the influence of debris cover and glacial lakes on the recession of glaciers in sikkim himalaya india we investigated area changes in glaciers covering an area of similar to 200 km 2 in the tista basin sikkim eastern indian himalaya between similar to 1990 and 2010 using landsat thematic mapper tm and indian remote sensing satellite irs images and related the changes to debris cover supraglacial lakes and moraine dam lakes the glaciers lost an area of 3 3 0 8 between 1989 90 and 2010 more detailed analysis revealed an area loss of 2 00 0 82 2 56 0 61 and 2 28 2 01 km 2 for the periods 1989 97 1997 2004 05 and 2004 2009 10 respectively this indicates an accelerated retreat of glaciers after 1997 on further analysis we observed 1 the formation and expansion of supraglacial lakes on many debris covered glaciers and 2 the merging of these lakes over time leading to the development of large moraine dam lakes we also observed that debris covered glaciers with lakes lose a greater area than debris covered glaciers without lakes and debris free glaciers the climatic data for 24 years 1987 2011 measured at the gangtok meteorological station 1812 m a s l showed that the region experienced a 1 0 degrees c rise in the summer minimum temperature and a 2 0 degrees c rise in the winter minimum temperature indicating hotter summers and warmer winters there was no significant trend in the total annual precipitation we find that glacier retreat is caused mainly by a temperature increase and that debris covered glaciers can retreat at a faster rate than debris free glaciers if associated with lakes

correcting regional seismic discriminants for path effects in western china abstract the effect of path on regional seismic wave propagation can be significant in an effort to improve discriminant performance we explore the effect of path upon p g l g ratios our primary objective is to find path corrections that reduce scatter within earthquake and explosion ratio populations while at the same time increasing the separation between the two populations we emphasize the 1 5 to 3 hz and 2 to 4 hz bands as p g and l g in these bands can often be observed at smaller magnitudes and greater distances than higher frequency bands which have previously been shown to be reliable discriminants for data we use 271 earthquakes from northwest china 25 nuclear explosions from the kazakh test site kts and one nuclear explosion from the lop nor test site recorded at station wmq we also use 185 earthquakes from the same region and seven nuclear explosion from the lop nor test site recorded at station aak event station distances range from 200 to 1400 km earthquake magnitudes range between m b 2 5 and 6 2 and explosion magnitudes range between m b 4 5 and 6 5 in addition to ratio distance trends we examine p g l g ratio parameter trends related to topography basin thickness and crustal thickness the parameters we consider are mean roughness gradient mean and gradient roughness of the topography basin thickness and crustal thickness along each event station path we also consider the same parameters after weighting by path length through linear regressions we found path corrections that reduce scatter within event populations and we also found path corrections that increase the separation between earthquakes and kts explosions recorded at wmq we obtained the best improvement in discrimination performance at wmq by removing the trends of topography roughness mean topography and the gradient of basin thickness after weighting the parameters by path length for aak we found that removing the trends of mean topography and the basement roughness improved discrimination performance over the uncorrected case however unlike wmq weighting these parameters by path length degraded discriminant performance because we see no predictable or repeatable trends for adjacent central asian stations and overlapping regions of interest we recommend an even more empirical approach to correcting for the effect of path where earthquakes are abundant such as the tian shan contouring a grid of ratio residuals for each band of interest may be a simpler method of finding appropriate path corrections

sea ice thickness estimations from icesat altimetry over the bellingshausen and amundsen seas 2003 2009 1 sea ice thicknesses derived from nasa s ice cloud and land elevation satellite icesat altimetry data are examined using two different approaches buoyancy and empirical equations and at two spatial scales icesat footprint size 70 m diameter spot and advanced microwave scanning radiometer amsr e pixel size 12 5 km by 12 5 km for the bellingshausen and amundsen seas of west antarctica ice thickness from the empirical equation shows reasonable spatial and temporal distribution of ice thickness from 2003 to 2009 ice thickness from the buoyancy equation however additionally needing snow depth information derived from the amsr e shows an overestimation in terms of maximum mean 63 to 75 and standard deviation while underestimation in modal thickness 20 as compared with those from the empirical equation approach when icesat snow freeboard is used as the snow depth in the buoyancy equation i e the zero ice freeboard assumption the derived ice thicknesses match well with those from the empirical equation approach within 5 overall the amsr e therefore may underestimate snow depth and accounts for 95 of the ice thickness overestimation as compared with the buoyancy approach the empirical equation derived ice thickness shows a consistent asymmetrical distribution with a long tail to high values and seasonal median values ranging from 0 8 to 1 4 m over the 2003 2009 period that are always larger than the corresponding modal values 0 6 1 1 m and lower than the mean values 1 0 1 6 m with standard deviation of 0 6 1 0 m an overall increasing trend of 0 03 m year of mean ice thickness is found from 2003 to 2009 although statistically insignificant p 0 11 at the 95 confidence level starting from autumn a general picture of seasonal mean modal and median ice thickness increases progressively from autumn to spring and decreases from spring to the following autumn when new thin ice dominates the ice thickness distribution the asymmetric shape of the thickness distribution reflects the key role of ice deformation processes in the evolution of the thickness distribution the statistical properties of the thickness distribution interannually high range of mean thickness and standard deviation indicate the variability of deformation processes however spring ice volume the product of ice mean thickness and areal extent computed for the spring maximum shows variability year to year but is primarily dominated by ice extent variability with no increasing or decreasing trend over this record length the dependence of the volume on the ice extent primarily suggests that ice thickness changes have also not covaried with the ice extent losses seen over the satellite record in this region unlike the arctic these properties reflect the interactive processes of ice advection thermodynamic growth and ice deformation that all substantially influence ice mass balance in the bellingshausen amundsen seas region

cryosphere applications of nscat data though designed to measure vector winds over the ocean new imaging techniques facilitate the use of nasa scatterometer data nscat in cryosphere studies nscat provides data of unprecedented coverage resolution and quality which when coupled with the scatterometer image reconstruction with filtering sirf algorithm enables images of spl sigma sup o at resolutions approaching 8 km over stationary targets such images are useful in ice mapping and classification and multidecadal studies are possible by comparison with seasat scatterometer sass data the utility of nscat data in polar ice studies is illustrated through a review of two cryosphere applications of nscat data 1 sea ice mapping and tracking and 2 ice sheet change in greenland and antarctica the wide swath and frequent revisit coupled with incidence and azimuth angle diversity makes nscat data very effective in mapping the extent of sea ice in greenland snow and ice facies are clearly delineated on the basis of the seasonally dependent radar backscattering cross section due to sensitivity of radar backscatter to diagenetic changes occurring at and beneath the surface comparison of nscat and sass data enables study of change in greenland between 1978 and 1996

estimation of sea ice thickness in ross and weddell seas from ssm i brightness temperatures in polar regions ocean atmosphere interactions are strongly influenced by sea ice and its thickness since satellite passive microwave observations became available in the 1970s significant progress has been made in the study of snow depth and sea ice concentration and extent in these regions estimating sea ice thickness sit instead turned out to be considerably more difficult we present a new empirical algorithm to estimate sit in the ross and weddell seas from special sensor microwave imager brightness temperatures this algorithm combines brightness temperature polarization difference and ratio values to obtain sit for seasonal ice up to a thickness of about 90 cm during freezing conditions a series of filters accounts for open water new ice and snow on sea ice our sit estimates are consistent with colocated visual ship based sit observations made according to the antarctic sea ice processes and climate project showing linear correlation values between 0 73 and 0 96 and root mean square error values between 14 and 24 cm the seasonal development of the region average sit derived with our approach agrees with the corresponding values derived from u s national ice center ice charts comparison with colocated polynya distribution maps suggests that the algorithm could be optimized for its performance with regard to sit values around 50 cm and that a closer investigation of the snow impact on the sit retrieval is required

snow accumulation rate on qomolangma mount everest himalaya synchroneity with sites across the tibetan plateau on 50 100 year timescales annual layer thickness data spanning ad 1534 2001 from an ice core from east rongbuk col on qomolangma mount everest himalaya yield an age depth profile that deviates systematically from a constant accumulation rate analytical model the profile clearly shows that the mean accumulation rate has changed every 50 100 years a numerical model was developed to determine the magnitude of these multi decadal scale rates the model was used to obtain a time series of annual accumulation the mean annual accumulation rate decreased from 0 8m ice equivalent in the 1500s to 0 3m in the mid 1800s from 1880 to 1970 the rate increased however it has decreased since 1970 comparison with six other records from the himalaya and the tibetan plateau shows that the changes in accumulation in east rongbuk col are broadly consistent with a regional pattern over much of the plateau this suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area however a record from dasuopu only 125 km northwest of qomolangma and 700 m higher than east rongbuk col shows a maximum in accumulation during the 1800s a time during which the east rongbuk col and tibetan plateau ice core and tree ring records show a minimum this asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology

the impact of early summer snow properties on antarctic landfast sea ice x band backscatter up to now snow cover on antarctic sea ice and its impact on radar backscatter particularly after the onset of freeze thaw processes are not well understood here we present a combined analysis of in situ observations of snow properties from the landfast sea ice in atka bay antarctica and high resolution terrasar x backscatter data for the transition from austral spring november 2012 to summer january 2013 the physical changes in the seasonal snow cover during that time are reflected in the evolution of terrasar x backscatter we are able to explain 76 93 of the spatio temporal variability of the terrasar x backscatter signal with up to four snowpack parameters with a root mean squared error of 0 87 1 62 db using a simple multiple linear model over the complete study and especially after the onset of early melt processes and freeze thaw cycles the majority of variability in the backscatter is influenced by changes in snow ice interface temperature snow depth and top layer grain size this suggests it may be possible to retrieve snow physical properties over antarctic sea ice from x band sar backscatter

snow thickness profiling on antarctic sea ice with gpr rapid and accurate measurements with the potential to upscale needles to a haystack snow thickness on sea ice is a largely under sampled parameter yet of importance for the sea ice mass balance and for satellite based sea ice thickness estimates and thus our general understanding of global ice volume change traditional direct thickness measurements with meter sticks can provide accurate but only spot information referred to as needles due to their pinpoint focus and information while airborne and satellite remote sensing snow products referred to as the haystack have large uncertainties due to their scale we demonstrate the remarkable accuracy and applicability of ground penetrating radar gpr snow thickness measurements by comparing them with in situ meter stick data from two field campaigns to antarctica in late winter early spring the efficiency and millimeter to centimeter accuracy of gpr enables practitioners to acquire extensive semi regional data with the potential to upscale needles to the haystack and to potentially calibrate satellite remote sensing products that we confirm to derive roughly 30 of the in situ thickness we find the radar wave propagation velocity in snow to be rather constant 6 encouraging regional snow thickness surveys snow thinner than 10 cm is under the detection limit with the off the shelf gpr setup utilized in our study

on the accuracy of glacier outlines derived from remote sensing data deriving glacier outlines from satellite data has become increasingly popular in the past decade in particular when glacier outlines are used as a base for change assessment it is important to know how accurate they are calculating the accuracy correctly is challenging as appropriate reference data e g from higher resolution sensors are seldom available moreover after the required manual correction of the raw outlines e g for debris cover such a comparison would only reveal the accuracy of the analyst rather than of the algorithm applied here we compare outlines for clean and debris covered glaciers as derived from single and multiple digitizing by different or the same analysts on very high 1 m and medium resolution 30 m remote sensing data against each other and to glacier outlines derived from automated classification of landsat thematic mapper data results show a high variability in the interpretation of debris covered glacier parts largely independent of the spatial resolution area differences were up to 30 and an overall good agreement for clean ice with sufficient contrast to the surrounding terrain differences 5 the differences of the automatically derived outlines from a reference value are as small as the standard deviation of the manual digitizations from several analysts based on these results we conclude that automated mapping of clean ice is preferable to manual digitization and recommend using the latter method only for required corrections of incorrectly mapped glacier parts e g debris cover shadow

