elevation changes of ice caps in the canadian arctic archipelago 1 precise repeat airborne laser surveys were conducted over the major ice caps in the canadian arctic archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region our measurements reveal thinning at lower elevations below 1600 m on most of the ice caps and glaciers but either very little change or thickening at higher elevations in the ice cap accumulation zones recent increases in precipitation in the area can account for the slight thickening where it was observed but not for the thinning at lower elevations for the northern ice caps on the queen elizabeth islands thinning was generally 0 5 m yr 1 which is consistent with what would be expected from the warm temperature anomalies in the region for the 5 year period between surveys and appears to be a continuation of a trend that began in the mid 1980s farther south however on the barnes and penny ice caps on baffin island this thinning was much more pronounced at over 1 m yr 1 in the lower elevations here temperature anomalies were very small and the thinning at low elevations far exceeds any associated enhanced ablation the observations on barnes and perhaps penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation as has been previously suggested for barnes ice cap on the basis of the regional relationships between elevation and elevation change in our data the 1995 2000 mass balance for the archipelago is estimated to be 25 km3 yr 1 of ice which corresponds to a sea level increase of 0 064 mm yr 1 this places it among the more significant sources of eustatic sea level rise though not as substantial as the greenland ice sheet alaskan glaciers or the patagonian ice fields

resolving mass flux at high spatial and temporal resolution using grace intersatellite measurements 1 the grace mission is designed to monitor mass flux on the earth s surface at one month and high spatial resolution through the estimation of monthly gravity fields although this approach has been largely successful information at submonthly time scales can be lost or even aliased through the estimation of static monthly parameters through an analysis of the grace data residuals we show that the fundamental temporal and spatial resolution of the grace data is 10 days and 400 km we present an approach similar in concept to altimetric methods that recovers submonthly mass flux at a high spatial resolution using 4 4 blocks at 10 day intervals we estimate the mass of surplus or deficit water over a 52 60 grid centered on the amazon basin for july 2003 we demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal

middle and late quaternary glacial lake outburst floods drainage diversions and reorganization of fluvial systems in northwestern eurasia abstract the middle and late pleistocene glaciations of northern eurasia had a great impact on the evolution of the modern drainage system this paper presents a review and synthesis on the palaeogeography of glacial lakes their drainage and impact on the re organization of the drainage systems during the last two glacial interglacial cycles we will focus on four regions 1 northern central europe and fennoscandia 2 the central part of the east european plain 3 the west siberian plain and 4 the aral caspian black sea area the main findings of the last decade s include the improved chronology of some major river system formation and of meltwater overflows across the continental drainage divides major drainage systems of the north central and west central part of the east european plain upper volga upper dnieper formed due to overspill of glacial lakes in late mis 6 with a partial re organization upper dnieper in mis 2 the aral caspian black sea cascade acted as a sink for glacial meltwater from the north the major meltwater yield to the aral and caspian seas occurred in mis 6 and late mis 5 in mis 2 the meltwater delivery via the volga valley into the caspian sea was low and therefore had only a minor influence on the sea level considerable meltwater discharge to the black sea through the dnieper river system occurred around the maximal stage of the mis 2 glaciation and ceased very quickly after the onset of deglaciation

glacier changes in southeast alaska and northwest british columbia and contribution to sea level rise 1 the digital elevation model dem from the 2000 shuttle radar topography mission srtm was differenced from a composite dem based on air photos dating from 1948 to 1987 to determine glacier volume changes in southeast alaska and adjoining canada srtm accuracy was assessed at 5 m through comparison with airborne laser altimetry and control locations measured with gps glacier surface elevations lowered over 95 of the 14 580 km2 glacier covered area analyzed with some glaciers thinning as much as 640 m a combination of factors have contributed to this wastage including calving retreats of tidewater and lacustrine glaciers and climate change many glaciers in this region are particularly sensitive to climate change as they have large areas at low elevations however several tidewater glaciers that had historically undergone calving retreats are now expanding and appear to be in the advancing stage of the tidewater glacier cycle the net average rate of ice loss is estimated at 16 7 4 4 km3 yr equivalent to a global sea level rise contribution of 0 04 0 01 mm yr

reconstruction of lake balkhash levels and precipitation evaporation changes during the last 2000 years from fossil diatom assemblages environmental changes in arid central asia are prominently manifest through changes in the water balance lake balkhash the largest lake in kazakhstan is a shallow lake situated in a closed basin we obtained a 600 cm long core from the western part of the lake in 2007 and carried out analyses of fossil diatoms and ostracods geochemistry and grain size of the sediments the age control of the core is based on radiocarbon ages of fossil ostracods and in the uppermost part the ad 1963 137cs activity peak and the first appearance of 137cs in ad 1952 we recognized two main diatom assemblages by detrended correspondence analysis one characterized by the dominance of freshwater planktonic species and the other dominated by brackish planktonic brackish and marine benthic and freshwater benthic species the first assemblage suggests higher lake levels and the second suggests lower lake levels the observed assemblage changes are consistent with lake level observations recorded during the last 120 years the diatom assemblage data from the core indicate that there were seven periods when the lake level was low during the last 2000 years moreover the ph of the lake changed together with the lake level in addition during periods when the lake level was low from ad 1260 2000 the abundance of fossil ostracods and the ca and toc contents were low in comparison with the periods before ad 1260 the causes of low water levels were essentially the same between lake balkhash and the aral sea during the studied period one likely cause of the low water levels especially those during the last 1200 years is changes in solar activity furthermore some environmental changes during the past 40 years can be explained by human activities

contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

quantifying tropospheric volcanic emissions with airs the 2002 eruption of mt etna italy 1 the atmospheric infrared sounder airs is a hyperspectral ir spectrometer orbiting on the eos aqua spacecraft since may 2002 in late october 2002 airs detected lower tropospheric sulfur dioxide and ash emitted by an eruption of mt etna italy in plumes which could be tracked over 1000 km from the volcano into north africa we report retrievals of so2 and ash column amounts and ash particle size in the etna plumes airs total so2 compares favorably with contemporaneous ground based correlation spectrometry cospec measurements retrieval of ash cloud parameters in the eruption plumes permits quantitative studies of distal ash fallout the etna data demonstrate the potential of airs to improve measurements of volcanic so2 and ash loading in the troposphere and to refine our understanding of volcanic cloud composition structure and evolution

recent volume and area changes of kaskawulsh glacier yukon canada recent surface elevation changes of kaskawulsh glacier yukon canada are quantified by comparing an air photo derived dem from 1977 and airborne lidar measurements from 1995 2000 and 2007 surface area changes are assessed using historical aerial photography from 1956 and satellite imagery from 1977 to 2007 combined these measurements provide some of the first detailed records of volume change of a large yukon glacier between 1977 and 2007 kaskawulsh glacier underwent a decrease in area of 1 53 and a decrease in volume of 3 27 5 94 km 3 w e the terminus also retreated by 655 m over the period 1956 2007 there was relatively minor volume change over the period 1977 95 0 01 km 3 w e a 1 while over the periods 1995 2000 and 2000 07 volume losses occurred at a relatively constant rate of 0 51 and 0 50 km 3 a 1 w e respectively since 1995 thinning has been prominent throughout the ablation zone while relative stability and even slight thickening has occurred in the accumulation zone these findings are similar to those recently observed at other nearby alaskan glaciers

