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

holocene climate variability archived in the puruogangri ice cap on the central tibetan plateau two ice cores 118 4 and 214 7 m in length were collected in 2000 from the puruogangri ice cap in the center of the tibetan plateau tp in a joint us chinese collaborative project these cores yield paleoclimatic and environmental records extending through the middle holocene and complement previous ice core histories from the dunde and guliya ice caps in northeast and northwest tibet respectively and dasuopu glacier in the himalaya the high resolution puruogangri climate record since ad 1600 details regional temperature and moisture variability the post 1920 period is characterized by above average annual net balance contemporaneous with the greatest 18 o enrichment of the last 400 years consistent with the isotopically inferred warming observed in other tp ice core records on longer timescales the aerosol history reveals large and abrupt events one of which is dated 4 7 kyr bp and occurs close to the time of a drought that extended throughout the tropics and may have been associated with centuries long weakening of the asian indian african monsoon system the puruogangri climate history combined with the other tp ice core records has the potential to provide valuable information on variations in the strength of the monsoon across the tp during the holocene

spatially integrated geodetic glacier mass balance and its uncertainty based on geostatistical analysis application to the western svartisen ice cap norway estimates of glacier mass balance using geodetic methods can differ significantly from estimates using direct glaciological field based measurements to determine if such differences are real or methodological there is a need to improve uncertainty estimates in both methods in this paper we focus on the uncertainty of geodetic methods and describe a geostatistical technique that takes into account the spatial correlation of the elevation differences when calculating spatially averaged elevation changes we apply this method to the western svartisen ice cap norway using elevation differences from the surrounding bedrock derived from stereophotogrammetry we show that the uncertainty is not only dependent on the standard error of the individual elevation differences but is also dependent on the size of the averaging area and the scale of the spatial correlation to assess if the geostatistical analysis made over bedrock is applicable to glacier surfaces we use concurrent photogrammetrical and laser scanning data from bedrock and a range of glacier surfaces to evaluate the dependency of the geostatistical analysis on the surface type the estimated geodetic mass balance and its uncertainty is 2 6 0 9 m w e for the period 1968 85 and 2 0 2 2 m w e for 1985 2002

glacier elevation and mass changes over the central karakoram region estimated from tandem x and srtm x sar digital elevation models snow cover and glaciers in the karakoram region are important freshwater resources for many down river communities as they provide water for irrigation and hydropower a better understanding of current glacier changes is hence an important informational baseline we present glacier elevation changes in the central karakoram region using tandem x and srtm x sar dem differences between 2000 and 2012 we calculated elevation differences for glaciers with advancing and stable termini or surge type glaciers separately using an inventory from a previous study glaciers with stable and advancing termini since the 1970s showed nearly balanced elevation changes of 0 09 0 12 m a 1 on average or mass budgets of 0 01 0 02gt a 1 using a density of 850 kg m 3 our findings are in accordance with previous studies indicating stable or only slightly negative glacier mass balances during recent years in the karakoram the high resolution elevation changes revealed distinct patterns of mass relocation at glacier surfaces during active surge cycles the formation of kinematic waves at quiescent surge type glaciers could be observed and points towards future active surge behaviour our study reveals the potential of the tandem x mission to estimate geodetic glacier mass balances but also points to still existing uncertainties induced by the geodetic method

characteristics of late quaternary monsoonal glaciation on the tibetan plateau and in east asia abstract glaciers fed by monsoonal precipitation are mainly located on the tibetan plateau and easternmost asia these are characterized by simultaneous accumulation and ablation in summer season the southeast part of the tibetan plateau experiences monsoonal precipitation in excess of 1000 mm yr resulting in maritime temperate glaciers in contrast precipitation in the middle and northwest part of the tibet plateau decreases from 1000 to 200 mm yr resulting in the formation of continental cold glaciers during the last glacial the regions of heavy monsoonal precipitation were restricted to the southeast corner of the plateau the westerly weak precipitation zone shifted southward and occupied the major northwest part of the plateau where the extreme continental type glaciers greatly expanded in the eastern margin of asia including taiwan central japan hokkaido and probably mount changbai maritime type glaciers were more extensive because of higher monsoonal precipitation especially heavy snowfall in northwest japan owing to the rich moisture content of the winter monsoon over the japan sea the millennial scale monsoon intensity and glacial cycle in the tibetan plateau are strongly affected by the precession cycle and the orbit inclination cycle which dominate the solar irradiance variation in low latitudes as the high radiation and strong monsoon caused the warmer and wetter climate during 40 30 ka the low radiation produced a weak monsoon and large depression of temperature and precipitation around 21 ka this climatic pattern differs from that in the high latitudes where the eccentricity cycle is prominent the temperature during the last glacial maximum lgm was 6 9 c lower than today on the tibetan plateau and the equilibrium line altitude was depressed by about 1000 m in the southeast part and in the east south and west margins of the plateau where precipitation was high the equilibrium line depression was 500 300 m in the inner and especially the west part of the plateau this variation in equilibrium lines might be caused by the combined effect of the decrease in precipitation the expansion of extreme continental glaciers and the active uplift of glaciated mountains the estimation of a glaciated area of about 350 000 km2 in the tibetan plateau and roughly 500 000 km2 in high asia based on observations of prominent features of lgm glacier extension may be the direct evidence that shows there was no quaternary unified ice sheet developed in the tibetan plateau

