lacustrine unit and the total sediment thickness we calculated 0 9 10 2 km3 of holocene lacustrine sediments and 20 1 10 2 km3 of marine sediments a denudation rate of 15 mm 1000 yr is calculated from the volume of the lacustrine sediments this demonstrates that fluvial erosion does not contribute significantly to the lowering of the landscape in the present climate in contrast glacial erosion rates in nearby areas on svalbard are much higher indicating that glacial erosion by warm based valley glaciers is the most important geomorphic process in the present climate three km of tertiary sediments are postulated to have been removed from central parts of svalbard our denudation rates suggest that this could not have occurred in the present interglacial type of climate we suggest that most of that was removed either in a warmer climate or by glaciers

tracer transport in a stochastic continuum model of fractured media a stochastic continuum model of a fractured medium conditioned on a specific set of field data is developed both the more conductive fractures and the less permeable matrix are generated within the framework of a single continuum stochastic model based on nonparametric indicator geostatistics in the stochastic model the fracture zones are distinguished from the matrix by imposing a long range correlation structure for a small fraction the highest approximately 11 of the hydraulic conductivity in the preferred planes of fracture zones results of flow arid transport simulation in three dimensions 3d are used to illustrate the large spatial variability of point measurements but for spatially integrated quantities the variability is reduced and results become less sensitive to correlation structure therefore it is suggested that spatially integrated quantities may be a more appropriate choice for predicting flow and transport in a strongly heterogeneous medium in that they are more commensurate with the level of our ignorance of the site the issue of spatial variability giving rise to uncertainty in the site characterization of a heterogeneous medium and the prediction of transport results is also addressed simulations are carried out for 3d transport from point tracer sources at hundreds of locations in the medium the breakthrough curve from each point source release is characterized by two parameters the mean transport velocity and the dispersion coefficient the results are presented as a statistical distribution of the transport parameters thus quantifying the uncertainty in predicting flow and transport based on a limited amount of site characterization data

major end moraines of younger dryas age on wollaston peninsula victoria island canadian arctic implications for paleoclimate and for formation of hummocky moraine some of the most extensive and massive end moraines of younger dryas age 11 10 14c ka bp yet recognized in north america occur on wollaston peninsula of victoria island on the western part of the peninsula numerous closely spaced end moraines formed in the interval starting 11 100 100 radiocarbon years ago and ending about 10 500 10 200 years ago net recession was generally slow throughout and was punctuated by moraine building and at least two readvances recession is mapped with a resolution that is approximately decadal the moraines form an orderly nested succession and are consistently associated with westward shedding of meltwater which formed a sequence of marine limit deltas we lack firm independent proxy climate evidence needed to assess whether these moraines formed because of cold younger dryas climate rather than because of controls such as topographic setting and water depth but climatic control seems probable the moraines evidently retain glacier ice cores as do most similarly

rapid oceanic and atmospheric changes during the younger dryas cold period the younger dryas event which began approximately 12 900 years ago was a period of rapid cooling in the northern hemisphere driven by large scale reorganizations of patterns of atmospheric and oceanic circulation 1 3 environmental changes during this period have been documented by both proxy based reconstructions 3 and model simulations 4 but there is currently no consensus on the exact mechanisms of onset stabilization or termination of the younger dryas 5 8 here we present high resolution records from two sediment cores obtained from lake krakenes in western norway and the nordic seas multiple proxies from lake krakenes are indicative of rapid alternations between glacial growth and melting during the later younger dryas meanwhile reconstructed sea surface temperature and salinity from the nordic seas show an alternation between sea ice cover and the influx of warm salty north atlantic waters we suggest that the influx of warm water enabled the westerly wind systems to drift northward closer to their present day positions the winds thus brought relatively warm maritime air to northern europe resulting in rising temperatures and the melting of glaciers subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice which forced the westerly winds back to the south cooling northern europe we conclude that rapid alternations between these two states immediately preceded the termination of the younger dryas and the permanent transition to an interglacial state the impact of freshwater pulses released from northern hemisphere ice sheets on the north atlantic meridional overturning circulation has been suggested as a likely mechanism for the younger dryas cooling 7 11 in addition a responsive sea ice cover has been proposed as a mechanism that could rapidly alter the heat exchange between the ocean and atmosphere during the last glacial period 12 13 the roles of the ocean and the atmosphere in triggering the climate shifts around the younger dryas are much discussed 9 these hypotheses are difficult to resolve partly because the temporal resolution of most palaeoclimate archives is too coarse to enable the anatomy of the younger dryas stadial to be adequately described 14 to address these questions we here present a lake sediment record at sub annual resolution together with new data on the sea surface conditions of the norwegian atlantic current nwac throughouttheyoungerdryasstadial fig 1

the water content of lake sediments and its relationship to other physical parameters an alpine case study the water content of lake sediment cores provides informative data for environmental reconstruction in addition to its usefulness for between core correlation significant nonlinear relationships between water content organic matter and dry density measurements suggest that high resolution records of organic matter and bulk density in alpine lake sediments can be estimated indirectly using water content as a surrogate for bulk density and organic matter data can be collected at much higher temporal scales than possible with current density samplers these results lend further credence to empirical relationships between bulk density water content and organic matter presented elsewhere

ams radiocarbon dating of organic poor lake sediment an example from linnevatnet spitsbergen svalbard ams radiocarbon dating of specific organic fractions is used to evaluate sources of errors in dating of organic poor lake sediment from linnevatnet a proglacial arctic lake dates on un differentiated bulk organic matter are much too old because of contamination from detrital coal attempts to remove coal from other organic matter were only partially successful a consequence of the wide grain size distribution of the coal even if coal contamination is fully removed the bulk of the remaining organic matter is of aquatic origin and is unsuitable for 14c dating because the lake waters are depleted in 14 c due to dissolution of carbonate minerals terrestrial plant macrofossils provide the only reliable material to date the lake sediment however this material is present in sufficient quantity for ams radiocarbon dating only in cores proximal to the main inlet streams paired dates on terrestrial plants and aquatic insects from the same core level and paired dates on modern aquatic and terrestrial vege

