clast shape analysis and clast transport paths in glacial environments a critical review of methods and the role of lithology the reconstruction and tracing of transport paths in glaciated and other environments have a long tradition in the earth sciences we here present a dataset of clast shape samples from a worldwide selection of glaciated mountain environments in order to assess the reliability of this approach overall and the role of lithology on the performance of clast shape measurements in particular our findings demonstrate that the widely used ra c40 co variance approach is applicable to 63 of the 19 catchments investigated while the alternative rwr c40 approach is more widely applicable to 75 of these catchments a systematic assessment of mixing of lithologies at the catchment scale demonstrates that such mixing leads to pronounced overlaps between different control envelopes that had previously been separated thereby removing the discriminatory power of the method mixing of similar lithologies between different catchments shows an even more extreme loss of discriminatory power which strongly suggests that lithology plays a primary role in determining clast shape and that catchment specific processes are superimposed systematic analysis of the dataset also shows that nearly all catchments apart from two can be grouped into two types type i relates to sites in lesser mountain ranges and is characterised by dominantly blocky forms in the subglacial realm highlighting significant reworking processes type ii sites are dominantly in high mountain environments and characterised by a high similarity between subglacial and fluvial control envelopes this indicates that although reworking may be pronounced it is not necessarily effective enough to remove the platy shape that most likely results from extraglacial and supraglacial inputs our study highlights the potential of clast shape analysis as a tool that allows generic processes to be identified between catchments thereby enabling an understanding of debris cascades in glaciated mountain environments we finish with recommendations for ensuring that future clast shape studies are robust reproducible and comparable between different sites

regionally differentiated contribution of mountain glaciers and ice caps to future sea level rise the contribution to sea level rise from mountain glaciers and ice caps has grown over the past decades a projection of their melting during the twenty first century based on temperature and precipitation projections from ten climate models suggests that by 2100 these glaciers will lose about 21 of their total global volume

the climate memory of an arctic polythermal glacier knowledge of glacier equilibrium line altitude ela changes and trends in time is essentialfor future predictions of glacier volumes we present a novel method for determining trends in elachange at mccall glacier alaska usa over the last 50 years based on mapping of the cold temperatetransition surface cts marking the limit between cold and temperate ice of a polythermal glacier latent heat release from percolating meltwater and precipitation keeps the ice column temperate in theaccumulation area a change from accumulation to ablation zone reduces this heat release leadinglocally to glacier ice cooling by mapping the cts along the whole glacier length using radio echosounding and employing a thermodynamic model the timing of the cooling was determined fromwhich past elas were constructed these are in accord with mass balance measurements carried out onmccall glacier since the 1950s we show that with a warming climate mccall glacier tends to cool ina counter intuitive way

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

the chernobyl reference horizon in the greenland ice sheet published reports of the presence of radioactive debris from the chernobyl reactor accident in snow on the greenland ice sheet raised the strong prospect that such debris might constitute a valuable time stratigraphic marker all over the ice sheet large volume snow samples to test this possibility were collected from 7 snowpits as part of a wide ranging regional snow chemistry survey conducted during 1987 and 1988 snow labeled with chernobyl derived radioactivity was detected in all of the pits however the total amount of radioactive debris found at the different locations varied over a 20 fold range the variability in total fallout showed no clear large scale spatial pattern that could be related to the presumed progress of the radioactive plume over greenland suggesting that small scale differences in precipitation pattern and reworking of the snow by wind were predominantly responsible for the patchy preservation of the chernobyl layer on the greenland ice sheet copyright american geophysical union 1989

the signal from the chernobyl accident in high altitude firn areas of the swiss alps in order to investigate the deposition of radioactive fission nuclides in the high altitude snow and firn of the swiss alps after the chernobyl accident core samples from nine mountain peaks were analyzed the observed radiological signal is described together with the characteristics of the snow in which it is embedded total activity is of the same order of magnitude around 10 kbq m 2 as deposition rates measured at lower altitudes and shows a comparable regional distribution a clear altitudinal trend only exists with respect to snow conditions above about 4000 m a s l erosion mlxmg and resedimentation of cold snow by wind could have occurred during or shortly after the deposition whereas at lower altitudes formation and percolation of melt water had already started probably selectively to redistribute the nuclides within temperate firn layers

the search for seismic signatures of movement at the glacier bed in a polythermal valley glacier a passive seismology experiment was conducted across the main overdeepening of storglaciaren in the tarfala valley northern sweden to investigate the spatial and temporal distribution of basal microseismic waveforms in relation to known dynamics of this small polythermal sub arctic glacier the high ablation rate made it difficult to keep geophones buried and well coupled to the glacier during the experiment and reduced the number of days of good quality data collection the characterization of typical and atypical waveforms showed that the dominant waveforms were from near surface events such as crevassing waveforms resembling basal microseismic signals were very rare and seldom observed on more than two seismic stations simultaneously the analysis of waveforms amplitudes and particle motions suggested a near field origin for most events even though basal sliding is known to occur in the overdeepening no convincing examples of basal waveforms were detected suggesting basal microseismic signals are rare or difficult to detect beneath polythermal glaciers like storglaciaren we discuss the reasons for failing to locate basal signals consider the origin of common waveforms and make recommendations for setting up passive seismology experiments on glaciers with high ablation rates

