remote sensing estimates of glacier mass balances in the himachal pradesh western himalaya india abstract although they correspond to an important fraction of the total area of mountain glaciers 33 000 km2 out of 546 000 km2 himalayan glaciers and their mass balance are poorly sampled for example between 1977 and 1999 the average area surveyed each year on the field was 6 8 km2 only no direct mass balance measurement is available after 1999 to contribute to fill this gap we use remote sensing data to monitor glacier elevation changes and mass balances in the spiti lahaul region 32 2 n 77 6 e himachal pradesh western himalaya india our measurements are obtained by comparing a 2004 digital elevation model dem to the 2000 srtm shuttle radar topographic mission topography the 2004 dem is derived from two spot5 satellite optical images without any ground control points this is achieved thanks to the good on board geolocation of spot5 scenes and using srtm elevations as a reference on the ice free zones before comparison on glaciers the two dems are analyzed on the stable areas surrounding the glaciers where no elevation change is expected two different biases are detected a long wavelength bias affects the spot5 dem and is correlated to an anomaly in the roll of the spot5 satellite a bias is also observed as a function of altitude and is attributed to the srtm dataset both biases are modeled and removed to permit unbiased comparison of the two dem on the 915 km2 ice covered area digitized from an aster image on most glaciers a clear thinning is measured at low elevations even on debris covered tongues between 1999 and 2004 we obtain an overall specific mass balance of 0 7 to 0 85 m a water equivalent depending on the density we use for the lost or gained material in the accumulation zone this rate of ice loss is twice higher than the long term 1977 to 1999 mass balance record for himalaya indicating an increase in the pace of glacier wastage to assess whether these ice losses are size dependant all glaciers were classified into three samples according to their areal extent all three samples show ice loss the loss being higher for glaciers larger than 30 km2 in the case of the benchmark chhota shigri glacier a good agreement is found between our satellite observations and the mass balances measured on the field during hydrological years 2002 2003 and 2003 2004 future studies using a similar methodology could determine whether similar ice losses have occurred in other parts of the himalaya and may allow evaluation of the contribution of this mountain range to ongoing sea level rise

landslide hazard assessment in the three gorges area china using aster imagery wushan badong abstract the objectives of this study are to develop a methodology for regional scale assessment of landslide hazard using remotely sensed data and to produce a landslide hazard map of the wushan badong area in the three gorges china from advanced spaceborne thermal emission and reflection radiometer aster images the area is undergoing rapid urban development with slope instability causing a widespread natural hazard landslide related parameters were largely estimated through image processing and visual interpretation of aster multi spectral and topographic data we used field measurements to define the quantification for three parameters a slope angle in relation to lithology b distance to drainage network in relation to stream order and c distance to tectonic lineament in relation to lineament length we employed a multi parameter elimination and characterization model based on estimation of the geometric mean to remove areas where landslides are not expected to occur and classify the remaining areas into landslide hazard categories our results show increased landslide hazard in and around wushan and badong towns as well as other populated areas along the yangtze and its tributaries we used field data on landslide distribution to identify typical geomorphological settings for different landslide types and to provide ground control for the hazard assessment the results indicate good correlation between classified high hazard areas and field confirmed slope failures and show the usefulness of aster imagery for landslide hazard assessment at a regional scale

river stage influences on uranium transport in a hydrologically dynamic groundwater surface water transition zone a well field within a uranium u plume in the groundwater surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes the plume discharges to the columbia river which displays a dramatic spring stage surge resulting from snowmelt groundwater exhibits a low hydrologic gradient and chemical differences with river water river water intrudes the site in spring specific aims were to assess the impacts of river intrusion on dissolved uranium uaq specific conductance spc and other solutes and to discriminate between transport geochemical and source term heterogeneity effects as a result of water table elevation fluctuations river water intrusion and changes in groundwater flow directions time series trends for uaq and spc were found to be complex and displayed large temporal and well to well variability the wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms hot spots in uaq varied in location with increasing water table elevation through the combined effects of advection and source term location heuristic reactive transport modeling with pflotran demonstrated that mobilized uaq was transported between wells and source terms in complex trajectories and was diluted as river watermore entered and exited the groundwater system moreover while uaq time series concentration trends varied significantly from year to year as a result of climate caused differences in the spring hydrograph common and partly predictable response patterns were observed that were driven by water table elevation and the extent and duration of river water intrusion less

river stage tomography a new approach for characterizing groundwater basins received 19 june 2008 revised 16 february 2009 accepted 12 march 2009 published 9 may 2009 1 data from tomographic surveys make an inverse problem better posed in comparison to the data from a single excitation source a tomographic survey provides different coverages and perspectives of subsurface heterogeneity nonfully redundant information of the subsurface fusion of these pieces of information expands and enhances the capability of a conventional survey provides cross validation of inverse solutions and constrains inherently ill posed field scale inverse problems basin scale tomography requires energy sources of great strengths spatially and temporally varying natural stimuli are ideal energy sources for this purpose in this study we explore the possibility of using river stage variations for basin scale subsurface tomographic surveys specifically we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of the river stage in a hypothetical groundwater basin we then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image subsurface heterogeneity of the basin results of the numerical exercises are encouraging and provide insights into the proposed river stage tomography using naturally recurrent stimuli such as river stage variations for characterizing groundwater basins could be the future of geohydrology however it calls for implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface

