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

a rapidly growing moraine dammed glacial lake on ngozumpa glacier nepal abstract moraine dammed glacial lakes are becoming increasingly common in the himalaya as a result of glacier mass loss causing concern about glacier lake outburst flood risk in addition to extant lakes the potential exists for many more to form as more glaciers ablate down to the level of potential moraine dams in this paper we document the recent rapid growth of a moraine dammed lake on ngozumpa glacier nepal using a combination of ground based mapping and sonar surveys aerial photographs

characteristics and evolution of supraglacial ponds on debris covered tasman glacier new zealand supraglacial ponds on tasman glacier new zealand initiated the development of the large tasman lake during the 1980s and still play an important role for ice loss and further terminus disintegration limnological and glaciological measurements between 2001 and 2003 reveal distinct differences between ponds the hydraulic connection of a pond to the englacial water level exerts a key control on whether the pond contributes to longer term terminus disintegration in the earlier stages of pond development ice loss occurs predominantly in the horizontal dimension by subaerial melt subaqueous calving at later stages plays a major role for ice loss during the capture of a pond by the lake substantial limnological changes lead to changes in relative significance and rates of ice loss processes the most important being the change from melting to predominantly calving as a result ice loss accelerated from around 11 m a 1 of melt under partial debris cover to a retreat by calving and melting of 34 m a 1 ice loss at the ponds accounted for only 10 of the surface loss in the lower terminus area but is likely to increase in the future with enlargement and coalescence of ponds

expansion of a moraine dammed glacial lake tsho rolpa in rolwaling himal nepal himalaya across the surface of debris covered glaciers in the nepal himalayas there are many lakes on the order of 1 km in scale some of the lakes dammed by the end lateral moraine have been expanded from ponds on the order of 100 m in length tsho rolpa glacier lake in the headwater region of the rolwaling valley eastern nepal was probably a small pond in the early 1950s the present expansion rate of the glacial lake is unknown from our investigation of the hydrological and meteorological conditions in 1993 1994 the calculated heat balance in the lake showed a deepening rate of about 1 2 m yr 21 all through the year this is comparable to the mean deepening rate of the bottom basin since 1952 the vertical expansion thus is still continuing annual volume expansion including the calving ice horizontal expansion volume was 3 of the present total volume of the lake

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

a physically based 3 d model of ice cliff evolution over debris covered glaciers we use high resolution digital elevation models dems from unmanned aerial vehicle uav surveys to document the evolution of four ice cliffs on the debris covered tongue of lirung glacier nepal over one ablation season observations show that out of four cliffs three different patterns of evolution emerge i reclining cliffs that flatten during the ablation season ii stable cliffs that maintain a self similar geometry and iii growing cliffs expanding laterally we use the insights from this unique data set to develop a 3 d model of cliff backwasting and evolution that is validated against observations and an independent data set of volume losses the model includes ablation at the cliff surface driven by energy exchange with the atmosphere reburial of cliff cells by surrounding debris and the effect of adjacent ponds the cliff geometry is updated monthly to account for the modifications induced by each of those processes model results indicate that a major factor affecting the survival of steep cliffs is the coupling with ponded water at its base which prevents progressive flattening and possible disappearance of a cliff the radial growth observed at one cliff is explained by higher receipts of longwave and shortwave radiation calculated taking into account atmospheric fluxes shading and the emission of longwave radiation from debris surfaces the model is a clear step forward compared to existing static approaches that calculate atmospheric melt over an invariant cliff geometry and can be used for long term simulations of cliff evolution and to test existing hypotheses about cliffs survival

heterogeneous glacial lake changes and links of lake expansions to the rapid thinning of adjacent glacier termini in the himalayas abstract glacier mass loss in the himalayas has far reaching implications for the alteration of regional hydrologic regimes an increased risk of glacial lake outburst downstream water resource abundance and contributions to sea level rise however the mass losses of himalayan glaciers are not well understood towing to the scarcity of observations and the heterogeneous responses of himalayan glaciers to climate change and local factors e g glacier surge interacting with proglacial lakes in particular there is a lack of understanding on the unique interactions between moraine dammed glacial lakes and their effects on debris cover on valley glacier termini in this study we examined the temporal evolution of 151 large glacial lakes across the himalayas and then classified these glacial lakes into three categories proglacial lakes in contact with full or partial debris covered glaciers debris contact lakes ice cliff contact lakes and non glacier contact lakes the results show that debris contact lakes experienced a dramatic areal increase of 36 5 over the years 2000 to 2014 while the latter two categories of lakes remained generally stable the majority of lake expansions occurred at the glacier front without marked lake level rises this suggests that the rapid expansion of these debris contact lakes can be largely attributed to the thinning of debris covered ice as caused by the melting of glacial fronts and the subsequent glacial retreat we reconstructed the height variations of glacier fronts in contact with 57 different proglacial lakes during the years 2000 to 2014 these reconstructed surface elevation changes of debris covered lake contact glacier fronts reveal significant thinning trends with considerable lowering rates that range from 1 0 to 9 7 m y our study reveals that a substantial average ice thinning of 3 9 m y occurred at the glacier fronts that are in contact with glacial lakes

proglacial lakes character behaviour and geological importance proglacial lakes are ubiquitous within the quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information present deglaciation is increasing the number and size of proglacial lakes around the world this study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective we show how ice marginal or ice contact lakes and other distal proglacial lakes can be distinguished from each other by geomorphological sedimentological chemical and biological characteristics the key controls on proglacial lake geomorphology and sedimentology are outlined and discussed proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation proglacial lakes interrupt meltwater flux and are very efficient sediment traps hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the quaternary overall analyses of proglacial lakes can provide a valuable insight into i patterns character and behaviour of mountain glaciers ice sheets and glaciations and ii the impacts of past present and future deglaciation