recent glacier mass changes in the gulf of alaska region from grace mascon solutions the mass changes of the gulf of alaska goa glaciers are computed from the gravity recovery and climate experiment grace inter satellite range rate data for the period april 2003 september 2007 through the application of unique processing techniques and a surface mass concentration mascon parameterization the mass variations in the goa glacier regions have been estimated at high temporal 10 day and spatial 2 2 arc degrees resolution the mascon solutions are directly estimated from a reduction of the grace k band inter satellite range rate data and unlike previous grace solutions for the goa glaciers do not exhibit contamination by leakage from mass change occurring outside the region of interest the mascon solutions reveal considerable temporal and spatial variation within the goa glacier region with the largest negative mass balances observed in the st elias mountains including the yakutat and glacier bay regions the most rapid losses occurred during the 2004 melt season due to record temperatures in alaska during that year the total mass balance of the goa glacier region was 84 5 gt a 1 contributing 0 23 0 01 mm a 1 to global sea level rise from april 2003 through march 2007 highlighting the large seasonal and interannual variability of the goa glaciers the rate determined over the period april 2003 march 2006 is 102 5 gt a 1 which includes the anomalously high temperatures of 2004 and does not include the large 2007 winter balance year snowfall the mascon solutions agree well with regional patterns of glacier mass loss determined from aircraft altimetry and in situ measurements

the palaeolimnology of the aral sea a review abstract formerly the fourth largest inland water body in the world the volume and area of the aral sea have decreased dramatically over the past 30 yr largely as a result of human actions throughout its approximately 2 million year history the fate of this water body has been intimately linked with that of its two main in flowing rivers the amu darya and the syr darya we present a review of the hydrological palaeontological and sedimentological evidence for the evolution of the aral sea based largely on russian literature although the structure of the aral basin can be traced back to the late neogene the sea has only existed in its present form for the past 8 10 ka and the holocene history has been shaped by regional climatic variations the development of the associated drainage system and anthropogenic forces past hydrological changes in the aral basin have led to systematic shifts in the level of the aral sea which are reflected sedimentologically through the deposition of transgressive and regressive sedimentary units and geomorphologically through the development of terraces all the above data are integrated to produced a late quaternary history of this important water body

dynamics of a small surge type glacier using one dimensional geophysical inversion we investigate the dynamics of a small surge type valley glacier as part of a study to characterize glacier response to climate in the donjek range southwest yukon canada pole displacements were measured using kinematic gps techniques during three consecutive summer field seasons measured surface velocities range from 10m a 1 over the lower 1500 m of the 5 km long glacier to a maximum of 25 35 m a 1 over the upper 3500 m basal velocities along an approximate flowline are reconstructed from the measured surface velocities using inverse methods control tests are used to validate the inversion scheme and sensitivity tests are performed to evaluate the influence of the flow law coefficient shape factor and longitudinal averaging length inversion of the real data shows that basal motion accounts for 50 100 of the total surface motion along the flowline based on these results and several other lines of evidence we suggest this glacier may be undergoing a slow surge

holocene lake level fluctuations and environmental changes at taro co southwestern tibet based on ostracod inferred water depth reconstruction lake level change is an important indicator of changes in the hydrological status of lakes triggered by the influence of atmospheric circulation systems previous studies show that the interaction

river inflow and salinity changes in the caspian sea during the last 5500 years abstract pollen spores and dinoflagellate cysts have been analysed on three sediment cores 1 8 1 4 m long taken from the south and middle basins of the caspian sea a chronology available for one of the cores is based on calibrated radiocarbon dates ca 5 5 0 8 cal ka bp the pollen and spores assemblages indicate fluctuations between steppe and desert in addition there are some outstanding zones with a bias introduced by strong river inflow the dinocyst assemblages change between slightly brackish abundance of pyxidinopsis psilata and spiniferites cruciformis and more brackish dominance of impagidinium caspienense conditions during the second part of the holocene important flow modifications of the uzboy river and the volga river as well as salinity changes of the caspian sea causing sea level fluctuations have been reconstructed a major change is suggested at ca 4 cal ka bp with the end of a high level phase in the south basin amongst other hypotheses this could be caused by the end of a late and abundant flow of the uzboy river now defunct carrying to the caspian sea either meltwater from higher latitudes or water from the amu daria a similar later clear phase of water inflow has also been observed from 2 1 to 1 7 cal ka bp in the south basin and probably also in the north of the middle basin

local and distal origin of sands in the hatteras abyssal plain abstract quartz grain shape analysis and sem imagery of pleistocene sediment in the northern and central hatteras abyssal plain indicates two sources for very fine sand in the plain the first source contributed a diagnostic suite of relatively well rounded grains with many silica solution and precipitation features on the surface indicating their derivation from pedologic environments such as the soils of the southeastern u s piedmont and coastal plain the second source was apparently a glacially affected terrain as evidenced by the plethora of irregularly shaped quartz grains with conchoidal fracture features one of the known sources for sediment in the hatteras abyssal plain is the hatteras canyon system elmore et al 1979 which drains part of the continental margin of the southeastern u s not surprisingly an analysis of 29 samples in the black shell turbidite elmore et al 1979 a deposit of known hatteras canyon origin showed that their sands were composed predominantly 73 97 of the well rounded grains of the first source and none of the grains of the second source thus the presence of high proportions of well rounded very fine sand grains was considered to be indicative of sediment transported into the basin via the hatteras canyon system sixteen other sand layers all confined to an area within 150 km of the mouth of the hatteras canyon also contained high proportions of this sand type and hence were attributed to hatteras canyon turbidity currents eastward and southward of this area however very fine sand grains produced in glacially affected areas predominated in all the sand layers sampled except the black shell turbidite it is apparent from this study therefore that the sand supplied to the northern and central hatteras abyssal plain was brought into the basin not only via the hatteras canyon system as has been shown by elmore et al 1979 but from other more northern canyon systems as well likely candidates for these northern transport paths include the wilmington canyon system which was supplied with sediment by the ancestral hudson river in the pleistocene kelling et al 1975 the hudson canyon system horn et al 1971 and possibly canyon systems further north pratt 1968

analysis of a grace global mascon solution for gulf of alaska glaciers we present a high resolution gravity recovery and climate experiment grace mascon solution for gulf of alaska goa glaciers and compare this with in situ glaciological climate and other remote sensing observations our grace solution yields a goa glacier mass balance of 65 11 gt a 1 for the period december 2003 to december 2010 with summer balances driving the interannual variability between october november 2003 and october 2009 we obtain a mass balance of 61 11 gt a 1 from grace which compares well with 65 12 gt a 1 from icesat based on hypsometric extrapolation of glacier elevation changes we find that mean summer june august air temperatures derived from both ground and lower troposphere temperature records were good predictors of grace derived summer mass balances capturing 59 and 72 of the summer balance variability respectively large mass losses during 2009 were likely due to low early melt season surface albedos measured by the moderate resolution imaging spectroradiometer modis and likely associated with the 31 march 2009 eruption of mount redoubt southwestern alaska grace data compared well with in situ measurements at wolverine glacier maritime alaska but poorly with those at gulkana glacier interior alaska we conclude that although goa mass estimates from grace are robust over the entire domain further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations

glacier changes in alaska can mass balance models explain grace mascon trends temperature and precipitation data from three weather stations in the st elias mountains of alaska and northwestern canada were used to drive one dimensional 1 d elevation dependent and 0 d degree day mass balance models model outputs were optimized against a 10 day resolution time series of mass variability during 2003 07 obtained from gravity recovery and climate experiment grace mass concentration mascon solutions the models explained 52 60 of the variance in the grace time series modelled mass variations matched the phase of the grace observations and all optimized model parameters were within the range of values determined from conventional mass balance and meteorological observations we describe a framework for selecting appropriate weather stations and mass balance models to represent glacier variations of large regions there is potential for extending these calibrated mass balance models forwards or backwards in time to construct mass balance time series outside of the grace measurement window

