automated detection of unstable glacier flow and a spectrum of speedup behavior in the alaska range surge type glaciers are loosely defined as glaciers that experience periodic alterations between slow and fast flow regimes glaciers from a variety of mountain ranges around the world have been classified as surge type yet consensus of what defines a glacier as surge type has not always been met a common source of dispute is the lack of a succinct and globally applicable delimiter between a surging and nonsurging glacier the attempt is often a boolean classification however glacier speedup events can vary significantly with respect to event magnitude duration and the fraction of the glacier that participates in the speedup for this study we first updated the inventory of glaciers that show flow instabilities in the alaska range and then quantified the spectrum of speedup behavior we developed a new method that automatically detects glaciers with flow instabilities our automated results show a 91 success rate when compared to direct observations of speedup events and glaciers that are suspected to display unstable flow based on surface features through a combination of observations from the landsat archive and previously published data our inventory now contains 36 glaciers that encompass at least one branch exhibiting unstable flow and we document 53 speedup events that occurred between 1936 and 2014 we then present a universal method for comparing glacier speedup events based on a normalized event magnitude metric this method provides a consistent way to include and quantify the full spectrum of speedup events and allows for comparisons with glaciers that exhibit clear surge characteristics yet have no observed surge event to date our results show a continuous spectrum of speedup magnitudes from steady flow to clearly surge type which suggests that qualitative classifications such as surge type or pulse type behavior might be too simplistic and should be accompanied by a standardized magnitude metric

regional retrograde metamorphism of a high grade terrain the willyama complex broken hill australia abstract retrograde metamorphism has been a major influence in the development of the presently observed lithologies of the willyama complex broken hill two broad types of retrogression are distinguished pseudomorphous and kinematic retrogression the former type of retrogression involves replacement of prograde phases without complete loss of the high grade fabric hence the prograde assemblage can frequently be inferred kinematic retrogression involves the development of a new schistose fabric and like pseudomorphous retrogression is commonly related to f3 deformation retrogression was initiated during the waning stage of prograde metamorphism and was accompanied by an influx of aqueous fluid at similar pressure but lower temperature conditions than prograde metamorphism the source of the water is believed to be the crystallization of cooling partial melts the regional nature of this willyama style of retrogression is attributed to the metasediment rich nature of the sequence the high geothermal gradient and the considerable amount of in situ partial melting

genetic implications of pyrite chemistry from the palaeoproterozoic olary domain and overlying neoproterozoic adelaidean sequences northeastern south australia abstract sulphide mineralisation associated with rocks from the palaeoproterozoic olary domain od and overlying neoproterozoic adelaidean sequences has undergone a complex history of metamorphism and remobilisation in this study new trace element and sulphur isotopic analyses of pyrites from a large number of deposits and paragenetic generations are combined with an existing data set to build up a sequence of mineralising events linked to the tectonometamorphic evolution of the region the typically high co ni ratios 10 indicate that early strata bound pyrite precipitated from a volcanic related fluid which had fluctuating activities of the two metals during the early stages of the evolution of the willyama basin this period of mineralisation was followed by a diagenetic concentration of sulphide mineralisation at the horizon known as the bimba formation which occurred as a result of the differing redox conditions between the upper and lower sequences in the willyama supergroup during the mesoproterozoic 1600 to 1500 ma olarian orogeny metamorphic remobilisation of strata bound pyrite resulted in an epigenetic signature the trace element concentrations of this generation were controlled primarily by the proximity of mineralisation to the mafic intrusive bodies found throughout the terrane further reworking of existing sulphides during the delamerian orogeny and associated granitoid intrusive rocks led to the formation of a new generation of epigenetic pyrite that occurs in quartz veins in the adelaidean sequences and veins that crosscut olarian fabrics in the olary domain 34s results range from 16 to 11 but most data fall between 2 and 4 this association is suggestive of an initial uniform deep seated crustal reservoir of sulphur which has been repeatedly tapped throughout the metallogenic history of the region the isotopic outliers can be explained by the input of biogenic sulphur or sulphur derived from oxidised possibly evaporitic sediments respectively previous workers have invoked the kupferschiefer and the zambian copperbelt as analogues to mineralisation processes in the olary domain this study shows that 34s and trace element data are suggestive of some affinities with the aforementioned analogues but a more likely link can be made between epigenetic remobilisation in the olary region and the iron oxide copper gold iocg style of mineralisation found at the nearby olympic dam deposit

deformation enhanced fluid distribution in feldspar aggregates and implications for ductile shear zones experiments at 900 c and 1 4 gpa show that the distribution of aqueous fluid in fine grained feldspar aggregates changes from isolated pores under hydrostatic conditions to mostly wetted grain boundaries during deformation the isolated pore distribution is rapidly regained during annealing following deformation the deformation enhanced fluid distribution causes a switch from dislocation creep to diffusion creep accompanied by a significant decrease in strength it also increases the bulk transport rate through the aggregate by more than an order of magnitude a change in fluid distribution is not observed in fine grained quartz aggregates deformed at similar conditions if deformation enhanced fluid distribution occurs in naturally deformed feldspathic rocks it could help to explain the localization of strain and enhancement of bulk transport in ductile shear zones

late weichselian and holocene sedimentary palaeoenvironment and glacial activity in the high arctic van keulenfjorden spitsbergen high arctic fjords for example van keulenfjorden on spitsbergen provide valuable palaeoenvironmental archives as they typically contain landforms and sediment sequences that document past changes in glacial activity with high temporal resolution van keulenfjorden was covered with a grounded glacier during the last glacial and it was deglaciated between c 11 8 and 11 3 cal ka bp the retreat of the ice front accelerated from approximately 80 to 190 m a during the deglaciation the maximum late holocene glacier extent occurred after surge like advances of the glacier nathorstbreen between 2790 and 2610 cal yr bp i e during a period with the coldest climatic conditions on svalbard this maximum extent was reached approximately 2600 years earlier than inferred for most fjords on svalbard suggesting that surge like glacier advances on svalbard can occur under variable climatic conditions the time interval between the advances of nathorstbreen around 2 7 ka bp was approximately 100 150 years this is comparable to the last and only historically known quiescent phase of nathorstbreen of c 120 years between the late 19th century and the most recent surge from 2003 to 2012

secular gravity variation at svalbard norway from ground observations and grace satellite data the svalbard archipelago norway is affected by both the present day ice melting pdim and glacial isostatic adjustment gia subsequent to the last pleistocene deglaciation the induced deformation of the earth is observed by using different techniques at the geodetic observatory in ny alesund precise positioning measurements have been collected since 1991 a superconducting gravimeter sg has been installed in 1999 and six campaigns of absolute gravity ag measurements were performed between 1998 and 2007 moreover the gravity recovery and climate experiment grace satellite mission provides the time variation of the earth gravity field since 2002 the goal of this paper is to estimate the present rate of ice melting by combining geodetic observations of the gravity variation and uplift rate with geophysical modelling of both the gia and earth s response to the pdim we estimate the secular gravity variation by superimposing the sg series with the six ag measurements we collect published estimates of the vertical velocity based on gps and vlbi data we analyse the grace solutions provided by three groups csr gfz grgs the crux of the problem lies in the separation of the contributions from the gia and pdim to the earth s deformation to account for the gia we compute the response of viscoelastic earth models having different radial structures of mantle viscosity to the deglaciation histories included in the models ice 3g or ice 5g to account for the effect of pdim we compute the deformation of an elastic earth model for six models of ice melting extension and rates errors in the gravity variation and vertical velocity are estimated by taking into account the measurement uncertainties and the variability of the grace solutions and gia and pdim models the ground observations agree with models that involve a current ice loss of 25 km3 water equivalent yr 1 over svalbard whereas the space observations give a value in the interval 5 18 km3 water equivalent yr 1 a better modelling of the pdim which would include the precise topography of the glaciers and altitude dependency of ice melting is necessary to decrease the discrepancy between the two estimates

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

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

geometry changes on svalbard glaciers mass balance or dynamic response the geometry of glaciers is affected by both the mass balance and the dynamics we present repeated gps measurements of longitudinal altitude profiles on three glaciers in svalbard and show that surface altitude changes alone cannot be used to assess the mass balance the three measured glaciers are in different dynamic modes and the observed changes in geometry are strongly affected by the dynamics nordenskioldbreen shows no significant change in the geometry indicating that the mass balance is in steady state with the dynamics on amundsenisen the surface has lowered by 1 5 2 0 m a 1 in the lower part of the accumulation area at 520 550 m a s l indicating that the ice flux is higher than the mass balance input probably due to a surge advance of the glacier further downstream affecting the higher part of the drainage area on kongsvegen the opposite situation was found here the geometry of the profile showed a clear build up of 0 5 m a 1 in the accumulation area and a lowering of 1 m a 1 in the lower part of the ablation area the ice velocity is very low giving a negligible vertical velocity component and an ice flux that is far smaller than the mass balance flux indicating that the glacier is building up towards a surge advance our results show that if mapping of height changes is to be used to monitor the response of the glaciers to climate change both surface net mass balance data and dynamic data are needed