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

holocene glacier and climate fluctuations of the maritime ice cap hogtuvbreen northern norway holocene fluctuations of a small outlet glacier from the ice cap hogtuvbreen at 65 n in coastal northern norway are reconstructed based on distal glacier fed lake sediments complemented by a moraine sequence dated by lichenometry glaciers respond to changes in accumulation season precipitation ablation season temperature and redistribution of snow by wind hence reconstructions of glacier fluctuations based on distal glacier fed lakes may give detailed information about past climate at a potentially high temporal resolution yet the importance of any of these climate components is often difficult to solve here we apply the liestol relationship which expresses the relationship between ablation season temperature and annual accumulation of snow at the equilibrium line altitude ela to the reconstructed local temperature precipitation wind ela tpw ela to infer the relative importance of winter balance and ablation season temperature as causes of reconstructed glacier variation the reconstruct

mild little ice age and unprecedented recent warmth in an 1800 year lake sediment record from svalbard the arctic region is subject to a great amplitude of climate variability and is currently undergoing large scale changes due in part to anthropogenic global warming accurate projections of future change depend on anticipating the response of the arctic climate system to forcing and understanding how the response to human forcing will interact with natural climate variations the svalbard archipelago occupies an important location for studying patterns and causes of arctic climate variability however available paleoclimate records from svalbard are of restricted use due to limitations of existing climate proxies here we present a sub decadal to multidecadal scale record of summer temperature for the past 1800 yr from lake sediments of kongressvatnet on west spitsbergen svalbard based on the first instrumental calibration of the alkenone paleothermometer the age model for the high arctic lake sediments is based on 210 pb plutonium activity and the first application of tephrochronology to lake sediments in this region we find that the summer warmth of the past 50 yr recorded in both the instrumental and alkenone records was unmatched in west spitsbergen in the course of the past 1800 yr including during the medieval climate anomaly and that summers during the little ice age lia of the 18 th and 19 th centuries on svalbard were not particularly cold even though glaciers occupied their maximum holocene extent our results suggest that increased wintertime precipitation rather than cold temperatures was responsible for lia glaciations on svalbard and that increased heat transport into the arctic via the west spitsbergen current began ca a d 1600

from field data to fracture network modeling an example incorporating spatial structure this paper describes a technique for processing field data for a fracture network model which accounts for the observed spatial variability this has been done by generating a network subregion by subregion where the properties of each subregion are predicted through geostatistics once the geometry of a particular realization is specified flow through the network is studied we develop the method for a two dimensional analysis based on data from fanay augeres a uranium mine in france we plan to extend the analysis to three dimensions and compare the results with in situ test results in particular we have focused on the data collected in a long section of a drift where fractures have been mapped and steady state permeability tests have been performed in 10 boreholes in order to generate fractures in a statistically heterogeneous region we first divided the region into statistically homogeneous subregions in each subregion and for each fracture set we must specify the areal fracture density and the orientation length and aperture distributions we divided the fractures into five sets based on tectonic history and observed that for each set fractures spaced close together tended to have similar orientations this was built into the simulation an estimate of the aperture distribution for each set was made by assuming that the hydraulic apertures of the fractures intersecting a well test zone were proportional to the fracture opening observed in the core data input to the geostatistical analysis for each set consisted of 16 values of mean length and density of fractures in each 5 m by 2 m section of the drift wall the results of the simulation are tables of values for mean length and fracture density for each of the five sets the value of density simulated for each subregion was used directly to determine the number of fractures to be generated of that set in the subregion the value of mean length was used as the mean of the length distribution in the subregion the local coefficient of variation for length was the same in every subregion using the data described above we generated a 100 m by 100 m fracture network in a series of 100 statistically homogeneous subregions the fractured region generated has a total of 65 740 fractures a 70 m by 70 m region was isolated for directional permeability testing results show that the system is barely connected about 0 1 of the fractures essentially control permeability in the language of percolation theory this mesh is close to the critical density for which infinite clusters of fractures are found problems remaining include that 1 the analysis should be extended to three dimensions 2 the geostatistical simulation and network simulation should be combined rather than used as two separate operations and 3 the nature of flow through single fractures at fanay augeres should be investigated

post glacial relative sea level history of northwestern spitsbergen svalbard the late weichselian and holocene raised beach sequences on northwestern spitsbergen provide a detailed record of sea level oscillations during the last deglacial hemicycle initial emergence commenced at 13 ka coincident with local deglaciation and until 10 5 ka was characterized by a relative slow rate of emergence 1 5 to 5 m ka interrupted by minor stillstands or transgressions associated with possible glacier re advances the orientation of paleo spits and the paucity of whale remains at the late weichselian marinelimit indicate that the prevailing westerly fetch was dampened by a semi permanent sea ice cover allowing long shore drift to predominate a period of accelerated emergence 15 to 30 m ka between 10 5 and 9 ka is correlative with rapid deglaciation of fiords the middle and late holocene is characterized by two brief transgressions one between 6 5 and 5 0 ka that did not exceed 7 m asl and a present probable slow rise in sea level that commenced 2 to 1 ka the strandline tilts in northwestern spitsbergen and the pattern and rate of emergence on svalbard indicate that the maximum glacier loads during the late weichselian were centered on nordaustlandet and on the central and eastern part of the archipelago northwestern and southwestern spitsbergen were marginal to glacial loading and were deglaciated early 13 ka which is presently incompatible with maximum ice sheet extent and the timing and position of deglacial margins recently reconstructed for the barents sea and svalbard mountain ranges and large fiords probably confined major outlet glaciers to the central part of the archipelago preventing inundation of much of western spitsbergen by an inferred large ice sheet based in eastern svalbard and the barents sea

holocene cirque glacier activity in western spitsbergen svalbard sediment records from proglacial linnevatnet holocene glacial variations of a presently ice free cirque in western spitsbergen are inferred from sediment records from the proglacial lake linnevatnet glaciation is indicated in the core records by increased intensity of laminae derived from the cirque inflow and by increase in sediment accumulation rate radiocarbon ages on terrestrial plant macrofossils limit the onset of glaciation in the cirque to within the last six centuries no evidence for earlier glaciation is recognized in the core records indicating that the threshold for glaciation in the cirque was not reached during prior neoglacial advances local climate events favouring glacier expan sion were either of greater magnitude or of longer duration during the little ice age than at any other time during the holocene

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

holocene and latest pleistocene alpine glacier fluctuations a global perspective abstract alpine glacier fluctuations provide important paleoclimate proxies where other records such as ice cores tree rings and speleothems are not available about 20 years have passed since a special issue of quaternary science reviews was published to review the worldwide evidence for holocene glacier fluctuations since that time numerous sites have been discovered new dating techniques have been developed and refined climatic hypotheses have been proposed that contribute to a better understanding of earth s climate system this special volume includes 12 papers on holocene and latest pleistocene alpine glacier fluctuations that update the seven review papers from 1988 major findings of these 12 papers include the following many but certainly not all alpine areas record glacier advances during the younger dryas cold interval most areas in the northern hemisphere witnessed maximum glacier recession during the early holocene with some glaciers disappearing although a few sites yield possible evidence for advances during the 8 2 ka cooling event in contrast some alpine areas in the southern hemisphere saw glaciers reach their maximum post glacial extents during the early to middle holocene in many parts of the globe glaciers reformed and or advanced during neoglaciation beginning as early as 6 5 ka neoglacial advances commonly occurred with millennial scale oscillations with many alpine glaciers reaching their maximum holocene extents during the little ice age of the last few centuries although the pattern and rhythm of these glacier fluctuations remain uncertain improved spatial coverage coupled with tighter age control for many events will provide a means to assess forcing mechanisms for holocene and latest pleistocene glacial activity and perhaps predict glacier response to future impacts from human induced climate change