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

remote sensing based analysis of the 1996 surge of northern inylchek glacier central tien shan kyrgyzstan the evolution of northern inylchek glacier and its proglacial lake upper lake merzbacher during its 1996 surge and the surrounding decades is analyzed with remote sensing imagery overall retreat of the glacier from 1943 to 1996 enlarged the lake to 4 km long and 100 m deep the surge in 1996 initiated between 12 september and 7 october and advanced the glacier by 3 7 km to override most of upper lake merzbacher the surge phase probably ended in december 1996 and involved mean flow velocities across the lower trunk of the glacier that reached 50 m d 1 over a 32 day period water displaced by the surge from upper lake merzbacher totalling 1 5 108 m3 in volume accelerated filling of lower lake merzbacher downvalley and helped trigger this marginal ice dammed lake to outburst in a jokulhlaup around late november early december the characteristics and duration of the surge render it as similar to temperate glacier surges elsewhere it may have been facilitated by low basal friction caused by water saturated sediments in the upper lake bed furthermore bathymetric measurements show that the surge evacuated much sediment into the upper lake causing its depth to reduce from 20 to 30 m in 1996 to 8 m by 2005 and 2 m by 2011 the corresponding deposition rates imply glacier catchment specific mean sediment yields of 1 4 to 3 4 103 mg km 2 a 1 in the years after the surge our study documents novel interactions within a cascade system of glaciers and lakes that exhibits surging and outburst flood behavior

topographic effects on the thermal structure of himalayan glacial lakes observations and numerical simulation of wind abstract the thermal structure of two himalayan glacial lakes tsho rolpa and imja in the eastern nepal was examined by observations in the pre monsoon seasons of 1996 and 1997 tsho rolpa had an isothermal mixed layer at water depths of 0 20 m whereas imja did not possess such an isothermal layer this difference in the thermal structure is explained by the condition that diurnal valley winds producing wind driven currents blow strongly near the water surface of tsho rolpa but very weakly near that of imja the wind observations above or near the end moraine indicated that a daily wind system of strong diurnal valley winds and weak nocturnal mountain winds is common to the lakes it was suggested that with respect to the valley winds the weak winds near the surface of imja result from topographic screening effects of the upwind dead ice zone and end moraine 20 25 m higher than the water surface in order to ascertain the topographic effects three dimensional numerical simulation of airflow was carried out by making topographic models of actual size in the calculation domain corresponding to tsho rolpa and imja and their surrounding topography the simulation revealed that when winds blow at constant velocities of 1 5 m s 1 at 2 m above the points corresponding to the weather stations the wind velocity at 2 m above the water surface for imja is 33 42 smaller than for tsho rolpa with increasing heights of the end moraine and dead ice zone the wind velocity near the lake surface efficiently decreased by decreasing the lake length from 3 1 or 2 2 km to 1 2 km

hydrology of debris covered glaciers in high mountain asia abstract the hydrological characteristics of debris covered glaciers are known to be fundamentally different from those of clean ice glaciers even within the same climatological geological and geomorphological setting understanding how these characteristics influence the timing and magnitude of meltwater discharge is particularly important for regions where downstream communities rely on this resource for sanitation irrigation and hydropower such as high mountain asia the hydrology of debris covered glaciers is complex rugged surface topographies typically route meltwater through compound supraglacial englacial systems involving both channels and ponds as well as pathways that remain unknown low gradient tongues that extend several kilometres retard water conveyance and promote englacial storage englacial conduits are frequently abandoned and reactivated as water supply changes new lines of permeability are exploited and drainage is captured due to high rates of surface and subsurface change seasonal influences such as the monsoon are superimposed on these distinctive characteristics reorganising surface and subsurface drainage rapidly from one season to the next recent advances in understanding have mostly come from studies aimed at quantifying and describing supraglacial processes little is known about the subsurface hydrology particularly the nature or even existence of subglacial drainage in this review we consider in turn the supraglacial englacial subglacial and proglacial hydrological domains of debris covered glaciers in high mountain asia we summarise different lines of evidence to establish the current state of knowledge and in doing so identify major knowledge gaps finally we use this information to suggest six themes for future hydrological research at high mountain asian debris covered glaciers in order to make timely long term predictions of changes in the water they supply

performance of aster and srtm dems and their potential for assessing glacial lakes in the lunana region bhutan himalaya to assess the potential volume of a glacial lake outburst flood glof more precisely than in previous studies we analyze ground survey data and remote sensing digital elevation models dems around glacial lakes in the lunana region bhutan based on a dem generated from differential gps ground surveys we first evaluate the relative accuracies of dems produced by the advanced spaceborne thermal emission and reflection radiometer aster and the shuttle radar topography mission srtm root mean square errors of the altitudinal difference between these dems and ground survey data were 11 0 m for aster and 11 3 m for srtm these errors are similar to those of previous studies we show that a topographical classification allows a better estimate of elevation on lakes ponds riverbeds and glaciers due to their flat surfaces while the relative accuracy is worse over moraines and hill slopes due to their narrow ridges and steep slopes using the optical satellite images and the ground survey data we re evaluate the glof volume in 1994 as 17 2 5 3 10 6 m 3 we show glof related information such as distance altitudinal difference and gradient at possible outburst points where the lake level is higher than the neighboring riverbed and or glacial lake

investigating the complex interface where bedrock transforms to regolith abstract the interface where bedrock transforms to regolith is not planar but rather has a roughness that varies with the scale of observation the complexity of this surface is manifested in both element depth and fragment size depth distributions and may sometimes be related to the longitudinal profiles of watershed streams the fractal nature of the bedrock regolith interface means that the interface has a thickness which is 20 m in two ridgetop examples from pennsylvania and puerto rico such weathering thicknesses modeled as a function of one dimensional fluid flow are affected by the balance between rates of weathering and erosion one dimensional models are consistent with weathering advance rates that vary with equilibrium solubility and porefluid velocities and not reaction kinetics however fluid flow is not strictly downward and one dimensional permeability of regolith changes as particle size and bulk density changes with depth thus both downward and lateral flow occurs especially at reaction fronts where reactions change permeability the rate of weathering advance is therefore affected by the 3 dimensional distribution of reaction zones that affect permeability across the watershed quantitative models of such phenomena over a range of spatial and temporal scales are needed