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

over 400 previously undocumented svalbard surge type glaciers identified abstract identifying glaciers that exhibit surge type behavior is important when using evidence of ice front fluctuations as a proxy for reconstructing past climate oscillations this study identifies previously undocumented surge type glaciers in svalbard based on the presence of crevasse squeeze ridges in glacier forelands crevasse squeeze ridges are landforms suggested to be unique to surging glacier land systems estimates vary greatly as to the actual percentage of surge type glaciers in svalbard and consequently their distribution pattern is poorly understood a detailed survey of recent 2008 2012 high resolution aerial imagery from toposvalbard provided by the norwegian polar institute allowed for a survey of all the glacier forelands in svalbard before our study 277 individual glaciers in svalbard have been documented to exhibit surge behavior by using crevasse squeeze ridges as indicators of surge behavior we have identified 431 additional glaciers that have surged we suggest that this is a modest value as the unique surge landforms were not visible in approximately one third of the forelands with documented surge histories limits to the crevasse squeeze ridge technique are presented and potential controlling factors for crevasse squeeze ridge formation preservation are discussed

tidewater glacier surges initiated at the terminus terrasar x data were provided by dlr project oce1503 and funded by the conoco phillips lundin northern area program through the crios project calving rates and impact on sea level c n acknowledges funding from european union erc grant 320816 and esa project glaciers cci 4000109873 14 i nb

permanent fast flow versus cyclic surge behaviour numerical simulations of the austfonna ice cap svalbard a large part of the ice flux within ice caps occurs through spatially limited fast flowing units some of them permanently maintain fast flow whereas others operate in an oscillatory mode characterized by short lived active phases followed by long quiescent phases this surge type behaviour results from intrinsic rather than external factors thus complicating estimates of glacier response to climate change here we present numerical model results from austfonna an ice cap on svalbard that comprises several surge type basins previous studies have suggested a thermally controlled soft bed surge mechanism for svalbard we systematically change the parameters that govern the nature of basal motion and thereby control the transition between permanent and oscillatory fast flow surge type behaviour is realized by a relatively abrupt onset of basal sliding when basal temperatures approach the pressure melting point and enhanced sliding of marine grounded ice irrespective of the dynamic regime the absence of considerable volumes of temperate ice both in the observed and simulated ice cap indicates that fast flow is accomplished by basal motion over a temperate bed given an idealized present day climate the equilibrium ice cap size varies significantly depending on the chosen parameters

stratigraphic and structural constraints on the proterozoic tectonic history of the olary block south australia abstract the lower proterozoic of the olary block is divided into five rock suites defining a conformable stratigraphic sequence correlated with the willyama supergroup of the broken hill block which has a probable depositional age no greater than 1800 ma the sequence was deformed and metamorphosed during the olarian orogeny at 1580 ma definition of the stratigraphy permits regional structural analysis and the resolution of two folding events an initial recumbent fold terrain redeformed by upright folds with a near vertical axial surface the olarian orogeny comprises a single regional compression axis with both folding events indicating a se direction of transport the described tectonic fabrics are consistent with simple shear deformation generating the early recumbent terrain

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

the influence of climate during and after a glacial surge a comparison of the last two surges of fridtjovbreen svalbard abstract glacial surges are periods of fast flow often limited in space and time and driven by internal conditions which are not fully explained the quantity and variety of documented case studies and settings demonstrate that the critical variables are difficult to isolate in an alternative approach two surges from the same basin were compared at fridtjovhamna one of the few known sites where this is possible fridtjovbreen is a polythermal glacier that has been through two recent surges the last event 1991 2002 occurred during an unusually warm period in the high arctic whereas the previous surge culminated in 1861 around the little ice age when many svalbard glaciers had their maximum holocene extent based on a multi disciplinary study processes and landforms from the two episodes were compared with respect to ice front movement rates formation and decay of ice cored moraines and glacial meltwater drainage patterns the study demonstrates that moraines and meltwater traces from the oldest surge locally well preserved provide excellent opportunities for reconstructing the behavior of the ice mass the last surge however took place during a period with ablation rates never seen at this latitude and 10 years after the maximum extent the deglaciated areas onshore hardly show traces from the event

a microstructural and argon laserprobe study of shear zone development at the western margin of the nanga parbat haramosh massif western himalaya a sample of banded amphibolite from the western margin of the nanga parbat haramosh massif as sassi has been studied using microstructural and 40ar 39ar laserprobe techniques to investigate the relationship between deformation and argon isotope variations in a natural system amphibolite grade deformation occurred during south directed overthrusting of the kohistan arc over india along the main mantle thrust and was overprinted by extensional reactivation of the earlier fabric and the formation of biotite rich shear zones subsequent deformation along discrete fine grained fault zones was characterised by the formation of scapolite chlorite and k feldspar early plastic deformation and later cataclasis different minerals developed during this history show a wide range in apparent 40ar 39ar ages biotite chlorite and scapolite exhibit much lower concentrations of excess argon indicating their equilibration in a fluid relatively poor in excess argon a true age of ca 8 ma from biotite represents a minimum age for deformation associated with formation of the nanga parbat syntaxis and also precludes pliocene metamorphism in this area of the syntaxis both high and low closure temperature minerals amphiboles and feldspars record apparent ages which are associated with the incorporation of excess argon within the mineral lattice although differential thermal resetting of minerals at different closure temperatures is important variations in the inherited 40ar 36ar ratio throughout the sample is dominated by deformation and fluid infiltration consequently it appears that within deforming metamorphic rocks areas with significantly different argon isotope compositions may be present and need not be homogenised by diffusion

the geomorphic imprint of glacier surges into open marine waters examples from eastern svalbard abstract seafloor morphology beyond nine tidewater glaciers terminating in open marine settings in eastern svalbard has been investigated using multibeam swath bathymetry historical information on tidewater glacier fluctuations over the past century or so shows that the seafloor offshore has been exposed only recently most glaciers have been observed to surge or have looped surface moraines indicating past surges during these ice advances and subsequent retreat a well preserved submarine landform assemblage has been produced a subglacial landforms include overridden moraine ridges mega scale glacial lineations msgls other streamlined lineations elongate drumlins and medial moraines small ridges forming a complex boxwork or rhombohedral pattern and meltwater related eskers and channels b ice marginal landforms include large terminal moraines with debris flow lobes on their outer flanks and indentations on their inner sides small transverse retreat moraines and crater like kettle holes c glacimarine features include iceberg ploughmarks and an otherwise relatively smooth sedimentary seafloor produced by fine grained debris rain out a schematic plan view landform assemblage model for tidewater glaciers advancing into open marine settings is developed arcuate terminal moraines marking the ice advance limit provide a distinctive component submarine basin s exposed inside these moraine ridges when ice retreats contain suites of individual landforms produced subglacially and ice marginally with a consistent order of timing of deposition and stratigraphic superposition the new schematic model is compared with earlier models based on submarine landforms associated with surges in the more topographically constrained setting of spitsbergen fjords differences include i the overall arcuate shape of the open marine assemblage ii the indented ice proximal sides of terminal moraine ridges iii the fan shaped pattern of streamlined lineations iv crater like kettle holes at the inner lateral margins of many submarine basins v prominent systems of eskers and channels modern glaciological analogues from ongoing surges of ice caps in eastern svalbard and severnaya zemlya provide contemporary observations of ice advance into open marine settings including heavily crevassed ice lobes with finger like termini

reconstruction of former glacier surface topography from archive oblique aerial images abstract archive oblique aerial imagery offers the potential to reconstruct the former geometry of valley glaciers and other landscape surfaces whilst the use of structure from motion sfm photogrammetry with multiview stereopsis mvs to process small format imagery is now well established in the geosciences the potential of the technique for extracting topographic data from archive oblique aerial imagery is unclear here sfm mvs is used to reconstruct the former topography of two high arctic glaciers midtre and austre lovenbreen svalbard norway using three archive oblique aerial images obtained by the norwegian polar institute in 1936 the 1936 point cloud was produced using seven lidar derived ground control points located on stable surfaces in proximity to the former piedmont glacier termini to assess accuracy the 1936 data set was compared to a lidar data set using the m3c2 algorithm to calculate cloud to cloud differences for stable areas such as nonglacial surfaces vertical differences were detected between the two point clouds rms m3c2 vertical difference of 8 5 m with the outwash zones adjacent to the assessed glacier termini showing less extensive vertical discrepancies 94 of m3c2 vertical differences between 5 m this research highlights that historical glacier surface topography can be extracted from archive oblique aerial imagery but accuracy is limited by issues including the lack of camera calibration the quality and resolution of the archive imagery and by the identification of suitable ground control to demonstrate the value of historical glacier surfaces produced using oblique archive imagery the reconstructed glacier surface topography is used to investigate evidence of a potential former surge front at the high arctic valley glacier austre lovenbreen a glacier identified to have potentially exhibited surge type behaviour during the neoglacial a surface bulge of 15 20 m is resolved on the 1936 model however when compared with the now deglaciated former subglacial topography a surge origin for the surface feature becomes unclear the processed 1936 oblique imagery was also used to produce orthorectified nadir aerial imagery from which structural mapping was undertaken this adds to the existing 1948 1995 structural map series for these glaciers this research demonstrates the potential of sfm mvs for reconstructing historical glacier surfaces which is important for aiding our understanding of former glacier dynamics and enabling the rapid assessment of glacier change over time

