integrated hazard assessment of cirenmaco glacial lake in zhangzangbo valley central himalayas abstract glacial lake outburst floods glofs have recently become one of the primary natural hazards in the himalayas there is therefore an urgent need to assess glof hazards in the region cirenmaco a moraine dammed lake located in the upstream portion of zhangzangbo valley central himalayas has received public attention after its damaging 1981 outburst flood here by combining remote sensing methods bathymetric survey and 2d hydraulic modeling we assessed the hazard posed by cirenmaco in its current status inter annual variation of cirenmaco lake area indicates a rapid lake expansion from 0 10 0 08 km2 in 1988 to 0 39 0 04 km2 in 2013 bathymetric survey shows the maximum water depth of the lake in 2012 was 115 2 m and the lake volume was calculated to be 1 8 107 m3 field geomorphic analysis shows that cirenmaco glacial lake is prone to glofs as mass movements and ice and snow avalanches can impact the lake and the melting of the dead ice in the moraine can lower the dam level hec ras 2d model was then used to simulate moraine dam failure of the cirenmaco and assess glof impacts downstream reconstruction of cirenmaco 1981 glof shows that hec ras can produce reasonable flood extent and water depth thus demonstrate its ability to effectively model complex glofs glof modeling results presented can be used as a basis for the implementation of disaster prevention and mitigation measures as a case study this work shows how we can integrate different methods to glof hazard assessment

hydrological changes in western central asia kyrgyzstan during the holocene as inferred from a palaeolimnological study in lake son kul abstract the hydrology of western central asia is highly sensitive to climatic perturbations in order to understand its long term variability and to infer linkages between precipitation and atmospheric and oceanic systems we conducted a thorough sedimentary and geochemical study on a composite core retrieved in lake son kul central kyrgyzstan a multi proxy approach was conducted on lake sediments based on grain size analyses magnetic susceptibility total organic carbon toc total nitrogen tn and carbon and oxygen isotope analyses on bulk and biogenic materials ostracoda and molluscs shells at a resolution equivalent to ca 40 years aiming to characterise the sequence of palaeolimnological changes in son kul as indicated by 18 o record of bulk carbonates mainly consisting of aragonite the holocene hydrological balance was negative during most of time suggesting an excess of evaporation e over precipitation p limnological conditions fluctuated rapidly before 5000 cal yr bp indicating significant changes in regional hydrology and climate in particular the long term negative hydrological balance was impeded by several short stages with marked increase of precipitation lasting several decades to a few centuries e g 8300 8200 6900 6700 6300 6100 5500 5400 5300 5200 and 3100 3000 cal yr bp precipitation changes as inferred from 18 o data are also documented by increased minerogenic detritus and higher toc we propose that the seasonal pattern of precipitation varied transiently in western central asia during the holocene although evaporation changes may also account for the rapid changes observed in 18 o data when the annual water balance was less critical p e the excess of water might be ascribed to increased precipitation during cold seasons mainly because winter precipitation has more negative 18 o than its summer equivalent conversely when the annual water balance is negative p e the moisture was mainly delivered during the warm season as between 5000 and 2000 cal yr bp our results thus imply that moisture sources could have changed as well during the holocene moisture was delivered as today mainly during summer from the extended caspian aral basin and eastern mediterranean although arctic and even north atlantic seas might be important moisture sources when seasonal precipitation was dominated by winter precipitation we hypothesise that warming arctic and north atlantic seas were important for the north hemisphere circulation during the cold season

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

coupling glacial lake impact dam breach and flood processes a modeling perspective glacial lake outburst floods glofs are highly mobile mixtures of water and sediment that occur suddenly and are capable of traveling tens to hundreds of kilometers with peak discharges and volumes several orders of magnitude larger than those of normal floods they travel along existing river channels in some instances into populated downstream regions and thus pose a risk to people and infrastructure many recent events involve process chains such as mass movements impacting glacial lakes and triggering dam breaches with subsequent outburst floods a concern is that effects of climate change and associated increased instability of high mountain slopes may exacerbate such process chains and associated extreme flows modeling tools can be used to assess the hazard of potential future glofs and process modeling can provide insights into complex processes that are difficult to observe in nature a number of numerical models have been developed and applied to simulate different types of extreme flows but such modeling faces challenges stemming from a lack of process understanding and difficulties in measuring extreme flows for calibration purposes here we review the state of knowledge of key aspects of modeling glofs with a focus on process cascades analysis and simulation of the onset propagation and potential impact of glofs are based on illustrative case studies numerical models are presently available for simulating impact waves in lakes dam failures and flow propagation but have been used only to a limited extent for integrated simulations of process cascades we present a spectrum of case studies from patagonia the european alps central asia and the himalayas in which we simulate single processes and process chains of past and potential future events we conclude that process understanding and process chain modeling need to be strengthened and that research efforts should focus on a more integrative treatment of processes in numerical models

an assessment procedure for glacial hazards in the swiss alps glacial hazards such as ice avalanches glacial lake outburst floods and debris flows have caused severe damage in populated mountain regions such as the swiss alps assessment of such hazards mus

a review of catastrophic drainage of moraine dammed lakes in british columbia abstract moraine dammed lakes are common in the high mountains of british columbia most of these lakes formed when valley and cirque glaciers retreated from advanced positions achieved during the little ice age many moraine dams in british columbia are susceptible to failure because they are steep sided have relatively low width to height ratios comprise loose poorly sorted sediment and may contain ice cores or interstitial ice in addition the lakes commonly are bordered by steep slopes that are prone to snow and ice avalanches and rockfalls moraine dams generally fail by overtopping and incision the triggering event may be a heavy rainstorm or an avalanche or rockfall that generates waves that overtop the dam the dam can also be overtopped by an influx of water caused by sudden drainage of an upstream ice dammed lake jokulhlaup melting of moraine ice cores and piping are other possible failure mechanisms failures of moraine dams in british columbia produce destructive floods orders of magnitude larger than normal streamflows most outburst floods are characterized by an exponential increase in discharge followed by an abrupt drop to background levels when the water supply is exhausted peak discharges are controlled by dam characteristics the volume of water in the reservoir failure mechanisms and downstream topography and sediment availability for the same potential energy at the dam site floods from moraine dammed lakes have higher peak discharges than floods from glacier dammed lakes the floodwaters may mobilize large amounts of sediment as they travel down steep valleys producing highly mobile debris flows such flows have larger discharges and greater destructive impact than the floods from which they form moraine dam failures in british columbia and elsewhere are most frequent following extended periods of cool climate when large lateral and end moraines are built a period of protracted warming is required to trap lakes behind moraines and create conditions that lead to dam failure this sequence of events occurred only a few times during the holocene epoch most notably during the last several centuries glaciers built large moraines during the little ice age mainly during the 1700s and 1800s and lakes formed behind these moraines when climate warmed in the 1900s twentieth century climate warming is also responsible for recent moraine dam failures in mountains throughout the world warming from the late 1800s until about 1940 and again from 1965 to today destabilized moraine dams with interstitial or core ice the warming also forced glaciers to retreat prompting ice avalanches landslides and jokulhlaups that have destroyed some moraine dams

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

comparing a 1d hydraulic model with a 2d hydraulic model for the simulation of extreme glacial outburst floods glacial outburst floods jokulhlaups destroy a significant amount of infrastructure in proglacial areas nevertheless few studies have simulated extreme jokulhlaup inundation using hydraulic modelling in this study we demonstrate the capability of one dimensional jokulhlaup simulation hec ras modelling software and compare simulation results with those from a two dimensional finite element model telemac 2d modelling software to determine the potential and limitations of one dimensional modelling for jokulhlaup simulations in both models a pre defined hydrograph was used as an upstream boundary condition for the jokulhlaup which was simulated on the mo rudalur floodplain northeast iceland an unsteady flow simulation of the rising stage of the flood 5 h 15 min was undertaken with both models to produce maps of flood inundation and flow depth the study shows that simulations had a 200 m horizontal difference in inundated area at the peak discharge stage additional differences were also detected in the rising stage of the hydrograph the most significant differences between the models was found at the time when the front of the jokulhlaup inundated a new area through a sinuous gorge or when inundation took place through a complex flow route maximum difference 1800 m this study demonstrates that one dimensional modelling of jokulhlaup propagation provides results broadly comparable to data derived from more complex simulations copyright 2007 john wiley sons ltd