heterogeneity of glacial lake expansion and its contrasting signals with climate change in tarim basin central asia on the basis of landsat tm etm oli imagery in the years 1990 2000 and 2013 changes of lake area were detected and its contrasting signals with climate change are addressed for tarim basin in central asia during the past 23 years the lake area has expanded at an average rate of 0 67 a with the fastest rates in altun shan and tian shan mountains and slower rates in the karakoram and pamir which indicates spatially heterogeneous warmer and wetter climatic signals in the basin examining decades the average expansion rate of lake area 0 98 a over 2000 2013 was about four times that 0 23 a of 1990 2000 indicating accelerated warmer wetter trends around the transition year 2000 in the mountain areas discrepant area expansion of different types of glacial lake implies contrasting signals of climate change in the tarim basin fewer direct climatic signals can be inferred from changes of supraglacial lakes ice contacting lakes characterized by the fastest expansion rate 3 35 a depict accelerated glacier shrinkage caused by climate warming non glacier fed lakes expansion at the rate of 0 57 a reflect an apparent increase of precipitation in the mountains of tarim basin

evolution of a debris covered glacier in the western himalaya during the last four decades 1971 2016 a multiparametric assessment using remote sensing and field observations abstract this study assesses the response of the panchi nala glacier bhaga basin western himalaya to climate change by monitoring multiple glacier parameters namely length area debris cover snowline altitude sla surface ice velocity siv and surface elevation change h these parameters were analysed using high resolution satellite images corona kh 4b and sentinel 2 msi and medium resolution ones landsat tm etm oli and terra aster acquired between 1971 and 2016 along with extensive field observations considering only dimensional changes the glacier appears to have low rates of recession 4 54 2 56 m y 1 and deglaciation 0 11 0 04 y 1 over the study period 1971 2016 however siv and h values reveal a significant slowdown 33 87 1992 93 2015 16 and an extensive lowering 1 62 0 06 m y 1 2000 2013 on the glacier the debris cover area and sla also increased by 23 50 1 74 and 287 63 m respectively during 1971 2016 increase in the mean winter minimum temperature and decrease in the winter snowfall are probably the main drivers of glacier depletion we conclude that the significant slowdown extensive surface lowering development of a proglacial lake and appearance of the supraglacial lakes collectively indicate a severe glacier degeneration this forewarns that the glacier may experience an accelerated pace of wastage in the future

a regional scale assessment of himalayan glacial lake changes using satellite observations from 1990 to 2015 abstract the himalaya the world s highest mountain ranges are home to a large group of glaciers and glacial lakes glacial lake outburst floods glofs in this region have resulted in catastrophic damages and fatalities in the past decades the recent warming has caused dramatic glacial lake changes and increased potential glof risk in the himalaya however our knowledge on the current state and change of glacial lakes in the entire himalaya is limited this study maps the current 2015 distribution of glacial lakes across the entire himalaya and monitors the spatially explicit evolution of glacial lakes over five time periods from 1990 to 2015 using a total of 348 landsat images at 30 m resolution the results show that 4950 glacial lakes in 2015 cover a total area of 455 3 72 7 km2 mainly located between 4000 m and 5700 m above sea level himalayan glacial lakes expanded by approximately 14 1 from 1990 to 2015 the changing patterns of supraglacial lakes and proglacial lakes are rather complex involving both lake disappearance and emergence many emergent glacial lakes are found at higher elevations especially the new proglacial lakes which have formed as a result of glacier retreat spatially heterogeneous changes of himalayan glacial lakes are observed with the most significant expansion occurring in the southern slopes of the central himalaya increasing glacier meltwater induced by the himalayan atmospheric warming is a primary cause for the observed lake expansion this study provides primary data for future glof risk assessments a total of 118 rapidly expanded glacial lakes are identified as potential vulnerable lakes for the priority of risk assessment

thermo erosional notch development at fresh water calving tasman glacier new zealand controls on glacier calving rates are receiving increased scientific interest at fresh water calving glaciers limnological factors might be more important than glaciological ones measurements of thermo erosional notch development at the calving ice cliff of tasman glacier new zealand suggest that the calving rates at this glacier are directly controlled by the rate of thermal undercutting notch formation rates typically vary between 10 and 30 cm d 1 maximum rate 65 cm d 1 in summer corresponding to an average calving rate of 34 m a 1 notch formation is slower than waterline melt and is controlled by water temperatures and circulation cliff geometry debris supply and water level fluctuations the latter shift the position of undercutting resetting the level of the notch formation process and thereby slowing it the geometry of the notch and the debris supply determine the extent of influence of the lake on notch water temperatures and circulation hence water temperatures in the lake are not necessarily indicative of the rate of notch formation the prediction of rate of notch formation from far field variables is hampered by the complex interaction of the influencing factors the significance of thermal undercutting as a calving rate controlling process decreases with increasing ice velocities calving rates and surface gradients

growth and drainage of supraglacial lakes on debris mantled ngozumpa glacier khumbu himal nepal ablation of debris mantled glaciers in nepal has resulted in the formation of several potentially unstable moraine dammed lakes some of which constitute serious hazards ngozumpa glacier khumbu himal has undergone significant downwasting in recent decades and is believed to lie close to the threshold for moraine dammed lake formation the debris mantled ablation area of the glacier is studded with numerous supraglacial lakes the majority of which occupy closed basins with no perennial connections to the englacial drainage system perched lakes perched lakes can undergo rapid growth by subaerial and water line melting of exposed ice faces and calving subaerial and subaqueous melting beneath thick 1 m debris mantles is comparatively insignificant although lake expansion can contribute substantially to ablation of the glacier perched lakes cannot continue to grow indefinitely but are subject to rapid drainage once a connection is made to englacial conduits the level of one of the lakes on the ngozumpa however is controlled by the altitude of a spillway through the lateral moraine of the glacier this lake underwent only limited growth in the period 1998 2000 but is likely to experience monotonic growth if glacier mass balance continues to be negative

