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

quantification of the ice cored moraines short term dynamics in the high arctic glaciers ebbabreen and ragnarbreen petuniabukta svalbard abstract extensive ice cored moraine complexes are common elements marking the last advance of many svalbard glaciers sediment gravity flows are among the most dynamic processes transforming these landforms the short term yearly and weekly dynamics of mass wasting processes were studied in a cm scale using repetitive topographic scanning we monitored several active sites on the forelands of two glaciers ebbabreen and ragnarbreen both of which are located near petuniabukta at the northern end of billefjorden in spitsbergen the surveys indicate high dynamic rates of landforms transformation the mean annual volume loss of sediments and dead ice for the most active parts of the moraines was up to 1 8 m a 1 however most of the transformation occurred during summer with the short term values of mean elevation changes as high as 104 mm day 1 in comparison the dynamics of the other i e non active parts of the ice cored moraines were much lower namely the mean annual lowering attributed mainly to dead ice downwasting was up to 0 3 m a 1 whereas lowering during summer was up to 8 mm day 1 our results indicate that in the case of the studied glaciers backwasting was much more effective than downwasting in terms of landscape transformation in the glacier forelands however despite the high activity of localised mass movement processes the overall short term dynamics of ice cored moraines for the studied glaciers were relatively low we suggest that as long as debris cover is sufficiently thick thicker than the permafrost s active layer depths the mass movement activity would occur only under specific topographic conditions and or due to occurrence of external meltwater sources and slope undercutting in other areas ice cored moraines remain a stable landsystem component in a yearly to decadal time scale

multiple late holocene surges of a high arctic tidewater glacier system in svalbard abstract most large tidewater glaciers in svalbard are known to have surged at least once in the last few hundred years however very little information exists on the frequency timing or magnitude of surges prior to the little ice age lia maximum in 1900 we investigate the sediment landform assemblages produced by multiple advances of the nathorstbreen glacier system ngs in order to reconstruct its late holocene surge history the glacier has recently undergone one of the largest surges ever observed in svalbard advancing 16 km from 2008 to 2016 we present flow velocities and ice marginal observations terminus change proglacial geomorphological processes from the later stages of this surge a first detailed assessment of the development of a glaciotectonic mud apron within the fjord during a surge is provided geomorphological and sedimentological examination of the terrestrial moraine areas formed prior to the most recent surge reveals that at least two advances were responsible for their formation based on the identification of a previously unrecognised ice contact zone recorded by the distribution of sediment facies in coastal exposures we distinguish between an outer older advance to the distal part of the moraine system and an inner younger advance to a position 2 km upfjord radiocarbon dating of shells embedded in glaciotectonic composite ridges formed by the onshore bulldozing of marine mud during the outer older of the two advances shows that it occurred at some point during the interval 700 890 cal yr bp i e 1160 ad and not during the lia as previously assumed we instead attribute the inner younger advance to the lia at 1890 by combining these data with previous marine geological investigations in inner and outer van keulenfjorden we demonstrate that ngs has advanced at least four times prior to the recent 2008 2016 surge twice at 2 7 kyr bp at 1160 ad and in 1890 this represents a unique record of the timing and magnitude of late holocene tidewater glacier surges in svalbard

englacial deltaic sediments as evidence for basal freezing and marginal shearing leirbreen southern norway analyse des depots de geles de limons sables et graviers pres du front du glacier leirbreen les structures demontrent une origine deltaique les sediments ayant ete geles avant leur incorporation au glacier et n ayant pas subit de cisaillement pendant le transport glaciaire on en deduit les mecanismes de variation du glacier

holocene development and geomorphic processes at omnsbreen southern norway evidence for glacier permafrost interactions omnsbreen is a small 0 5 km2 and degrading glacier situated at the regional lower limit of present day permafrost distribution and glaciation at present the existence of omnsbreen is mainly de

the morphology structural evolution and significance of push moraines abstract push moraines glaciotectonic ice marginal moraines have a restricted distribution at modern glacier margins and consequently are of potential value in reconstructing pleistocene ice sheets providing data both on former glaciodynamics and on the palaeoenvironment of the glacial foreland to the wider earth science community push moraines are of interest as analogues for thin skin tectonics within orogenic belts this paper reviews the morphology structural geology formation and significance of push moraines the morphological and structural characteristics of small seasonal push moraines through to large multi crested examples produced by sustained glacier advances are reported before the primary controls on push moraine formation are examined these controls include the nature of the applied glacial stress field the presence and properties of decollement horizons and the shear strength and rheology of the glacial foreland a conceptual model of push moraine formation is introduced in which the range of observed morphological and structural forms are viewed within a matrix defined by the main variables which control their formation the absence of consensus over which of these variables is of greatest importance currently limits the significance of push moraines in palaeoglaciological research as a consequence this review emphasises the need for future research in order to realise the true potential of push moraine in the reconstruction of pleistocene environments

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

fractures as collections of cracks abstract a single fracture can be thought of as two rough surfaces in partial contact observations show that the noncontacting regions are patches of widely varying size and shape which are characterized by an aperture which is much less than any of the in plane dimensions a further idealization is therefore to assume that the regions of contact are welded and the noncontacting patches are replaced by cracks the deformation of cracks arranged in simple two dimensional 2 d geometries can be described analytically solutions for noninteracting and interacting cracks are reviewed and the analogy with solutions for ubiquitously cracked intact rock is discussed using the model of a fracture as a two dimensional collection of cracks expressions for fracture stiffness flow of a single phase fluid through a fracture and propagation of elastic waves across a fracture are formulated comparison with observations shows that this simple model provides a consistent description of many first order attributes of the mechanical deformation and fluid flow in fractures under normal stress and the velocity and amplitude of seismic waves propagating in fractured rock

