on the characterization of glacier response by a single time scale glacier response to climate can be characterized by a single time scale when the glacier changes sufficiently slowly then the derivative of volume with respect to area defines a thickness scale similar to that of johannesson and others and the time scale follows from it our version of the time scale is different from theirs because it explicitly includes the effect of surface elevation on mass balance rate which can cause a major increase in the time scale or even lead to unstable response the time constant has a dual role controlling both the rate and magnitude of response to a given climate change data from south cascade glacier washington u s a illustrate the ideas some of the difficulty in obtaining accurate values for the thickness and time scales and the susceptibility of all response models to potentially large errors

on the imbalance and response time of glaciers in the european alps glaciers in the european alps rapidly lose mass to adapt to changes in climate conditions here we investigate the relationship and lag between climate forcing and geometric glacier response with a regional glacier evolution model accounting for ice dynamics the volume loss occurring as a result of the glacier climate imbalance increased over the early 21st century from about 35 in 2001 to 44 in 2010 this committed loss reduced to 40 by 2018 indicating that temperature increase was outweighing glacier retreat in the early 2000s but that the fast retreat effectively somewhat diminished glacier imbalances we analyze the lag in glacier response for each individual glacier and find mean response times of 50 28 years our findings indicate that the response time is primarily controlled by glacier slope and secondarily by elevation range and mass balance gradient rather than by glacier size

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

implications for the dynamic health of a glacier from comparison of conventional and reference surface balances conventional and reference surface mass balance data from gulkana and wolverine glaciers alaska usa are used to address the questions of how rapidly these glaciers are adjusting or responding to climate whether their responses are stable and whether the glaciers are likely to survive in today s climate instability means that a glacier will eventually vanish or at least become greatly reduced in volume if the climate stabilizes at its present state a simple non linear theory of response is presented for the analysis the response of gulkana glacier is characterized by a timescale of several decades but its stability and therefore its survival in today s climate are uncertain wolverine seems to be responding to climate more slowly on the timescale of one to several centuries its stability is also uncertain but a slower response time would make it more susceptible to climate changes

estimating response times of vadret da morteratsch vadret da palu briksdalsbreen and nigardsbreen from their length records length records of two pairs of glaciers are used to reconstruct the equilibrium line altitude ela and to estimate glacier response times the method is based on the assumption that neighbouring glaciers should be subject to the same climatic forcing and that differences in the length records are thus caused by differences in response times and climate sensitivities by means of a control method in which the difference between the reconstructed histories of the ela is minimized realistic response times are found the pairs of glaciers studied are i vadret da morteratsch and vadret da paluin the swiss alps and ii briksdalsbreen and nigardsbreen in southern norway in both cases the reconstructed ela histories of the individual glaciers are very similar in spite of the large differences in the length records short e folding response times are found for the steep glaciers 4 4 years for vadret da palii 5 0 years for briksdalsbreen for the larger glaciers with a more gentle slope the response times are substantially larger 33 0 years for vadret da morteratsch 34 8 years for nigardsbreen

six decades of glacier mass balance observations a review of the worldwide monitoring network glacier mass balance is the direct and undelayed response to atmospheric conditions and hence is among the essential variables required for climate system monitoring it has been recognized as the largest non steric contributor to the present rise in sea level six decades of annual mass balance data have been compiled and made easily available by the world glacier monitoring service and its predecessor organizations in total there have been 3480 annual mass balance measurements reported from 228 glaciers around the globe however the present dataset is strongly biased towards the northern hemisphere and europe and there are only 30 reference glaciers that have uninterrupted series going back to 1976 the available data from the six decades indicate a strong ice loss as early as the 1940s and 1950s followed by a moderate mass loss until the end of the 1970s and a subsequent acceleration that has lasted until now culminating in a mean overall ice loss of over 20 m w e for the period 1946 2006 in view of the discrepancy between the relevance of glacier mass balance data and the shortcomings of the available dataset it is strongly recommended to 1 continue the long term measurements 2 resume interrupted long term data series 3 replace vanishing glaciers by early starting replacement observations 4 extend the monitoring network to strategically important regions 5 validate calibrate and accordingly flag field measurements with geodetic methods and 6 make systematic use of remote sensing and geo informatics for assessment of the representativeness of the available data series for their entire mountain range and for the extrapolation to regions without in situ observations and 7 make all these data and related meta information available