recent glacier and glacial lake changes and their interactions in the bugyai kangri southeast tibet glaciers in the bugyai kangri are located in a transition zone from southeast tibet where monsoonal temperate glaciers dominate to inner tibet where continental glaciers dominate here we analyze glacier and glacial lake changes in this region using multi year inventories based on landsat images from 1981 2013 results show that the total area of 141 glaciers in the region decreased by 30 44 0 89 km 2 from 198 35 9 54km 2 1980s to 167 93 4 52 km 2 2010s the annual area shrinkage rate 0 48 a 1 is lower than that reported for southeastern tibet but higher than that of inner tibet both the number and total area of glacial lakes increased between 1981 and 2013 among all lakes proglacial lakes contribute most similar to 81 to the expansion the total area of ten proglacial lakes increased by 150 3 13 17 and of these ten lakes the four that expanded most sharply showed increased calving at their upper margins resulting in more rapid retreat of lake terminating glaciers than land terminating glaciers owing to rapid calving several lakes may undergo further growth in the near future increasing the potential risk of glacial lake outburst floods

volume calculation and analysis of the changes in moraine dammed lakes in the north himalaya a case study of longbasaba lake glacial lake outburst flood hazards in the himalayan region have received considerable attention in recent years accurate volume estimation for glacial lakes is important for calculating outburst flood peak discharge and simulating flood evolution longbasaba lake a potentially dangerous moraine dammed lake is located on the north side of the himalaya its depth was surveyed using the syqwest hydrobox high resolution echo sounder and 6916 measurements were collected in september 2009 the maximum and average depths of the lake were 102 2 and 48 2 m respectively the morphology of the lake basin was modeled by constructing a triangulated irregular network and the lake was found to have a storage capacity of 0 064 0 002 km 3 multi source remote sensing images from landsat mss landsat tm etm and terra aster and a topographic map were digitized to delineate the outlines of the lake between 1977 and 2009 the results indicate that the length and area of the lake have increased during the past 32 years with a drastic expansion occurring since 2000 based on volume and area data of longbasaba lake in different periods we deduced an empirical equation of the lake volume area relationship that can be used to calculate the storage capacity of similar moraine dammed lakes in the himalayan region

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

modelling outburst floods from moraine dammed glacial lakes in response to climatic change the size and number of moraine dammed supraglacial and proglacial lake systems have increased dramatically in recent decades given an appropriate trigger the natural moraine dams that impound these proglacial lakes are breached producing catastrophic glacial lake outburst floods glofs these floods are highly complex phenomena with flood characteristics controlled in the first instance by the style of breach formation downstream glofs typically exhibit transient often non newtonian fluid dynamics as a result of high rates of sediment entrainment from the dam structure and channel boundaries combined these characteristics introduce numerous modelling challenges in this review the historical contemporary and emerging approaches available to model the individual stages or components of a glof event are introduced and discussed a number of methods exist to model the stages of a glof event dam breach models can be categorised as being empirical analytical or numerical in nature with each method having significant advantages and shortcomings empirical relationships that produce estimates of peak discharge and time to peak are straightforward to implement but the applicability of these models is often limited by the nature of the case study data from which they are derived furthermore empirical models neglect the inclusion of basic hydraulic principles that describe the mechanics of breach formation analytical or parametric models simulate breach development using simplified versions of the physically based equations that describe breach enlargement whilst complex physically based codes represent the state of the art in numerical dam breach modelling to date few of the latter have been applied to investigate the moraine dam failure problem despite significant advances in the physical complexity and availability of higher order hydrodynamic solvers the majority of published accounts that have attempted to reconstruct or predict glof characteristics have been limited often by necessity to the use of relatively simplistic models this is in part attributable to the unavailability of terrain models of many high mountain catchments at the fine spatial resolutions required for the effective application of numerically sophisticated codes and their proprietary and often cost prohibitive nature however advanced models are experiencing increasing use in the glacial hazards literature in particular the suitability of emerging mesh free particle based methods for simulating dam breach and glof routing may represent a solution to many of the challenges associated with modelling this complex phenomenon sources of uncertainty in the glof modelling chain have been identified by various workers however to date their significance for the robustness of reconstructive and predictive modelling efforts have been largely unexplored and quantified in detail these sources include the geometric and material characterisation of moraine dam complexes including lake bathymetry and the presence and extent of buried ice initial conditions freeboard precise spillway dimensions spatial discretisation of the down valley domain hydrodynamic model dimensionality and the dynamic coupling of successive components in the glof model cascade

quantifying ice cliff evolution with multi temporal point clouds on the debris covered khumbu glacier nepal measurements of glacier ice cliff evolution are sparse but where they do exist they indicate that such areas of exposed ice contribute a disproportionate amount of melt to the glacier ablation budget we used structure from motion sfm photogrammetry with multi view stereo mvs to derive 3d point clouds for nine ice cliffs on khumbu glacier nepal in november 2015 may 2016 and october 2016 by differencing these clouds we could quantify the magnitude seasonality and spatial variability of ice cliff retreat mean retreat rates of 0 30 to 1 49 cm d 1 were observed during the winter interval november 2015 to may 2016 and 0 74 to 5 18 cm d 1 were observed during the summer may 2016 to october 2016 four ice cliffs which all featured supraglacial ponds persisted over the full study period in contrast ice cliffs without a pond or with a steep back slope degraded over the same period the rate of thermo erosional undercutting was over double that of subaerial retreat overall 3d topographic differencing allowed an improved process based understanding of cliff evolution and cliff pond coupling which will become increasingly important for monitoring and modelling the evolution of thinning debris covered glaciers

thermal regime of a supraglacial lake on the debris covered koxkar glacier southwest tianshan china a supraglacial lake was surveyed on the koxkar glacier in southwest tianshan from july to september 2007 and july to september 2008 and the temperature variation characteristics of the lake debris and debris free ice were analyzed at different depths to determine the thermal regimes in addition the discrepancies of temperature variation characteristics were investigated for different geomorphic units of the ablation zone of the koxkar glacier it was found that daily temperature variation curves for deep water are v shaped because meltwater from the glacier surface at temperatures of around 0 c feeds the lake and mixes with the relatively high temperature surface water during the day as the water temperature rises to approximately 4 c the mixed water sinks and forms a low temperature trough in the deep water of the lake in the middle of the day the vertical lapse rate of the lake water temperature against depth 0 33 c m has a magnitude lower than that of the debris 4 29 c m and that of the debris free ice 0 38 c m in the koxkar glacier s ablation zone the temperature curve for the surface water largely varied between the temperature curves for the debris at depths of 0 2 and 0 5 m the surface thermal condition of the ablation zone is significantly affected by the daily weather and there is a limited influence in debris at a depth of 1 m and in the lake at a depth of 5 m