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

timing of rotational motion of apuseni mountains romania paleomagnetic data from tertiary magmatic rocks paleomagnetic results are reported from 8 sites in eocene to oligocene magmatic rocks and 27 sites in middle miocene to upper miocene volcanic rocks of the apuseni mountains following af demagnetization 29 sites were selected for tectonic interpretation these results together with previously published data imply a northward displacement of the area studied between the late cretaceous and oligocene followed by a large clockwise rotation prior to the middle miocene after which no significant movement has occurred these results agree with other data from the carpatho pannonian domain showing a period of great mobility during the early miocene

former dynamic behaviour of a cold based valley glacier on svalbard revealed by basal ice and structural glaciology investigations large numbers of small valley glaciers on svalbard were thicker and more extensive during the little ice age lia demonstrated by prominent ice cored moraines up to several kilometres beyond present day margins the majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds indicating they are likely to have undergone a thermal transition from a polythermal to a cold based regime we present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of tellbreen a small cold based valley glacier in central spitsbergen based on its basal sequence and glaciological structures within the basal sequence the underlying matrix supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer this is overlain by debris poor dispersed facies ice interpreted to have formed through strain induced metamorphism of englacial ice the sequential development of structures includes arcuate fracture traces interpreted as shear planes formed in a compressive transpressive stress regime and fracture traces interpreted as healed extensional crevasses the formation of these sediment ice facies and structures is indicative of dynamic warm based flow most likely during the lia when the glacier was significantly thicker

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

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

glacier surge propagation by thermal evolution at the bed bakaninbreen southern svalbard began a prolonged surge during 1985 in 1986 an internal reflecting horizon on radio echo sounding data was interpreted to show that the position of the surge front coincided with a transition between areas of warm unfrozen and cold frozen bed ground penetrating radar lines run in 1996 and 1998 during early quiescence show that the basal region of the glacier is characterized by a strong reflection interpreted as the top of a thick layer of sediment rich basal ice down glacier of the present surge front features imaged beneath the basal reflection are interpreted as the bottom of the basal ice layer the base of a permafrost layer and local ice lenses this indicates that this region of the bed is cold up glacier of the surge front a scattering zone above the basal reflection is interpreted as warm ice there is no evidence for this warm zone down glacier of the surge front nor do we see basal permafrost up glacier of it thus as in early surge phase the location of the surge front is now at the transition between warm and cold ice at the glacier bed we suggest that the propagation of the front is associated with this basal thermal transition throughout the surge because propagation of the front occurs rapidly and generates only limited heat basal motion during fast flow must have been restricted to a thin layer at the bed and occurred by sliding or deformation localized at the ice bed interface

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

improved accuracy of cross borehole radar velocity models for ice property analysis cross borehole radar xbhr is widely used for the quantification of pore scale liquid water in geologic materials inferred from bulk velocity variations caused by differences in electromagnetic properties between the water and the surrounding material the xbhr can accurately and repeatedly measure variation at depth with sampled material remaining under natural stresses while maintaining good lateral sampling however even small errors in measured radar velocities result in large errors in water content estimates emphasizing the need to quantify and minimize errors we have rigorously assessed the sources of uncertainty in xbhr surveys undertaken in a glaciological setting we have summarized and quantified the three main areas of uncertainty in data collection 1 instrument time drift 2 first break picking and 3 borehole geometry our analysis of field data indicated that contemporary acquisition procedures can produce velocity errors of 3 0 0 0050 m ns equivalent to 0 84 vol water content we have developed several revisions to produce improved data acquisition through enhancement of existing techniques the velocity uncertainties were improved to 1 5 we also found the measurement of borehole diameter during hot water drilling which could hypothetically further reduce the velocity uncertainty to 0 8 equivalent to 0 2 vol water content the need for such precise measurement is clear because an increase in englacial water content from 0 to 0 8 has been proven to triple the strain rate and soften the ice liquid water between ice crystals has also been linked to faster velocities in ice streams and surging events

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

glacial and periglacial floodplain sediments regulate hydrologic transfer of reactive iron to a high arctic fjord the transport of reactive iron i e colloidal and dissolved by a glacier fed stream system draining a high relief periglacial landscape in the high arctic archipelago of svalbard is described a negative non linear relationship between discharge and iron concentration is found indicative of increased iron acquisition along baseflow pathways because the glaciers are cold based and there are no intra or sub permafrost groundwater springs baseflow is principally supplied by the active layer and the colluvial and alluvial sediments in the lower valley collectively these environments increase the flux of iron in the stream by 40 over a floodplain length of just 8 km resulting in 6 kg fe km 2a 1 of reactive iron export for a 20 glacierized watershed we show that pyrite oxidation in shallow groundwater flowpaths of the floodplain is the most important source of reactive iron although it is far less influential in the upper parts of the catchment where other sources are significant including ironstone and secondary oxide coatings microbial catalysis of the pyrite oxidation occurs in the floodplain enabling rapid hyporheic water exchange to enhance the iron fluxes at high discharge and cause the non linear relationship between discharge and reactive iron concentrations furthermore because the pyrite oxidation is tightly coupled to carbonate and silicate mineral weathering other nutrients such as base cations and silica are also released to the stream system our work therefore shows that high arctic floodplains should be regarded as critically important regulators of terrestrial nutrient fluxes to coastal ecosystems from glacial and periglacial sources copyright 2015 john wiley sons ltd

