surface and bed topography of trapridge glacier yukon territory canada digital elevation models and derived hydraulic geometry measurements of ice thickness and surface elevation are prerequisite to many glaci ological investigations a variety of techniques has been develo ped for inter pret ation of these data including means of constructing regularly gridded digital eleva tion models dem s for use in numcrical studies here we present a simple yet stati sti cally sound method for processing ice pe netr ating radar data and descr ibe a tech nique for interpol ating these data onto a regular grid dems generatcd fort rapridge glacier yukon territory canada are used to derive geometric quantities lhal give pre liminary insights into the underlying basin scale hydrol ogical syste m this simple geo metric analysis suggests that at low water press ures a dendrilic drainage netw ork exists that evolves into a uniaxial morphology as water pressure approaches notation these pre dictions are compared to hydraulic connection probabilities based on bore hole drilling

simulations of water movement and solute transport through different soil texture configurations under negative pressure irrigation this study examined the effects of different soil texture configurations on water movement and solute transport to provide a reliable scientific basis for the application of negative pressure irrigation npi technology hydrus 2d was used to analyze water movement and solute transport under npi the main results are as follows 1 hydrus 2d can be used to simulate water movement and solute transport under npi as there was good agreement between the simulated and measured values for water contents nacl concentrations and wetting distances in the horizontal and vertical directions the nash sutcliffe efficiency coefficients were in the range of 0 94 0 97 2 layered soils have obvious effects on water movement under npi with the emitter position in the loam layer when a coarse texture of loamy sand was present below the loam layer namely l ls irrigation water accumulated in the topsoil and this led to an increase in evaporation compared with the homogeneous loam profile however fine texture silty loam or silty clay loam layers beneath the loam layer namely l sil or l sicl respectively was more conducive to water infiltration into the lower layer and this increased the amount of water infiltration and simultaneously reduced the surface evaporation effectively 3 layered soils have obvious effects on solute transport under npi and salt accumulation will readily occur in the clay rich soil layer at the interface the maximum soil salt accumulation of l ls occurred above the soil interface between the two soil layers with a value of 21 8 g kg 1 however for l sicl and l sil the maximum salt accumulation occurred below the soil interface between the two soil layers with values of 23 8 g kg 1 and 20 08 g kg 1 respectively 4 interlayered soils showed remarkable changes in the water infiltration characteristics and salt leaching intensities under npi and the properties for the soil profile with a silty loam interlayer were better than those for the soil profile with a silty clay loam interlayer the soil profile with a loamy sand interlayer had the lowest amount of water infiltration which resulted in reductions of the salt leaching intensities thus npi is clearly not suitable for loamy sand soil overall the results demonstrated that soil texture configurations affected water movement and solute transport under npi therefore careful consideration should be given to the use of npi to achieve target soil water and solution conditions and reduce water loss

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

identification of alpine glaciers in the central himalayas using fully polarimetric l band sar data to study the applicability of full polarimetric synthetic aperture radar sar data to identify alpine glaciers in the central himalayas six polarimetric decomposition methods were used to obtain 20 polarimetric characteristic parameters based on the advanced land observing satellite 2 alos 2 phased array type l band sar palsar data object oriented multiscale segmentation was performed on a landsat 8 operational land imager oli image prior to classification and the vector boundaries of different types of training samples were selected from the segmented results we performed a support vector machine svm based classification on the characteristic parameters from each polarimetric decomposition all 20 parameters were then screened and combined according to different requirements the degree of separability of different types of training samples and the type of scattering mechanisms the results show that the classification accuracy of the incoherent decomposition characteristics based on the covariance matrix is the best reaching 87 and it can exceed 91 after adding the local incidence angle to the suite of classifiers eventually more than 93 accuracy was achieved using a combination of multiple polarimetric parameters which reduced the misclassification between bare ice and rock we also analyzed the use of controlling factors on the accuracy of alpine glacier identification and found that the polarimetric information and aspect of the glacier surface are the most important factors the former is the main basis for identification but the latter will confuse the feature distributions of different categories and cause misclassification

