manifestations and mechanisms of the karakoram glacier anomaly global scale glacier shrinkage is one of the most prominent signs of ongoing climatic change however important differences in glacier response exist at the regional scale and evidence has accumulated that one particular region stands out the karakoram in the past two decades the region has shown balanced to slightly positive glacier budgets an increase in glacier ice flow speeds stable to partially advancing glacier termini and widespread glacier surge activity this is in stark contrast to the rest of high mountain asia where glacier retreat and slowdown dominate and glacier surging is largely absent termed the karakoram anomaly recent observations show that the anomalous glacier behaviour partially extends to the nearby western kun lun and pamir several complementary explanations have now been presented for the anomaly s deeper causes but our understanding is far from complete whether the anomaly will continue to exist in the coming decades remains unclear but its long term persistence seems unlikely in light of the considerable warming anticipated by current projections of future climate glaciers in the karakoram region with their balanced or slightly positive mass balance stand out from global glacier shrinkage but this anomaly is not expected to persist in the long term according to an overview of the possible explanations

texture development and deformation mechanisms in ringwoodite ringwoodite mg2sio4 with spinel structure is an important phase in the earth s mantle transition zone controlled deformation experiments showed that ringwoodite underwent ductile deformation when compressed axially at 6 10 gpa and at room temperature in a multianvil d dia deformation apparatus texture evolution during cyclic compression has been recorded in situ using x ray transparent anvils with monochromatic synchrotron x ray diffraction and a two dimensional detector quantitative analysis of the images with the rietveld method revealed a 1 1 0 fiber texture by comparing this texture pattern with polycrystal plasticity simulations it is inferred that 111 slip is the dominant deformation mechanism in ringwoodite consistent with high temperature mechanisms observed in other spinel structured materials although strong ringwoodite textures may develop in the transition zone the contribution to bulk anisotropy is minimal due to the weak single crystal anisotropy 2005 elsevier b v all rights reserved

crystallographic preferred orientation of olivine in the earth s deep upper mantle abstract simple shear deformation experiments of olivine were conducted at pressures of 11 1 12 7 gpa and temperatures of 1670 1770 k c type olivine fabric developed by the 1 0 0 0 0 1 slip system and similar fabrics were dominantly developed in a wide range of water content coh 49 19 242 ppm h si in olivine because the seismic fast a axes are perpendicular to the shear plane only for c type fabric a positive negative transition of vsh vsv difference in velocity between horizontally and vertically polarized shear waves inevitably occurs when c type fabric is developed by a pressure induced fabric transition the positive negative transition of vsh vsv at 200 km depth reported in global one dimensional models is known to be well explained by the horizontal flow of olivine with a low water content

upper and mid mantle anisotropy beneath the tonga slab measurements of source side splitting in s waves fromevents within the tonga slab reveal anisotropy in the upperand mid mantle beneath the slab we observed splitting forevents originating at both upper mantle and transition zonedepths anisotropic fast directions are trench parallel orsub parallel for both upper mantle and transition zoneevents delaytimes dt decreasewithdepthforuppermantleevents the source of anisotropy for the upper mantle eventsis likely in the sub slab mantle and is likely indicative oftrench parallel flow due to slab rollback the source ofanisotropy for the deeper earthquakes is more difficult toconstrain but the pattern of splitting measurements arguesfor an uppermost lower mantle anisotropic source and slabinduced deformation may be responsible for this anisotropyas well additional constraints from mineral physics studiesare necessary to interpret the mid mantle anisotropy signalin terms of geodynamical processes

dynamics of surge type glaciers in west kunlun shan northwestern tibet here we examine 31 glaciers in the west kunlun shan of the northwestern tibetan plateau and identify 9 as surge type the method is based on satellite synthetic aperture radar and landsat optical images the former going back to 1992 the latter to 1972 to identify surge type glaciers we consider temporal changes in velocity changes in glacier terminus position propagation of a surge bulge presence of looped and or contoured medial moraines and extensive crevassing other than the nine surge type glaciers we identify two that have likely surged and six that may be surge type but no glacier surges more than once during the observation period meaning that the recurrence interval exceeds 42 years in addition we examine the evolution of the surface velocities at two surging glaciers with the unprecedented temporal resolution of down to 11 days over 7 years the results show clear seasonal modulations by as much as 200 in early winter against those in early summer this seasonal modulation in surface velocity suggests the presence of surface meltwater that reroutes through the englacial and subglacial drainage systems thus our findings suggest that the hydrological processes originating in the surface meltwater play an important role in maintaining the yearlong active surging phase

iron partitioning in a pyrolite mantle and the nature of the 410 km seismic discontinuity pyrolite1 is a hypothetical mixture of distinct minerals which iswidely believed to represent the composition of the earth s mantle the main pressure induced phase transformations of the olivine component of pyrolite occur at about 13 5 gpa to and 24 gpa to mgsio3 rich perovskite magnesiowustite 2 3 which are thought to be responsible for the seismic discontinuities at 410 and 660 km depths in the mantle recent seismological studies however have demonstrated that the 410 km seismic discontinuity is sharper in some areas than that expected from the to transformation in mantle olivine with a fixed composition4 5 6 7 moreover some mineral physics studies suggest that the seismic velocity jump at the 410 km discontinuity is inconsistent with that associated with the to transformation in olivine8 9 here we present a phase equilibria study of a material having pyrolite composition at pressures of 6 16 gpa we found that the iron content in olivine changes significantly with increasing pressure as a result of the formation of a relatively iron rich majorite phase at these pressures this variation in iron content can overcome or at least reduce both of the above difficulties encountered with the pyrolite model of mantle composition by showing that the component mineral systems cannot be treated as separate