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

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

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

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

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

satellite and pollen based quantitative woody cover reconstructions for northern asia verification and application to late quaternary pollen data abstract accurate reconstruction of late quaternary vegetation cover is necessary for better understanding of past vegetation dynamics the role of vegetation feedbacks in glacial interglacial climate variations and for validating vegetation and climate models in this paper over 1700 surface pollen spectra from the former soviet union mongolia northern china and northern japan together with data from the advanced very high resolution radiometer avhrr were used to calibrate modern analogue method for quantitatively reconstructing past woody cover from fossil pollen data the avhrr based estimates of woody cover percentages within a 21 21 km window around pollen sampling sites were attributed to the respective modern pollen spectra reconstructions of modern woody cover using the pollen data and best modern analogues bma method matched well to the original avhrr based estimates for both total woody cover r 2 0 77 and its fractions including broad leaved r 2 0 66 needle leaved r 2 0 79 deciduous r 2 0 60 and evergreen r 2 0 76 woody cover discrepancies in the pollen avhrr cross validation may be caused by long distance transport of arboreal pollen patchy forest distributions underrepresentation of larix and populus in pollen records and errors in the avhrr classification the generally strong correlations encourage application of the modern analogue approach for reconstructing late quaternary variations in vegetation cover from northern asian fossil pollen records at the last glacial maximum lgm 21 000 cal yr bp areas presently occupied by boreal forest were much more open suggesting a reduction in total woody cover to below 20 at most modern forest sites pollen records from northern and central siberia suggest a rather quick spread of tree and shrub vegetation after 15 000 cal yr bp presumably in response to increased summer insolation woody cover histories are spatially variable in the modern forest steppe where tree growth is largely controlled by the ratio of annual actual over potential evapotranspiration which serves as an index of moisture availability in northwestern mongolia woody cover percentages decreased between 9000 and 5000 cal yr bp and again between 2000 and 1000 cal yr bp and may be linked to shifts in intensity of the pacific monsoon in contrast pollen data from the kazakhstan forest steppe where atmospheric precipitation is associated with the atlantic westerly flow suggest that woody cover density reached modern levels only during the last millennium

holocene moisture changes in western china central asia inferred from stalagmites abstract central asia lies at the convergence between the mediterranean and asian monsoon climates and there is a complex interaction between the westerlies with the monsoon to form the climate of that region and its variability the region is highly vulnerable to changes in rainfall highlighting the need to understand the underlying controls we present a stalagmite based 18 o record from kesang cave in western china using mc icp ms u series dating and stable isotope analysis stalagmite calcite 18 o largely documents changes in the 18 o of precipitation 18 o in stalagmites was low during the early and middle holocene 10 0 3 0 ka bp and shifted to higher values between 3 0 and 2 0 ka bp after 2 0 ka bp 18 o fluctuates with distinct centennial scale variations drawing from results of state of the art atmospheric general circulation model simulations for the preindustrial period and 9 ka bp we propose that changes in moisture source regions and the wetter climate both contributed to the isotopic depletion of precipitation during the early and middle holocene multiple records from surrounding regions indicate a generally wetter climate during the early and mid holocene supporting our interpretation on the speleothem 18 o changes in precipitation seasonality do not appear to be a viable explanation for the observed changes nor increased penetration of monsoonal moisture to the study site we speculate that the climatic regime shifted around 3 0 2 0 ka bp towards a drier climate resulting in temperature having dominant control on precipitation 18 o the demise of three settlements around 500ad at the margin of tarim basin coincided with a period of decreased precipitation and increased temperature that likely affected local water resources underscoring the potential impact of climate on human habitation in this region

a late pleistocene holocene lacustrine record from lake manas zunggar northern xinjiang western china information on the late quaternary palaeoclimate in the zunggar desert northern xinjiang is deduced from the study of three 5 m long cores taken from lake manas analyses including the mineralogical composition of bulk sediments stable isotope contents of carbonates organic matter pollen and diatoms were performed to help reconstruct the environmental evolution of the area the chronology is provided by 9 ams 14c dates done on carbonates or organic matter the record suggests a late pleistocene humid episode radiocarbon dated at 37 000 32 000 yr b p this episode is followed by a period of extreme aridity attributed to the last glacial maximum the early mid holocene record indicates conditions generally wetter than today as previously established for western china however our results show that the holocene period is rather complex after a minor wet warm pulse estimated to be around 12 000 yr b p the most important environmental change is recorded at 10 000 yr b p it led to the establishment of a steppic vegetation cover in the catchment and of a permanent lake which lasted 4000 years fluvial sedimentation took place between about 6000 and 4500 yr b p and it coincided with a decrease in moisture availability for vegetation growth a second lacustrine episode is recorded from about 4500 to 2500 yr b p although the pollen record and a sudden influx in detrital organic matter suggest a short term dry event around 3800 3500 yr b p the last 2500 years show climate unstability and the step wise establishment of hypersaline conditions in lake manas the major post glacial environmental changes appear to be roughly in phase with those observed in tibet

late holocene drought responsible for the collapse of old world civilizations is recorded in an italian cave flowstone a severe drought in parts of low latitude northeastern africa and southwestern asia 4200 yr ago caused major disruption to ancient civilizations stable isotope trace element and organic fluorescence data from a calcite flowstone collected from the well watered alpi apuane karst of central western italy indicate that the climatic event responsible for this drought was also recorded in mid latitude europe although the timing of this event coincides with an episode of increased ice rafted debris to the subpolar north atlantic the regional ocean atmosphere response seems atypical of similar holocene ice rafting events furthermore comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longer term climate anomaly

snow anomaly events from historical documents in eastern china during the past two millennia and implication for low frequency variability of ao nao and pdo 1 models and instrumental data indicate that the spatial and temporal variations of snow cover are significantly related to atmospheric circulation e g the ao nao here we present historical snow anomaly events during the past two millennia that provide a unique temporal window to studying long term ao nao a prominent phenomenon in wintertime direct descriptions such as no snow during the winter and pray god for snow are interpreted as convincing evidence for snow anomalies the variations of positive negative snow abnormal events show clear decadal to century variations during the past two millennia based on the previous instrumental research and comparison with other reconstruction data we suggest the index of abnormal snow ias may be an ao like atmospheric variability the winter during the medieval warm period mwp ad 900 1300 might be strongly influenced by a predominantly positive ao with less snow condition whereas the little ice age lia ad 1300 1900 by negative ao concomitant with heavier snowfalls in east asia our data show that a warm climate period the mwp a cold period the lia can be perturbed by a cold spell a warm spell which are linked with a change in atmospheric circulation low frequency variability of snow records may be intrinsic to the natural climate system although the dynamic mechanisms linking snow anomalies with atmospheric circulation the ao nao the pdo is unclear on the decadal to century time scales pacific ocean may play an important role in regulating atmospheric circulations since the ias is highly correlated with the reconstruction of pdo

analysis and dynamic modeling of a moraine failure and glacier lake outburst flood at ventisquero negro patagonian andes argentina summary although moraine dams are inherently prone to failure because of their often weak structure loose internal composition and lack of an engineered spillway the understanding of dam breaching processes remains largely incomplete and appropriate modeling approaches are scarce this paper analyzes a recent glacier lake outburst caused by the failure of the terminal moraine of ventisquero negro patagonian andes argentina in may 2009 the dam breach trigger breaching and lake emptying processes plus the dynamics of the outburst flood were reconstructed based on field evidence and the application of a dynamic dam break model results indicate that the moraine failure was caused most probably by a rising lake level due to heavy precipitation resulting in high lake outflow which led to dam erosion and finally to dam failure the lake volume of ca 10 106 m3 was released in ca 3 h producing high discharge ca 4100 m3 s 1 debris flows and hyperconcentrated flows as the escaping water entrained large volumes of clastic material the methodology presented in this paper provides valuable insights into complex dam breach and glof processes and closes a critical gap in dynamic dam break modeling aimed at providing the lake outburst hydrograph an accurate determination of outburst hydrographs constitutes one of the most crucial aspects for hazard assessment of unstable lakes and will gain further importance with ongoing glacier retreat and glacier lake formation