identifying dynamically induced variability in glacier mass balance records abstractglacier mass balance provides a direct indicator of a glacier s relationship with local climate but internally generated variability in atmospheric circulation adds a significant degree of noise to mass balance time series making it difficult to correctly identify and interpret trends this study applies dynamical adjustment to seasonal mass balance records to identify and remove the component of variance in these time series that is associated with large scale circulation fluctuations dynamical adjustment refers here to a statistical method and not a glacier s dynamical response to climate mass balance records are investigated for three glaciers wolverine and gulkana in alaska and south cascade in washington north pacific sea level pressure and sea surface temperature fields perform comparably as predictors each explaining 50 60 of variance in winter balance and 25 35 in summer balance for south cascade and wolverine glaciers gulkana glacier located farther inland is less closely

recent changes 1991 2010 in glacier mass balance and air temperature in the european alps we estimate temperature sensitivity of observed mass balance for glaciers in the alps to compare with our earlier estimates from modelling we treat 1961 1990 as our reference period and compare mass balance for 1991 2010 with this reference period there are eight alpine glaciers with long enough records the mean mass balance for the eight glaciers is close to zero for the reference period very negative for 1991 2010 and highly negative in the exceptionally warm year 2003 mass balance changes are compared with 1991 2010 temperature anomalies to give an average temperature sensitivity of about 0 7 0 2 m w e a 1 k 1 for the eight glaciers there is considerable variation between individual glaciers with higher sensitivity for western glaciers and lower sensitivity for more eastern glaciers temperature sensitivity for the eight glaciers is strongly correlated with the standard deviation of observed mass balance which from earlier work is known to be correlated with winter balance the mean temperature sensitivity for observed mass balance is in reasonable agreement with values from earlier models but changes in glacier hypsometry during 1991 2010 may have further increased observed mass loss

downscaled precipitation applied in modelling of mass balance and the evolution of southeast vatnajokull iceland simulations of the post little ice age evolution of three outlet glaciers of southeast vatnajokull iceland skalafellsjokull heinabergsjokull and flaajokull are presented a coupled shallow ice approximation ice flow and degree day mass balance model is applied that is calibrated with a 14 year record of in situ mass balance measurements the measured mass balance cannot be realistically represented by constant horizontal and vertical precipitation gradients high resolution 1 km precipitation fields derived from downscaled orographic atmospheric circulation models of precipitation are required to capture the spatial variation of the winter mass balance the observed ice volume around 1890 15 30 larger than in 2000 can be simulated with 1 c lower temperatures and a 20 reduction in the annual precipitation relative to the reference climate period 1980 2000 the sensitivity of each glacier s annual balance to a change in temperature is 1 51 to 0 97 m w e a 1 c 1 and 0 16 to 0 65 m w e a 1 for a 10 increase in precipitation a steady state experiment applying a step increase in temperature of 2 c 3 c and precipitation increase of 10 results in a 50 80 90 decrease in ice volume

long term change of mass balance and the role of radiation the effect of climate change in the 20th century is investigated based on measured mass balance data annual winter and summer mass balances on claridenfirn switzerland since 1914 15 storglaciaren sweden since 1945 46 storbreen norway since 1948 49 glacier de sarennes france since 1948 49 and vernagtferner austria since 1965 66 are studied with air temperature at high altitude stations and the longest records of solar global radiation in europe the mean mass balances of these glaciers during the 20th century were mostly negative except for the first two decades the fluctuating mass balance reaches the minimum largest loss and maximum almost equilibrium around 1940 and 1980 respectively with a drastic loss in the last 15 years these variations are mostly steered by the variation in summer mass balance the change in the summer mass balance is determined to 72 by temperature and the remaining 28 by solar radiation during the colder period e g 1960 80 the reduction in solar radiation counteracted the warming trend due to the greenhouse effect since 1990 the greenhouse effect of terrestrial radiation and the global brightening effect of solar radiation have both been acting to accelerate the melt resulting in the unprecedented mass loss of the observational era the glacier mass balance during the 20th century clearly reacted towards temperature and solar radiation changes which reflected the greenhouse effect and aerosol and cloud variations