positive mass balance during the late 20th century on austfonna svalbard revealed using satellite radar interferometry determining whether increasing temperature or precipitation will dominate the cryo spheric response to climate change is key to forecasting future sea level rise the volume of ice contained in the ice caps and glaciers of the arctic archipelago of svalbard is small compared with that of the greenland or antarctic ice sheets but is likely to be affected much more rapidly in the short term by climate change this study investigates the mass balance of austfonna svalbard s largest ice cap equilibrium line fluxes for the whole ice cap and for individual drainage basins were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio echo sounding these fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was 5 6 2 0 10 8 m 3 a 1 three basins in the quiescent phase of their surge cycles contributed 75 of this accumulation the remaining volume may be attributable either to as yet unidentified surge type glaciers or to increased precipitation this result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere

hydrology and hydrochemistry of a deglaciating high arctic catchment svalbard summary the impact of deglaciation on contemporary hydrological and biogeochemical functioning in the rieperbreen foxfonna catchment in western svalbard was observed in 2007 2008 an overall negative mass balance was observed during 2007 mass loss was high below the equilibrium line altitude ela but spatially patchy mass increases due to superimposed ice and firn were evident above the ela runoff from above the ela was almost exclusively routed through low gradient hydraulically inefficient supraglacial flowpaths which fed steeper highly efficient supraglacial and englacial subglacial channels downstream as interaction with debris rich environments subglacial and proglacial was minimal and transit times were rapid below the ela runoff from supraglacial sources had a low solute content in addition two further parallel hydrological pathways existed snowmelt fed springs emerging from the glacier s contemporary marginal moraines and multiple shallow intermittent streams within recent moraines throughout the glacier forefield and along its northern moraine flank runoff from these additional pathways flowed through highly reactive sediments composed of shale carbonate and sandstones their intense chemical and physical weathering meant moraines were important sources of solute contribution to the catchment s bulk runoff chemistry ecological succession at the glacier margin is therefore highly likely to be dependent upon nutrient acquisition by hydrological processes within moraines as the catchment undergoes deglaciation

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

vertical distribution of water within the polythermal storglaciaren sweden 1 knowledge of water content and its distribution in polythermal glaciers is required to model their flow and thermal state however observations of water content variations with depth in polythermal glaciers are scarce water content can be estimated from radio wave speed because they depend on one another we obtained continuous profiles of radio wave speed variations with depth from zero offset radar profiles collected in boreholes approximately 80 m deep in the upper ablation area of storglaciaren northern sweden these profiles show that the microcrystalline water system in the temperate ice is relatively homogeneous the overall hydrothermal structure at this location is composed of a 20 m thick upper layer of cold water free ice underlain by a temperate ice layer whose average water content is 0 6 0 3 these results are corroborated by surface radar and thermistor measurements which show that the depth of the cold temperate transition is 21 m and the calculated water content at that transition is 0 6 0 1 these findings imply that the whole temperate ice layer is from 3 to 4 times softer than the cold ice and consequently that realistic ice flow models of polythermal glaciers should include the effect of water content on viscosity

temporal variations in flow velocity at finsterwalderbreen a svalbard surge type glacier inter and intra annual velocity variations are well known on alpine glaciers but their importance for arctic glaciers has only been recognized more recently this paper presents flow velocity data from finsterwalderbreen a 35 km 2 polythermal surge type glacier in southern svalbard that is presently 100 years into its quiescent phase field measurements of glacier surface velocities are available from 1950 52 and 1994 97 and mean velocities for the last decade are estimated for the lower glacier using cables drilled to the glacier bed these velocities show substantial seasonal variations indicating that basal sliding is an important component of surface velocities and interannual fluctuations of up to 75 possibly indicating variations in subglacial water storage several lines of evidence indicate that this glacier has an extensive subglacial hydrological system generally considered to be a prerequisite for surge type glaciers which is at least partly pressurized information on surface morphology from 1898 onwards shows that the glacier has experienced continuous retreat since the last surge in about 1910 and has now retreated 1 5 km further back than its previous pre surge position in 1898 tracking of moraine loops on terrestrial and aerial photographs acquired over a 100 year period indicates that the surge period of finsterwalderbreen may be lengthening in response to climate changes