the genesis of diogenites and hed parent body petrogenesis abstract samples of clasts and whole rocks from eighteen of the twenty four known diogenites orthopyroxenite breccia meteorites have been studied by combined inaa empa in order to elucidate their petrogenetic history the incompatible elements a12o3 and tio2 are positively correlated in diogenite orthopyroxenes these elements determined by empa are also positively correlated with incompatible trace elements such as yb determined by inaa on bulk samples these correlations indicate that most diogenites may form a single igneous fractionation sequence the incompatible minor and trace elements are decoupled from the major elements for essentially constant mg tio2 varies by about 4 times and yb by about 8 times hence there is no strong evidence for igneous fractionation preserved in the major element composition of orthopyroxenes geothermometry calculations using two pyroxene and spinelorthopyroxene thermometers show that these phases in diogenites maintained equilibrium to temperatures in the range 650 880 c far below likely magmatic temperatures in some diogenites orthopyroxenes of differing composition are in breccia contact therefore the low equilibration temperatures were achieved in the diogenites prior to brecciation decoupling of major and trace elements was most likely caused by slow subsolidus cooling in the diogenite pluton which allowed ca fe and mg to reach diffusive equilibration incompatible trace elements likely have much lower diffusivities in orthopyroxene and therefore may have largely preserved their magmatic distributions the extensive variation in incompatible trace elements indicates that either the diogenites were formed through an extensive crystallization interval or that partition coefficients greatly increased during crystallization if the former were true one would expect to find substantial amounts of plagioclase in the diogenites if they are comagmatic with eucrites this is contrary to observations a model in which diogenites crystallized from one or more melts of approximately orthopyroxenitic composition can satisfy both the mineralogie and trace element constraints

glaciers glacial lakes and glacial lake outburst floods in the mount everest region nepal recent climate changes have had a significant impact on the high mountain glacial environment rapid melting of glaciers has resulted in the formation and expansion of moraine dammed lakes creating a potential danger from glacial lake outburst floods glofs most lakes have formed during the second half of the 20th century glaciers in the mount everest sagamartha region nepal are retreating at an average rate of 10 59 m a 1 from 1976 to 2000 lumding and imja glaciers retreated 42 and 34 m a 1 respectively a rate that increased to 74 m a 1 for both glaciers from 2000 to 2007 during the past decade himalayan glaciers have generally been shrinking and retreating faster while moraine dammed lakes have been proliferating although the number of lakes above 3500 m a s l has decreased the overall area of moraine dammed lakes is increasing understanding the behaviour of glaciers and glacial lakes is a vital aspect of glof disaster management

association of the northern hemisphere circumglobal teleconnection with the asian summer monsoon during the holocene in a transient simulation this paper provides another look at the response of the asian summer monsoon asm to insolation forcing and oceanic feedback during the holocene using a fully coupled general circulation ocean atmosphere model forced by earth s orbital variations the model results revealed a recurrent circumglobal teleconnection cgt pattern in the summertime june july august mid latitude circulation of the northern hemisphere during the holocene the cgt index showed a decreasing trend before 5 ka bp and a slight increasing trend afterwards affected by the combined effects of summer insolation indian summer monsoon ism north atlantic and indian ocean western pacific ocean sea surface temperature sst the cgt showed a close relationship with asm precipitation and surface air temperature during the holocene and therefore could act as a bridge linking the asm to insolation high latitude forcing north atlantic sst and low latitude forcing tropical ocean sst we emphasize that the mid latitude atmospheri

glacier change in the poiqu river basin inferred from landsat data from 1975 to 2010 abstract the poiqu river basin is a transboundary basin that is highly prone to glacial lake outburst floods this basin is located in the middle of the himalayas between china and nepal fieldwork investigating nearby glaciers has indicated that glaciers in this region have ablated quickly in recent decades a new glacier database for the poiqu river basin was generated for the phases 1975 2000 and 2010 using automatic classification and manual visual interpretation based on long time series landsat data in 2010 the poiqu river basin had 124 glaciers with a total area of 203 4 5 3 km 2 eleven glaciers have debris covered tongues with the debris covering a total area of 51 0 1 5 km 2 during the period of 1975 2000 the area change rates of all glaciers in the basin clean ice and debris covered parts were 0 45 y 0 71 y and 0 96 y respectively from 2000 to 2010 these area change rates were 0 82 y 1 24 y and 0 73 y respectively the number of glaciers and area change of clean ice within various size classes indicate that the large glaciers shrink into small glaciers and smaller glaciers retreated faster the mean size of the glaciers in this basin is within the size class 1 0 5 0 km 2 the area change rate for 1 0 5 0 km 2 glaciers was similar to that of all glaciers in the poiqu river basin the altitude of the region with the fastest change rfc uplifted from 5200 m to 5500 m and the area change rate of glaciers in the rfc accelerated from 0 17 km 2 y to 0 21 km 2 y between the two periods 1975 to 2000 and 2000 to 2010 aspect analysis indicates that for a long time period glaciers with southward aspects including south east southeast and southwest in the poiqu river basin retreated faster than glaciers with northward aspects including west north northeast and northwest at the decade scale changes in areas of glaciers were more influenced by composition than aspect additionally the retreat rate of the glaciers in the poiqu river is in a state of accelerating ablation since 2000 despite elevation and aspect

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

geomorphic and sedimentological signature of a two phase outburst ood from moraine dammed queen bess lake british columbia canada on 12 august 1997 the lower part of diadem glacier in the southern coast mountains of british columbia fell into queen bess lake and produced a train of large waves the waves overtopped the broad end moraine at the east end of the lake and ooded the valley of the west fork of nostetuko river the displacement waves also incised the out ow channel across the moraine stratigraphic and sedimentologic evidence supports the conclusion that the ood had two phases one related to wave overtopping and a second to breach formation empirical equations were used to calculate the peak discharge of the ood at various points along the west fork of the nostetuko valley and to describe the attenuation of the ood wave the velocity of the ood was also calculated to determine the time it took for the ood to reach the main fork of nostetuko river the highest peak discharges were achieved in the upper reach of the valley during the displacement phase of the ood peak discharge declined rapidly just below the moraine dam with little change thereafter for approximately 7 km empirical formulae and boulder measurements indicate a rise in peak discharge in the lower part of the west fork valley we suggest that ow in the upper part of the valley records the passage of two separate ood peaks and that the rise in discharge in the lower part of the valley is due to amalgamation of the wave and breach peaks hydraulic ponding in con ned reaches of the valley extended the duration of the ood in addition erosion of vegetation and sediment in the channel and valley sides may also have exerted an in uence on the duration and nature of ooding sediments were deposited both upstream and downstream of channel constrictions and on a large fan extending out into the trunk nostetuko river valley this study extends our understanding of the variety and complexity of outburst oods from naturally dammed lakes it also shows that simple empirical and other models for estimating peak discharges of outburst oods are likely to yield erroneous results copyright 2005 john wiley sons ltd

spatial change detection of glacial lakes in the koshi river basin the central himalayas region warming and the resulting ongoing deglaciation have led to the formation of new glacial lakes and expansion of existing glacial lakes for giving an overview of the distribution and expansion of glacial lakes in the koshi river basin krb between the central china and nepal himalayas in the recent 10 years this paper aimed to analyze and assess recent spatial variability of glacial lake changes in the krb central himalayas using two inventory data of glacial lake in 2001 and 2010 in nepal and landsat tm etm data for the 1990s 2000 and 2009 on the chinese section of the krb the datasets show that there are 1 203 glacial lakes with a total area of 118 54 km2 in the krb in 2009 in which 599 lakes are mapped in the nepalese section of the krb with a total of 25 92 km2 and 604 lakes in the chinese section of the krb with a total area of 92 62 km2 from 2000 to 2009 the total number of glacial lakes decreased from 1 668 to 1 203 with a reduction of 45 86 in the krb whereas the total lake areas expanded by 10 60 i e 0 72 km2 a from 111 35 to 118 54 km2 between 2000 2001 and 2009 2010 especially 17 lakes are identified as potentially dangerous glacial lakes pdgls by international centre for integrated mountain development icimod on the nepalese section of the krb in 2009 in the same period 23 pdgls are also identified on the chinese section of the krb and the total area increased by 77 46 i e 0 37 km2 a from 1990 to 2010 and the expansion rate is significantly higher than 39 0 19 km2 a of non pdgls therefore there is a need for promoting the awareness of the hazard potential of glacier lakes to support proper planning of mitigation and adaptation strategies in this context

petrology and geochemistry of the unbrecciated achondrite northwest africa 1240 nwa 1240 an hed parent body impact melt nwa 1240 is an unusual eucrite recently recovered in morocco as a single stone of 98 g it is an unbrecciated greenish brown rock nearly devoid of fusion crust it displays porphyritic texture consisting of skeletal hollow low ca pyroxene phenocrysts set in a variolitic fan spherulitic mesostasis of fine elongate pyroxene and plagioclase crystals minor phases are skeletal chromite iron silica troilite ilmenite and minute amounts of phosphate and fayalite pyroxenes are unequilibrated and show one of the widest ranges of composition so far described for a eucrite from en 76 0 wo 1 9 fs 22 1 to compositions nearly devoid of mg unusual ferrosilite and fe augite symplectites and possibly pyroxferroite plagioclase crystals contain significant amounts of fe and mg which are possibly controlled by the ca mg fe2 si3o8 plagioclase component

