late ordovician jaw bearing polychaetes from anticosti island eastern canada and their biogeographic significance the upper ordovician to lower silurian shallow marine succession of anticosti island eastern canada provides one of the most complete records across the hirnantian in the world this study reports a diverse assemblage of scolecodonts polychaete jaws from the upper katian and hirnantian vaureal ellis bay and basal becscie formations of western anticosti the collection of 10 samples includes ca 30 species representing 10 families the fauna is dominated by polychaetaspids mochtyellids paulinitids and polychaeturids the family xanioprionidae and genera pistoprion tetraprion and rakvereprion are documented for the first time from the ordovician of laurentia the anticosti polychaete fauna shows great similarity to the contemporaneous faunas of baltoscandia this is evidenced by a high relative abundance of mochtyellids and polychaeturids and a number of common species thus suggesting that the closing iapetus ocean at that time did not constitute a barrier for the dispersal of jaw bearing polych

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

diversification and biogeography of scolecodont bearing polychaetes in the ordovician scolecodonts are common microfossils in palaeozoic rocks bearing witness to the extensive radiation of jawed polychacte worms during the ordovician period information on ordovician scolecodonts is increasing though it is still patchy and strongly skewed towards baltica and laurentia comparison of the faunas of these two palaeocontinents indicates that approximately 50 of the genera but only a few species had intercontinental distribution meagre data from other terranes also show that several genera were cosmopolitan in total more than 50 ordovician genera are known the first records are from the furongian latest cambrian but scolecodont diversity and abundance remained very low until the darriwilian the earliest jawed polychaetes had primitive usually symmetrical placognath ctenognath type jaw apparatuses xanioprionids tetraprionids and or conjungaspids seem to have played an important role in the early evolution and diversification of scolecodont beating polychactes the first more advanced taxa such as the polychaetaspids with labidognath type jaw apparatuses and mochtyellids with placognath type apparatuses and compound maxillae are first recorded in the earliest mid ordovician the most significant increase in global generic diversity but also regional species level diversity occurred in the late mid ordovician when many common taxa appeared accordingly the origination rate is highest in that interval since many ordovician polychaete genera are relatively long ranging extending into the silurian the extinction rate is low throughout the period increasing only slightly in the latest late ordovician the normalised diversity curve is characterised by an increasing trend in the mid ordovician followed by a plateau in the late ordovician c 2006 elsevier b v all rights reserved less

impacts of recent paraglacial dynamics on plant colonization a case study on midtre lovenbreen foreland spitsbergen 79 n climatic changes since the end of the little ice age have considerably disturbed environmental balances of plant colonization in high latitudes within one century on spitsbergen valley glaciers have retreated up to one kilometre from their original terminus as of 1918 affecting several hundred hectares of two types of landscape processes plant colonization and paraglacial morphogenesis since these processes are limited to the chronological position of the old ice front it is possible to know the rate of plant colonization by both qualitative and quantitative means as well as speculate on the processes involved such as the effects of runoff the present study is limited to the midtre lovenbreen forefield latitude 79 n longitude 12 e where geomorphologic and floristic samples were collected in 2003 on stable deposits in this area the settlement and the evolution of floristic groups have been documented during this time period of colonization the plain areas are reworked by runoff at a kilometric scale and are characterized as similar to their surrounding biogeographic landscapes thus a relationship can be observed between the paraglacial process occurring in the proglacial forelands and surrounding stable surfaces on till deposits these features that occur as spatial discontinuities across the landscape are perceptible through either plant colonization or disturbance to vegetation caused by hydrological processes ultimately however runoff dynamics maintain pioneer vegetation groups which are superimposed on plant colonization that are driven by temporal periods of deglaciation differences in the rates and the nature of plant colonization are biomarkers of paraglacial dynamics

chitinozoan graptolite and scolecodont reflectance as an alternative to vitrinite and pyrobitumen reflectance in ordovician and silurian strata anticosti island quebec canada because of the absence of vitrinite in lower paleozoic sediments the reflectance of pyrobitumen is used as an indicator of thermal maturation a new technique of preparing organic matter permits discrimination among types of zooclasts and solid bitumen including pyrobitumen and leads to more precise reflectance histograms studies of organic matter from ordovician silurian strata of anticosti island show that reflectance of zooclasts is different from that of solid bitumen and that each group of the following zooclasts chitinozoans graptolites and scolecodonts has a specific reflectance evolution path with increasing depth on a logarithmic scale the paths of the three groups of zooclasts are linear highly correlated and converging however reflectance of solid bitumen is not linear throughout the range studied solid bitumen becomes linear only where the reflectance is greater than 0 75 comparing the relations between zooclasts and solid bitumen with the vitrinite solid bitumen correlation in the literature suggests that a hypothetical vitrinite evolution line in the anticosti island basin should be subparallel with that of chitinozoans and graptolites but 0 4 0 8 lower in the 1 2 range however scolecodonts and vitrinite should have the same reflectance at 1 but scolecodont reflectance should be slightly 0 2 higher for a vitrinite reflectance of 2

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

mass balance of white glacier axel heiberg island n w t canada 1960 91 white glacier is a valley glacier at 79 5 n with an area of 38 7 km 2 its mass balance has been measured over 32 years with a 3 year gap by standard techniques using the stratigraphic system with a stake density of the order of one stake per km 2 errors in stake mass balance are about 200 250 mm due largely to the local unrepresentativeness of measurements errors in the whole glacier mass balance b are of the same order as single slake errors however the lag 1 autocorrelation in the time series of b is effectively zero so it consists of independent random samples and the error in the long term balance normal b is noticeably less b is 100 48 mm the equilibrium line altitude ela averages 970 m with a range of 470 1400 m mass balance is well correlated with ela but detailed modelling shows that the equilibrium line is undetectable on visible band satellite images a reduced network of a few stakes could give acceptable but less accurate estimates of the mass balance as could estimates based on data from a weather station 120 km away there is no evidence of a trend in the mass balance of white glacier to detect a climatologically plausible trend will require a ten fold reduction of measurement error a conclusion which may well apply to most estimates of mass balance based on similar stake densities