remote sensing of glacier change in west greenland accounting for the occurrence of surge type glaciers automated glacier mapping from thresholded band ratios of multispectral satellite data is a well established technique to update glacier inventories over large and remote regions the local glaciers and ice caps on greenland are of particular interest for such efforts as they have been only partly mapped mainly during the 1940s 60s and their potential contribution to global sea level rise could be large here we use three landsat etm scenes from 2001 covering disko island qeqertarsuaq and the nuussuaq and svartenhuk peninsulas west greenland to map the glacier extent in 2001 of 1172 entities we also manually digitize little ice age lia extents from clearly visible trimlines for a subsample of 500 entities in this region with numerous surge type glaciers the related area change calculation is challenging and we consider different samples with and without known surging glaciers for the three regions the mean area changes are 28 20 and 23 respectively when known surge type glaciers are excluded the glaciers on smaller islands and peninsulas closer to the margin of the ice sheet show a lower mean area change of 15 moreover lower 16 and upper 21 bounds are calculated for the overall area changes in the entire region between the lia and 2001 using different upscaling assumptions cumulative length changes since the lia are found to be slightly lower for surge type glaciers

crystallographic preferred orientation of wadsleyite and ringwoodite effects of phase transformation and water on seismic anisotropy in the mantle transition zone simple shear deformation experiments on wadsleyite and ringwoodite aggregates were performed at 15 18 gpa and 1473 1873 k to investigate the effect of water on the development of the crystallographic preferred orientation cpo of wadsleyite and ringwoodite the 001 axes of wadsleyite are preferentially sub parallel to the shear direction and the 010 axes of wadsleyite concentrate in the direction of the shear plane normal for water content less than 9000 ppm h si i e 540 wt ppm in wadsleyite at higher water content in wadsleyite 9000 ppm h si the concentration of the 100 axes of wadsleyite becomes stronger than that of the 010 axes in the direction of the shear plane normal the fabric strength of wadsleyite having low water content 3000 ppm h si was much stronger than that having water content higher than 3000 ppm h si the magnitude of vsh vsv the ratio of horizontally and vertically polarized shear wave velocities in the upper transition zone is well explained by the flow of wadsleyite aggregates having water content higher than 3000 ppm h si the back transformation from ringwoodite to wadsleyite may help to suppress the increase in fabric strength of wadsleyite during the deformation in contrast to wadsleyite the fabric strength of ringwoodite cpos was not sufficient to cause robust seismic anisotropy even though the deformation of ringwoodite was controlled by dislocation creep thus the lower transition zone is expected to be largely isotropic

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

melt water chemistry and its impact on stream water quality samples of snowpack leachate were collected over a 60 day period of the spring melt season in 1988 and 1989 at a 10 km2 upland catchment in the cairngorm mountains of scotland these were analysed for major ions to assess snowpack chemistry dynamics through the spring and to assess the melt water influence on stream water chemistry the data clearly show preferential elution of sulphate and nitrate over chloride and hydrogen over the other cations during the early melt of 1988 following the addition of ions to the snow surface either as snow or later in the season as rain the elution sequence is reproduced comparison of leachate chemistry with stream chemistry samples taken at the basin outlet indicate that snow pack melt water contributes directly to stream water the stream water chemistry signal is however noisy and the stream concentrations are considerably damped relative to the snowpack leachate this is thought to be a consequence of differential melting within the catchment as the snowpack at lower altitudes is at a more advanced stage of melt and so holds fewer solutes and mixing with groundwater contributions temperature observations at different altitudes within the catchment support this interpretation

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

mechanisms of transformation and deformation in mg1 8fe0 2sio4 olivine and wadsleyite under non hydrostatic stress abstract we have studied the effect of non hydrostatic stress on the mechanisms of the olivine wadsleyite ringwoodite phase transformations and deformation mechanisms of olivine and wadsleyite at high pressure experiments were performed at 900 c in the stability field 15 gpa for 0 5 h and in the stability field 16 gpa for 11 h using a multianvil apparatus with san carlos olivine as the starting material a sample assembly designed to produce non hydrostatic stress was used the deformed samples have been characterised using optical and transmission electron microscopy remnant olivine contains high densities of mostly c dislocations and deformation occurs by dislocation glide involving the slip systems 010 001 and 100 001 in wadsleyite dislocations are in a climb configuration which suggests that self diffusion of si and or o is much faster in wadsleyite than in olivine at 900 c wadsleyite also contains 010 stacking faults which are interpreted to be growth defects that anneal out with time during the olivine wadsleyite transformation non hydrostatic stress results in anisotropic reaction textures wadsleyite nucleates preferentially on olivine grain boundaries that are oriented at a high angle to the direction of principal compressive stress and or the growth of wadsleyite occurs preferentially in this direction wadsleyite transforms to ringwoodite by two competing mechanisms i coherent intracrystalline nucleation on a dislocations probably where they intersect 010 stacking faults and ii partially coherent nucleation at wadsleyite grain boundaries non hydrostatic stress enhances transformation rates by increasing the density of dislocations which act as nucleation sites for ringwoodite although the samples were partially reacted under non hydrostatic stress there is no evidence for transformational faulting

glacier shrinkage across high mountain asia an assessment of glacier shrinkage reductionof area for all of high mountain asia requires a complete compilation of measured rates of change and also a methodology for objective comparison of rates i present a compilation from 155 publications reporting glacier area changes and also a method ology that overcomes the main obstacles hindering comparison glacier areas are not always assigned uncertainties and this problem is addressed with an error model derived from published estimates the problem of discordant survey dates is addressed by interpolating measured areas to fixed dates at pentadal intervals interpolation error depends only incoherently on the time span between measure ments but strongly on glacier size smaller glaciers in addition to changing more rapidly on average exhibit more variable rates of change the overlapping boundaries of study regions are reconciled by mapping all of the information to a 0 5 geographical grid when coupled with glacier area information from the randolph glacier inventory the widely observed inverse dependence of shrinkage rates on glacier size shows promise as a tool for treating incomplete spatial coverage over high mountain asia as a whole from 1960 to 2010 the unweighted average shrinkage rate is 0 57 a 1 but corrections for variable glacier size raise the average to 0 34 a 1 and filling unmeasured gridcells with rates based on size dependence alters the latter estimate to 0 40 a 1 the uncertainties in these rates are large the karakoram anomaly is found to be a zonal feature extending well to the east of the karakoram proper

