earthquake rupture complexity due to dynamic nucleation and interaction of subsidiary faults we numerically study the dynamic interaction of propagating cracks it is assumed that propagating cracks can nucleate and drive subsidiary cracks because of shear strain enhancement near the propagating crack tips the critical strain fracture criterion is assumed in the analysis intense interaction is expected to occur among the cracks all the cracks are assumed to be parallel and antiplane strain deformation is assumed in the computation

dynamic nucleation process of shallow earthquake faulting in a fault zone two distinct phases are commonly observed at the initial part of seismograms of large shallow earthquakes low frequency and low amplitude waves following the onset of a p wave p1 are interrupted by the arrival of the second impulsive phase p2 enriched with high frequency components this observation suggests that a large shallow earthquake involves two qualitatively different stages of rupture at its nucleation we propose a theoretical model that can naturally explain the above nucleation behaviour the model is 2 d and the deformation is assumed to be anti plane a key clement in our model is the assumption of a zone in which numbers of pre existing cracks are densely distributed this cracked zone is a model for the fault zone dynamic crack growth nucleated in such a zone is intensely affected by the crack interactions which exert two conflicting effects one tends to accelerate the crack growth and the other tends to decelerate it the accelerating and decelerating effects are generally ascribable to coplanar and non coplanar crack interactions respectively we rigorously treat the multiple interactions among the cracks using the boundary integral equation method biem and assume the critical stress fracture criterion for the analysis of spontaneous crack propagation our analysis shows that a dynamic rupture nucleated in the cracked zone begins to grow slowly due to the relative predominance of non coplanar interactions this process radiates the p1 phase if the crack continues to grow coalescence with adjacent coplanar cracks occurs after a short time then coplanar interactions suddenly begin to prevail and crack growth is accelerated the p2 phase is emitted in this process it is interpreted that the two distinct phases appear in the process of the transition from non coplanar to coplanar interaction predominance

lake seasonality across the tibetan plateau and their varying relationship with regional mass changes and local hydrology the recent growth and deepening of inland lakes in the tibetan plateau tp may be a salient indicator of the consequences of climate change the seasonal dynamics of these lakes is poorly understood despite this being potentially crucial for disentangling contributions from glacier melt and precipitation which are all sensitive to climate to lake water budget using in situ observations satellite altimetry and gravimetry data we identified two patterns of lake level seasonality in the central northern and northeastern tp lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons which is consistent with regional mass changes related to monsoon precipitation and evaporation in the northwestern tp however lake levels exhibit dramatic increases during both warm and cold seasons which deviate from regional mass changes this appears to be more connected with high spring snowfall and large summer glacier melt the variable lake level response to different drivers indicates heterogeneous sensitivity to climate change between the northwestern tp and other regions

radiocarbon constraints on ice sheet advance and retreat in the weddell sea antarctica we report here the results of a study aimed at providing radiometric age control on glacial events in the weddell sea during the late quaternary sediment cores from the eastern continental shelf where the east antarctic ice sheet was grounded have recovered glacial marine sediments resting on tills and the latter deposits predate the isotope stage 2 last glacial maximum sediment cores from the continental slope and rise sampled a prominent ice rafted debris layer and radiocarbon ages indicate that this ice rafting event took place prior to 26 000 yr b p thus the combined data indicate that significant deglaciation of the weddell sea continental shelf took place prior to the last glacial maximum our data also suggest that the ice masses that border the weddell sea are more extensive than they were during the previous glacial minimum