oceanic and atmospheric variations during the last deglaciation in the fram strait arctic ocean a coupled high resolution organic geochemical and sedimentological study abstract from a high sedimentation rate core obtained from the yermak slope arctic ocean we deduced short term climatic fluctuations of the last deglaciation lasting from 17 000 to 9000 years bp by using a coupled organic geochemical and sedimentological approach we reconstructed near bottom current conditions and assessed their significance in relation with comparable global thermohaline circulation patterns and surface water conditions highest concentrations and fluctuations of specific marine phytoplankton biomarkers were obtained in the bolling allerod when the major deglaciation of the svalbard barents sea ice sheet sbis occurred the marine biomarker record and the sedimentological record are consistent with climate reconstructions obtained from greenland ice cores and thermohaline circulation variations however beginning with the younger dryas yd episode bottom currents decreased during this time period but surface waters remained very productive the atmospheric conditions of the western fram strait reconstructed from biomarker data and thermohaline circulation signals reconstructed from sedimentological data were decoupled in the yd maximum insolation values of solar radiation and fohn like winds enabled open water conditions and increased productivity values in the northern fram strait at least in summer

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

alkenone based reconstructions reveal four phase holocene temperature evolution for high arctic svalbard abstract situated at the crossroads of major oceanic and atmospheric circulation patterns the arctic is a key component of earth s climate system compounded by sea ice feedbacks even modest shifts in the region s heat budget drive large climate responses this is highlighted by the observed amplified response of the arctic to global warming assessing the imprint and signature of underlying forcing mechanisms require paleoclimate records allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming however such datasets are scarce and sparse in the arctic limiting our ability to address these issues here we present two quantitative holocene length paleotemperature records from the high arctic svalbard archipelago situated in the climatically sensitive arctic north atlantic temperature estimates are based on u 37 k unsaturation ratios from sediment cores of two lakes our data reveal a dynamic holocene temperature evolution with reconstructed summer lake water temperatures spanning a range of 6 8 c and characterized by four phases the early holocene was marked by an early onset 10 5 ka cal bp of insolation driven hypsithermal conditions likely compounded by strengthening oceanic heat transport this warm interval was interrupted by cooling between 10 5 8 3 ka cal bp that we attribute to cooling effects from the melting northern hemisphere ice sheets temperatures declined throughout the middle holocene following a gradual trend that was accentuated by two cooling steps between 7 8 7 ka cal bp and around 4 4 4 3 ka cal bp these transitions coincide with a strengthening influence of arctic water and sea ice in the adjacent fram strait during the late holocene past 4 ka temperature change decoupled from the still declining insolation and fluctuated around comparatively cold mean conditions by showing that holocene svalbard temperatures were governed by an alternation of forcings this study improves our understanding of arctic climate dynamics

hydroclimate variability of high arctic svalbard during the holocene inferred from hydrogen isotopes of leaf waxes abstract the response of the arctic hydrologic cycle to global warming includes changes in precipitation patterns and moisture availability associated with variable sea ice extent and modes of atmospheric circulation reconstructions of past hydroclimate changes help constrain the natural range of these systems identify the manners in which they respond to different forcing mechanisms and reveal their connections to other components of the climate system all of which lead to a better understanding of present and future changes here we examine hydroclimate changes during the holocene in the high arctic archipelago of svalbard by reconstructing the isotopic composition of precipitation we measured the hydrogen isotopic composition d values of leaf wax compounds n alkanes c 25 c 31 in a sediment core from lake hakluytvatnet on the island of amsterdamoya northwest spitsbergen we interpret d values of mid chain c 25 and long chain c 29 c 31 length n alkanes to represent changes in the isotopic composition of lake water and precipitation over the last 12 9 ka after deglaciation of the catchment water supply became restricted and the lake experienced significant evaporative isotopic enrichment indicating warmer conditions from 12 8 to 7 5 ka the isotope values suggest an increase in the delivery of moisture from warmer sub polar air masses between 12 8 and 9 5 ka followed by generally warm but unstable conditions between 9 5 and 7 5 ka possibly indicating a response to meltwater forcing sedimentary evidence indicates a hiatus in deposition c 7 5 5 0 ka likely as a result of desiccation of the lake at c 5 0 ka lacustrine sedimentation resumed and over the last 5 ka there was a progressive increase in the influence of polar air masses and colder conditions which culminated in an abrupt shift to colder conditions at c 1 8 ka this late holocene cooling ended c 0 18 ka when isotopic data indicate warmer conditions and greater influence of moisture derived from lower latitudes

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

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

holocene cooling culminates in sea ice oscillations in fram strait a reconstruction of holocene sea ice conditions in the fram strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years bp organic geochemical analyses of sediment cores from eastern and western fram strait enable the identification of variations in the ice coverage that can be linked to changes in the oceanic and atmospheric circulation system by means of the sea ice proxy ip25 phytoplankton derived biomarkers and ice rafted detritus ird increasing sea ice occurrences are traced along the western continental margin of spitsbergen throughout the holocene which supports previous palaeoenvironmental reconstructions that document a general cooling a further significant ice advance during the neoglacial is accompanied by distinct sea ice fluctuations which point to short term perturbations in either the atlantic water advection or arctic water outflow at this site at the continental shelf of east greenland the general holocene cooling however seems to be less pronounced and sea ice conditions remained rather stable here a major neoglacial increase in sea ice coverage did not occur before 1000 years bp phytoplankton ip25 indices pip25 index are used for more explicit sea ice estimates and display a mid holocene shift from a minor sea ice coverage to stable ice margin conditions in eastern fram strait while the inner east greenland shelf experienced less severe to marginal sea ice occurrences throughout the entire holocene highlights biomarker and ird data give insight into holocene sea ice conditions in fram strait we find increasing sea ice coverage off west spitsbergen throughout the holocene oceanic atmospheric variability caused neoglacial sea ice fluctuations ice conditions along east greenland shelf remain rather stable until 1000 years bp