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

slight glacier mass loss in the karakoram region during the 1970s to 2000 revealed by kh 9 images and srtm dem an anomalously slight glacier mass gain during 2000 to the 2010s has recently been reported in the karakoram region however to date no investigations of the region wide glacier mass balance in the karakoram prior to 2000 have been reported leaving a knowledge gap for assessing glacier responses to climate change we calculated elevation and mass change using dems generated from kh 9 images acquired during 1973 1980 and the 1 arc second srtm dem we find a slight mass loss of 0 09 0 03 m w e a 1 12 366 km2 for 1973 2000 which is less negative than the global average rate for 1971 2009 0 31 0 19 m w e a 1 within the karakoram the glacier change patterns are spatially and temporally heterogeneous in particular a nearly stable state in the central karakoram 0 04 0 05 m w e a 1 during the period 1974 2000 implies that the karakoram anomaly dates back to the 1970s combined with the previous studies we conclude that the karakoram glaciers as a whole were in a nearly balanced state during the 1970s to the 2010s

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

groundwater recharge through an alluvial fan in the atacama desert northern chile mechanisms magnitudes and causes the chacarilla fan in the atacama desert is one of several formed in the late miocene at the foot of the pre andean cordillera overlying the large complex pampa tamarugal aquifer contained in the continental clastic sediments of the fore arc basin the pampa tamarugal aquifer is a strategic source of water for northern chile but there is continuing doubt over the resource magnitude and recharge during january 2000 a 1 in 4 year storm in the andes delivered a 34 million m3 flash flood to the fan apex where c 70 percolated to the underlying aquifers groundwater recharge through the fan is calculated to be a minimum of 200 l s or 6 of the long term catchment rainfall these figures are supported by hydrochemical data that suggest that recharge may be 9 of long term rainfall isotopic data suggest groundwater less than 50 years old is transmitted westward through the permeable sheetflood sediments of the fan overlying the main aquifer analysis of this and other events shows that the hydrological system is non linear with positive feedback the magnitude of groundwater recharge is dependent on climatic variations antecedent soil moisture storage and changes in channel characteristics long term declines in groundwater level may partly result from climatic fluctuations and the causes of such fluctuations are discussed copyright 2002 john wiley sons ltd

heterogeneous decadal glacier downwasting at the mt everest qomolangma from 2000 to 2012 based on multi baseline bistatic sar interferometry abstract remote sensing based geodetic observations can be used as alternatives data to map glacier height changes because the harsh environment complicates in situ observations in this study we analysed five pairs of x band bistatic terrasar x tandem x images from 2011 and 2014 for mt everest qomolangma glacier height changes were derived using the d insar method respect to srtm dem of 2000 an iterative d insar method using multi baseline bistatic sar interferograms was employed which increased reliability and accuracy of glacier height changing observations from 2000 to 2012 the geodetic glacier mass balance for the mt everest and the surrounding region was 0 38 0 04 m w e a 1 the spatial pattern of the glacier mass loss was heterogeneous the regional heterogeneity may possibly reflect debris covering rates terminating type temperature rising rates and glacier flow rates comparison to long period geodetic glacier mass balance data provided by previous studies since 1970 revealed that our results showed more rapid increases in the glacier mass loss rates after 2000 in the area around khumbu glacier in the southern slope of the mt everest whereas glacier mass loss rates kept stable in the rongbuk catchment at its northern slope

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

glacier mass balance in the qinghai tibet plateau and its surroundings from the mid 1970s to 2000 based on hexagon kh 9 and srtm dems abstract in the context of global warming glacier changes in the qinghai tibet plateau qtp and its surroundings have attracted a great amount of public attention to date there have been many studies of glacier mass balance across the qtp however given that most of the previous studies have focused on a short observation period 2000 2015 and that long term mass change measurements are available only for some local regions we utilized declassified kh 9 images and 1 arc second shuttle radar topography mission srtm digital elevation models dems to provide the region wide mass balance from the mid 1970s to 2000 for a larger scale including 11 sample regions across the qtp and its surroundings the final results indicate that the glaciers in the northwest of the qtp have shown a less negative or near zero mass balance ranging from 0 11 0 13 m w e a 1 to 0 02 0 10 m w e a 1 compared to those in the southeast part with a mass balance range of 0 30 0 12 m w e a 1 to 0 11 0 14 m w e a 1 the most serious mass loss has emerged in the central eastern himalaya integrating our results with the observations after 2000 suggests that over the past four decades mid 1970s to the mid 2010s the glaciers in the himalaya nyainqentanglha and tanggula mountains as a whole have exhibited accelerated mass loss and the most significant acceleration has occurred in the eastern nyainqentanglha moreover the hindu raj glaciers have shown a stable rate of continuous mass loss while a nearly stable or slight mass gain state in the western kunlun region can be dated back to at least as far as the mid 1970s