oxygen isotope geothermometers for metamorphic rocks the chicago mineral carbonate oxygen isotope fractionation curves have been combined with mineral water fractionation data for jadeite zoisite and rutile and new data for grossular water to provide a set of self consistent mineral pair calibrations the a coefficients in the equation 1000 in a 106t 2 of the new mineral pair fractionations are jadeite zoisite grossular rutile quartz 1 69 2 00 3 03 5 02 jadeite 0 31 1 34 3 33 zoisite 1 03 3 02 grossular 1 99 the isotopic fractionation properties of natural pyralspite garnet ca fe mg mn 3al2si3o12 can be approximated by those of the grossular end member appropriate substitutions also yield coefficients for the solid solution minerals sodic pyroxene and epidote e g aquartz sodic pyroxene 2 75 1 06xjd aquartz epidote 2 00 0 75xps where xjd and xps are the mole fractions of the jadeite and pistacite components respectively the new data set is particularly suitable for the geothermometry of metamorphic rocks 18o data from minerals of the high pressure metamorphic rocks of the sesia zone of italy and cyclades complex of greece yield well constrained mean temperatures of 572 and 478d c respectively type iii blueschist metabasalts of the franciscan formation of california give mean quartz garnet temperatures of 354d c

glacier volume changes using aster satellite stereo and icesat glas laser altimetry a test study on edgeoya eastern svalbard currently one of the major methodological gaps in the observation of glaciers from space is the measurement of volume changes of mountain glaciers and ice caps in this paper we present a case study of comparing a digital elevation model derived from advanced spaceborne thermal emission and reflection radiometer aster satellite optical stereo elevation data derived from ice cloud and land elevation satellite geoscience laser altimeter system glas laser altimetry and contour lines from a topographic map from the 1970s for two ice caps in eastern svalbard kvalpyntfonna and digerfonna we obtain an overall elevation change of 0 55 or 0 61 m year between 1970 and 2002 aster or glas 2006 respectively from comparison of different methods and from different quality checks we estimate the error of this numbers to be on the order of 5 this paper demonstrates that and on how long term glacier volume changes can be observed from space over a large number of ice caps and glaciers

late weichselian local ice dome configuration and chronology in northwestern svalbard early thinning late retreat the chronology and configuration of the svalbard barents sea ice sheet sbsis during the late weichselian lw are based on few and geographically scattered data thus the timing and configuration of the sbsis has been a subject of extensive debate we present provenance data of erratic boulders and cosmogenic 10be ages of bedrock and boulders from northwest spitsbergen nws svalbard to determine the thickness configuration and chronology during the lw we sampled bedrock and boulders of mountain summits and summit slopes along with erratic boulders from coastal locations around nws we suggest that a local ice dome over central nws during lw drained radially in all directions provenance data from erratic boulders from northern coastal lowland reinsdyrflya suggest northeastward ice flow through liefdefjorden 10be ages of high elevation erratic boulders in central nws 687 836 m above sea level ranging from 18 3 1 3 ka to 21 7 1 4 ka indicate that the centre of a local ice dome was at least 300 m thicker than at present 10be ages of all high elevation erratics 400 m above sea level central and coastal locations indicate the onset of ice dome thinning at 25 20 ka 10be ages from erratic boulders on reinsdyrflya ranging from 11 1 0 8 ka to 21 4 1 7 ka indicate an ice cover over the entire reinsdyrflya during lw and a complete deglaciation prior to the holocene but apparently later than the thinning in the mountains lack of moraine deposits but the preservation of beach terraces suggest that the ice covering this peninsula possibly was cold based and that reinsdyrflya was part of an inter ice stream area covered by slow flowing ice as opposed to the adjacent fjord which possibly was filled by a fast flowing ice stream despite the early thinning of the ice sheet 25 20 ka we find a later timing of deglaciation of the fjords and the distal lowlands several bedrock samples 10be from vertical transects in the central mountains of nws pre date the lw and suggest either ice free or pervasive cold based ice conditions our reconstruction is aligned with the previously suggested hypothesis that a complex multi dome ice sheet configuration occupied svalbard and the barents sea during lw with numerous drainage basins feeding fast ice streams separated by slow flowing possibly cold based inter ice stream areas

geochemical and stable isotope resetting in shear zones from taschalp constraints on fluid flow during exhumation in the western alps fluid flow at greenschist facies conditions during exhumation of the western alps occurred in several penecontemporaneous systems including shear zones at lithological contacts deformed contacts between serpentinite bodies and metabasalts albite veins within metabasalts and calcite quartz veins within calcareous schists fluid flow in shear zones that juxtapose metasediments and ophiolitic rocks within the piemonte unit reset o and h isotope ratios 18o values are buffered by the wall rocks however calculated fluid 2h values are similar within all the shear zones suggesting that they formed an interconnected network the similarity of 2h values of the sheared rocks and those of unsheared calcareous schists suggests that the fluids were derived from or had equilibrated with the schists that envelop the ophiolite rocks time integrated fluid fluxes at the sheared contacts estimated from changes in si in metabasalts were up to 105 m3 m 2 with the fluid flowing up temperature driven either by topography or seismic pumping individual shear zones were active for c 2 3 myr implying average fluid fluxes of up to 10 9 m3 m 2 s 1 rocks in shear zones within the ophiolite away from contacts with the metasediments show much less marked isotopic and geochemical changes implying that fluid volumes decreased into the ophiolite unit consistent with the source of fluids being the metasediments fluids were generated by dehydration reactions that were intersected during exhumation and while many rocks show the affects of fluid rock interaction large scale fluid flow between major units was not common

flow thermal structure and subglacial conditions of a surge type glacier temperature measurements in a subpolar surge type glacier reveal a distinctive thermal structure associated with the boundary between the ice reservoir and receiving areas in the receiving area the glacier is cold based but bottom temperature has increased as much as 0 5 c between 1981 and 1982 and the basal heat flux is roughly 10 times the expected geothermal flux water percolation through permeable subglacial material is the probable energy source deformation of the substrate could destroy this drainage system and trigger a surge

the flow of surface derived fluids through alice springs age middle crustal ductile shear zones reynolds range central australia the south east reynolds range central australia is cut by steep north west trending alice springs age c 334 ma shear zones that are up to hundreds of metres wide and several kilometres long with reverse senses of movement amphibolite facies 550 600 c 500 600 mpa shear zones cut metapelites while greenschist facies shear zones 420 535 c 400 650 mpa cut metagranites the sheared rocks commonly underwent metasomatism implying that the shear zones were the pathways of significant fluid flow altered granites within greenschist facies shear zones have gained si and k but lost ca and na relative to their unsheared counterparts suggesting that the fluid flowed down temperature and hence probably upward through the shear zones time integrated fluid fluxes calculated from silica addition are up to 2 1 1010 mol m 2 c 4 2 105 m3 m 2 similar time integrated fluid fluxes are also estimated from changes in k and na the sheared granitic rocks locally have 18o values as low as 0 which is much lower than the 18o values of the adjacent unsheared granites 7 to 9 implying that the fluid which flowed through these shear zones was derived from the surface for the estimated time integrated fluid fluxes the fluids would be able to retain their isotopic signature for many tens to hundreds of kilometres the flow of surface derived fluids into the ductile middle crust with subsequent expulsion upwards through the shear zones may have been driven by seismic activity accompanying the alice springs deformation

