new insights into ice accumulation at galena creek rock glacier from radar imaging of its internal structure the ice cored galena creek rock glacier wyoming usa has been the subject of a number of studies that sought to determine the origin of its ice we present new observations of the rock glacier s internal structure from ground penetrating radar to constrain ice and debris distribution and accumulation we imaged dipping reflectors in the center of the glacier that are weak and discontinuous in contrast to strong reflectors toward the edge of the cirque beneath large debris avalanche chutes these reflectors form a network of concave up up glacier dipping layers we interpret these as englacial debris bands formed by large debris falls buried by subsequent ice and snow accumulation they are discontinuous where ice outpaces debris accumulation but with sufficient debris accumulation an interleaved pattern of ice and debris layers can form we propose a model in which the ice in these interleaved layers is snowfall preserved by debris facilitated accumulation large debris falls that occur in early spring bury sections of the snowpack which are then preserved through summer and incorporated into the rock glacier body over time this study highlights the importance of sequential accumulation of ice and debris for understanding the dynamics of rock glaciers and debris covered glaciers

the response of black rapids glacier alaska to the denali earthquake rock avalanches 1 we describe the impact of three simultaneous earthquake triggered rock avalanches on the dynamics of black rapids glacier alaska by using spaceborne radar imagery and numerical modeling we determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ers 1 ers 2 tandem radarsat 1 and alos palsar synthetic aperture radar data ice velocity above the debris covered area of the glacier increased up to 14 after the earthquake but then decreased 20 by 2005 within the area of the debris sheets mean glacier surface velocity increased 44 within 2 years of the landslides at the downglacier end of the lowest landslide where strong differential ablation produced a steep ice cliff velocities increased by 109 over the same period by 2007 ice velocity throughout the debris area had become more uniform consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris without further analysis we cannot prove that these changes resulted from the landslides because black rapids glacier displays large seasonal and interannual variations in velocity however a full stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide induced mass balance changes

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

rock glaciers and mountain hydrology a review abstract in mountainous regions climate change threatens cryospheric water resources and understanding all components of the hydrological cycle is necessary for effective water resource management rock glaciers are climatically more resilient than glaciers and contain potentially hydrologically valuable ice volumes and yet have received less attention even though rock glacier hydrological importance may increase under future climate warming in synthesising data from a range of global studies we provide the first comprehensive evaluation of the hydrological role played by rock glaciers we evaluate hydrological significance over a range of temporal and spatial scales alongside the complex multiple hydrological processes with which rock glaciers can interact diurnally seasonally annually decadally and both at local and regional extents we report that although no global extent complete inventory for rock glaciers exists currently recent research efforts have greatly elaborated spatial coverage using these research papers we synthesise information on rock glacier spatial distribution morphometric characteristics surface and subsurface features ice storage and hydrological flow dynamics water chemistry and future resilience from which we provide the first comprehensive evaluation of their hydrological contribution we identify and discuss long intermediate and short term timescales for rock glacier storage allowing a more balanced assessment of the contrasting perspectives regarding the relative significance of rock glacier derived hydrological contributions compared to other water sources we show that further empirical observations are required to gain a deeper hydrological understanding of rock glaciers in terms of i their genesis and geomorphological dynamics ii total ice water volume iii water discharge and iv water quality lastly we hypothesise that at decadal and longer timescales under future climate warming degradation of ice within rock glaciers may represent an increasing hydrological contribution to downstream regions and thus increased hydrological significance while rock glacier water stores persist

a distributed temperature index ice and snowmelt model including potential direct solar radiation hourly melt and discharge of storglaciaren a small glacier in sweden were computed for two melt seasons applying temperature index methods to a 30 m resolution grid for the melt component the classical degree day method yielded a good simulation of the seasonal patient of discharge but the pronounced melt induced daily discharge cycles were not captured modelled degree day factors calculated for every hour and each gridcell from melt obtained from a distributed energy balance model varied substantially both diurnally and spatially a new distributed temperature index model is suggested attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography this is accomplished by including a radiation index in terms of potential clear sky direct solar radiation and thus without the need for other data besides air temperature this approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates the incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

is that a relict rock glacier abstract the distribution of rock glaciers is often used to investigate the occurrence of permafrost in mountain areas and to understand their climate and paleoclimate evolution this requires the creation of regional and global inventories capable of discriminating active and relict landforms in order to forecast the presence or absence of ice in the ground in this paper geomorphological geophysical and microclimatic surveys are performed on a rock glacier of the carnic alps eastern european alps in the classification currently used for implementing regional inventories of permafrost evidence in the alps this rock glacier would be defined as relict however the geophysical climatological and geomorphological results indicate that internal ice is widespread in large portions of the rock glacier these are generally interpreted as ice in pore spaces and local ice lenses probably without layers of massive ice moreover the occurrence of ice during the maximum thawing season at depths

slow dynamics in debris covered and rock glaciers in hofsdalur trollaskagi peninsula northern iceland abstract the results of previous work on the dynamics of the debris covered and rock glaciers in trollaskagi are contradictory to improve our knowledge of these dynamics and determine the origin and evolution of these landforms we analyzed two case studies located in the hofsdalur valley the hofsjokull debris covered glacier and the jullogil rock glacier using digital photogrammetry combined with gis techniques our most accurate results were obtained for the period 1980 1994 as follows for the hofsjokull debris covered glacier a mean block displacement velocity of 0 22 m yr 1 a block elevation difference of 0 36 m and a horizontal displacement of linear ridges of 0 21 m yr 1 for the jullogil rock glacier a mean block displacement velocity of 0 15 m yr 1 a block elevation difference of 0 63 m and a horizontal displacement of linear ridges of 0 16 m yr 1 the limits of these glaciers remained stable for 70 years from 1946 to 2017 all our data support the fact that these landforms are stable and having lost their ice accumulation sources their dynamics are fundamentally related to subsidence processes therefore they are relict landforms whose origin seems to be related to paraglacial processes after rapid deglaciation of the valleys and their stagnated ice is preserved as it is above the permafrost level