elevation change of fedchenko glacier pamir mountains from gnss field measurements and tandem x elevation models with a focus on the upper glacier fedchenko glacier experienced a large thickness loss since the first scientific investigations in 1928 as the largest glacier in the pamir mountains this glacier plays an important role for the regional glacier mass budget we use a series of global navigation satellite systems observations from 2009 to 2016 and tandem x elevation models from 2011 to 2016 to investigate recent elevation changes accounting for radar wave penetration minimizes biases in elevation that can otherwise reach up to 6 m in dry snow on fedchenko glacier with mean values of 3 4 m in the high accumulation regions the seasonal elevation changes reach up to 5 m the glacier surface elevation decreased along its entire length over multi year periods thinning rates increased between 2000 and 2016 by a factor of 1 8 compared with 1928 2000 resulting in peak values of 1 5 m a 1 even the highest accumulation basins above 5000 m elevation have been affected by glacier thinning with change rates between 0 2 and 0 4 m a 1 from 2009 to 2016 the estimated glacier wide mass balance rates are 0 27 0 05 m w e a 1 for 2000 to 2011 and 0 51 0 04 m w e a 1 between 2011 and 2016

the termination of the equatorial undercurrent in the eastern pacific abstract the termination of the equatorial undercurrent euc in the eastern tropical pacific has been studied through analysis of the historical hydrographic station data in the region bounded by 5 n 10 s 80 w and 100 w three distinctive hydrographic features associated with the euc are used along with dynamic topography to trace the mean path of the euc and to investigate aspects of its seasonal variation these features are 1 the 13 c thermostad 2 the high salinity core and 3 the high dissolved oxygen concentration tongue the thermostad is thickest just south of the equator to the west of the galapagos islands with a decreasing maximum extending southeast to the coast of south america near 7 s the thermostad is poorly developed in the mean near the equator east of the galapagos islands this pattern appears to be produced by convergence of eastward flow in the euc and in the southern subsurface countercurrent as the euc flows southeastward from the galapagos this interpretation is supported by the geostrophic flow calculated from the mean dynamic topography the isolated high salinity core is found to the south of the equator and is traced all the way to the coast of south america the high oxygen tongue associated with the euc splits at the galapagos with the southward projecting branch disappearing rapidly as an identifiable feature the other branch of the tongue continues around the islands to the north and along the equator to the coast of ecuador some evidence of recirculation of euc water in the south equatorial current is seen to the northwest of the galapagos a strong seasonal pulsation of the euc affects these features in a consistent way with the pulse occurring first west of the galapagos and later along the coast the thermostad first reaches maximum development and then a pronounced downwelling of the thermocline occurs rapidly leading to minimum thermostad extent associated wtih this downwelling is an eastward protruding high salinity tongue near the equator which is later seen as an isolated core along the coast at 4 s and 6 s pressure gradients along the equator and the coast inferred from dynamic topography suggest that this pulse is associated with an increase in the flow of the euc and ultimately the peru chile undercurrent the pressure gradient reversal along the equator occurs prior to the annual wind reversal suggesting that remote forcing plays a role in the seasonal pulse of the euc in the eastern pacific

the depth of penetration in antarctic firn at 10 ghz measurements taken by an x band pulse radar system in east antarctica in 1987 were analyzed to determine the depth of penetration of radar energy in polar firn a minimum estimate of the penetration depth at 10 ghz for the cold and dry polar plateau region is approximately 4 7 m spatial variations in the amount of signal penetration were observed and are related to latitude surface elevation and mean annual temperature the amount of signal penetration and its spatial variation are important factors that should be considered when processing datasets from microwave remote sensing systems that operate in the polar regions

accelerated glacier mass loss 2011 2016 over the puruogangri ice field in the inner tibetan plateau revealed by bistatic insar measurements abstract the temporal variation of glacier mass balance during recent years remains poorly known for the mountain glaciers in the inner tibetan plateau itp due to the lack of field measurements in this study we retrieved the annual glacier mass balance of the puruogangri ice field which is the largest modern ice mass in the itp by differencing multi temporal digital elevation models dems generated with five pairs of tandem x bistatic interferometric synthetic aperture radar insar images acquired between april 2011 and january 2016 we compared the tandem x dems in january and april 2012 to estimate the x band radar penetration depth difference 0 61 0 06 m which enabled systematic bias correction in the estimation of annual glacier mass balance the observed mass balance reveals a glacier mass gain of 0 44 0 10 m w e yr 1 in 2011 12 which was followed by accelerated glacier mass loss in 2012 16 glacier mass balances of 0 13 0 03 0 34 0 06 and 0 52 0 10 m w e yr 1 were estimated for the periods of 2012 13 2013 14 and 2014 16 respectively this accelerating trend of glacier mass loss is likely caused by the continuous decrease in annual precipitation according to the climate data recorded by adjacent meteorological stations this study demonstrates that repeated bistatic insar measurement is a promising method for monitoring glacier elevation change and mass balance at regular intervals