global distributions of glacier properties a stochastic scaling paradigm many problems in global climate and earth systems science require knowledge of regional or global scale distributions of glacier properties which includes mass balance ice velocity flux thickness volume and surface area among others with roughly 160 000 glaciers worldwide obtaining information on the global probability distributions of most ice properties is expensive and often infeasible only surface area distributions are relatively easy to measure either by direct observation or remote sensing while other properties are difficult to observe this work shows that scaling relationships from the continuum dynamics of ice can link the distribution of surface areas to the global and regional distributions of any other continuum property some data inventories already exist for constructing reasonable distributions of glacier sizes and this analysis presents theoretical arguments based on glacier network topologies similar in concept to river networks to suggest a power law times an exponential distribution of surface areas in agreement with the data therefore by using existing data or the theoretical distributions of surface areas specific distributions for other glacier properties in any region of the world can be constructed as an example predictions up to a scaling constant are made for the distribution of glacier volumes characteristic thicknesses characteristic velocities and characteristic response times in the alps

a consensus estimate for the ice thickness distribution of all glaciers on earth knowledge of the ice thickness distribution of the world s glaciers is a fundamental prerequisite for a range of studies projections of future glacier change estimates of the available freshwater resources or assessments of potential sea level rise all need glacier ice thickness to be accurately constrained previous estimates of global glacier volumes are mostly based on scaling relations between glacier area and volume and only one study provides global scale information on the ice thickness distribution of individual glaciers here we use an ensemble of up to five models to provide a consensus estimate for the ice thickness distribution of all the about 215 000 glaciers outside the greenland and antarctic ice sheets the models use principles of ice flow dynamics to invert for ice thickness from surface characteristics we find a total volume of 158 41 103 km3 which is equivalent to 0 32 0 08 m of sea level change when the fraction of ice located below present day sea level roughly 15 is subtracted our results indicate that high mountain asia hosts about 27 less glacier ice than previously suggested and imply that the timing by which the region is expected to lose half of its present day glacier area has to be moved forward by about one decade the ice volume of glaciers outside the greenland and antarctic ice sheets totals about 158 000 km3 with about 27 less ice in high mountain asia than thought according to multiple models that estimate ice thickness from surface characteristics

volume measurements of mittivakkat gletscher southeast greenland here we present ground penetrating radar measurements of mittivakkat gletscher southeast greenland to estimate an empirical volume area scaling relationship at an individual glacier between a previous direct volume survey in 1994 and one in 2012 the glacier volume has decreased from 2 02 km 3 to 1 44 km 3 while the study area has decreased from 17 6 km 2 to 15 8 km 2 these results are in accordance with the cumulative mass loss observed by long term mass balance measurements 1995 96 2011 12 at mittivakkat gletscher and confirm that the glacier is in severe climatic disequilibrium aar 0 17 the observed scaling exponent 3 14 and coefficient c 0 00025 km 3 2 are outside the range of global scaling parameters but sensitive to small uncertainties nevertheless existing global volume area scaling relationships estimate the volume of mittivakkat gletscher within 31 and 15 of the measured 1994 and 2011 volumes respectively

atmospheric patterns over the antarctic peninsula abstractusing clustering analysis for the sea level pressure field of the era interim reanalysis between 1979 and 2016 five synoptic pressure patterns have been obtained for the drake area and antarctic peninsula ap region 45 75 s 20 120 w and the resulting daily series has been made available to the scientific community the five patterns have been named according to their most important features as follows low over the weddell sea lws low over the amundsen and bellingshausen seas lab low over the drake passage ldp zonal flow over the drake passage zdp and ridge over the antarctic peninsula rap each atmospheric pattern is described after analyzing its development and evolution a frequency analysis shows that the five atmospheric patterns present a similar annual frequency but a large seasonal variability the transitions from one pattern to another tend to follow a cycle in which synoptic atmospheric waves are displaced eastward by a quarter wavelength four of the five atmosphe

regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data 1 very few global scale ice volume estimates are available for mountain glaciers and ice caps although such estimates are crucial for any attempts to project their contribution to sea level rise in the future we present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from 123 000 glaciers from a recently extended world glacier inventory we compute glacier volumes and their sea level equivalent sle for 19 glacierized regions containing all mountain glaciers and ice caps on earth on the basis of total glacierized area of 741 103 68 103 km2 we estimate a total ice volume of 241 103 29 103 km3 corresponding to 0 60 0 07 m sle of which 32 is due to glaciers in greenland and antarctica apart from the ice sheets however our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried i e antarctica north america greenland and patagonia this emphasizes the need for more volume observations especially of large glaciers and a more complete world glacier inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps

a more complete version of the world glacier inventory the world glacier inventory wgi was conceived half a century ago as an activity to be completed during the international geophysical year 1957 58 it consisted until very recently of nearly 70 000 glacier records covering slightly less than one quarter of the glacier ice outside the ice sheets a complete wgi must be a compromise if it is to be available and usable soon a more complete version called wgi xf is available and usable now and contains records for just over 131 000 glaciers and nearly half of the global extent of ice the additional glaciers come mainly from the assimilation of existing inventories but also from rescuing inventories that have been lost and from new inventories in canada and the subantarctic in wgi xf the xf stands for extended format flagging the fact that wgi xf conforms to a set of explicit specifications which enhance usefulness by eliminating low level inconsistencies two important features are nominal glaciers and glacier complexes a nominal glacier of which there are about 5000 in wgi xf is one about which little is known other than its existence and approximate location a glacier complex is one or more contiguous glaciers this term embodies the idea which is not new that inventories can be preliminary based upon vector outlines which await subdivision by trained glaciologists many regional studies have found that measurements of changes in single glaciers require accurate work and painstaking quality control wgi xf is not assuredly reliable as a source for such detailed work but there are several other subjects in which less detail would be a price worth paying for more complete coverage incomplete information about the dates of imagery and maps is a hindrance to analysis and the recovery of dates from metadata should have high priority

estimate of the total volume of svalbard glaciers and their potential contribution to sea level rise using new regionally based scaling relationships we present a set of new volume scaling relationships specific to svalbard glaciers derived from a sample of 60 volume area pairs glacier volumes are computed from ground penetrating radar gpr retrieved ice thickness measurements which have been compiled from different sources for this study the most precise scaling models in terms of lowest cross validation errors are obtained using a multivariate approach where in addition to glacier area glacier length and elevation range are also used as predictors using this multivariate scaling approach together with the randolph glacier inventory v3 2 for svalbard and jan mayen we obtain a regional volume estimate of 6700 835 km3 or 17 2 mm of sea level equivalent sle this result lies in the mid to low range of recently published estimates which show values as varied as 13 and 24 mm sle we assess the sensitivity of the scaling exponents to glacier characteristics such as size aspect ratio and average slope and find that the volume of steep slope and cirque type glaciers is not very sensitive to changes in glacier area

application of inventory data for estimating characteristics of and regional climate change effects on mountain glaciers a pilot study with the european alps a parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate change effects on mountain glaciers for past and potential climate scenarios glacier changes for assumed mass balance changes are calculated as step functions between steady state conditions for time intervals that approximately correspond to the characteristic dynamic response time a few decades of the glaciers in order to test the procedure a pilot study was carried out in the european alps where detailed glacier inventories had been compiled around the mid 1970s total glacier volume in the alps is estimated at about 130 km3 for the mid 1970s strongly negative mass balances are likely to have caused a loss of about 10 20 of this total volume during the decade 1980 90 backward calculation of glacier length changes using a mean annual mass balance of 0 25m w e a 1 since the end of the little ice age around 1850 ad gives considerable scatter but satisfactory overall results as compared with long term observations the total loss of alpine surface ice mass since 1850 can be estimated at about half the original value an acceleration of this development with annual mass losses of around 1 m a 1 or more as anticipated from ipcc scenario a for the coming century could eliminate major parts of the presently existing alpine ice volume within decades

comment on the potential for sea level rise new estimates from glacier and ice cap area and volume distribution by s c b raper and r j braithwaite

radio echo sounding and ice volume estimates of western nordenskiold land glaciers svalbard as part of ongoing work to obtain a reliable estimate of the total ice volume of svalbard glaciers and their potential contribution to sea level rise we present here volume calculations with detailed error estimates for ten glaciers on western nordenskiold land central spitsbergen svalbard the volume estimates are based upon a dense net of gpr retrieved ice thickness data collected over several field campaigns spanning the period 1999 2012 the total area and volume of the ensemble are 116 06 4 53 km 2 and 10 439 0 373 km 3 respectively while the individual areas volumes and average ice thickness lie within 2 6 50 4 km 2 0 08 5 54 km 3 and 29 108 m respectively volume area scaling relationships overestimate the total volume of these glaciers by up to 35 with respect to our calculation on the basis of the pattern of scattering in the radargrams we also analyse the hydrothermal structure of these glaciers nine of the ten are polythermal while only one is entirely cold