permafrost active layer abstract this article discusses the properties and occurrence of an active layer al in the near surface of the lithosphere in glacial and periglacial environments this layer shows a seasonal variability in temperature as a result of the climate the al as classically understood seasonally thaws and freezes while in glacial environments it usually only reaches 0 c the definition of al is currently not consistent with the definition of permafrost even though both concepts usually appear linked for these terms to be comparable both should be defined based on temperature variability and not exclusively on phase change thus the al would be described not only as the upper section of perennially frozen ground presenting seasonal thaw freeze cycles 1 but as a layer presenting a seasonal variation in temperature 2 classical active layer can be thawed to a depth of approximately 2 8 cm the thickest al reaches over 20 m in the particularly favorable conditions al might be completely absent with the permafrost beginning at the ground surface in glacial and sub marine permafrost environments the al includes a layer of liquid water that seasonally accompanies the permafrost glaciers and ice sheets are usually devoid of the classical al in both cases the al is usually horizontal but in specific terrains such as sea shore cliffs or karst environments the al may have a vertical course and may even be reversed both al and permafrost are common in other frozen bodies in the solar system differing mainly in their thermal character

pioneer zone geo ecological change observations from a chronosequence on the storbreen glacier foreland jotunheimen southern norway abstract the first 33 years of primary geo ecological succession is investigated in the pioneer zone of the storbreen glacier foreland using the chronosequence approach pitfall trapping of invertebrates and the sampling of higher and lower plants and habitat factors from quadrats were used on three replicate transects across a till plain accurately dated by annually monitored glacier front variations combined with the mapping of annual moraine ridges unstable saturated sediments deglacierized for

suspended sediment fluxes in a high arctic glacierised catchment implications for fluvial sediment storage suspended sediment fluxes from the 68 km2 finsterwalderbreen catchment in svalbard were monitored intensively during the 1999 and 2000 melt seasons at proximal and distal ends of a 4 2 km2 proglacial area which has been deglacierised during the twentieth century measured distal sediment fluxes correspond to total catchment denudation rates of 2700 710 t km 2 year 1 1999 and 1800 350 t km 2 year 1 2000 hourly net sediment flux time series distal flux minus proximal flux isolating change within the proglacial area itself reveal that the proglacial area serves as both a source and a sink of sediment during different periods of the melt season and that the majority of sediment evacuation from the area occurs during discrete episodes of enhanced meltwater discharge the mean net flux from the proglacial area itself was 690 230 t km 2 year 1 1999 and 3800 1700 t km 2 year 1 2000 therefore in 1999 there was a net increase in sediment storage in the proglacial area aggradation and in 2000 there was a net decrease denudation the pattern of sediment storage change appears to be driven by the runoff regime with net storage occurring during a year of relatively episodic sediment transport in which relative supply exhaustion occurs and net release in a year of more sustained sediment transport when relative supply exhaustion is absent many more years monitoring would be required for any trend to emerge from the large interannual variability in sediment yield

the sedimentary and structural evolution of a recent push moraine complex holmstrombreen spitsbergen abstract the glacier holmstrombreen in spitsbergen surged into the ice contact scarp of a proglacial outwash sequence at some time during its neoglacial maximum the outwash sediments were pushed along a decollement to produce a moraine in which deformation extended for 1 5 km beyond the furthest extent of the glacier front the style of folding and faulting and the nature of the pre syn and post tectonic sedimentary sequence across the whole push moraine is described from a continuously exposed section of the push moraine which extends from its proximal to distal extremities the precise extent of incremental compressive shortening of the pushed sediments of some 900 m is established the depth to the underlying decollement is inferred to be an average of about 30 m indicating that stresses and movement were transmitted through a thin nappe with an aspect ratio of about 1 in 30 it is suggested that this nappe was frozen and that an artesian water pressure head of 60 m immediately beneath it reduced friction along its base to a very low value it is calculated that a glacially generated force of about 1 5 10 7 kn was responsible for pushing the sediment nappe the nature of the glacially controlled groundwater flow system rather than the magnitude of longitudinal forces generated by the glacier is the principle determinant of large scale push moraine characteristics the changing ice topography produced by the pushing event during the surge and in the post surge decay had a major influence on the evolution of the meltwater drainage system and the style of fluvial sedimentation the structure sedimentary architecture and evolution of the whole glacitectonic fluvial complex can best be understood by considering the impact of the surge on a complete outwash system it is suggested that the setting and processes which produced the holmstrombreen push moraine could account for many broad multi ridge and fold push moraines which formed proglacially and that the thickness of original sediments above the decollement can be a guide to the thickness of contemporary permafrost

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

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

sedimentary imprints of former ice sheet margins insights from an end ordovician archive sw libya fromthe proterozoic to the quaternary the evolution of the earthwas characterised by recurrent periods of glaciation however the margins of many ancient ice sheets are poorly defined on palaeogeographic reconstructions the extent and outlines of ancient ice sheets can be better understood through careful documentation of sediments deposited at the ice sheet margin an outstanding example is provided herein based on an end ordovician archive in libya tihemboka area murzuq basin the four sets of structures include i subglacial glaciotectonic structures and soft sediment deformations from flowing glacier ice such as intraformational glacial striae intraformational deformation shear planes sheath folds normal microfaults and large scale glaciotectonic folds and thrusts ii structures resulting from overpressured subglacial meltwater flows such as clastic dykes and tunnel valleys iii proglacial depositional structures and facies related to highmagnitude meltwater floods such as sandstone intraclasts large scale bedforms resulting from supercritical flows climbing dune cross stratification and kettle holes and iv deformation structures resulting from free floating and nonglacier ice such as ice keel scours and ice crystal marks such a set of structures points to an ice marginal essentially continental depositional setting and provides an excellent suite of criteria to identify margins of ancient ice sheets in the stratigraphic record at a regional scale a reconstruction through time and space of the related depositional wedge is proposed this corresponded to a seismic scale n120 m in thickness 40 km in length ice marginal wedge in front of an essentially warm based ice sheet inducing concomitant large scale glaciotectonic deformation glacial basin and tunnel valley downcuttings the related ice front was associated with high energy meltwater flows feeding a network of deeply incised proglacial channels downstream and beyond them a fluvioglacial deltaic system shallow ice marginal permafrost most likely affected the depositional wedge at a larger scale the tihemboka ice marginal wedge is interpreted as related to a stillstand period over the gondwana platform developed over an estimated interval of a few thousands of years based on these data the conditions that arose in a particularly favourable context for the development the preservation and the identification of ice marginal wedges in the geological record are reviewed significant meltwater derived sediment deposition and aggradation in an accommodation space resulting either from preglacial inheritance glacial downcuttings and or glacio isostatic lithospheric flexure or active tectonic subsidence 1 myr are required for their formation and subsequent preservation