biogenic magnetite and the magnetization of sediments biogenic magnetites are produced through the reduction of ferric iron by both biologically induced extracellular and biologically controlled intracellular processes with few exceptions all are ultra fine grained single domain magnetite biogenic magnetites formed by magnetotactic bacteria biologically controlled have been shown to contribute significantly to the natural remanent magnetization of carbonates and limestones hemipelagic and deep sea marine sediments the input into sediments of ultra fine grained magnetite produced by dissimilatory iron reducing bacteria biologically induced has yet to be firmly established but may be even more significant whether either type of authigenic biomagnetite is preserved is determined by postdepositional factors including oxidation reduction by substitution and dissolution unconsolidated and lithified sediments can be screened for putative biogenic magnetite by rock magnetic techniques it is not generally appreciated that magnetotactic bacteria and their magnetofossils can be identified by the unusual and in some cases unique morphologies size range and composition of the magnetite crystals magnetite produced by dissimilatory iron reducing bacteria have a distinctive morphology and size range but it is currently controversial as to whether these can be distinguished from certain chemically precipitated magnetites the presence of dissimilatory iron reducing bacteria however can be detected using microbiological techniques and sediment geochemistry biogenic magnetites are trace fossils and potentially useful environmental indicators and are considered to have significant input to the magnetization of most sediments both modern and ancient

holocene glacier and climate fluctuations on franz josef land arctic russia 80 n fluctuations in glacier extent provide the first comprehensive record of holocene paleoclimate for franz josef land glacier fluctuations were constrained using 45 14c ages from 16 glacier margins many glaciers were behind present margins before 9 4 kyr possibly as early as 10 3 kyr and probably remained so until at least 4 4 kyr where kyr 14c yr b p 1000 subsequently glaciers expanded probably reaching present margins before 3 2 kyr but certainly by 2 kyr a prominent neoglacial advance occurred ca 1 kyr and was followed by little ice age advances including one in the middle 1600s a d glaciers were larger than present at the turn of the century followed by widespread retreat soon after the holocene glacier record closely mimics that of svalbard 500 to 1000 km to the west suggesting similar glacier mass balance changes over a broad region of the eurasian arctia independent paleoclimate evidence from svalbard indicates higher than present summer air temperatures during the early to middle holocene when glaciers were behind present margins followed by generally cooler summer conditions and intermittent glacier advances and retreats holocene glacier variations were probably more influenced by summer temperature than winter precipitation

a multi proxy approach to assessing isolation basin stratigraphy from the lofoten islands norway article i nfo article history received 14 november 2009 available online 24 september 2010 this study takes a comprehensive approach to characterizing the isolation sequence of heimerdalsvatnet a coastal lake in the lofoten islands northern norway we use established methods and explore new techniques to assess changes in marine influence bathymetric and sub bottom profiles were acquired to examine basin wide sedimentation and a 5 8 m sediment core spanning the last 7800 cal yr bp was analyzed we measured magnetic susceptibility bulk organic matter properties molecular biomarkers diatom assemblages and elemental profiles acquired by scanning x ray fluorescence these characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively isolated three distinct litho chemo stratigraphic units represent a restricted marine phase 7800 6500 cal yr bp a transitional phase characterized by intermittent marine influence 6500 4900 cal yr bp and complete isolation and freshwater sedimentation 4900 cal yr bp to present although there are uncertainties in the estimate of the threshold elevation of the lake the timing of these phases generally corresponds with previous interpretations of the local relative sea level history this record captures sea level regression following the tapes transgression and supports the interpretation of a subsequent sea level stillstand dated in heimerdalsvatnet from 6500 to 4900 cal yr bp

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

late holocene glacier activity at inner hornsund and scottbreen southern svalbard new 10be dating on two late holocene maximum moraines on the treskelen peninsula and at scottbreen svalbard improve constraints on the timing and character of holocene glacial activity in this region average moraine ages of 1 9 0 3 ka n 4 on the treskelen peninsula and 1 7 0 1 ka n 5 on scottbreen indicate the timing of a glacial culmination the age of moraine abandonment at treskelen and scottbreen correlates with snowline lowering and glacier expansion between 2 0 and 1 5 ka observed elsewhere on svalbard both scottbreen and the glaciers near treskelen have surged in the instrumental record like many glaciers across svalbard yet the age relation between our possible surge related moraines and other glacier records leads us to hypothesize that on centennial and longer timescales climate forcing outweighs surge dynamics which exerts a stronger control on glacier length on centennial timescales at our study sites

a new approach for reconstructing glacier variability based on lake sediments recording input from more than one glacier abstract we explore the possibility of building a continuous glacier reconstruction by analyzing the integrated sedimentary response of a large 440 km2 glacierized catchment in western norway as recorded in the downstream lake nerfloen n61 56 e6 52 a multi proxy numerical analysis demonstrates that it is possible to distinguish a glacier component in the 8000 yr long record based on distinct changes in grain size geochemistry and magnetic composition principal component analysis pca reveals a strong common signal in the 15 investigated sedimentary parameters with the first principal component explaining 77 of the total variability this signal is interpreted to reflect glacier activity in the upstream catchment an interpretation that is independently tested through a mineral magnetic provenance analysis of catchment samples minimum glacier input is indicated between 6700 5700 cal yr bp probably reflecting a situation when most glaciers in the catchment had melted away whereas the highest glacier activity is observed around 600 and 200 cal yr bp during the local neoglacial interval 4200 cal yr bp until present five individual periods of significantly reduced glacier extent are identified at 3400 3000 2700 2100 2000 1700 1500 and 900 cal yr bp

multiple independent records of local glacier variability on nuussuaq west greenland during the holocene abstract the sensitivity of mountain glaciers to small scale climate fluctuations makes records of their past extent among the best proxies for identifying spatio temporal climate variability here we build on the few existing holocene records of local glacier change in greenland by using three independent geochronological methods proglacial lake sediment analysis cosmogenic 10be surface exposure dating and in situ 14c burial modeling to reconstruct continuous records of holocene glacier variability on nuussuaq west greenland 10be ages of perched boulders indicate eastern nuussuaq was deglaciated between 11 0 and 10 5 ka radiocarbon dated sediments from two lakes on nuussuaq contain mineral rich layers between 9 6 and 9 0 and 8 7 8 0 cal ka bp that may be correlative with nearby ice sheet moraines deposited in the early holocene multiple proxies for glacier size indicate frequent high amplitude glacier fluctuations superimposed on net glacier growth during the late holocene with significant ice expansion phases at 3 7 ka 2 8 ka and throughout the past 2 ka mean 10be ages from five nested moraine crests confirm that local glacier extents on nuussuaq culminated during both the little ice age 1470 c e n 3 and 1750 c e n 3 and the preceding centuries 520 1320 c e n 11 results reveal that local glaciers on nuussuaq episodically advanced and retreated at centennial timescales throughout the holocene most likely in response to regional climate changes in west greenland superimposed on the progressive insolation driven cooling trend in the northern hemisphere our new 10be moraine chronologies coupled with other glacier size proxies corroborate an emerging pattern of significant summer cooling and glacier expansion in the centuries prior to the little ice age in the arctic

glaciers on svalbard survived the holocene thermal optimum abstract about 60 of svalbard is covered by glaciers today but many of these glaciers were much reduced in size or gone in the early holocene high resolution modeling of the glacial isostatic rebound reveals that the largest glaciers in nordaustlandet and eastern spitsbergen survived the early holocene warming while the smaller more peripheral glaciers especially in the northwest started to form about 5 500 years ago and reached 3 4 of their current size about 600 years ago relative sea level has been rising during the last few millennia in the north and western parts of spitsbergen while land still emerges in the remaining part of svalbard here we show that this sea level rise in the northwest is caused by the regrowth of glaciers in the mid to late holocene that slowed down and even reversed the post glacial isostatic uplift and caused the crust to subside over large areas of spitsbergen

