deducing the thermal structure in the tongue of gornergletscher switzerland from radar surveys and borehole measurements we present the thermal distribution in the confluence area of gorner and grenzgletscher valais switzerland the area was mapped by ice penetrating radar at 1 5 and 40 mhz the higher frequency data reveal a thick surface layer of low backscatter in the center of the grenzgletscher branch based on datasets of borehole temperature measurements and flow velocity we interpret this as a thick layer of cold ice advected from the accumulation region of grenzgletscher along seven profiles the base of the low backscatter zone can be found at a maximum depths between approxi mately 100 and 200 m laterally the layer extends some 400 m 1 3 of the width of the grenz gletscher branch the lower boundary of the low backscatter zone is systematically higher than the cold temperate transition surface found in the boreholes this discrepancy is attributed to the direct sensitivity of radar backscatter to liquid water inclusions rather than to the temperature distributions as observed in boreholes we present the current state of the cold layer and discuss its influence on other glacier characteristics

on the temperature distribution of glaciers in china les mesures de temperature des differents types de glaciers en chine sont presentees la temperature de la base de la couche active etant comparee a la temperature atmospherique moyenne

cold surface layer thinning on storglaciaren sweden observed by repeated ground penetrating radar surveys 1 a characteristic feature of ground penetrating radar gpr surveys on polythermal glaciers is an internal reflection presumably caused by the cold temperate transition surface cts hence providing a possible tool for mapping thermal structure with high accuracy comparison of detailed temperature measurements in bore holes and gpr profiles at 345 mhz and 800 mhz center frequencies on storglaciaren sweden show that the cts can be detected and mapped with an accuracy of about 1 m at both frequencies a comparison between comprehensive gpr surveys of the cold surface layer separated by 12 years 1989 2001 shows a substantial and complex thinning of the cold layer an overall decrease of 8 3 m 22 of average thickness of the cts depth is much larger than uncertainties in cts depth determinations the stability of the cold surface layer depends on the net ice ablation at the surface and the downward migration of cts there is no evidence of substantial increased net ablation between the survey dates that could explain the observed thinning however small increase in average winter air temperature a limiting factor for the temperature gradient through the cold surface layer may provide a partial explanation the weaker temperature gradient reduces the transport of latent heat from the cts thus slowing down its downward migration

estimating the risk of glacier cavity collapse during artificial drainage the case of tete rousse glacier 1 during the summer of 2010 the presence of a pressurized water filled subglacial cavity of at least 50 000 m3 was detected within the tete rousse glacier french alps artificial drainage was started to avoid an uncontrolled rupture of the ice dam but was interrupted soon after to evaluate the capacity of the cavity roof to bear itself the risk was that the release of pressure within the cavity during the artificial drainage would precipitate the collapse of the cavity roof and potentially flush out the remaining water flooding the valley below an unprecedented modeling effort was deployed to answer the question of the cavity roof stability we set up a model of the glacier with its water cavity solved the three dimensional full stokes problem predicted the upper surface and cavity surface displacements for various drainage scenarios and quantified the risk of the cavity failure during artificial drainage we found that the maximum tensile stress in the cavity roof was below the rupture value indicating a low risk of collapse a post drainage survey of the glacier surface displacements has confirmed the accuracy of the model prediction this practical application demonstrates that ice flow models have reached sufficient maturity to become operational and assist policy makers when faced with glaciological hazards thus opening new perspectives in risk management of glacier hazards in high mountain regions

links between short term velocity variations and the subglacial hydrology of a predominantly cold polythermal glacier the surface velocity of a predominantly cold polythermal glacier john evans glacier ellesmere island canada varies significantly on both seasonal and shorter time scales seasonal variations reflect the penetration of supraglacial water to the glacier bed through significant thicknesses of cold ice shorter term events are associated with periods of rapidly increasing water inputs to the subglacial drainage system earlyseason short term events immediately follow the establishment of a drainage connection between glacier surface and glacier bed and coincide with the onset of subglacial outflow at the terminus a mid season short term event occurred as surface melting resumed following cold weather and may have been facilitated by partial closure of subglacial channels during this cold period there is a close association between the timing and spatial distribution of horizontal and vertical velocity anomalies the temporal pattern of surface water input to the glacier and the formation seasonal evolution and distribution of subglacial drainage pathways these factors presumably control the occurrence of highwater pressure events and water storage at the glacier bed the observed coupling between surface water inputs and glacier velocity may allow predominantly cold polythermal glaciers to respond rapidly to climate induced changes in surface melting

an automatic approach to delineate the cold temperate transition surface with ground penetrating radar on polythermal glaciers ground penetrating radar has been widely used to map the thermal structure of polythermal glaciers hitherto the cold temperate transition surface cts in radargrams has been identified by a labour intensive and subjective manual picking method we introduce a new automatic approach for picking the cts that uses the difference in signal power exhibited by the cold and temperate ice layers we compare our automatically computed cts depths with manual picks our results show very good agreement between the two methods in most areas r 2 0 7 rmses computed at each trace in two way travel time from three test sites range from 14 to 19 ns 2 4 3 2 m the proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the cts in some areas high power originating from non water sources is misinterpreted by the automatic picking method as temperate ice