holocene hillslope development in glacially formed valley systems in nordfjord western norway abstract large areas of the norwegian fjord landscapes are covered by hillslopes that reflect the influence of glacial inheritance from the last glacial maximum lgm the focus of this paper is two fold 1 analyze the spatio temporal variability of relevant denudational slope processes and process intensities over the holocene and 2 detect holocene modification of the glacial valley morphometry research was performed on hillslope systems within two steep parabolic shaped and glacier fed tributary valleys erdalen and bodalen located on the western side of the jostedalsbreen ice cap in western norway orthophoto delineation high resolution mapping tls detailed geomorphological information and spatial data analysis were combined with dating techniques and geophysical investigations calculated holocene rockwall retreat rates at selected slope test sites range from 0 38 to 0 67 mm yr 1 with a mean value of 0 53 mm yr 1 slightly higher values were found in erdalen with a mean rockwall retreat rate of 0 57 mm yr 1 compared to 0 50 mm yr 1 in bodalen valley wide holocene rockwall retreat rates of 0 38 0 50 mm yr 1 are consistent with other estimates of holocene rockwall retreat rates in cold mountain environments it is shown that the glacial inheritance of topography is the most important factor controlling valley development since the lgm and that sediment storage capacity is primarily conditioned by valley morphometry compared to contemporary rates the results indicate enhanced denudation activity and intensity immediately following deglaciation and during the little ice age the overall tendency of landscape development is postglacial widening of the parabolic shaped valley morphometry through rockwall retreat with associated debris accumulation beneath rockwalls as a result the glacially sculpted topography has not yet adapted to denudational processes acting under holocene environmental conditions

evolution of high arctic glacial landforms during deglaciation abstract glacial landsystems in the high arctic have been reported to undergo geomorphological transformation during deglaciation this research evaluates moraine evolution over a decadal timescale at midtre lovenbreen svalbard this work is of interest because glacial landforms developed in svalbard have been used as an analogue for landforms developed during pleistocene mid latitude glaciation ground penetrating radar was used to investigate the subsurface characteristics of moraines to determine surface change a lidar topographic data set obtained 2003 and a uav derived obtained 2014 digital surface model processed using structure from motion sfm are also compared evaluation of these data sets together enables subsurface character and landform response to climatic amelioration to be linked ground penetrating radar evidence shows that the moraine substrate at midtre lovenbreen includes ice rich radar velocities of 0 17 m ns 1 and debris rich radar velocities of 0 1 0 13 m ns 1 zones the ice rich zones are demonstrated to exhibit relatively high rates of surface change mean thresholded rate of 4 39 m over the 11 year observation period however the debris rich zones show a relatively low rate of surface change mean thresholded rate of 0 98 m over the 11 year observation period and the morphology of the debris rich landforms appear stable over the observation period a complex response of proglacial landforms to climatic warming is shown to occur within and between glacier forelands as indicated by spatially variable surface lowering rates landform response is controlled by the ice debris balance of the moraine substrate along with the topographic context such as the influence of meltwater site specific characteristics such as surface debris thickness and glaciofluvial drainage are therefore argued to be a highly important control on surface evolution in ice cored terrain resulting in a diverse response of high arctic glacial landsystems to climatic amelioration these results highlight that care is needed when assessing the long term preservation potential of contemporary landforms at high arctic glaciers a better understanding of ice cored terrain facilitates the development of appropriate age and climatic interpretations that can be obtained from palaeo ice marginal landsystems

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

glaciation of alpine valleys the glacier debris covered glacier rock glacier continuum abstract alpine ice varies from pure ice glaciers to partially debris covered glaciers to rock glaciers as defined by the degree of debris cover in many low to mid latitude mountain ranges the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized instead valley heads are more likely to be populated by rock glaciers which can number in the hundreds these rock cloaked glaciers represent some of the most identifiable components of the cryosphere today in low to mid latitude settings and the over steepened snouts pose an often overlooked hazard to travel in alpine terrain geomorphically rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs in this work we show how rock glaciers can be treated as an end member case that is captured in numerical models of glaciers that include ice dynamics debris dynamics and the feedbacks between them specifically we focus on the transition from debris covered glaciers where the modern equilibrium line altitude ela intersects the topography to rock glaciers where the modern ela lies above the topography on debris covered glaciers i e glaciers with a partial rock mantle rock delivered to the glacier from its headwall or from sidewall debris swept into the glacier at tributary junctions travels englacially to emerge below the ela there it accumulates on the surface and damps the rate of melt of underlying ice this allows the termini of debris covered glaciers to extend beyond debris free counterparts thereby decreasing the ratio of accumulation area to total area of the glacier aar in contrast rock glaciers i e glaciers with a full rock mantle occur where and when the environmental ela rises above the topography they require avalanches and rockfall from steep headwalls the occurrence of rock glaciers reflects this dependence on avalanche sources because they are most common on lee sides of ridges and peaks where wind blown snow enhances the strength of the avalanche source to maintain positive mass balance the avalanche cone developed in the winter must be sufficiently thick not to melt entirely in the summer thus providing an ice accumulation area for the rock glacier in the absence of rockfall this would support a short cirque glacier the presence of debris however facilitates the development of rock glaciers with lengths of hundreds of meters thicknesses of tens of meters and speeds of meters per year that are well described by numerical models numerical models are used to explore the alpine glacier response to its climate history in warming climates a debris covered glacier can transform into a much shorter rock glacier leaving in its wake a thinning ice cored moraine rock glaciers will persist in landscapes well beyond debris free counterparts because they have much longer response times to climate change the headwaters of alpine basins with steep headwalls will therefore oscillate between glacier and rock glacier occupation over glacial interglacial cycles maintaining a means by which rock from the headwall can be conveyed away this enhances the asymmetry of alpine ridgelines with downwind valleys biting deeply into the range crests as originally noted by g k gilbert