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

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

holocene mountain glacier history in the sukkertoppen iskappe area southwest greenland abstract mountain glaciers and ice caps gic independent of the greenland ice sheet respond rapidly to climate variations and records of their past extent provide information on the natural envelope of climate variability here we use a multi proxy approach that combines proglacial lake sediment analysis cosmogenic nuclide surface exposure dating in situ 10be and 14c and radiocarbon dating of recently ice entombed moss to generate a centennial scale record of holocene gic fluctuations in southwestern greenland following local deglaciation 10 9 ka sediments from proglacial crash lake record a glacier advance at 9 ka that is indistinguishable from nearby ice sheet moraines implying a synchronous response of gic and the greenland ice sheet to a centennial scale climate event following this local glacier advance gic experienced net recession until 4 6 ka radiocarbon ages of in situ moss n 29 and crash lake sediments reveal intervals of glacier expansion at 1 8 1 2 and 0 7 ka that are superimposed on an overall trend of net glacier expansion throughout the late holocene in situ 14c concentrations from bedrock adjacent to radiocarbon dated moss samples further constrain the duration of ice cover through the holocene in this region we find that our glacier size proxy records during the past 4 ka are broadly consistent with relatively lower temperatures recorded in gisp2 and occur during or following intervals of volcanic perturbations thus we speculate that volcanic activity although less frequent and intense than in the early holocene and during the little ice age may have led to centennial scale variability imprinted on net glacier expansion due to decreasing summer insolation through the late holocene

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

holocene moraine chronology spitsbergen svalbard lichenometric evidence for multiple neoglacial advances in the arctic late holocene neoglacial moraines occurring within 1 or 2 km of present glacier margins are prominent features in the forefields of spitsbergen glaciers little ice age moraines are typically the most extensive and best preserved moraines of older holocene advances are much less common where observed older moraines occur as moraine remnants and provide irrefutable evidence of earlier neoglacial advances the fragmentary moraine record indicates two little ice age advances and two older neoglacial advances lichenometry provides calibrated ages for periods of moraine stabilization the oldest moraines stabilized by ca 1500 years ago and a second group of moraines stabilized by ca 1000 years ago little ice age moraines were deposited during two periods an early group of moraines stabilized ca 650 years ago and a later group during the last several centuries the proposed moraine chronology compares well with other proxy climate records on spitsbergen and with moraine records from areas borde

numerical analyses of a multi proxy data set from a distal glacier fed lake sorsendalsvatn western norway abstract here we present a holocene record of glacier variability as documented through physical sediment properties analysed on sediments from the distal glacier fed lake nedre nedre lower sorsendalsvatn 918 m a s l located 35 km inland from the coast in western norway we emphasise comparing different sediment parameters by means of statistical methods as well as integrating chronological uncertainties along with uncertainties of reconstructed glacier variability a multi proxy data set consisting of sedimentological physical and geochemical data shows one main process as extracted by means of principal component analysis 88 of the variance explained by the first pc driving sediment variability in nedre sorsendalsvatn the common signal extracted from the sediment data is indicative of glacial activity in the catchment and is interpreted to vary in concert with the changing glacier equilibrium line altitude the reconstruction of former glacier activity is in accordance with glacier variability reconstructed from other sites in western norway including the termination of the deglaciation at approximately 10 000 cal yr bp the 8 2 ka bp finse event the holocene thermal optimum between 8000 and 5500 cal yr bp and the onset of the neoglacial at 5500 cal yr bp the largest glacial extent during the neoglacial time period took place during the little ice age the combined radiocarbon chronologies from three different sediment cores provide insight into the duration of the 8 2 ka event in the terrestrial system the maximum glacier activity at approximately 8 2 cal bp is the culmination of a glacier advance that began around 9 cal bp and accelerated at 8 4 cal bp the glacier advance ended abruptly at 8 0 cal bp

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

holocene fluctuations of a polythermal glacier in high alpine eastern jotunheimen central southern norway abstract bukkehammarbreen is a polythermal cirque glacier lying in the permafrost zone of eastern jotunheimen central southern norway in the proglacial lake bukkehammartjorna sediment analyses of loss on ignition loi magnetic susceptibility and analyses of grain size distribution have been used to reconstruct holocene variations in glacier activity and other catchment processes the glacier has low sediment production hence a low signal to noise ratio of minerogenic sediment flux is found grain size analyses are used to enhance the glacigenic signal and to detect glacier variations and other changes in sediment input the sedimentological record from bukkehammartjorn is compared with three other lake records from the same region in order to separate the glacial signal from variations in organic production and episodes of enhanced non glacial minerogenic sedimentation subsequent to the deglaciation after the younger dryas a preboreal glacial advance culminated before 10 100 cal bp this was followed by a prolonged period with no glaciers in the catchment until 7500 cal bp after which there is evidence of limited glacier activity lasting until 6800 cal bp between 6700 and 6000 cal bp the catchment was deglaciated after 6000 cal bp bukkehammarbreen reformed increasing in size towards 3800 cal bp with evidence for reduced glacier activity around 5200 cal bp a glacier with approximately similar size as at present has existed after 3800 cal bp the investigation has demonstrated the usefulness of multi site and multi parameter lacustrine investigations in reconstructing glacier fluctuations and for testing and validating the results the investigations have shown that grain size variations in sediment cores located at increasing distance from the meltwater inlet of a lake may provide an indicator of paraglacial activity in the catchment during the holocene the results also suggest that the lower altitudinal limit of permafrost in eastern jotunheimen remained below about 1800 m during the holocene