high resolution monitoring of himalayan glacier dynamics using unmanned aerial vehicles himalayan glacier tongues are commonly debris covered and they are an important source of melt water however they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles observations of debris covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space borne remote sensing in this study we deploy an unmanned aerial vehicle uav before and after the melt and monsoon season may and october 2013 over the debris covered tongue of the lirung glacier in nepal based on stereo imaging and the structure for motion algorithm we derive highly detailed ortho mosaics and digital elevation models dems which we geometrically correct using differential gps observations collected in the field based on dem differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy on average mass loss is limited and the surface velocity is very small however the spatial variability of melt rates is very high and ice cliffs and supra glacial ponds show mass losses that can be an order of magnitude higher than the average we suggest that future research should focus on the interaction between supra glacial ponds ice cliffs and englacial hydrology to further understand the dynamics of debris covered glaciers finally we conclude that uav deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features

the temporal significance of transitions from melting to calving termini at glaciers in the central southern alps of new zealand termini of valley glaciers in the central southern alps are undergoing a three phase sequence of retreat that began in the 1950s an initial phase of melting and slow downwasting under thickening supraglacial debris mantles is associated with stationary or slowly retreating termini this is followed by a transitional phase of disruption of insulating debris mantles allowing the rapid growth of shallow thermokarst lakes the shape and location of which vary according to glacier gradient and marginal topography a third phase of rapid calving retreat of ice cliffs into deepening proglacial lakes develops from the transitional phase at no stage are terminal responses simply related to climate present transitions to calving retreat are related to the morphology of glacier termini particularly to large outwash heads landform evidence indicates that similar calving phases do not appear to have occurred since late pleistocene deglaciation so that present changes to glacier termini are of great significance

the sustainability of water resources in high mountain asia in the context of recent and future glacier change high mountain asia contains the largest volume of glacier ice outside the polar regions and contain the headwaters of some of the largest rivers in central asia these glaciers are losing mass at a mean rate of between 0 18 and 0 5 m water equivalent per year while glaciers in the himalaya are generally shrinking those in the karakoram have experienced a slight mass gain both changes have occurred in response to rising air temperatures due to northern hemisphere climate change in the westerly influenced indus catchment glacier meltwater makes up a large proportion of the hydrological budget and loss of glacier mass will ultimately lead to a decrease in water supplies in the monsoon influenced ganges and brahmaputra catchments the contribution of glacial meltwater is relatively small compared to the indus and the decrease in annual water supplies will be less dramatic therefore enhanced glacier melt will increase river flows until the middle of the twenty first century but in the longer term into the latter part of this century river flows will decline as glaciers shrink declining meltwater supplies may be compensated by increases in precipitation but this could exacerbate the risk of flooding

ice cliff dynamics in the everest region of the central himalaya the importance of ice cliffs for glacier scale ablation on debris covered glaciers is now widely recognised however a paucity of data exists to describe the spatio temporal distribution of ice cliffs in this study we analysed the position and geometry of 8229 ice cliffs and 5582 supraglacial ponds on 14 glaciers in the everest region between 2000 and 2015 we observed notable ice cliff and pond spatial coincidence on average across our study glaciers 77 of supraglacial pond area was associated with an adjacent ice cliff and 49 of ice cliffs featured an adjacent supraglacial pond the spatial density of ice cliffs was not directly related to glacier velocity but did peak within zones of active ice furthermore we found that ice cliff density was glacier specific temporally variable and was positively correlated with surface lowering and decreasing debris thickness for individual glaciers ice cliffs predominantly had a north facing commonly north westerly aspect which was independent of glacier flow direction thereby signifying a strong solar radiation control on cliff evolution independent field observations indicated that cliff morphology was related to aspect local debris thickness and presence of a supraglacial pond and highlighted the importance of surface runnel formation which acts as a preferential pathway for meltwater and debris fluxes overall by coupling remote sensing and in situ observations it has been possible to capture local and glacier scale ice cliff dynamics across 14 glaciers which is necessary if explicit parameterisation of ice cliffs in dynamic glacier models is to be achieved

object based analysis of unmanned aerial vehicle imagery to map and characterise surface features on a debris covered glacier debris covered glaciers in the himalaya may have spatially averaged rates of surface height change that are similar to those observed on bare ice glaciers despite the insulating effects of thick debris spatially heterogeneous melt patterns caused by the development and evolution of ice cliffs and supraglacial pond systems result in substantial mass losses over time however mechanisms controlling the formation and survival of cliffs and ponds remain largely unknown to study the distribution and characteristics of these surface features we deploy an unmanned aerial vehicle uav over a stretch of the debris covered langtang glacier nepal acquired images are processed into high resolution orthomosaics and elevation models with the structure from motion sfm photogrammetry algorithm ice cliffs and ponds are classified using object based image analysis obia and their morphology and spatial distribution are analysed and evaluated using object pixel and point cloud approaches results show that ice cliffs are predominantly north facing and larger ice cliffs are generally coupled with supraglacial ponds which may affect their evolution considerably the spatial distribution of ice cliffs indicates that they are more likely to form in areas where high strain rates are expected the spatial configuration of ponds over the entire tongue reveals high pond density near confluences possibly due to closure of conduits via transverse compression we conclude that the combination of obia and uav imagery is a valuable tool in the semi automatic and objective analysis of surface features on debris covered glaciers the technique may also have potential for upscaling to the use of spaceborne imagery and the use of uav derived point clouds to analyse ice cliff undercuts is promising