automated coregistration of repeat digital elevation models for surface elevation change measurement using geometric constraints a large archive of digital elevation model dem data spanning more than a decade is now available for a wide range of earth surface process studies precise coregistration is a critical step for obtaining accurate elevation change measurements from repeat dems we present an algorithm for coregistering stereoscopic gridded dems that includes an automatic detection of control surfaces a reliable estimation technique for defining a geometric relationship between dems through a 3 d conformal transformation and a quality check qc for the confidence of the coregistration for the control surface detection we use a geometric constraint approach that uses similarities in slope aspect and height undulation as observation weights in an iterative transformation model solution the qc is possible through the evaluation of the geometric similarities and the amount of detected relatively unchanged surfaces we test our algorithm using a sample of repeat stereoscopic gridded dems from multiple sources over a rapidly changing glacier in greenland the algorithm results on average in a 24 decrease in the standard error as obtained from elevation over stationary surfaces the result is not sensitive to the distribution of the control surface the qc metric provides a simple and effective criterion for parsing result quality in large data sets surface height decreases of 110 and 200 m at the up glacier and down glacier ends of kangerdlugssuaq glacier in greenland are observed between april 2001 and june 2010 respectively

rigorous 3d change determination in antarctic peninsula glaciers from stereo worldview 2 and archival aerial imagery abstract this paper presents detailed elevation and volume analysis of 16 individual glaciers grouped at four locations spread across the antarctic peninsula ap the study makes use of newly available worldview 2 satellite stereo imagery to exploit the previously untapped value of archival stereo aerial photography high resolution photogrammetric digital elevation models dems are derived to determine three dimensional glacier change over an unprecedented time span of six decades with an unparalleled mean areal coverage of 82 per glacier the use of an in house robust surface matching algorithm ensured rigorous alignment of the dems to overcome inherent problems associated with processing archival photography most notably the identification and correction of scale error in some datasets the analysis provides insight into one of the most challenging and data scarce areas on the planet by expanding the spatial extent north of the ap to include previously un studied glaciers located in the south shetland islands 81 of glaciers studied showed considerable loss of volume over the period of record the mean annual mass loss for all glaciers yielded 0 24 0 08 m w e per year with a maximum mass loss of up to 62 m w e and frontal retreat exceeding 2 2 km for stadium glacier located furthest north on elephant island observed volumetric loss was broadly though not always correlated with frontal retreat the combined mass balance of all 16 glaciers yielded 1 862 0 006 gt which corresponds to 0 005 mm sea level equivalent sle over the 57 year observation period

formation and interpretation of dilatant echelon cracks the relative displacements of the walls of many veins joints and dikes demonstrate that these structures are dilatant cracks we infer that dilatant cracks propagate in a principal stress plane normal to the maximum tensile or least compressive stress arrays of echelon crack segments appear to emerge from the peripheries of some dilatant cracks breakdown of a parent crack into an echelon array may be initiated by a spatial or temporal rotation of the remote principal stresses about an axis parallel to the crack propagation direction near the parent crack tip a rotation of the local principal stresses is induced in the same sense but not necessarily through the same angle incipient echelon cracks form at the parent crack tip normal to the local maximum tensile stress further longitudinal growth along surfaces that twist about axes parallel to the propagation direction realigns each echelon crack into a remote principal stress plane the walls of these twisted cracks may be idealized as helicoidal surfaces an array of helicoidal cracks sweeps out less surface area than one parent crack twisting through the same angle thus many echelon cracks grow from a single parent because the work done in creating the array as measured by its surface area decreases as the number of cracks increases in cross sections perpendicular to the propagation direction echelon cracks grow laterally each crack overlapping its neighbors until the mechanical interaction of adjacent cracks limits this growth dilation of each crack pinches the tips of adjacent cracks into an asymmetrical form and introduces local stresses that can cause lateral growth along a curving sigmoidal path sigmoidal echelon cracks may link at tip to plane intersections leaving a step in the through going crack wall the geometry of dilatant echelon cracks may be used to infer spatial or temporal changes in the orientation of principal stresses in the earth

combination of srtm3 and repeat aster data for deriving alpine glacier flow velocities in the bhutan himalaya abstract the present study evaluates the fusion of dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm the study area consists of high elevation glaciers draining through the rough topography of the bhutan himalayas it turns out that the aster derived and srtm3 dems have similar accuracy over the study area but the srtm3 dem contains less gross errors however for rough topography large sections of the srtm3 dem contain no data we therefore compile a combined srtm3 aster dem from this final composite master dem we produce repeat aster orthoimages from which we evaluate the dem quality and derive glacier surface velocities through image matching the glacier tongues north of the himalayan main ridge which enter the tibet plateau show maximum surface velocities in the order of 100 200 m year 1 in contrast the ice within the glacier tongues south of the main ridge flows with a few tens of meters per year these findings have a number of implications among others for glacier dynamics glacier response to climate change glacier lake development or glacial erosion the study indicates that space based remote sensing can provide new insights into the magnitude of selected surface processes and feedback mechanisms that govern mountain geodynamics