the death mask of the antarctic ice sheet comparison of glacial geomorphic features across the continental shelf abstract multibeam swath bathymetry data seismic lines and shallow cores were collected seaward of all of the major drainage outlets of the antarctic ice sheet from the pennell coast of north victoria land to the northwestern weddell sea the results show that during the last glacial maximum the ice sheet extended onto the outer shelf in all areas to the shelf break in many swath bathymetry and deep tow sidescan sonar data from the continental shelf also record the geomorphology left by the retreating ice sheet glacial troughs occur offshore of all major glacial outlets in each drainage area except for parts of the ross sea the inner shelf is characterized by acoustic basement interpreted as crystalline substrate the geomorphology of these inner shelf areas consists of erosional features such as grooves that show that ice flow tended to follow the structural grain of the bedrock outer shelf areas are floored by sedimentary substrate where the direction of ice flow was more directly offshore and depositional features characterize the seafloor in these areas the signature of the grounded ice consists of till deposits and large scale geomorphic features mega scale glacial lineations drumlins occur within the region of contact between crystalline and sedimentary substrates meltwater channels also have been imaged in both inner and outer shelf settings while the presence of meltwater across the shelf has long been suspected we present here the first multibeam image of a meltwater channel on the outer continental shelf of antarctica at the shelf break gullies are in all areas where we know ice reached the shelf break we note the remarkable similarity in form of mega scale glacial lineations observed on the outer shelf over sedimentary substrate across all areas surveyed typically measuring 200 600 m crest to crest this suggests that the shape of these landforms is governed by the same process in each drainage area and that process was occurring under a large area of the ice sheet the erosional and transitional features show much variability in form and distribution

ice shelf water overflow and bottom water formation in the southern weddell sea 1 cold shelf waters flowing out of the filchner depression in the southern weddell sea make a significant contribution to the production of weddell sea bottom water wsbw a precursor to antarctic bottom water aabw we use all available current meter records from the region to calculate the flux of cold water 1 9 c over the sill at the northern end of the filchner depression 1 6 0 5 sv and to determine its fate the estimated fluxes and mixing rates imply a rate of wsbw formation referenced to 0 8 c of 4 3 1 4 sv we identify three pathways for the cold shelf waters to enter the deep weddell sea circulation one path involves flow constrained to follow the shelf break the other two paths are down the continental slope resulting from the cold dense water being steered northward by prominent ridges that cross the continental slope near 36 w and 37 w mooring data indicate that the deep plumes can retain their core characteristics to depths greater than 2000 m probably aided by thermobaricity the plume water at this depth can flow at a speed approaching 1 m s 1 implying that the flow is occasionally supercritical we postulate that such supercriticality acts to limit mixing between the plume and its environment the transition from supercritical to slower more uniform flow is associated with very efficient mixing probably as a result of hydraulic jumps

southern weddell sea shelf edge geomorphology implications for gully formation by the overflow of high salinity water 1 submarine gullies are the most common morphological features observed on antarctic continental slopes the processes forming these gullies however remain poorly constrained in some areas gully heads incise the continental shelf edge and one hypothesis proposed is erosion by overflow of cold dense water masses formed on the continental shelf we examined new multibeam echo sounder bathymetric data from the weddell sea continental slope the region that has the highest rate of cold dense water overflow in antarctica ice shelf water isw cascades downslope with an average transport rate of 1 6 sverdrups sv in the southern weddell sea our new data show that within this region isw overflow does not deeply incise the shelf edge the absence of gullies extending deeply into the glacial sediments at the shelf edge implies that cold high salinity water overflow is unlikely to have caused the extensive shelf edge erosion observed on other parts of the antarctic continental margin instead the gullies observed in the southern weddell sea are relatively small and their characteristics indicative of small scale slides probably resulting from the rapid accumulation and subsequent failure of proglacial sediment during glacial maxima

bathymetry of the amundsen sea continental shelf implications for geology oceanography and glaciology the amundsen sea continental shelf is one of the most remote areas of coastal antarctica and was relatively unexplored until the late 1980s over the last two decades increased oceanographic and geological interest has led to several cruises that resulted in sufficient bathymetric data to compile a fairly detailed regional map of the amundsen continental shelf we have combined available multibeam and single beam bathymetry data from various sources and created a new regional bathymetry of the amundsen sea continental shelf and margin deep trough systems that dominate the inner shelf are aligned with present glaciers and separated by shallower ridges shaped by paleo ice streams these features merge into a small number of broader troughs on the middle shelf and shoal seaward they now serve as conduits and reservoirs for relatively warm circumpolar deep water this new compilation is a major improvement over previously available regional maps and should aid the numerical modeling of ocean circulation the reconstructions of paleo ice streams and the refinement of ice sheet models