metamorphic events in the eastern arunta inlier part 2 nd_sr_ar isotopic constraints in the harts ranges the central province of the eastern arunta inlier is characterised by upper amphibolite facies ortho and paragneisses previously published u pb dating of zircons as well as new sm nd and rb sr data indicate that the intrusive ages of both mafic and felsic orthogneisses are in the range 1780 1740 ma strangways orogeny these rocks had initial nd values of 0 to 3 and depleted mantle model ages of 2 5 2 1 ga and they intruded supracrustal rocks which are now preserved as paragneisses with initial nd of about 15 sm nd and rb sr whole rock isotope data indicate that the hornblende rich amphibolitic gneisses and mylonites in the harts range detachment zone ding and james 1989 were equilibrated at 1473 ma 133 when the rocks experienced hydration isotopic homogenisation and thrust faulting this is the anmatjira event described elsewhere in the arunta inlier and is a predominantly structural influence with thrust faults and hydrous fluid flux accordingly the record of this event by radiogenic geochronometers has been diffuse a problem also exacerbated by the probable influence on these rocks of least one more subsequent lower temperature amphibolite facies metamorphic event in spite of the indications of 1470 ma isotopic homogenisation of amphibolites in the harts ranges rb sr isotopic analyses of all minerals and 40ar 39ar from hornblendes yield ages in the range 450 300 ma using the sm nd system a few garnet hornblende pairs give 1400 1250 ma ages but several of these pairs also yield early palaeozoic ages these data suggest that the central province of the eastern arunta inlier also experienced an early palaeozoic thermal event having cooled from temperatures 550 c during and immediately before the carboniferous alice springs orogeny in the southern province south of the illogwa shear zone micas record mesoproterozoic ages 1500 1250 ma for the rb sr k ar and ar ar systems equivalent to the whole rock ages obtained from the central province to the north of the illogwa shear zone clearly the exposed southern basement cooled to 350 c presumably as a result of uplift and exhumation during the anmatjira event when basement now exposed in the central province remained at depth undergoing one or more additional amphibolite facies events the spectacular contrast in cooling histories across the illogwa shear zone emphasises that this is an important crustal scale tectonic structure

waves of accelerated motion in a glacier approaching surge the mini surges of variegated glacier alaska u s a periods of dramatically accelerated motion in which the flow velocity increases suddenly from about 55 cm d to a peak of 100 300 cm d and then decreases gradually over the course of a day occurred repeatedly during june and july 1978 81 in variegated glacier alaska a surging type glacier that surged in 1982 83 these mini surges appear to be related mechanistically to the main surge the flow velocity peak propagates down glacier as a wave at a speed of about 0 3 km h over a reach of about 6 km in length it is accompanied by a propagating pressure wave in the basal water system of the glacier in which after a preliminary drop the pressure rises rapidly to a level greater than the ice overburden pressure at the glacier bed and then drops gradually over a period of 1 2 d usually reaching a new low for the summer the peak velocity is accompanied by a peak of high seismic activity due to widespread fresh crevassing it is also accompanied by a rapid uplift of the glacier surface amounting to 6 11 cm which then relaxes over a period of 1 2 d maximum uplift rate coincides with the peak in flow velocity the peak in accumulated uplift lags behind the velocity peak by 2 h the uplift is mainly due to basal cavitation driven by the high basal water pressure although the strain wave associated with the mini surge motion can also contribute basal cavitation is probably responsible for the pulse of high turbidity that appears in the terminal outflow stream in association with each mini surge in the down glacier reach where the mini surge waves are attenuating the observed strain wave corresponds to what is expected for the propagating pulse in flow velocity but in the reach of maximum mini surge motion the strain wave has a form quite different possibly related to special features in the mini surge initiation process from that point up stream the flow acceleration in the mini surges is due to enhanced basal sliding caused by the high basal water pressure and the consequent reduction of bed friction a preliminary velocity increase shortly before the pressure wave arrives is caused by the forward shove that the main accelerated mass exerts on the ice ahead of it and the resulting preliminary basal cavitation causes the drop in water pressure shortly before the pressure wave arrives the mini surge wave propagation is controlled by the propagation of the water pressure wave in the basal water conduit system the propagation characteristics result from a longitudinal gradient up glacier increase in hydraulic conductivity of the basal water system in response to the up glacier increase of the basal water pressure in the mini surge wave the mini surge waves are initiated in a succession of areas situated generally progressively up glacier during the course of the summer season in these areas presumably melt water that has accumulated in subglacial reservoirs is released suddenly into the basal water system immediately below generating a pressure rise that propagates down stream from there relationships of the mini surges to the main surge are seen in the role of high basal water pressure in causing the rapid glacier motion in both phenomena in the pulse propagation features of both and in the high outflow turbidity associated with both the mini surges of variegated glacier have a strong resemblance to movement and uplift events observed in unteraargletscher and findelengletscher switzerland this bears on the question whether the mini surges are a particular characteristic of surge type glaciers prior to surge

geometric evolution and ice dynamics during a surge of bakaninbreen svalbard bakaninbreen svalbard started surging in 1985 and developed a steep surge front where fast moving ice impinged on stagnant non surging ice this front which was 20 25 m high in 1985 became a steep and heavily crevassed fcature about 60 m high the surge continued through 1986 95 annual surge front propagation rate was 1 0 1 8 km a 1 during 1985 89 this rate dropped considerably during 1989 95 and the front became less steep front propagation occurred largely by longitudinal compression and vertical extension of the ice and the effects of over riding appear minor ice velocities were slowe than the average propagation rate of the front the surge affected bakanin breen in four zones upper region where extensiv e flow fast propagation rates and negative vertical strain occurred resulting in widespread crevassing and stranded blocks tens of metres above the post surge ice surface 2 mid glacier region where initial strong compression was associated with ice thickening which started before the arrival of the surge front horizontal strain rates were very low but vertical strain rates were up to 300 mm d 1 as the front passed the horizontal velocity increased and about 500 m behind it became extensive negative vertical strain and ice down draw occurred as ice vclocities dropped 3 surge front where ice velocity w as high but vertical strain remained positive associated with compression 4 lower region below the front where only compression occurred resulting in the formation of a fore bulge a thickening of the ice of up to 50 m above pre surge levels the fore bulge affected the whole 1 7 km below the now halted surge front the glacier has not advanced ba kaninbreen s surge was characterized by a long active phase approximately 10 years low ice velocities and low basal shear stresses compared to glaciers in lower latitudes and an indistinet surge termination

multiphase formation of superimposed ice during a mass balance year at a maritime high arctic glacier meteorological and snow temperature data from midtre lovenbreen spitsbergen svalbard indicate two distinct annual phases of rapid snowpack warming and superimposed ice formation in 1998 99 short periods of positive air temperatures in early winter lasting up to 36 hours and often coinciding with rainfall caused rapid glacier wide melting percolating water froze to form superimposed ice on the lower half of the glacier and wetted refrozen snow and ice lenses at higher altitudes the second period of superimposed ice formation commenced in may june 1999 and continued for 5 weeks at low altitudes and throughout the summer at high altitudes these observations at midtre lovenbreen are typical of spitsbergen glaciers and reflect the unique climatology of the region they contrast with those from glaciers in more continental climatic settings where superimposed ice formation is confined to a single period during summer there are significant implications for glacier mass balance with superimposed ice locally comprising up to 20 of winter balances and accounting for 16 25 of the annual accumulation since projected climatic warming is greatest during the winter months in arctic regions superimposed ice may become an increasingly important component of the winter and potentially the net balance of spitsbergen glaciers

massive destabilization of an arctic ice cap abstract ice caps that are mostly frozen at the bedrock ice interface are thought to be stable and respond slowly to changes in climate we use remote sensing to measure velocity and thickness changes that occur when the margin of the largely cold based vavilov ice cap in the russian high arctic advances over weak marine sediments we show that cold based to polythermal glacier systems with no previous history of surging may evolve with unexpected and unprecedented speed when their basal boundary conditions change resulting in very large dynamic ice mass losses an increase in annual mass loss by a factor of 100 over a few years we question the future long term stability of cold and polythermal polar ice caps many of which terminate in marine waters as the climate becomes warmer and wetter in the polar regions

is there a single surge mechanism contrasts in dynamics between glacier surges in svalbard and other regions 1 during the 1990s monacobreen a 40 km long tidewater glacier in svalbard underwent a major surge we mapped the surge dynamics using ers synthetic aperture radar images differential dual azimuth interferometry and intensity correlation tracking a series of 11 three dimensional 3 d velocity maps covering the period 1991 1997 show a months long initiation and years long termination to the surge with no indication of a surge front travelling downglacier during the surge the front of the glacier advanced 2 km the velocity and derived strain rate increased by more than an order of magnitude and maximum ice flow rates measured during 1994 were 5 m d 1 the spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed we combine these results with those published in the literature to construct a typical svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions especially those of variegated glacier in alaska the strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms

how do glaciers surge a review the quasi periodic oscillations between normal and fast motion exhibited by surge type glaciers provide the best observational opportunity to determine limiting conditions that allow fast motion the measurements from variegated glacier prove that its surge motion is caused by rapid sliding induced by high water pressure this arises from a major restructuring of the basal hydraulic system which impedes water discharge prior to and during surge although the evolving glacier geometry and stress distribution play a principal enabling role the seasonal timing of two distinct surge pulses each initiated in winter and terminated in summer indicates a major influence from variable external water inputs this influence is not considered in existing surge models and should promote caution in the use of data from temperate and subpolar surge type glaciers to deduce surge potential in polar ice masses the spatial spreading of surge motion from a zone of local initiation occurs by stress redistribution which may spread the surging zone rapidly upglacier or downglacier inside a region of active ice and by mass redistribution with compressional thickening at the surge front which enables down glacier propagation into less active ice the data from other surge type glaciers including the extensive data from medvezhiy glacier are not inconsistent with the above processes but are inadequate to establish whether completely different mechanisms operate in some surges the way by which water accumulates and produces fast sliding is not established in detail for any surge type glacier and may be different on different glaciers depending for example on the presence or absence of unconsolidated debris between the ice and rock