improving maps of ice sheet surface elevation change using combined laser altimeter and stereoscopic elevation model data we combine the complementary characteristics of laser altimeter data and stereoscopic digital elevation models dems to construct high resolution 100m maps of surface elevations and elevation changes over rapidly changing outlet glaciers in greenland measurements from spaceborne and airborne laser altimeters have relatively low errors but are spatially limited to the ground tracks while dems have larger errors but provide spatially continuous surfaces the principle of our method is to fit the dem surface to the altimeter point clouds in time and space to minimize the dem errors and use that surface to extrapolate elevations away from altimeter flight lines this reduces the dem registration errors and fills the gap between the altimeter paths we use data from icesat and atm as well as spot 5 dems from 2007 and 2008 and apply them to the outlet glaciers jakobshavn isbrae ji and kangerdlugssuaq kl we find that the main trunks of ji and kl lowered at rates of 30 35 and 7 20ma respectively the rates decreased inland the corresponding errors were 0 3 5 2ma 1 for ji and 0 3 5 1ma 1 for kl with errors increasing proportionally with distance from the altimeter paths

rapid ice discharge from southeast greenland glaciers interferometric synthetic aperture radar insar observations of southeast greenland glaciers acquired by the earth remote sensing satellites ers 1 2 in 1996 were combined with ice sounding radar data collected in the late 1990s to estimate a total discharge of 46 3 km 3 ice per year between 62 n and 66 n which is significantly lower than a mass input of 29 3 km 3 ice per year calculated from a recent compilation of snow accumulation data further north helheim glacier discharges 23 1 km 3 yr vs 30 3 km 3 yr accumulation kangerdlugssuaq glacier discharges 29 2 km 3 yr vs 23 km 3 yr and daugaard jensen glacier discharges 10 5 0 6 km 3 yr vs 10 5 1 km 3 yr the mass balance of east greenland glaciers is therefore dominated by the negative mass balance of southeast greenland glaciers 17 4 km 3 yr equivalent to a sea level rise of 0 04 0 01 mm yr warmer and drier conditions cannot explain the imbalance which we attribute to longterm changes in ice dynamics copyright 2004 by the american geophysical union

morphometric analysis of aeolian bedforms in the namib sand sea using aster data the aster global digital elevation model gdem has made elevation data at 30 m spatial resolution freely available enabling reinvestigation of morphometric relationships derived from limited field data using much larger sample sizes these data are used to analyse a range of morphometric relationships derived for dunes between dune height spacing and equivalent sand thickness in the namib sand sea which was chosen because there are a number of extant studies that could be used for comparison with the results the relative accuracy of gdem for capturing dune height and shape was tested against multiple individual aster dem scenes and against field surveys highlighting the smoothing of the dune crest and resultant underestimation of dune height and the omission of the smallest dunes because of the 30 m sampling of aster dem products it is demonstrated that morphometric relationships derived from gdem data are broadly comparable with relationships derived by previous methods across a range of different dune types the data confirm patterns of dune height spacing and equivalent sand thickness mapped previously in the namib sand sea but add new detail to these patterns

estimating the mass change of mountain glacier using a novel method based on insar observations melting glaciers have a direct contribution to sea level rise runoff and glacier lake outburst flood disasters therefore accurate estimations of glacier mass balances with high spatial large region and temporal annual seasonal resolutions are very important however the estimation of glacial mass balances in mountainous regions is usually hampered by remoteness and the lack of high precision topographic data for most mountain ranges this study presents a novel method for estimating mass changes in mountain glaciers using insar data we utilised observations of glacier surface deformation to derive changes in thickness and then calculated the mass change this method can accurately estimate short term mass changes we apply this method to the koxkar glacier in the tien shan mountain range in china and successfully estimate the seasonal mass change using theoretical error and statistical error analysis we determined that the accuracy of this method is much better than other geodetic methods we analyse the spatial characteristics of the mass changes in the ablation zone for the first time the results show considerable spatial and seasonal variability which were mainly from ablation in the summer with the greatest amount of glacial ablation reaching up to 3872 mm water equivalent w e and from accumulation in the winter

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

on the use of apparent hydraulic diffusivity as an indicator of connectivity summary connectivity of high permeability paths is recognized as important but has not been properly quantified in the groundwater literature in fact it has been shown that the concept is process dependent and difficult to define so that it applies both to water flow and solute transport phenomena field and numerical evidence from hydraulic tests suggest that the apparent hydraulic diffusivity d a could potentially inform about the phenomena in order to test this conjecture we present a monte carlo analysis based on series of fields that display varying degrees of connectivity our results confirm that d a does indeed indicate the presence of connectivity d a is found to correlate well with early tracer arrival time and also with the product of a flow connectivity indicator cf and a transport connectivity indicator ct this indicates that d a accounts both for connectivity effects controlling the average plume movement through cf and for connectivity effects not linked to the effective medium properties that control the progression of the solute front through ct analysis of seven binary fields suggests that flow connectivity hinges more on the continuity of fast paths whereas transport connectivity seems to be more dependent on the width of connected features forming possibly discontinuous fast paths in conjunction with previous studies our results suggest that hydraulic response arrival times and early arrival times of tracer can be expected to correlate well in most types of hydrogeologic systems

stream water infiltration bank storage and storage zone changes due to stream stage fluctuations abstract during a flood period stream stage increases induce infiltration of stream water into an aquifer subsequent declines in stream stage cause a reverse motion of the infiltrated water this paper presents the results of the water exchange rate between a stream and aquifer the storage volume of the infiltrated stream water in the surrounding aquifer bank storage and the storage zone the storage zone is the part of aquifer where groundwater is replaced by stream water during the flood modflow was used to simulate stream aquifer interactions and to quantify rates of stream infiltration and return flow modpath was used to trace the pathlines of the infiltrated stream water and to determine the size of the storage zone simulations were focused on the analyses of the effects of the stream stage fluctuation aquifer properties the hydraulic conductivity of streambed sediments regional hydraulic gradients and recharge and evapotranspiration et rates on stream aquifer interactions generally for a given stream aquifer system larger flow rates result from larger stream stage fluctuations larger storage volumes and storage zones are produced by larger and longer lasting fluctuations for a given stream stage hydrograph a lower permeable streambed an aquitard or an anisotropic aquifer of low vertical hydraulic conductivity can significantly reduce the rate of infiltration and limit the size of the storage zone the bank storage solely caused by the stage fluctuation differs slightly between gaining and losing streams short term rainfall recharge and et loss in the shallow groundwater slightly influence on the flow rate but their effects on bank storage in a larger area for a longer period can be considerable