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

an olivine fabric database an overview of upper mantle fabrics and seismic anisotropy we present a unique database of 110 olivine petrofabrics and their calculated seismic properties the samples come from a variety of the upper mantle geodynamic environments ophiolites subduction zones and kimberlites with a wide range of micro structures a phenomenological relationship is established between p and s wave seismic anisotropy and the degree of crystal alignment fabric strength seismic anisotropy increases rapidly at low fabric strength before reaching a near saturation level of 15 to 20 for p waves and 10 to 15 for s waves despite a large variation in the symmetry of fabric patterns the average seismic properties of the different fabric micro structural and geodynamic settings have similar anisotropies in both magnitude and symmetry hence it would seem possible to determine some measure of fabric strength from seismic anisotropy if the dimensions of the anisotropic region are known but not geodynamic environment or details of the petrofabric pattern a simple pattern of seismic anisotropy characterises the average sample of the database which has the following features the polarisation plane of the fastest s wave is parallel or sub parallel to the foliation plane the maximum shear wave splitting is parallel to the y structural direction in foliation plane and normal to the lineation the maximum of the p wave velocity is parallel to the high concentration of 100 axes which is sub parallel to the lineation the 100 orientation distribution has the greatest influence on the p wave seismic anisotropy the 100 and 001 orientation distributions have the greatest influence on the symmetry of s wave anisotropy although the magnitude of anisotropy is influenced by the distribution of all three principal axes although the database only contains olivine petrofabrics this statistical study clearly shows that seismic anisotropy can be used to deduce the orientation of the structural frame in the upper mantle 1998 elsevier science b v all rights reserved

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

interpretation of sks waves using samples from the subcontinental lithosphere abstract the seismic properties of five south african kimberlite nodules have been calculated from petrofabric measurements these garnet lherzolite and harzburgite composition nodules 56 80 olivine are known from previous studies to have originated at depths of 120 170 km in the subcontinental lithosphere their in situ seismic properties have been calculated by extrapolating the elastic constants to the appropriate temperature 900 1050 c and pressure 3 0 3 5 gpa conditions the average of the five samples has a maximum s wave anisotropy v s of 3 7 which is sufficiently high to explain previously reported teleseismic sks delay times t in continental shield areas of up to 1 7 s the biggest delay time is observed when the foliation is vertical the lineation horizontal and the fastest s wave polarized parallel to the lineation i e an orientation for transcurrent motion delay times of over 1 s can only be generated by this orientation a strong mantle crust mechanical coupling is suggested for such situations the potential use of seismic anisotropy as an indicator of strain in the lithosphere has been investigated using experimental and simulated fabric data for olivine the most abundant phase 70 in the upper mantle the v p and v s seismic anisotropy increases with fabric strength and finite strain recrystallization tends to reduce fabric strength and seismic anisotropy resulting in saturation values for experimental and simulated fabrics which correspond to approximately 50 60 strain or 8 9 v s for pure olivine aggregates a survey of 25 naturally deformed peridotites of oceanic origin suggests an average maximum s wave anisotropy for the olivine component of 9 or about 8 for a lherzolite or harzburgite rock composition when the orthopyroxene component is taken into account the ophiolite samples are twice as anisotropic as the kimberlite nodules if an average anisotropy value is representative of the lithosphere then the sks delay times represent variations in anisotropic layer thickness for delay times over 1 s as the orientation is constrained to be foliation vertical and lineation horizontal the magnitude of s wave anisotropy is less sensitive than v p to variations in olivine volume fraction in range 50 100 and to deformation or fabric intensity further suggesting that s wave anisotropy is particularly apt for the determination of the anisotropic lithosphere thickness for smaller delay times there is some trade off between structural orientation and thickness

icesat altimetry data product verification at white sands space harbor three unique techniques have been developed to validate the ice cloud and land elevation satellite icesat mission altimetry data product and implemented at white sands space harbor wssh in new mexico one specific technique at wssh utilizes zenith pointed sensors to detect the laser on the surface and enable geolocation determination of the altimeter footprint that is independent of the data product generation the system of detectors also registers the laser light time of arrival which is related to the data product time tag several overflights of the wssh have validated these time tags to less than 3plusmn1 mus the ground based detector system also verified the laser illuminated spot geolocation to 10 6 m 3 5 arcsec plusmn4 5 m on one occasion which is consistent with the requirement of 3 5 m 1sigma a third technique using corner cube retroreflector signatures in the altimeter echo waveforms was also shown to provide an assessment of the laser spot geolocation although the accuracy of this technique is not equal to the other methodologies it does offer position determination for comparison to the spacecraft altimetry data product in addition elevation verifications were made using the comparison of the icesat elevation products at wssh to those acquired with an airborne light detection and ranging the elevation comparisons show an agreement to within plusmn34 cm plusmn6 7 cm under best conditions which indicate no significant errors associated with the pointing knowledge of the altimeter