recent extreme slope failures in glacial environments effects of thermal perturbation abstract this paper describes recent exceptional slope failures in high mountain glacial environments the 2002 kolka karmadon rock ice avalanche in the caucasus a series of ice rock avalanches on iliamna volcano alaska the 2005 mt steller rock ice avalanche in alaska and ice and rock avalanches at monte rosa italy in 2005 and 2007 deposit volumes range from 10 6 to 10 8 m 3 and include rock ice and snow here we focus on thermal aspects of these failures reflecting the involvement of glacier ice and permafrost at all sites suggesting that thermal perturbations likely contributed to the slope failures we use surface and troposphere air temperatures near surface rock temperatures satellite thermal data and recent 2d and 3d thermal modeling studies to document thermal conditions at the landslide sites we distinguish between thermal perturbations of volcanic geothermal and climatic origin and thermal perturbations related to glacier permafrost interaction the data and analysis support the view that recent current and future climatic change increases the likelihood of large slope failures in steep glacierized and permafrost terrain however some important aspects of these settings such as the geology and tectonic environment remain poorly understood making the identification of future sites of large slope instabilities difficult in view of the potentially large natural disasters that can be caused by such slope failures improved data and understanding are needed

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

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

identification of chernobyl fall out as a new reference level in northern hemisphere glaciers among the various artificial radioactive markers mainly from atmospheric nuclear tests the contamination from the chernobyl accident has been found at five sampling sites on northern hemisphere glaciers total beta activity measurements reveal a very high radio active level however due to the short time of its occurrence the temporal resolution of this event in the snow layers can be generally quite low and positive results require careful sampling the size of the signal also depends on the trajectory of the contaminant cloud the amount of precipitation and the surface conditions during deposition a stfonna ny alesun itsberg

1 subduction slab detachment and mineralization the neogene in the apuseni mountains and carpathians abstract the inner carpathians comprise several distinct neogene late stage orogenic pb zn cu ag au ore districts the mineral deposits in these districts are closely related to volcanic and subvolcanic rocks and represent mainly porphyry and epithermal vein deposits which formed within short periods of time in each district here we discuss possible geodynamic and structural controls that suggest why some of the neogene volcanic districts within the carpathians comprise abundant mineralization while others are barren the neogene period has been characterized by an overall geodynamic regime of subduction where primary roll back of the subducted slab and secondary phenomena like slab break off and the development of slab windows could have contributed to the evolution location and type of volcanic activity structural features developing in the overlying lithosphere and visible in the carpathian crust such as transtensional wrench corridors block rotation and relay structures due to extrusion tectonics have probably acted in focusing hydrothermal activity as a result of particular events in the geodynamic evolution and the development of specific structural features mineralization formed during fluid channelling within transtensional wrench settings and during periods of extension related to block rotation in the slovakian ore district of the western carpathians neogene volcanism and associated mineralization were localized by sinistral ne trending wrench corridors which formed part of the extruding alcapa block the baia mare ore district in the eastern carpathians reflects a transtensional wrench setting on distributed oversteps close to the termination of the dragos voda fault there mineralization was spatially controlled by the transtensional dragos voda master fault and associated cross fault systems the golden quadrangle cu au ore district of the southern apuseni mountains reflects an unusual rotated transtensional extensional setting close to the termination of a graben system there fluid flow was probably localized by fault propagation at the inner tip of the graben system the spatial and temporal evolution of the magmatism and its changing geochemical signature from n w to s e strongly suggests a link with the contemporaneous northeastward roll back of the subducted slab and a progressive southeastward detachment during accelerating roll back this geodynamic evolution is further supported by the present day overall and detailed mantle lithospheric density images the present day heat flow patterns the crustal architecture and its interpreted evolution and the spatial and temporal evolution of depocentres around the carpathian arc in contrast to all these features the mineral deposits in the west carpathians east carpathians and apuseni mountains are too synchronous with respect to their individual volcanic history and contrast too much with younger volcanics of similar style but barren in southeastern parts of the carpathians to simply link them directly to the slab evolution in all three districts the presence of magmatic fluids released from shallow plutons and their mixing with meteoric water were critical for mineralization requiring transtensional or extensional local regimes at the time of mineralization possibly following initial compressional regimes these three systems show that mineralization was probably controlled by the superposition of favourable mantle lithospheric conditions and partly independent evolving upper crustal deformation conditions in the 13 to 11 ma period the dominant mineralization formed all across the carpathians and was superimposed on structurally favourable crustal areas with at that time volcanic hydrothermal activity the period may reflect the moment when the upper part of the crust failed under lithospheric extension imposed by the slab evolution this crustal failure would have fragmented the overriding plate possibly breaking up the thermal lid to provoke intensive fluid flow in specific areas and allowed subsequent accelerated tectonic development block rotation and extrusion of a family of sub blocks that are arbitrarily regarded as the tisia dacia or alcapa blocks even though they have lost their internal entity