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

reconstructing historic glacial lake outburst floods through numerical modelling and geomorphological assessment extreme events in the himalaya westoby m j glasser n f hambrey m j brasington j reynolds j m hassan m a a m 2014 reconstructing historic glacial lake outburst floods through numerical modelling and geomorphological assessment extreme events in the himalaya earth surface processes and landforms 39 12 1675 1692

petrology and geochemistry of the fine grained unbrecciated diogenite northwest africa 4215 we report on the petrology and geochemistry of northwest africa nwa 4215 an unbrecciated diogenite recovered in the sahara this single stone weighing 46 4 g displays a wellpreserved cumulative texture it consists of zoned xenomorphic orthopyroxene grains on the order of 500 m in size along with a few large chromite crystals 5 vol up to 3 mm accessory olivine and scarce diopside grains occur within the groundmass usually around the chromite crystals minor phases are cristobalite troilite and metal unlike other diogenites orthopyroxenes en76 2wo1 1fs22 7 to en68 6wo5 5fs25 9 olivines fo76 to fo71 and chromites mg 14 3 44 0 cr 42 2 86 5 are chemically zoned the minor element behavior in orthopyroxenes and the intricate chemical profiles obtained in chromites indicate that the zonings do not mirror the evolution of the parental melt we suggest that they resulted from reaction of the crystals with intercumulus melt in order to preserve the observed zoning profiles nwa 4215 clearly cooled significantly faster than other diogenites indeed the cooling rate determined from the diffusion of cr in olivine abutting chromite is in the order of 10 50 c a suggesting that nwa 4215 formed within a small shallow intrusion the bulk composition of nwa 4215 has been determined for major and trace elements this meteorite is weathered and its fractures are filled with calcite limonite and gypsum typical of hot desert alteration in particular the feo cao abundances and most of the trace element concentrations sr ba pb and ree among others are high and indicate a significant contribution from the secondary minerals to remove the terrestrial contribution we have leached with hcl a subsample of the meteorite the residue made essentially of orthopyroxene and chromite has similar major and trace element abundances to diogenites as shown by the shape of its ree pattern or by its high al ga ratio the connection of nwa 4215 with diogenites is confirmed by its o isotopic composition 17o 1 431 0 102 18o 3 203 0 205 17o 0 248 0 005

a persistent holocene wetting trend in arid central asia with wettest conditions in the late holocene revealed by multi proxy analyses of loess paleosol sequences in xinjiang china abstract there are significant differences in the interpretation of the moisture precipitation history of arid central asia aca during the holocene as inferred on one hand from speleothem oxygen isotope records and on the other from lake sediments here we present the results of measurements of climatically sensitive magnetic properties and soil color from four well dated loess paleosol sequences from the northern slopes of the tienshan mountains and the yili river valley xinjiang china in the core area of aca our results demonstrate that the characteristic holocene paleosol indicating relatively moist conditions generally formed after 6 ka 1 ka 1000 cal yr bp in the study region and that the accumulation of unweathered loess prevailed during the early holocene indicating a dry climate at that time the magnetic proxies further reveal a trend of generally increasing moisture since the last glacial maximum with the wettest climate occurring during the late holocene this trend of increasing moisture during the holocene is representative of the xinjiang region and possibly of the whole of the core area of aca and is in marked contrast both to the mid holocene moisture maximum observed in the east asian summer monsoon region and to the general decrease in the strength of the indian summer monsoon since the early holocene our findings are supported by the results of a climate simulation which indicate a trend of increasing summer and winter precipitation during the holocene in the core area of aca caused mainly by an increase in the strength of the westerlies effected by an increasing latitudinal insolation gradient and by a negative trend of the arctic oscillation ao or north atlantic oscillation nao

recent expansions of glacial lakes in the bhutan himalayas current conditions and secular changes in ice contact lakes in the bhutan china border region were investigated using satellite imagery more than 50 moraine dammed ice contact or ice proximal lakes were identified of which 14 were evidently growing in debris covered areas of valley glaciers lake growth is characterised by the initial appearance of supraglacial lakes and subsequent upstream expansion by a coalesced lake in small debris free or partially debris covered glaciers lake growth begins from a single lake lake growth has continued over a period ranging from 20 to 70 years with a growth rate of 70 m year in length and 0 04 km2 year in area these values observed at the northern side of the main himalayan range are smaller than those observed at the southern side the initial appearance year estimated from the expansion rate of most of the lakes in the southern and northern sides ranges from the 1950s to the 1970s and before the 1950s respectively

reconstructing the chongbaxia tsho glacial lake outburst flood in the eastern himalaya evolution process and impacts abstract glacial lake outburst floods glof are one of the most destructive natural disasters understanding glof evolution and their impacts plays a fundamental role in glof hazard assessment and risk management reconstructing historical glofs is an important exercise because detailed case studies of such glacial hazards are rare which hinders the capacity of glacial hazard practitioners to learn from these events in this study we reconstruct a historical glof from moraine dammed chongbaxia tsho 89 745 e 28 211 n in the eastern himalaya which is a unique case study because the outburst flood cascaded into two further lakes downstream we employ a combination of i multi source and multi temporal satellite imagery ii field investigation including an unmanned aerial vehicle survey iii numerical dam breach and hydrodynamic modelling and iv qualitative and quantitative cryospheric and meteorological analysis to investigate the evolution of the glof hazard simulate moraine dam failure and glof propagation and explore the role that long and short term climate trends played in providing the conditioning factors for the outburst chongbaxia tsho expanded rapidly between 1987 until 2001 in response to glacier recession most likely caused by a regional warming trend of 0 37 c per decade based on satellite image analysis we refine the outburst date to be 6 august 2001 instead of 6 august 2000 as previously reported and attribute an ice avalanche into the glacial lake originating from the receding parent glacier as the most likely trigger for moraine dam failure through dem differencing and lake level decrease we estimate that a total water volume of 27 1 1 6 106 m3 was released from the lake during the event and using dam breach modelling we estimate that the peak discharge at the breach was 6600 m3 s 1 the glof flowed through downstream chongbamang tsho and chongbayong tsho both of which served to attenuate the glof and reduce downstream losses the latter stored an estimated 96 of the flood volume precipitation totals in the weeks preceding the glof exceeded the historical mean by up to 40 and may have contributed to instability of the parent glacier and generation of an ice avalanche with enough impact energy to cause lake water to overtop the moraine dam and initiate breach development a future glof from chongbaxia tsho cannot be ruled out but more field data including detailed lake bathymetry and information pertaining to the sedimentological and geotechnical characteristics of the moraine dam are required for a more robust parameterization of a predictive glof model and quantification of the hazard posed by a future glof

metamorphic diogenite grosvenor mountains 95555 mineral chemistry of orthopyroxene and spinel and comparisons to the diogenite suite abstract grosvenor mountains gro 95555 is a relatively newly discovered and unique metamorphic diogenite it does not show the usual brecciated appearance of other diogenites or wide compositional variability of orthopyroxene or spinel electron microprobe analysis empa and secondary ion mass spectrometer sims analysis of orthopyroxene and empa of spinel show limited compositional variability compositions for orthopyroxene for fe fe mg atomic al zr y and yb fall in the middle of the compositional ranges of the diogenite suite apparently gro 95555 formed at sufficient depth or location to escape brecciation by meteorite bombardment and in a thermal regime that led to high grade metamorphism resulting in homogeneous mineral compositions the believed introduction howardite eucrite and diogenite hed lithologies are to have originated on asteroid 4 vesta during an extensive melting event at 4 6 ga consolmagno and drake