the crary fan a trough mouth fan on the weddell sea continental margin antarctica abstract multichannel seismic investigations show the presence of a large trough mouth fan deposit on the continental margin in the southern weddell sea a characteristic feature of the fan is relatively few but large canyons and or channels which appear to have been stable for long periods levees associated with the channels may reach thicknesses of more than 1 km drilling during odp leg 113 recorded the presence of glaciers in east antarctica since early oligocene time and the seismic stratigraphic evidence suggests that the submarine fan is largely composed of glacigenic sediments the channel levee systems and complexes indicate several growth phases apparently controlled by glacial interglacial climate fluctuations with maximum fan growth during glacial periods the present interglacial period is characterized by strong and erosive flow of ice shelf water running down the western slope of the fan and carrying only minor amounts of suspended matter the fan is essentially sediment starved during interglacial periods the dimensions of the channel levee complexes and the persistent loci of sediment supply suggest that turbidite sedimentation resulted from melting of wet based glaciers at or near the shelf edge which has consequently prograded 70 80 km seaward

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

ice ocean processes over the continental shelf of the southern weddell sea antarctica a review 1 interactions between the southern ocean and the weddell sea ice shelves are important both to the antarctic ice sheet and to the production of globally significant water masses here we review the interaction between the filchner ronne ice shelf and the shelf sea in which it floats the continental shelf processes leading to the production of weddell sea deep and bottom waters from the original off shelf source waters are discussed and a new view is offered of the initial production of high salinity shelf water data from ship based measurements at the ice front from glaciological methods and from measurements made within the sub ice shelf cavity itself are used to describe the pattern of flows beneath the ice shelf we also consider the variability observed within the cavity from tidal to interannual time scales and finish with a discussion of future research priorities in the region

numerical simulation of the filchner overflow the plume of ice shelf water isw flowing into the weddell sea over the filchner sill contributes to the formation of antarctic bottom water the filchner overflow is simulated using a hydrostatic primitive equation three dimensional ocean model with a 0 5 2 sv isw influx above the filchner sill the best fit to mooring temperature observations is found with influxes of 0 5 and 1 sv below a previous estimate of 1 6 0 5 sv based on sparse mooring velocities the plume first moves north over the continental shelf and then turns west along slope of the continental shelf break where it breaks up into subplumes and domes some of which then move downslope other subplumes run into the eastern submarine ridge and propagate along the ridge downslope in a chaotic manner the next western ridge is crossed by the plume through several paths despite a number of discrepancies with observational data the model reproduces many attributes of the flow in particular we argue that the temporal variability shown by the observations can largely be attributed to the unstable structure of the flow where the temperature fluctuations are determined by the motion of the domes past the moorings our sensitivity studies show that while thermobaricity plays a role its effect is small for the flows considered smoothing the ridges out demonstrate that their presence strongly affects the plume shape around the ridges an increase in the bottom drag or viscosity leads to slowing down and hence thickening and widening of the plume

satellite image derived velocity field of an antarctic ice stream the surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery variations of ice velocity are spatially related to surface undulations and transverse velocity variations of up to 30 percent occur such large variations negate the concept of plug flow and call into question earlier mass balance calculations for this and other ice streams where sparse velocity data were used the coregistration of images with the use of the topographic undulations of the ice stream and the measurement of feature displacement with cross correlation of image windows provide significant improvements in the use of satellite imagery for ice flow determination

divergent trends in land and ocean temperature in the southern ocean over the past 18 000 years reconstructions of land and ocean temperatures over the past 18 000 years in the high southern latitudes have shown conflicting trends analyses of temperatures on campbell island south of new zealand confirm this behaviour and lead to the suggestion that it reflects changes in the position and intensity of the westerly winds over the past 18 000 years sea surface temperatures for the southern ocean do not align with those of the adjacent high latitude landmasses during the late glacial period the ocean surface warmed rapidly to present day temperatures1 whereas the land warmed only slowly as evidenced by the lagged response of forest and glaciers2 3 however in the holocene epoch land based records suggest strong warming whereas marine records indicate that ocean surface temperatures cooled here we present reconstructions of summer temperature for campbell island in the southern ocean over the past 16 500 years based on fossil pollen we find a pronounced warming 12 500 11 000 years ago a cooling until 9 200 years ago and a rapid warming to a peak between 6 000 and 5 000 years ago followed by minor cool intervals from 5 200 4 000 3 000 1 700 and 700 100 years ago as expected our temperature reconstructions show a late glacial lag behind nearby records of sea surface temperature6 7 and opposing trends in the holocene we suggest that this discrepancy arises because land based reconstructions record summer temperatures whereas marine proxies generally reflect annual temperatures we conclude that the divergence of the records therefore reflects changes in the seasonality of atmospheric heat transport as atmospheric heat transport is tied to the southern hemisphere westerly winds we attribute our observed changes to shifts in the position and intensity of the southern westerlies