elevation and volume changes on the harding icefield alaska airborne surface elevation profiles of the harding icefield south central alaska were made in 1994 and 1996 thirteen glaciers were profiled along with the upper region of the icefield the profiles were compared to u s geological survey topographic maps made in the 1950s to obtain elevation and volume changes comparison of the changes for the different glaciers shows no significant correlation between volume change and the type of glacier or characteristics such as location aspect size slope or terminus changes estimated total volume change for this 43 year period is about 34 km 3 which corresponds to an area average elevation change of 21 m the estimated error in this elevation change of 5 m is mainly due to errors in the maps at higher elevations our measurements provide an accurate baseline against which future determinations of volume change can be made

using a spatially realistic load model to assess impacts of alaskan glacier ice loss on sea level 1 ice loss from glaciers results in highly nonuniform patterns of sea level change due to the effects of self attraction and loading to quantify these spatial effects it is necessary to obtain an ice load model that is both spatially realistic and regionally complete we demonstrate a technique to produce such a model for the alaskan glaciers by combining mass balance rates from a gravity recovery and climate experiment grace mascon solution with realistic glacier geometries this load model can be used to solve the sea level equation to determine gravitationally self consistent sea level and gravity rates the model predicts a significant drop in relative sea level in the near field of the glaciers with coastal rates of around 9 mm yr compared to a global average rise of 0 2 mm yr and significant differences to those predicted by a coarser model the magnitude and sensitivity of these near field rates imply that the near field tide gauge records could contain significant information about the spatial distribution of ice loss comparison of model gravity rates with an independently produced spherical harmonic grace solution verifies that our technique can successfully capture the mass changes estimated in the mascon solution within our higher resolution model finally we use our ice load model to examine the possibility of detecting the effects of ice loss in estimates of ocean bottom pressure obp from grace we use the model to simulate the effects of grace signal leakage and show that the obp signal from leakage has a similar pattern to but larger amplitude than the sea level fingerprint expected from ice loss

magnetic characteristics of loess paleosol sequences in tacheng northwestern china and their paleoenvironmental implications abstract systematic rock magnetic data including magnetic mineralogy and magnetic concentration magnetic susceptibility laboratory induced magnetic remanences are presented from the loess paleosol sequences in tacheng northwestern china to explore the specific paleoenvironmental significance of magnetic characteristics in the xinjiang loess results show that ferrimagnetic minerals such as magnetite and maghemite dominate the magnetic properties in the tacheng tc section similar to the magnetic mineralogy of loess deposits in the chinese loess plateau clp the magnetic particles in the tc section are characterized by multi domain md and pseudo single domain psd behavior representing the detrital primary mineral phase the absolute contents of pedogenic ultrafine superpara sp ferrimagnetic particles are very low in the tc section indicating that pedogenesis has a limited contribution this is quite different from the magnetic enhancement of loess deposits in the clp variation of magnetic susceptibility and median grain sizes could be interpreted by the predominance of paleowind intensity as well as provenance variation a similar pattern was also found in other places in xinjiang such as talede section in yili basin and bole section in the western tianshan our results suggest that variation of detrital inputs might have played a pivotal role in the enhancement of magnetic susceptibility while pedogenesis was probably responsible for the increase of finer single domain sd particles in paleosol units the arm sirm ratio could serve as an indicator for reflecting the degree of pedogenesis in xinjiang loess

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

ice elevations and surface change on the malaspina glacier alaska 1 here we use ice cloud and land elevation satellite icesat derived elevations and surface characteristics to investigate the malaspina glacier of southern alaska although there is significant elevation variability between icesat tracks on this glacier we were able to discern general patterns in surface elevation change by using a regional digital elevation model dem as a reference surface specifically we report elevation differences between icesat laser 1 3 observations february 2003 november 2004 and a shuttle radar topography mission srtm derived dem from february 2000 elevation decreases of up to 20 25 m over a 3 4 year time period were observed across the folded loop moraine on the southern portion of the malaspina glacier

constraining hydrological and cryospheric mass flux in southeastern alaska using space based gravity measurements 1 watersheds draining into the gulf of alaska goa experience large seasonal and inter annual variations of water in the form of rain snow and ice but accurate constraints on these variations have been difficult to obtain over larger geographic regions water variations can be inferred directly from the gravity recovery and climate experiment grace data however because goa variations occur over such a small region the inferred average value of water flux increases as the applied smoothing of the grace data decreases we use this observed scaling together with scaling results obtained from forward models to infer a seasonal amplitude of 115 20 km3 of water and an average contribution to sea level rise over the two years of data of 0 31 0 09 mm yr these results suggest that accelerated melting that began in the late 1990s as inferred from altimetry continues unabated

volume change of mccall glacier arctic alaska usa 1956 2003 a long history of research documents that mccall glacier arctic alaska usa continues to lose mass at a rate that is likely increasing with time we present a photo comparison 1958 2003 that visually documents these volume changes along with survey measurements that quantify these losses measurements of longitudinal profiles initially acquired from airborne laser altimetry and repeated by ground based surveys indicate that the areally averaged rate of thinning increased between 1956 93 and 1993 2002 from 0 35 0 07 m a 1 to 0 47 0 03 m a 1 respectively total volume loss was 8 3 107 1 7 107 m3 and 2 7 107 0 2 107 m3 all in water equivalent for these two time periods these profiles also indicate that a 1 km stretch of the mid ablation area is behaving differently from this trend with a rate of thinning that is not changing with time lastly we present a comparison of several methods for calculating volume change and assess their relative errors

21st century increase in glacier mass loss in the wrangell mountains alaska usa from airborne laser altimetry and satellite stereo imagery alaskan glaciers are among the largest regional contributors to sea level rise in the latter half of the 20th century earlier studies have documented extensive and accelerated ice wastage in most regions of alaska here we study five decades of mass loss on high elevation land terminating glaciers of the wrangell mountains 4900 km2 in central alaska based on airborne center line laser altimetry data from 2000 and 2007 a digital elevation model dem from aster and spot5 and us geological survey topographic maps from 1957 the regional mass balance estimates derived from center line laser altimetry profiles using two regional extrapolation techniques agree well with that from dem differencing repeat altimetry measurements reveal accelerated mass loss over the wrangell mountains with the regional mass balance rate evolving from 0 07 0 19 m w e a 1 during 1957 2000 to 0 24 0 16 m w e a 1 during 2000 07 nabesna the largest glacier in this region 1056 km2 lost mass four times faster during 2000 07 than during 1957 2000 although accelerated the mass change over this region is slower than in other glacierized regions of alaska particularly those with tidewater glaciers together our laser altimetry and satellite dem analyses demonstrate increased wastage of these glaciers during the last 50 years