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

flow hydraulics and geomorphic effects of glacial lake outburst floods in the mount everest region nepal glacial lake outburst floods glofs on 3 september 1977 and 4 august 1985 dramatically modified channels and valleys in the mount everest region of nepal by eroding transporting and depositing large quantities of sediment for tens of kilometres along the flood routes the glof discharges were 7 to 60 times greater than normal floods derived from snowmelt runoff glacier meltwater and monsoonal precipitation referred to as seasonal high flow floods shffs specific stream power values ranged from as low as 1900 w m 2 in wide low gradient valley segments to as high as 51 700 w m 2 in narrow high gradient valley segments bounded by bedrock along the upper 16 km of the glof routes the reach averaged specific stream power of the glofs was 3 2 to 8 0 times greater than the reach averaged specific stream power of the shffs the greatest geomorphic change occurred along the upper 10 to 16 km of the glof routes where the ratio between the glof specific stream power and the shff specific stream power was the greatest there was an abundant supply of sediment and channel valley boundaries consisted primarily of unconsolidated sediment below 11 to 16 km from the source area the geomorphic effects of the glofs were reduced because of the lower specific stream power ratio between the glofs and shffs more resistant bedrock flow boundaries reduced sediment supply and the occurrence of past glofs copyright 2003 john wiley sons ltd

evaluation of aster gdem and srtm and their suitability in hydraulic modelling of a glacial lake outburst flood in southeast tibet the resolution and accuracy of digital elevation models dems can affect the hydraulic simulation results for predicting the effects of glacial lake outburst floods glofs however for the tibetan plateau high quality dem data are often not available leaving researchers with near global freely available dems such as the advanced spaceborne thermal emission and reflection radiometer global digital elevation model aster gdem and the shuttle radar topography mission data srtm for hydraulic modelling this study explores the suitability of these two freely available dems for hydraulic modelling of glofs our study focused on the flood plain of a potentially dangerous glacial lake in southeastern tibet to evaluate the elevation accuracy of aster gdem and srtm and their suitability for hydraulic modelling of glofs the elevation accuracies of aster gdem and srtm were first validated against field global position system gps survey points and then evaluated with reference to the relatively high precision of 1 50 000 scale dem dem5 constructed from aerial photography moreover the dem5 aster gdem and srtm were used as basic topographic data to simulate peak discharge propagation as well as flood inundation extent and depth in the hydrologic engineering center s river analysis system one dimensional hydraulic model results of the three dem predictions were compared to evaluate the suitability of aster gdem and srtm for glof hydraulic modelling comparisons of aster gdem and srtm each with dem5 in the flood plain area show root mean square errors between the former two as 15 4 m and between the latter two as 13 5 m although srtm overestimates and aster gdem underestimates valley floor elevations both dems can be used to extract the elevations of required geometric data i e stream centre lines bank lines and cross sections for flood modelling however small errors still exist in the cross sections that may influence the propagation of peak discharge the flood inundation extent and mean water depths derived from aster gdem predictions are only 2 2 larger and 2 3 m deeper than that of the dem5 predictions whereas the srtm yields a flood zone extent 6 8 larger than the dem5 prediction and a mean water depth 2 4 m shallower than the dem5 prediction the modelling shows that in the absence of high precision dem data aster gdem or srtm dem can be relied on for simulating extreme glofs in southeast tibet copyright 2011 john wiley sons ltd

the influence of the de vries 200 year solar cycle on climate variations results from the central asian mountains and their global link long term climatic changes related to solar forcing were examined using millennium scale palaeoclimatic reconstructions from the central asian mountain region i e summer temperature records for the tien shan mountains and precipitation records for the tibetan plateau the reconstructions were based on juniper tree ring width records i e juniperus turkestanica for the tien shan and sabina przewalskii for the tibetan plateau the data were processed using spectral and wavelet analysis and filtered in the frequency range related to major solar activity periodicities the results obtained for various tree ring chronologies indicate palaeoclimatic oscillations in the range of the de vries similar to 210 year solar cycles through the last millennium the quasi 200 year variations revealed in the palaeoclimatic reconstructions correlate well r 2 0 58 0 94 with solar activity variations delta c 14 variations the quasi 200 year climatic variations have also been detected in climate linked processes in asia europe north and south america australia and the arctic and antarctica the results obtained point to a pronounced influence of solar activity on global climatic processes analysis has shown that climate response to the long term global solar forcing has a regional character an appreciable delay in the climate response to the solar signal can occur up to 150 years in addition the sign of the climate response can differ from the solar signal sign the climate response to long term solar activity variations from 10s to 1000s years manifests itself in different climatic parameters such as temperature precipitation and atmospheric and oceanic circulation the climate response to the de vries cycle has been found to occur not only during the last millennia but also in earlier epochs up to hundreds of millions years ago c 2007 elsevier b v all rights reserved

changes in glacial lakes and glaciers of post 1986 in the poiqu river basin nyalam xizang tibet glacial lakes and glaciers are sensitive indicators of recent climate change in the poiqu river basin of southern tibet 60 100 km nw of mt everest landsat imagery defines post 1986 changes in the size and distribution of both glacial lakes and glaciers total area of glaciers in the 229 km2 drainage area has decreased by 20 the number of glacial lakes with areas in excess of 0 020 km2 has increased by 11 and the total area of glacial lakes has increased by 47 the areas of typical large glacial lakes of the area galongco gangxico and cirenmaco have increased by 104 118 and 156 respectively and these increases are confirmed by field investigations comparing the 1986 data the area of glaciers in the basin headwaters has decreased by 46 18 km2 to a present total area of 183 12 km2 an annual rate of change of 3 30 km2 year trends indicate that the total area of glaciers will continue to decrease and that both the numbers and areas of glacial lakes will continue to increase accompanying these trends will be an increased risk of debris flows formed by entrainment of sediment in glacial outburst floods and in surges from both failure and avalanche and landslide induced overtopping of moraine dams based on both the local and world wide history of catastrophes from flows of these origins disaster mitigation must be planned and appropriate engineering countermeasures put in place as soon as possible

petrology and geochemistry of the elephant moraine a79002 diogenite a genomict breccia containing a magnesian harzburgite component the elephant moraine a79002 eeta79002 diogenite is a fragmental breccia with a subtle lightdark structure it is composed of orthopyroxene with minor olivine chromite and ubiquitous inhomogeneously distributed approximately 5 500 m sized troilite and metal grains these latter are present in the matrix and as inclusions in and as symplectic intergrowths with orthopyroxene and olivine trace amounts of silica and diopside are also present most orthopyroxene compositions typical orthopyroxenes are in the narrow range wo2 1 2 7en74 1 75 6fs22 2 23 8 like those of most diogenites a few magnesian orthopyroxenes are present with compositions of wo1 7 2 5en77 5 80 2 fs18 2 20 3 these are among the most magnesian orthopyroxenes known from diogenites a few ferroan orthopyroxenes have compositions of wo2 1 2 9en71 7 73 7fs24 2 25 5 differences in al2o3 tio2 and cr2o3 between the different orthopyroxene groups are inconsistent with a simple igneous fractionation relationship between them olivine compositions are fo75 0 76 9 the olivines could be in equilibrium with the magnesian orthopyroxenes but not with the typical or ferroan orthopyroxenes that form the bulk of eeta79002 metal grains exhibit a range of ni and co contents and ni co ratios their compositions indicate that they are primary igneous metal metal and troilite grains are more prevalent in the dark samples the trace incompatible lithophile element contents of 16 samples are remarkably uniform their yb concentrations are all within their 2s analytical uncertainties of the mean the uniformity and low content of light rare earth elements in eeta79002 indicate that negligible amounts of a trapped liquid component or foreign material mixed in the breccia could be present the siderophile and chalcophile element data show that the light dark structure is due to the distribution of metal and troilite grains dark samples contain higher ni co and se compared to light samples meteorite eeta79002 appears to contain material from three or more related plutons a magnesian harzburgite and two orthopyroxenites and is a genomict breccia