satellite gravity measurements confirm accelerated melting of greenland ice sheet using time variable gravity measurements from the gravity recovery and climate experiment grace satellite mission we estimate ice mass changes over greenland during the period april 2002 to november 2005 after correcting for the effects of spatial filtering and limited resolution of grace data the estimated total ice melting rate over greenland is 239 23 cubic kilometers per year mostly from east greenland this estimate agrees remarkably well with a recent assessment of 224 41 cubic kilometers per year based on satellite radar interferometry data grace estimates in southeast greenland suggest accelerated melting since the summer of 2004 consistent with the latest remote sensing measurements

reconstructing morphometric change in a proglacial landscape using historical aerial photography and automated dem generation this paper explores the feasibility of using historical aerial photographs and digital photogrammetric procedures to reconstruct morphometric landscape changes in a proglacial setting of the southern coast mountains british columbia canada the photographic record includes 12 sets of vertical photography obtained at a range of large to medium nominal scales for the period 1947 to 1997 an automated procedure of digital elevation model dem extraction was employed and details of morphometric change were assessed by differencing the dem surfaces obtained for different dates of photography results are used to describe terrain surface changes associated with glacier recession moraine gully erosion and forest growth in the glacial forefield methods are reviewed for the estimation and handling of systematic and random vertical errors in the dems that are suitable for this type of environment where there are no historical surveys or monuments to use as a common benchmark and only natural features are available for establishing ground control digital photogrammetry applied to scanned archived photography can be used to generate high resolution sub meter dem surfaces of proglacial terrain suitable for quantifying decadal scale morphometric changes that have occurred since the mid 20th century to recent times potential applications of these techniques and the associated historical data are discussed

progressive increase in ice loss from greenland 1 laser altimeter measurements over greenland show increasing thickening rates above 2000 m reflecting increasing snowfall in a warming climate but near coastal thinning rates have increased substantially since the mid 1990s and net mass loss more than doubled from an average of 4 50 gt yr 1 between 1993 4 and 1998 9 to 57 105 gt yr 1 between 1998 9 and 2004 this increasing trend is very similar to findings from independent mass budget studies but differs widely from ers radar altimeter results this may result from limitations associated with the large ers footprint over sloping and undulating surfaces that typify fast narrow glaciers where thinning is most pronounced

estimating volume change of mountain glaciers using srtm and map based topographic data this paper describes a method for estimating the volume change of mountain glaciers using the shuttle radar topography mission srtm c band data 2000 and a digital elevation model dem generated from topographic maps this approach was developed with srtm data and topographic maps of 1 25 000 scale 1977 from the akshiirak glaciers tien shan central asia the dem for 1977 was generated using 10 m contour lines from 18 map sheets covering the akshiirak massif and surrounding area the nominal vertical accuracy of the maps is 3 3 m the standard deviation of the differences between the map derived dem and the srtm data on glacier free areas of less than 25deg is 6 3 m a single localized region in the western periphery of the study area with systematic error in the srtm data from 20 to 12 m on a 30 km spatial scale was found and excluded from the error analysis assuming a 10 m map error on the upper snow covered glacier areas the estimated root mean square error of the glacier surface change is 8 2 m from 1977 to 1999 the average glacier surface thinning is 15 1 m and the estimated volume loss is 6 15 km3 the rate of the akshiirak glacier volume loss has increased by 2 7 times compared with historical data from 1943 to 1977 the srtm data show an opportunity for quantifying climatic and dynamic surface elevation changes in mountain glaciers ice cloud and land elevation satellite icesat laser altimetry and srtm data could also be used for the estimation of short term surface changes of mountain glaciers

an active subglacial water system in west antarctica mapped from space satellite laser altimeter elevation profiles from 2003 to 2006 collected over the lower parts of whillans and mercer ice streams west antarctica reveal 14 regions of temporally varying elevation which we interpret as the surface expression of subglacial water movement vertical motion and spatial extent of two of the largest regions are confirmed by satellite image differencing a major previously unknown subglacial lake near the grounding line of whillans ice stream is observed to drain 2 0 cubic kilometers of water into the ocean over 3 years while elsewhere a similar volume of water is being stored subglacially these observations reveal a wide spread dynamic subglacial water system that may exert an important control on ice flow and mass balance

timing of recent accelerations of pine island glacier antarctica 1 we have used interferometric synthetic aperture radar insar data and sequential landsat imagery to identify and temporally constrain two acceleration events on pine island glacier pig these two events are separated by a period of at least seven years 1987 1994 the change in discharge between two flux gates indicates that the majority of the increase in discharge associated with the second acceleration originates well inland 80 km from the grounding line an analysis indicates that changes in driving stress consistent with observed thinning rates are sufficient in magnitude to explain much of the acceleration