a new glacier inventory for the svartisen region norway from landsat etm data challenges and change assessment glaciers are widely recognized as key indicators of climate change and their meltwater plays an important role in hydropower production in norway since the last glacier inventory was compiled in northern norway in the 1970s marked fluctuations in glacier length and mass balance have been reported for individual glaciers and the current overall glacier state is thus not well known within the framework of the global land ice measurements from space glims initiative we have created a new inventory for 489 glaciers in the svartisen region northern norway using a landsat enhanced thematic mapper plus etm satellite scene from 7 september 1999 and automated multispectral glacier mapping thresholded band ratios in addition visual inspection and correction of the generated glacier outlines has been applied adverse snow conditions and uncertain drainage divides made glacier mapping challenging in some regions of the study site glacier outlines from 1968 as digitized from a topographic map were used for a quantitative change assessment for a selection of 300 glaciers the overall area change of this sample from 1968 to 1999 was close to zero but with a strongly increasing scatter towards smaller glaciers large area gains 50 for small glaciers 1 km 2 and an unexpected stronger relative area loss towards the wetter coast the overall size changes are small 1 for the three largest ice masses in the study region vestisen ostisen and blamannsisen

surface area changes of glaciers in the tibetan plateau interior area since the 1970s using recent landsat images and historical maps the tibetan plateau interior area tpia often termed the qangtang plateau is distinguished by many dome like mountains higher than 6000 m a s l these mountains provide favourable conditions for the development of ice caps and glaciers of extreme continental subpolar type according to historical topographic maps 1959 80 and recent landsat images 2004 11 continuous retreat was observed and the glacierized part of this area decreased by 9 5 0 27 a 1 with respect to the total glacier area of 8036 4 km 2 in the 1970s glaciers in the zhari namco basin have experienced the highest area shrinkage with a reduction rate of 0 72 a 1 while the smallest reduction occurred in bangong co 0 12 a 1 and dogai coying basins 0 11 a 1 a regional gradient of area loss was found with a larger decrease in the south and a smaller decrease in the north of the plateau comparisons indicate glaciers have experienced smaller shrinkage in the tpia than in surrounding regions glacier shrinkage in the tpia is mainly attributed to an increase in air temperature while precipitation glacier size and positive difference of glaciation also played an important role

mass balance and a glacier surge of guliya ice cap in the western kunlun shan between 2005 and 2015 abstract contemporary estimates of glacier changes are necessary to assess the impact of climate change associated hazards and water resources management glaciers in high mountain asia hma are mostly retreating except the karakoram and western kunlun shan confirmed by remote sensing measurements however ground validation with precise measurements of these mass balance estimates are scarce this study selected guliya ice cap in the western kunlun shan to observe its recent changes regarding surface dynamics and mass balance using aster dem of 2005 and 2015 our findings indicate that one of the north facing glaciers surged with no previous surging history during july and early november 2015 advancing at about 8 m per day on average the mass balance shows a balance condition 0 01 0 02 m w e a 1 the icesat data 2004 2008 at selected locations compared to dgps data collected in the field during 2015 indicating a minute difference of 0 03 0 05 m a 1 with aster data in the same area our findings suggest that guliya ice cap in the western kunlun shan is in equilibrium state following a similar pattern mass gain or stable conditions as observed previously

the structure and sharpness of mg fe 2sio4 phase transformations in the transition zone abstract to calculate accurately the pressure interval and mineral proportions i e yields across the olivine to wadsleyite and wadsleyite to ringwoodite transformations requires a detailed knowledge of the non ideality of fe mg mixing in these mg fe 2 sio 4 solid solutions in order to constrain the activity composition relations that describe non ideal mixing fe mg partitioning experiments have been conducted between magnesiowustite and mg fe 2 sio 4 olivine wadsleyite and ringwoodite as a function of pressure at 1400 c using known activity composition relations for magnesiowustite the corresponding relations for the three polymorphs were determined from the partitioning data in all experiments the presence of metallic iron ensured redox conditions compatible with the earth s transition zone the non ideality of the mg fe 2 sio 4 solid solutions was found to decrease in the order w wadsleyite femg w ringwoodite femg w olivine femg these partitioning data were used along with published phase equilibria measurements for the mg 2 sio 4 and fe 2 sio 4 end member transformations to produce an internally consistent thermodynamic model for the mg 2 sio 4 fe 2 sio 4 system at 1400 c using this model the pressure interval of the olivine to wadsleyite transformation is calculated to be significantly smaller than previous determinations by combining these results with fe mg partitioning data for garnet the widths of transition zone phase transformations in a peridotite composition were calculated the olivine to wadsleyite transformation at 1400 c in dry peridotite was found to occur over a pressure interval equivalent to approximately 6 km depth and the mineral yields were found to vary almost linearly with depth across the transformation this transformation is likely to be even sharper at higher temperatures or could be significantly broader in wet mantle or in regions with a significant vertical component of mantle flow the entire range of estimated widths for the 410 km discontinuity 4 35 km could therefore be explained by the olivine to wadsleyite transformation in a peridotite composition over a range of quite plausible mantle temperatures and h 2 o contents the wadsleyite to ringwoodite transformation in peridotite mantle was calculated to take place over an interval of 20 km at 1400 c this transformation yield was also found to be near linear