late holocene changes in character and behaviour of land terminating glaciers on james ross island antarctica virtually no information is available on the response of land terminating antarctic peninsula glaciers to climate change on a centennial timescale this paper analyses the topography geomorphology and sedimentology of prominent moraines on james ross island antarctica to determine geometric changes and to interpret glacier behaviour the moraines are very likely due to a late holocene phase of advance and featured 1 shearing and thrusting within the snout 2 shearing and deformation of basal sediment 3 more supraglacial debris than at present and 4 short distances of sediment transport retreat of 100m and thinning of 15 20m has produced a loss of 0 1km3 of ice the pattern of surface lowering is asymmetric these geometrical changes are suggested most simply to be due to a net negative mass balance caused by a drier climate comparisons of the moraines with the current glaciological surface structure of the glaciers permits speculation of a transition from a polythermal to a cold based thermal regime small land terminating glaciers in the northern antarctic peninsula region could be cooling despite a warming climate

origin evolution and dynamic context of a neoglacial lateral frontal moraine at austre lovenbreen svalbard moraines marking the neoglacial limits in svalbard are commonly ice cored investigating the nature of this relict ice is important because it can aid our understanding of former glacier dynamics this paper examines the composition of the lateral frontal moraine associated with the neoglacial limit at austre lovenbreen and assesses the likely geomorphological evolution the moraine was investigated using ground penetrating radar gpr with context being provided by structural mapping of the glacier based on an oblique aerial image from 1936 and vertical aerial imagery from 2003 multiple up glacier dipping reflectors and syncline structures are found in the gpr surveys the reflectors are most clearly defined in lateral positions where the moraine is substantially composed of ice the frontal area of the moraine is dominantly composed of debris the core of the lateral part of the moraine is likely to consist of stacked sequences of basal ice that have been deformed by strong longitudinal compression the long term preservation potential of the ice dominated lateral moraine is negligible whereas the preservation of the debris dominated frontal moraine is high a glacier surface bulge identified on the 1936 aerial imagery provides evidence that austre lovenbreen has previously displayed surge activity although it is highly unlikely to do so in the near future in its current state this research shows the value of relict buried ice that is preserved in landforms to aiding our understanding of former glacier characteristics

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

a model computation of moisture content in polythermal glaciers measurements in boreholes and internal radar horizons confirm the existence of polythermal structures in polar and subpolar glaciers and ice sheets the occurrence of an intraglacial phase boundary makes it necessary to consider two layers and transition conditions between cold and temperate ice the governing field equations and constitutive relations for a two layer model are stated with emphasis on boundary and transition conditions a reduced plane flow model is introduced by using dimensionless variables and performing a scale analysis according to the stated aim of this paper a parallel sided slab model is suitable for rough analyses of borehole measurements its governing equations are deduced and their analytical and numerical treatment is discussed sensitivity tests reveal a strong dependence of moisture content profiles on the numerical value of the water diffusivity coefficient and especially on strain heating

a refined apparent polar wander curve for the transdanubian central mountains and its bearing on the mediterranean tectonic history abstract recently obtained palaeomagnetic data have given a fairly detailed apparent polar wander a p w curve for the mesozoic of the transdanubian central mountains which has been compared with other a p w curves from the mediterranean area the similarity of the a p w curves enabled a unified a p w curve to be constructed for the central mediterranean region it has been shown that the new mediterranean a p w curve is in full agreement even in details with the updated a p w curve for africa this confirms the existence during the entire mesozoic of a single central mediterranean megatectonic unit rigidly attached to africa its positions with respect to the pole can now be traced back in more detail than before

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

the paleomagnetism of the upper cretaceous magmatic rocks in the banat area of south carpathians tectonic implications abstract forty four sites were sampled in upper cretaceous magmatic rocks in the western part of the southern carpathians banat area for a paleomagnetic study after detailed af demagnetization only 10 sites yielded primary remanent magnetizations the directions of which are similar to those identified in senonian magmatic rocks from the apuseni mountains and the ha eg and rusca montan basins the mean paleomagnetic pole for these three areas is compared with those from coeval formations of stable europe and stable africa this comparison shows a large clockwise rotation both with respect to africa and europe and a northward transport to reach their present day position during the tertiary the relations with adjacent zones of the tethys mobile belt are also discussed

thermal structure of svalbard glaciers and implications for thermal switch models of glacier surging switches between cold and warm based conditions have long been invoked to explain surges of high arctic glaciers here we compile existing and new data on the thermal regime of six glaciers in svalbard to test the applicability of thermal switch models two of the large glaciers of our sample are water terminating while one is land terminating all three have a well known surge history they have a thick basal layer of temperate ice superimposed by cold ice a cold terminus forms during quiescence but is mechanically removed by calving on tidewater glaciers the other three glaciers are relatively small and are either entirely cold or have a diminishing warm core all three bear evidence of former warm based thermal regimes and in two cases surge like behavior during the little ice age in svalbard therefore three types of glaciers have switched from slow to fast flow 1 small glaciers that underwent thermal cycles during and following the lia switches between cold and warm based conditions 2 large terrestrial glaciers which remain warm based throughout the entire surge cycle but develop cold termini during quiescence and 3 large tidewater glaciers that remain warm based throughout the surge cycle our results demonstrate that thermal switching cannot explain the surges of large glaciers in svalbard we apply the concept of enthalpy cycling to the spectrum of surge and surge like behavior displayed by these glaciers and demonstrate that all svalbard surge type glaciers can be understood within a single conceptual framework