reevaluation of the viscoelastic and elastic responses to the past and present day ice changes in southeast alaska abstract we have reevaluated the viscoelastic and elastic responses to the past and present day ice changes in southeast alaska se ak based on a gps data set by combining the data previously published in 2005 with additional uplift rates compiled recently there are 22 new gps sites yielding a total of 91 sites the mean observation epoch of the data sets is the middle of 2003 here we considered three ice unloading effects due to the last glacial maximum lgm the little ice age lia and the present day ice melting pdim we also examined the dependency of the estimated lithospheric thickness and the asthenospheric viscosity on pdim models for this test two pdim models were used one is a model called here the uaf05 ice model whose mean epoch is the mid 1970s and the other is a model called here the uaf07 model whose mean epoch is the mid 1980s statistical examinations of the misfits between observations and model predictions indicate that uaf07 gives much more consistent results than uaf05 based on the magnitude of the minimum 2 and the agreement of the residual distribution with a gaussian function we have tested two different kinds of mantle viscosity structure a 2 layer model similar to the model used the paper previously published in 2005 and a 4 layer model for the 2 layer model at the 95 confidence level the optimum values for the lithospheric thickness and the asthenospheric viscosity with a thickness of 110 km are 54 45 65 km and 5 58 4 0 12 0 in unit of 10 18 pa s respectively on the other hand for the 4 layer model the best values were 60 42 63 km and 10 0 3 0 13 in unit of 10 18 pa s respectively the comparison between the analysis results for gps data and the model computations indicates that the observations detect not only the uplift rates in se ak but also their time variations which are considered to be due to the glacier changes after the 1990s

late quaternary lake level and climate changes in arid central asia inferred from sediments of ebinur lake xinjiang northwestern china arid central asia plays an important role in global climate dynamics but large uncertainties remain in our understanding of the region s hydroclimate variability during the late quaternary here we present a new high resolution record of lacustrine sediment grain size and element chemistry from ebinur lake which was used to infer lake conditions and related climate changes in the study region between ca 39 2 and 3 6 ka end member modeling analysis of grain size data and pca of elemental data show that lake level fluctuated dramatically from 39 2 to 34 0 ka subsequently ebinur lake experienced a high stand from 34 0 to 28 0 ka under humid climate conditions the subsequent period from 28 0 to 12 0 ka was characterized by lake regression under dry climate conditions whereas afterward 12 0 3 6 ka considerably higher lake levels and humid conditions again prevailed millennial scale abrupt climate changes such as heinrich events h3 and h1 and the younger dryas which are documented in the north atlantic region are also detected in the sediment record from ebinur lake comparisons with other sediment records from arid central asia generally support the claim that climate change in this region was influenced mainly by variations in north atlantic sea surface temperatures through the westerlies

iceberg calving as a primary source of regional scale glacier generated seismicity in the st elias mountains alaska 1 since the installation of the alaska regional seismic network in the 1970s data analysts have noted nontectonic seismic events thought to be related to glacier dynamics while loose associations with the glaciers of the st elias mountains have been made no detailed study of the source locations has been undertaken we performed a two step investigation surrounding these events beginning with manual locations that guided an automated detection and event sifting routine results from the manual investigation highlight characteristics of the seismic waveforms including single peaked narrowband spectra emergent onsets lack of distinct phase arrivals and a predominant cluster of locations near the calving termini of several neighboring tidewater glaciers through these locations comparison with previous work analyses of waveform characteristics frequency magnitude statistics and temporal patterns in seismicity we suggest calving as a source for the seismicity statistical properties and time series analysis of the event catalog suggest a scale invariant process that has no single or simple forcing these results support the idea that calving is often a response to short lived or localized stress perturbations our results demonstrate the utility of passive seismic instrumentation to monitor relative changes in the rate and magnitude of iceberg calving at tidewater glaciers that may be volatile or susceptible to ensuing rapid retreat especially when existing seismic infrastructure can be used

alaskan mountain glacial melting observed by satellite gravimetry abstract we use satellite gravity measurements from the gravity recovery and climate experiment grace as an indication of mass change to study potential long term mountain glacial melting in southern alaska and west canada the first 3 5 yr of grace monthly gravity data spanning april 2002 november 2005 show a prominent glacial melting trend in the mountain regions around the gulf of alaska goa grace observed surface mass changes correlate remarkably well with available mass balance data at gulkana and wolverine two benchmark glaciers of the u s geological survey usgs although the grace signals are smaller in magnitude in addition terrestrial water storage tws changes estimated from an advanced land surface model show significant mass loss in this region during the same period after correcting for the leakage errors and removing tws contributions using model estimates we conclude that grace observed glacial melting in the goa mountain region is equivalent to 101 22 km 3 yr which agrees quite well with the assessment of 96 35 km 3 yr based on airborne laser altimetry data and is consistent with an earlier estimate based on the first 2 yr of grace data this study demonstrates the significant potentials of satellite gravity measurements for monitoring mountain glacial melting and regional climate change

mass balance in the glacier bay area of alaska usa and british columbia canada 1995 2011 using airborne laser altimetry the glacier bay region of southeast alaska usa and british columbia canada has undergone major glacier retreat since the little ice age lia we used airborne laser altimetry elevation data acquired between 1995 and 2011 to estimate the mass loss of the glacier bay region over four time periods 1995 2000 2000 05 2005 09 2009 11 for each glacier we extrapolated from center line profiles to the entire glacier to estimate glacier wide mass balance and then averaged these results over the entire region using three difference methods normalized elevation area weighted method and simple average we found that there was large interannual variability of the mass loss since 1995 compared with the long term post lia average for the full period 1995 2011 the average mass loss was 3 93 0 89 gt a 1 0 6 0 1 m w e a 1 compared with 17 8 gt a 1 for the post lia 1770 1948 rate our mass loss rate is consistent with grace gravity signal changes for the 2003 10 period our results also show that there is a lower bias due to center line profiling than was previously found by a digital elevation model difference method

westerlies asia and monsoonal asia spatiotemporal differences in climate change and possible mechanisms on decadal to sub orbital timescales abstract the westerlies dominated climatic regime wdcr in the present interglacial period was proposed because precipitation moisture variations between arid central asia and mid latitude monsoonal asia are out of phase or anti phased on different timescales during the holocene in this study we first review the development of the theoretical framework of the wdcr and then outline the boundary of its core area from the caspian sea in the west to the western hexi corridor in the east with the northern and southern limits coinciding with the domain of arid central asia next we present a synthesis of multiple lines of evidence for the occurrence of the wdcr on multi millennial sub orbital herein to decadal timescales during the holocene finally we examine the possible physical mechanisms responsible for the wdcr we find that external factors insolation changes induced by orbital factors generated the wdcr on a sub orbital timescale whereas a circum global teleconnection silk road pattern was the most significant factor responsible for the wdcr on centennial and decadal timescales the study provides a comprehensive summary of the development of our knowledge of the wdcr over the past several decades together with a tentative theoretical framework for understanding climatic and environmental changes within its region of influence in addition it forms a scientific basis for environmental management and ecological restoration in this arid region in the context of global warming

the mass balance of mccall glacier brooks range alaska u s a its regional relevance and implications for climate change in the arctic mccall glacier has the only long term mass balance record in arctic alaska average annual balances over the periods 1958 72 and 1972 93 were 15 and 33cm respectively recent annual balances 1993 96 are about 60 cm and the mass balance gradient has increased for an arctic glacier with its low mass exchange rate this marks a significant negative trend recently acquired elevation profiles of mccall glacier and ten other glaciers within a 30 km radius were compared with topographic maps made in 1956 or 1973 most of these glaciers had average annual mass balances between 25 and 33 cm while mccall glacier averaged 28 cm for 1956 93 indicating that it is representative of the region in contrast changes in terminus position for the different glaciers vary markedly thus mass balance trends in this region cannot be estimated from fractional length changes at time scales of a few decades we developed a simple degree day accumulation mass balance model for mccall glacier the model was tested using precipitation and radiosonde temperatures from weather stations at inuvik canada and barrow kaktovik and fairbanks alaska and was calibrated with the measured balances the inuvik data reproduce all measured mass balances of mccall glacier well and also reproduce the long term trend towards more negative balances data from the other stations do not produce satisfactory model results we speculate that the arctic front oriented east west in this region causes the differences in model results