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

short term velocity variations and sliding sensitivity of a slowly surging glacier we use daily surface velocities measured over several weeks in 2007 and 2008 on a slowly surging glacier in yukon canada to examine the ordinary melt season dynamics in the context of the ongoing surge horizontal velocities within and just below the 1 5 km long zone of fastest flow where the surge is occurring are often correlated during intervals of low melt this correlation breaks down during melt events with the lower reaches of the fast flow zone responding first velocity variability in this lower reach is most highly correlated with melt velocities above and below appear to respond at least as strongly to the velocity variations of this reach as to local melt gps height records are suggestive of ice bed separation occurring in the fast flow zone but not below it pointing to a hydrological cause for the short term flow variability in the surging region independent velocity measurements over 6 years show a maximum july flow anomaly coincident with the location most responsive to melt results from a simple model of dashpots and frictional elements lend support to the hypothesis that this zone partly drives the dynamics of the ice above and below it we speculate that the slow surge may enhance glacier sensitivity to melt season processes including short term summer sliding events

origin of hydrothermal cuznpb mineralisation in the olary block south australia evidence from fluid inclusions and sulphur isotopes abstract styles of sulphidic mineralisation recognised in the olary block south australia include disseminated to massive stratiform and stratabound occurrences as well as post peak metamorphic vein type mineralisation corresponding to the range of deposit types in the adjacent broken hill block however it is still unclear as to whether the epigenetic veins are genetically related to stratabound mineralisation in either of these two portions of the meso to palaeoproterozoic willyama inliers a fluid inclusion and sulphur isotope study was undertaken to examine the nature of fluids associated with epigenetic mineralisation in the olary block to determine possible genetic relationships between sulphides in epigenetic veins and stratabound mineralisation and to evaluate possible sources of sulphur in each of these occurrences fluid inclusions in epigenetic assemblages can be classified in general terms of co 2 rich ch 4 rich nacl rich and h 2 o rich types dense and moderately saline co 2 and ch 4 rich fluids prevailed during or shortly after peak metamorphism possibly as a result of metamorphic decarbonatisation and dehydration reactions at deeper levels as well as oxidation of graphite during retrograde metamorphism in shallower levels due to rehydration reactions and infiltration of metamorphic fluids from deep seated hydrothermal reservoirs during retrogression and uplift these fluids became increasingly saline and thus suitable to transport significant amounts of metals in solution near surface derived fluids entered fluid conduits during further uplift and cooling resulting in compositional dilution of the brines and decreasing fluid temperatures sulphur isotopic signatures in stratabound and epigenetic mineralisation in the olary block suggest a continuous supply of hydrothermal sulphur bearing fluids from a deep seated reservoir large scale leaching of volcaniclastics and other sedimentary rocks or convective homogenisation of a mixed source e g evaporitic or seawater sulphate and igneous sulphides resulted in relatively uniform 34 s values of 5 to 10 in the hydrothermal fluids mixing with sedimentary sulphur in stratabound occurrences is indicated by lighter sulphur isotopic compositions 34 s 15 6 in sulphides associated with carbonaceous pelites the distinct sulphur isotopic signature of epigenetic vein mineralisation in the olary block 34 s inpyrrhotite between 5 8 and 7 6 precludes simple derivation from pre existing deposits by remobilisation processes it rather implies extraction from the same source region at a later stage possibly induced by tectonic pumping and hydrothermal venting of a deep seated crustal reservoir

controls on glacier surging in svalbard the geographical distribution of surge type glaciers worldwide displays a remarkably non random pattern surge type glaciers tend to be concentrated in certain glacierized areas and to be completely absent in others this observation suggests that special conditions are required for surges to occur however the factors controlling the spatial occurrence of surge type behaviour are not known to investigate this problem we performed probability statistical analysis on a sample population of 615 glaciers in svalbard the probability that a glacier in the sample population is surge type is 36 4 within the sampled area there is a spatial variation in the concentration of surge type glaciers several geometric and environmental factors associated with glaciers in the sample population were measured and tested to determine if they are related to the probability of surging of the geometric factors tested length slope elevation orientation and presence or absence of tributaries only glacier length is related to surging with surge probability increasing with increasing length elevated probabilities of surging were also found for glaciers associated with sedimentary subglacial rocks and sub polar thermal regimes the distributions of related factors were used to predict the spatial distribution of surge type glaciers however in each case the individual factors were unable to reproduce the observed pattern of surge type glacier distribution

metamorphism in the olary block south australia compression with cooling in a proterozoic fold belt the sedimentary and igneous rocks comprising the lower proterozoic olary block south australia were deformed and meta morphosed during the mid proterozoic olar ian orogeny the area is divided into three zones on the basis of assemblages in metapelitic rocks higher grade conditions occurring in the south east mineral assemblages developed during peak metamorphism which accom panied recumbent folding include andalusite in zones i and i1 and sillimanite in zone 111 upright folding and overprinting of mineral assemblages occurred during further com pression the new mineral assemblages includ ing kyanite in zone i1 and kyanite and sillimanite in zone 111 the timing relationships of the aluminosilicate polymorphs together with the peak metamorphic and overprinting parageneses imply an anticlockwise p t path for the olarian orogeny pressure increasing with cooling from the metamorphic peak

a 300 year surge history of the drangajokull ice cap northwest iceland and its maximum during the little ice age over the last 300 years each of the three surge type outlet glaciers of the drangajokull ice cap in northwest iceland has surged 2 4 times there is valuable historical information available on the surge frequencies since the little ice age lia maximum because of the proximity of the surging outlets reykjarfjar arjokull leirufjar arjokull and kaldalonsjokull to farms and pastures and monitoring of these glaciers since 1931 we have reconstructed the surge history of the drangajokull ice cap based on geomorphological mapping sedimentological studies and review of historical records geomorphological mapping of the glacier forefields reveals twice as many end moraines as previously recognized this indicates a higher surge interval than earlier perceived a clear relationship between the surge interval and climate cannot be established surges were observed more frequently during the 19th century and the earliest 20th century compared with the relatively cool 18th century and the late 20th century

th u pb monazite ages from al mg rich metapelites rauer group east antarctica the age of high temperature granulite facies metamorphism 800 850 c in the rauer group prydz bay east antarctica is relevant for establishing the metamorphic and temporal architecture of the prydz bay mobile belt monazites within al mg rich granulite facies metapelites give an overall tanh estimated pan african age of 511 4 ma 2r using in situ electron microprobe based th u pb chronology consistent with existing u pb zircon geochronology from the rauer group and prydz bay monazite occurs primarily within cordierite bearing coronae and symplectic min eral reaction textures and also within biotite pan african granulite facies metamorphism is preferred as responsible for the development of the cordierite bearing microstructures and probably peak coarse grained assemblages constrained using an integrated geologic geochronologic and metamorphic framework thus pan african granulite facies metamorphism affected the rauer group within the prydz bay mobile belt moreover integrated monazite geochronology may be used to decipher the temporal metamorphic histories of potentially complex high temperature terrains

late holocene expansion of eastern larch larix laricina du roi k koch in northwestern quebec the holocene expansion of eastern larch larix laricina du roi k koch at the edge of its geographical range in northwestern quebec was reconstructed using pollen and macrofossils from peat deposits becauselarixis a poor pollen producer the total pollen sum of 300 500 grains per spectrum was supplied by an additional survey of 2000 grains however the use of 2000 pollen counts did not give a betterlarixrecord the combination of both pollen and macrofossil analyses offered greater opportunities to estimate the time of arrival of eastern larch at the edge of its distributional range along the study transect eastern larch established east of 75 w long before 2000 yr b p but not sooner than 5000 yr b p whereas it arrived much later after 1500 yr b p in most sites west of 75 w within a migration corridor around 57 45 n the macrofossil record is completely different between the eastern sites with high frequencies and densities and the western sites where larch occurs sporadically with few remains only concentrated in the upper part of the peat profiles the colonization pattern of eastern larch was patchy in time and space as suggested by the available macrofossil records present distributional pattern in the area and age structure of extant populations the establishment of disjunct larch populations in the westernmost sites most likely proceeded from long distance transport the spatial temporal pattern of eastern larch west of 74 w may have been influenced by the site conditions associated with late deglaciation in central northern quebec

controls on the distribution of surge type glaciers in svalbard we analyzed the possible controls on the distribution of surge type glaciers in svalbard using multivariate logit models including 504 glaciers and a large number of glacial and geological attributes specifically we examined the potential effect of geological boundaries mass balance conditions and thermal regime on surging it was found that long glaciers with relatively steep slopes overlying young fine grained sedimentary lithologies with orientations in a broad arc clockwise from northwest to southeast are most likely to be of surge type no relation between lithological boundaries and surge potential could be established possible explanations for length being conducive to surging are transport distance related substrate properties distance related attenuation of longitudinal stresses and the possible relation between thermal regime and glacier size analysis of glaciers with recorded radioecho sounding reveals that a polythermal regime accumulation area ratios close to balance and a large elevation span increase the surge potential the logit models also enabled us to detect 19 new surge type glaciers to reclassify six glaciers as normal and to identify unusual surge type glaciers our model results suggest that a polythermal regime and fine grained potentially deformable beds are conducive to the surge potential of svalbard glaciers