estimation of lakes water storage and their changes on the northwestern tibetan plateau based on bathymetric and landsat data and driving force analyses abstract lake water storage changes in four lakes were analyzed based on in situ bathymetric survey data and landsat images in the extremely dry and cold northwestern tibetan plateau region the results indicated that bangdag co and aksai chin lake which are glacier fed and closed lakes showed decreasing trends from 1976 to 1996 then increasing trend from 1996 to 2015 during which period water storage increased by 1 24 km3 and 1 37 km3 respectively and 65 of the water storage increase in aksai chin lake during this period occurring in 2006 and 2013 longmu co which is a non glacier fed lake exhibited little variation from 1976 to 1996 and a slight increase of 0 1 km3 from 1996 to 2015 the precipitation temperature and potential evaporation ep trends indicated that lake shrinkage from 1976 to 1996 was attributed to less precipitation and less meltwater at lower surface air temperatures decreased ep 15 5 mm y contributed approximately 2 and 4 to the lake expansion of aksai chin lake and bangdag co from 2000 to 2009 based on the assumption of equal precipitation evaporation for the study area glacial meltwater contributed 76 6 to the lake expansion of bangdag co from 2000 to 2015 because change in lakes water storage showed a large difference between glacier fed lakes and non glacier fed lakes from 1996 to 2015 under relatively high precipitation conditions it is suggested that glacial meltwater exerted more influence on increasing lake water storage associated with rising temperatures

the role of subglacial water in ice sheet mass balance subglacial water can significantly affect the velocity of ice streams and outlet glaciers of ice sheets depending on the geometry and capacity of the subglacial hydrologic system increased surface melting in greenland over the coming decades may influence the ice sheet s mass balance furthermore subglacial lakes in antarctica can modulate ice velocities and act as nucleation points for new fast flowing ice streams in the coming decades significant changes in the polar regions will increase the contribution of ice sheets to global sea level rise under the ice streams and outlet glaciers that deliver ice to the oceans water and deformable wet sediments lubricate the base facilitating fast ice flow the influence of subglacial water on fast ice flow depends on the geometry and capacity of the subglacial hydrologic system water moving rapidly through a well connected system of conduits or channels will have little impact on ice sheet velocities but water injected into a spatially dispersed subglacial system may reduce the effective pressure at the base of the ice sheet and thereby trigger increased ice sheet velocities in greenland the form of the subglacial hydrologic system encountered by increasing surface melt water will determine the influence of changing atmospheric conditions on ice sheet mass balance in antarctica subglacial lakes have the capacity to both modulate velocities in ice streams and outlet glaciers and provide nucleation points for new fast ice flow tributaries climate models of ice sheet responses to global change remain incomplete without a parameterization of subglacial hydrodynamics and ice dynamics

present and future states of himalaya and karakoram glaciers a complete glacier inventory of the himalaya and karakoram h k has been created by merging records from the chinese glacier inventory several regional inventories produced by the international centre for integrated mountain development kathmandu nepal and partial inventories from the geological survey of india the only remaining gap the indian part of kashmir has been filled by a reconnaissance inventory based on soviet military maps at 1 200 000 scale representing the late 1970s it contains records for 3526 glaciers covering 9584 km 2 the new h k inventory contains records and outlines for 20 812 glaciers covering 43 178 km 2 the extent of ice in the karakoram is slightly less than in the himalaya but the karakoram glaciers are on average twice as thick 160 m as against 80 m a glacier by glacier analysis relying on estimates of mass balance for the entire mountain range and on an extension of the often used volume area scaling relation suggests that up to about one fifth of the glaciers present in 1985 may have disappeared already if mass loss were to remain constant at the average rate for 1975 2008 from 3000 to 13 000 more glaciers might disappear by 2035 if mass loss were to continue to accelerate as inferred for 1985 2008 only a few thousand to a few hundred glaciers might remain in 2035 total area and total mass would each decrease by about one half constant rate assumption or three quarters constant trend assumption these projections which are uncertain and neglect some possibly important mitigating controls such as variable extents of debris cover and the feedback due to retreat to higher elevations demonstrate the need for more complete analyses to inform public perceptions of and policy decisions relating to the health of h k glaciers