influence of debris cover and altitude on glacier surface melting a case study on dokriani glacier central himalaya india most of the central himalayan glaciers have surface debris layers of variable thickness which greatly affect the ablation rate an attempt has been made to relate debris cover thickness to glacier surface melting thirty stakes were used to calculate ablation for debris covered and clean ice of dokriani glacier 7km 2 from 2009 10 to 2012 13 our study revealed significant altitude wise difference in the rate of clean and debris covered ice melting we found a high correlation r 2 0 92 between mean annual clean ice ablation and altitude and a very low correlation r 2 0 14 between debris covered ice melting and altitude debris covered ice ablation varies with variation in debris thickness from 1 to 40cm ablation was maximum under debris thicknesses of 1 6cm and minimum under 40cm even a small debris cover thickness 1 2cm reduces ice melting as compared to that of clean ice on an annual basis overall debris covered ice ablation during the study period was observed to be 37 less than clean ice ablation strong downwasting was also observed in the dokriani glacier ablation area with average annual ablation of 1 82mw e a 1 in a similar period our study suggests that a thinning glacier rapidly becomes debris covered over the ablation area reducing the rate of ice loss

uncertainties in antarctic sea ice thickness retrieval from icesat a sensitivity study was carried out for the lowest level elevation method to retrieve total sea ice snow freeboard from ice cloud and land elevation satellite icesat elevation measurements in the weddell sea antarctica varying the percentage p of elevations used to approximate the instantaneous sea surface height can cause widespread changes of a few to 10 cm in the total freeboard obtained other input parameters have a smaller influence on the overall mean total freeboard but can cause large regional differences these results together with published icesat elevation precision and accuracy suggest that three times the mean per gridcell single laser shot error budget can be used as an estimate for freeboard uncertainty theoretical relative ice thickness uncertainty ranges between 20 and 80 for typical freeboard and snow properties ice thickness is computed from total freeboard using advanced microwave scanning radiometer for earth observing system amsr e snow depth data average ice thickness for the weddell sea is 1 73 0 38 m for icesat measurements from 2004 to 2006 in agreement with previous work the mean uncertainty is 0 72 0 09 m our comparison with data of an alternative approach which assumes that sea ice freeboard is zero and that total freeboard equals snow depth reveals an average sea ice thickness difference of 0 77 m

snow depth of the weddell and bellingshausen sea ice covers from icebridge surveys in 2010 and 2011 an examination we examine the snow radar data from the weddell and bellingshausen seas acquired by eight icebridge oib flightlines in october of 2010 and 2011 in snow depth retrieval the sidelobes from the stronger scattering snow ice s i interfaces could be misidentified as returns from the weaker air snow a s interfaces in this paper we first introduce a retrieval procedure that accounts for the structure of the radar system impulse response followed by a survey of the snow depths in the weddell and bellingshausen seas limitations and potential biases in our approach are discussed differences between snow depth estimates from a repeat survey of one weddell sea track separated by 12 days without accounting for variability due to ice motion is 0 7 13 6 cm average snow depth is thicker in coastal northwestern weddell and thins toward cape norvegia a decrease of 30 cm in the bellingshausen the thickest snow is found nearshore in both octobers and is thickest next to the abbot ice shelf snow depth is linearly related to freeboard when freeboards are low but diverge as the freeboard increases especially in the thicker rougher ice of the western weddell we find correlations of 0 71 0 84 between snow depth and surface roughness suggesting preferential accumulation over deformed ice retrievals also seem to be related to radar backscatter through surface roughness snow depths reported here generally higher than those from in situ records suggest dissimilarities in sample populations implications of these differences on antarctic sea ice thickness are discussed

glacial lake evolution and glacier lake interactions in the poiqu river basin central himalaya 1964 2017 despite previous studies glacier lake interactions and future lake development in the poiqu river basin central himalaya are still not well understood we mapped glacial lakes glaciers their frontal positions and ice flow from optical remote sensing data and calculated glacier surface elevation change from digital terrain models during 1964 2017 the total glacial lake area increased by 110 glaciers retreated with an average rate of 1 4 km 2 a 1 between 1975 and 2015 based on rapid area expansion 150 and information from previous studies eight lakes were considered to be potentially dangerous glacial lakes corresponding lake terminating glaciers showed an overall retreat of 6 0 1 4 to 26 6 1 1 m a 1 and accompanying lake expansion the regional mean glacier elevation change was 0 39 0 13 m a 1 while the glaciers associated with the eight potentially dangerous lakes lowered by 0 71 0 05 m a 1 from 1974 to 2017 the mean ice flow speed of these glaciers was 10 m a 1 from 2013 to 2017 about double the mean for the entire study area analysis of these data along with climate observations suggests that ice melting and calving processes play the dominant role in driving lake enlargement modelling of future lake development shows where new lakes might emerge and existing lakes could expand with projected glacial recession

thickness distribution of antarctic sea ice 1 ship based observations are used to describe regional and seasonal changes in the thickness distribution and characteristics of sea ice and snow cover thickness around antarctica the data set comprises 23 373 observations collected over more than 2 decades of activity and has been compiled as part of the scientific committee on antarctic research scar antarctic sea ice processes and climate aspect program the results show the seasonal progression of the ice thickness distribution for six regions around the continent together with statistics on the mean thickness surface ridging snow cover and local variability for each region and season a simple ridge model is used to calculate the total ice thickness from the observations of level ice and surface topography to provide a best estimate of the total ice mass including the ridged component the long term mean and standard deviation of total sea ice thickness including ridges is reported as 0 87 0 91 m which is 40 greater than the mean level ice thickness of 0 62 m analysis of the structure function along north south and east west transects revealed lag distances over which sea ice thickness decorrelates to be of the order of 100 300 km which we use as a basis for presenting near continuous maps of sea ice and snow cover thickness plotted on a 2 5 5 0 grid

compilation of a glacier inventory for the western himalayas from satellite data methods challenges and results abstract due to their sensitive reaction to changes in climatic conditions glaciers have been selected as an essential climate variable ecv although a large amount of ice is located in the himalayas this region is yet only sparsely represented in global glacier databases accordingly a sound and comprehensive change assessment or determination of water resources was not yet possible in this study we present a new glacier inventory for the western himalayas compiled from landsat etm scenes acquired between 2000 and 2002 coherence images from alos palsar image pairs the srtm digital elevation model dem and the aster global dem gdem several specific challenges for glacier mapping were found in this region and addressed they are related to debris cover orographic clouds locally variable snow conditions and creeping permafrost features in cold dry regions additional to seven topographic parameters that are obtained from the aster gdem for each glacier we also determined the relative amount of debris cover on the glacier surface the inventory contains 11 400 glaciers larger than 0 02 km2 which cover a total area of 9 310 km2 analysis of the inventory data revealed characteristic patterns of mean glacier elevation and relative debris cover amounts that might be related to the governing climatic conditions the full dataset will be freely available in the glims glacier database to foster further analyses and modeling of the glaciers in this region

response of debris covered glaciers in the mount everest region to recent warming and implications for outburst flood hazards abstract in areas of high relief many glaciers have extensive covers of supraglacial debris in their ablation zones which alters both rates and spatial patterns of melting with important consequences for glacier response to climate change wastage of debris covered glaciers can be associated with the formation of large moraine dammed lakes posing risk of glacier lake outburst floods glofs in this paper we use observations of glaciers in the mount everest region to present an integrated view of debris covered glacier response to climate change which helps provide a long term perspective on evolving glof risks in recent decades debris covered glaciers in the everest region have been losing mass at a mean rate of 0 32 m yr 1 although in most cases there has been little or no change in terminus position mass loss occurs by 4 main processes 1 melting of clean ice close to glacier elas 2 melting beneath surface debris 3 melting of ice cliffs and calving around the margins of supraglacial ponds and 4 calving into deep proglacial lakes modelling of processes 1 and 2 shows that everest region glaciers typically have an inverted ablation gradient in their lower reaches due to the effects of a down glacier increase in debris thickness mass loss is therefore focused in the mid parts of glacier ablation zones causing localised surface lowering and a reduction in downglacier surface gradient which in turn reduce driving stress and glacier velocity so the lower ablation zones of many glaciers are now stagnant model results also indicate that increased summer temperatures have raised the altitude of the rain snow transition during the summer monsoon period reducing snow accumulation and ice flux to lower elevations as downwasting proceeds formerly efficient supraglacial and englacial drainage networks are broken up and supraglacial lakes form in hollows on the glacier surface ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub debris melt rates so extensive lake formation accelerates overall rates of ice loss most supraglacial lakes are perched above hydrological base level and are susceptible to drainage if they become connected to the englacial drainage system speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre existing weaknesses in the ice roof collapses can open these voids up to the surface and commonly provide the nuclei of new lakes thus by influencing both lake drainage and formation englacial conduits exert a strong control on surface ablation rates an important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier base level lakes formed behind intact moraine dams can grow monotonically and in some cases can pose serious glof hazards glacier termini can evolve in different ways in response to the same climatic forcing so that potentially hazardous lakes will form in some situations but not others additionally the probability of a flood is not simply a function of lake volume but depends on the geometry and structure of the dam and possible trigger mechanisms such as ice or rockfalls into the lake satellite based measurements of glacier surface gradient and ice velocities allow probable future locations of base level lakes to be identified a base level lake has begun to grow rapidly on ngozumpa glacier west of mount everest and could attain a volume of 10 8 m 3 within the next 2 or 3 decades unless mitigation efforts are undertaken this lake could pose considerable glof hazard potential

estimation of the recession rate of gangotri glacier garhwal himalaya india through kinematic gps survey and satellite data snout monitoring of the gangotri glacier uttarakhand india during the ablation season may to september in years 2005 and 2015 by using rapid static and kinematic gps survey reveals that the retreating rate has been comparatively more declined than shown by the earlier studies our study is based on the individual measurement by the remote sensing added by the ground observations by using differential global positioning system dgps to determine the precise recession rate of the glacier at sub centimeter level of accuracy the gps dataset show that the total average retreat along the snout has been 102 57 0 05 m from 2005 to 2015 with an average rate as 10 26 0 05 m yr additionally the shift in snout position was also measured through multi temporal satellite data from 1989 to 2016 the results indicate that the gangotri glacier snout has retreated by 585 62 38 30 m during this period with an average retreat of 26 75 4 36 m yr from 1989 to 1999 21 58 3 77 m yr from 1999 to 2009 and 14 60 4 81 m yr from 2009 to 2016 such a decline in retreat is further confirmed by the satellite data set a close examination of meltwater discharge and retreating rate r2 0 95 show that both parameters are strongly correlated therefore we suggest that a consistent decrease in meltwater discharge from 1999 to 2015 is in agreement with decreasing trend of retreating rate during the recent years to determine the possible causes of decreased retreating rate a relationship between debris thickness and melt rate was also established by ablation stakes further we infer that the declining trend in the glacier retreat is not only controlled by prevailing weather conditions rainfall and air temperature but is also governed by increased debris cover on the glacier surface which prevents the ice to melt