interaction of a river with an alluvial basin aquifer stable isotopes salinity and water budgets summary detailed sets of tracer data isotopes salinity and the results of modflow modeling of water budgets provide an unprecedented opportunity for comparing modeling with field data in the area where the rio grande enters the hueco bolson basin of texas and chihuahua water from the rio grande has recharged the hueco bolson aquifer to a depth of 300 m below the surface in the el paso ciudad juarez area the depth of infiltration corresponding to the depth of ancestral rio grande fluvial sediments groundwater beneath the river exhibits complex isotope and salinity stratification post dam post 1916 type a river water has infiltrated to depths up to 80 m pre dam type b river water has infiltrated to 300 m depth near downtown el paso and has mixed with or been displaced further downstream by high salinity native hueco bolson groundwater type c present in the basin north of the river salinity and isotope boundaries do not correspond precisely isotope stratification corresponds to water residence time and for type c to degree of evaporation the highest salinities are associated with the most evaporated water modeling of water budgets in the basin fill beneath the river predicts present day mixing of water types b and c where changing rates of pumping have caused a reversal of groundwater flow direction between el paso and ciudad juarez and deep recharge of type b water under conditions prevailing in the 1960s

estimating equilibrium line altitude ela from glacier inventory data a glacier s most fundamental altitude is the equilibrium line altitude ela because it divides the glacier into ablation and accumulation areas the best parameterization of the ela for glacier inventory is the balanced budget ela we discuss direct estimation of balanced budget ela from mass balance data for individual glaciers and indirect estimation of balanced budget ela from simple topographic parameters available from the world glacier inventory wgi i e the area median and maximum and minimum altitudes mass balance and ela for individual glaciers are usually strongly correlated and we calculate balanced budget ela from the regression equation linking the two we then compare balanced budget ela with area median and mid range altitudes for the 94 glaciers for which we have all the necessary data the different ela estimates agree well enough 82 to 125 m to describe geographical variations in ela and for application of glacier climate models to glacier inventory data mid range and area median altitudes are already available for tens of thousands of glaciers in the current wgi and should be evaluated in future inventories

heterogeneity in karakoram glacier surges many karakoram glaciers periodically undergo surges during which large volumes of ice and debris are rapidly transported downglacier usually at a rate of 1 2 orders of magnitude greater than during quiescence here we identify eight recent surges in the region and map their surface velocities using cross correlation feature tracking on optical satellite imagery in total we present 44 surface velocity data sets which show that karakoram surges are generally short lived lasting between 3 and 5 years in most cases and have rapid buildup and relaxation phases often lasting less than a year peak velocities of up to 2 km a 1 are reached during summer months and the surges tend to diminish during winter months otherwise they do not follow a clearly identifiable pattern in two of the surges the peak velocity travels down ice through time as a wave which we interpret as a surge front three other surges are characterized by high velocities that occur simultaneously across the entire glacier surface and acceleration and deceleration are close to monotonic there is also no consistent seasonal control on surge initiation or termination we suggest that the differing styles of surge can be partly accounted for by individual glacier configurations and that while some characteristics of karakoram surges are akin to thermally controlled surges elsewhere e g svalbard the dominant surge mechanism remains unclear we thus propose that these surges represent a spectrum of flow instabilities and the processes controlling their evolution may vary on a glacier by glacier basis

early 21st century glacier thickness changes in the central tien shan abstract although studies based on satellite gravimetry 2003 2010 and laser altimetry 2003 2009 measurements have achieved region wide glacier mass change for the tien shan the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately in this study we investigated region wide glacier thickness change in the central tien shan cts during 2000 2012 by differencing the shuttle radar topographic mission srtm digital elevation model dem with a newly constructed dem from 27 tandem x images for a total glacier area of 7239 8 527 2 km 2 an average glacier thickness change rate of 0 24 0 22 m a was derived this result agrees well with the result based on satellite laser altimetry measurements reported earlier 0 31 0 41 m a with temporal synchronization a fine spatial resolution and wide coverage our measurements are able to reveal abundant glacier change features and dependencies in the cts firstly the lower mountains have seen a more severe glacier decline and the glaciers facing the prevailing wind westerlies have experienced a greater decline because of the stronger evaporation furthermore those glaciers lying along the extremely high meridian mountain range have obviously gained mass in their upper reaches because the air current from the west is blocked and lifted by the meridian mountain range secondly for the entire glacier body the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish some huge glaciers covered by heavy debris have still experienced a severe decline however even though the heavy debris did not prevent the ablation its attenuating effects were considerable thirdly for the glaciers that surged before 2000 the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones some large glaciers surged again during 2000 2012 however with much lower magnitudes than in previous surges in general the surge glaciers have experienced a greater decline than the non surge glaciers fourthly due to the ice front calving and subglacial thermal erosion glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land terminated glaciers overall the glaciers in the cts are more stable than those in other parts of the tien shan however the glacier state there is still alarming a moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones

a spatially resolved estimate of high mountain asia glacier mass balances from 2000 to 2016 glacier mass balances in high mountain asia are uncertain satellite stereo imagery allows a spatially resolved estimate for about 92 of the glacierized area and yields a region wide average of about 16 gt yr 1 for 2000 to 2016

massive collapse of two glaciers in western tibet in 2016 after surge like instability surges and glacier avalanches are expressions of glacier instability and among the most dramatic phenomena in the mountain cryosphere until now the catastrophic collapse of a glacier combining the large volume of surges and mobility of ice avalanches has been reported only for the 2002 130 106 m3 detachment of kolka glacier caucasus mountains which has been considered a globally singular event here we report on the similar detachment of the entire lower parts of two adjacent glaciers in western tibet in july and september 2016 leading to an unprecedented pair of giant low angle ice avalanches with volumes of 68 2 106 m3 and 83 2 106 m3 on the basis of satellite remote sensing numerical modelling and field investigations we find that the twin collapses were caused by climate and weather driven external forcing acting on specific polythermal and soft bed glacier properties these factors converged to produce surge like enhancement of driving stresses and massively reduced basal friction connected to subglacial water and fine grained bed lithology to eventually exceed collapse thresholds in resisting forces of the tongues frozen to their bed our findings show that large catastrophic instabilities of low angle glaciers can happen under rare circumstances without historical precedent two catastrophic glacier collapse events in western tibet in 2016 were caused by a convergence of weather and glacier bed conditions according to an analysis of observations and modelling

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

stable isotopic variations in west china a consideration of moisture sources 1 in this study individual precipitation samples collected over 2 years at stations in different climatic regions of west china tibetan plateau region tianshan region and altay were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution our results identify regional patterns in both 18o and deuterium excess d excess defined as d 8 18o and in particular we have identified the northward maximum extent of the southwest monsoon over the tibetan plateau this demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation the patterns we have identified are as follows 1 in the southern tibetan plateau along the southern slope of the himalayas our results show a distinct seasonality for both 18o and d excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport the signals of 18o in the western tibetan plateau reveal that the region receives southwest monsoonal moisture in the east of the plateau stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture 2 in contrast in tianshan there is an apparent temperature effect in 18o with enriched values occurring in summer and depleted values occurring in winter seasonal d excess values opposite to those observed in the southern tibetan plateau are controlled by differing seasonal evaporation conditions 3 in altay the most northern mountain region the seasonal 18o shows the same variation with that in tianshan region however d excess shows no apparent seasonal variation

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

glacier mass changes over duxueshan burog kangri and zangser kangri in the inner tibetan plateau the variation of glacier mass balance during the past decades remains poorly known for duxueshan burog kangri and zangser kangri dbz which are located in the inner tibetan plateau itp a transition zone with shifting influences between the westerlies and the indian summer monsoon in the present study glacier area and mass changes were determined by topographic maps topo landsat imagery and multi temporal digital elevation models dems generated with topo srtm tandem x bistatic interferometric synthetic aperture radar insar images and high mountain asia 8 m dems on average the glaciers showed a slight retreat from 343 27 5 23 km2 in 1971 to 334 67 3 21 km2 in 2018 0 05 0 04 a 1 however glaciers lost mass at a rate of 0 32 0 03 m w e a 1 from 1971 to 2012 for the 1999 2012 and 2012 2017 periods mass balances of 0 03 0 16 and 0 09 0 04 m w e a 1 respectively were observed which represents an approximately equilibrium two glaciers also advanced in our investigation period and we confirmed one of them surged in 2015