relating glacier mass balance to meteorological data using a seasonal sensitivity characteristic we propose to quantify the climate sensitivity of the mean specific balance b of a glacier by a seasonal sensitivity characteristic ssc the ssc gives the dependence of b on monthly anomalies in temperature and precipitation it is calculated from a mass balance model we show and discuss examples for franz josef glacier new zealand nigardsbreen norway hintereisferner austria peyto glacier canadian rockies abramov glacier kirghizstan and white glacier canadian arctic with regard to the climate sensitivity of b the sscs clearly show that summer temperature is the most important factor for glaciers in a dry climate for glaciers in a wetter climate spring and fall temperatures also make a significant contribution to the overall sensitivity the ssc is a 2 12 matrix multiplying it with monthly perturbations of temperature and precipitation for a particular year yields an estimate of the balance for that year we show that with this technique mass balance series can be re constructed from long meteorological records or from output of atmospheric models

modelling the evolution of vadret da morteratsch switzerland since the little ice age and into the future we use a 3 d higher order glacier flow model for vadret da morteratsch engadin switzerland to simulate its strong retreat since the end of the little ice age lia and to project its future disintegration under a warming climate the flow model coupled to a 2 d energy balance model is initialized with the known maximum glacier extent during the lia and subsequently forced with mean monthly precipitation and temperature records to correctly reproduce the observed retreat of the glacier front for the period 1864 2010 additional mass balance perturbations are required to account for uncertainties in the initial state the mass balance model and climate variations not captured by the ambient meteorological records changes in glacier volume and area are in good agreement with additional information from historical topographic maps under constant 2001 10 climate conditions a strong retreat and mass loss continue and vadret da morteratsch disconnects from its main tributary vadret pers before 2020 the future glacier evolution is analysed in detail to understand the timing and rate of retreat and to assess the role of ice dynamics assuming a linearly increasing warming of 3 c by 2100 only isolated and largely stagnant ice patches remain at high elevation

seismic characteristics and evolution of post rift igneous complexes and hydrothermal vents in the lingshui sag qiongdongnan basin northwestern south china sea abstract the study of morphology distribution and characteristics of igneous complexes has great significance to the understanding of magma plumbing processes geodynamics and tectonic evolution of continental margins previous studies concentrated partly on the magma rich rifted basins where the lateral magma transport mainly affects the igneous complexes connection and distribution however due to seismic wave shielding effects of the large shallow magmatic bodies the underlying igneous complexes and their corresponding magma plumbing systems in the magma poor rifted margins are still in debate in this study 2d 3d seismic data and well data are utilized to describe the morphology architecture and spatial temporal distribution of igneous complexes in the lingshui sag of the qiongdongnan basin northwestern south china sea margin the identified igneous complexes include 98 intrusive sills and feeder dykes beneath some of the isolated sills twenty six cone shaped mounds that overlie intruded sills through internal disturbed conduits were also described drilled well samples and seismic expressions suggest that these mounds are hydrothermal vents a uniform bottom mounds horizon of these vents suggests that they probably formed at the same time constrained by biostratigraphic data and sedimentation rate of underlying and overlying sedimentary layers the magma emplacement was dated to the middle miocene ca 14 6 ma most of the hydrothermal vents are distributed along the f2 fault zone and have direct linkage with the underlying sills while the large sill complexes that are connected with limited vents are mainly present above the hyperextended continental crust where the crust thins to 6 10 km the sills intruded into different layers from the lower oligocene to the lower miocene and the emplaced depth of sills is 1 2 6 3 km whether or not they feed any vents above unlike most of the large volume and laterally linked sills found in the magma rich rifted margins the scattered distribution of sills at different levels indicates that dykes probably play an important role in magma transport which might coexist with numerous polygonal or small faults and interference reflections this work highlights the critical role of basin structures in controlling the distribution of post rift igneous complexes in magma poor margins including thinned continental crust sedimentary thickness and faults