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

the holocene paleolimnology of lake issyk kul kyrgyzstan trace element and stable isotope composition of ostracodes the stable isotope and trace element geochemistry of ostracode shells from lake issyk kul kyrgyzstan provide an important new paleoclimate record for central asia the n 18 o n 13 c sr ca mg ca and u ca composition of shells from the species candona neglecta found in two piston cores constrains the paleohydrology of the lake from 8700 to 1000 calendar yr before present these data combined with robust chronologies based on 16 ams 14 c dates suggest that the region went from a relatively moist climate in the early holocene to a more arid climate in the late holocene intense freshwater input presumably glacial runoff flowed into the lake from 8700 to 8300 cal yr bp as evident from the n 18 o and n 13 c values from 8300 to 6900 cal yr bp n 18 o and sr ca values indicate that the lake was relatively fresh and an open basin and u ca values suggest that the lake was well mixed with well oxygenated bottom waters there is a transition zone between 6900 and 4900 cal yr bp when n 18 o and sr ca values rapidly increase and mg ca and u ca values rapidly decrease during this period the lake evolved from an open freshwater well mixed lake to a closed more saline less well mixed lake for the remainder of the record n 18 o sr ca mg ca and u ca are relatively constant implying conditions similar to modern conditions although the slight increasing trend in sr ca may suggest an increase in salinity over this period the n 13 c values were approximately in equilibrium with atmospheric co2 in the early part of the record but became relatively negative in the later part of the record this indicates that the dominant mechanism controlling the isotopic composition of dissolved inorganic carbon shifted from exchange with the atmosphere to variations in biological productivity fl 2001 elsevier science b v all rights reserved

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

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

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

reconstruction of the largest holocene jokulhlaup within jokulsa a fjollum ne iceland abstract glacial outburst floods jokulhlaups have a significant role for landscape evolution in ne iceland a number of jokulhlaups have routed from the northern margin of vatnajokull during the holocene in this study reconstruction of the largest holocene jokulhlaup along jokulsa a fjollum ne iceland was undertaken using the hec ras hydraulic modelling and hec georas flood mapping techniques with a digital elevation model dem derived from ers insar data and field based wash limit evidence the largest jokulhlaup produced extensive erosional and depositional landforms across an inundated area of 1390 km2 and is calculated to have had a peak discharge of 0 9 106 m3 s 1 power per unit area within this jokulhlaup varied from 6 to 46 000 w m 2 jokulhlaup hydraulics are related to geomorphogical evidence at three key sites in va alda upptyppingar and mo rudalur sub areas in order to explain the abrupt spatial variation of the flood characteristics on a regional scale and to relate erosional and depositional features to spatial variations in jokulhlaup hydraulics these process form relationships of the largest jokulhlaup along the jokulsa a fjollum are compared with large outburst floods elsewhere the largest jokulsa a fjollum jokulhlaup had a factor of 20 times smaller discharge and a factor of 20 times lower power per unit area than altai palaeoflood the largest known flood on the earth

isotopic measurements of precipitation on central asian glaciers southeastern tibet northern himalayas central tien shan the glacial regions of central asia considered in our study are influenced by tropical monsoons and western extratropical cyclones isotopic 18o and d data were obtained over 3 years in three climatic regions gongga massif of southeastern tibet windward slope of summer monsoon xixibangma massif on the northern slope of the himalayas leeward of summer monsoon and the massifs of pobeda khan tengry in the central tien shan exposed to western airstreams the survey reported here provides information from atmospheric precipitation snow pits and a 23 m ice core the significant differences of oxygen isotopic ratios from 25 1 per mil to 9 5 per mil indicate that the indian and pacific oceans as well as the atlantic ocean are sources of moisture on the northern slope of the himalayas and southeastern tibet sharply changing isotopic ratios in precipitation corresponded to changing wind direction and were associated with different sources of air masses on the northern slope of the himalayas and southeastern tibet steady isotopic ratios in atmospheric precipitation and the absence of changing 18o composition in a 23 m ice core suggest only one source of moisture in central tien shan the relatively heavier oxygen isotopic ratios in atmospheric precipitation and ice core indicate the moisture from which the precipitation was derived originated over the caspian or mediterranean seas within the eurasian continent air masses developed over the atlantic ocean advance farther than those from the pacific and indian oceans

solar modulation of north atlantic central water formation at multidecadal timescales during the late holocene article i nfo understanding natural climate variability in the north atlantic region is essential not only to assess the sensitivity of atmosphere ocean climate signal exchange and propagation but also to help distinguish between natural and anthropogenic climate change the north atlantic oscillation is one of the controlling modes in recent variability of atmosphere ocean linkages and ice freshwater fluxes between the polar and north atlantic ocean through these processes the nao influences water mass formation and the strength of the atlantic meridional overturning circulation and thereby variability in ocean heat transport however the impact of the nao as well as other forcing mechanisms on multidecadal timescales such as total solar irradiance on eastern north atlantic central water production central water circulation and climate signal propagation from high to low latitudes in the eastern subpolar and subtropical basins remains uncertain here we use a 1200 yr long benthic foraminiferal mg ca based temperature and oxygen isotope record from a 900 m deep sediment core off northwest africa to show that atmosphere ocean interactions in the eastern subpolar gyre are transferred at central water depth into the eastern boundary of the subtropical gyre further we link the variability of the nao over the past 165 yrs and solar irradiance late holocene and their control on subpolar mode water formation to the multidecadal variability observed at mid depth in the eastern subtropical gyre our results show that eastern north atlantic central waters cooled by up to 0 8 0 7 c and densities decreased by 0 3 0 2 during positive nao years and during minima in solar irradiance during the late holocene the presented records demonstrate the sensitivity of central water formation to enhanced atmospheric forcing and ice freshwater fluxes into the eastern subpolar gyre and the importance of central water circulation for cross gyre climate signal propagation during the late holocene 2011 elsevier b v all rights reserved

a high resolution record of holocene environmental and climatic changes from lake balikun xinjiang china implications for central asia a high resolution record of holocene environmental and climatic change in the balikun area was reconstructed from a sediment core from the lake balikun multiproxy data show that the climate was extremely arid during the early holocene before 8 6 cal ka bp moisture began to increase after 8 6 cal ka bp and the climate was humid between 7 9 and 4 3 cal ka bp a significant dry event occurred around 4 3 3 8 cal ka bp the climate became generally wet during the late holocene after 3 8 cal ka bp the holocene pollen and geophysical records do not indicate a wet early holocene making it evident that there was no early holocene humid period associated with peak asian monsoon strength regional comparisons indicate that this region has a different pattern of holocene environmental and climatic change from the asian monsoonal area and south siberia

paleoenvironmental changes recorded in a luminescence dated loess paleosol sequence from the tianshan mountains arid central asia since the penultimate glaciation abstract mid latitude arid central asia aca is one of the driest regions in the world and is a key source area of global atmospheric dust loess records of paleoclimatic changes in aca are complex and interpretations are problematic due primarily to the lack of robust chronologies quartz osl and k feldspar pirir dating methods were employed to date 8 quartz and 30 k feldspar samples from a 30 m loess sequence byh10 section on the northern slope of the tianshan mountains central aca northwest china the reliability of quartz and k feldspar ages was monitored by internal checks of luminescence characteristics and by comparison of the quartz and k feldspar ages the section lithology proxy indexes of grain size and magnetic susceptibility and the high resolution osl chronology together indicate 1 quartz osl dating can be used to date aca loess samples less than 40 ka while k feldspar pirir dating is reliable for loess samples at least as old as 150 ka from aca 2 aeolian loess began to be deposited on the northern slope of tianshan mountains beginning at least 145 ka ago and was deposited primarily during the penultimate and last glaciation periods 3 rapid loess deposition occurred during mis 6 mis 4 to early mid mis 3 and mis 2 but little or no loess deposition occurred during mis 5 mis 3a and mis 1 4 this loess depositional sequence is comparable to previously published stalagmite growth records in the region on glacial interglacial cycles rapid dust deposition and lack of stalagmite growth during glacials and lack of loess deposition and stalagmite growth during interglacials indicate a climatic pattern of wet warm interglacial and dry cold glacial climatic regimes on orbital cycles in aca 5 variation in the loess deposition rates in aca was much larger than in the central loess plateau during the last glaciation 6 depositional hiatuses of 50 kyr occur in aca loess sequences and high resolution chronologies are needed when reconstructing past climatic changes