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

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

spatial variability of glacier elevation changes in the swiss alps obtained from two digital elevation models 1 massive glacier thinning in the alps during the past 20 years is documented by direct mass balance measurements on nine regularly observed glaciers how representative this limited sample of glaciers is for the entire alps however remained uncertain the near global digital terrain model from the srtm enables a closer analysis of this question which is of fundamental importance to assess overall glacier volume change here we present elevation changes from 1985 to 1999 for about 1050 glaciers in the swiss alps the analysis reveals extreme thickness losses 80 m for flat low lying glacier tongues and a strong overall surface lowering the mean cumulative mass balance of the nine glaciers with direct measurements 10 8 m w e agrees well with the mean change of the entire region from dem differencing 11 m w e and can thus be considered to be representative mean thickness change of individual glaciers is correlated with their size elevation and exposure to solar irradiation this implies that mass losses of large glaciers can be underestimated when they are directly inferred from values measured at much smaller glaciers

single crystal elasticity of ringwoodite to high pressures and high temperatures implications for 520 km seismic discontinuity abstract the single crystal elastic moduli of spinel structured mg 0 91 fe 0 09 2 sio 4 ringwoodite were measured to 16 gpa at room temperature and to 923 k at ambient pressure by brillouin spectroscopy a third order finite strain equation of state yields pressure derivatives of 4 1 2 and 1 3 1 for the adiabatic bulk modulus k s and shear modulus respectively the pressure derivatives of aggregate elastic moduli for all three polymorphs and of mg fe 2 sio 4 in the mg rich end are equal within the mutual experimental uncertainties with k s p t 4 1 4 3 and p t 1 3 1 4 a linear decrease of the elastic moduli and sound velocities with temperature adequately describes the data the temperature derivatives of k s and are 0 021 and 0 016 gpa k respectively an extrapolation of our data to transition zone pressures and temperatures indicates that the shear and compressional impedance contrasts associated with mg fe 2 sio 4 mg fe 2 sio 4 transition are sufficient to produce a visible discontinuity at 520 km depth even with only a moderate 30 50 amount of olivine moreover the partitioning of fe between mg fe 2 sio 4 and mg fe 2 sio 4 and majoritic garnet will produce a relatively sharp seismic discontinuity in the order of 10 15 km even when the latent heat of reaction is taken into account the visibility of the discontinuity in regional and global studies could be inhibited by large topography that would accompany any local variations in temperature or fe content the high v p contrasts observed in some localities are difficult to explain by the transition and are suggestive of a chemical boundary this is consistent with chemical heterogeneity in the transition zone probably related to subduction one of the possible explanations for high velocity contrasts near 520 km is a buried moho a boundary between garnetite former oceanic crust and mg fe 2 sio 4 enriched former peridotite layers

heterogeneous changes of glaciers over the western kunlun mountains based on icesat and landsat 8 derived glacier inventory abstract glaciers in the northwestern qinghai tibet plateau qtp including the karakoram and western kunlun mountains wkm exhibited heterogeneous changes in recent years a latest glacier inventory of the wkm region is generated by using landsat 8 oli images year 2013 and srtm3 dem the icesat ice cloud and land elevation satellite elevation data in combination with the dem is then employed to investigate glacier thickness changes the wkm region consists of 537 glaciers 0 02 km 2 with a total area of 3137 km 2 in 2013 out of these 16 groups of glaciers covering an area about 1234 km 2 2013 showed varying surface elevation trends ranging from 0 4 0 20 m a to 0 7 24 m a over 2003 2008 except the serious thinning trend 1 15 0 41 m a detected at a surging glacier the surging glacier the zhongfeng glacier is characterized by drastic elevation variations up to 80 m and contrasting trends over the accumulation areas due to cave in and rapid transfer of ice to the downstream the heterogeneous glacier behavior in the wkm region was not only exemplified in the varying mass balances of individual glaciers but also the spatial variability of elevation trends over different glacier parts accumulation ablation areas analysis of the heterogeneity shows that such glacier dynamics were probably associated with local glacier parameters including altitude aspect glacier hypsometry and ice flow the mechanisms for the mass gain and glacier surging in the wkm region require further studies with more observations

glacier changes in the west kunlun shan from 1970 to 2001 derived from landsat tm etm and chinese glacier inventory data

the glacier inventory of china following recommendations from the international commission on snow and ice for a world glacier inventory an inventory of glaciers in china was carried out by chinese glaciologists from 1978 to 2002 each glacier was measured from aerial photographs and topographical maps and 34 parameters recorded these parameters were then analyzed statistically for the various river systems in china twelve volumes of the glacier inventory of china gic have been published consisting of 22 parts in 21 books the data were subsequently abridged into a concise gic published in chinese 2005 and in english 2008 to make the glacier inventory more accessible and better adapted for assessing glacier response to climate change after the gic was completed new aerial photographs became available and remote sensing techniques became more common to investigate glacier changes since completion of the first gic a second glacier inventory of china was initiated in 2007 this 5 year project supported by the ministry of science and technology will be undertaken mainly using remote sensing techniques

new type of olivine fabric from deformation experiments at modest water content and low stress a new type of olivine fabric was found by high strain simple shear deformation experiments in the presence of trace amounts of water at 0 5 2 2 gpa and 1470 1570 k in this fabric called e type fabric the olivine 100 axis is subparallel to the shear direction and the 001 plane is parallel to the shear plane this geometry suggests that the 100 001 slip system makes the dominant contribution to total strain this fabric is dominant at a modest water content 200 coh 1000 h 10 6 si at low stresses and high temperatures some mylonites from peridotite massifs show this type of olivine fabric which suggests the presence of water during the shear localization the seismic anisotropy caused by this fabric is qualitatively similar to that by dry fabric a type but the magnitudes of anisotropy are different between the two types for horizontal flow the amplitude of vsh vsv anisotropy is weaker but the amplitude of shear wave splitting is stronger for the e type fabric than for the a type dry fabric seismic anisotropy in the oceanic upper mantle may be due to the olivine e type fabric