satellite remote sensing of sea ice thickness and kinematics a review observations of sea ice thickness and kinematics are essential for understanding changes in sea ice mass balance interactions between the ice cover and the ocean and atmosphere and for improving projections of sea ice response in a warming climate these parameters are not directly observable with current sensor technology but are derived from satellite altimetry and imagery while there is progress in the retrievals of arctic sea ice thickness from satellite altimetry approaches to address southern ocean ice thickness require additional attention on the other hand procedures to derive sea ice motion from satellite imagery are more mature and better understood and have been employed to produce useful results for more than a decade adequate sampling of sub daily ice motion however remains a challenge generally satellite instruments provide large scale coverage but the frequency of temporal sampling is limited by orbit characteristics in this review i focus on the approaches uncertainties sampling limitations and validation issues associated with the estimation of sea ice thickness and motion i provide a summary of current and anticipated capabilities for monitoring sea ice thickness and kinematics from space the prospects for continuing these measurements into the next decade from a satellite remote sensing perspective are discussed

role of off shelf to on shelf transitions for east antarctic sea ice dynamics during spring 2003 1 during austral spring 2003 mesoscale sea ice drift and deformation off east antarctica were investigated using in situ data from a nine buoy array upon deployment the array comprised an area of about 4000 km2 with a mean ice concentration of 96 half hourly sea ice velocities were coherent across all buoys at zonal meridional separations of less than 160 km 70 km regional cross spectral correlation was high at synoptic scales and also at semidiurnal periods off the continental shelf atmospheric synoptic scale forcing explained in excess of 85 of the ice drift variability this is significantly more than found in the weddell sea where significant ice drift variability is derived from oceanic forcing peak frequencies of semidiurnal contributions covaried with latitude and are largely associated with the inertial response over the continental shelf coincident diurnal and semidiurnal variances in ice motion arose from tidal forcing net divergence over 37 days resulted in an expansion to 270 of the initial area although regional ice concentration reduced only slightly high frequency processes namely inertial response and to a lesser degree tidal forcing dominated the variability of all deformation parameters in contrast to ice motion low frequency processes played a secondary role in sea ice deformation this high frequency dominance is similar to what has been found in the weddell sea although many observations there were limited to the continental shelf where tidal processes dominate sea ice motion and deformation were not affected by a seasonal transition nor did the regional ice characteristics show any signal of seasonal change instead local ice dynamics were strongly influenced by bathymetrically dependent processes

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

glacier changes in the koshi river basin central himalaya from 1976 to 2009 derived from remote sensing imagery we use remote sensing and gis technologies to monitor glacier changes in the koshi river basin central himalaya the results indicate that in 2009 there were 2061 glaciers in this region with a total area of 3225 90 3 km 2 this glacier population is divided into 1290 glaciers with a total area of 1961 54 9 km 2 on the north side of the himalaya nsh and 771 glaciers with a total area of 1264 35 4 km 2 on the south side of the himalaya ssh from 1976 to 2009 glacier area in the basin decreased by about 19 5 6 0 59 0 17 a 1 glacier reduction was slightly faster on ssh 20 3 5 6 than on nsh 18 8 5 6 the maximum contribution to glacier area loss came from glaciers within the 1 5 km 2 area interval which accounted for 32 of total area loss between 1976 and 2009 the number of glaciers in the koshi river catchment decreased by 145 between 1976 and 2009 glacier area on ssh decreased at a rate of 6 2 3 2 0 68 0 36 a 1 faster than on nsh where the rate was 2 5 3 2 0 27 0 36 a 1 during 2000 09 based on records from tingri weather station we infer that temperature increase and precipitation decrease were the main causes of glacier thinning and retreat during the 1976 2000 period glacier retreat during the 2000 09 period appears to be controlled by temperature increase since precipitation increase over this period did not offset ice losses to surface melting

classification of debris covered glaciers and rock glaciers in the andes of central chile in the dry andes of chile 17 to 35 s debris covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover thickness of surface debris and ice content internal ice is preserved by an insulating cover of thick debris which acts as a storage reservoir to release water during the summer and early fall these landforms are more numerous than glaciers in the central andes however the existing legislation only recognizes uncovered or semicovered glaciers as a water resource glaciers debris covered glaciers and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains in addition agricultural expansion and population growth in this region have placed additional demands on water resources in a warmer climate as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season rock glaciers and debris covered glaciers contribute a larger component of base flow to rivers and streams as a result identifying and locating these features to implement sustainable regional planning for water resources is important the objective of this study is to develop a classification system to identify debris covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs the classification system is linked to field observations and measurements of ice content debris covered glaciers have three subclasses surface coverage of semi class 1 and fully covered class 2 glaciers differentiates the first two forms whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris based on field observations the amount of ice decreases from more than 85 to 65 85 to 45 65 for semi fully and buried debris covered glaciers respectively rock glaciers are characterized by three stages class 4 rock glaciers have pronounced transverse ridges and furrows that arch across the surface which indicates flow produced via ice class 5 rock glaciers have ridges and furrows that appear linear in the direction of flow indicating reduced flow from limited internal ice and class 6 rock glaciers have subdued surface topography because the movement of the rock glacier has ceased ice content decreases from 25 45 to 10 25 to 10 from class 4 to 6 respectively examples from digital imagery aerial photographs and field photographs are provided for each class the classification scheme can be used to identify and map debris covered glaciers and rock glaciers to create an inventory this will help improve recognition of these landforms as an important water resource in the dry andes of chile which will aid in sustainable planning and development in basins that hold the majority of the population and support a large share of the economic activity in chile

slopes of p to s wave spectral ratios a broadband regional seismic discriminant and a physical model concerns about nuclear proliferation and negotiations toward a comprehensive test ban treaty ctbt emphasize the need for robust seismic monitoring and regional discrimination capabilities especially at low magnitudes standard regional discrimination techniques have many shortcomings for example they cannot always discriminate shallow low magnitude earthquakes or mining related events i show that slopes of p to s wave spectral ratios can be used to discriminate shallow and normal depth earthquakes from explosions and possibly to discriminate explosions from mining related rockburst or collapse events p to s wave slopes and conventional high frequency p to s wave spectral amplitude ratios discriminate even better in combination than alone a comparison of pn and lg spectra from nevada test site nts explosions and earthquakes shows that this method discriminates concentrated explosions from earthquakes and other shallow seismic events such as mine collapses because s waves from explosions decay more rapidly at high frequencies than do s waves from earthquakes spectra of one dimensional reflectivity synthetic seismograms show that frequency dependent attenuation of explosion generated p to s wave converted phases in the near surface layers may be responsible for the differences in lg s wave spectral falloff these simulations also show that absolute amplitudes of earthquake p to s wave spectral ratios are very sensitive to mechanism and depth which may help explain the variable performance of conventional methods

a new glacier inventory on southern baffin island canada from aster data ii data analysis glacier change and applications despite its large area covered by glaciers and ice caps detailed glacier inventory data are not yet available for most parts of baffin island canada automated classification of satellite data could help to overcome the data gaps along track stereo sensors allow the derivation of a digital elevation model dem and glacier outlines from the same point in time and are particularly useful for this task while part i of this study describes the remote sensing methods in part ii we present an analysis of the derived glacier inventory data for 662 glaciers and an application to glacier volume and volume change calculations among other things the analysis reveals a mean glacier elevation of 990 m with a weak dependence on aspect and a close agreement of the arithmetic mean with the statistical mean elevation as derived from the dem a strong scatter of mean slope is observed for glaciers 1 km2 and the derived glacier thickness differs by a factor of two for glaciers of the same size for the period from about 1920 to 2000 the relative area change is 12 5 264 glaciers with a strong dependence on glacier size mean mass loss as derived from volume changes is about 0 15mw e a 1

microwave signatures of snow on sea ice observations part of the earth observing system aqua advanced microwave scanning radiometer amsr e arctic sea ice validation campaign in march 2003 was dedicated to the validation of snow depth on sea ice and ice temperature products the difficulty with validating these two variables is that neither can currently be measured other than in situ for this reason two aircraft flights on march 13 and 19 2003 were dedicated to these products and flight lines were coordinated with in situ measurements of snow and sea ice physical properties one flight was in the vicinity of barrow ak covering elson lagoon and the adjacent chukchi and beaufort seas the other flight was farther north in the beaufort sea about 73degn 147 5degw and was coordinated with a navy ice camp the results confirm the amsr e snow depth algorithm and its coefficients for first year ice when it is relatively smooth for rough first year ice and for multiyear ice there is still a relationship between the spectral gradient ratio of 19 and 37 ghz but a different set of algorithm coefficients is necessary comparisons using other amsr e channels did not provide a clear signature of sea ice characteristics and hence could not provide guidance for the choice of algorithm coefficients the limited comparison of in situ snow ice interface and surface temperatures with 6 ghz brightness temperatures which are used for the retrieval of ice temperature shows that the 6 ghz temperature is correlated with the snow ice interface temperature to only a limited extent for strong temperature gradients within the snow layer it is clear that the 6 ghz temperature is a weighted average of the entire snow layer

analysis of high frequency pg lg ratios from nts explosions and western u s earthquakes the high frequency pg lg discriminant is studied between frequencies of 0 5 and 10 hz using 294 nts explosions and 114 western u s earthquakes recorded at four broadband seismic stations operated by lawrence livermore national laboratory the stations are located at distances of about 200 to 400 km from the nevada test site nts event magnitudes ranged from about 2 5 to 6 5 and propagation paths for the earthquakes range from approximately 175 to 1300 km the discriminant is shown to be very effective and displays improved separation between earthquakes and explosions as frequency is increased because of propagation effects it is important to apply distance corrections directly to the amplitude ratios or to the magnitude corrected amplitudes prior to computing the ratios multivariate discrimination analysis using both maximum likelihood gaussian classifiers and a backpropagation neural network show that approximately 95 of the events can be correctly identified both classification procedures were designed to handle missing data filled in using a nearest neighbor algorithm except for a few notable exceptions most of the earthquake misclassifications occur for mb 4 which is expected for events having reduced signal to noise ratios all of the explosion misclassifications occur for mb 4 suggesting a source or near source effect rather than an effect of poor signal to noise ratio the explosions that were misclassified were typically of magnitude large enough to be classified correctly by mb ms or love wave energy the main drawback of the pg lg discriminant is that because of signal to noise considerations and propagation effects the number of measurements are reduced considerably at higher frequencies it is expected that the problem will be amplified as magnitudes are reduced and event receiver distances are increased

estimating small scale snow depth and ice thickness from total freeboard for east antarctic sea ice abstract deriving the snow depth on antarctic sea ice is a key factor in estimating sea ice thickness distributions from space or airborne altimeters using a linear regression to model snow depth from observed total freeboard or the snow ice surface elevation relative to sea level is an efficient and promising method for the estimation of snow depth for instruments which only detect the uppermost surface of the sea ice conglomerate e g laser altimetry however the antarctic pack ice zone is subject to substantial variability due to synoptic scale weather forcing ice formation motion and melt undergo large spatio temporal variability throughout the year in this paper we estimate snow depth from total freeboard for the arise 2003 sipex 2007 and sipex ii 2012 research voyages to the east antarctic pack ice zone using in situ data we investigate variability in snow depth and show that for east antarctica relationships between snow depth and total freeboard vary between each voyage at a resolution of metres to tens of metres we show how regression based snow depth models track total freeboard and generally over estimate snow depth especially on highly deformed sea ice and at sites where ice freeboard makes a substantial contribution to total freeboard for a set of 3192 records we obtain an in situ mean snow depth of 0 21 m 0 19 m using a regression model derived from all in situ points we obtain the same mean with a slightly lower variability 0 16 m using voyage specific subsets of the data to derive regression models and estimate snow depth mean snow depths ranged from 0 19 m model derived from sipex observations to 0 25 m model derived from sipex ii observations while small these discrepancies impact ice thickness estimation using the assumption of hydrostatic equilibrium mean in situ ice thickness for all samples is 1 44 m 1 19 m using empirical models for snow depth ice thickness varies from 1 0 to 1 8 m with the best match to the in situ mean given when snow depth is derived using a snow depth model from all observations 1 53 m 1 55 m however mean values only tell part of the story when investigating the sea ice thickness distribution here we explicitly show how modelling snow depth and ice thickness based on a total freeboard signal compares with in situ observations this provides insight into the confidence we place in ice thickness distributions derived using a total freeboard signal and empirically derived models for snow depth