late weichselian submarine debris flow deposits on the bear island trough mouth fan sedimentary processes on the bear island trough mouth fan during the last glacial were studied using high resolution reflection seismics and gravity cores the fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km2 the large debris flows were generated when the barents sea ice sheet reached the shelf break glacigenic sediments transported to the grounding line were temporarily stored on the upper slope due to the high sedimentation rate the sediments were unstable and earthquakes oversteepening and or build up of excess pore pressure triggered sediment release generating large debris flows sediments were also eroded and incorporated during the downslope flow debris flows were the most important sediment distributing process due to the relatively high shear strength low flow mobility of the glacigenic diamicton and the low fan gradient the weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the early and mid weichselian the barents sea ice sheet might have reached the shelf break twice during the late weichselian on average one large debris flow comprising 18 km3 of sediments was released between every 35 to 75 years during the last glacial maximum

the role of lateral drag in the dynamics of ice stream b antarctica the partitioning of resistive force between the bed and sides of ice stream b antarctica is obtained for three large areas that have been measured using repeat aerial photogrammetry problems associated with data errors and local variations in ice strength and velocity are reduced by considering the areally averaged budget of forces for each photo block results indicate that the bed under ice stream b must be very weak and unable to provide muche resistance mechanical control on this ice stream emanates almost entirely from the lateral margins

flow of the west antarctic ice sheet on the continental margin of the bellingshausen sea at the last glacial maximum geophysical data show that during the last glaciation the west antarctic ice sheet wais drained to the continental shelf edge of the bellingshausen sea through a cross shelf bathymetric trough belgica trough as a grounded fast flowing ice stream the drainage basin feeding this ice stream probably encompassed southwestern palmer land parts of southern alexander island and the bryan coast of ellsworth land with an area exceeding 200 000 km2 on the inner continental shelf streamlined bedrock and drumlins mapped by swath bathymetry show that the ice stream was fed by convergent ice flow draining from eltanin bay and bays to the east as well as by ice draining the southern part of the antarctic peninsula ice sheet through the ronne entrance the presence of a paleoice stream in belgica trough is indicated by megascale glacial lineations formed in soft till and a trough mouth fan on the continental margin grounding zone wedges on the inner and midshelf record ice marginal stillstands during deglaciation and imply a staggered pattern of ice sheet retreat these new data indicate an extensive wais at the last glacial maximum lgm on the bellingshausen sea continental margin which advanced to the shelf edge in conjunction with ice sheet reconstructions from the antarctic peninsula and pine island bay this implies a regionally extensive ice sheet configuration during the lgm along the antarctic peninsula bellingshausen sea and amundsen sea margins with fast flowing ice streams draining the wais and antarctic peninsula ice sheet to the continental shelf edge

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

use of total grain size distributions to define bed erosion and transport for poorly sorted sediment undergoing simulated bioturbation abstract flume experiments were conducted using poorly sorted beds made to resemble those glacial deposits that blanket the antarctic seafloor today flow within the flume was gradually increased over 2 cm s 1 increments up to 20 cm s 1 an initial run was made without altering the bed and two additional runs were made in which the bed was mechanically mixed in order to simulate bioturbation initial and efficient transport of a given size particle was determined using total grain size distribution data for samples taken from the residual bed from trays placed at different elevations above the floor of the flume and from the water column using this method we were able to measure the current velocities at which initial movement occurred as well as relate different modes of transport for given size ranges to current velocity without mixing the bed current velocities greater than 16 cm s 1 were required to initiate particle movement but because the bed became armored this initial movement was not reflected in the total grain size distribution of the bed with mixing a residual bed containing little silt and clay was produced at velocities of only a few centimeters per second once fines were removed from the bed sand sized material began to move by either traction or saltation a curve relating current velocity to sediment transport by bed load traction and saltation intermittent suspension and suspension is presented the results of our flume experiments demonstrate how sorted sediments are presently being derived from cohesive often overcompacted poorly sorted glacial sediments on high latitude continental shelves where measured current velocities are less than 20 cm s 1 the antarctic seafloor for example furthermore we have gained important information about the true meaning of grain size data as it relates to current velocity mean grain size sorting and skewness reflect not only current velocity but also the efficiency with which the bed was mixed therefore attempts to reconstruct paleovelocity using only these parameters may be meaningless