seismic anisotropy in the mantle transition zone induced by shear deformation of wadsleyite abstract mantle flow in the earth s mantle transition zone between 410 and 660 km depth plays a key role to understand the nature of mantle convection which can be mapped by observed seismic anisotropy combined with crystallographic preferred orientations of mantle minerals although wadsleyite is the most important mineral to cause seismic anisotropy observed in the mantle transition zone there have been limited experimental data on its crystallographic preferred orientation because of experimental limitations we experimentally evaluated the preferred orientation of wadsleyite developed by shear deformation at pressure temperature conditions of the mantle transition zone 17 6 gpa and 1800 1900 k using a deformation dia apparatus the deformation experiments reveal that the 0 0 1 axis and the 0 1 0 plane of wadsleyite tend to be subparallel to the shear direction and the shear plane during deformation respectively these results demonstrate that polarization seismic anisotropy velocity contrast between horizontally polarized and vertically polarized s waves vsh vsv observed in the mantle transition zone might be attributed to the preferred orientation of wadsleyite caused by horizontal mantle flow

estimation and analysis of the surface velocity field of mountain glaciers in muztag ata using satellite sar data muztag ata is a mountain known as the father of glaciers in the west of china however its glacier flow pattern has never been studied in this paper the velocity of mountain glaciers on muztag ata is mapped by two methods insar and offset tacking using sar data this map provides a detailed view of the features of glacier motion on muztag ata a special effort was also made to assess the accuracy of the glacier velocity estimates to ensure the accuracy of the derived results the validation of the results was conducted over two glaciers saliymek glacier and kuksay glacier the two methods yielded similar results that agree well with each other the patterns of glacier velocity on muztag ata suggest that mountain topography westerly winds and the monsoon have a strong influence our results show that motion of glaciers in the southern and western regions of muztag ata is faster than that in the northern and eastern regions eleven glaciers were identified along which glacier velocities exhibited distinctive behavior in terms of the spatial variability of the glacier motion the occurrence of the local flow maxima and minima at consistent locations over different parts of different glaciers suggests that the subglacial topography glacier size and glacier orientation affect the overall flow patterns the velocities are very low in the surface debris cover of some glaciers which suggests debris cover has an impact on glacier motion

transmission electron microscope observation of α β and γ mg fe 2sio4 in shocked meteorites planar defects and polymorphic transitions abstract high pressure polymorphs of olivine mg fe 2sio4 have been observed by transmission electron microscopy in the shocked tenham and catherwood meteorites planar defects are characterized in and polymorphs and their possible role in polymorphic transitions is assessed and discussed in relation with the published literature the stacking fault 1 2 1 01 010 observed in the phase can produce a shear transformation to the phase if it occurs on every other 010 plane conversely the stacking fault 1 2 1 1 2 110 observed in the phase can be transformed to the phase if it is repeated on every other 110 plane and to an intermediate yet unobserved e phase if it is repeated on every 110 plane shear transformation between olivine and spinel could involve the e phase as an intermediate stage

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

strain induced seismic anisotropy of wadsleyite polycrystals and flow patterns in the mantle transition zone 1 we use forward models based on recent high pressure experimental data on mantle minerals to predict the seismic anisotropy produced by plastic strain of orthorhombic wadsleyite the dominant mineral in the upper transition zone these models predict a weak seismic anisotropy for a polycrystal of pyrolitic composition 60 wadsleyite 40 garnet at transition zone conditions 2 for p and 1 for s waves for a shear strain of 1 both p and s wave anisotropy patterns show an orthorhombic symmetry p waves propagate faster at low angle to the shear direction and slower at high angle to the shear plane s wave anisotropy is characterized by faster propagation of waves polarized at low angle to the shear direction horizontal shearing results therefore in higher velocities for horizontally propagating p waves ph and horizontally polarized s waves sh as well as in weak azimuthal variation of sv and sh velocities on the other hand vertical flow leads to higher velocities for vertically propagating p waves pv and vertically polarized s waves sv and to a weak azimuthal variation of sv velocity but to a roughly constant sh velocity analysis of global observations of seismic anisotropy in the transition zone in the light of these models supports dominant horizontal flow in the uppermost transition zone in agreement with predictions of geodynamical models that explicitly introduce phase transitions

a joint interpretation of electromagnetic and seismic tomography models suggests the mantle transition zone below europe is dry abstract the three dimensional 3d electrical conductivity distribution in the mantle transition zone mtz below europe is resolved by directly inverting geomagnetic response functions from 12 selected european observatories comparison of the conductivity image with the results of global seismic tomography reveals a good correlation between low conductivity and high velocity anomalies at depths of 400 700 km beneath the mediterranean subduction zone in central europe interpretation of the 3d conductivity model combined with seismic tomography indicates that the european mtz is drier than the mtz beneath the western pacific subduction zone even though the subducted slab material is stagnating similarly in both regions

glacier surges in the north west west kunlun shan inferred from 1972 to 2017 landsat imagery the west kunlun shan lie close to or are perhaps part of two significant glaciological phenomena the high mountain asia surge supercluster and the karakoram anomaly however glaciological studies and particularly surge studies in the range are limited here we extend the database of known surges in the region using landsat imagery and cross correlation feature tracking we examine 88 glaciers larger than 1 km2 in the hotan prefecture of xinjiang china and find evidence of nine surges occurring between 1972 and 2017 glaciers display low active phase velocities 0 2 1 5 km a 1 that show seasonal acceleration in the summer active phase periods as short as 2 years and build up and deceleration phases of months years although these observations display characteristics indicative of both the classic hydrological and thermal switch mechanisms the surging observed displays a close resemblance to that in the adjacent karakoram ranges furthermore the majority of the surges occur clustered at the end of a decadal scale warming period corroborating previously proposed causal links between climate and surging in the karakoram we suggest that the two regions should be considered part of one larger system when considering surge dynamics in high mountain asia