the concept of cryo conditioning in landscape evolution comment to the paper published by ivar berthling and bernd etzelmuller quaternary research 75 2011 378 384 abstract the term cryo conditioning proposed by the authors for classifying specific landform association in periglacial landscapes needs to be defined more precisely a starting point could be the proper understanding of the term cryo in the various compound words found in various disciplines this is also important for a correct understanding of the proposed concepts since it concerns one of the most important processes in nature the phase transition of water between solid and liquid cold temperate transition surfaces in polythermal glaciers and at the permafrost base in their forelands can act as a specific hub between the glacial and periglacial domains

landscape evolution and ice sheet behaviour in a semi arid polar environment james ross island ne antarctic peninsula this study of landscape evolution presents both new modern and palaeo process landform data and analyses the behaviour of the antarctic peninsula ice sheet through the last glacial maximum lgm the holocene and to the present day six sediment landform assemblages are described and interpreted for ulu peninsula james ross island ne antarctic peninsula 1 the glacier ice and snow assemblage 2 the glacigenic assemblage which relates to lgm sediments and comprises both erratic poor and erratic rich drift deposited by cold based and wet based ice and ice streams respectively 3 the boulder train assemblage deposited during a mid holocene glacier readvance 4 the ice cored moraine assemblage found in front of small cirque glaciers 5 the paraglacial assemblage including scree pebble boulder lags and littoral and fluvial processes and 6 the periglacial assemblage including rock glaciers protalus ramparts blockfields solifluction lobes and extensive patterned ground the interplay between glacial paraglacial and periglacial processes in this semi arid polar environment is important in understanding polygenetic landforms crucially cold based ice was capable of sediment and landform genesis and modification this landsystem model can aid the interpretation of past environments but also provides new data to aid the reconstruction of the last ice sheet to overrun james ross island

the concept of cryo conditioning in landscape evolution recent accounts suggest that periglacial processes are unimportant for large scale landscape evolution and that true large scale periglacial landscapes are rare or non existent the lack of a large scale topographical fingerprint due to periglacial processes may be considered of little relevance as linear process landscape development relationships rarely can be substantiated instead periglacial landscapes may be classified in terms of specific landform associations we propose cryo conditioning defined as the interaction of cryotic surface and subsurface thermal regimes and geomorphic processes as an overarching concept linking landform and landscape evolution in cold regions by focusing on the controls on processes this concept circumvents scaling problems in interpreting long term landscape evolution derived from short term processes it also contributes to an unambiguous conceptualization of periglacial geomorphology we propose that the development of several key elements in the norwegian geomorphic landscape can be explained in terms of cryo conditioning

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

comparison of radio echo sounding 30 1000 mhz and high resolution borehole temperature measurements at finsterwalderbreen southern spitsbergen svalbard

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

icelandic permafrost dynamics since the last glacial maximum model results and geomorphological implications abstract iceland s periglacial realm is one of the most dynamic on the planet with active geomorphological processes and high weathering rates of young bedrock resulting in high sediment yields and ongoing mass movement permafrost is discontinuous in iceland s highlands and mountains over c 800 m a s l and sporadic in palsa mires in the central highlands during the late pleistocene and holocene iceland s periglacial environment varied considerably in time and space dominated by glacial fluctuations and periglacial processes to evaluate the dynamics of permafrost in iceland since the last deglaciation we use the output of a coupled climate ice sheet model to force a transient permafrost model cryogrid 2 from the last glacial maximum lgm through to the present we find that permafrost was widespread across the deglaciated areas of western northern and eastern iceland after the lgm and that up to 20 of iceland s terrestrial area was underlain by permafrost throughout the late pleistocene this influenced geomorphological processes and landform generation the early collapse of the marine based ice sheet together with the aggradation of permafrost in these zones initiated the formation of abundant and now relict rock glaciers across coastal margins permafrost degraded rapidly after the younger dryas with a marked impact on slope stability permafrost that formed during the little ice age is again thawing rapidly and an escalation in slope failure and mass movement might be currently underway our study demonstrates that large regions of iceland have been underlain by permafrost for millennia facilitating landform development and influencing the stability of steep slopes

interpreting exposure ages from ice cored moraines a neoglacial case study on baffin island arctic canada 10be dating of moraines has greatly improved our ability to constrain the timing of past glaciations and thus past cold events however the spread in ages from a single moraine is often greater than would be expected from measurement uncertainty making paleoclimatic interpretations equivocal here we present 28 new 10be ages from ice cored neoglacial moraines on baffin island arctic canada and explore the processes at play in moraine formation and evolution through field observations and a numerical debris covered glacier model the insulating effect of debris cover modifies glacier lengths and results in the development of ice cored moraines over multiple advances and thousands of years although ice cores can persist for several millennia spatially variable ice core melt out contributes to moraine degradation and boulder destabilization making it likely that the 10be clock is reset on moraine boulders in these settings thus exposure ages from ice cored moraines must be interpreted with caution the oldest ages after excluding samples with inheritance provide the best estimates of initial moraine formation three baffin island moraines yield 10be ages suggesting formation at 5 2 4 6 and 3 5 ka respectively adding to a growing body of evidence for significant summer cooling millennia before the little ice age