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

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

far flung moraines exploring the feedback of glacial erosion on the evolution of glacier length abstract over many glacial cycles the glacial erosion of alpine valleys can be sufficient to reduce the length of glaciers in the most recent cycles we document field cases illustrative of this erosional feedback and model the long term evolution of glacier lengths analytically and numerically the general feature we target is a moraine deposited well beyond the last glacial maximum lgm limit which we refer to as a far flung moraine firstly we assemble published observations to illustrate that far flung moraines are documented around the world the observations suggest that the downvalley distance to such far flung moraines can exceed the distance to lgm moraines by up to twofold secondly we address the problem analytically making several simplifying assumptions to demonstrate that glacier length scales linearly with erosion depth finally we employ a numerical model to test the analytical solution this 1d depth integrated flowline model includes i a depth averaged longitudinal coupling stress approximation ii prescribed winter and summer surface mass balance profiles iii evolving ice temperature calculated via the conventional heat equation and iv glacier sliding velocity parameterized as a function of basal ice temperature and spatially and temporally variable prescribed flotation fraction the simulated alpine landscape is modified through the competing processes of glacier erosion which is dependent on glacier sliding velocity and prescribed bedrock erodibility and prescribed uplift rate the climate controlling surface mass balance is prescribed by time series of air temperature and snowfall approximated by the sum of two sinusoidal cycles the recurrence statistics of these prescribed climate drivers closely match those of the marine isotopic record hence the prescribed climate drivers faithfully mimic observed long term climate drivers consistent with earlier landscape evolution studies we find that the primary effect of repeated glaciations is to flatten a valley floor and steepen its headwall effectively cutting a longitudinal notch in a fluvial valley profile analytical and numerical model results also demonstrate that far flung moraines are an inevitable consequence of repeated glaciations glaciers in tectonically inactive regions can sufficiently erode their valleys so that the earliest glaciations leave moraines many kilometers down valley from moraines left by the latest glaciations despite similar climates this suggests that a different landscape rather than a different climate is capable of explaining the early glacier extents as a corollary the long term drift toward reduced glacier length favors the survival of early moraines in the face of later glacial advances finally rock uplift can defeat this erosional feedback while rock subsidence enhances the feedback

did rock avalanche deposits modulate the late holocene advance of tiedemann glacier southern coast mountains british columbia canada abstract most glaciers in western north america with reliable age control achieved their maximum holocene extents during final advances of the little ice age tiedemann glacier a large alpine glacier in western canada is an enigma because the glacier constructed lateral moraines that are up to 90 m higher and extend 1 8 km farther downvalley than those constructed during the little ice age our data show that the activity of the glacier is more complex than originally documented and that the glacier advanced many times during the past six thousand years surface exposure dating and radiocarbon ages of stumps beneath till demonstrate that the glacier achieved its maximum holocene extent at about 2 7 ka we hypothesize that one or more rock avalanches delivered surface debris to the glacier and caused the 2 7 ka glacier advance to be much larger than can be explained by climate forcing to test our hypothesis we developed and used a surface debris advection routine coupled to an ice dynamics model our results show that even a moderately sized rock avalanche 10 10 6 m 3 delivered to the top of the ablation zone could cause the glacier to thicken and advance far beyond its little ice age limit

glacial melt under a porous debris layer in this paper we undertake a quantitative analysis of the dynamic process by which ice underneath a dry porous debris layer melts we show that the incorporation of debris layer airflow into a theoretical model of glacial melting can capture the empirically observed features of the so called ostrem curve a plot of the melt rate as a function of debris depth specifically we show that the turning point in the ostrem curve can be caused by two distinct mechanisms the increase in the proportion of ice that is debris covered and or a reduction in the evaporative heat flux as the debris layer thickens this second effect causes an increased melt rate because the reduction in latent energy used for evaporation increases the amount of energy available for melting our model provides an explicit prediction for the melt rate and the temperature distribution within the debris layer and provides insight into the relative importance of the two effects responsible for the maximum in the ostrem curve we use the data of nicholson and benn 2006 to show that our model is consistent with existing empirical measurements

an inventory driven rock glacier status model intact vs relict for south tyrol eastern italian alps ice presence in rock glaciers is a topic that is likely to gain importance in the future due to the expected decrease in water supply from glaciers and the increase of mass movements originating in periglacial areas this makes it important to have at ones disposal inventories with complete information on the state of rock glaciers this study presents a method to overcome incomplete information on the status of rock glaciers i e intact vs relict recorded in regional scale inventories the proposed data driven modelling framework can be used to estimate the likelihood that rock glaciers contain frozen material potential predictor variables related to topography environmental controls or the rock glacier appearance were derived from a digital terrain model dtm satellite data and gathered from existing data sets an initial exploratory data analysis supported the heuristic selection of predictor variables three classification algorithms namely logistic regression glm support vector machine svm and random forest rf were trained on the basis of the available information on the status of rock glaciers within the territory of south tyrol eastern italian alps the resulting classification rules led to assign a binary label intact or relict to 235 unclassified rock glaciers present in the inventory all models were validated quantitatively on spatially independent test samples spatial cross validation and achieved highly satisfactory performance scores hereby the less flexible statistically based classifier glm performed slightly better than the more flexible machine learning algorithms svm and rf spatial permutation based variable importance assessment revealed that elevation and vegetation cover based on ndvi were the most relevant predictors for more than 80 of the unclassified rock glaciers all of the three models agreed on the spatially predicted rock glacier status only for a minor portion 12 3 one model differed from the remaining two