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

geometry change between 1990 and 2003 at finsterwalderbreen a svalbard surge type glacier from gps profiling surface mass balance and geometry data are key to quantifying the climate response of glaciers and confidence in data synthesis and model interpretations and forecasts requires data from as wide a range of locations and glacier types as possible this paper presents measurements of surface elevation change at the svalbard surge type glacier finsterwalderbreen by comparing a 1990 digital elevation model dem with a surface gps profile from 2003 the pattern of elevation change is consistent with that previously noted between 1970 and 1990 and reflects the continued quiescent phase evolution of the glacier with mass loss in the down glacier receiving area of up to 1 25 m w e a 1 and mass gain in the up glacier reservoir area of up to 0 60 m w e a 1 the area weighted mean change for the whole glacier is 0 19 m w e a 1 the spatial pattern of elevation increase and decrease is complex and the boundary between thickening and thinning determined by combining gps and dem data does not appear to correspond with the equilibrium line altitude determined from surface mass balance measurements there is no evidence yet of a decrease in the rate of reservoir area build up driven by mass balance change resulting from the warmer winter air temperatures and decreased proportion of snowfall in total precipitation noted at meteorological stations in svalbard

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

a re analysis of the 58 year mass balance record of storglaciaren sweden the use of glacier mass balance records to assess the effects of glacier volume change from climate change requires high quality data the methods for measuring glacier mass balance have been developed in tandem with the measurements themselves which implies that the quality of the data may change with time we have investigated such effects on the mass balance record of storglaciaren sweden by re analyzing the records using a better map base and applying successive maps over appropriate time periods our results show that errors 10 year oscillations the pseudo cyclic signal must thus be explained by factors other than cyclically occurring phenomena although the record may still be too short to establish significant signals we strongly recommend re analysis of long mass balance records in order to improve the mass balance records used for other analyses

glacial geological studies of surge type glaciers in iceland research status and future challenges abstract surging glaciers are potential analogues for land terminating palaeo ice streams and surging ice sheet lobes and research on surge type glaciers is important for understanding the causal mechanisms of modern and past ice sheet instabilities the geomorphic signatures left by the icelandic surge type glaciers vary and range from glaciotectonic end moraines formed by folding and thrusting crevasse squeeze ridges concertina eskers drumlins and fluted forefields to extensive dead ice fields and even drift sheets where fast ice flow indicators are largely missing we outline some outstanding research questions and review case studies from the surge type outlets of bruarjokull eyjabakkajokull and tungnaarjokull vatnajokull ice cap mulajokull and satujokull hofsjokull ice cap hagafellsjokull and su urjokull langjokull ice cap kaldalonsjokull leirufjar arjokull and reykjarfjar arjokull drangajokull ice cap as well as the surge type cirque glaciers in northern iceland we review the current understanding of how rapid ice flow is sustained throughout the surge the processes that control the development of the surge type glacier landsystem and the geological evidence of surges found in sediments and landforms we also examine if it is possible to reconstruct past surge flow rates from glacial landforms and sediments and scale up present day surge processes landforms and landsystems as modern analogues to past ice streams finally we also examine if there is a climate mass balance control on surge initiation duration and frequency

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

paleomagnetic aspects of plate tectonics in the carpatho pannonian region paleomagnetic data available from the carpatho pannonian region are unevenly distributed at some places observations are sporadic at others the concentration is high in the latter case it is possible to decide whether the movements indicated are related to plate microplate displacements or are of local significance the paleomagnetically best known parts of the carpatho pannonian region belong to the transdanubian central range to the cserhat matra bukk area and to the mecsek villany zone comparison among paleomagnetic data sets characterizing each of them reveals fundamental differences i e points to their independent displacements during the mesozoic and cenozoic most of the isolated observations can be tied to one of the above mentioned paleomagnetic units via coeval mostly late cretaceous cenozoic data thus further subdivision of the carpatho pannonian area at least in the cenozoic does not seem required by available paleomagnetic observations

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

porphyry copper deposit density estimating numbers of undiscovered mineral deposits has been a source of unease among economic geologists yet is a fundamental task in considering future supplies of resources estimates can be based on frequencies of deposits per unit of permissive area in control areas around the world in the same way that grade and tonnage frequencies are models of sizes and qualities of undiscovered deposits to prevent biased estimates it is critical that for a particular deposit type these deposit density models be internally consistent with descriptive and grade and tonnage models of the same type in this analysis only deposits and prospects that are likely to be included in future grade and tonnage models are employed and deposits that have mineralization or alteration separated by less than an arbitrary but consistent distance 2 km for porphyry copper deposits are combined into one deposit only 286 deposits and prospects that have more than half of the deposit not covered by postmineral rocks sediments or ice were counted nineteen control areas were selected and outlined along borders of hosting magmatic arc terranes based on three main features 1 extensive exploration for porphyry copper deposits 2 definable geologic settings of the porphyry copper deposits in island and continental volcanic arc subduction boundary zones and 3 diversity of epochs of porphyry copper deposit formation porphyry copper deposit densities vary from 2 to 128 deposits per 100 000 km2 of exposed permissive rock and the density histogram is skewed to high values ninety percent of the control areas have densities of four or more deposits 50 percent have densities of 15 or more deposits and 10 percent have densities of 35 or more deposits per 100 000 km2 deposit density is not related to age or depth of emplacement porphyry copper deposit density is inversely related to the exposed area of permissive rock the linear regression line and confidence limits constructed with the 19 control areas can be used to estimate the number of undiscovered deposits given the size of a permissive area in an example of the use of the equations we estimate a 90 percent chance of at least four a 50 percent chance of at least 11 and a 10 percent chance of at least 34 undiscovered porphyry copper deposits in the exposed parts of the andean belt of antarctica which has no known deposits in a permissive area of about 76 000 km2 measures of densities of deposits presented here allow rather simple yet robust estimation of the number of undiscovered porphyry copper deposits in exposed or covered permissive terranes