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

glacier permafrost interactions processes products and glaciological implications abstract glaciers and permafrost represent key components of the global cryosphere widely held assumptions that 1 they are largely mutually exclusive and 2 glaciers resting on permafrost are slow moving and geomorphologically ineffectual have meant that glacier permafrost interactions have been given little attention within the research literature recent research however has demonstrated that such interactions are likely to have been more extensive than previously thought particularly during periods of ice sheet growth when glaciers would have advanced over pre existing permafrost work in both modern and ancient environments has revealed that subglacial processes such as basal sliding and subglacial sediment deformation can remain active at temperatures below the pressure melting point due to the persistence of premelted liquid water consequently cold based glaciers resting on permafrost are potentially more dynamic than previously thought and are capable of creating subglacial features typically viewed as only forming beneath warm based ice in addition the active coupling of cold based ice with ice marginal permafrost means such ice masses are capable of deforming sediments and occasionally bedrock to depths of tens or even hundreds of meters and are commonly associated with the development of a range of distinctive ice marginal landforms including push or thrust moraines and hummocky or controlled moraines this reflects the influence of permafrost on the entrainment of debris rich basal ice as well as the hydraulic transmissivity of the groundwater system and the associated porewater pressures within the substrate this review considers the key characteristics of permafrost and its formation likely extent and rheological behaviour within glacial environments traditional conceptions regarding the motion and landscape impact of cold based glaciers resting on permafrost are considered before their re examination in light of recent work demonstrating the operation of basal processes at sub freezing temperatures the implications for our understanding of the dynamics of glaciers and ice sheets as well as landforms and sedimentary sequences indicative of glacier permafrost interactions are explored and exemplified with reference to modern and ancient glacial environments gaps in our existing knowledge are identified and profitable areas for future research suggested

the final phase of dead ice moraine development processes and sediment architecture kotlujokull iceland consecutive phases of de icing of ice cored moraines and the formation of dead ice moraine were monitored over a 4 year period at the terminus of the kotlujokull glacier iceland particularly the transition from partially ice cored moraine with isolated dead ice blocks to the ice free landscape receives attention in this paper in order to link the final melting processes to the architecture of the sedimentary end product in the current humid sub polar climate of south iceland de icing of partially ice cored moraines results chiefly from melting along the bottom surface of ice cores with an annual average rate of 25 cm the final de icing is associated with an interrelated group of re sedimentation processes and surface features series of sinkholes evolve at the toe of dead ice blocks which initiate retrogressive rotational sliding or backslumping of the ice cored slopes and the formation of distinct edges and fractures in the adjacent basins although backslumping is the dominant process in this phase of re sedimentation structures resulting from this process are rarely recognized in the ice free landscape as ice cores gradually diminish the effect of the latest re sedimentation events will overprint or destroy most existing sedimentary characteristics thus in the ice free landscape structures mainly related to the formation of sinkholes and fractures remain imprinted on the sediment succession generally no inversion of the topography occurs during the final phase of de icing the overall topography recognized in the late phase of the fully ice cored terrain is merely lowered and the amplitude of the relief reduced as de icing progresses the sediment architecture of the ice free landscape is characterized by heterogeneous and often slumped diamict sediments with variable thickness and lateral distribution clast orientation is related to the direction of slopes and boulders are found in isolated groups or in linear arrangements

debris entrainment and transfer in polythermal valley glaciers hambrey mj bennett mr dowdeswell ja et al 1999 debris entrainment and transfer in polythermal valley glaciers journal of glaciology 45 149 69 86 published 1999

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

cold firn and ice of high altitude glaciers in the alps measurements and distribution modelling the thermal regime of high altitude accumulation areas in the swiss alps was systematically investigated on the jungfraufirn bernese alps on the breithornplateau valais alps and on grenzgletscher valais alps in 1991 1992 and 1994 temperatures were measured in a deep hole 120 m deep and in several shallow holes 14 30 m deep whereas the wide neve of the jungfraufirn at 3400 3600 m a s l and the 3800 m high breithorn plateau seems to be predominantly temperate cold firn and ice temperatures were measured throughout on grenzgletscher 3900 4450 m a s l mean firn temperatures on grenzgletscher vary strongly and range between 3 and 14 c a comparison between the measured temperature profiles and a one dimensional heat conduction calculation shows that the release of latent heat by penetrating and refreezing meltwater decisively influences the thermal pattern of the firn pack a multiple linear regression model based on measured firn temperatures from the european alps and the parameters altitude and aspect yields aspect dependent lower boundaries for the occurrence of cold firn ranging between 3400 northerly aspects and 4150 m a s l southerly aspects a total of 120 glaciers with cold firn areas are found when applying the model to glacier inventory data from the european alps

recent high arctic glacial sediment redistribution a process perspective using airborne lidar abstract progressive glacier thinning retreat and mass loss in the high arctic is increasingly exposing forefield sediments to processes of mobilisation and redistribution in this paper we quantify forefield sediment redistribution at midtre lovenbreen svalbard using repeat light detection and ranging lidar surveys conducted in 2003 and 2005 in combination with field based observations average surface lowering of the forefield over the observation period identified from lidar surveys is 0 05 ma 1 and two primary areas of sediment reworking are identified active fluvial incision of proglacial streams by 2 m and lateral moraine downwasting of similar magnitude multivariate analysis of fluvial and climatological field data indicates that observed forefield sediment mobilisation is driven primarily by discharge forcing but with contributions from thermoerosive processes and stochastic autogenic sediment supply during the period of observation disparity between sediment loss in forefield fluvial systems as calculated from lidar data 3000 4000 103 kg and monitoring of fluvial sediment load 1600 3500 103 kg suggests the likely presence of significant quantities of buried ice beneath a thick debris mantle as evidenced by field observations relatively uniform lowering of the moraine crest identified from our repeat lidar surveys indicates thermoerosion of an ice core however simple debris layer thickness modelling indicates an increase in variation of debris layer thickness at lower elevations providing support for the assertion that moraine disintegration is driven by complex combinations of both thermal and mechanical processes this study demonstrates the viability of using lidar in conjunction with field monitoring to better understand sedimentary deglaciation dynamics and processes and also highlights the significance of forefield areas in controlling the sediment yield from deglaciating catchments