rates of southeast greenland ice volume loss from combined icesat and aster observations 1 repeat satellite laser altimetry is critical for observing the rapidly changing mass balance of the greenland ice sheet however sparse sampling and high surface slopes over rapidly thinning coastal outlet glaciers may result in underestimation of mass loss here we supplement icesat derived surface elevation changes with differenced aster digital elevation models of outlet glaciers in southeastern greenland the region with the largest concentrated change in outlet glacier mass loss we estimate a 2002 2005 regional volume loss rate of 108 km3 yr our results are consistent with drainage scale grace and mass budget estimates when differences in observation periods are taken into account the two largest glaciers kangerdlugssuaq and helheim account for only 28 of the mass loss illustrating the combined importance of smaller glaciers and the need for complete observational coverage additionally we find that rapid concentrated thinning within the outlets represents a small contribution to the total volume change compared to dispersed inland thinning

heterogeneous mass loss of glaciers in the aksu tarim catchment central tien shan revealed by 1976 kh 9 hexagon and 2009 spot 5 stereo imagery the meltwater released by the glaciers in the aksu tarim catchment south of tomur peak central tien shan feeds the tarim river which is the main artery for the oases at the northern margin of the taklamakan desert the correct modeling of the contribution of the glaciers meltwater to the total runoff of the tarim river is hampered by the lack of mass balance data multi temporal digital terrain models dtms allow the determination of volume changes for large samples of glacier here we present the mass changes for 12 glaciers using 1976 kh 9 hexagon 2000 srtm3 and 2009 spot 5 datasets the results show that most of the glaciers have been losing mass since 1976 the largest glaciers koxkar and west qongterang lost 0 27 0 15 m w e a 1 and 0 43 0 15 m w e a 1 between 1976 and 2009 despite thick debris cover however some smaller glaciers show mass gain at their tongues indicating glacier surges using srtm3 data the volume gain of qinbingtan glacier no 74 could be dated to the time period 1999 2009 the overall mass budget of 0 33 0 15 m w e a 1 for 1976 2009 of the investigated glaciers is within the variability range of the global average however in the recent years 1999 2009 a slightly decelerated mass loss of 0 23 0 19 m w e a 1 could be observed c 2012 elsevier inc all rights reserved

multi decadal glacier surface lowering in the antarctic peninsula from approximately 400 glaciers of the western antarctic peninsula no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained we seek to address this shortcoming by using surface elevations from usgs and bas airborne 1948 2005 and aster spaceborne 2001 2010 stereo imagery combined by using a rigorous semi automated registration approach to determine multi decadal glacier surface elevation changes in the western antarctic peninsula for 12 glaciers all observed glaciers show near frontal surface lowering and an annual mean lowering rate of 0 28 0 03 m yr at the lower portion of the glaciers during the 4 decades following the mid 1960s with higher rates for the glaciers in the north west parts of the antarctic peninsula increased lowering of up to 0 6 m yr can be observed since the 1990s in close correspondence to increased atmospheric positive degree days in all cases surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude this lowering may have been at least partially compensated for by increased high altitude accumulation

rapid changes in ice discharge from greenland outlet glaciers using satellite derived surface elevation and velocity data we found major short term variations in recent ice discharge and mass loss at two of greenland s largest outlet glaciers their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates likely as a result of fast re equilibration of calving front geometry after retreat total mass loss is a fraction of concurrent gravity derived estimates pointing to an alternative source of loss and the need for high resolution observations of outlet dynamics and glacier geometry for sea level rise predictions

elevation changes measured on svalbard glaciers and ice caps from airborne laser data precise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the svalbard archipelago covering the islands of spitsbergen and nordaustlandet we present the derived elevation changes lower elevation glaciers in south spitsbergen show the largest thinning rates of 0 5 m a 1 while some of the higher more northerly ice caps appear to be close to balance the pattern of elevation change is complex however due to several factors including glacier aspect microclimatological influences and the high natural annual variability in local accumulation and ablation rates anomalous changes were observed on fridtjovbreen which started surging in 1996 at the start of the measurement period on this glacier thinning of 0 6 m a 1 w as observed in the accumulation area coincident with thickening at lower elevations asymmetric thinning was found on two ice caps on nordaustlandet with the largest values on the eastern side of vestfonna but the western slopes of vegafonna the mean elevation change for all ice masses was 0 19 m a 1 w e which is 1 6 times the net mass balance value determined for the last 30 years using mass balance sensitivity estimates for svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s multiple linear regression suggests that mass balance is most closely correlated with latitude rather than mean altitude or longitude

recent dramatic thinning of largest west antarctic ice stream triggered by oceans a growing body of observational data suggests that pine island glacier pig is changing on decadal or shorter timescales these changes may have far reaching consequences for the future of the west antarctic ice sheet wais and global sea levels because of pig s role as the ice sheet s primary drainage portal we test the hypothesis that these changes are triggered by the adjoining ocean specifically we employ an advanced numerical ice flow model to simulate the effects of perturbations at the grounding line on pig s dynamics the speed at which these changes are propagated upstream implies a tight coupling between ice sheet interior and surrounding ocean