multi variable mixing cell model as a calibration and validation tool for hydrogeologic groundwater modeling abstract agricultural irrigation can make substantial changes to groundwater systems this study focuses on an arid area in northern nevada where 100 yr of extensive irrigation has occurred in particular the impacts of long term agricultural activities on the groundwater fluid balance geochemistry and potential changes to the water quality of a nearby river were investigated the study conducted in the fernley basin in western nevada utilized two different modeling approaches to construct a conceptual model that honors both the chemical and physical aspects of the basin groundwater flow regime a multi variable mixing cell model was constructed to represent the hydrochemical approach while a modflow model was constructed to represent the hydrogeological model a geochemical and isotopic analysis of the basin and its margin groundwater was conducted to identify all of the water sources that potentially flow through the basin and all water bodies within the basin those water bodies and sources were incorporated into a mixing cell model that allowed delineation of the general flow lines connecting the different water bodies within the basin with their sources the mixing cell model results were used to calibrate the hydrogeological model until a general agreement between the flow lines of both models was achieved the calibration of the hydrogeologic model included adjustments of the hydraulic conductivities and the use of various interpolation methods the study showed that parallel application of two different modeling approaches the mixing cell model along with a hydrogeological model provides an excellent tool for the validation of the conceptual model moreover it allowed calibration of the hydrogeologic model not only to the water heads as usually done in hydrogeological models but also to the general flow lines that honors the basin geochemistry

modelling the impact of forest cover on groundwater resources a case study of the sherwood sandstone aquifer in the east midlands uk land use change from arable agriculture to forestry has become a focus in many european countries to control leaching of non point agricultural pollutants such as nitrate to aquifers however a reduction in groundwater recharge beneath forest areas could potentially exacerbate water supply shortages no direct study has previously been undertaken in the uk to assess the effect of increasing woodland cover on the quantity of groundwater resources to address this knowledge gap this study applied a groundwater flow model modflow with a soil moisture balance recharge model to predict the effect of land use change to forestry on groundwater recharge and levels by 2025 at two public supply borehole sites on the unconfined sherwood sandstone aquifer in nottinghamshire four land use change scenarios focusing on borehole capture zones were developed the recharge calculations revealed a reduction of up to 45 in annual recharge as a result of an increase in woodland cover in the borehole capture zones with the reduction more marked in winter than in summer at both borehole locations however the associated decrease in groundwater levels was limited owing to the high storage capacity of the sandstone aquifer even with an increase in woodland cover over the entire target zone the simulated decrease in groundwater levels was less than 0 3 m it is concluded that a quantitative analysis using a modelling approach can assist in the better targeting of pollution control strategies that include land use change to woodland helping decision makers balance the expected improvements to groundwater quality while concurrently managing groundwater resources

modelling the effect of forest cover in mitigating nitrate contamination of groundwater a case study of the sherwood sandstone aquifer in the east midlands uk summary as the second largest aquifer in the united kingdom the sherwood sandstone is threatened by high nitrate concentrations and water shortages land use change from arable agriculture to woodland could help mitigate agricultural diffuse pollution and this study provides an evaluation of the effects of woodland cover on groundwater quality six land use change scenarios focusing on two public supply borehole capture zones on the unconfined sherwood sandstone aquifer in nottinghamshire were examined in predictive simulations of nitrate concentrations until 2025 groundwater flow modelling modflow and mass transport modelling mt3dms incorporating outputs from a groundwater recharge model and an export coefficient model enabled a quantitative comparison between different scenarios on groundwater quality results revealed that the greatest decrease by 2025 in nitrate concentration 35 was associated with the entire target zone covered with forest whereas a decrease dependent on the application of best agricultural practice achieved a 20 reduction conversion of 80 ha and 240 ha of agricultural land to woodland in two borehole capture zones with areas of 210 ha and 484 ha respectively could potentially restrict nitrogen losses such that the eu groundwater nitrate limit 50 mg l 1 could be achieved in abstracted groundwater it is concluded that the combination of forest creation and application of best agricultural practice in a borehole capture zone is a recommended approach to control nitrate pollution in the long term and provides scientific support for pollution control strategies that rely on land use change to woodland to achieve water quality objectives

recent slowdown and thinning of debris covered glaciers in south eastern tibet abstract recent large scale remote sensing studies have shown that glacier mass loss in south eastern tibet specifically in the eastern nyainqentanglha range exceeds the average in high asia however detailed studies at individual glaciers are scarce and the drivers behind the observed changes are poorly constrained to date employing feature tracking techniques on terrasar x data for the periods 2008 2009 2012 2013 and 2013 2014 we found measurable surface velocities through to the glacier terminus positions of five debris covered glacier tongues this is contrary to debris covered glaciers in other parts of high asia where stagnant glacier tongues are common our feature tracking results for the 2013 2014 period suggest an average deceleration of 51 when compared with published landsat velocities for the period 1999 2003 further we estimated surface elevation changes for the five glaciers from recently released one arc second resolution elevation data obtained during the shuttle radar topography mission in 2000 and an interferometrical derived tandem x elevation model for the year 2014 with an average rate of 0 83 0 57 m a 1 we confirm strong surface lowering in the region despite the widely discussed insulation effect of debris cover beside the influence of thermokarst processes and delayed response times of debris covered glaciers we highlight that abundant monsoonal summer rainfall might contribute significantly to the pronounced negative mass balances in the study region