hazardous processes and events from glacier and permafrost areas lessons from the chilean and argentinean andes glacier and permafrost hazards such as glacial lake outburst floods and rock ice avalanches cause significant socio economic damages worldwide and these processes may increase in frequency and magnitude if the atmospheric temperature rises in the extratropical andes nearly 200 human deaths were linked to these processes during the twentieth century we analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio economic damages in this region in historic time including glacial lake outburst floods ice and rock ice avalanches and lahars to unravel their causes and geomorphological impacts in the extratropical andes at least 15 ice dammed lakes and 16 moraine dammed lakes have failed since the eighteenth century causing dozens of floods some floods rank amongst the largest events ever recorded 5000 106 m3 and 229 106 m3 respectively outburst flood frequency has increased in the last three decades partially as a consequence of long term decades to centuries climatic changes glaciers shrinkage and lake growth short term days to weeks meteorological conditions i e intense and or prolonged rainfall and high temperature that increased meltwater production have also triggered outburst floods and mass movements enormous mass failures of glaciers and permafrost 10 106 m3 have impacted lakes glaciers and snow covered valleys initiating chain reactions that have ultimately resulted in lake tsunamis and far reaching 50 km flows the eruption of ice covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 106 m3 despite the importance of these events basic information about their occurrence e g date causes and geomorphological impact which is well established in other mountain ranges is absent in the extratropical andes a better knowledge of the processes involved can help to forecast and mitigate these events copyright 2014 john wiley sons ltd

the influence of ground ice distribution on geomorphic dynamics since the little ice age in proglacial areas of two cirque glacier systems holocene glaciers have contributed to an abundance of unstable sediments in mountainous environments in permafrost environments these sediments can contain ground ice and are subject to rapid geomorphic activity and evolution under condition of a warming climate to understand the influence of ground ice distribution on this activity since the little ice age lia we have investigated the pierre ronde and rognes proglacial areas two cirque glacier systems located in the periglacial belt of the mont blanc massif for the first time electrical resistivity tomography temperature data loggers and differential global positioning systems dgps are combined with historical documents and glaciological data analysis to produce a complete study of evolution in time and space of these small landsystems since the lia this approach allows to explain spatial heterogeneity of current internal structure and dynamics the studied sites are a complex assemblage of debris covered glacier ice rich frozen debris and unfrozen debris ground ice distribution is related to former glacier thermal regime isolating effect of debris cover water supply to specific zones and topography in relation with this internal structure present dynamics are dominated by rapid ice melt in the debriscovered upper slopes slow creep processes in marginal glacigenic rock glaciers and weak superficial reworking in deglaciated moraines since the lia geomorphic activity is mainly spatially restricted within the proglacial areas sediment exportation has occurred in a limited part of the former rognes glacier and through water pocket outburst flood and debris flows in pierre ronde both sites contributed little sediment supply to the downslope geomorphic system rather by episodic events than by constant supply in that way during holocene and even in a paraglacial context as the recent deglaciation proglacial areas of cirque glaciers act mostly as sediment sinks when active geomorphic processes are unable to evacuate sediment downslope especially because of the slope angle weakness

mathematical modeling and numerical simulation of polythermal glaciers 1 a mathematical model for polythermal glaciers and ice sheets is presented the enthalpy balance equation is solved in cold and temperate ice together using an enthalpy gradient method to obtain a relationship between enthalpy temperature and water content we apply a brine pocket parameterization scheme known from sea ice modeling the proposed enthalpy formulation offers two advantages 1 the discontinuity at the cold temperate transition surface is avoided and 2 no treatment of the transition as an internal free boundary is required fourier s law and fick type diffusion are assumed for sensible heat flux in cold ice and latent heat flux in temperate ice respectively the method is tested on storglaciaren northern sweden numerical simulations are carried out with a commercial finite element code a sensitivity study reveals a wide range of applicability and defines the limits of the method realistic temperature and moisture fields are obtained over a large range of parameters

twenty years of cold surface layer thinning at storglaciaren sub arctic sweden 1989 2009 this paper presents the changes in the thermal structure of the polythermal glacier storglaciaren northern sweden over the 20 year period 1989 2009 derived by comparing maps of the depth of the englacial transition between cold ice permanently frozen and temperate ice which contains water inclusions the maps are based on interpreted ice penetrating radar surveys from 1989 2001 and 2009 complex thinning of the cold layer first identified between 1989 and 2001 is still ongoing a volume calculation shows that storglaciaren has lost one third of its cold surface layer volume in 20 years with a mean thinning rate of 0 80 0 24 m a 1 we suggest that the thinning of the cold layer at storglaciaren is connected to the climatic warming experienced by sub arctic scandinavia since the 1980s and we argue that repeated ice penetrating radar surveys over the ablation area of polythermal glaciers offer a useful proxy for evaluating glacier responses to changes in climate

thermal tracking of meltwater retention in greenland s accumulation area 1 poorly understood processes controlling retention of meltwater in snow and firn have important implications for greenland ice sheet s mass balance and flow dynamics here we present results from a 3 year 2007 2009 field campaign studying firn thermal profiles and density structure along an 85 km transect of the percolation zone of west greenland we installed one or two thermistor strings at 14 study sites each string having 32 sensors spaced between 0 and 10 m depth data from our network of over 500 sensors were collected at 15 60 min intervals for 1 2 years thereby recording the thermal signature of meltwater infiltration and refreezing during annual melt cycles we document three types of heating of firn related to different mechanisms of meltwater motion and freezing including heterogeneous breakthrough events wetting front advance and year round heating from freezing of residual deep pore water vertically infiltrating meltwater commonly penetrates through cold firn accumulated over decades even where ice layers are present at the previous summer surface and where ice layer thickness exceeds several decimeters the offset between the mean annual air temperature and the 10 m firn temperature reveals the elevation dependency of meltwater retention along our transect the firn is 10 c warmer than the mean annual air temperature at the region where meltwater runoff initiates during 2007 2009 runoff was limited to elevations lower than 1500 m with no sharp runoff limit rather the ratio of retention to runoff transitioned from all retention to all runoff across a 20 km wide zone