a far field record of the end ordovician glaciation the ellis bay formation anticosti island eastern canada abstract the end ordovician was a critical period in earth history it was a time of global climatic change with large scale continental glaciations a wealth of recent work has documented the stratigraphical records from the near field areas i e from various gondwanan continental relics where glaciation was more severely felt there is an urgent need to re examine the stratigraphic record from the far field areas at greater levels of resolution than it has been hitherto possible in order to understand the timing duration and character at the glaciation centred around the ordovician silurian o s boundary one of the best exposed and most complete stratigraphic records from paleotropical areas near the boundary is on anticosti island in eastern canada the east west trending 200 km long ellis bay hirnantian outcrop belt with superb coastal exposures at both ends of anticosti island is slightly oblique to the paleoshoreline with near shore siliciclastic dominated facies restricted to the eastern part of the island and more offshore carbonate dominated facies present along the central and western parts these mixed carbonate siliciclastic facies accumulated along a storm dominated beach to offshore profile they are organized into a stacked set of shallowing upward offshore to shoreline facies successions typically coarsening upward separated by deepening upward facies successions typically fining upward formed during intervening transgressions high frequency glacio eustatic fluctuations were the dominant control on the development of tr sequences observed in the ellis bay succession of anticosti island although tectonic subsidence had a substantial secondary effect on thickness five tr sequences are recognized allowing for precise correlation along the ellis bay outcrop belt in the eastern sections relatively thin tr sequences are locally bounded by unconformities a typical sequence begins with thin transgressive limestone overlain by a maximum flooding calcareous shale grading up into regressive storm influenced proximal to transitional zone fine sandstone grainstone and shale which are sharply overlain by shoreface to foreshore sandstone grainstone in the central and western sections the thicker tr sequences have more symmetrical transgressive regressive components reflecting greater subsidence compensated by a higher carbonate sediment supply two discrete glacial periods are recognized during the deposition of the hirnantian ellis bay succession with the younger one recording large sea level changes 50 m in magnitude caused by the development of very large ice sheets over western gondwana abundant ice conditions on the globe during the end ordovician and the resulting high amplitude eustasy appear to have left distinctive stratigraphical imprints on mixed paleotropical siliciclastic carbonate ramps

exceptionally preserved soft bodied assemblage in ordovician carbonates of anticosti island eastern canada abstract a diverse benthic fauna containing exceptionally preserved soft bodied organisms is described from the new vaureal konservat lagerstatte from the upper ordovician vaureal formation katian of anticosti island canada these fossils occur as pyritic or goethitic if weathered calcitic aggregates or sediment filled voids on micritic bedding planes of a marlstone limestone alternation originated on a shallow tropical carbonate ramp many organisms are preserved in association with their traces e g burrows trails whose changing shapes indicate increasing cohesiveness of the substrate rapid burial obrution under dysoxic bottom conditions must have favoured exceptional preservation although anatomical details of the organisms are often lacking due to recrystallization members of different groups of organisms could be interpreted based on their shape and other characteristic features including those of which represent their oldest fossil record i e acoelomorpha turbellaria nemertea nematoda beside polychaeta sipuncula ostracoda and other arthropoda in parallel with molecular data which recently have changed the phylogenetic status of some clades this soft bodied fauna and their traces not only record their appearance but add to the understanding of their body plan and behaviour the new konservat lagerstatte provides important information about a diverse benthic community in the late ordovician after the great ordovician biodiversification event gobe and represents a calibration point for comparison across the late ordovician mass extinction moreover comparable fossil lagerstatten are probably more common in shallow marine carbonates than currently known but might have been simply overlooked

paraglacial gullying of sediment mantled slopes a case study of colletthogda kongsfjorden area west spitsbergen svalbard this paper evaluates the paraglacial evolution of a sediment mantled slope in a polar maritime environment the intensity of paraglacial processes is estimated through quantifi cation of erosion and dating of fi eld sectors with the help of photographic archives gully erosion has been estimated using morphometric parameters and by surveys of vegetation cover the rapid melting of dead ice cores controls gully formation this leads to slope form modifi cation gully profi le gradients are reduced from a mean of 35 to a mean ranging between 10 and 15 profi le evolution results from the collapse of glacier lateral moraine all data mean slope angle of individual gullies frequency distribution of slope angles fractional distance to the apex gullying index volume of debris mobilized vertical erosion rate tend to increase with increasing deglaciation age and the duration of paraglacial activity vegetation colonization is a response to stabilization of the ground surface and the drying up of the ground surface due to dead ice melting the full sequence of paraglacial slope adjustment gully incision stabilization may occur rapidly at the study site i e within two decades finally a lateral morphogenic sequence is proposed showing the importance of paraglacial processes at the onset of the deglaciation

the duration of the active phase on surge type glaciers contrasts between svalbard and other regions many glaciers in svalbard and in other glacierized areas of the world are known to surge however the time series of observations required to assess the duration of fast motion is very restricted data on active phase duration in svalbard come from aerial photographs satellite imagery field surveys and airborne reconnaissance evidence on surge duration is available for eight svalbard ice masses varying from 3 to 1250 km 2 worldwide active phase duration is recorded for less than 50 glaciers few observations are available on high polar ice masses the duration of the active phase is significantly longer for svalbard glaciers than for surge type glaciers in other areas from which data are available in svalbard the active phase may last from 3 to 10 years by contrast a surge duration of 1 2 years is more typical of ice masses in northwest north america iceland and the pamirs ice velocities during the protracted active phase on svalbard glaciers are considerably lower than those for many surge type glaciers in these other regions mass is transferred down glacier more slowly but over a considerably longer period svalbard surge type glaciers do not exhibit the very abrupt termination of the active phase over periods of a few days observed for several alaskan glaciers the duration of the active phase in svalbard is not dependent on parameters related to glacier size the quiescent phase is also relatively long 50 500 years for svalbard ice masses detailed field monitoring of changing basal conditions through the surge cycle is required from surge type glaciers in svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago which may also typify other high polar ice masses the finding that surge behaviour in the form of active phase duration shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges

palaeoclimates in central and south america since 18 000 bp based on pollen and lake level records abstract the last 18 ka of palaeoclimates are discussed at 3 ka intervals based on palaeoenvironmental changes shown in pollen and lake level records from central and south america a total of 61 pollen records fulfill the requirements of continuity and chronology to be used in this synthesis 8 records from tropical and subtropical lowlands in central and south america 7 records from the central american highlands 26 records from the high andes north and south of the equator 2 records from the southern subtropics and 18 from the southern andes and subantarctic islands palaeoclimatic interpretation of the pollen records is semiquantitative based on bioclimatic parameters such as e g elevational temperature gradients or latitudinal precipitation gradients that can be related to vegetation zonation additional palaeoclimatic information is obtained from lake level records derived either from dated shorelines or from the limnological history of lake sediment sections large scale palaeoclimatic comparison of the proxy data records indicates that full and late glacial climates throughout central and south america were cooler than today by about 4 to 5 c but that moisture patterns showed regional differentiation thus in both the southern subtropics and high latitudes in southern chile conditions were substantially moister than today during full and late glacial times whereas everywhere else conditions were far drier than today in terms of palaeocirculation this scenario can be interpreted as a poleward shift of the subtropical as well as the westerly circulation a scenario that has been suggested by palaeoclimatic simulations from general circulation models gcm another major palaeoclimatic aspect predicted by the gcm simulations is the suppressed early holocene summer monsoon in the southern subtropics although proxy records are few from this zone their palaeoenvironmental history during that time shows a period of aridity that would support the model one of the most controversial aspects of south american palaeoclimates concerns the existence of a younger dryas equivalent a cold period between 11 and 10 ka bp based on the existing data from south america that show a great diversity of palaeoclimatic trends the concept of an interval that is characterized by the same climatic signal as documented for the north atlantic seems too simplistic moreover at this point only very few records have been analysed in sufficient detail to yield unambiguous climatic information for the interval in question the principal outcome of this palaeoenvironmental and palaeoclimatic synthesis is the better understanding of the type and quality of data available at present and the realization of regions and periods where much more and concerted effort is needed to address problems of intra and interhemispheric palaeoclimatic correlations only then can questions concerning the mechanism of climatic change be tackled successfully