18o concentrations in sea ice of the weddell sea antarctica we present data on ice texture salinity and delta o 18 obtained from identical sections of ice cores during the winter weddell sea project 1986 on rv polarstern from july through august 1986 in the longitude range between 5 degrees w and 7 degrees e we find no uniquely definable relationship between delta o 18 values and ice texture in a particular section however most of the snow ice as well as some sections of frazil ice ar found to have negative delta o 18 concentrations this is due to varying degrees of admixtures of meteoric ice snow and sea water during formation of snow ice in contrast to common assumptions our results seem to indicate that a snow cover contributes positively to sea ice growth rather than slowing down the overall growth rate based on a simple model we have estimated the contributions of meteoric ice mean of 3 3 and the combined meteoric ice sea water fraction a minimum of 7 6 to the total ice thickness for the majority of the sampled floes although this is only a moderate contribution to the overall mass balance in the absence of congelation growth it nevertheless enhances ice growth in general this hypothesis is dependently supported by our snow and ice thickness data wadhams and others 1987 which demonstrate that the depression of the snow ice interface below the water line i e a negative freeboard and the formation of snow ice is a common occurrence in the weddell sea therefore we hypothesize that the major part of the observed apparent increase in ice thickness between our inbound and outbound tracks of wwsp 86 may not be derived from regular thermodynamically driven congelation growth but rather from the snow ice component in floes of the weddell sea

a quantitative study of the site effects observed at the geress array site effects were studied for the individual sites of the 25 elements of the german experimental seismic system geress array based on the traditional spectral ratio tsr technique and horizontal to vertical ratios hvrs for earthquakes and microtremors commonly referred to as nakamura9s technique an understanding of these site effects is required for various applications in particular for the discrimination of seismic events the spectral ratio technique identifies three stations a0 a3 b3 as showing prominent peaks in the frequency band from 1 to 17 hz up to a factor of 30 with a0 and b3 having the largest site effect at a frequency of 7 hz these stations are situated in the immediate vicinity of the array center a number of other stations such as a1 b1 b4 b5 c1 c3 c5 d2 d5 and d7 d9 display a broad frequency range preferably above 10 hz where the spectral ratios indicate up to 10 times higher spectral amplitudes compared to the reference site c2 the remaining stations a2 b2 c6 c7 d1 d3 d4 and d6 show no noticeable site effects further study considers the appropriateness for the selection of c2 as reference site for the tsr technique and the comparison of tsr and hvr techniques for the three component elements of the array although typically site response refers to the site amplification of horizontal ground motions the assessed site response of vertical ground motions seems to yield comparable results the spectral variance a parameter based on the smoothness of stacked array spectra from the best 17 array elements of the geress array has been used successfully to distinguish between local earthquakes and mining explosions it is shown that the spectral variance estimate is considerably improved using all 25 array elements and applying a site response correction

icesat observations of seasonal and interannual variations of sea ice freeboard and estimated thickness in the weddell sea antarctica 2003 2009 sea ice freeboard heights for 17 icesat campaign periods from 2003 to 2009 are derived from icesat data freeboard is combined with snow depth from advanced microwave scanning radiometer for earth observing system amsr e data and nominal densities of snow water and sea ice to estimate sea ice thickness sea ice freeboard and thickness distributions show clear seasonal variations that reflect the yearly cycle of growth and decay of the weddell sea antarctica pack ice during october november sea ice grows to its seasonal maximum both in area and thickness the mean freeboards are 0 33 0 41 m and the mean thicknesses are 2 10 2 59 m during february march thinner sea ice melts away and the sea ice pack is mainly distributed in the west weddell sea the mean freeboards are 0 35 0 46 m and the mean thicknesses are 1 48 1 94 m during may june the mean freeboards and thicknesses are 0 26 0 29 m and 1 32 1 37 m respectively the 6 year trends in sea ice extent and volume are 0 023 0 051 x 10 exp 6 sq km a 0 45 a and 0 007 1 0 092 x 10 exp 3 cu km a 0 08 a however the large standard deviations indicate that these positive trends are not statistically significant

icesat over arctic sea ice interpretation of altimetric and reflectivity profiles 1 we provide an assessment of the icesat altimeter for studying the arctic ocean and examine the magnitude of the large and small scale expressions of geophysical processes embedded in the elevation profiles this analysis includes data from six surveys at the large scale the response of the ice covered ocean to atmospheric loading is near ideal i e approximately 1 cm hpa after removal of the inverted barometer effects and best available geoid the elevation signal is still dominated by unresolved geoid residuals 0 4 m that can be seen in the similarity of the remaining spatial patterns seasonal differences in elevations over multiyear ice are consistent with snow depth climatology the broad differential spatial patterns are indicative of interannual differences in multiyear ice coverage associated with advection patterns in the derived surface roughness fields correspond to the seasonal and perennial ice zones seen in quikscat data at the small scale near coincident radarsat imagery provides a spatial context for understanding the signature of the observed elevations waveforms and reflectivity in particular those associated with thin ice open water multiyear ice and ridges the precision of the elevation estimates measured over relatively flat sea ice identified in synthetic aperture radar sar imagery is 2 cm the unambiguous identification of ridged areas in coupled icesat radarsat analysis could be used to enhance the utility of sar imagery for examining ridge distributions over a 20 day period we monitored the evolution of the reflectivity of a newly opened lead the steep increase in reflectivity due to snow coverage suggests that dips in icesat reflectivity are likely areas of thin ice and could serve as a basis for selection of tie points for use as sea level reference identification of these tie points is crucial for accurate estimation of sea ice freeboard

intercomparisons of antarctic sea ice types from visual ship radarsat 1 sar envisat asar quikscat and amsr e satellite observations in the bellingshausen sea abstract antarctic sea ice processes and climate aspect visual ship based observations were conducted in the bellingshausen sea during the sea ice mass balance in the antarctic simba cruise in austral spring 2007 a total of 59 aspect observations are compared to coincident satellite active and passive microwave data envisat and radarsat 1 c band hh polarization radar backscatter values called nrcs henceforth are derived on km scales for six individual ice types and ice type mixtures c band hh polarized and ku band vv polarized nrcs are extracted on several 10 km scale areas from coincident envisat radarsat 1 and quikscat radar images for areas primarily covered with multiyear deformed first year and undeformed young ice as well as ice of the marginal ice zone miz the c band nrcs permits distinction between first year miz and undeformed young ice however nrcs of the multiyear ice zone overlaps with that of the other ice zones and types ku band nrcs obtained for the same ice types permits discrimination of the first year ice zone only obtained nrcs agree with those of previous studies and suggest a high degree of deformation and considerable potential for flooding for the first year ice case in comparison to large scale nrcs amsr e snow depth values form two clearly separated clusters one for 0 24 0 35 m depth first year ice zone and one for 0 36 0 54 m depth multiyear ice zone however a comparison to aspect observations suggests a remarkable underestimation of the snow depth by amsr e in the multiyear first year ice transition zone and for first year cake ice nevertheless a fusion of the coarse amsr e snow depth ranges for interior pack ice regions with radar imagery at large scale appears promising for mapping the major zones miz and pack ice and ice types first year and multiyear of antarctic sea ice on a circumpolar basis

evaluation of amsr e snow depth product over east antarctic sea ice using in situ measurements and aerial photography 1 the antarctic remote ice sensing experiment arise was conducted in the east antarctic sea ice zone during september october 2003 a key objective of this program was the acquisition of in situ measurements suitable for evaluating the eos aqua advanced microwave scanning radiometer amsr e snow depth product a strategy is presented for comparing snow thickness measurements over spatial scales ranging from point measurements to satellite pixels in situ measurements of snow thickness were taken across eight lagrangian grid cells defined and tracked using an array of drifting buoys these data are coupled with ice type analyses from digital aerial photographs to calculate area averaged snow thicknesses that are compared with the amsr e derived snow thickness product the results show considerable underestimates of the amsr e snow depths for rough sea ice by a factor of 2 3 we investigate the impact of underlying sea ice roughness on snow depth retrievals and conclude that in situ measurements of snow thickness underrepresent snow depth over rough ice which is then not adequately accounted for in the development of the algorithm coefficients

freeboard snow depth and sea ice roughness in east antarctica from in situ and multiple satellite data in october 2003 a campaign on board the australian icebreaker aurora australis had the objective to validate standard aqua advanced microwave scanning radiometer amsr e sea ice products additionally the satellite laser altimeter on the ice cloud and land elevation satellite icesat was in operation to capture the large scale information on the sea ice conditions necessary for satellite validation the measurement strategy was to obtain large scale sea ice statistics using extensive sea ice measurements in a lagrangian approach a drifting buoy array spanning initially 50 km x 100 km was surveyed during the campaign in situ measurements consisted of 12 transects 50 500 m with detailed snow and ice measurements as well as random snow depth sampling of floes within the buoy array using helicopters in order to increase the amount of coincident in situ and satellite data an approach has been developed to extrapolate measurements in time and in space assuming no change in snow depth and freeboard occurred during the period of the campaign on the floes surveyed we use buoy ice drift information as well as daily estimates of thin ice fraction and rough ice vs smooth ice fractions from amsr e and quikscat respectively to estimate kilometer scale snow depth and freeboard for other days the results show that icesat freeboard estimates have a mean difference of 1 8 cm when compared with the in situ data and a correlation coefficient of 0 6 furthermore incorporating icesat roughness information into the amsr e snow depth algorithm significantly improves snow depth retrievals snow depth retrievals using a combination of amsr e and icesat data agree with in situ data with a mean difference of 2 3 cm and a correlation coefficient of 0 84 with a negligible bias

spatial variability of barrow area shore fast sea ice and its relationships to passive microwave emissivity aircraft acquired passive microwave data laser radar height observations radarsat synthetic aperture radar imagery and in situ measurements obtained during the amsr ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales the data fusion allows delineation of the shore fast ice and pack ice in the barrow area ak into several ice classes results show good agreement between observed and polarimetric scanning radiometer psr derived snow depths over relatively smooth ice with larger differences over ridged and rubbled ice the psr results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness ridging and other factors such as ice age apparent relationships exist between ice roughness and the degree of depolarization of emission at 10 19 and 37 ghz this depolarization would yield overestimates of total ice concentration using polarization based algorithms with indications of this seen when the nt 2 algorithm is applied to the psr data other characteristics of the microwave data such as effects of grounding of sea ice and large contrast between sea ice and adjacent land are also apparent in the psr data overall the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity

identification of earthquakes and explosions using amplitude ratios the vogtland area revisited identification of seismic events is a major scientific issue in the framework of verification of the comprehensive nuclear test ban treaty ctbt of special interest in this context is the identification of the numerous low yield mining or blasting events especially those occurring in the same area as earthquakes such as the vogtland area in the border region of germany and the czech republic seismic events in this area were investigated by wuster 1993 1995 who achieved complete discrimination using measures of spectral decay and spectral variance at the geress array and a quadratic discrimination function