deformation and mantle flow beneath the sangihe subduction zone from seismic anisotropy abstract subduction of oceanic lithosphere is the most direct feedback between the earth s surface and deep interior however the detail of its interaction with the broader convecting mantle is still unclear mantle flow around subduction zones can be constrained using seismic anisotropy but despite many such studies a simple global picture is lacking the sangihe subduction zone where the molucca sea microplate is subducting westward beneath the eurasian plate is part of the tectonically complex sulawesi philippine region and an ideal natural laboratory to study complex subduction processes we investigate the anisotropic structure of the sangihe subduction zone with shear wave splitting measurements of local s and sks phases at two stations mni in sulawesi dav in the philippines as well as downgoing s phases at five stations at teleseismic distances combining different phases allows a better vertical resolution of anisotropic fabrics than is possible with a single phase the broad depth distribution of local events 60 630 km allows us to observe a change in splitting behaviour at 380 km depth above fast directions are trench parallel and delay times t are 0 34 0 53 s with no increase with depth we suggest this anisotropy is caused by aligned cracks possibly melt filled beneath the volcanic arc and fossil anisotropy in the overriding plate below 380 km is predominantly trench normal and t are slightly higher 0 53 0 65 s as no correlation is observed with inferred distance travelled inside the slab we attribute this anisotropy to shear layers atop the slab which are coherent from 200 to 400 km depth and perhaps extend into the transition zone sks and source side measurements show larger t 1 53 and 1 33 s respectively and trench parallel since these phases predominantly sample sub slab mantle we consider along strike lateral flow associated with the double sided subduction of the molucca sea microplate to be the most likely explanation we thus infer three dominant regions of anisotropy at the sangihe subduction zone one within the overriding lithosphere one along the slab wedge interface and one below the subducting molucca sea slab the mantle wedge above 200 km depth and the slab itself do not seem to contribute notably to the measured anisotropy this study demonstrates the insight seismic anisotropy can provide into mantle dynamics even in tectonically complex subduction systems

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

mantle anisotropy beneath northwest pacific subduction zones to assess the location strength and orientation of seismic anisotropy in the southern kuril japan and izu bonin subduction zones we analyzed shear wave splitting in local s phases and teleseismic sks phases fast directions from these phases are roughly parallel to the direction of absolute pacific plate motion wnw in izu bonin roughly parallel to the strike of the trench nne in central honshu and roughly n in the southern kuril back arc in the vicinity of sakhalin island assuming that the orientation and strength of anisotropy does not vary with depth modeling of splitting times from local s and teleseismic phases recorded at sakhalin island requires that the maximum depth of anisotropy lies between 480 km and 950 km in contrast splitting times for local s phases from events in izu bonin rule out anisotropy in the transition zone all the data are consistent with a model in which the lower transition zone 520 660 km and lower mantle are largely isotropic and in which anisotropy occurs intermittently in the upper transition zone 410 520 km possibly due to preferred orientation of spinel assuming that splitting in the upper mantle is produced by preferred orientation of olivine the observed fast directions indicate that the geometry of back arc strain varies systematically between subduction zones the relationship of fast directions and plate motions suggests that the subducting slab exerts significant control on back arc flow but that flow correlated with upper plate deformation must also exist

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

re analysis of seasonal mass balance at abramov glacier 1968 2014 abramov glacier located in the pamir alay kyrgyzstan is a reference glacier within the global terrestrial network for glaciers long term glaciological measurements exist from 1968 to 1998 and a mass balance monitoring programme was re established in 2011 in this study we re analyse existing mass balance data and use a spatially distributed mass balance model to provide continuous seasonal time series of glacier mass balance covering the period 1968 2014 the model is calibrated to seasonal mass balance surveys and then applied to the period with no measurements validation and recalibration is carried out using snowline observations derived from satellite imagery and after 2011 also from automatic terrestrial camera images we combine direct measurements remote observations and modelling the results are compared to geodetic glacier volume change over the past decade and to a ground penetrating radar survey in the accumulation zone resolving several layers of accumulation previously published geodetic mass budget estimates for abramov glacier suggest a close to zero mass balance for the past decade which contradicts our results we find a low plausibility for equilibrium conditions over the past 15 years instead we suggest that the glacier s sensitivity to increased summer air temperature is decisive for the substantial mass loss during the past decade

changes in glacier mass in the lenglongling mountains from 1972 to 2016 based on remote sensing data and modeling abstract glacial meltwater fed streamflow from the qilian mountains provides a much needed source of water for the northeastern margins of the tibetan plateau tp and surrounding regions we analyzed changes in glaciers located in the lenglongling mountains llm in the eastern qilian mountains in terms of glacier area and surface elevation these analyses were accomplished using multi temporal satellite images and studying digital elevation models dems based on topographic maps and zy 3 data the results showed that from 1972 to 2016 glacier coverage decreased by 41 1 km2 leaving only 62 1 km2 extant in 2016 the mean rate of change in glacier surface elevation asl was 18 7 1 2 m 0 43 0 03 m a 1 over the same period in situ measured data from ningchan no 1 glacier nc01 combined with meteorological records were also employed to develop a spatially distributed degree day model for the llm glaciers these two approaches yielded similar results allowing the reconstruction of a consistent time series that detailed annual changes in glacier mass over the past 44 years in addition we calculated that the mean annual glacial meltwater fed streamflow from 1972 to 2013 in the jiutiaoling basin jtlb northeast of the llm was equivalent to 1 4 107 m3 or 4 6 of the area s total annual streamflow it is remarkable that in years when streamflow was relatively lower such as 1972 1991 and 2013 glacial meltwater accounted for a higher proportion more than 8 of the streamflow