simulating climatic mass balance seasonal snow development and associated freshwater runoff in the kongsfjord basin svalbard 1980 2016 the kongsfjord basin in northwest svalbard is the site of a number of interdisciplinary studies concerned with the effect of fresh water from seasonal snow and glacier melt on the physical and biol

surge type glaciers in the russian high arctic identified from digital satellite imagery landsat digital imagery was used to search the island archipelagos of franz josef land severnaya zemlya and novaya zemlya russian high arctic for the presence of looped moraines characteristic of past glacier surges the imagery provides almost complete summer time coverage of the 60000 km 2 of ice in these islands very few surge type glaciers are identified none in franz josef land three in novaya zemlya and two on severnaya zemlya this contrasts greatly with svalbard ice covered area 36 600 km 2 to the west where 36 of glaciers and ice cap drainage basins are inferred to surge the strong climatic gradient across the eurasian high arctic with decreasing temperature and moisture eastward may provide a gross control on this pattern through colder glacier thermal structure limiting basal drainage on the thinner ice masses in particular

estimating the long term calving flux of kronebreen svalbard from geodetic elevation changes and mass balance modelling this study independently quantifies geodetic elevation change and models surface mass balance to solve the continuity equation the approach is tested on two dynamically different glaciers kongsvegen and kronebreen in northwest svalbard through two time epochs 1966 1990 95 i and 1990 95 2007 ii on kongsvegen a dynamically inactive glacier the residual term represents an error associated with determining elevation changes and surface mass balance it is apparent that centerline mass balance estimates are not representative of the entire glacier which we relate to center line accumulation being larger than the elevation bin average on kronebreen a fast flowing and actively calving glacier a significant part of the residual is identified with the long term calving flux for both glaciers the cumulative surface mass balance remained close to zero during the first epoch but became increasingly negative in the second epoch the long term calving flux of kronebreen is estimated to be 0 14 0 03 km3 w e a 1 during epoch i and 0 20 0 05 km3 w e a 1 in epoch ii

late weichselian valdaian and holocene vegetation and environmental history of the northern timan ridge european arctic russia abstract lake and peat deposits from the timan ridge arctic russia were pollen analysed reconstructing the vegetation history and paleoenvironment since the last glacial maximum lgm 20 18 000 years ago the sites studied are located inside the margins of a large paleolake of about 20 km 2 by us named lake timan this lake developed in the late weichselian more than 30 000 years after the deglaciation of this region and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment the lake was drained during the early holocene when the outlet rivers eroded the spillways a new generation of much smaller lakes formed during the holocene when the last remnants of buried glacier ice melted away causing the exposed floor of lake timan to subside since deglaciation the following regional vegetation development has been recorded 1 during the initial stage of lake timan the dominant vegetation was discontinuous steppe tundra with patches of snow bed vegetation 2 a dwarf shrub tundra established during the late weichselian interstadial allerod probably reflecting warmer and moister conditions 3 the younger dryas cooling is recognised by a reversal to steppe tundra and snowbeds on unstable mineral soils and higher palynological richness 4 soon after the transition into the holocene a birch forest established on the timan ridge 5 a cooling starting around 8200 cal years bp initiated the deforestation of the exposed hills in the most protected sites birch trees persisted until later than 4000 years ago reflecting a gradual development into the present treeless dwarf shrub tundra

glacier bed characteristics of midtre lovenbreen svalbard from high resolution seismic and radar surveying we conducted a seismic and radar survey of the central part of midtre lovenbreen a small polythermal valley glacier in svalbard we determined the physical properties of the material beneath the glacier by measuring the reflection coefficient of the bed by comparing the energy of the primary and multiple reflections and deriving the acoustic impedance by making reasonable assumptions about the properties of the basal ice we determined the acoustic impedance of the bed material as 6 78 1 53 x 10 6 kg m 2 s 1 we interpret the material beneath the glacier to be permafrost with up to 50 ice and we speculate that the material may be frozen talus similar to a deposit observed directly by others beneath another svalbard glacier the implication for midtre lovenbreen is that the basal material beneath the present glacier is not able to support fast flow we conclude that midtre lovenbreen has most likely had limited capability for faster flow in the past with motion dominated by internal deformation midtre lovenbreen is used as a study glacier for the scientific community in svalbard and a large number of studies have been based there our results show that it cannot be used as an analogue for larger glaciers in svalbard having distinct basal boundary conditions

glacier hydrology in svalbard norwegian high arctic abstract progress in glacier hydrology has focused on temperate glaciers although partly or wholly non temperate glaciers are found in many parts of the world and significant areas of former ice sheets were probably non temperate it has usually been assumed that drainage from non temperate glaciers consists of relatively dilute and invariable supraglacial runoff in this paper the hydrology of glaciers in the high arctic archipelago of svalbard is examined variations in the thermal regimes of glaciers and their implications for drainage are first addressed results from svalbard concerning meltwater discharge and storage and solute and suspended sediment dynamics are then reviewed in general meltwater penetration of non temperate ice is limited and drainage from non temperate glaciers in svalbard has many of the characteristics of sub aerial drainage however it would be erroneous to view this drainage simply as dilute supraglacial runoff as significant material transport occurs in suspension and solution furthermore twentieth century climate change has probably led to changes in the thermal regimes of some svalbard glaciers such that relict drainage structures are sometimes observed while meltwater yields are augmented by runoff which can be attributed to the loss of mass from glaciers at large spatial scales turbid plumes observed at the marine margins of polythermal ice caps indicate that meltwater can be routed subglacially through non temperate ice

sensitivity to long term climate change of subpermafrost groundwater systems in svalbard deep subpermafrost aquifers are highly climate dependent with the permafrost as an aquitard preventing groundwater recharge and discharge a study from the high arctic island of spitsbergen svalbard shows that during a glacial to interglacial phase both the permafrost and the glacier regime will respond to climatic changes and a glacier fed groundwater flow system will vary accordingly a full glaciation results in the melting of permafrost and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers these groundwater flow systems will mainly be localized to fjords and valleys and form low lying terrestrial springs when the relative sea level drops during deglaciation due to glacio isostatic rise during an interglaciation permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation an already frozen spring system cannot reopen before the permafrost melts only groundwater springs related to permanently warm based glacial ice will persist into the next glaciation during a new glaciation flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm based ice causing permafrost thawing