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

numerical modeling of glacial erosion and headwall processes in alpine valleys abstract how rock relief is developed by glacial erosion in alpine landscapes is a key question in understanding the controls on mountain range topography any generation of relief by glaciers at the highest elevations in mountain ranges can affect the distribution of precipitation in alpine landscapes creating feedbacks between glacier mass balance and glacial erosion relief production at high elevation mountain crests is addressed using a numerical model that incorporates glacier dynamics and subglacial erosion as well as relevant hillslope processes blowing snow from a valley bounding plateau and avalanching onto the accumulation zone of the glacier is included in the model furthermore temperature dependent frost cracking is used as a proxy for headwall backwearing the parameterization of subglacial erosion produces about 500 m of erosion over the 400 ka of each numerical simulation in steady and varying climate scenarios valley floors flatten as headwalls increase in height and retreat headward over time headwall slopes increase in simulations in which quarrying is explicitly incorporated rates of quarrying are high near the base of the headwall increasing headwall length and slope as a result of valley floor lowering high rates of subglacial erosion and production of headwall relief also result when elastic flexural uplift occurs in response to mass unloading small overdeepenings form at the base of the headwall in steady climate simulations when the glacier is small at the end of the model run while the final profiles are relatively insensitive to the erosion rule used quarrying is most effective near the head of the glacier whereas rates of abrasion reflect the instantaneous pattern of integrated ice discharge or ice flux in simulations in which cirques are formed the equilibrium line altitude is hundreds of meters above the cirque floor however the time averaged horizontal position of the equilibrium line corresponds well with the downvalley position of the cirques

the effect of topography latitude and lithology on rock glacier distribution in the lemhi range central idaho usa abstract statistical analysis of rock glaciers in the lemhi range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology we inspected 171 alpine valleys in the lemhi range using optical remote sensing techniques digital topographic analysis and field examination in those valleys we identified 48 rock glaciers and examined them for lichen cover evidence of ice presence specific evidence of movement and distinctive morphological features in addition to recording the presence or absence of a rock glacier in each alpine valley existing rock glaciers were classified according to their morphology factors such as topographic shading lithology relief aspect and elevation determine the development and preservation of rock glaciers analysis of these factors in the lemhi range shows that elevation 2600 m a north facing aspect 300 60 and multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly whereas duration of insolation is a logical controlling factor latitude is more enigmatic additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range lithology may affect rock glacier distribution through its effects on hydrology or air ventilation moreover statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence suggesting that protalus lobes play a role in the genesis of rock glaciers in the lemhi range separate analysis of the classification systems shows that each morphologic class inferred to correlate with rock glacier activity is statistically significant and distinguishable from other classes in addition to the effect of insolation statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology

a model of ablation dominated medial moraines and the generation of debris mantled glacier snouts medial moraines form striking dark stripes that widen non linearly steepen laterally and increase in relief down glacier from the equilibrium line coalescence of these low ablation rate features can feed back strongly on the mass balance of a glacier snout ablation dominated medial moraines originate from debris delivered to glacier margins producing a debris rich septum between tributary streams of ice below their confluence emergence of this ice below the equilibrium line delivers debris to the glacier surface which then moves down local slopes of evolving morainal topography a quantitative description of moraine evolution requires specification of the debris concentration field within the glacier treatment of the melt rate dependence on debris thickness and characterization of processes that transport debris once it emerges onto the ice surface debris concentration at glacier tributary junctions scales with the erosion rates and the lengths of the tributary valley walls and inversely with the tributary ice speeds melt rate is damped exponentially by debris with a 10 cm decay scale debris flux across the glacier surface scales with the product of debris thickness and local slope analytical and numerical results show that medial moraines should develop cross glacier profiles with parabolic crests and linear slopes and should widen with age and hence distance down glacier debris should be both thin and uniform over the moraine observed faster than linear growth of moraine widths with distance reflects the increasing ablation rate down glacier increase in medial moraine cover reduces the local average ablation rate allowing the glacier to extend further down valley than meteorology alone would suggest this feedback is especially effective when moraines merge

glacial advance and stagnation caused by rock avalanches abstract new model results show that a glacier advance caused by deposition of a rock avalanche on the ice will be followed by stagnation of the advanced ice lobe producing distributed hummocky deposits quite different from the single moraine ridges typically dated in paleoclimatic reconstructions we obtain these results using a numerical flow line glacier model with superimposed rock debris in particular our results imply that the single moraine ridge known as the waiho loop of the franz josef glacier new zealand is not the result of an advance triggered by a rock avalanche else there would be a widespread hummocky glacial stagnation deposit associated with it

the differing biogeochemical and microbial signatures of glaciers and rock glaciers glaciers and rock glaciers supply water and bioavailable nutrients to headwater mountain lakes and streams across all regions of the american west here we present a comparative study of the metal nutrient and microbial characteristics of glacial and rock glacial influence on headwater ecosystems in three mountain ranges of the contiguous u s the cascade mountains rocky mountains and sierra nevada several meltwater characteristics water temperature conductivity ph metals nutrients complexity of dissolved organic matter dom and bacterial richness and diversity differed significantly between glacier and rock glacier meltwaters while other characteristics ca fe sio2 concentrations reactive nitrogen and microbial processing of dom showed distinct trends between mountain ranges regardless of meltwater source some characteristics were affected both by glacier type and mountain range e g temperature ammonium nh4 and nitrate no3 concentrations and bacterial diversity due to the ubiquity of rock glaciers and the accelerating loss of the low latitude glaciers our results point to the important and changing influence that these frozen features place on headwater ecosystems