the sedimentary legacy of a palaeo ice stream on the shelf of the southern bellingshausen sea clues to west antarctic glacial history during the late quaternary a major trough belgica trough eroded by a palaeo ice stream crosses the continental shelf of the southern bellingshausen sea west antarctica and is associated with a trough mouth fan belgica tmf on the adjacent continental slope previous marine geophysical and geological studies investigated the bathymetry and geomorphology of belgica trough and belgica tmf erosional and depositional processes associated with bedform formation and the temporal and spatial changes in clay mineral provenance of subglacial and glaciomarine sediments here we present multi proxy data from sediment cores recovered from the shelf and uppermost slope in the southern bellingshausen sea and reconstruct the ice sheet history since the last glacial maximum lgm in this poorly studied area of west antarctica we combined new data physical properties sedimentary structures geochemical and grain size data with published data shear strength clay mineral assemblages to refine a previous facies classification for the sediments the multi proxy approach allowed us to distinguish four main facies types and to assign them to the following depositional settings 1 subglacial 2 proximal grounding line 3 distal sub ice shelf sub sea ice and 4 seasonal open marine in the seasonal open marine fades we found evidence for episodic current induced winnowing of near seabed sediments on the middle to outer shelf and at the uppermost slope during the late holocene in addition we obtained data on excess pb 210 activity at three core sites and 44 ams c 14 dates from the acid insoluble fraction of organic matter aio and calcareous micro fossils respectively at 12 sites these chronological data enabled us to reconstruct for the first time the timing of the last advance and retreat of the west antarctic ice sheet wais and the antarctic peninsula ice sheet apis in the southern bellingshausen sea we used the down core variability in sediment provenance inferred from clay mineral changes to identify the most reliable aio c 14 ages for ice sheet retreat the palaeo ice stream advanced through belgica trough after similar to 36 0 corrected c 14 ka before present b p it retreated from the outer shelf at similar to 25 5 ka b p the middle shelf at similar to 19 8 ka b p the inner shelf in eltanin bay at similar to 12 3 ka b p and the inner shelf in ronne entrance at similar to 6 3 ka b p the retreat of the wais and apis occurred slowly and stepwise and may still be in progress this dynamical ice sheet behaviour has to be taken into account for the interpretation of recent and the prediction of future mass balance changes in the study area the glacial history of the southern bellingshausen sea is unique when compared to other regions in west antarctica but some open questions regarding its chronology need to be addressed by future work c 2010 elsevier ltd all rights reserved

extent and dynamics of the west antarctic ice sheet on the outer continental shelf of pine island bay during the last glaciation abstract swath bathymetry and topas sub bottom profiler acoustic data reveal the presence of a major cross shelf bathymetric trough containing streamlined subglacial bedforms formed in soft till that extends to the continental shelf edge of outer pine island bay amundsen sea west antarctica the new data indicate that the west antarctic ice sheet wais extended to the shelf edge of pine island bay during the last glaciation and was drained by a grounded fast flowing palaeo ice stream through this outer shelf trough topography and subglacial geology are likely to have exerted a strong control on the development and location of palaeo ice streams in pine island bay topas records show that mega scale glacial lineations are formed in an acoustically transparent sediment layer interpreted to be soft till and are inferred to be the product of subglacial sediment deformation beneath the palaeo ice stream the flat to irregular nature of the basal reflector of the acoustically transparent layer of soft till implies that a combination of groove ploughing of the substrate and subglacial sediment deformation were important processes beneath the palaeo ice stream in the outer trough of pine island bay as well as palaeo ice streams elsewhere in antarctica therefore the formation of the soft till layer and possibly associated subglacial bedforms are likely to be a function of these palaeo ice stream processes in a regional context the wais extended to the continental shelf edge of the bellingshausen amundsen and ross seas and was drained by a number of palaeo ice streams during the last glaciation