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

100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation thirty new 100 year records of glacier surface mass balance accumulation and melt in the swiss alps are presented the time series are based on a comprehensive set of field data and distributed modeling and provide insights into the glacier climate linkage considerable mass loss over the 20th century is evident for all glaciers but rates differ strongly glacier mass loss shows multidecadal variations and was particularly rapid in the 1940s and since the 1980s mass balance is significantly anticorrelated to the atlantic multidecadal oscillation amo index assumed to be linked to thermohaline ocean circulation we show that north atlantic variability had a recognizable impact on glacier changes in the swiss alps for at least 250 years citation huss m r hock a bauder and m funk 2010 100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation geophys res lett 37 l10501 doi

geodetic and direct mass balance measurements comparison and joint analysis this paper describes a new compilation of both direct and geodetic mass balance measurements develops a procedure to reduce diverse balance measurements over different time spans to common time spans and presents updated estimates of global average balance of small glaciers based on the enlarged compilation although geodetic measurements are fewer than direct measurements they cover four times as many balance years direct and geodetic measurements are unbiased with respect to one another but differences are often substantial the statistical procedure can be understood by imagining that an n year balance measurement is an average of a series of 1 year measurements the series is hypothetical but we can calculate the uncertainty of each of its elements if in addition to its measured average we can also estimate its standard deviation for this claim to be valid the annual series must be stationary and normally distributed with independent roughly uncorrelated elements for which there is reasonable evidence the need to know the standard deviation means that annual direct measurements from a nearby glacier or equally reliable information about variability are indispensable given this information the new methodology results in moderately more negative balances this is probably because tidewater glaciers are better represented in the geodetic data in any case the most recent published estimate of global average balance 0 8 1 0 mm a 1 of sea level equivalent for 2001 04 is now increased substantially to 1 1 1 4 mm a 1 for 2001 05

common climatic signal from glaciers in the european alps over the last 50 years conventional glacier wide mass balances are commonly used to study the effect of climate forcing on glacier melt unfortunately the glacier wide mass balances are also influenced by the glacier s dynamic response investigations on the effects of climate forcing on glaciers can be largely improved by analyzing point mass balances using a statistical model we have found that 52 of the year to year deviations in the point mass balances of six glaciers distributed across the entire european alps can be attributed to a common variability point mass balance changes reveal remarkable regional consistencies reaching 80 for glaciers less than 10 km apart compared to the steady state conditions of the 1962 1982 period the surface mass balance changes are 0 85 m water equivalent w e a 1 for 1983 2002 and 1 63 m w e a 1 for 2003 2013 this indicates a clear and regionally consistent acceleration of mass loss over recent decades over the entire european alps

spatial variability of glacier elevation changes in the swiss alps obtained from two digital elevation models 1 massive glacier thinning in the alps during the past 20 years is documented by direct mass balance measurements on nine regularly observed glaciers how representative this limited sample of glaciers is for the entire alps however remained uncertain the near global digital terrain model from the srtm enables a closer analysis of this question which is of fundamental importance to assess overall glacier volume change here we present elevation changes from 1985 to 1999 for about 1050 glaciers in the swiss alps the analysis reveals extreme thickness losses 80 m for flat low lying glacier tongues and a strong overall surface lowering the mean cumulative mass balance of the nine glaciers with direct measurements 10 8 m w e agrees well with the mean change of the entire region from dem differencing 11 m w e and can thus be considered to be representative mean thickness change of individual glaciers is correlated with their size elevation and exposure to solar irradiation this implies that mass losses of large glaciers can be underestimated when they are directly inferred from values measured at much smaller glaciers

estimating the longevity of glaciers in the xinjiang region of the tian shan through observations of glacier area change since the little ice age using high resolution imagery

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

glaciermip a model intercomparison of global scale glacier mass balance models and projections global scale 21st century glacier mass change projections from six published global glacier models are systematically compared as part of the glacier model intercomparison project in total 214 pro