very high elevation mont blanc glaciated areas not affected by the 20th century climate change 1 this paper analyses the impact of climate change over the last 100 years on high elevation glaciated areas of the mont blanc range comprising ice fields covering the top of the mont blanc 4808 m and dome du gouter 4300 m areas surface ablation is negligible for these high elevation areas and the surface mass balance is mainly controlled by snow accumulation at dome du gouter ice fluxes have been calculated through two transversal sections by two independent methods in order to assess long term surface accumulation a comparison between these results and recent accumulation observations together with the strong relationship between valley precipitation and snow accumulation suggests that surface accumulation rates did not change significantly over the entire 20th century moreover the small ice thickness changes less than 3 m on the average observed at mont blanc and dome du gouter between 1905 and 2005 clearly reveal that these high elevation glaciated areas have not been significantly affected by climate change over the last 100 years

increase of 10 m ice temperature climate warming or glacier thinning in 1972 and 1995 shallow ice temperatures were measured at identical locations and depths on polythermal mccall glacier brooks range alaska u s a mean annual ice temperatures at 10 m depth t 10 have systematically increased by 1 k for the ablation area 1400 1900 m while closer to the firn area where meltwater percolation and refreezing play a role they remained approximately unchanged interpreting these findings in terms of climate change requires careful consideration of the observed thinning of the glacier which causes lowering of the surface through an existing vertical temperature gradient such temperature gradients can be particularly large in the ablation areas of polythermal glaciers on mccall glacier they are on the order of 0 2 k m 1 we also study the evolution of a 75 m deep temperature profile measured at one location in 1972 using a one dimensional heat diffusion model we find that this profile was in approximate equilibrium with the mean surface temperature extrapolated from the 1972 data using the observed rate of surface lowering and measured rates of vertical advection we find that both the measured temperature change and the vertical temperature gradient at 10 m depth can be reproduced only if the mean annual surface temperature on mccall glacier has increased by 1 1 0 3 k between 1972 and 1995 this result is consistent with the observed trend toward more negative mass balances on the glacier in the 1990s

a cut and closure origin for englacial conduits in uncrevassed regions of polythermal glaciers on uncrevassed regions of polythermal glaciers englacial conduits can form by incision of supraglacial stream channels followed by roof closure the origin and evolution of examples in longyearbreen svalbard and khumbu glacier nepal were determined by speleological survey the development of perennial incised channels requires that incision is significantly faster than glacier surface ablation and thus will be favoured by high meltwater discharges in combination with cool climatic conditions or thick debris cover incised canyons can become blocked by drifted winter snow refrozen meltwater ice rafting from non local sources allochthonous breccias and roof collapses autochthonous breccias conduit closure can also occur in response to ice creep particularly at depth following isolation from the surface englacial conduits continue to evolve by vadose incision down to local base level in the case of longyearbreen incision allowed the channel to reach the glacier bed but on khumbu glacier deep incision is prevented because an effectively impermeable terminal moraine provides a high base level for the glacier drainage system during our period of observations deeper parts of the longyearbreen conduit became blocked by a combination of ice accumulation and creep causing the stream course to be re routed to higher levels on that glacier incision blockage and upward re routing are cyclic we conclude that cut and closure is the dominant mechanism of englacial conduit formation on uncrevassed regions of polythermal glaciers

spatio temporal changes in glacier wide mass balance quantified by optical remote sensing on 30 glaciers in the french alps for the period 1983 2014 remote sensing is a powerful method to reconstruct annual mass balance series over past decades by exploiting archives of available images as well as to study glaciers in inaccessible regions we present the application of a methodological framework based only on optical satellite images to retrieve glacier wide annual mass balances for 30 glaciers in the french alps the glacier wide annual mass balance for the period 1983 2014 was reconstructed by combining changes in glacier volumes computed from remote sensing derived dems with annual measurements of the snow line altitude on satellite images data from direct observations on two of the glaciers confirmed the accuracy of the annual mass balances quantified by remote sensing with an average difference of 0 3 m w e within the uncertainty range of the methods our results confirm the significant increase in mass loss since the early 2000s with a difference 1 m w e a 1 between the periods 1983 2002 and 2003 14 the region wide mass balance for the french alps over the period 1979 2011 was 0 66 0 27 m w e a 1 close to that of the european alps we also show that changes in glacier surface area or length are not representative of changes in mass balance at the scale of a few decades

three dimensional distribution and evolution of permafrost temperatures in idealized high mountain topography 1 permafrost degradation is regarded as a crucial factor influencing the stability of steep rockwalls in alpine areas discernment of zones of fast temperature changes requires knowledge about the temperature distribution and evolution at and below the surface of steep rock in complex high mountain topography strong lateral heat fluxes result from topography and variable surface temperatures and profoundly influence the subsurface thermal field to investigate such three dimensional effects numerical experimentation was conducted using typical idealized geometries of high mountain topography such as ridges peaks or spurs the approach combines a surface energy balance model with a three dimensional ground heat conduction scheme to investigate belowground temperature distribution and permafrost occurrence in high mountain topography time dependent simulations are based on scenario data gained from regional climate models results indicate complex three dimensional patterns of temperature distribution and heat flow density below mountainous topography for equilibrium conditions which are additionally perturbed by transient effects permafrost occurs at many locations where temperatures at the surface do not indicate it e g on the south face of ridges or below the edges of a peak the modeling tools applied have potential for a number of studies in high mountains addressing questions related to permafrost distribution and evolution at depth in real topographies for instance the reanalysis of temperature related instabilities