landscape evolution in martian mid latitude regions insights from analogous periglacial landforms in svalbard periglacial landforms on spitsbergen svalbard norway are morphologically similar to landforms on mars that are probably related to the past and or present existence of ice at or near the surface many of these landforms such as gullies debris flow fans polygonal terrain fractured mounds and rock glacier like features are observed in close spatial proximity in mid latitude craters on mars on svalbard analogous landforms occur in strikingly similar proximity which makes them useful study cases to infer the spatial and chronological evolution of martian coldclimate surface processes the analysis of the morphological inventory of analogous landforms on svalbard and mars allows the processes operating on mars to be constrained different qualitative scenarios of landscape evolution on mars help to better understand the action of periglacial processes on mars in the recent past

a comparison of the styles of deformation associated with two recent push moraines south van keulenfjorden svalbard in this paper two push moraine systems associated with two small subpolar glaciers finsterwalderbreen and penckbreen were investigated this study showed that at these glaciers the push moraines were formed in association with surges which produced a different style of moraine depending on the rheology of the deformed material and the glacial history the moraines are similar in that they are formed by folded outwash sediments and contain little till however the forms of these moraines are very different the penckbreen moraine is composed of a lower shallow marine sand silt and clay and an upper fluvial sand and gravel deformation at this site led to the formation of large anticlines in the silts and clays with disharmonic smaller folds and thrusts in the upper gravels above a detachment surface between the fine grained and overlying coarse grained lithologies this deformation decreases towards the foreland with marine and fluvial sediments responding differently because of their different rheological properties this moraine was formed during one surge event which occured during the early 19th century in contrast the finsterwalderbreen moraine is composed of outwash sand and gravel and was formed as the result of a series of surge events these advances all reached a similar limit and occurred at regular intervals 1997 john wiley sons ltd

controlled moraines origins characteristics and palaeoglaciological implications abstract controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de icing and possess clear linearity due to the inheritance of the former pattern of debris rich folia in the parent ice linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt out as a result moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris rich ice was concentrated in frozen toe zones recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that a controlled moraine development can be ascribed to a specific process e g englacial thrusting or supercooling and b controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts e g ancient polythermal or supercooled snouts these assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris rich ice thickening mechanisms are seen to produce the same geomorphic features polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier permafrost interface end moraines lie on a process form continuum constrained by basal thermal regime the morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores but the final deposits landforms tend to consist of discontinuous transverse ridges with intervening hummocks preserving only a weak impression of the former englacial structure these are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice walled lake plains and lying down flow of streamlined landforms produced by warm based ice a variety of debris entrainment mechanisms can produce the same geomorphic signature spatial and temporal variability in process form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin

current transition from glacial to periglacial processes in the dolomites south eastern alps abstract a close relationship between glacial and periglacial landforms is frequently observed in alpine environments where a transition from glacial to periglacial processes often took place after the end of the little ice age lia understanding the origin of these landforms is challenging and assessing the current spatial domain of glacial and periglacial processes may be a difficult task in high relief areas where thick and widespread debris cover often characterize rapidly decaying glaciers here we present a comprehensive study of a composite landform located in the dolomites south eastern alps combining geomorphological geophysical and topographic surveys with ground surface temperature measurements results indicate that a debris covered glacier persists in the upper part rather large compared to the lia extent but currently inactive and rapidly losing mass an active rock glacier exists in the lower part surrounded by discontinuous permafrost a frozen body about 10 m thick was detected in the rock glacier and geomorphological evidence suggests that this ice mass is completely detached from the debris covered glacier our findings suggest that the lower part of the composite landform is probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions periglacial processes are therefore replacing glacial processes which dominated in this site during the lia

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

reactivation of temporarily stabilized ice cored moraines in front of polythermal glaciers gravitational mass movements as the most important geomorphological agents for the redistribution of sediments a case study from ebbabreen and ragnarbreen svalbard abstract ice cored moraine complexes are prominent landforms characteristic of many polythermal glacial landsystems on svalbard usually marking their maximum little ice age extent despite being often stable over a period ranging from several years to 50 60 years the abundance of dead ice makes them potentially unstable in the future this study aims to 1 recognize the different processes that contribute to ice cored moraine degradation 2 document the spatial distribution of mass wasting sites within ice cored moraine complexes of ebbabreen and ragnarbreen svalbard 3 investigate the relationship between the distribution of mass movement sites and the topographic properties of the landscape 4 develop a model of mass wasting mechanism in a proglacial area we performed field based geomorphological mapping combined with the interpretation of aerial photographs 1960 1990 2009 high resolution satellite imagery 2013 uav based images 2014 terrestrial photographs 2011 2014 hillshade models and digital elevation models in 2013 frontal and lateral ice cored landforms occupied 3 33 km2 of the forelands of ebbabreen and ragnarbreen the total area with an unstable ice cored moraine condition was 0 57 km2 127 sites debris falls slides rolls and flows were the most important processes contributing to the reworking of glacigenic sediments and altering of their properties four different morphological site types were identified 1 near vertical ice cliffs covered with debris transformed mainly by dead ice backwasting as well as debris falls and slides 2 steep debris slopes with exposed ice cores dominated by debris slides 3 gentle sediment mantled slopes transformed by debris flows and 4 non active debris mantled areas transformed by dead ice downwasting alone the spatial and temporal activation of moraines reworking was for the most part related to local geomorphic conditions e g slope gradient occurrence of streams and meltwater channels gravitational mass movements were responsible for the redistribution of debris within the moraine complex whereas fluvial transport by meltwater exported sediments outside the little ice age moraines