paleo evolution of the black sea watershed sea level and water transport through the bosporus straits as an indicator of the lateglacial holocene transition the paleo evolution of the black sea level during the lateglacial holocene transition is still unclear which motivates us to provide new estimates for that period based on the analysis of water budget hydrological conditions in the black sea catchment area are reconstructed here using water balance equation available data and constraints based on simple theory relating the runoff ratio with climatic characteristics in order to estimate the impact of the aridity of climate we consider two alternative scenarios 1 climate change under constant in time gradient in precipitation and evaporation over land and sea and 2 climate change accounting for changes in the horizontal distribution of precipitation and evaporation hydrological data are compiled from available present day data and paleo observations a number of sensitivity experiments is carried out revealing that the hydrological conditions in the black sea watershed should have evolved towards a very arid climate similar to the present day climate in the caspian sea area in order to initiate a drop of sea level of 100 m below the sill depth of the bosporus straits as speculated in some recent research estimates of sea level changes reveal a qualitative agreement with the coast line evolution inferred from paleo observations the younger dryas draw down of the black sea starts at about 13 3 to 13 kyr bp with a maximum low stand of 104 m at 11 5 kyr bp in an arid climate scenario the sea level reaches the outlet at about 8 8 to 7 4 kyr bp approximately at that time mediterranean sea level was about 10 m higher making flooding events of the black sea possible however the nature and exact timing of the holocene reconnection depends also on other not well known factors one of them is the bosporus sill depth motivating further research in this field estimates of the water transport through the bosporus straits are also provided for the time of lateglacial holocene transition

a late ordovician age for the whirlpool and power glen formations new york a restudy of the palynology of the whirlpool formation and power glen formation in new york usa yielded a diverse fossil assemblage with cryptospores glomalean fungi acritarchs chitinozoans scolecodonts and small carbonaceous fossils these new data and particularly the presence of the chitinozoan index fossil hercochitina crickmayi combined with emerging stable carbon isotope data suggest a late ordovician katian or hirnantian age for these formations which is older than their previously suggested silurian rhuddanian age

superimposed ice regime of a high arctic glacier inferred using ground penetrating radar flow modeling and ice cores 1 a 900 mhz ground penetrating radar gpr profile collected along 1 7 km of the centerline of a high arctic glacier in svalbard is interpreted using shallow ice core data and thermomechanical flow modeling four distinct zones are visible in the image and correspond to areas of firn recent and older superimposed ice and ablation zone glacier ice on the ground the areas of firn and superimposed ice are characterized by relatively steeply and gently dipping internal reflecting horizons irh respectively in the radar image the irhs arise from permittivity contrasts due to density variations produced in firn by alternating firn and ice layers and in superimposed ice by varying air bubble content recently formed and older superimposed ice can be distinguished in the gpr image a three dimensional flow model is used to indicate the long term mass balance and flow history responsible for the spatial distribution and orientation of superimposed ice irhs in the radar image results indicate that the irh distribution can only be explained by invoking a down glacier shift in mean 30 year equilibrium line altitude ela by 20 30 m compared with measured mean 30 year ela they also suggest that many of the superimposed irhs are relict features produced 100 years b p when the ela was 100 150 lower than at present this work advocates combined gpr and flow modeling as a unique tool for validating mass balance measurements and or inferring the mass balance dynamic history of a glacier beyond a recent measurement period

episodic sedimentation on an early silurian storm dominated carbonate ramp becscie and merrimack formations anticosti island canada the 150 160 m thick lowermost silurian rhuddanian becscie and merrimack formations of anticosti island canada represent continuous deposition on a shallow open marine carbonate ramp several rock types are identified a laminated and homogenous mudstone b laminated and homogenous packstone c argillaceous mudstone and packstone d calcareous shale e laminated calcisiltite f medium to fine grained grainstone and g bio intraclastic rudstone these rock types are arranged into five distinct lithofacies lf1 calcareous mudstone shale lf2 laminated homogenous mudstone lf3 calcareous grainstone shale lf4 laminated mudstone grainstone and lf5 laminated calcisiltite grainstone the sequence reflects deposition on a low energy muddy carbonate to argillaceous ramp subject to short lived episodic high energy storms these events produced fining upwards storm units 5 80 cm thick or tempestites consisting of a sharp scoured base overlain by intra bioclastic rudstone grading upwards into medium grained grainstone finely laminated calcisiltite and mudstone or shale these are interbedded with low energy fairweather mudstones and calcareous shales deposition progressed from a carbonate mud dominated ramp in the becscie formation to an argillaceous mud dominated ramp in the merrimack formation lateral tempestite proximality trends and lithofacies distribution indicate that the anticosti basin deepened to the south east into the iapetus ocean and shallowed towards a sw ne orientated shoreline to the north west vertical tempestite proximality trends and lithofacies changes identify third order eustatic sea level changes after an initial deepening at the base of the formation a shallowing deepening event dominated the sequence several higher order fluctuations defined by lithofacies and tempestite proximality trends are superimposed on these changes the fluctuations identified with the aid of tempestite proximality trends are of an order of magnitude higher than those identified by either lithofacies or palaeontological methods

late glacial holocene climate of the lake district of chile pollen evidence from a 350 cm section of a fen in a moraine belt at rucanancu 39 33 s 72 18 w bears on the controversy regarding interpretation of late glacial and holocene climate in midlatitude chile earlier pollen studies indicating a cooling trend between approximately 11 000 and 10 000 yr b p disagreed with observations of glacier fluctuations which show continuous glacier wastage and by inference warming after 12 500 yr b p and possibly earlier up until neoglaciation beginning after 6850 yr b p fossil beetle assemblage data in this time range support the interpretation of climate made from the observed glacier behavior at rucanancu a pollen assemblage containing upper montane podocarp podocarpus andinus in quantities reaching 34 and dating between 10 440 and 10 000 yr b p implies a cold climate with summer temperatures possibly 5 8 c lower than today s holocene warming began afterward later than the glacier and beetle records indicate and continued until at least 8350 yr b p as suggested by the sequence of assemblages dominated by myrtaceae by aextoxicon punctatum and by gramineae a subsequent assemblage of nothofagus obliqua type implies an increase of moisture until 6960 yr b p following which n dombeyi type under a cool and humid neoglacial climate became dominant