the influence of snow cover thickness on the thermal regime of tete rousse glacier mont blanc range 3200 m a s l consequences for outburst flood hazards and glacier response to climate change 1 tete rousse glacier french alps was responsible for an outburst flood in 1892 that devastated the village of st gervais le fayet close to chamonix causing 175 fatalities changes in the hydrothermal configuration of the glacier are suspected to be the cause of this catastrophic outburst flood in 2010 geophysical surveys of this glacier revealed a subglacial lake that was subsequently drained artificially the processes controlling the thermal regime of the glacier have been investigated on the basis of measurements and snow firn cover and heat flow models using meteorological data covering the last 200 years temperature measurements show a polythermal structure with subglacial water trapped by the cold lowest part of the glacier 2 c the modeling approach shows that the polythermal structure is due to temporal changes in the depth of the snow firn cover at the glacier surface paradoxically periods with negative mass balances associated with warmer air temperature tend to cool the glacier whereas years with colder temperatures associated with positive mass balances tend to increase the glacier temperature by increasing the firnpack depth and extent the thermal effect of the subglacial lake is evaluated and shows that the lake was formed around 1980 according to future climate scenarios modeling shows that the glacier may cool again in the future this study provides insights into the thermal processes responsible for water storage inside a small almost static glacier which can lead to catastrophic outburst floods such as the 1892 event or potentially dangerous situations as in 2010

a potassic volcanic front in western mexico the lamprophyric and related lavas of san sebastian the superposition of two tectonic regimes rifting and subduction in western mexico has led to the development of a lamprophyric volcanic front 70 km closer to the middle america trench than is the main axis of andesitic volcanism the san sebastian cindercone field represents the northernmost extent of lamprophyric activity in western mexico and lies 40 km trenchward of volcan ceboruco a historically active andesitic stratovolcano the predominant country rocks are cretaceous silicic ash flows although marine sedimentary rocks emplaced between 45 and 115 ma also occur minette absarokite and kersantite lavas were erupted between 0 48 and 0 26 ma in the san sebastian field in close association with flows of basaltic andesite and hornblende andesite there is a gradual transition observed between the two intermediate lava types basaltic andesite and kersantite as plagioclase is suppressed and hornblende and phlogopite are stabilized in melts of intermediate composition this transition reflects the increasing influence of water during crystallization and documents a wide range of hydrous conditions examination of the primary lamprophyric lava types absarokite and minette reveals a remarkable range in their oxidation states if these lavas reflect their mantle source conditions then the redox state of western mexico9s sub arc mantle spans the interval between the ni nio and magnetite hematite buffers a variation in fo 2 of five log units the oxidation and hydrous enrichment of mexico9s sub arc mantle probably formed in response to subduction the eruption of lamprophyric lavas in front of the andesitic suite of the main axis however may have depended upon rifting 1 to trigger melting of the modified mantle and 2 to provide an easy passage to the surface through crustal thinning and block faulting

climate warming revealed by englacial temperatures at col du dome 4250 m mont blanc area 1 temperatures were measured in two deep boreholes drilled at the same location in the ice at col du dome 4250 m in 1994 and 2005 providing clear evidence of atmospheric warming the 1994 temperature profile was already far from steady state conditions results from a heat transfer model reveal that the englacial temperature increase cannot be explained solely by atmospheric temperature rise the latent heat produced by the refreezing of surface meltwater below the surface also contributes to the englacial temperature increase although surface melting is normally very low at this altitude this contribution became significant after 1980 for temperatures at the top of the borehole simulations for different climatic scenarios show that glaciated areas located between 3500 and 4250 m could become temperate in the future this warming could have a major impact on the stability of hanging glaciers frozen to their beds if the melting point is reached

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

spatial and temporal variations in surface velocity and basal drag across the tongue of the polythermal glacier midre lovenbreen svalbard we present results of a detailed investigation of surface motion across the tongue of a polythermal glacier midre lovenbreen svalbard during the 1999 summer surface velocities in the warm based upper tongue increased during periods of enhanced surface melting and rainfall events and force balance analysis indicates that these velocity variations were locally forced probably by fluctuations in subglacial water pressure surface speed ups were also observed on the cold based lower tongue which acted as a sticky spot through which there was minimal subglacial drainage for most of the summer but these were largely non locally forced by longitudinal coupling to the faster moving ice up glacier on one occasion however a large rapid input of surface water to the glacier reduced the basal drag beneath the cold based lower tongue presumably due to hydraulic jacking this resulted in locally forced enhanced surface velocities across the entire tongue accompanied by a breaching of the lower tongue and an outburst of subglacially stored water