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

the geodetic mass balance of eyjafjallajokull ice cap for 1945 2014 processing guidelines and relation to climate mass balance measurements of icelandic glaciers are sparse through the 20th century however the large archive of stereo images available allows estimates of glacier wide mass balance dot b in decadal time steps since 1945 combined with climate records they provide further insight into glacier climate relationship this study presents a workflow to process aerial photographs 1945 1995 spy satellite imagery 1977 1980 and modern satellite stereo images since 2000 using photogrammetric techniques and robust statistics in a highly automated open source pipeline to retrieve seasonally corrected decadal glacier wide geodetic mass balances in our test area eyjafjallajokull s iceland 70 km 2 we obtain a mass balance of cdata dot curr b curr 1945 curr 2014 curr 0 27 pm 0 03 rm curr m w rm curr e rm rm curr a rm ndash curr 1 with a maximum and minimum of dot curr b curr 1984 curr 1989 curr 0 77 curr pm 0 19 rm curr m curr w rm curr e rm curr rm curr a rm curr ndash 1 and dot curr b curr 1994 curr 1998 curr 1 94 curr pm 0 34 rm curr m w rm curr e rm curr rm curr a rm curr ndash 1 respectively attributed to climatic forcing and dot curr b curr 2009 curr 2010 curr 3 39 rm curr pm rm curr 0 43 rm curr m w rm curr e rm curr rm curr a rm curr ndash 1 mostly caused by the april 2010 eruption the reference surface mass balances correlate with summer temperature and winter precipitation and linear regression accounts for 80 of the mass balance variability yielding a static sensitivity of mass balance to summer temperature and winter precipitation of 2 1 0 4 m w e a 1 k 1 and 0 5 0 3 m w e a 1 10 1 respectively this study serves as a template that can be used to estimate the mass balance changes and glaciers response to climate

modelling 60 years of glacier mass balance and runoff for chhota shigri glacier western himalaya northern india glacier mass balance and runoff are simulated from 1955 to 2014 for the catchment 46 glacier cover containing chhota shigri glacier western himalaya using gridded data from three regional climate models 1 the rossby centre regional atmospheric climate model v 4 rca4 2 the regional atmosphere model remo and 3 the weather research and forecasting model wrf the input data are downscaled to the simulation grid 300 m and calibrated with point measurements of temperature and precipitation additional input is daily potential global radiation calculated using a dem at a resolution of 30 m the mass balance model calculates daily snow accumulation melt and runoff the model parameters are calibrated with available mass balance measurements and results are validated with geodetic measurements other mass balance model results and run off measurements simulated annual mass balances slightly decreased from 0 3 m w e a 1 1955 99 to 0 6 m w e a 1 for 2000 14 for the same periods mean runoff increased from 2 0 m 3 s 1 1955 99 to 2 4 m 3 s 1 2000 14 with glacier melt contributing about one third to the runoff monthly runoff increases are greatest in july due to both increased snow and glacier melt whereas slightly decreased snowmelt in august and september was more than compensated by increased glacier melt

planimetric and volumetric glacier changes in the khumbu himal nepal since 1962 using corona landsat tm and aster data multitemporal space imagery from 1962 corona kh 4 1992 landsat tm 2001 and 2005 terra aster was used to investigate the glacier changes in the khumbu himal nepal the ice coverage in the investigation area decreased by about 5 between 1962 and 2005 with the highest retreat rates occurring between 1992 and 2001 the debris coverage increased concomitantly with the decrease in total glacier area the clean ice area decreased by 10 digital terrain model dtm generation from the early corona kh 4 stereo data in this high relief terrain is time consuming and the results still contain some elevation errors however these are minor in the snow free areas with gentle slopes thus comparison of the surfaces of the debris covered glacier tongues based on the corona dtm and an aster dtm is feasible and shows the downwasting of the debris covered glaciers the highest downwasting rates more than 20 m 0 5 m a 1 can be found near the transition zone between the active and the stagnant glacier parts of the debris covered glacier tongues the downwasting is lower but still evident in the active ice areas and at the snout with thick debris cover all investigated debris covered glaciers in the study area show similar behaviour the estimated volume loss for the investigated debris covered glacier tongues is 0 19 km 3