the end ordovician glaciation and the hirnantian stage a global review and questions about late ordovician event stratigraphy abstract this paper proposes a global review of hirnantian event stratigraphy the hirnantian gssp in south china is tentatively correlated with latest ordovician strata from the peri gondwanan glacial regions problems of biostratigraphical correlation are highlighted at a worldwide scale the major biostratigraphically useful fossil groups graptolites chitinozoans brachiopods conodonts acritarchs are analysed and their limits for global correlation of the uppermost ordovician are discussed palaeobiogeographical disparities are invoked as the primary cause of the difficulty in establishing an effective late ordovician global biostratigraphical scheme as an alternative correlative tool the hice hirnantian isotopic curve excursion event is often put forward in the literature however carbon isotope chemostratigraphy shows like biostratigraphy some limits to the present state of knowledge no good independent biostratigraphical control of the hice exists in both shallow carbonate deposits and deeper shaly ones recent studies have also demonstrated inconsistencies between carbon isotopic signals obtained from organic 13corg and inorganic 13ccarb carbon species further complicating the use of the hice as an isochronous benchmark all of these difficulties for hirnantian event stratigraphy are discussed in detail in order to enable them to be overcome in the future precise late ordovician and early silurian event stratigraphies are essential for the understanding of the mechanisms linked to the first of the big five extinctions

spatio temporal variability in elevation changes of two high arctic valley glaciers uncertainties in estimates of glacier and ice cap contribution to sea level rise exist in part due to poor quantification of mass balance errors particularly those resulting from extrapolation of sparse measurements centre line data are often assumed to be representative of the glacier as a whole with little attention paid to extrapolation errors or their effect on mass balance estimates here we present detailed digital elevation model dem measurements of glacier wide elevation changes over the last 40 years at two glaciers on svalbard norwegian arctic austre broggerbreen and midtre lovenbreen are shown to have lost 27 54 0 98 and 9 65 0 76 10 7 m 3 of ice respectively between 1966 and 2005 findings that we relate to trends in average summer air temperatures and winter accumulation these volume losses correspond to geodetic balances of 0 58 0 03 and 0 41 0 03 m w e a 1 respectively our analysis revealed high spatial complexity in patterns of elevation change varying between glaciers between measurement intervals and within and between elevation bins balances from extrapolated centre line geodetic data were the same within errors as those from full coverage dem differencing in the majority of comparisons yet significantly underestimated balance in three instances additionally field mass balance from centre line ablation stake data underestimated balances from full coverage geodetic measurements during three of six measurement periods these findings may support the hypothesis that field measurements under estimate svalbard glacier mass loss at least partly as a result of the failure of centre line measurements to account for glacier wide variations in ablation our results demonstrate the importance of deriving accurate interpolation functions and constraining extrapolation errors from sparse measurements

reefs during the multiple crises towards the ordovician silurian boundary anticosti island eastern canada and worldwide multiple latest ordovician rawtheyan hirnantian glaciations in central africa with concomitant global sea level lowstands and cooler restricted equatorial carbonate shelves and ramps interrupted by warmer interstadial highstands had a dramatic global impact on the tropical shallow water reef ecosystem and carbonate production with the ordovician silurian boundary strata on anticosti island as a global standard for a carbonate shelf ramp setting the latest ordovician and earliest silurian reveal three reef phases ended by three extinctions the first extinction towards the end of the rawtheyan affected the last richmondian type reefs vaureal formation mill bay member the second extinction was less pronounced ending with reefs at the base of the prinsta member ellis bay formation interpreted as the top of the normalograptus extraordinarius graptolite subzone the third and most severe extinction phase capped the laframboise patch reef complex ellis bay formation at the top of the no

recent warming of mountain permafrost in svalbard and scandinavia 1 three deep boreholes 100 m in mountain permafrost were recently drilled in svalbard janssonhaugen and in scandinavia tarfalaryggen and juvvasshoe for long term permafrost monitoring these holes form part of a latitudinal transect of boreholes in permafrost through europe established by the permafrost and climate in europe pace project six year thermal time series data collected from the three boreholes are presented these data provide the first opportunity for temporal trends in permafrost temperatures in svalbard and scandinavia to be analyzed results show that the permafrost has warmed considerably at all three sites significant warming is detectable down to at least 60 m depth and present decadal warming rates at the permafrost surface are on the order of 0 04 0 07 c yr 1 with greatest warming in svalbard and in northern scandinavia the present regional trend shows accelerated warming during the last decade

glacier and permafrost signals of 20th century warming currently available evidence of 20th century warming from glaciers and permafrost is briefly reviewed the signals are clear and strong warming of polar firn and permafrost and mass losses of glaciers at lower latitudes were most striking towards the middle of the century the easily observable length reduction of mountain glaciers confirms the global character of the evolution a probably intermittent reversal of the trend was observed in places after about 1950

styles of sedimentation beneath svalbard valley glaciers under changing dynamic and thermal regimes glacier beds provide crucial information concerning past and present ice dynamics and thermal regime in this paper we present structural and sedimentological data from four valley glaciers austre lovenbreen midtre lovenbreen vestre lovenbreen and austre broggerbreen on broggerhalvoya nw spitsbergen the main focus of this paper is midtre and austre lovenbreen two typical high arctic land based polythermal valley glaciers the former has a long record of documentation regarding its response to twentieth century climatic warming structural mapping on the glacier surface and analysis of sediments in the proglacial area of midtre lovenbreen indicate that the dynamic regime and thermal structure of the glacier have changed through time dynamically midtre lovenbreen was once heavily crevassed and relatively fast moving but now is virtually crevasse free and slow moving the sedimentary record indicates that extensive areas of this glacier were wet based when it was in a more advanced state probably at its neoglacial maximum late nineteenth early twentieth centuries during this advance a thin deforming layer of diamicton commonly fluted was draped over the existing morphology in the presently exposed proglacial area this morphology consisted of large streamlined ridges aligned parallel to ice flow erosion of the underlying bedrock appears to have been limited radio echo soundings of the glacier show that at present it is characterized by a polythermal basal thermal regime with wet based subglacial conditions only beneath its thicker parts modification of the bed is limited under this thermal regime and as a result the supraglacial environment dominates modern sedimentation comparative studies on austre lovenbreen which also is probably polythermal indicate similar sedimentary characteristics and facies associations although here there are much more extensive areas of striated bedrock indicative of former basal sliding in contrast both austre broggerbreen and by analogy vestre lovenbreen are known to be predominantly cold based collectively these four glaciers suggest a trend of glacier recession and thinning accompanied by a change in thermal regime from predominantly wet based through partly frozen to completely frozen this study suggests that svalbard valley glaciers have several dynamic modes and that glaciers switch between these modes largely as a reaction to changes in mass balance