mass balance changes of the debris covered glaciers in the langtang himal nepal from 1974 to 1999 thick debris cover on glaciers can significantly reduce ice melt however several studies have suggested that debris covered glaciers in the himalaya might have lost mass at a rate similar to debris free glaciers we reconstruct elevation and mass changes for the debris covered glaciers of the upper langtang valley nepalese himalaya using a digital elevation model dem from 1974 stereo hexagon satellite data and the 2000 srtm shuttle radar topography mission dem uncertainties are high in the accumulation areas due to data gaps in the srtm and difficulties with delineation of the glacier borders even with these uncertainties we obtain thinning rates comparable to those of several other studies in the himalaya in particular we obtain a total mass balance for the investigated debris covered glaciers of the basin of 0 32 0 18 m w e a 1 however there are major spatial differences both between glaciers and within any single glacier exhibiting a very distinct nonlinear mass balance profile with elevation through analysis of surface velocities derived from landsat etm imagery we show that thinning occurs in areas of low velocity and low slope these areas are prone to a general dynamic decay of surface features and to the development of supraglacial lakes and ice cliffs which may be responsible for a considerable increase in overall glacier ablation

a new glacier inventory for the svartisen region norway from landsat etm data challenges and change assessment glaciers are widely recognized as key indicators of climate change and their meltwater plays an important role in hydropower production in norway since the last glacier inventory was compiled in northern norway in the 1970s marked fluctuations in glacier length and mass balance have been reported for individual glaciers and the current overall glacier state is thus not well known within the framework of the global land ice measurements from space glims initiative we have created a new inventory for 489 glaciers in the svartisen region northern norway using a landsat enhanced thematic mapper plus etm satellite scene from 7 september 1999 and automated multispectral glacier mapping thresholded band ratios in addition visual inspection and correction of the generated glacier outlines has been applied adverse snow conditions and uncertain drainage divides made glacier mapping challenging in some regions of the study site glacier outlines from 1968 as digitized from a topographic map were used for a quantitative change assessment for a selection of 300 glaciers the overall area change of this sample from 1968 to 1999 was close to zero but with a strongly increasing scatter towards smaller glaciers large area gains 50 for small glaciers 1 km 2 and an unexpected stronger relative area loss towards the wetter coast the overall size changes are small 1 for the three largest ice masses in the study region vestisen ostisen and blamannsisen

glacier area changes in the pumqu river basin tibetan plateau between the 1970s and 2001 glacier area changes in the pumqu river basin tibetan plateau between the 1970s and 2001 are analyzed based on the chinese glacier inventory and aster images a new glacier inventory is obtained by visually interpreting the remote sensing images and the digital elevation model by comparing the two inventories glacier area changes over the past 30 years are revealed the results show that the area loss is about 9 0 and the shrinkage trend continues according to the meteorological data

retreat rates of debris covered and debris free glaciers in the koshi river basin central himalayas from 1975 to 2010 debris covered glaciers are common in the himalayas and play a key role in understanding future regional water availability and management previous studies of regional glacial changes have often neglected debris covered glaciers or have mixed them with debris free glaciers in this study we generated a new glacier data set that includes debris covered and debris free glaciers to study the glacial surface area change in the koshi river basin in the central himalayas long time series landsat data were used to extract the glacier boundaries using automatic and manual classification methods the glacial area decreased by 10 4 from 1975 to 2010 at a rate of 0 30 a 1 with accelerated melting since 2000 0 47 a 1 small glaciers melted faster than large glaciers in terms of distinctive glacier types debris free glaciers shrank at a rate of 0 45 a 1 faster than debris covered glaciers 0 18 a 1 while debris covered glaciers larger than 5 0 km2 retreated at a rate faster than debris free glaciers of the same sized group we also studied the potential interactions between 222 supraglacial lakes and debris covered glaciers debris covered glaciers with glacial lakes melt faster than glaciers without lakes this study can improve our understanding of the differences in the changes between debris covered and debris free glaciers in the central himalayas and help evaluate water resource changes in the himalayas

glacier change 1958 1998 in the north cascades national park complex washington usa the spatial characteristics for all glaciers in the north cascades national park complex usa were estimated in 1958 and again in 1998 the total glacier area in 1958 was 117 3 1 1 km 2 by 1998 the glacier area had decreased to 109 1 1 1 km 2 a reduction of 8 2 0 1 km 2 7 estimated volume loss during the 40 year period was 0 8 0 1 km 3 of ice this volume loss contributes up to 6 of the august september stream flow and equals 16 of the august september precipitation no significant correlations were found between magnitude of glacier shrinkage and topographic characteristics of elevation aspect or slope however the smaller glaciers lost proportionally more area than the larger glaciers and had a greater variability in fractional change than larger glaciers most of the well studied alpine glaciers are much larger than the population median so global estimates of glacier shrinkage based on these well studied glaciers probably underestimate the true magnitude of regional glacier change

a grid based model of backwasting of supraglacial ice cliffs on debris covered glaciers ice cliffs might be partly responsible for the high mass losses of debris covered glaciers in the hindu kush karakoram himalaya region the few existing models of cliff backwasting are point scale models applied at few locations or assume cliffs to be planes with constant slope and aspect a major simplification given the complex surfaces of most cliffs we develop the first grid based model of cliff backwasting for two cliffs on debris covered lirung glacier nepal the model includes an improved representation of shortwave and longwave radiation and their interplay with the glacier topography shortwave radiation varies considerably across the two cliffs mostly due to direct radiation diffuse radiation is the major shortwave component as the direct component is strongly reduced by the cliffs aspect and slope through self shading incoming longwave radiation is higher than the total incoming shortwave flux due to radiation emitted by the surrounding terrain which is 25 of the incoming flux melt is highly variable in space suggesting that simple models provide inaccurate estimates of total melt volumes although only representing 0 09 of the glacier tongue area the total melt at the two cliffs over the measurement period is 2313 and 8282 m3 1 23 of the total melt simulated by a glacio hydrological model for the glacier s tongue

validation of airborne fmcw radar measurements of snow thickness over sea ice in antarctica antarctic sea ice and its snow cover are integral components of the global climate system yet many aspects of their vertical dimensions are poorly understood making their representation in global climate models poor remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover reliable and accurate snow thickness data are currently a highly sought after data product remotely sensed snow thickness measurements can provide an indication of precipitation levels predicted to increase with effects of climate change in the polar regions airborne techniques provide a means for regional scale estimation of snow depth and distribution accurate regional scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates the airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques this is primarily due to two factors better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas a 2 8 ghz frequency modulated continuous wave fmcw radar loaned by the center for remote sensing of ice sheets to the australian antarctic division is used to measure snow thickness over sea ice in east antarctica provided with the radar design parameters the expected performance parameters of the radar are summarized the necessary conditions for unambiguous identification of the air snow and snow ice layers for the radar are presented roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar finally this paper presents the first in situ validated snow thickness estimates over sea ice in antarctica derived from an fmcw radar on a helicopterborne platform

modelling ice cliff backwasting on a debris covered glacier in the nepalese himalaya ice cliffs have been identified as a reason for higher ablation rates on debris covered glaciers than are implied by the insulation effects of the debris this study aims to improve our understanding of cliff backwasting and the role of radiative fluxes in particular an energy balance model is forced with new data gathered in may and october 2013 on lirung glacier nepalese himalaya observations show substantial variability in melt between cliffs between locations on any cliff and between seasons using a high resolution digital elevation model we calculate longwave fluxes incident to the cliff from surrounding terrain and include the effect of local shading on shortwave radiation this is an advance over previous studies that made simplified assumptions on cliff geometry and radiative fluxes measured melt rates varied between 3 25 and 8 6cm d 1 in may and 0 18 and 1 34 cmd 1 in october model results reproduce the strong variability in space and time suggesting considerable differences in radiative fluxes over one cliff in october the model fails to reproduce stake readings probably due to the lack of a refreezing component disregarding local topography can lead to overestimation of melt at the point scale by up to 9

heterogeneous influence of glacier morphology on the mass balance variability in high mountain asia we investigate the control of the morphological variables on the 2000 2016 glacier wide mass balances of 6 470 individual glaciers of high mountain asia we separate the data set into 12 regions assumed to be climatically homogeneous we find that the slope of the glacier tongue mean glacier elevation percentage of supraglacial debris cover and avalanche contributing area all together explain a maximum of 48 and a minimum of 8 of the glacier wide mass balance variability within a given region the best predictors of the glacier wide mass balance are the slope of the glacier tongue and the mean glacier elevation for most regions with the notable exception of the inner tibetan plateau glacier wide mass balances do not differ significantly between debris free and debris covered glaciers in 7 of the 12 regions analyzed lake terminating glaciers have more negative mass balances than the regional averages the influence of lakes being stronger on small glaciers than on large glaciers

classification of local and regional events in central europe based on estimates of s wave spectral variance summary the vogtland region in the border region of germany and the czech republic is of special interest for the identification of seismic events on a local and regional scale since both earthquakes and explosions occur frequently in the same area and thus are relevant for discrimination research for verification of the comprehensive nuclear test ban treaty previous research on event discrimination using spectral decay and variance from data recorded by the geress array indicated that spectral variance determined for the s phase for the seismic events in the vogtland region seems to be the most promising parameter for event discrimination because this parameter provides for almost complete separation of the earthquake and explosion populations almost the entire set of vogtland events used in this research and more than 3000 local events detected in germany in 1998 and 1999 were analysed to determine spectral slopes and variance for the p and s wave windows from stacked spectra of recordings at the geress array the results suggest that small values for the spectral variance are associated not only with earthquakes in the vogtland region but also with earthquakes in other parts of germany and neighbouring countries while mining blasts show larger spectral variance values mininginduced events yield a wide range of values for example in the lubin area a threshold based identification scheme was applied almost all events classified as earthquakes are found in seismically active regions while the earthquakes are uniformly distributed throughout the day events classified as explosions correlate with normal working hours which is when blasting is done in germany in this study spectral variance provides good event discrimination for events in other parts of germany not only for the vogtland region showing that this identification parameter may be transported to other geological regions

properties of snow overlying the sea ice off east antarctica in late winter 2007 abstract the properties of snow on east antarctic sea ice off wilkes land were examined during the sea ice physics and ecosystem experiment sipex in late winter of 2007 focusing on the interaction with sea ice this observation includes 11 transect lines for the measurement of ice thickness freeboard and snow depth 50 snow pits on 13 ice floes and diurnal variation of surface heat flux on three ice floes the detailed profiling of topography along the transects and the d18o salinity and density datasets of snow made it possible to examine the snow sea ice interaction quantitatively for the first time in this area in general the snow displayed significant heterogeneity in types thickness mean 0 14 0 13 m and density 325 38 kg m 3 as reported in other east antarctic regions high salinity was confined to the lowest 0 1 m salinity and d18o data within this layer revealed that saline water originated from the surface brine of sea ice in 20 of the total sites and from seawater in 80 from the vertical profiles of snow density bulk thermal conductivity of snow was estimated as 0 15 w k 1 m 1 on average only half of the value used for numerical sea ice models although the upward heat flux within snow estimated with this value was significantly lower than that within ice it turned out that a higher value of thermal conductivity 0 3 to 0 4 w k 1 m 1 is preferable for estimating ice growth amount in current numerical models diurnal measurements showed that upward conductive heat flux within the snow and net long wave radiation at the surface seem to play important roles in the formation of snow ice from slush the detailed surface topography allowed us to compare the air ice drag coefficients of ice and snow surfaces under neutral conditions and to examine the possibility of the retrieval of ice thickness distribution from satellite remote sensing it was found that overall snow cover works to enhance the surface roughness of sea ice rather than moderate it and increases the drag coefficient by about 10 as for thickness retrieval mean ice thickness had a higher correlation with ice surface roughness than mean freeboard or surface elevation which indicates the potential usefulness of satellite l band sar in estimating the ice thickness distribution in the seasonal sea ice zone