the geomorphic significance of rock glaciers estimates of rock glacier debris volumes and headwall recession rates in west greenland to obtain knowledge on rockwall retreat rates at sites with rock glaciers an inventory of about 400 individual rock glacier sites in west greenland was carried out by means of field studies and using aerial photographs and topographic maps a number of sites with ice cored moraines beyond normal glaciers were included in the analysis for comparative purposes the estimated debris volume was compared with the size of the source headwall the result of the inventory suggests that the presence of rock glaciers indicates extraordinary high retreat rates for rock free faces above especially headwalls above glacier derived rock glaciers are exposed to high weathering rates and thereby presumably delimit critical ranges regarding altitude for headwall retreat rates the relation of such a critical altitudinal range to other regional concepts such as glaciation level gl and glacier equilibrium line is discussed from this comments are also made on the relation between various permafrost zones and the typical regional climate within the maximum headwall weathering altitude at sites with active rock glaciers finally the potential importance of this range of maximum weathering for understanding the long term evolution of high relief cold climate landscapes is emphasised

the significance of rock glaciers in the glacial periglacial landscape continuum rock glaciers are distinct landforms whose wide distribution occurrence and significance often go unrecognised they are deposits of poorly sorted angular blocky to tabular debris which are held together by an ice core or a matrix of ice cemented fine clastics rock glaciers have formed in glaciated and non glaciated areas many researchers have suggested that the absence of an ice core or the lack of movement indicates relict or fossil status active and inactive states can be viewed as the end members of a movement continuum movement rates derived from world wide locations as reported in the literature range from less than 1 cmyr 1 to greater than 130cmyr 1 unfortunately lack of observed movement has been equated incorrectly with an inactive status rock glacier movement must be considered from a rheological point of view movement is controlled by the transformation of potential energy to kinetic energy as the system attempts to reach thermal equilibrium or stability whereas a glacier can completely disappear or redevelop reactivation of a rock glacier requires only the re establishment of the conditions responsible for development and maintenance of interstitial ice although it might not be possible to re establish an ice core interstitial areas can definitely be recharged with ice and thus facilitate movement the concept of active versus inactive should be abandoned in favor of the view that a spatial and temporal continuum of form and movement exists

ice ablation and meteorological conditions on the debris covered area of baltoro glacier karakoram pakistan during the recent italian expedition k2 2004 50 years later june july 2004 on baltoro glacier karakoram pakistan glaciological field experiments were carried out on the debris covered area of this high elevation glacier the aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at urdukas 4022 m a s l and at k2 base camp 5033 m a s l in addition temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance r using the air temperature the local mean lapse rate 0 00758 cm 1 and the measured ablation the degree day factors k at different locations on the glacier were calculated the ice ablation rates were related to debris thickness and elevation they are typically on the order of 4 cm d 1 during the observation period however it was found that the surface topography slope aspect has an influence on the total ablation similar to that of the debris thickness thermal resistance of the debris cover and its distribution over the glacier were estimated finally a best guess estimate of the total meltwater production was calculated from available climate data

periglacial weathering and headwall erosion in cirque glacier bergschrunds glaciers produce cirques by scouring their beds and sapping their headwalls but evidence to constrain models of these processes has been elusive we report a suite of environmental measurements from three cirque glacier bergschrunds including the first temperature series recorded at depth throughout most of an annual cycle compared to the ambient air the bergschrunds were colder in summer and warmer in winter freeze thaw cycles were rare and relatively stable subfreezing temperatures persisted from november until may using a model for rock fracturing driven by ice segregation we demonstrate that favorable conditions for fracturing occur not only on the headwall above the glacier but also within the bergschrund where periglacial weathering and glacial transport can act together to drive cirque headwall retreat a small 3 c year round decrease in temperatures to conditions more typical of the pleistocene would likely intensify the weathering process though so far ignored in all glacial landscape evolution models the bergschrund likely plays an essential role in the sculpting of alpine landscapes

10be ages of late pleistocene deglaciation and neoglaciation in the north central brooks range arctic alaska we present a chronology of late pleistocene deglaciation and neoglaciation for two valleys in the north central brooks range alaska using cosmogenic 10be exposure dating the two valleys show evidence of ice retreat from the northern range front before 16 15 ka and into individual cirques by 14 ka there is no evidence for a standstill or re advance during the lateglacial period indicating that a glacier advance during the younger dryas if any was less extensive than during the neoglaciation the maximum glacier expansion during the neoglacial is delimited by moraines in two cirques separated by about 200 km and dated to 4 6 0 5 and 2 7 0 2 cal ka bp both moraine ages agree with previously published lichen inferred ages and confirm that glaciers in the brooks range experienced multiple advances of similar magnitude throughout the late holocene the similar extent of glaciers during the middle holocene and the little ice age may imply that the effect of decreasing summer insolation was surpassed by increasing aridity to limit glacier growth as neoglaciation progressed copyright 2012 john wiley sons ltd

internal structure and composition of a rock glacier in the andes upper choapa valley chile using borehole information and ground penetrating radar this study uses boreholes ground temperature monitoring and ground penetrating radar gpr in order to understand the internal structure and composition of a rock glacier in the upper choapa valley northern chile the rock glacier is a small valley side feature 200 m long and ranging between 3710 and 3780 m a s l two boreholes were drilled down to depths of 20 and 25 m respectively using the diamond drillhole technique an ice rock mixture was encountered in the boreholes with heterogeneous ice content averaging 15 30 data from common midpoint cmp and constant offset co gpr surveys acquired respectively near the boreholes and across the whole rock glacier were processed to highlight the internal stratigraphy and variations in the radar wave velocity the gpr profiles depict a rock glacier constituted of stacked and generally concordant layers with a thickness ranging from 10 m in its upper part to 30 m towards its terminus the cmp analysis highlights radar wave velocities of 0 13 0 16 m ns 1 in the first 20 m of the structure larger vertical and lateral velocity variations are highlighted from co data reflecting the heterogeneous composition of the rock glacier and the likely presence of unfrozen water in the structure given the average air temperature registered at the site 0 58c the near melting point temperature registered in the boreholes over more than a year and the presence of locally high water content inferred from gpr data it is thought that the permafrost in the rock glacier is currently degrading