rapid thinning of parts of the southern greenland ice sheet aircraft laser altimeter surveys over southern greenland in 1993 and 1998 show three areas of thickening by more than 10 centimeters per year in the southern part of the region and large areas of thinning particularly in the east above 2000 meters elevation the ice sheet is in balance but thinning predominates at lower elevations with rates exceeding 1 meter per year on east coast outlet glaciers these high thinning rates occur at different latitudes and at elevations up to 1500 meters which suggests that they are caused by increased rates of creep thinning rather than by excessive melting taken as a whole the surveyed region is in negative balance

greenland mass balance from grace 1 we use 22 monthly grace gravity recovery and climate experiment gravity fields to estimate the linear trend in greenland ice mass during 2002 2004 we recover a decrease in total ice mass of 82 28 km3 of ice per year consistent with estimates from other techniques our uncertainty estimate is dominated by the effects of grace measurement errors and errors in our post glacial rebound pg correction the main advantages of grace are that it is sensitive to the entire ice sheet and that it provides mass estimates with only minimal use of supporting physical assumptions or ancillary data

measurements of time variable gravity show mass loss in antarctica using measurements of time variable gravity from the gravity recovery and climate experiment satellites we determined mass variations of the antarctic ice sheet during 2002 2005 we found that the mass of the ice sheet decreased significantly at a rate of 152 80 cubic kilometers of ice per year which is equivalent to 0 4 0 2 millimeters of global sea level rise per year most of this mass loss came from the west antarctic ice sheet

short term velocity variations and sliding sensitivity of a slowly surging glacier we use daily surface velocities measured over several weeks in 2007 and 2008 on a slowly surging glacier in yukon canada to examine the ordinary melt season dynamics in the context of the ongoing surge horizontal velocities within and just below the 1 5 km long zone of fastest flow where the surge is occurring are often correlated during intervals of low melt this correlation breaks down during melt events with the lower reaches of the fast flow zone responding first velocity variability in this lower reach is most highly correlated with melt velocities above and below appear to respond at least as strongly to the velocity variations of this reach as to local melt gps height records are suggestive of ice bed separation occurring in the fast flow zone but not below it pointing to a hydrological cause for the short term flow variability in the surging region independent velocity measurements over 6 years show a maximum july flow anomaly coincident with the location most responsive to melt results from a simple model of dashpots and frictional elements lend support to the hypothesis that this zone partly drives the dynamics of the ice above and below it we speculate that the slow surge may enhance glacier sensitivity to melt season processes including short term summer sliding events

hubbard glacier alaska 2002 closure and outburst of russell fjord and postflood conditions at gilbert point 1 hubbard glacier the largest temperate tidewater glacier in the world has been advancing since 1895 ad and has now twice dammed 60 km long russell fjord once in 1986 and more recently in 2002 this paper focuses on the 2002 event when a strong spring advance pushed shallow submarine proglacial sediments against gilbert point closing off russell fjord by late june as a consequence upstream ice flow decelerated from 5 m d 1 to 1 5 m d 1 with flow diverging to either side of gilbert point lake height reached 15 m asl before intense rains caused lake water to overtop the moraine dam on 14 august 2002 three cubic kilometers of water were released within 30 hours with peak discharge reaching 55 000 m3 s 1 24 hours after the flood began the discharge records for the 1986 and 2002 outbursts differ significantly and reflect differences in lake height 26 m versus 15 m and dam types ice versus moraine the 2002 outburst proceeded in two stages 1 relatively slow overtopping of the subaerial moraine with downward erosion rates of 1 2 m h 1 with little lateral expansion 2 followed by faster downward erosion of the submarine moraine up to 7 m h 1 with rapid lateral expansion of the channel by ice calving 7 m h 1 the annual average terminus position at gilbert point has remained constant since 2002 although there are seasonal variations of 100 200 m the deep channel strong tidal currents and seasonally warm ocean water appear to have prevented the advance of this segment of the terminus despite the glacier s continued advance elsewhere along its terminus sediments are slowly filling in the channel at a rate of about 4 m yr 1 and their steady accumulation may eventually trigger the next closure

surface crusts on soils sediments of the southern aral sea basin uzbekistan soils and sediments of the southern aral sea basin of central asia are commonly covered by salt bearing surface crusts these crusts represent a potential source of salt rich dust that can contribute to salinisation of soils in a large area crust types include takyric crusts surface crusts on solonchaks and salt crusts covering dry parts of the lake bed the takyric crusts are structural crusts showing features related to flooding and shrinkage gypsum formed within the sediment matrix is the only evaporite mineral they contain one studied solonchak crust is fine grained with a thin thenardite and bloedite coating along the irregular surface and halite coatings along the sides of pores all salts in this crust formed by evaporation of solutions contained in the groundmass a solonchak crust with a sandy texture contains prismatic gypsum crystals that formed in a water saturated surface layer as well as bloedite eugsterite and halite formed by evaporation of interstitial brines the lake bed crust is a pure accumulation of salt minerals bloedite hexahydrite halite kainite with synsedimentary and diagenetic features salt mineral assemblages in the three crust types are those that form during successive stages of evaporation of aral sea waters in agreement with published theoretical predictions

record negative glacier balances and low velocities during the 2004 heatwave in alaska usa implications for the interpretation of observations by zwally and others in greenland

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

rapid viscoelastic uplift in southeast alaska caused by post little ice age glacial retreat our observations show that extreme uplift in southeast alaska began about 1770 ad with relative sea level rsl change to 5 7 m and current uplift rates to 32 mm yr this region experienced widespread glacial melting following the little ice age lia with the collapse of the glacier bay icefield alone equivalent to 8 mm of global sea level rise geodynamic modelling links the uplift to post lia isostatic rebound with the extreme uplift signal and a priori knowledge of ice load changes requiring the presence of a low viscosity asthenosphere 3 710 18 pa s these crustal deformations are triggered by climate change

uranium series dating uranium decays through a number of radioactive daughter isotopes some of which have half lives comparable to the time scale of prehistoric archaeology the growth of these isotopes in naturally occurring materials at archaeological sites can be used to determine the age of sites the growth of 230th from its parent 234u can be used over a time range from a few hundred to half a million years calcite precipitated from running or dripping water in springs and caves as well as marls and soil deposited calcretes may be spatio temporally associated with archaeological materials they can be dated by 230th 234u and 234u 238u measurements with a precision of 5 10 of the age by alpha counting or 1 by mass spectrometry bones teeth mollusk and egg shells are also datable but present problems due to migration of parent u in and out of the samples during their burial history