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

ice volume and subglacial topography for western canadian glaciers from mass balance fields thinning rates and a bed stress model abstracta method is described to estimate the thickness of glacier ice using information derived from the measured ice extent surface topography surface mass balance and rate of thinning or thickening of the ice column shear stress beneath an ice column is assumed to be simply related to ice thickness and surface slope as for an inclined slab but this calculation is cast as a linear optimization problem so that a smoothness regularization can be applied assignment of bed stress is based on the flow law for ice and a mass balance calculation but must be preceded by delineation of the ice flow drainage basin validation of the method is accomplished by comparing thickness estimates to the known thickness generated by a numerical ice dynamics model once validated the method is used to estimate the subglacial topography for all glaciers in western canada that lie south of 60 n adding the present ice volume of each glacier gives the estimated total volume as 2320 km3 equivalent to 5 8 mm of sea leve

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

width and length scaling of glaciers an analysis of hundreds of mountain and valley glaciers in the former soviet union and the alps shows that characteristic glacier widths scale as characteristic glacier lengths raised to an exponent of 0 6 this is in contrast to most previous analyses which implicitly or explicitly assumed scaling exponents of either 0 or 1 the exponent 0 6 implies that average glacier widths are proportional to average glacier thicknesses although this seems to suggest v shaped glacier valleys the linear width thickness relationship is not inconsistent with parabolic valley cross sections because the characteristic or average width of a glacier depends on many other aspects of channel and glacier morphology including variations in the channel width with distance up and downstream

post mortem onshore transportation of epiphytic foraminifera recent example from the tunisian coastline abstract the barrier island system that connects jerba island to the tunisian coastline is composed mainly of carbonate bioclastic sands well preserved tests of dead epiphytic foraminifera are abundant on the foreshore and backshore but they are scattered and poorly preserved on the shoreface where very fine sand size eolian quartz peloids and broken bioclasts are the main components the reason for this paradoxical pattern is that most epiphytic foraminifera are very easily removed as suspended load by storm generated currents and concentrated on beaches washover fans and small eolian dunes kilometers away from their original life environment similar bioaccumulations are common in the fossil record and have often been interpreted incorrectly as prolific biocoenoses

snow patch and glacier size distributions a simple theoretical model demonstrates that some amount of randomness in snow and ice mass balance is sufficient to reproduce empirically observed power law and exponential distributions of snow patch and glacier sizes no other assumptions about the underlying topography or snow accumulation and ablation processes are necessary to extract this important spatial property the inclusion of additional geometrical and physical processes can alter the specific scaling constants of the size distributions but the fundamental behavior remains unchanged specifically for snow patch and glacier sizes less than some correlation length the size distribution is a decreasing power law and for sizes larger than the correlation length the distribution decreases rapidly as an exponential the solution is based on a mapping to a relatively well explored class of problems in percolation theory

an extended perfect plasticity method for estimating ice thickness along the flow line of mountain glaciers 1 direct measurement of the thickness of mountain glaciers is difficult over large areas yet knowledge of the thickness is essential for calculating their volumes and future evolution we develop a new method for estimating the ice thickness along glacier flow lines using the perfect plasticity rheological assumption that relates the thickness and surface slope to a yield stress previous studies have used this assumption with the shallow ice approximation to estimate the ice thickness but the standard approach neglects the effect of side drag on glacier stress balance our method addresses this shortcoming and extends the standard method by accounting for the side drag via the glacier width besides the assumed yield stress the inputs for our method are the outline and surface topography of the glacier surface velocity and mass balance data are unnecessary we validated the extended method on five glaciers in northwest china where thickness data are available from radio echo soundings finding that it can reproduce measured thicknesses with a mean absolute error of 11 8 like the standard method moreover for long glacier tongues confined to flow between parallel valley sides this method is found to give more accurate thickness estimates than does the standard method with a mean absolute error of as low as 5 3 sensitivity analysis shows that the estimated ice thickness depends strongly on yield stress and surface slope and less strongly on glacier width because this method is physically more realistic than the standard method and its inputs are easily derivable from remote sensing observations it has the potential to be used for processing large glacier data sets