high frequency climate variability of the norwegian atlantic current during the early holocene period and a possible connection to the gleissberg cycle a high resolution sediment core md95 2011 from the voring plateau has been studied to document the variability of the surface water conditions during the younger dryas preboreal 13 9 kyr bp in the eastern norwegian sea in order to assess the climate variability in a period considered to be highly dynamic quantitative summer sea surface temperatures sssts with a time resolution of 20 40 years are reconstructed using three different diatom transfer function methods the younger dryas preboreal transition at site md95 2011 is documented with a temperature increase of 3 5 c 3 c within 100 years following the record resolves for the first time pbo as two prominent cooling events centred at 11 2 and 11 3 kyr bp in addition a broad cooling event documented from 10 3 9 9 kyr bp coincides with previously documented climatic events as the 10 3 event and erdalen event 1 10 1 9 9 kyr bp and 2 9 7 kyr bp respectively constrained by the observed ssst changes and diatom assemblages short term ssst ch

effects of distance from stone source on landscape scale variation in oldowan artifact assemblages in the paleo olduvai basin tanzania abstract ongoing excavations at olduvai gorge tanzania reveal tremendous variability among stone artifact assemblages across the plio pleistocene olduvai lake basin during bed i and lower bed ii times theoretically stone artifact traces of oldowan hominin land use are determined by the distribution of larger mammal carcasses and arboreal refuge from predation as well as proximity to stone material sources we provide an initial evaluation of these theoretical expectations focusing on the effects of distance from stone source on four parameters of oldowan artifact assemblages from the lowermost bed ii eastern olduvai basin quartzite artifact assemblages show expected distance from material source trends relative to their straight line proximity to three of four points along naibor soit a local quartzitic inselberg the weight density and proportionate weight of quartzite assemblages decrease with increasing distance from naibor soit as do the size of flaked pieces and the proportion of these that are minimally reduced the results demonstrate predicted behavioral patterning in broad scale traces of hominin land use but proximity to naibor soit explains the majority of variability in only the weight proportion of stone artifacts made on quartzite ecological factors appear to have also influenced the landscape distribution of oldowan hominin activity traces

changes in lake stratification and oxygen distribution inferred from two contrasting records of magnetotactic bacteria and diatoms 1 magnetotactic bacteria mtb and diatoms produce hard parts on seasonal timescales that continuously becomes embedded in various soft sediment archives consequently they can and are frequently used to reconstruct past environmental conditions in oceans fjords and freshwater basins in this study we observe how these two cosmopolitan creatures can be used to track vertical shifts in the distribution of oxygen in a small mountain lake situated in western norway several short and long sediment cores have been retrieved from the lake allowing for a detailed reconstruction that spans the last 2500 years during periods of enhanced runoff from the catchment the oxic anoxic transition zone oatz is lowered down to the lake sediment interface due to increased convection we posit that this condition reduces the concentration of microaerophilic magnetite producing mtb an interpretation partly supported by rock magnetic analyzes preservation of diatom frustules is however improved whenever this oxygen rich scenario prevails similarly when runoff is low and the oatz is lifted above the lake sediment interface mtb concentration seems to increase whereas dissolution of diatoms is more common this consistent antiphase relationship between mtb concentration and diatom preservation occurring on a multidecadal timescale during lowest reconstructed lake water ph in the lake s history suggest a coupled response to subtle changes in external environmental variables that affect catchment and lake hydrology

the lacustrine sedimentary sequence in sygneskardvatnet western norway a continuous high resolution record of the jostedalsbreen ice cap during the holocene abstract two lacustrine sediment cores from sygneskardvatnet sunndalen confirm that at least the northern part of the jostedalsbreen ice cap melted away during the atlantic chronozone between 6475 and 5300 14 c yr bp 7340 and 6150 cal bp possibly interrupted for short intervals of glacier activity around 6000 and 5800 14 c yr bp 6900 and 6700 cal bp prior to this periods of glacier expansion culminated at ca 8500 8400 8200 7750 7600 and 7400 cal bp the 8400 8200 cal bp advances are correlated with the widespread 8200 event finse event recorded in greenland ice cores lacustrine and proglacial sites and marine sediments during the early part of the holocene periods of glacier contraction culminated at ca 8450 8300 7900 7500 and 6250 cal bp of which the last represents climatic optimum conditions lowest supply of minerogenic sediments and or highest organic production the sedimentary record also shows that the ice cap has existed continuously since 5300 14 c yr bp 6150 cal bp neoglaciation involved three main phases 1 6150 4500 cal bp 2 4500 2700 cal bp 3 2700 cal bp to the present and a series of low amplitude glacier advances which occurred at 6000 5800 5700 5600 5500 5200 5100 4900 4800 4700 4550 4450 4300 4200 4150 4050 4000 3900 3800 3550 3300 2550 2450 2350 2250 2150 2000 1800 1700 1600 1400 1300 1150 1050 and the 1000 cal bp including the little ice age loss on ignition analyses indicate however that episodes of less glacier activity occurred during the mid and late holocene at around 5900 5800 5550 5450 5300 5050 4850 4750 4500 4400 4100 3950 3700 3450 3100 2650 2500 2400 2300 2200 1850 1700 1550 1350 1250 1050 1000 cal bp and during the twentieth century altogether the lacustrine record from sygneskardvatnet indicates that the holocene has been interrupted by 41 periods of increased glacier activity mean return period of ca 150 years and by 36 events of glacier contraction mean return period of 210 years spectral analysis of the loi data show peaks at periods of about 50 85 110 250 285 500 and 2000 calendar years the mean time resolution in core sygneskardvatnet 2 is ca 20 yr cm 1 while the mean sedimentation rate is 0 5 mm yr 1

10be surface exposure ages on the late pleistocene and holocene history of linnebreen on svalbard abstract arctic glaciers were sensitive to past changes in high latitude winter precipitation and summer temperature here we develop a late pleistocene to holocene history for linnebreen linne glacier in western svalbard using 10 be surface exposure ages on isolated erratic and moraine boulders we show that linnebreen had separated from the larger ice sheet over svalbard and was retreating up valley around the start of the younger dryas cold period we attribute this retreat during a cold period on svalbard to moisture starvation of linnebreen from advanced sea ice and or elevated shortwave boreal summer insolation that overwhelmed any reduction in sensible heat after an ice free period during the early to middle holocene linnebreen reformed sometime after 4 6 0 2 ka and was at a position roughly equivalent to its little ice age lia maximum extent before it began to retreat at 1 6 0 2 ka comparison with calibrated 14 c dates from three other glaciers could suggest that this period of ice retreat at 1 6 ka could be regional in extent linnebreen occupied the pre lia moraine when there was an increased ratio of cold arctic sourced relative to warm atlantic sourced waters around svalbard and advanced sea ice the retreat of linnebreen at 1 6 ka was concurrent with the increased presence of warm atlantic waters around svalbard and attendant sea ice retreat these coincident changes in ocean temperatures sea ice extent and linnebreen moraine age could imply a climatic forcing of the pre lia advance and retreat of linnebreen summer temperatures rather than changes in precipitation would then be dominant in driving ice retreat although the possibility of stochastic glacier margin variability cannot be excluded our data therefore suggest that linnebreen may have responded differently to past changes in sea ice extent that could depend on the background climate state deglacial climate vs late holocene climate which highlights the complexity in climatic controls on arctic glaciers