dynamic branched fractures in pulverized rocks from a deep borehole pulverized rocks observed in outcrops near large faults are considered to be products of intense fragmentation occurring during strong earthquakes however the exact mechanism and depth of pulverization are controversial here we present an analysis of pulverized rocks along an 930 m interval in a deep borehole in the vicinity of a buried fault cuttings of carbonate lithology from below 4980 m host well preserved sets of dense fractures with a hierarchic branching geometry that was never affected by near surface processes branches are typically symmetric with consistent orientations and hierarchic splitting the main fractures are spaced at 0 1 mm with angular fragments ranging from a few microns to submicrons indicating further intense localized fragmentation splitting of fossils by fractures in the absence of lateral shear proves the tensile origin of the fractures the fracture geometry and density are consistent with dynamic tensile fractures that propagate at critical velocities in laboratory experiments thus these dense branching fractures are the first direct observation that pulverization in fault zones extends to a significant depth and originates from dynamic tensile fracturing

assessment of glacier volume change using aster based surface matching of historical photography glaciated regions are known to be particularly sensitive to climate change historical archives of glacier volume change are important as they provide context for present day changes although photogrammetric archives exist for many regions their usefulness is often limited by a lack of contemporary ground control high quality digital elevation models dems underpin a range of change analysis activities this paper presents a cost effective solution which utilizes advanced spaceborne thermal emission and reflection radiometer aster dems as control for the scaling and orientation of archival data sets instead of relying upon ground control points a robust surface matching algorithm is employed to automatically determine the transformation required to register two overlapping dems through application to the slakbreen glacier system in svalbard norway the strategy is assessed by first matching an aster dem to a fixed lidar reference surface this demonstrates that aster dems are effectively correct in scale supporting their use as a control surface the second stage of the research implements this by matching an aerial photogrammetric dem to an aster reference surface resultant volumetric and annual elevation change rates are compared to those derived from lidar data which are considered in this paper as a truth data set aster based matching produced a mean annual elevation change rate of 4 12 ma 1 compared to a value of 4 11 ma 1 derived from the lidar data in volumetric terms this equates to a difference of 0 6 a major advantage of this approach is the near global coverage offered by aster data and the opportunity that this presents for remote glacial change analysis over regional extents

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

biases of srtm in high mountain areas implications for the monitoring of glacier volume changes because of its nearly global coverage the shuttle radar topographic mission srtm topography is a promising data set for estimating mountain glacier volume changes but first its absolute accuracy must be thoroughly investigated in a glacial environment we use topographic data available in the french alps to assess the usefulness of srtm for the monitoring of glacier volume variations we observe clear biases with altitude both on ice free and glacier covered areas at high altitudes srtm elevations are underestimated by up to 10 m these biases can have a significant impact on any estimate of glacier volume changes if srtm is the most recent of the two compared topographies the volume loss is overestimated and vice versa we cannot conclude definitively on the origin of these biases and whether they affect all high mountain areas but our findings invite reconsideration of previous estimates of glacier wastage based on srtm

kinematics of a deep seated landslide derived from photogrammetric gps and geophysical data the deep seated landslide located at the intersection of the gradenbach and moll valleys near dollach austria has been the target of many previous investigations kronfellner kraus g 1980 neue untersuchungsergebnisse in wildbachen der talzuschub in abhangigkeit von niederschlagen int symp interpraevent bad ischl 1 179 192 weidner s moser m lang e 1998 influence of hydrology on sagging of mountain slopes talzuschube new results of time series analysis 8th international iaeg congress vancouver canada balkema rotterdam 1259 1266 weidner s 2000 kinematik und mechanismus tiefgreifender alpiner hangdeformationen unter besonderer berucksichtigung der hydrologischen verhaltnisse dissertation friedrich alexander universitat erlangen nurnberg 246 in this paper photogrammetric gps and geophysical data have been utilized to derive a constraint on the kinematics of the sagging process the photogrammetric models have been based on aerial photographs from 1962 and 1996 displacement vectors of about 50 individual characteristic points have been determined these clearly show the area of the sagging slope from 1999 to 2004 eleven gps campaigns have been carried out yielding very accurate displacement vectors at four monitoring points information about the internal structure of the slope was determined using seismic surveys the displacements observed by photogrammetry and gps have shown a rather uniform movement of the whole sagging slope with a slight longitudinal compression of 0 6 in order to extend the kinematic consideration to 3d a special form of the equation of continuity conservation of mass has been applied to the 1962 1996 photogrammetric data together with the cross sections derived from the seismic data the average velocities through cross sections have been calculated by integrals of the mass balance above and below these cross sections changes of the total rock mass due to accumulation and especially to erosion as well as an overall compaction of 1 5 between 1962 and 1996 have been considered the calculated average velocities through a cross section and the surface velocities independently determined by photogrammetry agree within an uncertainty of 15 the results indicate a block movement with shear concentration at the basal sliding surface

the influence of local hydrogeologic forcings on near stream event water recharge and retention upper san pedro river arizona the rise in stream stage during high flow events floods can induce losing stream conditions even along stream reaches that are gaining during baseflow conditions the aquifer response to flood events can affect the geochemical composition of both near stream groundwater and post event streamflow but the amount and persistence of recharged floodwater may differ as a function of local hydrogeologic forcings as a result this study focuses on how vertical flood recharge varies under different hydrogeologic forcings and the significance that recharge processes can have on groundwater and streamflow composition after floods river and shallow groundwater samples were collected along three reaches of the upper san pedro river arizona usa before during and after the 2009 and 2010 summer monsoon seasons tracer data from these samples indicate that subsurface floodwater propagation and residence times are strongly controlled by the direction and magnitude of the dominant stream aquifer gradient a reach that is typically strongly gaining shows minimal floodwater retention shortly after large events whereas the moderately gaining and losing reaches can retain recharged floodwater from smaller events for longer periods the moderately gaining reach likely returned flood recharge to the river as flow declined these results indicate that reach scale differences in hydrogeologic forcing can control i the amount of local flood recharge during events and ii the duration of its subsurface retention and possible return to the stream during low flow periods our observations also suggest that the presence of floodwater in year round baseflow is not due to long term storage beneath the streambed along predominantly gaining reaches so three alternative mechanisms are suggested i repeated flooding that drives lateral redistribution of previously recharged floodwater ii vertical recharge on the floodplain during overbank flow events and iii temporal variability in the stream aquifer gradient due to seasonally varying water demands of riparian vegetation copyright 2011 john wiley sons ltd