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

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

uncertainty of predictions of embankment dam breach parameters risk assessment studies considering the failure of embankment dams often require the prediction of basic geometric and temporal parameters of a breach or the estimation of peak breach outflows many of the relations most commonly used to make these predictions were developed from statistical analyses of data collected from historic dam failures the prediction uncertainties of these methods are widely recognized to be very large but have never been specifically quantified this paper presents an analysis of the uncertainty of many of these breach parameter and peak flow prediction methods application of the methods and the uncertainty analysis are illustrated through a case study of a risk assessment recently performed by the bureau of reclamation for a large embankment dam in north dakota

young ages of two diogenites and their genetic implications the achondrite meteorites known as eucrites and diogenites are thought to be igneous rocks derived from the crust and mantle respectively of a common parent planet or asteroid1 2 several eucrites have been dated at 4 5 4 6 gyr by the rb sr method4 6 and a rb sr age of 4 45 0 18 gyr 1 42x 10 11yr 1 has been reported3 for three diogenites from these data one cannot judge whether diogenites and eucrites are the same age here we present precise rb sr data for two diogenites tatahouine and johnstown that yield an age of 4 394 0 011 gyr significantly younger than our age of 4 52 0 15 gyr for the juvinas eucrite the low initial 87sr 86sr ratio of these diogenites and their rare earth element abundance patterns are inconsistent with the interpretation that the young ages reflect secondary metamorphism we suggest that our data raise doubts about a genetically close relationship between eucrites and these diogenites and that there exist groups of diogenites that are genetically distinct from one another our results also suggest that igneous activity in the assumed parent body continued for about one hundred million years after its formation 4 52 gyr ago the parent body may thus have had a complicated evolutionary history

detecting himalayan glacial lake outburst floods from landsat time series abstract several thousands of moraine dammed and supraglacial lakes spread over the hindu kush himalayan hkh region and some have grown rapidly in past decades due to glacier retreat the sudden emptying of these lakes releases large volumes of water and sediment in destructive glacial lake outburst floods glofs one of the most publicised natural hazards to the rapidly growing himalayan population despite the growing number and size of glacial lakes the frequency of documented glofs is remarkably constant we explore this possible reporting bias and offer a new processing chain for establishing a more complete himalayan glof inventory we make use of the full seasonal archive of landsat images between 1988 and 2016 and track automatically where glofs left shrinking water bodies and tails of sediment at high elevations we trained a random forest classifier to generate fuzzy land cover maps for 2491 images achieving overall accuracies of 91 we developed a likelihood based change point technique to estimate the timing of glofs at the pixel scale our method objectively detected ten out of eleven documented glofs and another ten lakes that gave rise to previously unreported glofs we thus nearly doubled the existing glof record for a study area covering 10 of the hkh region remaining challenges for automatically detecting glofs include image insufficiently accurate co registration misclassifications in the land cover maps and image noise from clouds shadows or ice yet our processing chain is robust and has the potential for being applied on the greater hkh and mountain ranges elsewhere opening the door for objectively expanding the knowledge base on glof activity over the past three decades

aubrites and diogenites trace element clues to their origin we have analyzed by rnaa 25 aubrite and 9 diogenite samples for 13 to 29 siderophile volatile and lithophile trace elements both meteorite classes show a typically igneous siderophile element pattern with ir os re ge more depleted than au ni pd sb but aubrites tend to have about 10 higher abundances 10 3 10 4 cl for the first 4 and 10 2 10 3 cl for the last 4 siderophiles apparently reflecting smaller metal silicate distribution coefficients at lowerf o2 or less complete segregation of metal se is surprisingly abundant in aubrites up to 0 4 cl but te is less so sete 5 cl apparently due to its stronger siderophile character other volatiles ag zn in cd bi t1 show depletions intermediate between lunar dunite and the earth s mantle of 7 aubrites analyzed for ree ce nd eu tb yb lu 6 are depleted in ree 0 08 0 5 cl and 5 show negative eu anomalies the exceptions are bishopville and mt egerton silicate this supports an igneous origin as already noted by boynton and schmitt 1972 no samples of the complementary basaltic and feldspathic rocks have been found thus far but one of our samples of khor temiki dark is a candidate for the basalt it is 5 7 enriched in ree and only slightly less so in rb cs and u though shocked and enriched in siderophiles to 0 05 cl it apparently represents a new meteorite class three diogenites analyzed for ree show very diverse patterns from strongly depleted in light ree for tatahouine ce 0 01 cl to flat for garland 2 5 cl the data confirm the trends found by fukuokaet al 1977 as well as their interpretations factor analysis shows several parallel groupings for aubrites and diogenites siderophiles re ir os pd ge chalcophiles se te volatiles ag in tl and incompatibles u ree and cs or rb but there are some differences for elements such as ni sb cd bi au and zn most of which behave more sensibly in aubrites than in diogenites several element pairs that differ greatly in volatility cs u ge ir correlate closely in aubrites in approximately cl chondrite proportions these correlations and other lines of evidence suggest strongly that aubrites originated by igneous processes in their parent body not by direct nebular condensation the source material may have resembled el chondrites in oxidation state and depletion of refractories metal and volatiles

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

prediction and assessment of multiple glacial lake outburst floods scenario in pho chu river basin bhutan in this study the characteristic of multiple glacial lake outburst floods glofs in the pho chu river basin in bhutanese himalayas is evaluated to help assess the potential impact thorthormi cho tc and lugge cho lc in the east branch and two unnamed lakes labelled a and b in the west branch of pho chu are chosen for the study numerical models were employed to simulate different involved processes the results show that the peak sediment discharge in the east branch of the pho chu river by the tc dam breach reached about 5000 m3 s during the first glof at 4 km whereas by the lc dam breach is about 600 m3 s second glof at 6 km however the highest peak hydrographs sediment and water mixture calculated during the first and second glof are about 10 000 m3 s at the 18 km section and about 23 000 m3 s at the 10 km section respectively in the west branch of pho chu erosion and depositions are the frequent intermittent local processes during the first glof event from lake a because the first event stabilized the irregular river bed profile there is not much sediment discharge developed during the second glof from lake b at the 17 km section of the west branch the peak hydrograph reached about 9000 m3 s during the first event against the peak of about 800 m3 s during the second event the results suggest that even if multiple dam breaches occur simultaneously glof surges pass through the main river channel at different times with very different flood characteristics the differences in travel time and flood characteristics mostly depend on the distributions of bed slope and potential erosion depth along the reach further the amount of sediment accumulated in and transported by each surge is reliant on the temporal geomorphologic setting of the river and therefore on the impact of the previous glof on riverbed profile and potential erosion depth the robustness in peak glof hydrographs is associated with sediment flow dynamics as a consequence serious inundation of punakha lobeysa and major portion of wangdue phodrang is anticipated copyright 2011 john wiley sons ltd

presence of the solar de vries cycle 205 years during the last ice age certain characteristic periodicities in the 14c record from tree rings such as the well known 11 yr schwabe cycle are known to be of solar origin the origin of longer period cycles such as the 205 yr de vries cycle in the 14c record was less certain and it was possible to attribute it either to solar or climatic variability here we demonstrate that the de vries cycle is present in 10be data from the grip ice core during the last ice age 25 to 50 kyr bp analysis of the amplitude of variation of this cycle shows it to be modulated by the geomagnetic field indicating that the de vries cycle is indeed of solar rather than climatic origin

variation in holocene el nino frequencies climate records and cultural consequences in ancient peru analysis of mollusks from archaeological sites on the north and central coasts of peru indicates that between ca 5800 and 3200 2800 cal yr b p el nino events were less frequent than today with modern rapid recurrence intervals achieved only after that time for several millennia prior to 5 8 ka el nino events had been absent or very different from today the phenomena called el nino have had severe consequences for the modern and colonial historically recorded inhabitants of peru and el nino events also influenced prehistoric cultural development the onset of el nino events at 5 8 ka correlates temporally with the beginning of monumental temple construction on the peruvian coast and the increase in el nino frequency after 3 2 2 8 ka correlates with the abandonment of monumental temples in the same region

hydrodynamic characteristics of the tam pokhari glacial lake outburst flood in the mt everest region nepal the tam pokhari glacial lake outburst flood glof which occurred in 1998 in the mt everest region of nepal was evaluated using hydrodynamic models to gain a better understanding of the flow behaviour the flood wave was analysed separately under rigid and erodible boundary conditions in both cases the calculated dam breach hydrograph which had a peak discharge of about 10 000 m3 s was routed through the inkhu river which originates from the lake the morphologic changes along the river were also analysed and the results were compared with satellite images field observations and recorded data in the case of rigid boundaries the routing procedure gradually attenuated the peaks of the hydrographs to account for hydraulic pooling in narrow gorges and storage in the channel in the case of erodible boundaries such effects were minimized due to the increment in channel capacity associated with erosion by debris flow the study revealed that the glof event produced a large scale debris flow additionally the results revealed that erosion and deposition took place intermittently but that approximately 440 000 m3 of sediment was deposited about 14 km downstream from the lake mouth the calculated peak of the water and sediment mixture at 14 4 km was found to be 30 000 m3 s which is almost 6 times as large as that observed when the rigid boundary conditions were used further the increase in the peaks of the hydrographs due to sediment transport was the primary reason for the destruction associated with the glof these findings suggest that the local sedimentology and topography as well as other geo hazard conditions in the area should be carefully evaluated before recommending any control measures against glofs in the himalayan region copyright 2009 john wiley sons ltd