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

use of variable scale pressure test data to estimate the log hydraulic conductivity covariance and dispersivity of fractured granites near oracle arizona abstract application of modern stochastic theories to nonuniform geologic media requires among other things knowing the principal directions and correlation lengths of the log hydraulic conductivity covariance to infer this information by standard geostatistical methods directly from point measurements of hydraulic conductivity in three dimensional space is seldom possible due to a ubiquitous scarcity of data to show how this difficulty can be overcome we use an example of fractured granitic rocks near oracle arizona at this site hydraulic conductivities were measured on a small scale by packer tests and on a larger scale by cross hole tests the test results suggest that the measured hydraulic conductivities can be viewed as quantities defined over a continuum which are scalar on a local scale but exhibit large scale anisotropy due to spatial nonuniformity and the effect of fracture orientations based on this observation the two sets of hydraulic conductivity data are related theoretically and the resulting expression is used to estimate the anisotropic covariance function of log hydraulic conductivities at the oracle site we then employ these parameters to calculate a fickian dispersivity tensor for the oracle granite by relying on the recent theory of neuman et al 1987a our results highlight the need to extend available stochastic theories to the domain of strongly nonuniform media the properties of which fluctuate with large amplitudes

paleoclimatic implications based on equilibrium line altitude depressions of reconstructed younger dryas and holocene cirque glaciers in inner nordfjord western norway abstract relative to a present cirque glacier in innner nordfjord western norway equilibrium line altitude ela depressions for reconstructed cirque glaciers formed during the younger dryas 11 000 10 000 yr b p the erdalen event 9100 200 yr b p and the little ice age mid 18th century are calculated by the use of accumulation area ratio aar and compared to the corresponding values for plateau glaciers the temperature precipitation ela tp ela as reflected by plateau glaciers gives considerably larger ela depressions than use of the temperature precipitation wind ela tpw ela for cirque glaciers ela depressions during the younger dryas erdalen event and the little ice age thus strongly indicate that cirque glaciers are much more sensitive to changes in winter precipitation than plateau glaciers the difference in ela depressions of contemporaneous plateau and cirque glaciers during the younger dryas erdalen event and the little ice age suggests that winter precipitation was reduced to 59 7 71 6 and 88 7 compared to present values taken into account the reduced winter precipitation the corresponding mean ablation season temperature depressions were probably 4 3 0 3 3 0 0 2 0 3 and 1 4 0 3 0 2 c respectively

field example of data fusion in site characterization application of data fusion to characterization of the fountain and lyons formations at a field site incorporates geologic knowledge geophysical log data cross hole seismic tomography hydraulic test data and observations of head to reduce uncertainty associated with subsurface interpretation these formations consist of channel and overbank deposits that have undergone variable diagenesis resulting in more hydrofacies than would have been encountered in the original unaltered deposits the disparate types of available data are integrated to yield a coherent hydrofacies classification through use of discriminant analysis and soft data techniques this data fusion improves definition of the complex hydrofacies and increases knowledge of their spatial correlation two hundred multiple indicator conditional stochastic simulations of the site are generated 100 with only hard data and 100 with both hard and soft data forward groundwater flow modeling using estimates of hydraulic conductivity from field testing yields smaller head residuals for realizations which include soft data inverse modeling is used to eliminate hydrofacies realizations that do not honor hydraulic data and to estimate hydrofacies hydraulic conductivity ranges for the hard and hard soft data ensembles inverse parameter estimation substantially decreases head residuals for both ensembles standard deviations of hydraulic conductivities estimated through inverse modeling are smaller when both hard and soft data are used to generate the simulations even though head residuals are similar within the two ensembles when these estimated hydraulic conductivities are used

an inverse technique for developing models for fluid flow in fracture systems using simulated annealing one of the characteristics of flow and transport in fractured rock is that the flow may be largely confined to a poorly connected network of fractures in order to represent this condition lawrence berkeley laboratory has been developing a new type of fracture hydrology model called an equivalent discontinuum model in this model we represent the discontinuous nature of the problem through flow on a partially filled lattice this is done through a statistical inverse technique called simulated annealing the fracture network model is annealed by continually modifying a base model or template so that with each modification the model behaves more and more like the observed system this template is constructed using geological and geophysical data to identify the regions that possibly conduct fluid and the probable orientations of channels that conduct fluid in order to see how the simulated annealing algorithm works we have developed a synthetic case in this case the geometry of the fracture network is completely known so that the results of annealing to steady state data can be evaluated absolutely we also analyze field data from the migration experiment at the grimsel rock laboratory in switzerland

local glaciation in west greenland linked to north atlantic ocean circulation during the holocene recent observations indicate that ice ocean interaction drives much of the recent increase in mass loss from the greenland ice sheet however the role of ocean forcing in driving past glacier change is poorly understood to extend the observational record and our understanding of the ocean cryosphere link we used a multi proxy approach that combines new data from proglacial lake sediments 14 c dated in situ moss that recently emerged from beneath cold based ice caps and 10 be ages to reconstruct centennial scale records of mountain glacier activity for the past 10 k y in west greenland proglacial lake sediment records and 14 c dating of moss indicate the onset of neoglaciation in west greenland at ca 5 ka with substantial snowline lowering and glacier expansion at ca 3 7 ka followed by additional ice expansion phases at ca 2 9 ca 1 7 and ca 1 4 ka and during the little ice age we find that widespread glacier growth at ca 3 7 ka in west greenland coincides with marked cooling and reduced strength of the west greenland current in disko bugt the transition to cooler ocean conditions at ca 3 7 ka identified in disko bugt is registered by marine proxy data farther afield in east greenland and on the northwestern icelandic shelf implying large scale paleoceanographic changes across the north atlantic during this interval the similarity between glacier change on west greenland and multiple marine and terrestrial records across the north atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean cryosphere teleconnection is a persistent feature of the arctic system

palaeoenvironmental change and glacier fluctuations in the high tian shan mountains during the last millennium based on sediments from lake ala kol kyrgyzstan abstract a suite of limnological proxies measured in clastic sediments of the glacier fed lake ala kol ne kyrgyzstan document palaeoenvironmental change and glacier fluctuations in the central tian shan over the last millennium rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200 1400 ce 1500 1850 ce and 1900 1950 ce and glacier retreat periods during 1000 1200 ce and the intervening periods the maximal glacier extent as inferred from high lf si inc coh ca inc coh and low arm30 arm is recorded between 1500 and 1850 ce and corresponds to cold and wet conditions during the little ice age in the high central tian shan periods of glacier waxing and waning recorded at lake ala kol present a close correspondence to ice accumulation rate in the northern tibetan plateau suggesting that precipitation changes are the main driver of glacier fluctuations in central tian shan during the last millennium although temperature may have exerted a more complex influence on centennial timescales