quantifying groundwater discharge to cockburn river southeastern australia using dissolved gas tracers 222rn and sf6 groundwater discharge to the cockburn river southeast australia has been estimated from comparison of natural 222rn activities in groundwater and river water interpreted using a numerical flow model that simulates longitudinal radon activities as a function of groundwater inflow hyporheic exchange evaporation gas exchange with the atmosphere and radioactive decay an injection of sf6 into the river to estimate the gas transfer velocity assisted in constraining the model previous estimates of groundwater inflow using 222rn activities have not considered possible input of radon due to exchange between river water and water in the hyporheic zone beneath the streambed in this paper radon input due to hyporheic exchange is estimated from measurements of radon production by hyporheic zone sediments and rates of water exchange between the river and the hyporheic zone total groundwater inflow to the cockburn river is estimated to be 18500 m 3 d although failure to consider hyporheic exchange would cause overestimation of the volume of groundwater inflow by approximately 70 copyright 2006 by the american geophysical union

growth of exfoliation joints and near surface stress orientations inferred from fractographic markings observed in the upper aar valley swiss alps abstract granitic rock mass of the upper aar valley grimsel area switzerland contains distinct generations of exfoliation joints which formed during different stages of the pleistocene subparallel to distinct glacial valley palaeotopography the bulk of exfoliation joints shows prominent common fractographic features 1 radial plumose structures with distinct plume axes 2 arrest marks superimposed by plumose striations and 3 gradually developing en echelon fringe cracks multiple arrest marks reveal that exfoliation joints formed incrementally and together with the absence of hackle fringes suggest stable i e subcritical fracturing conditions smooth transitions from plumose structures on the parent plane to en echelon fringe cracks combined with non systematic stepping senses of fringe cracks suggest local vs temporal stress field variations assuming that plume axes formed parallel to the maximum principal compressive stress 1 enables us to infer near surface palaeostress orientations and compare them with classical borehole based in situ stress data the majority of plume axes suggest 1 persistently subhorizontal to slightly inclined 1 orientations at trough valley slopes and 2 near surface variability of 1 orientations originating from topographic perturbation caused by glacial valley erosion superimposed on the regional stress field our investigations of fracture surface morphologies yield unique insights into exfoliation fracture formation such as directional trends of fracture propagation and associated palaeostress orientations within alpine valley slopes

propagation of solutes and pressure into aquifers following river stage rise 1 water level rises associated with river flow events induce both pressure and solute movement into adjacent aquifers at vastly different rates we present a simple analytical solution that relates the travel time and travel distance of solutes into an aquifer following river stage rise to aquifer properties combination with an existing solution for pressure propagation indicates that the ratio of solute to pressure travel times is proportional to the ratio of the volume of water stored in the aquifer before the river stage rise and the volume added by the stage rise and is independent of hydraulic conductivity two dimensional numerical simulations of an aquifer slice perpendicular to a river demonstrate that the solutions are broadly applicable to variably saturated aquifers and partially penetrating rivers the solutions remain applicable where river stage rise and fall occur provided that regional hydraulic gradients are low and the duration of the river stage rise is less than pressure and solute travel times to the observation point in the aquifer consequently the solutions provide new insight into the relationships between aquifer properties and distance and time of solute propagation and in some cases may be used to estimate system characteristics travel time metrics obtained for a flood event in the cockburn river in eastern australia using electrical conductivity measurements enabled estimates of aquifer properties and a lateral extent of river aquifer mixing of 25 m a detailed time series of any soluble tracer with distinctly different concentrations in river water and groundwater may be used

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

an assessment of surface matching for the automated co registration of mola hrsc and hirise dtms abstract martian topographic data has been collected by various exploration missions over the last decade these products provide detailed topographic information and are invaluable for scientists to interpret and understand the geological and climate evolution which has occurred on mars in order to fully utilise these multi sensor multi resolution and multi scale martian topographic products a co registration process has been developed which allows co registration of digital terrain models dtms to be performed to co align these multiple datasets surface matching is the core technique to implement this task and it is here assessed to determine the parameters of the most robust algorithm for dtm co registration once this task was finished the matching tool was developed accordingly with a decision algorithm this algorithm was then employed to align dtms derived from mars orbiter laser altimeter mola high resolution stereo camera hrsc and high resolution imaging science experiment hirise for mola and hrsc dtms the co registration was performed directly as the mola dtm acted as a reference surface within a bundle adjustment process dtms from different versions covering three hrsc orbital strips were used for the assessment process as a result the mean bias of the height differences of a preliminary version hrsc dtm was significantly reduced from 38 596 m to 2 233 m when compared against mola while the bias of a newer dtm was improved from 1 616 m to 0 161 m after matching regarding the co registration of hirise and mola dtms a hierarchical approach employing a hrsc dtm as an intermediate dataset was assessed the results demonstrated that the method is feasible and that the three dtms were co registered effectively due to the success highlighted in this paper a surface matching tool is recommended to be applied to dtms derived from multiple sources before these data are further used moreover surface matching can be considered as an additional step of any workflow for mars dtm creation