timing and regional patterns of snowmelt on antarctic sea ice from passive microwave satellite observations an improved understanding of the temporal variability and the spatial distribution of snowmelt on antarctic sea ice is crucial to better quantify atmosphere ice ocean interactions in particular sea ice mass and energy budgets it is therefore important to understand the mechanisms that drive snowmelt both at different times of the year and in different regions around antarctica in this study we combine diurnal brightness temperature differences dtb 37ghz and ratios tb 19ghz tb 37ghz to detect and classify snowmelt processes we distinguish temporary snowmelt from continuous snowmelt to characterize dominant melt patterns for different antarctic sea ice regions from 1988 89 to 2014 15 our results indicate four characteristic melt types on average 38 9 6 0 of all detected melt events are diurnal freeze thaw cycles in the surface snow layer characteristic of temporary melt type a less than 2 reveal immediate continuous snowmelt throughout the snowpack i e strong melt over a period of several days type b in 11 7 4 0 type a and b take place consecutively type c and for 47 8 6 8 no surface melt is observed at all type d continuous snowmelt is primarily observed in the outflow of the weddell gyre and in the northern ross sea usually 17 days after the onset of temporary melt comparisons with snow buoy data suggest that also the onset of continuous snowmelt does not translate into changes in snow depth for a longer period but might rather affect the internal stratigraphy and density structure of the snowpack considering the entire data set the timing of snowmelt processes does not show significant temporal trends

variations of glacial lakes and glaciers in the boshula mountain range southeast tibet from the 1970s to 2009 catastrophic floods originating from glacial lake outbursts have recently become one of the primary natural hazards in the southeastern tibetan plateau here we report observations of glacial lake expansions and glacier recessions in the boshula mountain range southeast tibet derived from multitemporal remote sensing images and digital elevation models during the period from the 1970s to 2009 the area of glacial lakes has expanded from 9 24 0 1 km 2 in the 1970s to 10 96 0 1 km 2 in 2009 specifically the area of moraine dammed lakes has increased by 26 8 from the 1970s to 2009 the glacierized area in the boshula mountain range shrank by 12 7 21 2 km 2 increasing mean summer air temperature was the main cause for the glacier recession and lake expansion from the 1970s to 2001 while the combination of increased summer temperature and decreased summer precipitation led to accelerated glacier recession after 2001 climate warming and ongoing deglaciation play important roles in the expansion of moraine dammed lakes calling for intensified monitoring to properly address the hazard potential in the study area

arise antarctic remote ice sensing experiment in the east 2003 validation of satellite derived sea ice data products preliminary results are presented from the first validation of geophysical data products ice concentration snow thickness on sea ice hs and ice temperature ti from the nasa eos aqua amsr e sensor in east antarctica in september october 2003 the challenge of collecting sufficient measurements with which to validate the coarse resolution amsr e data products adequately was addressed by means of a hierarchical approach using detailed in situ measurements digital aerial photography and other satellite data initial results from a circumnavigation of the experimental site indicate that at least under cold conditions with a dry snow cover there is a reasonably close agree ment between satellite and aerial photo derived ice concentrations i e 97 2 3 6 for nt2 and 96 5 2 5 for bba algorithms vs 94 3 for the aerial photos in general the amsr e concentration represents a slight overestimate of the actual concentration with the largest discrepancies occurring in regions containing a relatively high proportion of thin ice the amsr e concentrations from the nt2 and bba algorithms are similar on average although differences of up to 5 occur in places again related to thin ice distribution the amsr e ice temperature ti product agrees with coincident surface measurements to approximately 0 58c in the limited dataset analyzed regarding snow thickness the amsr hs retrieval is a significant underestimate compared to in situ measurements weighted by the percentage of thin ice and open water present for the case study analyzed the underestimate was 46 for the overall average but 23 compared to smooth ice measurements the spatial distribution of the amsr e hs product follows an expected and consistent spatial pattern suggesting that the observed difference may be an offset at least under freezing conditions areas of discrepancy are identified and the need for future work using the more extensive dataset is highlighted

rapid expansion of glacial lakes caused by climate and glacier retreat in the central himalayas glacial lake outburst floods are among the most serious natural hazards in the himalayas such floods are of high scientific and political importance because they exert trans boundary impacts on bordering countries the preparation of an updated inventory of glacial lakes and the analysis of their evolution are an important first step in assessment of hazards from glacial lake outbursts here we report the spatiotemporal developments of the glacial lakes in the poiqu river basin a trans boundary basin in the central himalayas from 1976 to 2010 based on multi temporal landsat images studied glacial lakes are classified as glacier fed lakes and non glacier fed lakes according to their hydrologic connection to glacial watersheds a total of 119 glacial lakes larger than 0 01km 2 with an overall surface area of 20 22km 2 10 8 were mapped in 2010 with glacier fed lakes being predominant in both number 69 58 0 and area 16 22km 2 80 2 we found that lakes connected to glacial watersheds glacier fed lakes significantly expanded 122 1 from 1976 to 2010 whereas lakes not connected to glacial watersheds non glacier fed lakes remained stable 2 8 during the same period this contrast can be attributed to the impact of glaciers retreating glaciers not only supply meltwater to lakes but also leave space for them to expand compared with other regions of the hindu kush himalayas hkh the lake area per glacier area in the poiqu river basin was the highest this observation might be attributed to the different climate regimes and glacier status along the hkh the results presented in this study confirm the significant role of glacier retreat on the evolution of glacial lakes copyright c 2014 john wiley sons ltd

regional scale sea ice and snow thickness distributions from in situ and satellite measurements over east antarctica during sipex 2007 the sea ice physics and ecosystem experiment sipex was conducted in the east antarctic pack ice zone between 115 130 degrees e from 9 september 11 october 2007 in situ measurements of sea ice and snow properties were conducted at 15 ice stations together with ship based aspect observations the ice and snow thickness varied considerably in different regions of the pack ice with particularly thick ice associated with deformation and a strong slope jet in the southwest of the study region the mean ice thickness was 0 99 m 1 57 m excluding the northern marginal ice zones but varied from 0 61 m along the southern leg to 1 80 m along the western leg with pockets of considerably thicker ice in some regions swell was observed on two occasions penetrating more than 330 km south of the ice edge into regions with 80 100 ice concentration ice thicknesses calculated from near coincident icesat laser altimetry 1 74 m are similar to the in situ observations in the central pack 1 57 m c 2010 elsevier ltd all rights reserved

examining the interaction between multi year landfast sea ice and the mertz glacier tongue east antarctica another factor in ice sheet stability the mertz glacier tongue mgt east antarctica has a large area of multi year fast sea ice myfi attached to its eastern edge we use various satellite data sets to study the extent age and thickness of the myfi and how it interacts with the mgt we estimate its age to be at least 25 years and its thickness to be 10 55 m this is an order of magnitude thicker than the average regional sea ice thickness and too thick to be formed through sea ice growth alone we speculate that the most plausible process for its growth after initial formation is marine frazil ice accretion the satellite data provide two types of evidence for strong mechanical coupling between the two types of ice the myfi moves with the mgt and persistent rifts that originate in the mgt continue to propagate for large distances into the myfi the area of myfi decreased by 50 following the departure of two large tabular icebergs that acted as pinning points and protective barriers future myfi extent will be affected by subsequent icebergs from the ninnis glacier and the imminent calving of the mgt fast ice is vulnerable to changing atmospheric and oceanic conditions and its disappearance may have an influence on ice tongue ice shelf stability understanding the influence of thick myfi on floating ice tongues ice shelves may be significant to understanding the processes that control their evolution and how these respond to climate change and thus to predicting the future of the antarctic ice sheet

passive microwave observations of the weddell sea during austral winter and early spring the results of multispectral passive microwave observations 6 7 to 90 ghz are presented from the cruises of the fs polarstern in the weddell sea from july to december 1986 this paper includes primarily the analysis of radiometric observations taken at ice station sites averaged emissivity spectra for first year fy ice were relatively constant throughout the experiment and were not statistically different from fy ice signatures in the arctic detailed ice characterization was carried out at each site to compare the microwave signatures of the ice with the physical properties absorption optical depths of fy ice were found to be sufficiently high that only the structure in the upper portions of the ice contributed significantly to interstation emissivity variations the emissivities at 90 ghz e 90 had the greatest variance both e 90 at vertical polarization and gr sub e 90 18 7 defined as e sub v 90 e sub v 18 7 e sub v 90 e sub v 18 7 depended on the scattering optical depth which is a function of the snow grain diameter and layer thickness the variance showed a latitude dependence and is probably due to an increase in the strength of snow metamorphism nearer the northern edge of the ice pack the contribution of variations of near surface brine volume to the emissivity was not significant over the range of values encountered at the station sites emissivity spectra are presented for a range of thin ice types unsupervised principal component analysis produced three significant eigenvectors and showed a separation among four different surface types open water thin ice fy ice and fy ice with a thick snow cover a comparison with smmr satellite data showed that average ice concentrations derived from the ship s ice watch log were consistent with the satellite concentrations the surface based emissivities for fy ice were also compared with emissivities calculated from scanning multichannel microwave radiometer smmr satellite radiances best agreement was found at 6 7 and 10 ghz while at 18 and 37 ghz smmr emissivities were slightly lower than surface based results for the three lower frequencies agreement was found within a confidence limit of 95 and for 37 ghz within about 90

the stability of rms lg measurements and their potential for accurate estimation of the yields of soviet underground nuclear explosions data on underground nuclear explosions have recently become available from modern digital seismic stations installed within the soviet union and china observations of root mean square rms lg wave signals for soviet underground nuclear explosions at the shagan river test site in east kazakhstan show that the relative amplitudes of the rms signals at stations in norway the ussr and china are very similar for different explosions the standard deviation of the differences being only about 0 03 in logarithmic units i e magnitude units this is consistent with earlier observations comparing norsar and graefenberg array data and the observed scatter is significantly lower than has been reported for lg data from nevada test site explosions in view of the excellent correspondence found by nuttli 1986 and patton 1988 for lg versus yield at nevada this indicates that rms lg has a potential for yield estimation with very high accuracy at shagan river our study has shown that a selected stations in the ussr and china situated at regional distances provide a much improved signal to noise ratio of the lg phase for events at shagan river as compared to norsar array data b the scaling of rms lg amplitudes between different sized events recorded at the same single station site appears to be consistent with that of norsar indicating a remarkable degree of precision in single station measurements of lg signal c rms lg amplitude measurements for the best of these stations may be made at 1 5 to 2 0 magnitude units lower than at norsar or graefenberg allowing a much lower threshold for lg based yield determination and d the p wave detection capabilities of these single stations do not match those of the noress and arcess arrays thus teleseismic signals continue to be important for detection of small nuclear explosions our conclusion is that lg signals appear to provide an excellent basis for supplying estimates of the yields of nuclear explosions even down to below 1 kt when such signals are recorded at high quality digital in country seismic stations and when calibrated by access to independent nonseismic yield information for a few nuclear explosions at the test sites of interest in the context of monitoring a low yield threshold test ban treaty it will in addition be important to take into consideration various environmental conditions in the testing area such as the possible presence of cavities and to devise appropriate procedures for on site observations in this regard