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

new vertical modes for dissipative stratified circulations with application to coastal upwelling the method of vertical mode expansions for inviscid time dependent motions is simple and well known see gill 1982 the method simplifies the description of three dimensional stratified circulation by representing each circulation variable as a series expansion of orthogonal functions of z the vertical coordinate several papers for example mccreary 1981 and mccreary and chao 1985 have represented wind forced coastal upwelling in terms of such inviscid modes even when the circulation is viscous by using the inviscid modes however these papers were unable to represent the sea surface density anomaly produced by the wind stress instead of persisting with the vertical modes of the inviscid system this paper derives new viscous vertical modes which have the advantage of allowing nonzero surface density anomalies produced by the vertical diffusion of density anomalies below the surface

combined use of tracer approach and numerical simulation to estimate groundwater recharge in an alluvial aquifer system a case study of nasunogahara area central japan summary in this study we simulate the spatial and temporal distribution of groundwater recharge in an alluvial aquifer system in the nasunogahara area of japan natural stable isotopes 18 o d were considered as additional calibration targets in a numerical model the reliability of the model outputs was further validated by comparing the results from the numerical simulation and an independent tracer approach the results indicated that the calibrated model can effectively simulate the spatial and temporal characteristics of the contribution ratios of recharge sources to groundwater in the nasunogahara area however the tracer approach i e end member mixing analysis provided more reliable results at point scale particularly for the estimated contribution ratios of paddy field water the precipitation in the nasunogahara area is the major recharge source its mean contribution ratio is 58 for a one year period over the entire alluvial fan river seepage is significant in the upstream area of the alluvial fan and the contribution ratio of river waters along the river channels in the upstream area increases during the wet season paddy field water is a highly important recharge source in the midstream and downstream areas of the alluvial fan and the contribution ratio of paddy field water obviously increases from dry season to wet season because of irrigation this study demonstrates that combined use of the tracer approach and numerical simulation with stable isotopes as additional calibration targets can eliminate their respective limitations and can assist in better understanding the groundwater recharge mechanism in alluvial aquifer systems

impact of resolution and radar penetration on glacier elevation changes computed from dem differencing regional glacier mass balances can be measured by subtracting multi temporal digital elevation models dems however dems are often biased with altitude and it remains unclear whether the elevation differences observed on the ice free terrain can be used to correct biases on ice covered areas iwe investigate such altitude related biases using dems from three different sensors spot5 srtm c band and srtm x band the bias due to different original resolutions can be corrected using a relationship between curvature and elevation difference calculated on ice free terrain the impact of c band radar penetration into snow and ice can be evaluated for a specific region by comparing srtm c band and srtm x band dems in our test area karakoram the resolution related bias has a minor influence on region averaged elevation change conversely not accounting for c band penetration would significantly biased the mean elevation change

a model of the equatorial sea surface temperature field and associated circulation dynamics abstract a linear continuously stratified analytical model of the equatorial ocean is developed and used to simulate the major features of the equatorial sea surface temperature sst field and current system the model is bounded by meridional barriers to flow in the east and west and is forced by an idealized southeast trade wind field the steady state response is studied here although the model is time periodic and capable of simulating the annual cycle or a more general time dependence the surface heat flux forcing is set to zero so that the contribution of the equatorial upwelling field in maintaining the cool equatorial surface water can be isolated many of the observed features of the equatorial sst field and current system are simulated the model generates cool sst anomalies an the equator in the eastern half of the basin the cool water core is located to the south of the equator in the easternmost regions of the basin with the coldest water along the eastern boundary the latitudinal and

anthropogenic changes in a confined groundwater flow system in the bangkok basin thailand part i was groundwater recharge enhanced in many asian megacities the excessive use of confined groundwater has caused drastic decline of piezometric level with succeeding severe problems such as land subsidence and groundwater salinisation at the same time it may have enhanced groundwater recharge via an increase in vertical and or lateral hydraulic gradient the strength and spatiotemporal variation of the enhanced recharge are expected to depend on geographical and or hydrogeological settings of an area in question in the present study the bangkok basin in thailand was selected to examine characteristics of enhanced recharge due to excessive pumping we carried out numerical experiments on this phenomenon for half a century using a three dimensional groundwater flow model the model reproduced well observed hydraulic head variations model outputs showed clearly that confined groundwater recharge under natural conditions e g without pumping occurred only in suburban hilly areas corresponding to deep aquifer outcrop areas while recharge was enhanced due not only to suburban pumping urban areas mantled in thick clay i e bangkok metropolitan area recharge flux response to temporal variation in groundwater pumping was faster in urban areas and slower in remote hilly areas on the plain enhanced recharge was more distinct at locations where the bangkok clay is relatively thin these results suggest that piezometric level decline can be mitigated if appropriate sites are selected for groundwater pumping copyright 2011 john wiley sons ltd