a conceptual model of supra glacial lake formation on debris covered glaciers based on gpr facies analysis jordan r mertes acknowledges funding from michigan technological university and the michigan technological university 2016 fall finishing fellowship sarah s thompson acknowledges funding from the university centre in svalbard unis and the european commission fp7 mc ief

thermal structure of proglacial lakes in patagonia calving glaciers are rapidly retreating in many regions under the influence of ice water interactions at the glacier front in contrast to the numerous researches conducted on fjords in front of tidewater glaciers very few studies have been reported on lakes in which freshwater calving glaciers terminate to better understand ice water interactions at the front of freshwater calving glaciers we measured lakewater temperature turbidity and bathymetry near glaciar perito moreno upsala and viedma large calving glaciers of the southern patagonia icefield the thermal structures of these lakes were significantly different from those reported in glacial fjords there was no indication of upwelling subglacial meltwater instead turbid and cold glacial water discharge filled the region near the lake bottom this was because water density was controlled by suspended sediment concentrations rather than by water temperature near surface wind driven circulation reaches a depth of 180 m forming a relatively warm isothermal layer mean temperature of 5 6 c at perito moreno 3 4 c at upsala and 6 7 c at viedma which should convey heat energy to the ice water interface however the deeper part of the glacier front is in contact with stratified cold water implying a limited amount of melting there in the lake in front of glaciar viedma the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature our results revealed a previously unexplored thermal structure of proglacial lakes in patagonia suggesting its importance in the subaqueous melting of freshwater calving glaciers

morphometric evolution of everest region debris covered glaciers abstract debris covered glaciers in the central himalaya have now experienced several decades of sustained ice loss manifested predominantly in glacier surface lowering in particular glacier surfaces of low longitudinal gradient and low ice surface velocity have developed locally complex surface topographies and undergone profound changes in supraglacial hydrology in this study we examine the development of complex ice surface topography across six debris covered glaciers in the everest region over the last four decades via a new metric of glacier surface relief applied to digital elevation models dems we focus in on khumbu glacier and use fine spatial and temporal resolution dems covering a period of 28 months to quantify the contemporary contribution of ice cliff and supraglacial pond expansion to overall mass loss from stagnant areas of ice on the broader scale we find three common long term changes in glacier surface topography 1 glacier wide expansion of high relief topography in response to ice cliff and supraglacial pond network evolution 2 up glacier expansion of high local relief zones that may be caused by differential sub debris melt beneath thin debris and 3 increase in glacier surface relief proximal to glacier termini caused by supraglacial stream incision where linked proglacial supraglacial hydrological networks exist overall we contend that these topographic measurements will be important for understanding glacier surface water storage and also the energy balance of a debris covered glacier surface both of which could exacerbate future ice loss and downstream meltwater supply

interannual flow dynamics driven by frontal retreat of a lake terminating glacier in the chinese central himalaya abstract most lake terminating glaciers in the himalaya retreat rapidly due to periodic frontal ice loss at their terminus but long term observations are still limited regarding their flow dynamics which is crucial for understanding the processes of ice mass loss and proglacial lake growth we present multi decadal surface velocity dynamics of the longbasaba glacier a rapid retreating lake terminating glacier in the chinese himalaya using an image feature tracking method applied on optical satellite images between 1989 and 2018 we show that in companion with rapid retreat 51 7 m a 1 its lower 5 km tongue experienced high interannual fluctuations in velocity comprising periodic acceleration and slowdown in 1989 1995 and 2001 2010 and a recent remarkable acceleration since 2012 the temporal variation of longitudinal velocity distribution indicates an upward propagation of the lake ward acceleration namely a downglacier inversion of strain from compression to extension this propagation is coupled to the retreat of the glacier front and occurs along the lowermost 1 1 5 km lake adjacent section as the proglacial lake expands the most recent acceleration of the near lake section since 2012 has likely facilitated a dynamic thinning on its upper sections where flow acceleration started two years later in 2014 this pattern contrasts markedly with a nearby decelerating land terminating glacier which has experienced a much slower retreat rate 7 8 m a 1 and the same magnitude of mean thinning rate at its lower part since 2000 our results confirm the strong influence of the proglacial lake on ice flow dynamics and suggest that lake ice interactions are important to consider when analyzing interpreting or modeling dynamics of rapidly retreating lake terminating glaciers in the himalayas as well as around the world

onset of calving at supraglacial lakes on debris covered glaciers of the nepal himalaya field surveys of supraglacial ponds on debris covered glaciers in the nepal himalaya clarify that ice cliff calving occurs when the fetch exceeds 80 m thermal undercutting is important for calving processes in glacial lakes and subaqueous ice melt rates during the melt and freeze seasons are therefore estimated under simple geomorphologic conditions in particular we focus on the differences between valley wind driven water currents in various fetches during the melt season our results demonstrate that the subaqueous ice melt rate exceeds the ice cliff melt rate when the fetch is 20 m and water temperature is 2 48c calculations suggest the onset of calving due to thermal undercutting is controlled by water currents driven by winds at the surface of the lake which develop with expanding water surface

on the influence of debris cover on glacier morphology how high relief structures evolve from smooth surfaces abstract debris covered glaciers receive increasing attention during the current period of sustained negative mass balance and expanding debris cover the debris cover induces various feedback mechanisms that shape the evolution of the glacier geometry and also the glacier surface although the surface morphology of many debris covered glaciers is markedly different from that of debris free glaciers only a few studies have combined different processes to investigate these characteristic glacier surfaces in order to improve our knowledge of glacier evolution on a wider spatial and temporal scale debris covered glacier tongues can consist of parts with a smooth surface as well as surfaces of high local relief with abundant ice cliffs in the lower end in this study we analysed the evolution of the surface features of zmuttgletscher a debris covered glacier in switzerland over a period of 140 years using time series of historic maps high resolution digital elevation models and glacier velocities as well as data on debris cover extent and thickness our results reveal insights into the up glacier expansion of the debris cover over time and the formation of medial moraines in the prolongation of the uppermost areas where debris emerged on the glacier surface moraine ridge prominence increased during periods of negative mass balance and troughs developed in debris free areas between ridges persisting even after a continuous debris cover had developed the changing surface morphology inhibits across glacier meltwater flow both supra and subglacially accordingly we found that large cryo valleys with ice cliffs have formed down glacier of the troughs where meltwater runoff accumulates the meanders of these valleys have enlarged over time especially by ice cliff backwasting at steep slopes and most of the glacier width today is affected by such high relief erosion features we find that about 75 of all ice cliffs are located in this high relief zone the volume lost at these erosion features has increased by a factor of five since the 1980s but is still very small in comparison to the high glacier wide thinning rates