preservation of landforms under ice sheets and ice caps abstract this article addresses the question of whether or not distinct glacial and non glacial landforms can survive beneath ice sheets and ice caps with little or no morphological alteration a review of recent work documents the existence of pre last stadial landforms and landscapes in areas covered by the fennoscandian and laurentide ice sheets a substantial number of independent works indicate that landforms such as eskers drainage channels and boulder fields have escaped destruction despite complete ice overriding during several tens of millenia full preservation of former ground surfaces or delicate landforms probably is linked to areas where the ice sheet base was continuously frozen to its bed larger robust landforms such as large drumlins appear to have been preserved even under wet based conditions in glaciated areas patches preserved under dry cold based conditions provide important windows towards the past showing landscapes that were destroyed in surrounding areas affected by wet based and eroding ice some consequences for the research fields of non glacial geomorphology archaeology and botany include the possibility of subglacial museums and refugia a time space model describes geomorphological access to information from older events in glaciated areas

influence of glaciation on mechanisms of mineral weathering in two high arctic catchments in order to investigate the effect of glaciation on mineral weathering the stream water chemistry and the bacterial community composition were analysed in two catchments containing nominally identical sedimentary formations but which differed in the extent of glaciation the stream waters were analysed for major ions 34s 18oso4 and 18oh2o and associated stream sediments were analysed by 16s rrna gene tagged sequencing sulphate comprised 72 86 and 35 45 of the summer anion budget in meq in the unglaciated and glaciated catchments respectively this indicates that sulfuric acid generated from pyrite weathering is a significant weathering agent in both catchments based on the relative proportions of cations sulphate and bicarbonate the stream water chemistry of the unglaciated catchment was found to be consistent with a sulphide oxidation coupled to silicate dissolution weathering process whereas in the glaciated catchment both carbonates and silicates weathered via both sulfuric and carbonic acids stable isotope measurements of sulphate together with inferences of metabolic processes catalysed by resident microbial communities revealed that the pyrite oxidation reaction differed between the two catchments no 34s fractionation relative to pyrite was observed in the unglaciated catchment and this was interpreted to reflect pyrite oxidation under oxic conditions in contrast 34s and 18oso4 values were positively correlated in the glaciated catchment and were positively offset from pyrite this was interpreted to reflect pyrite oxidation under anoxic conditions with loss of s intermediates this study suggests that glaciation may alter stream water chemistry and the mechanism of pyrite oxidation through an interplay of biological physical and chemical factors

reaction softening by dissolution precipitation creep in a retrograde greenschist facies ductile shear zone new hampshire usa we describe strain localization by a mixed process of reaction and microstructural softening in a lower greenschist facies ductile fault zone that transposes and replaces middle to upper amphibolite facies fabrics and mineral assemblages in the host littleton schist near claremont new hampshire here na poor muscovite and chlorite progressively replace first staurolite then garnet and finally biotite porphyroblasts as the core of the fault zone in approached across the transect higher grade fabric forming na rich muscovite is also progressively replaced by fabric forming na poor muscovite the mineralogy of the new phyllonitic fault rock produced is dominated by na poor muscovite and chlorite together with late albite porphyroblasts the replacement of the amphibolite facies porphyroblasts by muscovite and chlorite is pseudomorphic in some samples and shows that the chemical metastability of the porphyroblasts is sufficient to drive replacement in contrast element mapping shows that fabric forming na rich muscovite is selectively replaced at high strain microstructural sites indicating that strain energy played an important role in activating the dissolution of the compositionally metastable muscovite the replacement of strong high grade porphyroblasts by weaker na poor muscovite and chlorite constitutes reaction softening the crystallization of parallel and contiguous mica in the retrograde foliation at the expense of the earlier and locally crenulated na rich muscovite defined foliation destroys not only the metastable high grade mineralogy but also its stronger geometry this process constitutes both reaction and microstructural softening the deformation mechanism here was thus one of dissolution precipitation creep activated at considerably lower stresses than might be predicted in quartzo feldspathic rocks at the same lower greenschist facies conditions this article is protected by copyright all rights reserved

discriminating glacier thermal and dynamic regimes in the sedimentary record abstract this paper provides a description and evaluation of the sedimentary facies and environments associated with a range of glacier thermal and dynamic regimes with additional consideration given to the tectonic context new and previously published data are evaluated together and are presented from modern terrestrial and marine glacial sedimentary environments in order to identify a set of criteria that can be used to discriminate between different glacier thermal regimes and dynamic styles in the sedimentary record sedimentological data are presented from a total of 28 glaciers in 11 geographical areas that represent a wide range of contemporary thermal dynamic and topographic regimes in the context of landsystems representatives from terrestrial environments include temperate glaciers in the european alps patagonia new zealand the cordillera blanca peru cold glaciers in the dry valleys of antarctica and the antarctic peninsula region and polythermal valley glaciers in svalbard northern sweden the yukon and the khumbu himal nepal the glaciomarine environment is illustrated by data from cold and polythermal glacier margins on the east antarctic continental shelf and from a polythermal tidewater glacier in svalbard along with general observations from temperate glaciers in alaska these data show that temperate glacial systems particularly in high relief areas are dominated by rockfall and avalanche processes although sediments are largely reworked by glaciofluvial processes debris in polythermal glaciers is both thermally and topographically influenced in areas of moderate relief debris is mainly of basal glacial origin and the resulting facies association is dominated by diamicton in high relief areas such as the himalaya the debris load in polythermal glaciers is dominated by rockfall and avalanche inputs resulting in extensive accumulations of sandy boulder gravel cold glaciers are dominated by basal debris entrainment but sediments are little modified from the source materials which are typically sandy boulder gravel from older till and sand from glaciofluvial glaciolacustrine and aeolian sources similar facies associations but with different facies geometry and thickness occur in equivalent glaciomarine settings application of these concepts can aid the interpretation of glacier thermal regime and hence palaeoclimate in quaternary and ancient glacial systems