an intercomparison between amsr e snow depth and satellite c and ku band radar backscatter data for antarctic sea ice advanced microwave scanning radiometer amsr e snow depth data for antarctic sea ice are compared with ship based visual observations of snow depth ice type and ridged ice fraction and with satellite c band and ku band radar backscatter observations for two ship cruises into the weddell sea ispol 2004 05 wwos 2006 and one cruise into the bellingshausen sea simba 2007 during late winter spring most 75 amsr e and ship based snow depth observations agree within 0 2 m during wwos and simba remaining observations indicate substantial underestimations of snow depths by amsr e data these underestimations tend to increase with the ridged ice fraction for wwos and simba in areas with large snow depths a combination of relatively stable low c band radar backscatter and variable ku band radar backscatter is associated with undeformed first year ice and may indicate snow metamorphism at this time of year during simba in areas with small snow depths a combination of relatively stable low ku band radar backscatter high c band radar backscatter and low c band radar backscatter standard deviations is associated with rough first year ice during simba this information can help to better understand causes of the observed amsr e snow depth bias during late winter spring conditions with decreasing average snow depth and to delineate areas where this bias occurs

the glaciers climate change initiative methods for creating glacier area elevation change and velocity products glaciers and their changes through time are increasingly obtained from a wide range of satellite sensors due to the often remote location of glaciers in inaccessible and high mountain terrain satellite observations frequently provide the only available measurements furthermore satellite data provide observations of glacier characteristics that are difficult to monitor using ground based measurements thus complementing the latter in the glaciers cci project of the european space agency esa three of these characteristics are investigated in detail glacier area elevation change and surface velocity we use a data from optical sensors to derive glacier outlines b digital elevation models from at least two points in time c repeat altimetry for determining elevation changes and d data from repeat optical and microwave sensors for calculating surface velocity for the latter the two sensor types provide complementary information in terms of spatio temporal coverage while c and d can be generated mostly automatically a and b require the intervention of an analyst largely based on the results of various round robin experiments multi analyst benchmark studies for each of the products we suggest and describe the most suitable algorithms for product creation and provide recommendations concerning their practical implementation and the required post processing for some of the products area velocity post processing can influence product quality more than the main processing algorithm

a method to automatically determine sea level for referencing snow freeboards and computing sea ice thicknesses from nasa icebridge airborne lidar abstract the nasa icebridge flights have obtained critical observations for earth s polar ice since icesat stopped collecting data in 2009 this study develops an automatic method in processing icebridge airborne topographic mapper atm altimeter l1b data one elevation per 3 4 m horizontally to derive a local sea level height for referencing snow freeboards and then computing sea ice thicknesses four 30 km l1b profiles a b c and d flown on october 21 2009 over the bellingshausen sea in antarctica are selected the local sea level reference is first obtained by visual examination of atm l1b heights over leads or thin ice identified on images simultaneously acquired from the digital mapping system camera called manual selection this sea level reference is then used as ground truth to validate sea level heights derived by automatic calculations using five thresholds of 2 1 0 5 0 2 and 0 1 of the lowest l1b data the l1b 0 2 method gives a similar sea level height as from the l1b manual selection by mean absolute difference of 0 01 0 06 m the sea level heights demonstrate a near linear gradient of 0 01 m km to 0 03 m km within each 30 km l1b profile along the flight track from section a to d the resulting mean snow freeboards are 0 59 m 0 67 m 0 53 m and 0 60 m on sections a b c and d respectively three empirical equations and the buoyancy equation with zero ice freeboard assumption all give similar statistics in ice thickness estimation with mean ice thicknesses of 1 91 m for section a 2 16 m for b 1 76 m for c and 1 94 m for d the sea level over leads cannot be accurately resolved from the atm l2 data 60 m x 80 m horizontal averaging however by using a sea level reference obtained from the l1b data the atm l2 data can achieve reasonable ice thickness estimates with mean absolute difference of only 0 10 m compared to thickness derived from the l1b data

discrimination of chemical explosions and earthquakes in central europe a case study both natural and artificial seismicity is observed in the vogtland area at near regional distance 180 km from the geress array this setting offers the opportunity to test various discrimination criteria using a uniform data set of 39 earthquakes and 22 chemical explosions strip mine and quarry blasts from a single epicentral region mostly eliminating wave path and distance effects discriminants used include lg pg and lg rg maximum amplitude ratios spectral peaks and slopes extracted by autoregressive moving average arma modeling master event correlation and the search for time independent frequency structures in sonograms although no single discrimi nant achieves a perfect separation of the two populations a joint discrimination scheme employing simple majority voting reduces misclassifications to 2 future research will focus on possible generalization and the physical basis of the discriminants

assessing ice cliff backwasting and its contribution to total ablation of debris covered miage glacier mont blanc massif italy continuous surface debris cover strongly reduces the ablation of glaciers but high melt rates may occur at ice cliffs that are too steep to hold debris this study assesses the contribution of ice cliff backwasting to total ablation of miage glacier mont blanc massif italy in 2010 and 2011 based on field measurements physical melt models and mapping of ice cliffs using a high resolution 1 m digital elevation model dem short term model calculations closely match the measured melt rates a model sensitivity analysis indicates that the effects of cliff slope and albedo are more important for ablation than enhanced longwave incidence from sun warmed debris or reduced turbulent fluxes at sheltered cliff bases analysis of the dem indicates that ice cliffs account for at most 1 3 of the 1 m pixels in the glacier s debris covered zone but application of a distributed model indicates that ice cliffs account for 7 4 of total ablation we conclude that ice cliffs make an important contribution to the ablation of debris covered glaciers even when their spatial extent is very small

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

modelling the feedbacks between mass balance ice flow and debris transport to predict the response to climate change of debris covered glaciers in the himalaya many himalayan glaciers are characterised in their lower reaches by a rock debris layer this debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean ice surfaces debris covered glaciers can persist well below the altitude that would be sustainable for clean ice glaciers resulting in much longer timescales of mass loss and meltwater production the properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean ice surfaces and yield conflicting results we developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance to investigate the impact of debris transport on the response of a glacier to recent and future climate change we applied this model to a large debris covered himalayan glacier khumbu glacier in nepal our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ concealing the magnitude of mass loss when compared with estimates based on glacierised area since the little ice age khumbu glacier has lost 34 of its volume while its area has reduced by only 6 we predict a decrease in glacier volume of 8 10 by ad2100 accompanied by dynamic and physical detachment of the debris covered tongue from the active glacier within the next 150 yr this detachment will accelerate rates of glacier decay and similar changes are likely for other debris covered glaciers in the himalaya

consideration of the errors inherent in mapping historical glacier positions in austria from the ground and space 1893 2001 the historical record of in situ measurements of the terminus positions of the pasterze and kleines fleiskees glaciers in the eastern alps of austria is used to assess uncertainties in the measurement of decadal scale changes using satellite data topographic maps beginning in 1893 and satellite data from 1976 to 2001 were studied in concert with ground measurements to measure glacier changes ground measurements show that the tongue of the pasterze glacier receded f1150 m from 1893 to 2001 while satellite derived measurements using august 2001 landsat enhanced thematic mapper plus etm data registered to an 1893 topographic map show a recession of 1300 1800 m with an unknown error the measurement accuracy depends on the registration technique and the pixel resolution of the sensor when two satellite images are used when using topographic maps an additional source of error is the accuracy of the glacier position shown on the map between 1976 and 2001 landsat derived measurements show a recession of the terminus of the pasterze glacier of 479f136 m at an average rate of 19 1 m a 1 while measurements from the ground showed a recession of 428 m at an average rate of 17 1 ma 1 four meter resolution ikonos satellite images from 2000 and 2001 reveal a shrinkage of 22 096f46 m 2 in the pasterze tongue the nearby kleines fleiskees glacier lost 30 of its area between 1984 and 2001 and the area of exposed ice increased by 0 44f0 0023 km 2 according to landsat satellite measurements as more recent satellite images are utilized especially data that are geocoded the uncertainty associated with measuring glacier changes has decreased it is not possible to assess the uncertainty when an old topographic map and a satellite image are coregistered

the second chinese glacier inventory data methods and results the second chinese glacier inventory was compiled based on 218 landsat tm etm scenes acquired mainly during 2006 10 the widely used band ratio segmentation method was applied as the first step in delineating glacier outlines and then intensive manual improvements were performed the shuttle radar topography mission digital elevation model was used to derive altitudinal attributes of glaciers the boundaries of some glaciers measured by real time kinematic differential gps or digitized from high resolution images were used as references to validate the accuracy of the methods used to delineate glaciers which resulted in positioning errors of 10 m for manually improved clean ice outlines and 30 m for manually digitized outlines of debris covered parts the glacier area error of the compiled inventory evaluated using these two positioning accuracies was 3 2 the compiled parts of the new inventory have a total area of 43 087 km 2 in which 1723 glaciers were covered by debris with a total debris covered area of 1494 km 2 the area of uncompiled glaciers from the digitized first chinese glacier inventory is similar to 8753 km 2 mainly distributed in the southeastern tibetan plateau where no images of acceptable quality for glacier outline delineation can be found during 2006 10

on the extraordinary snow on the sea ice off east antarctica in late winter 2012 abstract in late winter early spring 2012 the second sea ice physics and ecosystems experiment sipex ii was conducted off wilkes land east antarctica onboard r v aurora australis the sea ice conditions were characterized by significantly thick first year ice and snow trapping the ship for about 10 days in the near coastal region the deep snow cover was particularly remarkable in that its average value of 0 45 m was almost three times that observed between 1992 and 2007 in the region to reveal factors responsible we used in situ observations and era interim reanalysis 1990 2012 to examine the relative contribution of the different components of the local regional snow mass balance equation i e snow accumulation on sea ice precipitation minus evaporation p e and loss by i snow ice formation and ii entering into leads due to drifting snow results show no evidence for significantly high p e in the winter of 2012 ice core analysis has shown that although the snow ice layer was relatively thin indicating less transformation from snow to snow ice in 2012 as compared to measurements from 2007 the difference was not enough to explain the extraordinarily deep snow based on these results we deduce that lower loss of snow into leads was probably responsible for the extraordinary snow in 2012 statistical analysis and satellite images suggest that the reduction in loss of snow into leads is attributed to rough ice surface associated with active deformation processes and larger floe size due to sea ice expansion this highlights the importance of snow sea ice interaction in determining the mean snow depth on antarctic sea ice

investigation of teleseismic lg blockage and scattering using regional arrays abstract incoherent beamforming and continuous frequency wavenumber polar scan analysis have been applied to study the characteristics of p coda and lg waves recorded at the regional arrays noress and arcess from presumed explosions on the northwestern russian platform and at test sites of novaya zemlya and eastern kazakh also recordings at the graefenburg array near the new geress regional array of novaya zemlya events and an eastern european platform white sea event have been compared with the norwegian array recordings of the same events the white sea explosion at distances of 14 and 22 from noress and graefenburg respectively exhibits lg rms amplitudes on incoherent beams that exceed those of sn however for explosions at novaya zemlya at 20 from noress and eastern kazakh at 30 from arcess the lg waves have much smaller amplitudes than sn in the case of novaya zemlya the lg wave is almost completely blocked at both noress and arcess but is well recorded at graefenburg this reduction of the lg amplitudes relative to those from events at longer distances cannot be accounted for by anelastic attenuation and spreading comparison of propagation paths suggests that the reduction in amplitudes may be due to blockage and scattering of lg in the barents sea analysis of sn coda waves on incoherent beams and continuous frequency wavenumber analysis polar scans suggests that they can result from lg to sn scattering from the coastline between the barents sea and scandinavia recent geologic studies have revealed significant variations in crustal structure in the barents sea basin which may cause the blockage of lg waves from novaya zemlya in the case of eastern kazakh explosions arcess incoherent beams show much reduced lg amplitudes relative to the p coda waves compared with noress even though the distance to arcess 31 is less than that to noress 38 this reduction in lg amplitude at both noress and arcess is accompanied by enhancement of p and sn coda the timing of the coda waves and the propagation paths suggest that lg waves may be partially blocked and scattered by the ural mountains and that the p and sn coda waves may result from lg to pn pn to sn sn to lg and lg to sn conversions from lateral heterogeneities in the crust beneath the urals the blockage is greater for the eastern kazakh to arcess path because it crosses the middle part of the urals whereas the eastern kazakh to noress path crosses the southern part of the urals chain these blockage effects seem to result from sudden lateral variations in shallow crustal structure such as variations in sediment thicknesses in the sedimentary basins of the russian platform and adjacent to the urals these blockage effects can be predicted from geologic studies and need to be accounted for when using lg amplitudes to estimate absolute yields of explosions and for event identification