relative rates of solute and pressure propagation into heterogeneous alluvial aquifers following river flow events conventional theory for homogeneous aquifers states that pressure propagates more rapidly into aquifers than solutes following river stage rise we demonstrate through numerical simulations of two dimensional aquifer slices that the relative timing of pressure and solute responses in alluvial aquifers is a function of subsurface structures two generic conceptual models of heterogeneity are investigated a vertical clogging layer and a horizontal sand string independent of the conceptual model the hydraulic conductivity contrast is the primary controlling variable on the rates of pressure and solute transport from a river to an observation point conceptual models are compared using metrics for pressure and solute travel time that represent propagation of 50 change in each variable from river to observation point while not possible in a homogeneous system a solute travel time less than a pressure travel time can occur in the presence of both types of heterogeneity and indicates that heterogeneity is controlling propagation from the river to the aquifer less than one order of magnitude contrast in hydraulic conductivities is sufficient to create a travel time ratio less than one contrasts of this magnitude are often exceeded in alluvial environments and thus simultaneous measurement of solute and pressure has the potential to constrain estimates of exchange flux in a way not possible with pressure measurements alone in general flux estimates derived from solute travel times provide more accurate estimates than those derived from pressure responses in heterogeneous environments the magnitude of error in estimates derived from pressure responses is proportional to the hydraulic conductivity contrast travel times calculated from time series pressure and ec data collected in the mitchell river in northern australia are used to demonstrate application of this combined approach

fringe cracks key structures for the interpretation of the progressive alleghanian deformation of the appalachian plateau vertical joints in devonian clastic sedimentary rocks of the finger lakes area of new york state are ornamented with arrays of fringe cracks that reveal the complex deformational history of the appalachian plateau detachment sheet during the alleghanian orogeny three types of fringe cracks were mapped gradual twist hackles abrupt twist hackles and kinks gradual twist hackles are curviplanar en echelon fringe cracks that propagate with an overall vertical direction within the bed hosting the parent crack and are found in all clastic lithologies of the detachment sheet abrupt twist hackles propagate as planar features in thick shale beds above or below the siltstone beds hosting parent joints kinks propagate horizontally as planar surfaces from the tips of parent joints in siltstone beds the breakdown of the parent joint into either gradual or abrupt twist hackles depends on the orientation and magnitude of the remote stress field internal fluid pressure and the elastic properties of the bed the twist angle of gradual twist hackles is larger in coarser clastic beds indicating that stress and internal pressure are more important parameters than elastic properties in controlling breakdown assuming that the vertical stress axis s v equals 78 mpa at 3 km burial depth the difference in twist angle between sandstone and shale beds is used to estimate the maximum horizontal stress difference in the shale beds as s h s h 2 5 mpa when s h s h 12 mpa in sandstone beds the twist angle of the fringe cracks and the abutting relationships of parent joints give an indication of the overall change in stress field orientation within the detachment sheet during alleghanian tectonics these parent joints indicate a regional clockwise stress rotation of alleghanian age concordant with the twist angle of fringe cracks throughout the western part of the study area a counterclockwise twist angle in the eastern portion indicates a local stress attributed to drag where no salt was available to detach the eastern edge of the plateau sheet the clockwise change in stress orientation is consistent with the rotation in stress orientation found in the anthracite belt of the pennsylvania valley and ridge but is opposite to the sense of rotation in the southwestern portion of the detachment sheet western pennsylvania and west virginia the two regional rotation domains are separated by the juniata culmination

space based mapping of glacier changes using aster and gis tools we describe an investigation that combines space based observations of glacier parameters with historical glaciological data derived by traditional means to predict changes in ice extent and volume for the ak shirak range in the interior tien shan of central asia a variety of geographic information systems and photogrammetric tools are used to extract glacier outlines derive of a digital elevation model and compute area versus elevation distribution functions from data acquired by the advanced spaceborne thermal emission and reflection radiometer these products are then used in a glaciological methodology that can predict the response of glacier systems to changes in local climate

glaciers dominate eustatic sea level rise in the 21st century ice loss to the sea currently accounts for virtually all of the sea level rise that is not attributable to ocean warming and about 60 of the ice loss is from glaciers and ice caps rather than from the two ice sheets the contribution of these smaller glaciers has accelerated over the past decade in part due to marked thinning and retreat of marine terminating glaciers associated with a dynamic instability that is generally not considered in mass balance and climate modeling this acceleration of glacier melt may cause 0 1 to 0 25 meter of additional sea level rise by 2100

recent elevation changes on the ice streams and ridges of the ross embayment from icesat crossovers 1 we analyze differences in icesat elevation estimates at orbital crossover locations to determine short term rates of elevation change for small regions within the ross embayment of the west antarctic ice sheet a linear regression of crossover elevation difference against time difference gives an estimate of the mean elevation change rate during the icesat mission to date we observe prevalent elevation change in the south with uplift in the upstream end of kamb ice stream at 0 24 0 30 m a 1 and thinning in the parts of whillans ice stream mercer ice stream and the adjacent conway and engelhardt ice ridges at 0 05 0 18 m a 1 these rates of elevation change are too large to be explained by the 0 02 0 03 m a 1 formal regression error by seasonal height variations or by accumulation or densification rate variability suggesting that they reflect real variations stemming from ice dynamics of the region