from the allerod to the mid holocene palynological evidence from the south basin of the caspian sea pollen and dinoflagellate cysts have been analysed in a core from the south basin of the caspian sea providing a picture of respectively past vegetation and water salinity for the late pleistocene to middle holocene a relatively sharp lithological change at 0 86 m depth reflects a shift from detrital silts to carbonates rich fine silts from this depth upwards a holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates from the vegetation point of view the late pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with pinus juniperus hippophae elaeagnus and even alnus quercus pterocarya and fraxinus related to the allerod palynozone this was interrupted by the younger dryas palynozone when artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of pinus and quercus and the rare presence of ulmus zelkova from 11 5 to 8 4 cal ka bp an open landscape dominated by shrubs such as ephedra and progressively increasing quercus appeared the final spread of diverse evergreen and deciduous trees is delayed and occurs after 8 4 cal ka bp it is suggested that this delay is caused by an arid climate in the early holocene linked to high insolation and perhaps to a lake effect the dinocyst assemblages fluctuate between slightly brackish pyxidinopsis psilata and spiniferites cruciformis 7 psu and lower and more brackish impagidinium caspienense w13 psu in the lateglacial khvalynian highstand the assemblages remained dominated by relative low salinity taxa a late and brief increase of salinity occurred prior to 11 2 cal ka bp associated with the mangyshlak lowstand it is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast uzboy and a likely evaporation increase this lowstand occurs quasi at the same time as the end of a longer lowstand in the black sea the freshest waters are then inferred as having occurred between 8 4 and 4 4 cal ka bp linked to a connection with the amu darya and the melting glaciers on the pamir mountains

airborne surface profiling of glaciers a case study in alaska a relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested the aircraft position is determined by kinematic global positioning system gps methods the distance to the glacier surface is determined with a laser ranger the accuracy is about 0 3 m sufficient to permit future changes to be observed over short time intervals long term changes can be estimated by comparison of profiles with existing maps elevation profiles obtained in 1993 94 from three glaciers in central and south central alaska are compared with maps made about 1950 the resulting area averaged seasonally corrected thickness changes during the interval are gulkana glacier central alaska range 11 m worthington glacier central chugach mountains 7 m and bear lake glacier kenai mountains 12 m all three glaciers retreated during the interval of comparison the estimated uncertainty in the average thickness change is 5 m which is mainly due to errors in the existing maps constraints on the accuracy of the maps are obtained by profiling in proglacial areas

flow dynamics and iceberg calving rates of devon ice cap nunavut canada the surface velocity field of devon ice cap nunavut canada was mapped using interferometric synthetic aperture radar insar ascending european remote sensing satellite 1 and 2 ers 1 2 tandem mode data were used for the western and southeast sectors and 3 day repeat pass ers 1 imagery for the northeast sector speckle tracking procedures were used with radarsat 1 imagery to obtain surface velocities over the terminus of belcher glacier a major calving front where decorrelation between ers data occurred the insar data highlight a significant contrast in ice flow dynamics between the east and west sides of the ice cap ice movement west of the main north south divide is dominated by relatively uniform sheet flow but three fast flowing outlet glaciers that extend 14 23 km beyond the ice cap margin also drain this region several outlet glaciers that extend up to 60km inland from the eastern margin drain the eastern side of the ice cap the dominant ice flow regimes were classified based on the relationship between the driving stress averaged over a length scale often ice thicknesses and the ratio of surface velocity to ice thickness the mapped distribution of flow regimes appears to depict the spatial extent of basal sliding across the ice cap this is supported by a close relationship between the occurrence of flow stripes on the ice surface and flow regimes where basal sliding was found to be an important component of the glacier motion iceberg calving rates were computed using measured surface velocities and ice thicknesses derived from airborne radio echo sounding the volume of ice calved between 1960 and 1999 was estimated to be 20 5 4 7 km 3 or 0 57km 3 a 1 approximately 89 of this loss occurred along the eastern margin the largest single source is belcher glacier which accounts for 50 of the total amount of ice calved

palaeoenvironmental indicators from late holocene and contemporary ostracoda of the aral sea abstract the aral sea is a large terminal lake i e having no outflow in south western asia it is diminishing in size and the salinity of the water is increasing due to excessive withdrawal of water for irrigation from the two main rivers flowing into it the biota of the lake has been decimated and the chemical composition changed dramatically since 1960 three short sediment profiles two cores and one section are examined with a view to reconstructing the most recent history of the sea from microfossil assemblages historical and geological records indicate that since its formation aral sea levels have changed such variation may have been accompanied by changes in the chemistry of the sea through increased evaporation or precipitation in the present work analyses of the mg ca and sr ca molar ratios particularly the latter of benthonic ostracoda from the aforementioned cores indicate that although present salinity levels were never attained during the period of deposition of the sections studied past saalinity variation can be inferred oxygen and carbon isotope analyses of ostracoda and mollusca from one of the sections however indicates two possible periods of relative salinity increase

multi decadal elevation changes on bagley ice valley and malaspina glacier alaska 1 digital elevation models dems of bagley ice valley and malaspina glacier produced by i intermap technologies inc iti from airborne interferometric synthetic aperture radar insar data acquired 4 13 september 2000 ii the german aerospace center drl from spaceborne insar data acquired by the shuttle radar topography mission srtm 11 22 february 2000 and iii the us geological survey usgs from aerial photographs acquired in 1972 73 were differenced to estimate glacier surface elevation changes from 1972 to 2000 spatially non uniform thickening 10 7 m on average is observed on bagley ice valley accumulation area while non uniform thinning 47 5 m on average is observed on the glaciers of the malaspina complex mostly ablation area even larger thinning is observed on the retreating tidewater tyndall glacier these changes have resulted from increased temperature and precipitation associated with climate warming and rapid tidewater retreat

the fluctuating aral sea a multidisciplinary based history of the last two thousand years abstract the aral sea an intracontinental saline lake in western central asia is of great interest because of its rapid shrinkage during the last 50 years which caused catastrophic environmental and socio economic consequences for the region and its population geoscientists established the existence of similar multiple fast and deep lake level fluctuations in the past however a comprehensive picture of these changes has been lacking in this paper we summarize published and new geomorphological sedimentological paleoenvironmental geoarcheological and historical data to reconstruct fluctuations in the aral during the last two thousand years two deep regressions are recognized in addition to the modern human induced regression the regressions occurred at ca 2 1 1 3 and 1 1 0 35 ka cal bp according to the sedimentary and faunal data and 2 1 1 45 and 1 0 0 85 0 45 ka cal bp according to the archeological and historical data the aral sea lake level dropped to ca 10 m a s l during the first regression and to ca 29 m a s l during the second one transgressions which separated these periods reached elevations of ca 52 m a s l and 54 m a s l respectively according to the current data the regressions lasted longer than the transgressions or were of equal duration reasons considered for past aral sea lake level changes include both natural and human related causes as the region features more than 2000 years of agricultural activity

validation of high resolution grace mascon estimates of glacier mass changes in the st elias mountains alaska usa using aircraft laser altimetry we acquired center line surface elevations from glaciers in the st elias mountains of alaska northwestern canada using aircraft laser altimetry during 2000 05 and compared these with repeat measurements acquired in 2007 the resulting elevation changes were used to estimate the mass balance of 32 900 km 2 of glaciers in the st elias mountains during september 2003 to august 2007 yielding a value of 21 2 3 8gta 1 equivalent to an area averaged mass balance of 0 64 0 12 m a 1 water equivalent w e high resolution 2 arc degrees spatial and 10 day temporal gravity recovery and climate experiment grace mass balance estimates during this time period were scaled to glaciers of the st elias mountains yielding a value of 20 6 3 0 gt a 1 or an area averaged mass balance of 0 63 0 09 m a 1 w e the difference in balance estimates altimetry minus grace was 0 6 4 8 gta 1 well within the estimated errors differences likely resulted from uncertainties in subgrid sampling of the grace mass concentration mascon solutions and from errors in assigning an appropriate near surface density in the altimetry estimates the good correspondence between grace and aircraft altimetry data suggests that high resolution grace mascon solutions can be used to accurately assess mass balance trends of mountain glacier regions that are undergoing large changes