thermal characteristics and impact of climate change on mountain permafrost in iceland 1 this study contains the first quantitative description of mountain permafrost in iceland obtained through analysis of four ground temperature time series from recently established shallow boreholes at high altitude 900 m above sea level in central and eastern iceland permafrost is present at three of the four boreholes where temperatures range from 2 to 0 c during the data logging period 2004 2006 the thickness of the active layer at the individual sites varied between less than 2 m and more than 5 m mainly owing to differences in near surface ice content the ground temperature profiles are nonlinear with near surface temperature perturbations considered to be related to a recent warming of the ground surface at the one nonpermafrost site the insulating influence of winter snow cover is more pronounced a one dimensional heat conduction model was calibrated using ground temperature measurements and driven by surface temperature time series the model results reproduce the measured ground temperature pattern well this simplified model simulating the results of possible future climate scenarios indicates that permafrost degradation will occur at these sites within decades depending on climate scenarios chosen and subsurface ice content

polychaete palaeoecology in an early late ordovician marine astrobleme of sweden the post impact dalby limestone kulcruse upper ordovician of the tvaren crater southeastern sweden has been analysed with regards to polychaetes as represented by scolecodonts a palaeoecological succession is observed in the tvaren 2 drill core sequence as the vacant ecospace was successively filled by a range of benthonic nektonic and planktonic organisms scolecodonts belong to the first non planktonic groups to appear and constitute one of the most abundant fossil elements the polychacte assemblage recorded has an overall composition characteristic of that of the upper ordovician of baltoscandia oenonites vistulella mochtyella and the enigmatic xanioprion represent the most common genera whereas pteropelta protarabellites atraktoprion and xanioprion are considerably more rare the assemblage differs from coeval ones particularly in its poorly represented ramphoprionid fauna and the relatively high frequency of xanioprion a taxonomic succession and changes in abundance and relative frequency of different taxa is observed from the deepest part of the crater and upwards towards more shallow water environments the initial post impact assemblage does not however necessarily represent a benthonic colonization of the crater floor instead it seems to be a taphocoenosis as indicated by its taxonomic correspondence to the rim facies fauna recovered from dalby limestone erratics of the ringson island the tvaren succession has yielded considerably richer scolecodont assemblages than hitherto recorded from the approximately coeval lockne crater possibly as a consequence of shallower water settings in the former area

quantification of historical landscape change on the foreland of a receding polythermal glacier horbyebreen svalbard the assessment of multidecadal scale change in a polythermal glacial landsystem in the high arctic is facilitated by a quantitative approach that utilises time series of aerial photographs satellite images digital elevation models and field geomorphological mapping the resulting spatiotemporal analysis illustrates a transition from glacial to proglacial paraglacial conditions indicating that 1 the areal coverage of ice between the maximum lia extent and 2013 decreased from 29 35 to 16 07 km2 which is a reduction in the glacierized area in the catchment from 62 to 34 2 the ice volume loss in the proglacial area amounted to 214 9 3 million m3 which was attributed mostly to ablation of the glacier snout but to a lesser extent the degradation of ice cored landforms 3 the transition from areas formerly covered by glacier ice to ice cored moraines glacifluvial deposits and other landforms was the most intense in the period 1990 2013 4 two end member scenarios polythermal glacial landsystem domains evolve during glacier recession each one dictated by the volume of debris in englacial and supraglacial positions and include a subglacial surfaces limited englacial and supraglacial debris related to temperate basal ice and b ice cored lateral moraines and moraine mound complexes significant supraglacial debris accumulations related to marginal cold based ice an additional assemblage of geometric ridge networks discrete or linear englacial and supraglacial debris concentrations relates to crevasse and hydrofracture infill branching out from an esker complex and is indicative of either surging or later rapid release of pressurised meltwater from temperate to cold based parts of the former glacier snout

vagrant benthos annelida polychaeta associated with upper ordovician carbonate mud mounds of subsurface gotland sweden micropalaeontological investigations of upper ordovician carbonate mud mounds and enclosing strata of subsurface gotland sweden demonstrate that jaw bearing polychaetes formed the most diverse faunal element associated with these build ups although not present within the mound cores intra mound facies scolecodonts or polychaete jaws occur abundantly immediately below and particularly above the mounds the supra mound facies also has the most diverse fossil assemblages by contrast to the scolecodont distribution the most diverse conodont faunas were recorded in the intra mound facies this reinforces the fact that scolecodont and conodont abundance and diversity numbers are commonly inverse to one another suggesting that these metazoans occupied different niches and responded differently to taphonomical processes the polychaete assemblage has no less than 27 species belonging to 12 genera of which oenonites mochtyella and pistoprion are the most abundant the assemblage has a characteristic baltic signature and is similar in taxonomic composition to coeval ones from other areas of the baltoscandian palaeobasin such as that of present day estonia a principal component analysis clusters the gotland assemblage most closely to those recorded from shallow to transitional shelf environments of estonia indicatino that the mud mounds were formed in such environments less

the thermal regime of sub polar glaciers mapped by multi frequency radio echo sounding radio echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale radar signals of 320 370 mhz penetrate ice at sub freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water radar signals of 5 20 mhz on the other hand see through both the cold and the temperate ice down to the glacier bed radio echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in svalbard kongsvegen uversbreen midre lovenbreen and austre broggerbreen in the ablation area of kongsvegen a cold surface layer 50 160m thick was underlain by a warm basal layer which is advected from the temperate accumulation area the surface ablation of this cold layer may be compensated by freezing at its lower cold temperate interface this requires that the free water content in the ice at the freezing interface is about 1 of the volume the cold surface layer is thicker beneath medial moraines and where cold based hanging glaciers enter the main ice stream on uversbreen the thermal regime was similar to that of kongsvegen a temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between kongsvegen and uversbreen where meltwater accumulates during the summer near the subglacial lake setevatnet 250 m a s l lovenbreen was frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer up to 50m thick was fed by temperate ice from two cirques on austre broggerbreen a temperate basal layer was not detected by radio echo soundings but the basal ice was observed to be at the melting point in two boreholes