calving laws sliding laws and the stability of tidewater glaciers a new calving criterion is introduced which predicts calving where the depth of surface crevasses equals ice height above sea level crevasse depth is calculated from strain rates and terminus position and calving rate are therefore functions of ice velocity strain rate ice thickness and water depth we couple the calving criterion with three sliding laws in which velocity is controlled by 1 basal drag 2 lateral drag and 3 a combination of the two in model 1 velocities and strain rates are dependent on effective pressure and hence ice thickness relative to water depth imposed thinning can lead to acceleration and terminus retreat and ice shelves cannot form in model 2 ice velocity is independent of changes in ice thickness unless accompanied by changes in surface gradient velocities are strongly dependent on channel width and calving margins tend to stabilize at flow unit widenings model 3 exhibits the combined characteristics of the other two models and suggests that calving glaciers are sensitive to imposed thickness changes if basal drag provides most resistance to flow but stable if most resistance is from lateral drag ice shelves can form if reduction of basal drag occurs over a sufficiently long spatial scale in combination the new calving criterion and the basal lateral drag sliding function model 3 can be used to simulate much of the observed spectrum of behaviour of calving glaciers and present new opportunities to model ice sheet response to climate change

a mathematical model for steady state regolith production at constant erosion rate it has been hypothesized that many soil profiles reach a steady state thickness in this work such profiles were simulated using a one dimensional model of reaction with advective and diffusive solute transport a model rock is considered consisting of albite that weathers to kaolinite in the presence of chemically inert quartz the model yields three different steady state regimes of weathering at the lowest erosion rates a local equilibrium regime is established where albite is completely depleted in the weathering zone this regime is equivalent to the transport limited regime described in the literature with an increase in erosion rate transition and kinetic regimes are established in the transition regime both albite and kaolinite are present in the weathering zone but albite does not persist to the soil air interface in the weathering limited regime here called the kinetic regime albite persists to the soil air interface the steady state thickness of regolith decreases with increasing erosion rate in the local equilibrium and transition regimes but in the kinetic regime this thickness is independent of erosion rate analytical expressions derived from the model are used to show that regolith production rates decrease exponentially with regolith thickness the steady state regolith thickness increases with the darcy velocity of the pore fluid and in the local equilibrium regime may vary markedly with small variations in this velocity and erosion rate in the weathering limited regime the temperature dependences for chemical weathering rates are related to the activation energy for the rate constant for mineral reaction and to the h of dissolution while for local equilibrium regimes they are related to the h only the model illustrates how geochemical and geomorphological observations are related for a simple compositional system the insights provided will be useful in interpreting natural regolith profiles copyright 2010 john wiley sons ltd

refined energy balance modelling of a supraglacial pond langtang khola nepal supraglacial ponds on debris covered glaciers present a mechanism of atmosphere glacier energy transfer that is poorly studied and only conceptually included in mass balance studies of debris covered glaciers this research advances previous efforts to develop a model of mass and energy balance for supraglacial ponds by applying a free convection approach to account for energy exchanges at the subaqueous bare ice surfaces we develop the model using field data from a pond on lirung glacier nepal that was monitored during the 2013 and 2014 monsoon periods sensitivity testing is performed for several key parameters and alternative melt algorithms are compared with the model the pond acts as a significant recipient of energy for the glacier system and actively participates in the glacier s hydrologic system during the monsoon melt rates are 2 4 cm d 1 total of 98 5 m3 over the study period for bare ice in contact with the pond and 1 mm d 1 total of 10 6 m3 for the saturated debris zone the majority of absorbed atmospheric energy leaves the pond system through englacial conduits delivering sufficient energy to melt 2612m3 additional ice over the study period 38 4 m3 d 1 such melting might be expected to lead to subsidence of the glacier surface supraglacial ponds efficiently convey atmospheric energy to the glacier s interior and rapidly promote the downwasting process

stagnation and mass loss on a himalayan debris covered glacier processes patterns and rates the ablation areas of debris covered glaciers typically consist of a complex mosaic of surface features with contrasting processes and rates of mass loss this greatly complicates glacier response to climate change and increases the uncertainty of predictive models in this paper we present a series of high resolution dems and repeat lake bathymetric surveys on ngozumpa glacier nepal to study processes and patterns of mass loss on a himalayan debris covered glacier in unprecedented detail most mass loss occurs by melt below supraglacial debris and melt and calving of ice cliffs backwasting although ice cliffs cover only 5 of the area of the lower tongue they account for 40 of the ablation the surface debris layer is subject to frequent re distribution by slope processes resulting in large spatial and temporal differences in debris layer thickness enhancing or inhibiting local ablation rates and encouraging continuous topographic inversion a moraine dammed lake on the lower glacier tongue spillway lake underwent a period of rapid expansion from 2001 to 2009 but later experienced a reduction of area and volume as a result of lake level lowering and sediment redistribution rapid lake growth will likely resume in the near future and may eventually become up to 7 km long

chalcophile element constraints on magma differentiation of quaternary volcanoes in tengchong sw china abstract the tengchong volcanic field comprises numerous quaternary volcanoes in sw china the volcanic rocks are grouped into units 1 4 from the oldest to youngest units 1 3 and 4 are composed of trachybasalt basaltic trachyandesite and trachyandesite respectively and unit 2 consists of hornblende bearing dacite this rock assemblage resembles those of arc volcanic sequences related to oceanic slab subduction rocks of units 1 and 3 contain olivine phenocrysts with fo contents ranging from 65 to 85 mole indicating early fractionation of olivine and chromite prior to the eruption of magma all the rocks from units 1 3 and 4 have very low pge concentrations with