subglacial sediment distribution from constrained seismic inversion using multi software examples from midtdalsbreen norway fast ice flow is associated with the deformation of subglacial sediment seismic shear velocities vs increase with the rigidity of material and hence can be used to distinguish soft sediment from hard bedrock substrates depth profiles of vs can be obtained from inversions of rayleigh wave dispersion curves from passive or active sources but these can be highly ambiguous and lack depth sensitivity our novel bayesian transdimensional algorithm multi circumvents these issues by adding independent depth constraints to the inversion also allowing comprehensive uncertainty analysis we apply multi to the inversion of a rayleigh wave dataset acquired using active source multichannel analysis of surface waves techniques to characterise sediment distribution beneath the frontal margin of midtdalsbreen an outlet of norway s hardangerjokulen ice cap ice thickness 0 20 m is constrained using co located gpr data outputs from multi suggest that partly frozen sediment vs 500 1000 m s 1 overlying bedrock vs 2000 2500 m s 1 is present in patches with a thickness of 4 m although this approaches the resolvable limit of our rayleigh wave frequencies 14 100 hz uncertainties immediately beneath the glacier bed are 280 m s 1 implying that multi cannot only distinguish bedrock and sediment substrates but does so with an accuracy sufficient for resolving variations in sediment properties

de icing progression of ice cored moraines in a humid subpolar climate kotlujokull iceland modes and rates of de icing ice cored moraines under humid subpolar conditions have been determ ined for two dead ice fields of different age representing a mature and a final stage of collapse in the kotlujokull terminus region south iceland the melting processes considered are backwasting defined as the lateral retreat of near vertical ice walls or steep ice cored slopes and downwasting defined as the thinning of the ice core by melting along the top and bottom surfaces in the mature stage of collapse where there is less than 1 m of sediment cover major faces of ice exposed for rapid melting are ordinarily significant and long lived due to intense precipitation in this fully ice cored terrain the predominating processes are backwasting of exposed ice walls and downwasting by bottom melt each contributing to the annual surface lowering of about 0 5 m or 35 the total annual surface lowering melt rate due to all processes averages 1 4 m in those parts of the fully ice cored dead ice field

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

glacier change from the early little ice age to 2005 in the torngat mountains northern labrador canada abstract the glaciers of the torngat mountains of northern labrador are the southernmost of the canadian arctic and the easternmost of continental north america currently 195 small mountain glaciers cover an area in excess of 24 km2 confined mostly to small cirques and upland depressions using a combination of field and remote sensing methods this study reconstructs and dates the areal extent of torngat glaciers at their neoglacial maximums enabling the first assessment of regional glacier change over the past several centuries mapped glacier paleomargins n 165 are compared to current 2005 glaciers and ice masses showing a 52 5 reduction in glacier area with at least 11 former glaciers altogether disappearing glacier change is spatially homogenous and independent of most geographic and topographic factors however glacier elevation and glacier size mitigated total change previously established lichen growth stations were revisited and growth rates recalculated based on 30 year long records enabling the construction of locally derived low and high altitude lichen growth curves using growth rates and in situ lichen measurements the retreat from maximum neoglacial moraine extents are suggested to have occurred between a d 1581 and 1673 these findings indicate a similar magnitude of post lia retreat to mountain glaciers elsewhere yet a much earlier timing 200 years of retreat than other glaciers in the eastern canadian arctic though no definitive answer explaining this discrepancy is presented evidence suggests that regional climate dynamics and the importance of solar radiation for torngat glaciers may play an important role in local glacierization

very low inheritance in cosmogenic surface exposure ages of glacial deposits a field experiment from two norwegian glacier forelands terrestrial cosmogenic nuclide dating has been widely used to estimate the surface exposure age of bedrock and boulder surfaces associated with deglaciation and holocene glacier variations but the

the internal structure of rock glaciers and recently deglaciated slopes as revealed by geoelectrical tomography insights on permafrost and recent glacial evolution in the central and western alps italy france abstract ground ice of permafrost origin and sedimentary ice of glacial origin can coexist in locations where rock glaciers and glaciers interacted as well as in glacigenic sediments abandoned by a retreating glacier and subsequently exposed again to atmospheric cooling some of these geomorphological settings in the central foscagno rock glacier and western alps marinet and schiantala rock glaciers schiantala debris covered glacier maledia glacier were explored by means of geoelectrical tomographies the aim was that of inferring the presence of ice and cryologically interpreting electrical stratigraphies in order to test whether or not the internal structure of these landforms can be used for the reconstruction of recent permafrost and glacier evolution geomorphological data assisted these reconstructions and available borehole stratigraphies were used to calibrate the resistivities along with the ice debris mixture massive ice has also been found as lenses both at the apex and the front of the studied rock glaciers these lenses of sedimentary origin are thought to be transferred from a glacier snout to sectors of rock glacier and eventually embedded into the permafrost creep the scarcity of frozen debris in the mid upper part of the rock glaciers as revealed by low resistivity values can be due to the disruptive effect of the over riding glacier over the permafrost the near surface sedimentary ice masses detected along the slopes of the studied glacial cirques are interpreted as or debris covered terminations of the glaciers still visible upward or as fragments of it detached by the main bodies these ice masses are locally associated to medium high resistive sediments consistent with permafrost occurrence this indicates that the non glacial environment established during the deglaciation allowed the onset of frozen sediments formation overall the results indicate that internal structure of rock glaciers and recent deglaciated slopes can store the different climate related episodes occurred in a specific area such as those linked to the shifting between glacial to criotic condition and vice versa

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