evidence towards a thermal lag in the response of karsaglaciaren northern sweden to climate change recent topographical and ground penetrating radar gpr surveys of karsaglaciaren which is a small 1 km 2 and thin 56 m mountain glacier in arctic sweden show that there are small areas of temperate ice in the lowermost part of the glacier this is curious because we would expect such a small and thin glacier to have a fully cold ablation zone specifically with our analyses of present glacier geometry and thickness and of the prevailing climate we are unable to explain the presence of temperate ice within the snout of karsaglaciaren using prevailing models of glacier thermal structure this leads us to suggest that the presence of temperate ice within karsaglaciaren is a remnant of a previous polythermal state that existed when the glacier was larger and thicker karsaglaciaren is thus out of synch with current geometry and climate and is exhibiting a thermal lag we propose that with time karsaglaciaren s ablation zone and perhaps the entire glacier may well become fully cold as the temperate zone shrinks further we anticipate that such a thermal lag is likely to be present within other arctic glaciers a thermal lag and an evolution to a fully cold thermal state have significant implications for the dynamic behaviour of small arctic glaciers and for meltwater production from them

detection of a subglacial lake in glacier de tete rousse mont blanc area france the processes that form intraglacial lakes are poorly understood because of the difficulty in detecting and assessing such hidden lakes extensive geophysical surveys were performed between 2007 and 2010 in order to reassess the risk of an outburst flood from glacier de tete rousse where outburst flooding from an intraglacial lake caused 175 fatalities in 1892 our geophysical survey combined ground penetrating radar measurements and nuclear magnetic resonance imaging we found a subglacial water filled reservoir with a volume of 55 000 m 3 artesian outpourings occurred when the subglacial cavity was reached by two borehole drillings indicating that the hydrostatic water pressure exceeded the ice pressure at the bottom of the cavity on the basis of these geophysical and glaciological findings we warned the public authorities in july 2010 of the risk facing the 3000 inhabitants downstream of the glacier the subglacial reservoir was drained artificially this example demonstrates how geophysical surveys can be used to detect this type of hazard when it is suspected in particular when no hydraulic outlet from the snout exists numerous ice temperature measurements have shown that the tongue of this glacier is cold based this thermal regime could explain the accumulation of water in this glacier

a 3 d thermal regime model suitable for cold accumulation zones of polythermal mountain glaciers analysis of the thermal and mechanical response of high altitude glaciers to climate change is crucial to assess future glacier hazards associated with thermal regime changes this paper presents a new fully thermo mechanically coupled transient thermal regime model including enthalpy transport firn densification full stokes porous flow free surface evolution strain heating surface meltwater percolation and refreezing the model is forced by daily air temperature data and can therefore be used to perform prognostic simulations for different future climate scenarios the set of equations is solved using the finite element ice sheet ice flow model elmer ice this model is applied to the col du dome glacier mont blanc area 4250 m a s l france where a comprehensive data set is available the results show that the model is capable of reproducing observed density and velocity fields as well as borehole temperature evolution the strong spatial variability of englacial temperature change observed at col du dome is well reproduced this spatial variability is mainly a result of the variability of the slope aspect of the glacier surface and snow accumulation results support the use of this model to study the influence of climate change on cold accumulation zones in particular to estimate where and under what conditions glaciers will become temperate in the future

using remote sensing data to determine equilibrium line altitude and mass balance time series validation on three french glaciers 1994 2002 alpine glaciers are very sensitive to climate fluctuations and their mass balance can be used as an indicator of regional scale climate change here we present a method to calculate glacier mass balance using remote sensing data snowline measurements from remotely sensed images recorded at the end of the hydrological year provide an effective proxy of the equilibrium line mass balance can be deduced from the equilibrium line altitude ela variations three well documented glaciers in the french alps where the mass balance is measured at ground level with a stake network were selected to assess the accuracy of the method over the 1994 2002 period eight mass balance cycles results obtained by ground measurements and remote sensing are compared and show excellent correlation r 2 0 89 both for the ela and for the mass balance indicating that the remote sensing method can be applied to glaciers where no ground data exist on the scale of a mountain range or a given climatic area the main differences can be attributed to discrepancies between the dates of image acquisition and field measurements cloud cover and recent snowfalls constitute the main restrictions of the image based method

atmospheric warming at a high elevation tropical site revealed by englacial temperatures at illimani bolivia 6340 m above sea level 16 s 67 w in june 1999 a deep 138 7 m ice core was extracted from the summit glacier of illimani bolivia 6340 m above sea level 16 39 s 67 47 w and an englacial temperature profile was measured in the borehole using on site and regional meteorological data as well as ice core stratigraphy past surface temperatures were reconstructed with a heat flow model the englacial temperature measurements exhibit a profile that is far from a steady state reflecting an increasing atmospheric temperature over several years and nonstationary climatic conditions englacial temperature interpretation using air temperature data borehole temperature inversion and melting rate quantification based on ice core density shows two warming phases from 1900 to 1960 0 5 0 3 k starting approximately in 1920 1930 and from 1985 to 1999 0 6 0 2 k corresponding to a mean atmospheric temperature rise of 1 1 0 2 k over the 20th century according to various climate change scenarios the future evolution of englacial temperatures was simulated to estimate when and under what conditions this high elevation site on the illimani summit glacier could become temperate in the future results show that this glacier might remain cold for more than 90 years in the case of a 2 k rise over the 21st century but could become temperate in the first 20 m depth between 2050 and 2060 if warming reaches 5 k