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

debris thickness patterns on debris covered glaciers abstract many debris covered glaciers have broadly similar debris thickness patterns surface debris thickens and tends to transition from convex to concave up down glacier we explain this pattern using theory analytical and numerical models paired with empirical observations down glacier debris thickening results from the conveyor belt like nature of the glacier surface in the ablation zone debris can typically only be added but not removed and from the inevitable decline in ice surface velocity toward the terminus down glacier thickening of debris leads to the reduction of sub debris melt and debris emergence toward the terminus convex up debris thickness patterns occur near the up glacier end of debris covers where debris emergence dominates ablation controlled concave up debris thickness patterns occur toward glacier termini where declining surface velocities dominate velocity controlled a convex concave debris thickness profile inevitably results from the transition between ablation control and velocity control down glacier debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time by establishing this expected debris thickness pattern the effects of climate change on debris cover can be better identified

tectonic versus chemical weathering controls on the composition of fluvial sands in tropical environments the compositions of fluvial sands collected in mountainous regions along the volcanic front in central america and along the andean front in venezuela and colombia correlate with the tectonic setting of their source terrains the sands derived from the central american volcanic arc are compositionally distinct from those derived from the andean terrains and minor variations in tectonic style can also be discriminated subtle differences in tectonic setting and source rock composition are recognizable only when modification by chemical weathering is slight they are strongest in sands from low order streams draining mountainous areas with modest alluvial plain development sands that have been exposed to weathering for extended periods during alluvial storage are progressively enriched in chemically stable phases with increased weathering sands from continental terrains converge toward a supermature quartz arenite end member and the imprint left by source rock composition and tectonic setting is obscured in intraoceanic terrains a similar but much less pronounced enrichment in stable phases relative to less stable phases is observed similarly overprinting the tectonic signal although detailed tectonic information is easily lost sands derived from intraoceanic terrains are distinguishable from those derived from continental terrains even after long exposure to intense chemical weathering conditions

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

alpine landscape evolution dominated by cirque retreat despite the abundance in alpine terrain of glacially dissected landscapes the magnitude and geometry of glacial erosion can rarely be defined in the eastern kyrgyz range of central asia a widespread unconformity exhumed as a geomorphic surface provides a regional datum with which to calibrate erosion as tectonically driven surface uplift has progressively pushed this surface into the zone of ice accumulation glacial erosion has overprinted the landscape with as little as 500 m of incision into rocks underlying the unconformity distinctive glacial valleys display their deepest incision adjacent to cirque headwalls the expansion of north facing glacial cirques at the expense of south facing valleys has driven the drainage divide southward at rates of as much as two to three times the rate of valley incision glacial erosion rules based on ice flux incompletely explain this dominance of cirque retreat over valley incision local processes that either directly sap cirque headwalls or inhibit erosion down glacier appear to control at least initially alpine landscape evolution

evidence for a landslide origin of new zealand s waiho loop moraine the waiho loop moraine has been interpreted as evidence for younger dryas cooling in southern new zealand but recent dating and climatological studies have questioned this idea a detailed analysis of the sedimentology of the moraine suggests it was formed after a large landslide onto the franz josef glacier triggered a glacial surge independent of climate forcing

rock glaciers and the geomorphological evolution of deglacierizing mountains abstract rock glaciers are an important geomorphic element of glaciated mountain landscapes but our understanding of their distribution and ages controls on their development and their importance in regional mountain hydrology and mountain geomorphic evolution is incomplete in part this incomplete knowledge arises through problems associated with identifying rock glaciers on a morphological basis alone amplified by the multiple ways in which rock glaciers can form in different glacial periglacial and paraglacial settings this study focuses on rock glaciers as a paraglacial mountain landscape element and considers the relationships between rock glaciers and glacial periglacial and paraglacial processes new geomorphic and sedimentary data on different rock glaciers from the khumbu region of nepal are presented these data show that even within a single region rock glaciers may have varied origins and thus likely ages and different climatic and environmental controls we argue that rock glaciers in deglacierizing mountains may have a long residence time in the landscape unlike many other glacially influenced mountain landforms and can undergo significant morphodynamic changes as glaciated landscapes transition into paraglacial landscapes