volume area scaling vs flowline modelling in glacier volume projections volume area scaling provides a practical alternative to ice flow modelling to account for glacier size changes when modelling the future evolution of glaciers however uncertainties remain as to the validity of this approach under non steady conditions we address these uncertainties by deriving scaling exponents in the volume area relationship from one dimensional ice flow modelling we generate a set of 37 synthetic steady state glaciers of different sizes and then model their volume evolution due to climate warming and cooling as prescribed by negative and positive mass balance perturbations respectively on a century timescale the scaling exponent derived for the steady state glaciers 1 56 differs from the exponents derived for the glaciers in transient non steady state by up to 86 nevertheless volume projections employing volume area scaling are relatively insensitive to these differences in scaling exponents volume area scaling agrees well with the results from ice flow modelling in addition the scaling method is able to simulate the approach of a glacier to a new steady state if mass balance elevation feedback is approximated by removing or adding elevation bands at the lowest part of the glacier as the glacier retreats or advances if area changes are approximated in the mass balance computations in this way our results indicate that volume area scaling is a powerful tool for glacier volume projections on multi century timescales

analysis of scaling methods in deriving future volume evolutions of valley glaciers volume area scaling is a common tool for deriving future volume evolutions of valley glaciers and their contribution to sea level rise we analyze the performance of scaling relationships for deriving volume projections in comparison to projections from a one dimensional ice flow model the model is calibrated for six glaciers nigardsbreen rhonegletscher south cascade glacier sofiyskiy glacier midre lovenbreen and abramov glacier volume evolutions forced by different hypothetical mass balance perturbations are compared with those obtained from volume area v a volume length v l and volume area length v a l scaling results show that the scaling methods mostly underestimate the volume losses predicted by the ice flow model up to 47 for v a scaling and up to 18 for v l scaling by the end of the 100 year simulation period in general v l scaling produces closer simulations of volume evolutions derived from the ice flow model suggesting that v l scaling may be a better approach for deriving volume projections than v a scaling sensitivity experiments show that the initial volumes and volume evolutions are highly sensitive to the choice of the scaling constants yielding both over and underestimates however when normalized by initial volume volume evolutions are relatively insensitive to the choice of scaling constants especially in the v l scaling the 100 year volume projections differ within 10 of initial volume when the v a scaling exponent commonly assumed 1 375 is varied by 30 to 45 0 95 2 00 and the v l scaling exponent q 2 2 is varied by 30 to 45 q 1 52 3 20 this is encouraging for the use of scaling methods in glacier volume projections particularly since scaling exponents may vary between glaciers and the scaling constants are generally unknown

a new inventory of mountain glaciers and ice caps for the antarctic periphery although the glaciers in the antarctic periphery make up a large fraction of all mountain glaciers and ice caps on earth a detailed glacier inventory of the region is lacking we compile such an inventory recording areas area altitude distributions terminus characteristics and volume estimates glaciers on the mainland are excluded the inventory is derived from the antarctic digital database and some manual digitization we additionally rely on satellite imagery digital elevation models and a flowshed algorithm to classify ice bodies we find 1133 ice caps and 1619 mountain glaciers covering a total of 132 867 6643 km 2 estimated total volume corresponds to 0 121 0 010 m sea level equivalent of the total glacier area 99 drains either into ice shelves 63 or into the ocean 36 the inventory will provide a database for glacier mass balance assessments modelling and projections and help to reduce the uncertainties in previous studies

mountain glaciers and ice caps around antarctica make a large sea level rise contribution the intergovernmental panel on climate change ipcc estimates that the sum of all contributions to sea level rise for the period 1961 2004 was 1 1 0 5 mm a 1 leaving 0 7

the potential for sea level rise new estimates from glacier and ice cap area and volume distributions projections of sea level rise from mountain glaciers and ice caps for the next century and beyond should be based on an assessment of the ice available for melting projections to date are based on all regions except greenland and antarctica the latter are considered separately by the ipcc yet no sound estimates for the appropriate volume of ice and its potential for sea level rise are evident in the literature an ice cap data set is compiled allowing the separate treatment of glacier area coverage data glacier inventory data are comprehensive enough in some regions to allow the estimation of glacier size distributions the differences in the distributions are related to a metric of the regional topographic variability allowing glacier size distributions to be estimated on a 1 latitude longitude grid of cells containing glaciers appropriate volume area scaling for glaciers and for ice caps gives global estimates of glacier and ice cap volumes by size class this leads to an estimate of the total ice volume of 0 087 0 010 106 km3 and a sea level rise equivalent of 0 241 0 026 m the glaciers and ice caps contribute 41 and 59 to these estimates respectively these values are based on data sets compiled during several decades mainly in the second half of the 20th century we compare our results to published results that include the glaciers and icecaps at the margins of the greenland and antarctic ice sheets