surface mass balance of glaciers in the french alps distributed modeling and sensitivity to climate change a new physically based distributed surface mass balance model is presented for alpine glaciers based on the crocus prognostic snow model it resolves both the temporal 1 hour time step and spatial 200 m grid step variability of the energy and mass balance of glaciers mass balance reconstructions for the period 1981 2004 are produced using meteorological reconstruction from the safran meteorological model for glacier de saint sorlin and glacier d argentiere french alps both glaciers lost mass at an accelerated rate in the last 23 years the spatial distribution of precipitation within the model grid is adjusted using field mass balance measurements this is the only correction made to the safran meteorological input to the glacier model which also includes surface atmospheric temperature moisture wind and all components of downward radiation independent data from satellite imagery and geodetic measurements are used for model validation with this model glacier sensitivity to climate change can be separately evaluated with respect to a full range of meteorological parameters whereas simpler models such as degree day models only account for temperature and precipitation we provide results for both mass balance and equilibrium line altitude ela using a generic alpine glacier the sensitivity of the ela to air temperature alone is found to be 125 m c 1 or 160 m c 1 if concurrent stefan boltzmann longwave radiation change is taken into account

origin of the outburst flood from glacier de tete rousse in 1892 mont blanc area france extensive field measurements and historical data have been used to re analyse the cause of the outburst flood from glacier de tete rousse that devastated the village of saint gervais le fayet french alps in 1892 causing 175 fatalities the origin of this disaster was the rupture of an intraglacial cavity in glacier de tete rousse that released 200 000 m 3 of water and ice all previous studies have concluded that the intraglacial cavity was formed from a crevasse that was filled and enlarged by meltwater the re analysis presented here suggests that the reservoir of the upper cavity did not originate as an enlarging crevasse the origin of the meltwater reservoir was more likely a supraglacial lake formed before 1878 during a period of negative mass balance following a period of positive mass balance after 1878 the lake was hidden until the outburst flood of 1892 this means that such hazards may be detected by checking regularly for the formation of a lake on the surface of the glacier before it is hidden

a numerical model to simulate snow cover stratigraphy for operational avalanche forecasting laws of snow metamorphism have been introduced in a numerical model which simulates the evolution of temperature density and liquid water profiles of snow cover as a function of weather conditions to establish these laws the authors have summarized previous studies on temperature gradient and on wet snow metamorphism and they have also conducted metamorphism experiments on dry or wet fresh snow samples an original formalism was developed to allow a description of snow with parameters evolving continuously throughout time the introduction of laws of metamorphism has improved significantly the derivation of the settlement of internal layers and of snow covered albedo which depend on the simulated stratigraphy i e the type and size of snow grains of different layers of the snow cover the model was tested during a whole winter season without any re initialization comparison between the simulated characteristics of the snow cover and the observations made in the field are described in detail the model proved itself to be very efficient in simulating accurately the evolution of the snow cover stratigraphy throughout the whole winter season

mechanisms of subglacial cavity filling in glacier de tete rousse french alps the deadliest outburst flood from an englacial cavity occurred on glacier de tete rousse in the mont blanc area french alps in 1892 a subglacial reservoir was discovered in the same glacier in 2010 and drained artificially in 2010 2011 and 2012 to protect the 3000 inhabitants downstream the mechanism leading to the spontaneous refilling of the cavity following these pumping operations has been analyzed for this purpose the subglacial water volume changes between 2010 and 2013 were reconstructed the size of the cavity following the pumping was found to have decreased from 53 500 m 3 in 2010 to 12 750 m 3 in 2013 creep and the partial collapse of the cavity roof explain a large part of the volume loss analysis of cavity filling showed a strong relationship between measured surface melting and the filling rate with a time delay of 4 6 hours a permanent input of 15 m 3 d 1 not depending on surface melt was also found the meltwater and rain from the surface is conveyed to bedrock through crevasses and probably through a permeable layer of rock debris at the glacier bed the drainage pathway permeability was estimated at 0 054 m s 1 from water discharge measurements and dye tracing experiments

effects of el nino southern oscillation on the climate water balance and streamflow of the mississippi river basin abstract climatic and hydrologic observations and results from a terrestrial ecosystem model coupled to a regional scale river routing algorithm are used to document the associations between the el nino southern oscillation enso phenomenon and anomalies in climate surface water balance and river hydrology within the mississippi river basin while no enso signal is found in streamflow at the outlet of the basin in vicksburg mississippi significant anomalies in all water balance components are found in certain regions within the basin enso is mainly associated with positive winter temperature anomalies but hydrologic patterns vary with season location and enso phase el nino precipitation anomalies tend to affect evapotranspiration et in the western half of the basin and runoff in the eastern half la nina events are associated with et anomalies in the central portion of the basin and runoff anomalies in the southern and eastern portions of the basin both enso phases are associated with decreas

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

a multicomponent coupled model of glacier hydrology 2 application to trapridge glacier yukon canada 1 a new glaciohydraulic model is tailored to trapridge glacier yukon canada where long term measurements of subglacial water pressure provide parameter constraints and a platform for model evaluation using digital elevation models and meteorological data as input we investigate hydrology on diurnal and seasonal timescales quantitative comparisons of simulated and observed pressure records allow us to select a reference model objectively from which we gain first insights into the gross spatial characteristics of the drainage system equilibrium simulations highlight target areas for water storage and potential sticky spots both of which have established relevance to glacier dynamics seasonal simulations capture the key signatures of spring and autumn transitions and corroborate our understanding of the processes involved successfully modeled features of the spring transition include increased hydraulic coupling between the surface and bed with time temporary augmentation of subglacial storage and rapid subglacial transitions from a hydraulically unconnected to connected state autumn transitions are characterized by deterioration of the basal drainage network drawdown of subglacial storage reservoirs and heightened sensitivity to precipitation and surface refreezing finally we draw attention to the important role of groundwater transport in cold glacial environments where permafrost can impede drainage from the ice margin