climate sensitivity and geomorphological response of cirque glaciers from the late glacial to the holocene sierra nevada spain abstract through a detailed geomorphological study including thourough mapping of the geomorphic features as well as 10be cosmic ray exposure cre dating the geomorphological evolution of the mulhacen cirque since the maximum ice extent of the last glacial cycle until nowadays was determined this glacial cirque is shaped on the northern face of the mulhacen peak 3479 m a s l 37 03 12 n 3 18 41 w sierra nevada southern spain it includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle furthermore the sequence of glacial oscillations from this site was compared to that of other cirques of the massif evidencing that i new glaciers formed in these cirques during the younger dryas yd and ii disappeared at 11 7 1 0 ka depending on the altitude orientation and height of the cirque walls the final deglaciation of the cirques generated a diversity of landscapes including a wide range of glacial and periglacial landforms such as polished surfaces sequences of moraines proto rock glaciers or large rock glacier systems no glaciers existed in the sierra nevada during the middle holocene only the cirques whose summits exceed 3300 m are north exposed and whose walls exceed 300 m high i e mulhacen and veleta hosted glaciers during neoglacial phases including the little ice age lia approx 1300 1850 ce during these periods climate oscillations favoured the formation of small glaciers in these cirques which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs the existence of glaciers impeded the formation of permafrost related landforms such as rock glaciers and protalus lobes until the end of the lia when they started to form these results are compared with the deglacial evolution in 55 cirques from iberian mountains as well as from glacial cirques from other mid latitude mountains and subpolar regions the chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns with no significant differences at regional scale for each mountain range the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases

rock glaciers and related periglacial landforms in the sierra nevada ca usa inventory distribution and climatic relationships abstract rock glaciers and related periglacial rock ice features rifs are abundant yet overlooked landforms in the sierra nevada california where they occur in diverse forms we mapped 421 rifs from field surveys and grouped these into six classes based on morphology and location these categories comprise a greater range of frozen ground features than are commonly described in rock glacier surveys mapped features extended from 2225 to 3932 m modern mean 3333 m occurred mostly on nnw to nne aspects and ranged in apparent age from modern to relict late pleistocene many of the smaller features mapped here are not readily discernible with remote e g air photo observation field surveys remain the best approach for their detection we interpreted the presence of outlet springs basal lakes suspended silt in outlet streams and fringing phreatophytic vegetation in addition to morphologic indications of current rock movement as evidence for interstitial ice either persistent or seasonal the six classes were distinct in their geographic settings and morphologic conditions indicating process level differences to assess modern climate we intersected mapped locations with the 30 arcsec prism climate model discriminant analysis indicated significant differences among the climate means of the classes with the first three canonical vectors describing 94 of the differences among classes mean annual air temperatures maat for modern features ranged from 0 3 to 2 2 c mean precipitation ranged from 1346 to 1513 mm we calculated differences between modern and pleistocene temperatures in two ways one based on elevation differences of modern and relict rifs 662 m and standard lapse rate the other using prism estimates for the first we estimate the difference in maat as 3 9 c range 2 2 to 7 9 c from prism the difference was 3 3 c range 1 0 to 6 1 c in that persistent snowfields and glaciers are retreating in the sierra nevada under warming climates rifs will likely become increasingly important in prolonging water storage during the warm season and providing small but distributed water reserves for biodiversity and runoff their presence and water contributions would benefit by further hydrologic study

features of glacial valley profiles simply explained 1 glacial occupation of alpine valleys results in a distinct signature in the long valley profile including steepening of the profile in the headwaters flattening at lower elevations and a step in the profile at the convergence of headwater tributaries we present analytic results for glacial erosion patterns by making the following assumptions 1 the initial profile is linear 2 the width of the valley is uniform 3 the annual mass balance varies linearly with elevation 4 the glacier at any time is quasi steady 5 the erosion rate is proportional to ice discharge per unit valley width and 6 glacial erosion rates far exceed fluvial erosion rates a steady glacier under these conditions would erode a parabolic divot in the longitudinal valley profile with its maximum depth coinciding with the down valley position of the equilibrium line altitude ela the calculated flattening of the valley floor down valley of the ela and the steepening of it up valley captures the essence of the glacial signature when a reasonable probability distribution of elas is allowed the predicted erosion peaks at 30 40 of the down valley distance to the glacial limit and the pattern merges smoothly with the steeper fluvial profile downstream of the glacial limit profiles of mass balance that are capped at a maximum value produce shorter glaciers and a slight asymmetry in the expected erosion pattern only when we mimic the tributaries of glacial headwaters by specifying a valley width distribution do we obtain the upper step observed in many valley profiles

subsurface investigation of a rock glacier using ground penetrating radar implications for locating stored water on mars 1 the discovery of rock glacier like features on mars suggests the presence of flowing or once flowing ice rock mixtures these landforms which include lobate debris aprons concentric crater fill and lineated valley fill hold significant promise as reservoirs of stored water ice that could be used as fuel sources for human exploration of mars and provide a frozen record of the climatic history of the planet to understand the deformation and distribution of ice within these landforms fundamental descriptions of their internal structure and development are required to this end a ground penetrating radar investigation was initiated using rock glaciers in the san juan mountains of colorado as surrogates for similar martian landforms results obtained from one of these rock glaciers show that the interior of the landform is composed of a layered permafrost matrix of ice sediment and ice lenses that comprise thicker depositional units formed through high magnitude debris falls folds in the uppermost layers correspond to the surface expression of ridges and furrows suggesting that compressive stresses originating in the accumulation zone are transmitted downslope through the rock glacier rock glacier features on mars may also consist of layered permafrost which would suggest a history of development involving seasonal frost accumulation and or water influx from below in terms of water storage within martian analogs consideration must include the possibility that some water ice may be stored in relatively pure form within lenses and vein networks such as observed in the surrogate rock glacier of this study