rapid thinning of lake calving yakutat glacier and the collapse of the yakutat icefield southeast alaska usa both lake calving yakutat glacier 337 km 2 alaska usa and its parent icefield 810 km 2 are experiencing strong thinning and under current climate conditions will eventually disappear comparison of digital elevation models shows that yakutat glacier thinned at area averaged rates of 4 76 0 06 m w e a 1 2000 07 and 3 66 0 03 m w e a 1 2007 10 simultaneously adjacent yakutat icefield land terminating glaciers thinned at lower but still substantial rates 3 79 and 2 94 m w e a 1 respectively for the same time periods indicating lake calving dynamics helps drive increased mass loss yakutat glacier terminates into harlequin lake and for over a decade sustained a 3 km long floating tongue which started to disintegrate into large tabular icebergs in 2010 such floating tongues are rarely seen on temperate tidewater glaciers we hypothesize that this difference is likely due to the lack of submarine melting in the case of lake calving glaciers floating tongue ice losses were evaluated in terms of overall mass balance and contribution to sea level rise the post little ice age collapse of yakutat icefield was driven in part by tidewater calving retreats of adjacent glaciers the lake calving retreat of yakutat glacier a warming climate and by the positive feedback mechanisms through surface lowering

elevation volume and terminus changes of nine glaciers in north america nine glaciers in alaska and washington u s a originally mapped as part of the international geophysical year igy in 1957 58 were re mapped between 1993 and 1996 eight using airborne surface elevation profiling and the ninth using ground based kinematic global positioning system methods elevation volume and terminus changes were determined for the approximately 38 year period between the igy mapping and the profiling all nine glaciers showed substantial thinning at lower elevations seven of the nine thickened at higher elevations none of the glaciers had a significant net volume increase two had close to zero change and the others had a decrease for the eight glaciers for which we could obtain quantitative information the mean thickness change was 10 m with a large scatter 8 m standard deviation the volume and terminus changes had no clear geographic pattern and no simple relationship between volume change and terminus advance or retreat was identified the largest error in the estimated volume changes is due to map errors

comparison of thermal structure and evolution between neighboring subarctic glaciers 1 the distribution of cold and temperate ice within glaciers and ice sheets affects processes relevant to englacial and basal hydrology sliding and material rheology thermal regimes in turn are shaped by glacier and ice sheet dynamics as well as environmental setting we investigate the thermal structures of two small 7 km2 neighboring glaciers in the st elias mountains of southwestern yukon canada using ice penetrating radar and borehole temperature measurements our data reveal polythermal regimes in both glaciers that are strongly influenced by accumulation zone meltwater entrapment suggesting a climatic control on thermal structure differences in hypsometry and glacier dynamics nevertheless result in observed variations in the distribution of temperate ice between the two sites experiments with a thermomechanically coupled flow band model corroborate the strong control of meltwater entrapment on thermal structure and suggest a generally minimal role for strain heating an exception to this occurs where localized basal sliding produces lateral shearing and thus enhanced heat generation time dependent model simulations suggest that the future thermal evolution of the two glaciers may differ and therefore simple parameterizations of thermal response based on regional climate may not capture realistic variability between individual glaciers despite these differences both glaciers are ultimately expected to become fully cold prior to disappearing under negative mass balance conditions

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

ostracods crustacea through permian triassic events abstract through geological times the main turnover of marine ostracod group occurred at the permian triassic boundary ptb when the palaeozoic world gave way to meso cenozoic world as quite all the groups ostracods intensively suffered of the end palaeozoic events but they have the particularity to pass the ptb and to be present in quite all marine environments we have studied the ostracod assemblages from the best preserved marine permian triassic sections through the world these sections are for most of them located along the palaeo tethys margins south china block and tibet r p china bukk mountains hungary dolomites italy taurus mountains turkey and elbourz mountains iran these areas present different environmental settings from very shallow water to deep shelf the biostratigraphy is well constrained by the presence of conodont index in deep environment from external shelf to slope all the permian ostracods disappear slightly before the ptb and are absent from the early triassic the last representatives of palaeopsychrospheric forms occur in the early anisian on the platforms during the late permian the ostracods are abundant and highly diversified everywhere along peri tethyan margins the typical palaeozoic forms are mixed with the very first meso cenozoic representatives the specific extinction rates in the latest permian vary from 74 to 100 during the earliest triassic two different settings have to be considered with or without microbialitic deposits the development of microbialites gives favorable ecological conditions to ostracods during the griesbachian the fauna is composed of both new comers and surviving palaeozoic forms the reduction of size is frequently observed this interval is called survival stage during the dienerian and the smithian the fauna are very scarce and poor these two substages represent the maximum of poverty for the ostracod fauna may be due to the development of anoxia on the platforms during the spathian occurs the beginning of the true recovery the very last palaeozoic representatives are found in the earliest anisian which is the radiation stage of ostracod fauna with typical new comers the interval of palaeozoic meso cenozoic ostracod turnover is quite long about 15 my

spatial and temporal transferability of a distributed energy balance glacier melt model abstract modeling melt from glaciers is crucial to assessing regional hydrology and eustatic sea level rise the transferability of such models in space and time has been widely assumed but rarely tested to investigate melt model transferability a distributed energy balance melt model debm is applied to two small glaciers of opposing aspects that are 10 km apart in the donjek range of the st elias mountains yukon territory canada an analysis is conducted in four stages to assess the transferability of the debm in space and time 1 locally derived model parameter values and meteorological forcing variables are used to assess model skill 2 model parameter values are transferred between glacier sites and between years of study 3 measured meteorological forcing variables are transferred between glaciers using locally derived parameter values 4 both model parameter values and measured meteorological forcing variables are transferred from one glacier site to the other treating the second glacier

spatial distribution of glacial erosion rates in the st elias range alaska inferred from a realistic model of glacier dynamics glaciers have been principal erosional agents in many orogens throughout much of the recent geological past a modern example is the st elias mountains in southeastern alaska it is a highly convergent complex orogen which has been glaciated for much of its history we examine the seward malaspina glacier system which comprises two of the largest temperate glaciers in the world we focus on the pattern of erosion within its narrow passage through the st elias mountains the seward throat measured glacier surface velocities and elevations provide constraints for a full stress numerical flowband model that enables us to quantitatively determine the glacier thickness profile which is not easily measured on temperate glaciers and the basal characteristics relevant for erosion these characteristics at the bed namely the water pressure normal and shear stresses and sliding velocity are then used to infer the spatial variation in erosion rates using several commonly invoked erosion laws the calculations show that the geometry of the glacier basin exerts a far stronger control on the spatial variation of erosion rates than does the equilibrium line altitude which is often assumed to be important in studies of glaciated orogens the model provides a quantitative basis for understanding why erosion rates are highest around the seward throat which is generally consistent with local and large scale geological observations and thermochronologic evidence moreover model results suggest how glacier characteristics could be used to infer zones of active or recent uplift in ice mantled orogens 2012 american geophysical union all rights reserved