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

phytoplankton dynamics across the ordovician silurian boundary at low palaeolatitudes correlations with carbon isotopic and glacial events the late ordovician culminated in a major glacial period that has been related to one of the strongest mass extinctions recorded during the phanerozoic during this interval anticosti island quebec eastern canada was located at low to intermediate palaeolatitudes 15 30 s on the eastern margin of laurentia it displays a relatively complete section across the ordovician silurian o s boundary upper ordovician to lower silurian strata of anticosti studied here comprise the vaureal katian ellis bay hirnantian and becscie latest hirnantian rhuddanian formations phytoplankton dynamics inferred from the acritarch content of these strata are locally compared with new geochemical environmental proxies 13c with recent palynological data from baltica and also with phytoplankton dynamics as described from near polar high latitude localities of the gondwana region two positive excursions of the carbon isotope record have been identified in the lower and upper ellis bay formation overall phytoplankton trends are as follows 1 as with chitinozoans conodonts brachiopods and corals acritarchs from anticosti display a major turn over during the early hirnantian uppermost vaureal formation lower ellis bay formation with the appearance of taxa that exhibit silurian affinities e g tylotopalla sp ammonidium sp oppilatala sp evittia sp dilatisphaera spp high polymorphism for some common taxa is observed in the interval corresponding to the first 13c positive excursion using sequence stratigraphy this period may be related to a first glacially driven sea level drawdown corresponding to terrestrial ice sheet growth on gondwana such as recorded in morocco 2 subsequently during the late hirnantian of anticosti uppermost ellis bay formation phytoplanktic communities suffered a crisis exemplified by the disappearance of several typical large late ordovician taxa i e orthosphaeridium spp peteinosphaeridium spp large baltisphaeridum spp sacculidium sp the lower becscie strata corresponding to the time of deglaciation at the o s boundary interval only contain a low diversity assemblage dominated by large acritarchs of the genus hoegklintia and other morphologically related forms and a few tolerant and long ranging taxa e g evittia remota micrhystridium spp leiospheres despite a possible taphonomic bias in the uppermost ellis bay formation the major crisis in the late hirnantian coincides with the second 13c excursion and a second stronger glacially driven sea level fall corresponding to the time of the maximum extend of the ice sheets on gondwana 3 such phytoplankton events have also been detected in gondwanan ice center area but with typical ordovician taxa crises occurring apparently later when plotted against positive carbon isotope excursions as also observed in baltica this time lag may be linked to a basin configuration of the studied areas where environmental stress consequently differed or linked to the presence of omission surfaces coupled with preservation bias of acritarch assemblages in the uppermost ordovician strata of anticosti in addition to their biostratigraphic and palaeobiogeographic utility acritarchs turn out to be more specific in highlighting palaeoenvironmental conditions

depositional conditions of the bathonian to hauterivian janusfjellet subgroup spitsbergen abstract the janusfjellet subgroup was formed under shallow marine shelf conditions dominated by sedimentation of clay but silt and sand also accumulated in significant amounts the sand bodies recognized in the agardhfjellet formation bathonian b are redeposition of sediments originating from earlier deltaic coastal progradation the rurikfjellet formation berriasian hauterivian reveals an upwards increasing sand content reflecting built out of a delta system the prodeltaic material was partly reworked by storm currents the shales of the agardhfjellet formation were in part deposited under oxygen depleted conditions

spatial distribution and controls of permafrost development in non glacial arctic catchment over the holocene fuglebekken sw spitsbergen abstract this article presents the distribution and properties of the permafrost based on electrical resistivity tomography ert and multichannel analysis of surface waves masw data collected at the fuglebekken coastal catchment area in sw spitsbergen this work summarizes the development of permafrost in this area during the holocene from the mountain environment through to the system of elevated marine terraces found around the coast the ert models were analysed taking into consideration the non unique nature of the data inversion process and the physical limitations of this method comparing the ert and the masw results allows a zonal characterization of the occurring ice bearing permafrost and its correlation with the evolution history of the catchment area maritime transgression as well as intensive watercourses during past degradation episodes have altered the permafrost presence and ice accumulating abilities of different sediment zones permafrost development depends greatly on the presence of surface watercourses in talus slopes the youngest elevated uplifted marine terrace did not develop an ice rich permafrost but the presence of permafrost in a cryotic form is possible the significant range of the fjord water infiltration found within the sedimentary cover have influenced the development of the coastal permafrost the current structure of ice bearing permafrost found in the research area seems to be very sensitive to the climatic changes based on these results we propose a model for the formation of the current permafrost in the studied area

estimation of ground surface temperatures from borehole temperature data to infer past climatic changes from temperatures measured in boreholes one must obtain reliable estimates of ground surface temperature gst histories from these data this paper presents a method that uses a bayesian inverse technique to estimate the gst in the fourier frequency domain by assuming the a priori gst to be stationary with a prescribed standard deviation and a cutoff period the time series is constrained to be bounded and smooth because accounting for conductivity variations with depth is crucial to the estimation of gst a layered earth medium has been used for which the forward analytical solution of one dimensional heat conduction is available borehole data from flin flon and lac dufault in canada are inverted with this method the flin flon hole logged to a depth of 2900 m provides an opportunity to study long term gst variations and the estimated gst from this hole shows some effects of deglaciation at the end of pleistocene at lac dufault similar gsts were obtained independently from three holes ranging from 550 to 900 m and hence the results are considered more reliable in the lac dufault gsts there is a warm period centered about 1000 years bp and a cold period about 400 years b p confirming the presence of the little climatic optimum and the little ice age respectively the flin flon result does not show the little climatic optimum and the little ice age occurs about 100 200 years earlier however in both locations the gsts show another brief cold period around the turn of the century followed by rapid warming until 1940 1950 in good agreement with the trend of northern hemisphere surface air temperatures

late glacial climate in northern eurasia the last climatic cycle abstract analysis of palynomorphic coleoptera mammalian and geomorphic evidence throughout europe indicates that three distinctive cooling phases designated older middle and younger dryas can be recognized during late glacial time each subsequent cold interval was less intense than the preceding one with the younger dryas representing the warmest of the three episodes similarly the later allerod interval was warmer and more intense than the earlier bolling event consequently the overall pattern throughout the late glacial holocene transition was climatic warming climate changes throughout northern eurasia are directly related to fluctuations in sea level along the arctic ocean coast and to the establishment of anti cyclones over siberia and scandinavia

terminal ordovician carbon isotope stratigraphy and glacioeustatic sea level change across anticosti island quebec canada globally documented carbon isotope excursions provide time varying signals that can be used for high resolution stratigraphic correlation we report detailed inorganic and organic carbon isotope curves from carbonate rocks of the ellis bay and becscie formations spanning the ordovician silurian boundary on anticosti island quebec canada strata of the anticosti basin record the development of a storm dominated tropical carbonate ramp these strata host the well known hirnantian positive carbon isotope excursion which attains maximum values of 4 5 in carbonate carbon of the laframboise member or the fox point member of the becscie formation the excursion also occurs in organic carbon and 13 c carb and 13 c org values covary such that no reproducible 13 c 13 c carb 13 c org excursion is observed the most complete stratigraphic section at laframboise point in the west shows the characteristic shape of the hirnantian stage excursion at the global stratotype section and point gssp for the hirnantian stage in china and the silurian system in scotland we therefore suggest that the entire hirnantian stage on anticosti island is confined to the laframboise and lower fox point members by documenting discontinuities in the architecture of the carbon isotope curve at multiple stratigraphic sections spanning a proximal to distal transect across the sedimentary basin we are able to reconstruct glacioeustatic sea level fluctuations corresponding to maximum glacial conditions associated with the end ordovician ice age the combined litho and chemostratigraphic approach provides evidence for the diachroneity of the oncolite bed and becscie limestones the former transgresses from west to east and the latter progrades from east to west the sea level curve consistent with our sequence stratigraphic model indicates that glacioeustatic sea level changes and the positive carbon isotope excursion were not perfectly coupled although the start of the isotope excursion and the initial sea level drawdown were coincident the peak of the isotope excursion did not occur until after sea level had begun to rise carbon isotope values did not return to baseline until well after the anticosti ramp was reflooded the sea level 13ccarb relationship proposed here is consistent with the weathering hypothesis for the origin of the hirnantian 13 c carb excursion