gpr survey of a lobate rock glacier in yankee boy basin colorado usa abstract the internal structure of a lobate rock glacier located in the san juan mountains of southwest colorado was investigated using ground penetrating radar gpr a 440 m 25 mhz longitudinal profile oriented along the central axis of the rock glacier shows moderate to strongly coherent reflection horizons or layers that can be recognized clearly to a depth of 30 35 m the layers are interpreted as representing ice supersaturated sediments and coarse blocky rockslide debris that are the result of flow perhaps generated by seasonal snow pack covered by episodic debris flows or high magnitude discharges of talus from the cirque headwall profiles collected at 50 mhz indicate that in the upper 20 m thickness of the rock glacier many of these layers are laterally continuous the total depth of penetration 40 m at 25 mhz was sufficient to detect the rock glacier cirque floor contact which is composed of underlying moraine several prominent reflection events that subdivide the profile into broad 10 15 m thick layers represent contacts between major depositional units these units are believed to be individual flow lobes that were initiated at various cirque headwall locations we interpret this rock glacier to be a composite feature that formed by a process involving the development and subsequent overlap of discrete flow lobes that have over ridden older glacial moraine and protalus rampart materials the latter materials have been incorporated into the present flow structure of the rock glacier

constraints on the timing of debris covered and rock glaciers an exploratory case study in the holar area northern iceland abstract eighteen samples for 36cl cosmic ray exposure cre dating were taken from glacially polished bedrocks moraine boulders fossil active rock glaciers and debris covered glaciers in fremri grjotardalur and holadalur cirques in the vi inesdalur hofsdalur and he insdalur valleys close to holar village in the trollaskagi peninsula northern iceland boulder sampling was preceded by a study of the boulder stability with the twofold aim of ensuring that the surfaces to be sampled were stable enough for the reliable application of cre dating and to better understand the relation between the glacier dynamics and exposition history the results show that the glaciers which occupy the valleys in trollaskagi began their retreat around 16 ka later the glaciers advanced again around 11 ka within the cirques and small moraines were formed thereafter these small glaciers retreated and evolved into rock glaciers as debris from paraglacial processes accumulated on the glacier surface the fronts of these rock glaciers stabilized definitively shortly after their formation and became eventually fossil after the melting of their internal ice new rock glaciers and debris covered glaciers formed afterwards which still have internal ice at present although their current dynamics are mostly related to subsidence the stabilization of these rock glaciers and debris covered glaciers is dated to the period between 7 and 3 ka although they may have been reactivated during cold neoglacial periods this research demonstrates the potential interest in applying cre dating methods to debris covered glaciers and rock glaciers to determine their origin evolution and phase of cessation of internal movement until they finally lost their internal ice and became fossil

reconsidering the glacier to rock glacier transformation problem new insights from the central andes of chile abstract the glacier to rock glacier transformation problem is revisited from a previously unseen angle a striking case in the juncal massif located in the upper aconcagua valley chilean central andes is documented there the presenteseracae debris covered glacier has advanced several tens of metres and has developed a rock glacier morphology in its lower part over the last 60 years the conditions for a theoretically valid glacier to rock glacier transformation are discussed and tested permafrost probability in the area of the studied feature is highlighted by regional scale spatial modelling together with on site shallow ground temperature records two different methods are used to estimate the mean surface temperature during the summer of 2014 and the sub debris ice ablation rates are calculated as ranging between 0 05 and 0 19 cm d 1 i e 0 04 and 0 17 m over the summer these low ablation rates are consistent with the development of a coherent surface morphology over the last 60 years furthermore the rates of rock wall retreat required for covering the former glacier at presenteseracae lie within the common 0 1 2 mm y 1 range assuming an average debris thickness and a range of debris covering time intervals the integration of the geomorphological observations with the numerical results confirms that the studied debris covered glacier is evolving into a rock glacier

the sedimentology and geomorphology of rock avalanche deposits on glaciers this article describes and compares the deposits of four large landslides on two glaciers in alaska using field mapping and remote sensing digital image analysis is used to compare the sedimentological characteristics of nearly 200 000 individual surface blocks deposited by three landslides at black rapids glacier in 2002 the debris sheets of one of the three landslides on black rapids glacier and a landslide emplaced on sherman glacier in 1964 are also investigated the three landslides on black rapids glacier have undergone little post depositional modification by glacier flow whereas the sherman glacier landslide has been transported supraglacially up to ca 1k m over the past 46 years the three debris sheets on black rapids glacier have coarse blocky rims at their distal edges and all four debris sheets have longitudinal flowbands characterized by differences in texture and produced by shearing within the moving debris elongated blocks are parallel to flow except at the perimeter of the debris sheets where they are aligned more perpendicular to flow blocks on the sherman glacier debris sheet have been reoriented by glacier flow the matrix shows no systematic differences with depth or distance from the source however it appears to become coarser over a time scale of decades due to weathering

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

a new model of rock glacier dynamics abstract rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer they have also been described as glacigenic in origin in which the main rock glacier body contains glacier ice at depth other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive although all rock glaciers are to some extent polygenic there is no clear simple test that can be used to distinguish between different rock glacier types this study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature the study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls this analysis provides an easily deployed interpretive framework for the origins of rock glaciers

catastrophic landslides glacier behaviour and moraine formation a view from an active plate margin the influence of large bedrock landslides rock avalanches on the behaviour of glaciers is incompletely recognised here we present an example from an active tectonic margin in south island new zealand where large earthquakes leave a significant imprint on glacial records we demonstrate that terminal moraines on the western side of the southern alps record both ordinary i e climate driven and landslide initiated glacial advances following consideration of the processes involved in rock avalanche initiated moraine construction we suggest ways of determining the nature of the advance that built the terminal moraine the implications of these observations are important in breaking the conventional linkage of individual terminal moraines with climate forcing