potential for bias in 21st century semiempirical sea level projections we examine the limitations of a semiempirical model characterized by a sea level projection of 73 cm with rcp4 5 scenario by 2100 calibrating the model with data to 1990 and then simulating the period 1993 2009 produces sea level in close agreement with acceleration in sea level rise observed by satellite altimetry nonradiative forcing contributors such as long term adjustment of greenland and antarctica ice sheets since last glacial maximum abyssal ocean warming and terrestrial water storage may bias model calibration which if corrected for tend to reduce median sea level projections at 2100 by 2 10 cm though this is within the confidence interval we apply the semiempirical approach to simulate individual contributions from thermal expansion and small glacier melting steric sea level projections agree within 3 cm of output from process based climate models in contrast semiempirical simulation of melting from glaciers is 26 cm which is twice large as estimates from some process based models however all process models lack simulation of calving which likely accounts for 50 of small glacier mass loss worldwide furthermore we suggest that changes in surface mass balance and dynamics of greenland ice sheet made contributions to the sea level rise in the early 20th century and therefore are included within the semiempirical model calibration period and hence are included in semiempirical sea level projections by 2100 antarctic response is probably absent from semiempirical models which will lead to a underestimate in sea level rise if as is probable antarctica loses mass by 2100

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

a method to estimate the ice volume and ice thickness distribution of alpine glaciers sound knowledge of the ice volume and ice thickness distribution of a glacier is essential for many glaciological applications however direct measurements of ice thickness are laborious not feasible everywhere and necessarily restricted to a small number of glaciers in this paper we present a method to estimate the ice thickness distribution and the total ice volume of alpine glaciers this method is based on glacier mass turnover and principles of ice flow mechanics the required input data are the glacier surface topography the glacier outline and a set of borders delineating different ice flow catchments three parameters describe the distribution of the apparent mass balance which is defined as the difference between the glacier surface mass balance and the rate of ice thickness change and two parameters define the ice flow dynamics the method was developed and validated on four alpine glaciers located in switzerland for which the bedrock topography is partially known from radio echo soundings the ice thickness along 82 cross profiles can be reproduced with an average deviation of about 25 between the calculated and the measured ice thickness the cross sectional areas differ by less than 20 on average this shows the potential of the method for estimating the ice thickness distribution of alpine glaciers without the use of direct measurements

neural networks applied to estimating subglacial topography and glacier volume abstract to predict the rate and consequences of shrinkage of the earth s mountain glaciers and ice caps it is necessary to have improved regional scale models of mountain glaciation and better knowledge of the subglacial topography upon which these models must operate the problem of estimating glacier ice thickness is addressed by developing an artificial neural network ann approach that uses calculations performed on a digital elevation model dem and on a mask of the present day ice cover because suitable data from real glaciers are lacking the ann is trained by substituting the known topography of ice denuded regions adjacent to the ice covered regions of interest and this known topography is hidden by imagining it to be ice covered for this training it is assumed that the topography is flooded to various levels by horizontal lake like glaciers the validity of this assumption and the estimation skill of the trained ann is tested by predicting ice thickness for four 50 km 50 km regions that

testing the robustness of semi empirical sea level projections we determine the parameters of the semi empirical link between global temperature and global sea level in a wide variety of ways using different equations different data sets for temperature and sea level as well as different statistical techniques we then compare projections of all these different model versions over 30 for a moderate global warming scenario for the period 2000 2100 we find the projections are robust and are mostly within 20 of that obtained with the method of vermeer and rahmstorf proc natl acad sci usa 106 21527 21532 2009 namely 1 m for the given warming of 1 8 c lower projections are obtained only if the correction for reservoir storage is ignored and or the sea level data set of church and white surv geophys 2011 is used however the latter provides an estimate of the base temperature t 0 that conflicts with the constraints from three other data sets in particular with proxy data showing stable sea level over the period 1400 1800 our new best estimate model accounting also for groundwater pumping is very close to the model of vermeer and rahmstorf proc natl acad sci usa 106 21527 21532 2009

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

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