lake water and glacier mass gains in the northwestern tibetan plateau observed from multi sensor remote sensing data implication of an enhanced hydrological cycle abstract lakes and glaciers are widely distributed in the northwestern tibetan plateau a synchronized examination of lake and glacier mass variations there has not previously been conducted which has limited the understanding of the lake water balance and the hydrologic cycle in the region in this study we comprehensively examine lake area and volume and glacier mass changes using multi sensor satellite data we find that lake expansion in the northwestern tibetan plateau was more robust from 1976 to 2018 when compared to other regions of the plateau especially for the glacier fed and endorheic lakes lake volume changes show that most of the lakes had an increase in water volume particularly in 2000 2018 with a total water storage gain of 28 6 gt by using high resolution kh 9 and tandem x data we observe that the glacier surface elevation of the western kunlun mountains had a slight thinning rate of 0 07 0 16 m yr in 1973 2000 but a positive rate of 0 002 0 003 m yr in 2000 2018 the heterogeneous pattern of glacier elevation changes between the north n and south s slopes are revealed i e 0 02 0 01 m yr n against 0 12 0 03 m yr s in 1973 2000 and 0 05 0 02 m yr n against 0 06 0 02 m yr s in 2000 2018 overall the glaciers trend to a stable state 0 05 m yr in both the south slope of the western kunlun mountains and aru co regions between 2000 and 2018 similar patterns are also found for basin wide examinations of lake storage changes mass gains and glacier mass budgets positive or close to stable the seasonal snow cover area changes derived from cloud free modis snow cover products present a variable and insignificant trend between 2003 and 2017 snow depth derived from passive microwave remote sensing data exhibits a decreasing trend between 1979 and 2015 but the water equivalent could contribute only an insignificant amount to the observed lake changes the lake water gains and almost positive glacier mass balance imply that the hydrological cycle in the northwestern tibetan plateau has become enhanced

the misorientation index development of a new method for calculating the strength of lattice preferred orientation abstract using orientation data from experimentally deformed olivine we explore some practical problems with the j index a commonly applied measure of fabric strength we show that the j index is highly dependent on several factors including the number of discrete data in the orientation distribution function odf and arbitrary numerical parameters specified for its calculation because of this non uniqueness we conclude that the j index is difficult to interpret and should only be applied with caution as an alternative to the j index we propose a new measure of fabric strength that is based on the distribution of uncorrelated misorientation angles this m index is shown to be insensitive to the parameters specified for its calculation for typical deformed olivine samples we show that 150 discrete data are adequate to quantify fabric strength using the m index technique the m index correlates well with seismic anisotropy particularly for materials of the same fabric type therefore we conclude that the m index technique is well suited for the quantification of fabric strength and the comparison of like materials

short term glacier velocity changes at west kunlun shan northwest tibet detected by synthetic aperture radar data abstract seasonal glacier velocity changes across the high arctic including the greenland ice sheet have been observed and have attracted significant attention over the past decade however it remains uncertain how much short term variability exists in other polythermal glaciers particularly those in high asia here we report satellite radar image analyses that reveal diverse glacier surface velocities and their evolution in west kunlun shan wks nw tibet where little is known about glacier dynamics on the basis of radar images obtained from 2003 to 2011 we examined 36 glaciers and classified them into two classes according to their multi temporal velocity profiles 25 as normal flow type surface velocity reaches maxima around the middle part and gradually approaches zero toward downstream and upstream and four as surging type surface velocities are greater than 150 m yr and or the terminus advance is recognized from the radar images seven other glaciers do not fit the former two classes and reveal stagnant velocity profiles that are nearly zero in the lower part but are similar to those of the normal type in the upper part although these glaciers could be just stagnant tongues indicative of receding normal type glaciers given the temporal evolution at the zhongfeng glacier the stagnant type possibly represents a quiescent phase of the surging type glaciers while glacier surfaces are mostly clean with limited debris cover except near the termini surge type glaciers might be common in wks the observed short term velocity changes provide us with evidence for efficient basal slip even at the high elevation polythermal glaciers this study demonstrates that frequent radar image acquisitions are helpful to understand short term velocity changes at remote glaciers in detail

high pressure and temperature fabric transitions in olivine and variations in upper mantle seismic anisotropy the effects of pressure on crystallographic preferred orientation cpo of olivine aggregates were investigated through simple shear deformation experiments at pressures between 2 1 and 7 6 gpa and temperatures of 1493 1673 k under dry conditions using a deformation dia apparatus and the variations in seismic anisotropy were evaluated under the earth s upper mantle conditions we found that the monotonic decrease in seismic anisotropy with depth is caused by the pressure dependency of the seismic properties of a type developed by the 010 100 100 slip system olivine fabric while the rapid decrease is caused by the fabric transition from a type to b c type by the hk0 001 001 slip systems at 7 6 gpa and 1673 k moreover an alternative transition from a type fabric to b type like fabric by the 010 001 001 slip system occurs at 7 6 gpa and lower temperature these two temperature dependent fabric transitions occurring at 7 6 gpa result in low seismic anisotropy with vsh vsv the ratio of horizontally and vertically polarized shear waves 1 at low temperatures i e old continental mantle conditions and vsh vsv 1 at high temperatures i e oceanic mantle conditions at greater depths consistent with seismological observations thus the variations of cpo with pressure and temperature in olivine under dry conditions can explain the seismic anisotropy signatures observed in the upper mantle without invoking other mechanisms

irrigation as a potential driver for anomalous glacier behavior in high mountain asia many glaciers in the northwest of high mountain asia hma show an almost zero or positive mass balance despite the global trend of melting glaciers this phenomenon is often referred to as the karakoram anomaly although strongest positive mass balances can be found in the kunlun shan mountain range northeast of the karakoram using a regional climate model in combination with a moisture tracking model we show that the increase in irrigation intensity in the lowlands surrounding hma particularly in the tarim basin can locally counter the effects of global warming on glaciers in kunlun shan and parts of pamir and northern tibet through an increase in summer snowfall and decrease in net radiance irrigation can thus affect the regional climate in a way that favors glacier growth and future projections of glacier melt which may impact millions of inhabitants surrounding hma will need to take into account predicted changes in irrigation intensity