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

svalbard surge dynamics derived from geometric changes geometric changes on a sample of svalbard glaciers were studied using subtraction of repeat digital terrain models to determine early surge stage dynamics changes in surface features were also analyzed a number of new surges were found for glaciers not known to have surged previously the surge development could be followed through three stages of which the first two had not been previously described in svalbard the first two stages are mainly identified from glacier thickness changes and showed little visual evidence in stage 1 initial surface lowering was found in the upper part of the glacier followed by a thickening further down glacier in stage 2 stage 3 represents the period of well developed surge dynamics that is usually reported some surges ceased at stage 2 as a partial surge and never developed into a fully active surge these partial surges could be misinterpreted as rapid response to climate change the results of this study further support previous findings that the majority of svalbard glaciers are of surge type data archives have greatly facilitated the search for signs of surges and the recapturing of the course of events in this paper we present a number of new observations of svalbard surge type behaviour based on evidence from geometric changes and complemented by observations of newly developed crevasse fields two criteria are used to identify a surge either individually or in combination 1 mass displacement from the upper to the lower glacier part and 2 presence of new crevasse fields which indicate rapid or strong changes in stresses the aims of our study are to contribute to a more complementary picture and better understanding of the transition from build up stage via initial surge dynamics to the previously described mature stage where the changes are more pronounced we also investi gate whether all surges develop fully the implications of partial surges for interpretation of surface lowering related to varying climate conditions and finally the large spread in estimates for the number of surge type glaciers in svalbard

quiescent phase dynamics and surge history of a polythermal glacier hessbreen svalbard hessbreen is a 5 km 2 polythermal glacier in southern spitsbergen it is believed to have surged at the end of the 19th century and another surge started in 1969 not in 1972 as earlier studies suggested the surge was probably triggered in the middle section of the glacier and affected the upper part approximately 4 years before including the whole glacier present velocities are low increasing from 0 3 m a 1 at the snout to 4 8 m a 1 above the equilibrium line a distinct velocity reduction occurs where the glacier narrows this suggests the velocities here are affected by the cold marginal and frontal ice large seasonal variations with summer velocities of more than twice the winter velocities in the middle part of the glacier indicate a seasonal change in the drainage system in this area in the lower part there is no apparent sliding the balance flux estimate indicates that the actual ice flux is only about 50 of that required for steady state so hessbreen appears to be building up in the accumulation area the surge duration is now estimated to be 8 years

volcanoes and climate the triggering of preboreal jokulhlaups in iceland the early holocene 12 8 2 cal ka deglaciation and pulsed warming was associated in iceland with two major generations of jokulhlaups around the vatna ice cap vatnajokull at ca 11 4 11 2 cal ka and ca 10 4 9 9 cal ka and major tephra emissions from the grimsvotn and bar arbunga subglacial volcanoes the earliest flood events were recorded inland during the middle younger dryas and their deposits were overlain by the early preboreal vedde ash 11 8 cal ka the first holocene flood events ca 11 4 11 2 cal ka are issued from a glacial advance the second and major set of floods was partly driven by the erdalen cold events and advances 10 1 9 7 10be ka initially issued from the bar arbunga 10 4 10 1 9 9 ka and grimsvotn volcanoes saksunarvatn tephra complex ca 10 2 9 9 cal ka these floods were also fed by the residual glacio isostatic depressions below the vatnajokull that enabled the storage of meltwaters in large subglacial lakes or aquifers until ca 9 3 cal ka this storage was enhanced by ice damming and permafrost especially during the twinned erdalen events due to the glacio isostatic rebound the general slope was nearly flat and the valley was partly filled with sediments until ca 10 8 cal ka temporary lacustrine deposits in this valley resulted from the very broad splay of waters as for the ca 11 2 cal ka and ca 10 1 9 9 cal ka flood due to regional permafrost these floods had a potential duration of several months as they were mostly fed by climate driven meltwater the maximal volume evacuated by these events did not greatly exceed 1 106 m3 s 1 from the flood affected transverse profile of the valleys that remain partly filled with sediments

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

threefold increase in marine terminating outlet glacier retreat rates across the atlantic arctic 1992 2010 accelerated discharge through marine terminating outlet glaciers has been a key component of the rapid mass loss from arctic glaciers since the 1990s however glacier retreat and its climatic controls have not been assessed at the pan arctic scale consequently the spatial and temporal variability in the magnitude of retreat and the possible drivers are uncertain here we use remotely sensed data acquired over 273 outlet glaciers located across the entire atlantic arctic i e areas potentially influenced by north atlantic climate and or ocean conditions specifically greenland novaya zemlya franz josef land and svalbard to demonstrate high magnitude accelerating and near ubiquitous retreat between 1992 and 2010 overall mean retreat rates increased by a factor of 3 5 between 1992 and 2000 30 5 m a 1 and 2000 10 105 8 m a 1 with 97 of the study glaciers retreating during the latter period the retreat was greatest in northern western and south eastern greenland and also increased substantially on the barents sea coast of novaya zemlya glacier retreat showed no significant or consistent relationship with summer air temperatures at decadal timescales the rate of frontal position change showed a significant but weak correlation with changes in sea ice concentrations we highlight large variations in retreat rates within regions and suggest that fjord topography plays an important role we conclude that marine terminating arctic outlet glaciers show a common response of rapid and accelerating retreat at decadal timescales

microprobe monazite geochronology putting absolute time into microstructural analysis abstract high resolution compositional mapping and dating of monazite on the electron microprobe is a powerful addition to microstructural analysis and an increasingly important tool for tectonic analysis microprobe monazite geochronology can be an efficient reconnaissance tool for evaluating metamorphic and deformational age domains but more importantly its in situ nature and high spatial resolution offer an entirely new level of structurally and texturally specific geochronologic data that can be used to put absolute time constraints on p t d paths constrain the rates of metamorphic and deformational processes and provide new links between metamorphism and deformation microprobe geochronology is particularly applicable to three persistent microstructural microtextural problem areas 1 constraining the chronology of metamorphic assemblages 2 constraining the timing of deformational fabrics and 3 interpreting other geochronological results although some monazite generations can be directly tied to metamorphism or deformation at present the most common constraints rely on monazite inclusion relations in porphyroblasts that in turn can be tied to the deformation and or metamorphic history microprobe mapping and dating allow geochronology to be incorporated into the routine microstructural analytical process resulting in a new level of integration of time t into p t d histories

characterizing the may 2015 karayaylak glacier surge in the eastern pamir plateau using remote sensing we investigate an internal surge of karayaylak glacier which was reported by the media in may 2015 to differentiate the may 2015 glacier surge from other glacier advances we surveyed changes in velocity crevasses and glacier area using landsat 8 oli l1t zy 1 02c and gaofen 1 images from october 2014 to july 2015 the velocity measured by automatic feature extraction and tracking during the active phase was 10 100 times the velocity during the quiescent phase with a maximum of 20 2 0 9 m d 1 mean standard error from 8 to 15 may 2015 in the west branch of the glacier the surge initiation and termination took place from 13 april to 16 june 2015 ice in the west branch length 7 km area 6 8 km 2 of karayaylak glacier accelerated down to the east branch leading to the development of crevasses and ice covering an additional 0 1 km 2 of summer pasture on the northwestern side however we detected no advance of the glacier s terminus

dynamics of tidewater surge type glaciers in northwest svalbard the evolution of ice dynamics through surges of four tidewater terminating glaciers in northwest svalbard is investigated by remote sensing a 20 year time series of glacier surface flow speeds and frontal positions is presented covering the recent surges of monacobreen comfortlessbreen blomstrandbreen and fjortende julibreen surface flow speeds were derived using feature tracking between pairs of ers sar and alos palsar images while frontal positions were taken from the same imagery as well as more frequent but lower spatial resolution envisat wide swath mode images during all four surges increased ice flow caused the tidewater margin to advance while the calving flux was initially reduced to near zero due to compressive stresses limiting crevasse propagation as ice speed decreased the terminus continued to advance until the glacier s speed had returned to its pre surge flow rate only at this time did the terminus start to retreat and peak iceberg calving flux was established we conclude that terminus advance closely tracks glacier speed up that there is little mass loss through calving during the most active phase of the surge and that seasonal cycles of terminus positions diminish during the active surge phase