sensitivity of barnes ice cap baffin island canada to climate state and internal dynamics barnes ice cap is a remnant of the laurentide ice sheet which covered much of northern north america during the last glacial maximum barnes reached a quasi equilibrium state 2000 years ago and has remained similar in size since then with a small increase during the little ice age in this study we combine historical observations 1960 1980 with more recent satellite and airborne data 1995 2010 to drive a mass balance model coupled to a transient thermomechanical model with an adaptive mesh geometry the model is used to characterize the current state of the ice cap and to investigate its stability as a function of climate and its own internal dynamics on millennial time scales we show that ice flow is influenced by adjustment of an unsteady shape by gently sloping bedrock and by contrasting viscosities between the pleistocene and holocene ice on shorter time scales barnes is affected by surge activity sensitivity tests reveal that barnes experienced climate conditions which enabled its stability 2000 to 3000 years ago but will disappear under current climate conditions in the next millennium

comparison of thermal structure and evolution between neighboring subarctic glaciers 1 the distribution of cold and temperate ice within glaciers and ice sheets affects processes relevant to englacial and basal hydrology sliding and material rheology thermal regimes in turn are shaped by glacier and ice sheet dynamics as well as environmental setting we investigate the thermal structures of two small 7 km2 neighboring glaciers in the st elias mountains of southwestern yukon canada using ice penetrating radar and borehole temperature measurements our data reveal polythermal regimes in both glaciers that are strongly influenced by accumulation zone meltwater entrapment suggesting a climatic control on thermal structure differences in hypsometry and glacier dynamics nevertheless result in observed variations in the distribution of temperate ice between the two sites experiments with a thermomechanically coupled flow band model corroborate the strong control of meltwater entrapment on thermal structure and suggest a generally minimal role for strain heating an exception to this occurs where localized basal sliding produces lateral shearing and thus enhanced heat generation time dependent model simulations suggest that the future thermal evolution of the two glaciers may differ and therefore simple parameterizations of thermal response based on regional climate may not capture realistic variability between individual glaciers despite these differences both glaciers are ultimately expected to become fully cold prior to disappearing under negative mass balance conditions

an energy and mass model of snow cover suitable for operational avalanche forecasting a numerical model has been developed to simulate energy and mass evolution of snow cover at a given location as a function of meteorological conditions precipitation air temperature humidity wind velocity and incoming short wave and long wave radiation this model named crocus was first tested on a well instrumented field during a whole winter showing its ability to simulate the important phenomena affecting the evolution of the snow layers high temperature gradients wetting compaction and melting freezing cycles a second test was conducted at two locations in the french network used for operational avalanche forecasting though the weather observations are made there only twice daily the snow profiles calculated by the model were very close to those obtained once a week by a pit observation crocus proved itself sufficient to be considered now as a useful objective tool for operational avalanche forecasting

fracture propagation as means of rapidly transferring surface meltwater to the base of glaciers 1 propagation of water filled crevasses through glaciers is investigated based on the linear elastic fracture mechanics approach a crevasse will penetrate to the depth where the stress intensity factor at the crevasse tip equals the fracture toughness of glacier ice a crevasse subjected to inflow of water will continue to propagate downward with the propagation speed controlled primarily by the rate of water injection while the far field tensile stress and fracture toughness determine where crevasses can form once initiated the rate of water driven crevasse propagation is nearly independent of these two parameters thus rapid transfer of surface meltwater to the bed of a cold glacier requires abundant ponding at the surface to initiate and sustain full thickness fracturing before refreezing occurs

factors influencing the basal temperatures of a high arctic polythermal glacier a number of glaciers in the canadian high arctic are composed primarily of cold ice but the ice at or near their beds reaches the pressure melting point pmp in the ablation zone past modelling studies have suggested that the basal temperatures of some of these glaciers reach the pmp where they should not indicating that they are not in thermal equilibrium with present day surface air temperatures to investigate the possible reasons for thermal disequilibria in such glaciers a two dimensional ice temperature model was used to simulate the inferred thermal characteristics of john evans glacier ellesmere island results indicate that while surface refreezing and historical ice thickness changes have had a warming effect upon basal ice temperatures supraglacial meltwater reaching the glacier bed provides the single most critical heat source for explaining the apparent thermal disequilibrium between present day inferred ice bed temperatures and those modelled under present day boundary conditions

radioglaciological studies on hurd peninsula glaciers livingston island antarctica we present the results of several radio echo sounding surveys carried out on johnsons and hurd glaciers livingston island antarctica between the 1999 2000 and 2004 05 austral summer campaigns which included both radar profiling and common midpoint measurements with low 20 25 mhz and high 200 mhz frequency radars the latter have allowed us to estimate the radio wave velocity in ice and firn and the corresponding water contents in temperate ice which vary between 0 and 1 6 depending on the zone maximum ice thickness is 200 m with a mean value of 93 6 2 5 m total ice volume is 0 968 0 026 km 3 for an area of 10 34 0 03 km 2 the subglacial relief of johnsons glacier is quite smooth while that of hurd glacier shows numerous overdeepenings and peaks the radar records suggest that hurd glacier has a polythermal structure contrary to the usual assumption that glaciers in livingston island are temperate this is also supported by other dynamical and geomorphological evidence