glacier mass loss induced the rapid growth of linggo co on the central tibetan plateau remote sensing and gis techniques in conjunction with field investigations show how glacier mass loss has led to the rapid growth of linggo co a glacier fed lake on the central tibetan plateau which has expanded by 21 3 in area between 1974 and 2010 with a lake level rise of 11 2 m the lake volume of linggo co increased at a rate of 0 02 10 6 42 67 10 6 and 65 8 10 6 m 3 a 1 during the periods 1974 92 1992 99 and 1999 2010 respectively other non glacier fed lakes in the vicinity i e longwei co amur co and darngo co ngion shrank considerably from the early 1970s to 1992 and then expanded from 1992 to 2010 despite being in the same climate region linggo co and the non glacier fed lakes have differed in response to climate change the glaciers in the catchment of linggo co retreated by 2 4 in area between 1974 and 2007 and their mean thickness decreased by 6 19 1 91 m between 1974 and 2000 with an associated glacier meltwater runoff of 7 52 2 32 10 8 m 3 the results indicate that glacier mass loss had a significant impact on the growth of linggo co over the past 40 years

recent rapid thinning of the mer de glace glacier derived from satellite optical images the rapid wastage of mountain glaciers and their contribution to sea level rise require worldwide monitoring of their mass balance in this paper we show that changes in glacier thickness can be accurately measured from satellite images we use spot image pairs to build digital elevation models dems of the mont blanc area french alps for different years to register the dems we adjust their longitude latitude and altitude over motionless areas the uncertainty of the thickness change measurement is greatly reduced by averaging over areas covering altitude intervals of 50 m comparisons with topographic profiles and a differential dem from aerial photographs obtained on the mer de glace indicate an overall accuracy of 1 m for the thickness change measurement below 2100 m satellite dems show an evolution of the thinning rate from 1 0 4 m a years 1979 1994 to 4 1 1 7 m a 2000 2003

identification of groundwater recharge sources and processes in a heterogeneous alluvial aquifer results from multi level monitoring of hydrochemistry and environmental isotopes in a riverside agricultural area in korea we evaluated sources and pathways of groundwater recharge for a heterogeneous alluvial aquifer beneath an agricultural field based on multi level monitoring of hydrochemistry and environmental isotopes of a riverside groundwater system at buyeo korea two distinct groundwater zones were identified with depth 1 a shallow oxic groundwater zone characterized by elevated concentrations of no3 and 2 a deeper 10 14 m from the ground surface sub oxic groundwater zone with high concentrations of dissolved fe silica and hco3 but little nitrate the change of redox zones occurred at a depth where the aquifer sediments change from an upper sandy stratum to a silty stratum with mud caps the 18o and 2h values of groundwater were also different between the two zones hydrochemical and 18o 2h data of oxic groundwater are similar to those of soil water this illustrates that recharge of oxic groundwater mainly occurs through direct infiltration of rain and irrigation water in the sandy soil area where vegetable cropping with abundant fertilizer use is predominant oxic groundwater is therefore severely contaminated by agrochemical pollutants such as nitrate in contrast deeper sub oxic groundwater contains only small amounts of dissolved oxygen do and no3 the 3h contents and elevated silica concentrations in sub oxic groundwater indicate a somewhat longer mean residence time of groundwater within this part of the aquifer sub oxic groundwater was also characterized by higher 18o and 2h values and lower d excess values indicating significant evaporation during recharge we suggest that recharge of sub oxic groundwater occurs in the areas of paddy rice fields where standing irrigation and rain water are affected by strong evaporation and that reducing conditions develop during subsequent sub surface infiltration this study illustrates the existence of two groundwater bodies with different recharge processes within an alluvial aquifer copyright 2009 john wiley sons ltd

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

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

quaternary glaciation of puruogangri the largest modern ice field in tibet abstract the puruogangri the largest modern ice field in the tibetan plateau with an area of over 400 km2 in total is in the inner plateau although it is very difficult to reach the scale of the ice field makes it important to study the quaternary glaciation in this inland area to determine whether there was a unified ice sheet in the tibetan plateau during the quaternary field observation showed that five moraine groups termed moraine i v of terminal moraines and lateral moraines are present located from the snouts of modern glaciers to the piedmont based on geomorphic locations stratigraphic correlation relative weathering reworked degrees by wind action and the esr ages of the sands covering the gobi with erratics as well as through comparison with the quaternary glaciations with numerical ages in western chinese mountains these moraine groups represent the modern moraine the little ice age neoglacial the late stage of the last glaciation and the early stage of the last glaciation respectively the granite boulders of moraine v are scattered for 6 km from the mountain front on an extensive peneplain this suggests that the ancient glaciers in the west slope of the ice field advanced to the piedmont during the late pleistocene but did not integrate with the ice in the mountains nearby to form a unified ice sheet

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change