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

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

polythermal glacier hydrology a review 1 the manner by which meltwater drains through a glacier is critical to ice dynamics runoff characteristics and water quality however much of the contemporary knowledge relating to glacier hydrology has been based upon and conditioned by understanding gleaned from temperate valley glaciers globally a significant proportion of glaciers and ice sheets exhibit nontemperate thermal regimes the recent growing concern over the future response of polar glaciers and ice sheets to forecasts of a warming climate and lengthening summer melt season necessitates recognition of the hydrological processes in these nontemperate ice masses it is therefore timely to present an accessible review of the scientific progress in glacial hydrology where nontemperate conditions are dominant this review provides an appraisal of the glaciological literature from nontemperate glaciers examining supraglacial englacial and subglacial environments in sequence and their role in hydrological processes within glacierized catchments in particular the variability and complexity in glacier thermal regimes are discussed illustrating how a unified model of drainage architecture is likely to remain elusive due to structural controls on the presence of water cold ice near glacier surfaces may reduce meltwater flux into the glacier interior but observations suggest that the transient thermal layer of near surface ice holds a hydrological role as a depth limited aquifer englacial flowpaths may arise from the deep incision of supraglacial streams or the propagation of hydrofractures forms which are readily able to handle varied meltwater discharge or act as locations for water storage and result in spatially discrete delivery of water to the subglacial environment the influence of such drainage routes on seasonal meltwater release is explored with reference to summer season upwellings and winter icing formation moreover clear analogies emerge between nontemperate valley glacier and ice sheet hydrology the discussion of which indicates how persistent reassessment of our conceptualization of glacier drainage systems is required there is a clear emphasis that continued integrated endeavors focused on process glaciology at nontemperate glaciers are a scientific imperative to augmenting the existing body of research centered on ice mass hydrology

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

fracturing block faulting and moulin development associated with progressive collapse and retreat of a maritime glacier falljokull se iceland since 2007 falljokull in southeast iceland has been undergoing passive downwasting providing an ideal opportunity to study a range deformation structures developed in response to ice marginal collapse and retreat an integrated terrestrial lidar ground penetrating radar and glaciological structural study of the clean debris free ice at the margin of falljokull has allowed a detailed model of the surface and subsurface 3d structure to be developed collapse of the glacier margin takes the form of a multiple rotational failure controlled by large scale down ice dipping normal faults as the fault bound blocks of ice are displaced downslope they rotate leading to localized compression and the formation of down faulted graben like structures moulins present within the marginal zone of falljokull are closely associated with the zones of relatively more intense brittle deformation which crosscut the glacier a model is proposed where the moulins have formed in response to the progressive collapse of englacial drainage channels located along down ice dipping normal faults the preferential development of the moulins and englacial drainage channels along the normal faults weakens the ice along these structures promoting or even accelerating further collapse of the ice margin the complex pattern of surface lowering within the marginal zone of falljokull has also been shown to be directly related to movement on the main faults controlling the collapse of the ice margin this evidence suggests that structurally controlled collapse may in some instances have a profound effect on glacier surface lowering and geodetic mass balance measurements

cold ice in the ablation zone its relation to glacier hydrology and ice water content 1 cold ice within a polythermal ice body controls its flow dynamics through the temperature dependence of viscosity and affects glacier hydrology by blocking water flow paths lakes on the surface linked by persistent deeply incised meltwater streams are hallmark features of cold ice in the ablation zone of a glacier or ice sheet ice radar is a convenient method to map scattering from internal water bodies present in ice at the pressure melting temperature pmt consequently lack of internal scatters is indicative of cold ice we use a helicopter borne 30 mhz ice radar to delineate the extent of cold ice within grenzgletscher zermatt swiss alps the inferred thermal structure is validated with temperature measurements in 15 deep boreholes showing excellent agreement the cold ice occupies 80 90 of the total ice thickness in a 400 m wide flow band along the central flow line quantitative interpretation of ice radar scattering power indicates a decrease of ice water content between pmt and 0 5 k below pmt as predicted by theory and observed in the laboratory the cold ice which emerges at the surface in the lower ablation zone is impermeable to water and is thus devoid of moulins if not crevassed the surface water from melt and rain is routed through deeply incised persistent streams and lakes and cryoconite holes are frequent in stark contrast to the adjacent temperate ice from other tributaries the cold ice thus has a strong control on glacier hydrology but is likely to change due to continued warming