water flow through temperate glaciers understanding water movement through a glacier is fundamental to several critical issues in glaci ology including glacier dynamics glacier induced floods and the prediction of runoff from glacierized drainage basins to this end we have synthesized a conceptual model of water movement through a temper ate glacier from the surface to the outlet stream pro cesses that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology where a glacier is covered by a layer of porous perme able firn the accumulation zone the flux of water to the glacier interior varies slowly because the firn tempo rarily stores water and thereby smooths out variations in the supply rate in the firn free ablation zone in con trast the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time water moves from the surface to the bed through an upward branching arborescent net work consisting of both steeply inclined conduits formed by the enlargement of intergranular veins and gently inclined conduits spawned by water flow along the bottoms of near surface fractures crevasses engla cial drainage conduits deliver water to the glacier bed at a limited number of points probably a long distance downglacier of where water enters the glacier englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn their size adjusts so that they are usually full of water and flow is pressurized in contrast water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms flow is otherwise in an open channel configuration the subglacial drainage system typically consists of several elements that are distinct both morphologically and hydrologically an up glacier branching arborescent network of channels in cised into the basal ice conveys water rapidly much of the water flux to the bed probably enters directly into the arborescent channel network which covers only a small fraction of the glacier bed more extensive spatially is a nonarborescent network which commonly includes cav ities gaps between the glacier sole and bed channels incised into the bed and a layer of permeable sediment the nonarborescent network conveys water slowly and is usually poorly connected to the arborescent system the arborescent channel network largely collapses during winter but reforms in the spring as the first flush of meltwater to the bed destabilizes the cavities within the nonarborescent network the volume of water stored by a glacier varies diurnally and seasonally small temper ate alpine glaciers seem to attain a maximum seasonal water storage of 200 mm of water averaged over the area of the glacier bed with daily fluctuations of as much as 20 30 mm the likely storage capacity of subglacial cavities is insufficient to account for estimated stored water volumes so most water storage may actually occur englacially stored water may also be released abruptly and catastrophically in the form of outburst floods

ground penetrating radar and surface nuclear magnetic resonance monitoring of an englacial water filled cavity in the polythermal glacier of tete rousse in polythermal glaciers specific climatic topographic and exposure conditions may lead to the formation of englacial lakes that can produce catastrophic effects downstream in the event of abrupt natural drainage we have determined how a combination of ground penetrating radar gpr and surface nuclear magnetic resonance snmr surveys helped to locate and visualize the evolution of a water filled cavity within the tete rousse glacier french alps we have used gpr results to delineate the roof of the cavity and monitor the cavity deformation caused by artificial drainage because the glacier bed and cavity have complex 3d geometries we needed dense acquisition lines and 3d gpr views to qualitatively identify out of plane reflections this 3d approach made it possible to establish a precise map of the glacier bed topography the accuracy of which was verified against borehole observations then repetitive gpr measurements were used to obtain a quantitative estimate of the vertical deflection of the cavity s roof and changes in crevasse geometry observed in response to the decrease in the water pressure when 47 800 m3 of water was drained by pumping we have used 3d snmr imaging to locate water accumulation zones within the glacier and to estimate the volume of accumulated water the snmr monitoring revealed that in two years the cavity lost approximately 73 of its initial volume with 65 lost after the first drainage knowledge of the water contained in the ice provided a better understanding of gpr images and thus a more reliable interpretation of gpr data however snmr imaging had a much lower resolution in comparison with gpr and consequently gpr allowed a more accurate study of the evolution of cavity geometry caused by consecutive drainage and refilling this study demonstrated the value of combining gpr data with snmr data for the study of polythermal glaciers

the role of hydrologically driven ice fracture in drainage system evolution on an arctic glacier 1 observations from ellesmere island suggest that the connection between surface and subglacial drainage on a predominantly cold glacier is made abruptly by hydrologically driven propagation of fractures from the surface to the bed where ice is 150 m thick water ponded to a depth of 6 9 m within a supraglacial stream system before establishing a permanent bed connection multiple premonitory drainage events preceded the final drainage of ponded water implying that fracturing is necessary but insufficient to establish a permanent link between surface and subglacial drainage refreezing of water that penetrates the first fractures to form may reseal the connection while flow resistance within the subglacial system may delay the onset of continuous through flow a large volume of ponded water is required to enlarge fractures sufficiently by melting to maintain continuous drainage while feedbacks between subglacial hydrology and ice dynamics may assist in maintaining the connection and initiating subglacial outflow

modelling heat flow in a cold high altitude glacier interpretation of measurements from colle gnifetti swiss alps modelling the heat flow in small cold high altitude glaciers is important for the interpretation of paleoclimatic data from ice cores coupled glacier flow and heat flow models are presented that incorporate the densification heat advection and possible phase transitions at the permafrost boundaries within the bedrock marked bends observed in the temperature profiles from two recent boreholes on colle gnifetti swiss alps are interpreted with the help of a transient heat flow model driven with a temperature history the conclusion is that substantial warming of the mean firn temperature at shallow depths has taken place over the last few decades this has not been observed before in cold firn regions of the alps modelled heat fluxes in the monte rosa massif are strongly influenced by the mountain topography this leads to a spatial variability of the temperature gradient near the glacier base which has been observed in boreholes to the bedrock in order to match the measured temperature profiles in the glacier the vertical heat flux at great depth must be set to an extremely low value it is shown with the help of the transient heat flow model that this is a paleoclimatic effect possibly enhanced by a degrading permafrost base

spatial pattern and stability of the cold surface layer of storglaciaren sweden the mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have to date been poorly investigated and are not fully understood