the challenge of monitoring glaciers with extreme altitudinal range mass balance reconstruction for kahiltna glacier alaska glaciers spanning large altitudinal ranges often experience different climatic regimes with elevation creating challenges in acquiring mass balance and climate observations that represent the entire glacier we use mixed methods to reconstruct the 1991 2014 mass balance of the kahiltna glacier in alaska a large 503 km 2 glacier with one of the greatest elevation ranges globally 264 6108 m a s l we calibrate an enhanced temperature index model to glacier wide mass balances from repeat laser altimetry and point observations finding a mean net mass balance rate of 0 74 mw e a 1 0 04 std dev of the best performing model simulations results are validated against mass changes from nasa s gravity recovery and climate experiment grace satellites a novel approach at the individual glacier scale correlation is strong between the detrended model and grace derived mass change time series r 2 0 58 and p 0 001 and between summer r 2 0 69 and p 0 003 and annual r 2 0 63 and p 0 006 balances lending greater confidence to our modeling results we find poor correlation however between modeled glacier wide balances and recent single stake monitoring finally we make recommendations for monitoring glaciers with extreme altitudinal ranges including characterizing precipitation via snow radar profiling

updated estimates of glacier volume changes in the western chugach mountains alaska and a comparison of regional extrapolation methods and 2001 2004 average net balance rates ranged between 3 1 to 0 16 m yr 1 for the tidewater and 1 5 to 0 02 m yr 1 for the nontidewater glaciers we tested several methods for extrapolating these measurements to all the glaciers of the western chugach mountains using a process similar to cross validation predictions of individual glacier changes appear to be difficult probably because of the effects of glacier dynamics which on long multidecadal timescales complicates the response of glaciers to climate in contrast estimates of regional contributions to rising sea level were similar for different methods mainly because the large glaciers whose changes dominated the regional total were among those measured for instance the above sea level net balance rate of columbia glacier 3 1 0 08 km 3 yr 1 water equivalent weq or an equivalent rise in sea level sle of 0 0090 0 0002 mm yr 1 was nearly half of the total regional net balance rate of the western chugach mountain glaciers 7 4 1 1 km 3 yr 1 weq or 0 020 0 003 mm yr 1 sle between 1950 1957 and 2001 2004 columbia glacier is a rapidly retreating tidewater glacier that has lost mass through processes largely independent of climate tidewater glaciers should therefore be treated separately when performing regional extrapolations

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

fast tidewater glaciers some iceberg calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets no temperate tidewater glaciers are known to have floating termini but many polar and subpolar tidewater glaciers do the fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed which may approach zero and the longitudinal back stress on the terminus the terminus boundary condition the calving relation is imperfectly known yet is vital to the dynamics of these glaciers calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested the calving relations for floating termini are virtually unknown this together with the imperfect understanding of basal sliding inhibits confidence in our understanding of the stability of these glaciers columbia glacier alaska is an instructive example because observations have been made on the major changes in its geometry calving rate and dynamics that have occurred in less than 10 years the calving flux has increased more rapidly than the glacier flux causing thinning and retreat as a result the ice velocity has increased markedly the short term velocity changes relate to changes in back pressure ice recession tidal changes and the flux of water injected to the bed these results have relevance to the mechanisms of basal sliding glacier surges and the stability of marine ice streams

patagonia icefield melting observed by gravity recovery and climate experiment grace 1 using recently released reprocessed gravity solutions from the gravity recovery and climate experiment grace we estimate the ice loss rate for the patagonia icefield pif of south america for the period april 2002 through december 2006 after postglacial rebound and hydrological effects are corrected the estimated rate is 27 9 11 km 3 year equivalent to an average loss of 1 6 m year ice thickness change if evenly distributed over the entire pif area the estimated contribution to global sea level rise is 0 078 0 031 mm year this is an independent confirmation of relatively large melting rate estimates from earlier studies employing topographic and cartographic data

accelerated antarctic ice loss from satellite gravity measurements accurate quantification of antarctic ice sheet mass balance and its contribution to global sea level rise remains challenging gravity recovery and climate experiment data spanning the period april 2002 to january 2009 confirm earlier estimates of ice loss for antarctica and indicate that east antarctica started losing mass in about 2006

seasonal and interannual variations of firn densification and ice sheet surface elevation at the greenland summit seasonal and interannual variations in surface elevation at the greenland summit are modeled using a new temperature dependent formulation of firn densification and are compared with elevations from european remote sensing satellite ers 1 2 radar altimetry the rate constant and activation energy usually set as constants in the arrhenius type relation are strongly temperature dependent based on measurements of crystal growth rates a multiplicative factor in the densification rate accounts for differences between densification and grain growth rates and is chosen to match the modeled and measured density profiles from 0 to 40 m the stronger temperature dependence produces a significant seasonal cycle in the densification rate in the upper firn much of the densification and consequent surface lowering occur within 3 months in late spring early summer followed by a build up from accumulation modeled elevation changes using automatic weather station measurements of temperature and accumulation and modeled precipitation agree well with observations the respective seasonal amplitudes are 18 and 25 cm peak to peak with minima in mid summer the minimum elevation in 1995 is driven mainly by a temporary accumulation decrease and secondarily by warmer temperatures increased compaction driven by a summer warming trend decreases the modeled elevation 1992 99 by 20 cm but accumulation increases in latter years dominate the overall 4 2 cm a 1 trend

understanding ice sheet mass balance progress in satellite altimetry and gravimetry satellite remote sensing has come to dominate the measurement of glacier and ice sheet change three independent methods now exist for assessing ice sheet mass balance and we focus on progress in two satellite altimetry icesat and gravimetry grace with improved spatial and temporal sampling and synergy with ice flow measurements both the mechanisms and causes changing mass balance can be investigated we present examples of mass losses due to widespread intensifying glacier dynamic thinning in northwest greenland but local ablation rates in the northeast that are unchanged for decades advances in grace processing reveal greenland net ice sheet mass loss continuing into 2010 at 19530 gt a 1 a similarly negative trend in the gulf of alaska has significant spatial and temporal variation that highlights the importance of intense summer melting here strong summer melt on the antarctic peninsula also precipitated recent ice shelf collapse and prompted rapid dynamic thinning of tributary glaciers at up to 70ma 1 thinning continued for years to decades after collapse and propagated far inland while understanding of the physical mechanisms of change continues to improve estimates of future behaviour and in particular the near future glacial sea level contribution still rely on projections from such observations we introduce the suite of new sensors that will monitor the ice sheets into the future

bioclimatic change of the past 2500 years within the balkhash basin eastern kazakhstan central asia abstract on the bases of analytical data of an 850 cm long sediment core collected from balkhash lake with a chronological control of seventeen ams dates this research reconstructed the lake salinity using carbonate content and the oxygen isotopic composition as proxies and reconstructed the basin wide moisture using a c ratio and pollen concentration as proxies basin wide mean annual temperature mat and mean annual precipitation map were reconstructed using climate pollen response surface method the reconstruction appears to be supportive to the early proposition that the climate in the westerlies dominated areas has been generally characterized by cool wet and warm dry modes balkhash basin has experienced three stages of climate change during the past 2500 years cool wet from 2500 to 1800 cal bp moderate from 1800 to 650 cal bp and cooling and wetting during the past 650 years with the past 100 showing warming and drying the moisture evolution has closely followed the map variation and the mat must have modulated the moisture evolution through controlling the evaporation the first order variation in lake salinity has been controlled by basin wide temperature i e low temperature raises the salinity level in the lake through reducing the ice melt water supply to the lake the second order variation in the lake salinity seems to be modulated by pronounced variations in basin wide moisture those low amplitude variations in basin wide moisture levels left no detectable imprints in lake salinity proxy records

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