spatial seasonal and interannual variability of supraglacial ponds in the langtang valley of nepal 1999 2013 supraglacial ponds play a key role in absorbing atmospheric energy and directing it to the ice of debris covered glaciers but the spatial and temporal distribution of these features is not well documented we analyse 172 landsat tm etm scenes for the period 1999 2013 to identify thawed supraglacial ponds for the debris covered tongues of five glaciers in the langtang valley of nepal we apply an advanced atmospheric correction routine landcor 6s and use band ratio and image morphological techniques to identify ponds and validate our results with 2 5 m cartosat 1 observations we then characterize the spatial seasonal and interannual patterns of ponds we find high variability in pond incidence between glaciers may october means of 0 08 1 69 of debris area with ponds most frequent in zones of low surface gradient and velocity the ponds show pronounced seasonality appearing in the pre monsoon as snow melts peaking at the monsoon onset at 2 of debris covered area then declining in the post monsoon as ponds drain or freeze ponds are highly recurrent and persistent with 40 5 of pond locations occurring for multiple years rather than a trend in pond cover over the study period we find high interannual variability for each glacier after controlling for seasonality

heterogeneous water storage and thermal regime of supraglacial ponds on debris covered glaciers the water storage and energy transfer roles of supraglacial ponds are poorly constrained yet they are thought to be important components of debris covered glacier ablation budgets we used an unmanned surface vessel usv to collect sonar depth measurements for 24 ponds to derive the first empirical relationship between their area and volume applicable to the size distribution of ponds commonly encountered on debris covered glaciers additionally we instrumented nine ponds with thermistors and three with pressure transducers characterising their thermal regime and capturing three pond drainage events the deepest and most irregularly shaped ponds were those associated with ice cliffs which were connected to the surface or englacial hydrology network maximum depth 45 6 m whereas hydrologically isolated ponds without ice cliffs were both more circular and shallower maximum depth 9 9 m the englacial drainage of three ponds had the potential to melt 100 20 103 kg to 470 90 103 kg of glacier ice owing to the large volumes of stored water our observations of seasonal pond growth and drainage with their associated calculations of stored thermal energy have implications for glacier ice flow the progressive enlargement and sudden collapse of englacial conduits and the location of glacier ablation hot spots where ponds and ice cliffs interact additionally the evolutionary trajectory of these ponds controls large proglacial lake formation in deglaciating environments

calving speed and climatic sensitivity of new zealand lake calving glaciers calving speeds and calving mechanisms in fresh water contrast with those in tidewater we obtained calving speeds for six lake calving glaciers in new zealand s southern alps and surveyed the depths and temperatures of their ice contact lakes the glaciers are temperate grounded in shallow 20 m water and exhibit compressive flow at their termini these data increase the global dataset of fresh water calving statistics by 40 bringing the total to 21 glaciers for this dataset calving rates uc correlate positively with water depths hw r2 0 83 the relationship being expressed by uc 17 4 2 3 hw this is an order of magnitude lower than values of uc at temperate tidewater glaciers for a subset of 10 glaciers for which ice proximal water temperature tw data are available uc also correlates positively with tw supporting a physical relation between calving and melting at and below the water line fluctuations of new zealand lake calving glaciers in the period 1958 97 show that although the transition from non calving to calving dramatically increases frontal retreat rates the onset of calving does not isolate terminus change from climatic forcing in terms of climatic sensitivity lake calving glaciers occupy an intermediate position between tidewater glaciers least sensitive and non calving glaciers most sensitive

an inventory of historical glacial lake outburst floods in the himalayas based on remote sensing observations and geomorphological analysis abstract glacial lake outburst floods glofs are a unique type of natural hazard in the cryosphere that may result in catastrophic fatalities and damages the himalayas are known as one of the world s most glof vulnerable zones effective hazard assessments and risk management require a thorough inventory of historical glof events across the himalayas which is hitherto absent existing studies imply that numerous historical glof events are contentious because of discrepant geographic coordinates names or outburst time requiring further verifications this study reviews and verifies over 60 historical glof events across the himalayas using a comprehensive method that combines literature documentations archival remote sensing observations geomorphological analysis and field investigations as a result three unreported glof events were discovered from remote sensing images and geomorphological analysis eleven suspicious events were identified and suggested to be excluded the properties of five outburst lakes i e degaco chongbaxia tsho geiqu lemthang tsho and a lake on tshojo glacier were corrected or updated a total of 51 glof events were verified to be convincing and these outburst lakes were classified into three categories according to their statuses in the past decades namely disappeared 12 stable 30 and expanding 9 statistics of the verified glof events show that glof tended to occur between april and october in the himalayas we suggest that more attention should be paid to rapidly expanding glacial lakes with high possibility of repetitive outbursts this study also demonstrates the effectiveness of integrating remote sensing and geomorphic interpretations in identifying and verifying glof events in remote alpine environments this inventory of glofs with a range of critical attributes e g locations time and mechanisms will benefit the continuous monitoring and prediction of potentially dangerous glacial lakes and contribute to outburst induced risk assessments and hazard mitigations

calving processes at a grounded ice cliff repeat photographs and field survey reveal the mechanism of short term ice cliff evolution at maud glacier a temperate lake calving glacier in new zea land calving is cyclic each cycle involving four stages 1 waterline melting and collapse of the roof of a sub horizontal notch at the cliff foot 2 calving of ice flakes from the cliff face leading to a growing overhang from the waterline upwards and crack propagation from the glacier surface 3 large but infrequent calving of slabs in response to the devel oping overhang returning the cliff to an initial vertical profile 4 rare subaqueous cal ving of a submerged ice foot results indicate that the rate controlling process is the speed of waterline melting and that calving rate is independent of water depth at least at time scales of weeks to months slowly calving lake terminating glaciers have mass balances more negative than land terminating glaciers but nevertheless advance and retreat in response to mass balance driven changes in ice velocity