rapid recent warming on rutford ice stream west antarctica from borehole thermometry 1 the antarctic peninsula has warmed faster than the global average rate of warming during the last century due to limited availability of long term meteorological records the geographical extent of this rapid warming is poorly defined we collected borehole temperature measurements in the upper 300 m of rutford ice stream west antarctica and employed an inverse modeling scheme with a heat diffusion advection equation to determine the recent surface temperature history of the borehole position our results reveal recent warming of 0 17 0 07 c decade 1 since 1930 this result suggests that at least in an attenuated form the rapid warming observed over the antarctic peninsula extends as far south as rutford ice stream this result agrees with other recent results that show a warming trend across much of the west antarctic ice sheet

cold temperate transition surface and permafrost base cts pb as an environmental axis in glacier permafrost relationship based on research carried out on the storglaciaren and its forefield northern sweden here we present empirical ground penetrating radar gpr and electroresistivity tomography data ert to verify the cold temperate transition surface permafrost base cts pb axis theoretical model the data were collected from storglaciaren in tarfala northern sweden and its forefield the gpr results show a material relation between the glacial ice and the sediments incorporated in the glacier and a geophysical relation between the cold ice and the temperate ice layers clearly identifying lateral glacier margins is difficult as periglacial and glacial environments frequently overlap in this case we identified areas showing permafrost aggradation already under the glacier particularly where the cts is replaced by the pb surface this structure appears as a result of the influence of a cold climate over both the glacial and periglacial environments the results show how these surfaces form a specific continuous environmental axis thus both glacial and periglacial areas can be treated uniformly as a specific continuum in the geophysical sense similarly other examples previously described also allow identifying a continuation of permafrost from the periglacial environment onto the glacial base in addition the ert results show the presence of double layered periglacial permafrost possibly suggesting a past climatic fluctuation in the study area

calculation of sensible heat flux over a melting ice surface using simple climate data and daily measurements of ablation sensible heat flux is obviously important for glacier ablation but is difficult to measure routinely sensible heat flux can be estimated from wind speed and temperature data using a dimensionless heat transfer coefficient values of the heat transfer coefficient are evaluated for six sites by correlating measured melt energy with a wind temperature variable product of daily mean wind speed temperature and mean atmospheric pressure for the altitude in question data are available for short periods from two sites in arctic canada and two sites in north greenland and for hundreds of days of record at nordbogletscher and qamanarssup sermia in south and west greenland respectively average transfer coefficients for four out of the six sites are close to 0 003 which is in reasonable agreement with values reported elsewhere while larger values of 0 0047 and 0 0057 are found at the other two sites heat transfer coefficients are also estimated on a monthly basis for the two long records and substantial variations are found suggesting that the method should not be used for 20 30 days of data the present study is based on manually observed ablation and climate data but the approach could be updated to use data from automatic recording stations using modern sensors

development of the pannonian basin basement through the cretaceous cenozoic collision a new synthesis abstract a geodynamic analysis was carried out going back in time from the present the collision took place during the cretaceous and cenozoic based on the subduction origin of the neogene calc alkalic volcanites three microplates are delineated the southern and the northern ones are approximately the same as in previous plate tectonic syntheses but the third one is outlined here for the first time as the basement of a miocene island arc restoring the former position of microplates a basin of oceanic crust is outlined on the site of the present pannonian basin of continental crust at the beginning of the neogene the present northern microplate was located somewhere west of this basin and the present southern one was located on its southern shelf the reconstructed cretaceous paleogene histories of these microplates were different during the whole barremian to oligocene time interval the southern microplate was located on the passive margin of an oceanic basin which was coming into being through continental rifting of the european plate margin in the valanginian to hauterivian the northern microplate located on the african plate margin was undergoing collision with an island arc in the early cretaceous the oceanic basin of marginal see type behind this island arc was closed along a southerly directed subduction zone in the eocene this resulted in the appearance of a calc alkalic volcano chain along this microplate and in a new basin opening behind this marginal sea basin divided the present northern microplate from the african plate and joined the oceanic basin north of the present southern microplate the present pannonian basin was assembled as a lithospheric mosaic through convergent and transcurrent movements of the defined microplates during the neogene sediments of the former oceanic basin now strike along the contacts of continental microplates as flysch belts

flow mechanism of glaciers on soft beds subhourly measurements of bed deformation bed shear strength subglacial water pressure and surface speed at storglaciaren a glacier in northern sweden showed that the shear strain rates of the bed decrease during periods of high water pressure and surface speed high water pressures appear to be accompanied by a reduction in the coupling of ice with the bed that is sufficient to reduce or eliminate shearing the instability of large ice masses may result from similar decoupling rather than from pervasive bed deformation as has been commonly thought

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