bacterial magnetite in lake sediments late glacial to holocene climate and sedimentary changes in northern norway magnetic properties of sediments retrieved from a small lake in northern norway spanning the last f14500 cal years have been analyzed in detail the high resolution core with its ability to detect sub centurial variability records the rapid retreat of the fennoscandian ice sheet fis in northern lyngen and subsequently the establishment of a stable allerod to younger dryas watershed from early holocene and to the present magnetotactic bacteria mb producing stable single domain ssb magnetite become the dominating magnetic carrier the small low relief catchment area with its quartzite bedrock scattered till and vegetated surface generates a negligible contribution of detrital magnetic minerals this allows for the opportunity to follow the presence and changes of the magnetosomes during the last 10000 years a strong positive statistical relationship r 2 0 83 between the anhysteretic remanent magnetisation susceptibility varm and loss on ignition loi suggests an environmental control over the bacteria magnitude quart int 88 2002 13 that most likely is related to summer climate a comparison between the magnetic mineralogy as evident from the s ratio jirm100mt jsirm3t and the reconstructed summer temperatures from a nearby lake shows a close covariation between cooler summers and harder s ratios for a series of climatic events intervariability of loi data and other proxies such as august sea surface temperatures sst from the nordic sea suggests land ocean connections during converging phases of cooler climate where the most prominent in phase periods are approximately 1 6500 5000 2 3500 2400 and 3 1700 1000 cal years bp the most significant change in the holocene magnetic signal is initiated at f3700 cal years bp which we refer to here as the holocene turnover d 2004 elsevier b v all rights reserved

synchronized proxy based temperature reconstructions reveal mid to late holocene climate oscillations in high arctic svalbard existing paleoclimate data are exceedingly sparse from southern spitsbergen a high arctic region predicted to experience significant environmental changes because of amplified warming we analyzed biotic and isotopic paleolimnological proxies to reconstruct past climate from a lacustrine sediment core with a basal age of 5500 a bp in southern spitsbergen 77 n we used fossil chironomidae assemblages to quantitatively reconstruct past mean july air temperatures and stable oxygen isotope values 18o of these fossils to estimate changes in mean annual air temperature these proxy records are strikingly similar and show that the coldest anomaly since the mid holocene occurred between 350 and 50 cal a bp during the little ice age whereas the warmest period in the summer temperature record occurred between 5500 5000 and 2000 cal a bp our findings indicate that the natural long term air temperature dynamics in our study area are most likely connected to solar minima and positive feedback mechanisms from sea surface temperature maxima the results also highlight that the recent temperature increase is unprecedented in its rate with a 2 c increase in the summer temperatures during the past 50 years

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

late holocene glacier growth in svalbard documented by subglacial relict vegetation and living soil microbes much renewed research interest in arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas glacier and permafrost changes are among a number of proxies used for monitoring past and present arctic climate change here we present observations on frozen in situ soil and vegetation found below cold based glacier longyearbreen 78813 n 2 km upstream from the present glacier terminus dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c 1100 years the meteorological setting of non surging longyearbreen suggests this example of late holocene glacier growth represents a widespread phenomenon in svalbard and in adjoining arctic regions in addition we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods and we present evidence for microbes having survived more than 1100 years in a subglacial permafrozen state

high resolution x ray fluorescence core scanning analysis of les echets france sedimentary sequence new insights from chemical proxies the les echets sediment sequence has recently been the subject of a high resolution multi proxy study which revealed shifts in lake productivity linked to greenland stadials and interstadials over the last 40 ka wohlfarth et al 2008 rapid ecosystem response to abrupt climate changes during the last glacial period in western europe 40 16 ka geology 36 407 410 here we present new elemental data for this sequence as acquired using an x ray fluorescence core scanning system which provides in situ high resolution continuous multi element analyses it was found that the strength of associations between the studied elements ti rb k zr si ca sr mn and fe varied over time with changes in lake status which are ultimately driven by changes in climate increases in fine grained detrital input as indicated by ti rb k and zr rb overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions several of these arid periods are coincident with low diatom concentrations and the timing of heinrich events h4 h3 and h2 the duration of the environmental impacts linked to the h events varied by proxy with elemental data ti and zr rb estimating shorter events than the diatom data periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity the elemental data provide new insights into hydrological changes and related sediment processes within the catchment and highlight the need for multi element and multi proxy approaches when reconstructing climate change using lacustrine sediment sequences copyright 2011 john wiley sons ltd

holocene vegetational history and climatic change in west spitsbergen plant macrofossils from skardtjorna an arctic lake macrofossil analyses of a 335 cm long core from skardtjorna a small lake on the west coast of spitsbergen svalbard are presented the known processes of deposition of plant remains to arctic lake sediments are summarised and used in the interpretation of the vegetation history at skardtjorna the basal sediment is ams dated to 8110 110 bp the rest of the profile is dated by palaeomagnetic correlation the lowest sediments have the greatest macrofossil concentration and numbers of taxa per sample the occurrences of cassiope hypnoides and salix cf glauca before 4000 bp indicate a mean july temperature for the early holocene about 2 c higher than today comparable to the cassiope tetragona vegetation zone of the mid arctic region of the inner fjords increasing climatic severity resulted in the threshold from the cassiope to the dryas vegetation zone being passed at about 2500 bp the inferred climatic history at skardtjorna is compatible with other evidence from svalbard and elsewhere in the arctic

temporal and spatial scaling of hydraulic response to recharge in fractured aquifers insights from a frequency domain analysis quantification of the recharge in fractured aquifers is particularly challenging because of the multiscale heterogeneity and the range of temporal scales involved here we investigate the hydraulic response to recharge of a fractured aquifer using a frequency domain approach transfer functions are calculated in a range of temporal scales from 1 day up to a few years for a fractured crystalline rock aquifer located in ploemeur s brittany france using recharge and groundwater level fluctuations as input and output respectively the spatial variability of the response to recharge characteristic response time amplitude temporal scaling is analyzed for 10 wells sampling the different compartments of the aquifer some of the transfer functions follow the linear reservoir model behavior on the contrary others display a temporal scaling at high frequency that cannot be represented by classic models large scale hydraulic parameters estimated from the low frequency response are compared with those estimated from hydraulic tests at different scales the variability of transmissivity and storage coefficient tends to decrease with scale and the average estimates converge toward the highest values at large scale the small scale variability of diffusivities which implies the existence of a range of characteristic temporal scales associated with different pathways is suggested to be at the origin of the unconventional temporal scaling of the hydraulic response to recharge at high frequency