climate change at the 4 2 ka bp termination of the indus valley civilization and holocene south asian monsoon variability 1 planktonic oxygen isotope ratios off the indus delta reveal climate changes with a multi centennial pacing during the last 6 ka with the most prominent change recorded at 4 2 ka bp opposing isotopic trends across the northern arabian sea surface at that time indicate a reduction in indus river discharge and suggest that later cycles also reflect variations in total annual rainfall over south asia the 4 2 ka event is coherent with the termination of urban harappan civilization in the indus valley thus drought may have initiated southeastward habitat tracking within the harappan cultural domain the late holocene drought cycles following the 4 2 ka bp event vary between 200 and 800 years and are coherent with the evolution of cosmogenic 14c production rates this suggests that solar variability is one fundamental cause behind holocene rainfall changes over south asia

dry early holocene revealed by sand dune accumulation chronology in bayanbulak basin xinjiang nw china understanding the holocene climate changes especially moisture variation and their mechanisms in the semiarid arid central asia sca is very important as water availability is crucial for sustainable developments in this area this study presents chronostratigraphy of an aeolian sedimentary sequence from bayanbulak basin xinjiang nw china aiming to infer the holocene moisture history in the sca luminescence dating technique was selected to construct the age framework of the study section since the luminescence signal intensity of quartz from the samples was too low to be detected feldspar was used as an alternative dosimeter a newly developed post infrared ir ir stimulated luminescence irsl pirir dating protocol on k feldspar was applied to determine the ages of samples a set of tests on luminescence characteristics was performed and demonstrate that this method is suitable and the resultant ages are reliable combined with the stratigraphic investigation on the sand dune palaeosol section the results imply a very dry climatic condition characterized by sand dune accumulation at similar to 9 8 kyr and a wet interval of 5 1 6 kyr when a soil layer was formed this moisture variation pattern is consistent with that inferred from many lacustrine records in the sca suggesting a widespread dry period at 11 8 kyr the present results appear to challenge a new stalagmite delta o 18 sequence located nearby to bayanbulak basin which instead suggested a humid early holocene

holocene summer temperature in arid central asia linked to millennial scale north atlantic climate events and driven by centennial scale solar activity abstract the millennial and centennial scale variability of holocene climate in arid central asia aca is poorly understood due to the lack of high resolution records especially of temperature we present a high resolution 45 yr peat cellulose 13c record spanning the last 11 030 years from a well dated peat core atm10 c7 from the altai mountains in aca it is interpreted as a summer temperature record and exhibits millennial and centennial scale variability the millennial scale variability corresponds well to north atlantic ice rafting events implying a climatic link between the north atlantic and the aca via the westerlies the centennial scale cold events were synchronous with stages of low solar activity spectral and cross spectral analyses demonstrate that summer temperature and solar activity have a common cyclicity and we therefore suggest that solar activity was the fundamental driver of the centennial scale variability of summer temperature in aca during the holocene

timing and structure of the 8 2 kyr b p event inferred from δ18o records of stalagmites from china oman and brazil oxygen isotope records of stalagmites from china and oman reveal a weak summer monsoon event with a double plunging structure that started 8 21 0 02 kyr b p an identical but antiphased pattern is also evident in two stalagmite records from eastern brazil indicating that the south american summer monsoon was intensifi ed during the 8 2 kyr b p event these records demonstrate that the event was of global extent and synchronous within dating errors of 50 years in comparison with recent model simulations it is plausible that the 8 2 kyr b p event can be tied in changes of the atlantic meridional overturning circulation triggered by a glacial lake draining event this in turn affected north atlantic climate and latitudinal position of the intertropical convergence zone resulting in the observed low latitude monsoonal precipitation patterns

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

inconsistency between records of δ18o and trace element ratios from stalagmites evidence for increasing mid late holocene moisture in arid central asia the interpretation of trace element calcium ratios of speleothems as indicators of local hydroclimatic variability in the vicinity of caves has led to controversy in reconstructing the evolution of

presidential address presented 2000 august 28 chicago illinois usa the eucrite vesta story many lines of evidence indicate that meteorites are derived from the asteroid belt but in general identifying any meteorite class with a particular asteroid has been problematical one exception is asteroid 4 vesta where a strong case can be made that it is the ultimate source of the howardite eucrite diogenite hed family of basaltic achondrites visible and near infrared reflectance spectra first suggested a connection between vesta and the basaltic achondrites experimental petrology demonstrated that the eucrites the relatively unaltered and unmixed basaltic achondrites were the product of approximately a 10 melt studies of siderophile element partitioning suggested that this melt was the residue of an asteroidal scale magma ocean mass balance considerations point to a parent body that had its surface excavated but remains intact modern telescopic spectroscopy has identified kilometer scale vestoids between vesta and the 3 1 orbit orbit resonance with jupiter dynamical simulations of impact into vesta demonstrate the plausibility of ejecting relatively unshocked material at velocities consistent with these astronomical observations hubble space telescope images show a 460 km diameter impact basin at the south pole of vesta it seems that nature has provided multiple free sample return missions to a unique asteroid major challenges are to establish the geologic context of the hed meteorites on the surface of vesta and to connect the remaining meteorites to specific asteroids

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

peak discharge estimates of glacial lake outburst floods and normal climatic floods in the mount everest region nepal abstract glacial lake outburst floods glofs in the mount everest region of nepal on 3 september 1977 and 4 august 1985 dramatically modified channels and valleys in the region by eroding transporting and depositing large quantities of sediment for tens of kilometers along their flood routes prior to this research the glof discharges had not been determined and the hydrology of normal climatic floods shffs seasonal high flow floods was not known a one dimensional step backwater flow model was utilized in conjunction with paleostage indicators to estimate the peak discharges of the glofs and shffs and to reconstruct the hydrology and hydraulic conditions of the glofs at 10 reaches and shffs at 18 reaches the most reliable glof and shff peak discharge estimates were upstream from constrictions where there was critical depth control the peak discharge of the 1977 glof at 8 6 km from the breached moraine was approximately 1900 m3 s at 7 1 km downstream from the breached moraine the 1985 glof discharge was estimated at 2350 m3 s at 27 km downstream from the breached moraine the 1985 glof attenuated to an estimated discharge of 1375 m3 s the peak discharges of shffs ranged from 7 to 205 m3 s and were positively correlated with increasing drainage area the glof discharges were 7 to 60 times greater than the shff discharges with the greatest ratios occurring near the breached moraines the downstream decline in the ratio between the glof discharge and shff discharge is the result of the downstream attenuation of the glof and the increased discharge of the shff because of increased contributing drainage area and the increased effects of monsoonal precipitation at lower elevations

holocene moisture variations over the arid central asia revealed by a comprehensive sand dune record from the central tian shan nw china abstract arid central asia aca is one of the largest arid desert areas in the world and its climate is dominated by the westerlies in this study we examined sand dune evolution from the bayanbulak basin in the tian shan xinjiang nw china aiming to infer the holocene moisture history of the aca combined with stratigraphic observation and environmental proxies analysis grain size magnetic susceptibility and total organic content large numbers of luminescence ages from multiple sites eight sections 79 samples were applied to reconstruct the evolution of the sand dune accumulation in the study basin the overall results imply very dry conditions characterized by sand dune accumulation at 12 6 5 ka a wet interval between 6 5 and 0 8 ka when soil formation occurred and decreased moisture during the last 0 8 ka this moisture variation pattern is generally consistent with that inferred from many lacustrine records in the core zone of aca suggesting a widespread dry period in the early to middle holocene and relatively wet middle to late holocene thus the moisture history derived from the current sand dune system contrasts with that in asian monsoon areas which are characterized by a strong monsoon high precipitation in the early and mid holocene and a weak monsoon low precipitation and dry climate during the late holocene our results strongly suggest that the winter solar insolation and the external boundary conditions such as atmospheric co2 concentration ice sheets and meltwater fluxes have been major influential factors triggering the holocene moisture evolution in the core zone of aca