how much do we really know about glacier surging some of the ideas about glacier surging are considered mainly but not entirely in the light of observations of temperate glaciers in alaska u s a made within the last 15 years climate has an influence on surge recurrence interval climate and weather also affect surge initiation termination and magnitude regional studies lead to the speculation that subglacial till plays a key role in surging and it has been found under all surge type glaciers studied so far including black rapids and variegated glaciers alaska in most of the glaciers studied till deformation processes dominate the motion in quiescence the linked cavity model of surge triggering and rapid motion is not consistent with these observations but the limited coverage of the observations does not rule it out under parts of the glaciers studied the till observations in alaska raise old questions about the interaction between till and the hydraulic systems of temperate glaciers the role of stored water which observations show to be active even in winter on black rapids glacier is noted

on the relationship between the formation of shear zones and the form of the flow law for rocks undergoing dynamic recrystallization abstract the formation and maintenance of shear zones in rocks at high temperatures when viscous flow takes place at constant volume requires strain weakening several processes can lead to a strain weakening characteristic in the flow of such rocks to high strains but conventional experimental rock mechanics techniques cannot normally provide high quality mechanical data to high strains recent experimental data for calcite marble have demonstrated strain weakening accompanied by dynamic recrystallization a power law with strain exponent r can be used to describe the dependence of the flow stress on strain together with the conventional description of the dependence of strain rate on stress described by a stress exponent n the stable localization of strain into shear zones is favoured by more negative values of r e g r 0 8 and more positive values of n e g n 5 to 7 a further important factor is the critical strain e0 for the onset of recrystallization and hence strain weakening shear zone formation is favoured by smaller values for e0 shear zone formation weakens the crustal section in which they occur but the amount of weakening may not be great perhaps no more than 50 of the previous steady state flow stress certain rock types such as mafic igneous rocks may through their mechanical properties be more susceptible to shear zone formation than others such as mica schists it is emphasized that the analysis presented is based upon a strain dependent flow law that describes single phase dynamic recrystallization by grain boundary migration that leads to enhanced recovery without any change in deformation mechanism no consideration is given to possibly important effects arising from the activation of grain size sensitive flow or to potential weakening effects arising from syntectonic metamorphic reactions

surges of outlet glaciers from the drangajokull ice cap northwest iceland abstract surface elevation and volume changes of the drangajokull surge type glaciers reykjarfjar arjokull and leirufjar arjokull were studied by comparing digital elevation models that pre date and post date their most recent surges annual glacier frontal measurements were used to estimate average ice velocities during the last surge of the glaciers the observations show a distinct ice discharge most of which was from the upper reservoir areas down to the receiving areas during the surges the surface draw down in the reservoir areas was usually 10 30 m during the surges while the thickening of the receiving areas was significantly more variable on the order of 10 120 m despite a negative geodetic net mass balance derived from the digital elevation models the reservoir areas have been gaining mass since the surge terminations this surface thickening along with considerable ablation of the receiving areas will most likely return the glacier surface profiles to the pre surge stage our results indicate that a greatest surface thinning in the upper reservoir areas of drangajokull rather than proximal to the equilibrium line during vatnajokull surges and b development of drangajokull surges that resembles svalbard surge type glaciers rather than vatnajokull surge type glaciers the contrasting surge characteristics could be explained by differences in glacier geometry topography and substratum of the drangajokull and vatnajokull surge type glaciers

the 2008 09 surge of central yulinchuan glacier northern tibetan plateau as monitored by remote sensing the 2008 09 surge of central yulinchuan glacier cyg on the northwestern slope of muztag mountain tibetan plateau is studied based on satellite remote sensing the widely used cross correlation feature tracking method was used to collect satellite image control points and validate their geometric accuracies as well as to derive glacier surface velocity changes in glacier length and area were also retrieved results show that the surge of cyg initiated in may 2008 and terminated in july 2009 two diffluent glacier termini advanced 590 26 m 5 1 0 2 of the 2004 length and 182 26 m 1 8 0 3 respectively and glacier area increased by similar to 1 41 0 11 km 2 4 6 0 4 of the 2004 area during this period the most significant surge period was october 2008 to march 2009 when most of the terminus advances and area increases occurred the glacier surface drastically crevassed during this time as much as 1657 297 m of horizontal surface displacements were produced by surge ice and maximum surface speed reached 13 1 5 m d 1 results of transverse and longitudinal velocity profiles revealed two surge waves during this surge of cyg

visible and near infrared digital images for determination of ice velocities and surface elevation during a surge on osbornebreen a tidewater glacier in svalbard

the structural geometric and volumetric changes of a polythermal arctic glacier during a surge cycle comfortlessbreen svalbard various parameters of the most recent surge of the polythermal glacier comfortlessbreen in northwest svalbard have been assessed through a combination of remote sensing and ground observations analysis of a digital elevation model time series shows a marked change in the geometry of the glacier from quiescence 1990 and earlier into the late surge phase 2009 the transfer of 0 74 km3 of ice caused up to 80 m of surface drawdown in the reservoir area above the equilibrium line whilst ice built up in a spatially concentrated manner in the receiving zone below the equilibrium line a ramp of ice c 100 m above quiescent level developed in the lower reaches of the glacier late in the surge also in the lower reaches of the glacier structures attributable to the passage of a kinematic wave are identified and the migration of a surge front on the glacier is thus inferred in a conceptual model we consider that a bend in the valley in which the glacier resides and convergence with tributary glaciers to be significant factors in the style of surge evolution their flow restrictive interference results in slow initial mass transfer and the growth of a surge front within 3 4 km of the terminus copyright 2015 john wiley sons ltd

three dimensional topographic mapping with aster stereo data in rugged topography digital elevation models dems were generated from a stereo pair using the advanced spaceborne thermal emission and reflection radiometer aster backward and nadir images with 27 7 spl deg intersection angles b h 0 6 over a high relief area of the canadian rocky mountains fifteen ground control points were a good compromise to compute the stereo bundle adjustment when they are only 25 30 m precise to avoid their error propagation in the modeling it enabled to keep accuracy on the order of one pixel 15 m dem accuracy was then evaluated along the full process and as a function of different parameters applying the calibration of charge coupled devices in order to reduce the striping effects improves the dem accuracy by a factor of 10 the major problems in the image matching were the clouds snow lakes and occluded shadowed areas which generated mismatched areas and artificial relief in the lakes 1000 2000 m during the correlation process and the automatic interpolation method postprocessing the dem with semiautomatic three dimensional tools improved its accuracy by a factor of 10 the final results le68 and le90 of 28 and 51 m respectively were obtained with the interactive correction of lake elevations but without taking into account the large mismatched areas which were specific to this challenging mountainous study site

petrology and geochemistry of plagiogranite in the canyon mountain ophiolite oregon plagiogranites in the canyon mountain ophiolite oregon include a wide range of rock types ranging from diorite to trondhjemite the plagiogranites are mostly concentrated as an intrusive sill swarm at the top of a section of gabbroic cumulates the plagiogranites are typically low in k2o and high in na2o and are enriched 10 20 times chondrites in ree and overlap with abundances in basic rocks from canyon mountain all samples of plagiogranite are relatively depleted in lree with more silicic samples characterized by a slightly lesser degree of lree depletion total ree content is not consistently correlated with contents of major and other trace elements

a 40ar 39ar laser probe study of micas from the sesia zone italian alps implications for metamorphic and deformation histories two samples from the eclogite micaschist complex emc and the seconda zona diorito kinzigitica iidk of the sesia zone have been studied using a high spatial resolution laser probe 40ar 39ar technique with the aim of investigating the complexities of argon behaviour in metamorphic rocks and comparing their thermal histories data from a single large phengite grain from the emc show a range of ages from mid jurassic to upper cretaceous these apparent age variations are spatially related to both location within the grain and to intragrain microstructure modelling of the data shows that the profile formed by the diffusion of an excess argon component into the grain parallel to the mica cleavage profile asymmetry is explained by temporal variations in microstructural development enabling excess argon to enter the grain at different times in different places the temperatures of the initiation of deformation and the possible time scales for the deformation can be calculated as a function of cooling rate all estimates suggest deformation at greenschist facies in accord with the observed retrograde mineral assemblage absolute temperature estimates for deformation vary by less than 22 c for different cooling rates of 10 and 30 c ma 1 but vary by 80 c with different estimates of diffusion parameters the duration of deformation was for at least 2 ma at 10 c ma 1 or 0 7 ma at 30 c ma 1 biotites from the iidk sample record a permian to upper cretaceous age range that correlates with grain size the smallest grain sizes yielding the youngest ages this relationship is best explained by a partial resetting of biotites during an alpine thermal event initiated not more than 70 ma ago modelling of these data suggest that the sample never exceeded 300 c during the alpine the profoundly different thermal histories of the two units the emc recrystallized at 550 c whilst the iidk remained below 300 c suggests that they may not have been juxtaposed until much later than the eclogite facies metamorphism