evidence for long lasting landform surface instability on hummocky moraines in the pamir mountains tajikistan from 10be surface exposure dating abstract surface exposure dating is a new but already widely used tool in geomorphological studies aiming e g at the establishment of glacial chronologies sometimes however results from samples taken from one and the same moraine scatter widely and thus interpretation turns out to be difficult here we assess sample specific effects topographic shielding sample geometry and erosion on 17 surface exposure ages obtained by analysis of in situ produced cosmogenic 10be in boulders from moraines in the pamir mountains tajikistan a wide scatter of exposure ages is observed only for hummocky moraines 45 to 10 ka bp but not for distinct lateral moraines 20 and 60 ka bp respectively it is hypothesized that inheritance prior exposure and moraine degradation may be responsible for the wide scatter of exposure ages on the hummocky moraines to proof this hypothesis a data set of 72 boulders from the pamir mountains is used we conclude that most likely hummocky moraines experienced long lasting landform surface instability probably due to buried glacier ice that is protected from melting several ten thousand years by a thick debris cover

fast deformation of perennially frozen debris in a warm rock glacier in the swiss alps an effect of liquid water 1 surface movement internal deformation and temperature were monitored over 5 years on buz north rock glacier a small rock glacier located at the lower limit of the permafrost belt in the swiss alps the permafrost in the rock glacier mainly consists of pebbles and cobbles filled with interstitial ice two inclinometers installed at 4 and 5 m depths showed fast deformation with large seasonal and interannual variations while the permafrost temperatures remained almost at the melting point the movement of the inclinometers coincided with changes in the surface velocities the deformation rapidly accelerated during snowmelt periods whereas it gradually decelerated below a dry snow cover in winter the frozen debris was more deformable than typical glacier ice at the melting point these phenomena suggest that the frozen debris is permeable to snowmelt water the fast deformation should result from significant annual relocation of debris particles which probably creates a network of air voids in the frozen debris that eventually allows water infiltration the meltwater infiltration accelerates the deformation by reducing effective stress resulting in the reduced strength of the frozen debris the refreezing of the pore water which depends on the cooling intensity in winter decelerates the deformation the combination of these processes controls the temporal variations in the deformation

thermal and hydrologic attributes of rock glaciers and periglacial talus landforms sierra nevada california usa abstract to explore thermal regimes and hydrologic capacity of rock glaciers and related periglacial talus landforms mini thermochrons were deployed in and around potentially ice embedded features of the sierra nevada results from pilot studies at 13 rock glaciers and 7 taluses indicate that outlet springs from these landforms generally do not desiccate but persist year round as ice frozen in winter and flowing water in the warm season temperatures of water liquid and ice in rock glacier outlet springs had an annual mean of 0 2 c and mean of 0 6 c during the warm season with very low diurnal fluctuation these and other attributes suggest the existence of internal ice and or permafrost supplying the springs air temperatures of rock glacier matrices 1 m below the surface versus surface air corroborate the periglacial nature of internal environments annual air temperatures of matrices were below freezing mean 0 8 c compared to surface air especially during the warm season matrix air temperatures were significantly colder and fluctuated less talus landforms followed a similar pattern although water and matrix air temperatures were warmer and contrasts with surface air were not as strong as for rock glaciers for rock glaciers and talus slopes matrix air temperatures showed resistance buffering to changes in external air temperatures unique geomorphic conditions of rock glaciers and periglacial taluses in the sierra nevada appear to maintain cool buffered thermal regimes at least partly decoupled from external air springs support persistent wetlands and lakes at their snouts retaining water in otherwise semi arid high cirques and contribute as hydrologic reserves and critical habitat for alpine biota daily and seasonal lags and buffering effects suggest that ice within these landforms might resist surface warming on the longer term which could make these landforms increasingly important as regional climates change

debris covered glaciers in the sierra nevada california and their implications for snowline reconstructions abstract ice walled melt ponds on the surfaces of active valley floor rock glaciers and matthes little ice age moraines in the southern sierra nevada indicate that most of these landforms consist of glacier ice under thin ca 1 10 m but continuous covers of rock fall generated debris these debris blankets effectively insulate the underlying ice and greatly reduce rates of ablation relative to that of uncovered ice such insulation explains the observations that ice cored rock glaciers in the sierra actually debris covered glaciers are apparently less sensitive to climatic warming and commonly advance to lower altitudes than do adjacent bare ice glaciers accumulation area ratios and toe to headwall altitude ratios used to estimate equilibrium line altitudes elas of former glaciers may therefore yield incorrect results for cirque glaciers subject to abundant rockfall inadvertent lumping of deposits from former debris covered and bare ice glaciers partially explains an apparently anomalous regional ela gradient reported for the pre matthes recess peak neoglacial advance distinguishing such deposits may be important to studies that rely on paleo ela estimates moreover matthes and recess peak ela gradients along the crest evidently depend strongly on local orographic effects rather than latitudinal climatic trends indicating that simple linear projections and regional climatic interpretations of ela gradients of small glaciers may be unreliable

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

late pleistocene and holocene glaciation of the fish lake valley northeastern alaska range alaska we reconstructed a chronology of glaciation spanning from the late pleistocene through the late holocene for fish lake valley in the north eastern alaska range using 10 be surface exposure dating and lichenometry after it attained its maximum late wisconsin extent the fish lake valley glacier began to retreat ca 16 5 ka and then experienced a readvance or standstill at 11 6 0 3 ka evidence of the earliest holocene glacial activity in the valley is a moraine immediately in front of little ice age lia moraines and is dated to 3 3 3 0 ka a subsequent advance culminated at ca ad 610 900 and several lia moraine crests date to ad 1290 1640 1860 and 1910 our results indicate that 10 be dating from high elevation sites can be used to help constrain late holocene glacial histories in alaska even when other dating techniques are unavailable close agreement between 10 be and lichenometric ages reveal that 10 be ages on late holocene moraines may