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

phase and spectral ratio discrimination between nts earthquakes and explosions part i empirical observations seismic discrimination of small magnitude mb 0 5 hz regional measurements in this study we evaluate the most promising short period discriminants p wave to s wave phase amplitude ratios and low to high frequency spectral amplitude ratios for a data set from the nevada test site the data consist of 130 underground nuclear explosions one very large chemical explosion and 50 earthquakes ranging from magnitude 2 to 6 recorded at two broadband digital seismic stations operated by lawrence livermore national laboratory in contrast with much previous discrimination work in the western united states the common stations and paths for all the events in this study allow the discriminants to be evaluated without applying propagation corrections and differences between events can be ascribed to very near source effects the source effects found to have the most influence on the discriminants in this study are depth for the earthquakes and the source medium properties of gas porosity density and velocity for the explosions the phase amplitude ratio discriminants tested are pn lg and pg lg both show little dependence on magnitude and work better at higher frequencies and when averaged over the two stations at 6 to 8 hz pn lg discriminates all except the shallowest earthquakes while pg lg discriminates all but the high gas porosity explosions low to high frequency spectral amplitude ratio discriminants were tested in each of the phases pn pg lg and lg coda the explosions show significant dependence on source material properties such as gas porosity all the spectral ratios show dependence on magnitude and for 1 2 hz 6 8 hz none performs well below magnitude 3 5 of the spectral ratios lg coda performs the best at least in part because of its extremely small interstation variability discriminating all but the low gasporosity explosions the best discriminant performance is given by combining phase and spectral ratios a sum of the logarithmic values of pn lg pg lg and the lg coda discriminates all but two of the shallowest earthquakes the source medium dependence of the discriminants suggests that discrimination performance differences between the western united states and other regions of the world may be due more to source property differences than differences in the regional path simply put western united states discriminant studies differ from those in the rest of the world because of the lack of explosions in very high gas porosity low velocity materials outside of the nevada test site

seismic event identification of earthquakes and explosions in germany using spectral lg ratios at the german ndc initial work on seismic event identification has focused on the application of spectral amplitude ratios for lg in order to discriminate naturally occurring seismic events from other events associated with mining and quarry activities only about 10 of all seismic events occurring in germany and adjacent areas are due to natural seismicity and are mostly constrained to the alpine regions and areas along the rhinegraben rhenish massif swabian jura and the bohemian massif vogtland region using data from the broadband grsn network spectral amplitude ratios are calculated from maximum trace amplitudes in the 1 2 hz and 6 8 hz frequency bands which are within the passbands of the deployed sts 2 instruments and the recorded 20 hz data streams these amplitude ratios then must be corrected with an appropriate attenuation model in order to remove propagation paths effects for event identification a scoring scheme is applied across the grsn network based on station dependent scoring thresholds in a case study aimed at testing the identification scheme events are investigated from a quarry in southern germany that provided ground truth information for six events in 1997 to demonstrate the suitability of this identification approach except for one event with a rather strong earthquake signature i e a low spectral lg ratio these events could be screened out from the earthquake population by their large lg ratios in a second step aimed at applying the identification scheme all events in germany and neighboring areas that occurred in 1995 were processed with approximately 800 out of more than 1200 events showing explosion type lg ratios while only 10 remain in the earthquake population however specific mining areas appear to consistently produce earthquake type spectral ratios indicative of particular blasting practices

a preliminary study of regional seismic discrimination in central asia with emphasis on western china abstract in support of a comprehensive test ban treaty we have started to evaluate regional seismic event discrimination capabilities for central asia emphasizing western china we have measured noise and signal levels of over 260 earthquakes and 26 underground nuclear explosions recorded at the broadband digital station wmq in western china and over 120 earthquakes and five nuclear explosions at station aak in kyrgyzstan the explosions are from the kazakh test site kts and lop nor china the earthquakes are mostly from northwest china event magnitudes measured as either m b or m l range between 2 5 and 6 5 and maximum event station distance is about 1700 km we formed phase spectral cross spectral short period long period and long period ratios to test many possible event discriminants all ratios were corrected for distance effects before forming ratio versus magnitude discrimination plots the most consistent discriminants for separating earthquakes from explosions are p s phase ratios for frequencies above 3 to 4 hz p wave f 1 hz to rayleigh wave 0 03 hz f p s ratios separation between earthquakes and explosions increases with frequency and for the p r ratios separation increases with increasing p frequency the p 3 to 6 hz s 0 75 to 1 5 hz cross spectral ratios also separate earthquakes and explosions these cross spectral ratios may prove quite useful because due to weak high frequency l g signals from explosions the high frequency p l g ratio sometimes cannot be evaluated but the p 3 to 6 hz l g 0 75 to 1 5 hz can be evaluated successfully p spectral ratios 3 to 6 hz 0 75 to 1 5 hz also separate earthquakes and explosions but not quite as consistently as the p s ratios however p spectral ratios may prove useful in cases where path effects block or highly attenuate s n and l g waves rendering the p s ratios unavailable in contrast to nevada test site nts events the l g 3 to 6 hz 0 75 to 1 5 hz spectral ratio does not separate earthquakes and nuclear explosions in central asia this observation may be a source effect as asian explosions are thought to be detonated in highly lithified rocks below the water table while most of the smaller m b for station aak the short period spectral and cross spectral ratios identify a few earthquakes not recorded at wmq from the north pamir region that plot with the lop nor explosions the waveforms from these earthquakes lack surface waves and a distinct l g phase these events which we interpret as having occurred in a subducted slab do separate from the explosions on high frequency f 4 hz p s discrimination plots for station wmq long period r l rayleigh wave love wave ratios separate kts explosions and asian earthquakes however r l ratios fail to identify the large lop nor explosions recorded at station aak because the love waves are as large as the rayleigh waves suggesting that strong tectonic release occurs with these explosions because we have examined only one path at a single station for these explosions source radiation pattern may be influencing this observation

sea ice thickness retrieval algorithms based on in situ surface elevation and thickness values for application to altimetry 1 in situ measurements of sea ice thickness i snow depth s and snow freeboard fsn from drilling profile lines from 15 cruises into the southern ocean antarctica were analyzed i was calculated from in situ fsn and s using an isostatic approach i was also directly estimated from fsn as can be obtained from laser altimetry the root mean square difference rmsd between observed and calculated i reduces and the correlation between fsn and i increases substantially when 1 using values averaged over the survey lines 50 m instead of single drill hole measurements 1 m and 2 treating positive and negative sea ice freeboard fi separately for small fi however s approximates fsn pointing toward an isostatic balance also between s and i our linear regression analysis between the in situ measurements suggests a direct conversion of fsn into i using a region specific set of equations rmsd values are similar to those obtained employing isostatic balance models and treating positive and negative fi separately however more data would have been needed to obtain significant differences between most of the various models suggested still our new approach gives a viable alternative for antarctic i retrieval from altimetric measurements of fsn alone correlation between in situ observations of fsn and s is high rmsd between observed and calculated s is small this suggests estimation of s from altimetric fsn measurements such s has an estimated precision of 5 cm and is neither affected by snow wetness or grain size nor limited to s 50 cm

study of low magnitude seismic events near the novaya zemlya nuclear test site abstract a study of available seismic data shows that all but one of the 42 known underground nuclear explosions at novaya zemlya have been detected and located by stations in the global seismic network during the past 30 years only one seismic event in this area has been unambiguously classified as an earthquake 1 august 1986 m b 4 3 several other small events most of which are thought to be either chemical explosions or aftereffects of nuclear explosions have also been detected since 1990 a network of sensitive regional arrays has been installed in northern europe in preparation for the global seismic monitoring network under a comprehensive nuclear test ban treaty ctbt this regional network has provided a detection capability for novaya zemlya that is shown to be close to m b 2 5 three low magnitude events have been detected and located during this period as discussed in this article 31 december 1992 m b 2 7 13 june 1995 m b 3 5 and 13 january 1996 m b 2 4 to classify the source types of these events has proved very difficult thus even for the m b 3 5 event in 1995 we have been unable to provide a confident classification of the source as either an earthquake or explosion using the available discriminants a study of m b magnitude in different frequency bands shows as expected that the calculation of m b at regional distances needs to take into account source scaling effects at high frequencies thus when comparing a 4 to 8 or 8 to 16 hz filter band to a teleseismic 2 to 4 hz band the smaller events have relatively speaking significantly more high frequency energy up to 0 5 m b units than the larger events this suggests that a p wave spectral magnitude scale might be appropriate the problem of accurately locating small events using a sparse array network is addressed using the 13 january 1996 event which was detected by only two arrays as an illustrative example our analysis demonstrates the importance of using accurately calibrated regional travel time curves and at the same time illustrates how array processing can be used to identify an interfering phase from a local disturbance thereby avoiding location errors due to erroneous phase readings

icesat observations of arctic sea ice a first look 1 analysis of near coincident icesat and radarsat imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings containing thin ice or open water in the sea ice cover as well as to surface relief of old and first year ice the precision of the elevation estimates measured over relatively flat sea ice is 2 cm using the thickness of thin ice in recent openings to estimate sea level references we obtain the sea ice freeboard along the altimeter tracks this step is necessitated by the large uncertainties in the sea surface topography compared to that required for accurate determination of freeboard unknown snow depth introduces the largest uncertainty in the conversion of freeboard to ice thickness surface roughness is also derived for the first time from the variability of successive elevation estimates along the altimeter track overall these icesat measurements provide an unprecedented view of the arctic ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint of 70 m

glacier mass changes in rongbuk catchment on mt qomolangma from 1974 to 2006 based on topographic maps and alos prism data abstract elevation changes of glacier surfaces were investigated in rongbuk catchment rc on the northern slopes of mt qomolangma in the central himalayas by comparing a digital elevation model dem generated from the 2006 alos prism imageries with the base dem1974 derived from the 1 50 000 topographic maps the average elevation change rate of glacier surfaces in rc was estimated at 0 47 0 23 m a 1 between 1974 and 2006 such surface lowering rates varied significantly with glaciers and altitudes one of the notable results is that the debris covered ice thinned much more rapidly than the exposed ice at higher altitudes overall glaciers in rc have lost mass of 0 06 0 04 gt a 1 during 1974 2006 glacier imbalance constitutes about 50 or more of the rongbuk runoff