slow surge of trapridge glacier yukon territory canada 1 trapridge glacier a polythermal surge type glacier located in the st elias mountains yukon territory canada passed through a complete surge cycle between 1951 and 2005 air photos 1951 1981 and ground based optical surveys 1969 2005 are used to quantify the modifications in flow and geometry that occurred over this period yearly averaged flow records suggest that the active phase began 1980 and lasted until 2000 the average velocity in the central area of the glacier went from 16 m yr 1 in 1974 to 39 m yr 1 in 1980 it peaked at 42 m yr 1 in 1984 and remained above 25 m yr 1 until 2001 over that interval the flow decelerated by steps in 4 year pulses after a particularly vigorous acceleration in 1997 1999 the glacier gradually slowed to presurge velocities in 2005 the flow was less than 9 m yr 1 digital elevation models are generated by stereographic analysis of air photos for 1951 1970 1972 1977 and 1981 these models are updated annually using ground based survey data and a novel implementation of bayesian kriging over the course of the surge the front of active ice advanced 450 m and the glacier area increased by 10 with an associated thinning of the ice the previous surge of trapridge glacier starting before 1939 and ending before 1951 led to a terminus advance of 1 km comparison of the two surges suggests that the 1930s surge started with a slow progression similar to what we observed in the 1980s and 1990s and switched to a faster flow mode after 1941 this second phase was never attained in the recent surge probably owing to a lack of mass

timing and nature of fluid flow and alteration during mesoproterozoic shear zone formation olary domain south australia the development of shear zones at mid crustal levels in the proterozoic willyama supergroup was synchronous with widespread fluid flow resulting in albitization and calcsilicate alteration monazite dating of shear zone fabrics reveal that they formed at 1582 22 ma at the end of the olarian d3 deformational event and immediately prior to the emplacement of regional s type granites two stages of fluid flow are identified in the area first an albitizing event which involved the addition of na and loss of si k and fe and a second phase of calcsilicate alteration with additions of ca fe mg and si and removal of na fluid fluxes calculated for albitization and calcsilicate alteration were 5 56 109 to 1 02 1010 mol m 2 and 2 57 108 5 20 109 mol m 2 respectively these fluxes are consistent with estimates for fluid flow through mid crustal shear zones in other terranes the fluids associated with shearing and alteration are calculated to have 18o and d values ranging between 8 and 11 and 33 and 42 respectively and nd values between 2 24 and 8 11 our results indicate that fluids were derived from metamorphic dehydration of the willyama supergroup metasediments fluid generation occurred during prograde metamorphism of deeper crustal rocks at or near peak pressure conditions shear zones acted as conduits for major crustal fluid flow to shallow levels where peak metamorphic conditions had been attained earlier leading to the apparent retrograde fluid flow event thus the peak metamorphism conditions at upper and lower crustal levels were achieved at differing times prior to regional granite formation during the same orogenic cycle leading to the formation of retrograde mineral assemblages during shearing

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

identification of the scales of differential element mobility in a ductile fault zone two fundamentally different scales of element mobility have been identified in the upper amphibolite facies hunts brook fault zone of south central connecticut usa field relations mineral chemistry and 80 bulk rock analyses provide overwhelming evidence that the blastomylonitic schists and gneisses of the fault zone were derived from the enclosing granodioritic rope ferry orthogneiss two sample mass balance calculations between the rope ferry gneiss and fault rocks strongly suggest that the rope ferry gneiss was segregated into biotite rich schists and quartz plagioclase rich gneisses through the centimetre scale transfer of si al ca na ba and zr from schists to gneisses three and four sample mass balance calculations provide convincing evidence that al ca na and ba were lost and si and k gained by the entire fault zone both scales of metasomatism have been identified at two localities separated by 20 km implying that the metasomatic processes were pervasive throughout the fault zone from the mass balance calculations an apparent disparity in k mobility arises k appears to be gained by the entire fault zone but is immobile during the centimetre scale segregation this is because mass balance calculations can only detect differential element mobility differential element mobility requires that the mechanism of metasomatism produces chemical potential gradients therefore the identification of differentially mobile elements provides insight into the mechanisms of metasomatism the immobility of k during segregation of schists and gneisses implies that the segregation was not achieved through the extraction of partial melt however the element mobility is reconcilable with deformation driven metamorphic differentiation the gains of si and k and losses of ca na al and ba for the entire fault zone are also inconsistent with the intrusion or extraction of partial melt but may reflect the infiltration of a metasomatizing aqueous fluid

glacier surge mechanism 1982 1983 surge of variegated glacier alaska the hundredfold speedup in glacier motion in a surge of the kind the kind that took place in variegated glacier in 1982 1983 is caused by the buildup of high water pressure in the basal passageway system which is made possible by a fundamental and pervasive change in the geometry and water transport characteristics of this system the behavior of the glacier in surge has many remarkable features which can provide clues to a detailed theory of the surging process the surge mechanism is akin to a proposed mechanism of overthrust faulting

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

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

acceleration in thinning rate on western svalbard glaciers 1 geodetic measurements indicate that a number of glaciers in western svalbard ranging in size from 5 1000 km2 are losing mass at an accelerating rate the average thinning rate for midtre lovenbreen the glacier with the best data coverage has increased steadily since 1936 thinning rates for 2003 2005 are more than 4 times the average for the first measurement period 1936 1962 and are significantly greater than presented previously on slakbreen thinning rates for the latest measurement period 1990 2003 are more than 4 times that of the period 1961 1977 thinning of several glaciers along a previously measured airborne lidar profile in wedel jarls land has also increased doubling between the period 1990 1996 and 1996 2002 our results imply an increased sea level contribution from svalbard in addition the mass loss is an important influence on measured rates of rebound on western svalbard and should be factored into analysis of grace results

a new concept for glacial geological investigations of surges based on high arctic examples svalbard abstract svalbard is a key area for the investigation of glacial surges and almost two centuries worth of field observations exists from this region studies have shown that the course of a surge and the associated formation of landforms are strongly influenced by basinal factors and that the broad range of variables involved can hamper interpretations and comparisons based on a review of surges in svalbard a new concept for glacial geological investigations has been developed that combines ice flows ice front movements and morphostratigraphy the concept is comprised of the following four elements 1 classification based on the configuration and characteristics of the receiving basin 2 division of the surge cycle into six stages 3 guidelines for morphological mapping and 4 use of an allostratigraphic approach for interpreting ice front movements in this context delineation of the active phase is critical which include the history of terminus movements and four main categories of receiving basins are recognized these are a terrestrial basins with deformable substrates b terrestrial basins with poorly deformable substrates c shallow water basins and d deep water basins the ice front movement history is reconstructed by coupling information from the proglacial moraines syn surge the supraglacial moraines post surge and the associated traces of meltwater to the surge stages i vi this approach has revealed a critical relationship between the termination of the active phase and three morphological elements namely the maximum ice front position the maximum moraine extent and the youngest proglacial moraine which are unique for each of the basins a d the concept is thus a novel and more precise approach for mapping the active phase and the active phase duration as shown by the 12 year long surge of fridtjovbreen where stage i was 30 months inception stage ii was 54 months ice front advance stage iii was 12 months stillstand and stage iv was 48 months retreat during active flow the glacier has been in quiescent phase stages v vi since 2002

surge propagation constrained by a persistent subglacial conduit bakaninbreen paulabreen svalbard glacier surges tend to be initiated in relatively small regions then propagate down glacier up glacier and or across glacier the processes controlling patterns and rates of surge propagation however are incompletely understood in this paper we focus on patterns of surge propagation in two confluent glaciers in svalbard and examine possible causes one of these glaciers bakaninbreen surged in 1985 95 the surge propagated 7 km down glacier but did not cross the medial moraine onto the other glacier paulabreen when paulabreen surged between 2003 and 2005 the surge wave travelled several km down glacier but its lateral boundary stayed very close to the medial moraine the confluent glaciers formerly extended into a fjord and bathymetric mapping and historical observations show that an active subglacial conduit has existed between bakaninbreen and paulabreen since at least the early 20th century the existence of a persistent subglacial conduit below the medial moraine was confirmed when we entered and mapped a nye channel at the confluence of bakaninbreen and paulabreen we argue that the conduit acts as a barrier to surge propagation if pressurized water below one branch of the glacier system reaches the conduit water can be readily evacuated preventing its propagation into the other branch