conventional versus reference surface mass balance glacier surface mass balance evaluated over the actual glacier geometry depends not only on climatic variations but also on the dynamic adjustment of glacier geometry therefore it has been proposed that reference surface balances calculated over a constant glacier hypsometry are better suited for climatic interpretation here we present a comparison of 82 year modelled time series 1926 2008 of conventional and reference surface balance for 36 swiss glaciers over this time period the investigated glaciers have lost 22 of their area and ice surface elevation close to the current glacier terminus has decreased by 78 m on average conventional balance in the last decade at 0 91 m w e a 1 is 0 14 m w e a 1 less negative than the reference surface balance about half of the negative stabilizing feedback on mass balance due to glacier terminus retreat is compensated by more negative mass balances due to surface lowering short term climatic variability is clearly reflected in the conventional mass balance series however the magnitude of the long term negative trend is underestimated compared to that found in the reference surface balance series both conventional and reference surface specific balances show large spatial variability among the 36 glaciers

historically unprecedented global glacier decline in the early 21st century observations show that glaciers around the world are in retreat and losing mass internationally coordinated for over a century glacier monitoring activities provide an unprecedented dataset of glacier observations from ground air and space glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass balance data relating to the impact that glaciers exercise on global sea level fluctuations or on regional runoff in this study we provide an overview and analysis of the main observational datasets compiled by the world glacier monitoring service wgms the dataset on glacier front variations 42000 since 1600 delivers clear evidence that centennial glacier retreat is a global phenomenon intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the little ice age or holocene glaciological and geodetic observations 5200since 1850 show that the rates of early 21st century mass loss are without precedent on a global scale at least for the time period observed and probably also for recorded history as indicated also in reconstructions from written and illustrated documents this strong imbalance implies that glaciers in many regions will very likely suffer further ice loss even if climate remains stable

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

ice volume changes of selected glaciers in the swiss alps since the end of the 19th century the evolution of surface topography of glaciers in the swiss alps is well documented with high resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid 19th century in order to quantify and interpret glacier changes in the swiss alps time series of volume changes over the last 100 150 years have been collected the available datasets provide a detailed spatial resolution for the retreat period since the end of the little ice age the spatial distribution as well as temporal variations of the thickness change were analyzed a significant ice loss since the end of the 19th century was observed in the ablation area while the changes in the accumulation area were small we found moderate negative secular rates until the 1960s followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present an evaluation of 19 glaciers revealed a total ice volume loss of about 13 km 3 since the 1870s of which 8 7 km 3 occurred since the 1920s and 3 5 km 3 since 1980 decadal mean net balance rates for the periods 1920 60 1960 80 and 1980 present are 0 29 0 03 and 0 53 m a 1 w e respectively

glacier specific elevation changes in parts of western alaska the meltwater from glaciers in alaska contributes strongly to global sea level rise but accurate determination is challenging as only two comparatively small glaciers have long term measurements of annual mass balance gulkana and wolverine simple upscaling of their values to the entire region is error prone as their representativeness is unknown and might be biased alternatively differencing digital elevation models dems from two epochs provides overall volume changes for a longer period of time that can be converted to mass changes using appropriate density assumptions here we combine outlines from two glacier inventories to determine glacier specific elevation changes over a 50 year period for 3180 glaciers in western alaska using dem differencing this allows us to determine the representativeness of the land terminating gulkana and wolverine glaciers for the entire region and to exclude calving glaciers marine and lacustrine from the sample mean changes for all land terminating lake terminating and tidewater glaciers are 0 23 0 44 0 63 0 40 and 0 64 0 66 m a 1 respectively and 0 7 and 0 6 m a 1 for the two mass balance or benchmark glaciers thus fortuitously their changes better represent calving glaciers and the overall mean 0 63 1 14 m a 1 than the change of land terminating glaciers i e they are not representative for their own type different methods of considering potential dem artefacts provide variable mean changes but the same general result