mass balance change as a control on the frequency and occurrence of glacier surges in svalbard norwegian high arctic the end of the little ice age lia in svalbard 76 81 n a climate sensitive region at the northern extreme of strong poleward heat transfer was marked by an abrupt increase in mean annual air temperature of up to 5 c around 1920 glacier mass balance has been consistently negative since this time and large cumulative net losses of mass have occurred at most glaciers energy balance modelling confirms the sensitivity of svalbard glaciers to climate change predicting a negative shift in net mass balance of up to 0 8 m a 1 water equivalent per degree temperature rise this climate related shift in glacier mass balance has reduced the intensity of glacier surge activity in svalbard one glacier known to have surged since the end of the lia has since failed to accumulate the mass required to re initiate the surge cycle and is also now cold at its base and incapable of rapid flow by basal sliding three overviews of the total number of actively surging glaciers in svalbard between 1936 90 show a decrease from 18 to 5 this is significant compared with the expected numbers of surges based on lia conditions post lia climate change in svalbard has therefore affected not only glacier extent but also ice dynamics this is trend will probably continue given co2 induced climate warming

measurement and simulation of snow and superimposed ice at the kongsvegen glacier svalbard spitzbergen 1 multiyear glaciometeorological data have been collected at about the equilibrium line of kongsvegen glacier in svalbard during the first summer of the investigation period about 0 6 m of superimposed ice si was built up because of effective meltwater refreeze upon the former glacier surface thus winter accumulation is completely retained from runoff and latent heat is released equivalent to 27 of july net radiation this ice layer as well as part of the former year s ice disappeared during the subsequent summer using a physically based snow model the evolution of the snow pack properties as well as the observed amount of si is successfully reproduced however the latter is only possible by modifying the model s water transport routine to also treat effects of ponding water which have been observed two distinct phases of si formation can be distinguished a first one 15 cm is initiated as soon as meltwater has penetrated to the underlying cold glacier ice toward the end of the melt period however the remaining body of si is rapidly formed because of intense atmospheric cooling the availability of ponding water plays an essential role in this context during the following summer the initial refreezing phase was terminated by exposure of the newly built si at the surface the whole amount of the actual year and the major part of the former year s si was melted then a positive ice albedo feedback process plays an additional role there sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters despite their local nature these studies are valuable steps toward understanding the regional distribution of si on arctic glaciers as well as their climate sensitivity remote sensing studies indicate that si presently covers 35 of kongsvegen s surface area

the influence of drifting snow on the location of glaciers on western spitsbergen svalbard on western spitsbergen svalbard the amount of winter precipitation is insufficient to maintain the present day mass balance of the local glaciers additional snow mass must be added to the precipitation to reach the observed accumulation rates of the glaciers it was assumed in previous work that this additional mass is transported onto the glaciers by drifting snow and snow avalanches this study is a first attempt to quantify the amount of snow mass added to the glacier mass balance by wind transported snow the wind field over an area of 60 50 km2 on western spitsbergen was simulated for 24 idealized weather types by a mesoscale meteorological model on a 750 m grid the resulting wind velocities and directions were coupled to a two level snowdrift model the model output clearly shows erosion and accumulation areas in the terrain comparison with the present glacier locations suggests that the glacier accumulation areas coincide with low wind speeds moreover exposed areas with high wind speeds are mostly glacier free in reality thus the wind field and corresponding snowdrift gives an indication of the location of the present glaciers on western spitsbergen

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

chitinozoan biostratigraphy of a new upper ordovician stratigraphic framework for anticosti island canada thickness and facies variations in the upper ordovician succession of anticosti island have made correlations between the western and eastern ends of the island difficult this chitinozoan study reveals that most strata of the ellis bay formation at the eastern end of the island correlate with the vaureal formation at the western end in the eastern end chitinozoans typical of the ellis bay formation occur only in the upper part of the lousy cove member whereas chitinozoans diagnostic of the mid upper vaureal occur in the rest of the formation moreover the eastern schmitt creek and mill bay members of the vaureal formation are older than the uppermost vaureal eponym members in the western end new east west correlations supported by geochemical sedimentological and sequence stratigraphic data are proposed comparison with coeval upper ordovician successions suggests a hirnantian age for the gamachiana zone that occurs in the lower members of the ellis bay formation it also indicates that the hirnantian isotopic carbon excursion hice on anticosti begins in the d anceps zone just below the base of the hirnantian stage reaches a first peak in the lower n extraordinarius zone a second modest peak high in the n extraordinarius zone and a third more important one in the lower part of the n persculptus zone these results are in agreement with the biostratigraphic and chemostratigraphic data at the global boundary stratotype section and points gssps for the base of the hirnantian and silurian in south central china and at dob9s linn in scotland

holocene palaeoecology of the eastern sahara selima oasis buried lake sediments and tufa strandlines of holocene age provide evidence of a former lake in the selima oasis depression northwest sudan near the hyperarid core of the eastern sahara desert a 1 6 m section through laminated lake muds and precipitates has been analysed in detail and 30 radiocarbon dates geochemical sedimentological diatom and pollen analyses indicate that the unit dated from approximately 8 4 ka bp to 6 ka bp and was deposited in an environment that passed through one arid to humid to arid cycle the arid episodes from prior to 8 4 ka bp and subsequent to 7 ka bp are characterized by high caco3 deposition abundant diatom indicators of relatively high salinity and well developed periphytic communities and pollen spectra dominated by desert grassland indicators a humid period centered on 8 ka bp is indicated by low caco3 deposition high organic rich mud and al and si oxide deposition diatoms indicating a fresh deep 20 m lake and a pollen assemblage with maximum values for sahelo sudanian tree taxa suggesting a thorn tree and shrub savanna vegetational mosaic this reconstruction concordant with higher groundwater table and precipitation between 9 3 and 7 ka bp agrees with palaeoecological inferences from other sites in north africa

structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard hambrey michael murray t glasser n f hubbard a 2005 structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard journal of geophysical research 110 pp 1 19 rae2008