recommendations for the compilation of glacier inventory data from digital sources modern geoinformatic techniques allow the automated creation of detailed glacier inventory data from glacier outlines and digital terrain models dtms once glacier entities are defined and an appropriate dtm is available several methods exist to derive the inventory data e g minimum maximum and mean elevation mean slope and aspect for each glacier from digital intersection of both datasets compared to the former manual methods the new grid based statistical calculations are very fast and reproducible the major aim of this contribution is to help in standardizing the related calculations to enhance the integrity of the global land ice monitoring from space glims database the recommendations were prepared by a working group and also contribute to the european space agency project globglacier the document follows the former unesco manual for the production of the world glacier inventory published in 1970 identifies the potential pitfalls and describes the differences from the former methods of compilation the online background material for this paper see http www glims org contains example scripts for calculation of each parameter and will be updated when required

two types of brittle fracture of silicate rocks under confining pressure and their implications in the earth s crust abstract four silicate rocks granite gabbro dunite and eclogite were triaxially compressed up to a confining pressure of 3 gpa at room temperature and were found to exhibit brittle fracture behaviour from the measurements of the compressive and frictional strengths and the activity of acoustic emission ae and the observations of the microstructure of fractured specimens the pattern of fracture was found to change when the compressive strength became equal to the frictional strength two types of fracture mechanism low pressure and high pressure types were inferred the low pressure type fracture exhibits features of brittle fracture equivalent to those recorded by previous workers the features of high pressure type fracture are similar to those observed between brittle fracture and ductile creep in high temperature triaxial experiments microcracks are not concentrated close to the main fault and the main fault is sharp and oriented at approximately 45 to the stress direction this suggests that the high pressure type fracture might correspond to the transitional fracture type between the brittle and ductile regimes at room temperature for granite and gabbro samples of a few centimeters size high pressure type fracturing begins at 0 8 gpa confining pressure while for dunite and eclogite it begins at 1 0 and 2 0 gpa respectively the size effect on compressive strength under confining pressure was estimated based on the suggestion that the uniaxial strength decreases with increasing specimen size and ceases to decrease for specimens 1 m this estimation suggests that the compressive strength for a granite specimen a few meters in size would become equal to the frictional strength at confining pressures as low as 60 mpa the significance of this is that it may be necessary to model earthquakes using the high pressure type fracturing because in the absence of pore pressure 60 mpa confining pressure corresponds to a depth of 3 km faulting processes in the crust including both the initial faulting and the movement of existing faults were inferred using the experimental results and the estimated size effect on strength

climate evolution at the last deglaciation the role of the southern ocean abstract two sediment sequences recovered close to and south of the present polar front 50 53 s in the atlantic sector of the southern ocean were analysed in order to evaluate the environmental evolution of the southern ocean surface over the last deglaciation and the holocene our reconstruction is based on radiocarbon dated records of diatom based sea surface temperature and sea ice proxies and planktic foraminiferal stable isotopes the onset of the deglacial warming and gradual southward retreat of the winter sea ice field between 18 and 17 cal kyr bp occurrence of a thermal reversal centered at ca 13 cal kyr bp antarctic cold reversal or acr and early holocene occurrence of the climatic optimum well correlate with climatic reconstructions available from the indian southern ocean and from antarctic ice cores time correspondence of southern ocean warming and heinrich event 1 in the north atlantic is compatible with the transmission of the climate signal from the northern to the southern hemisphere through the bipolar seesaw our data support modeling results suggesting that the northern hemisphere bolling warming and turn on of the north atlantic deep water formation are triggered by gradual warming and sea ice retreat in the southern ocean meltwater shedding into the southern ocean associated with the acr may maintain northern hemisphere warming during the allerod the development of sea surface warming and sea ice retreat is compatible with a southern ocean control on the atmospheric co2 increase during the deglaciation during the early holocene 9 7 cal kyr bp our southern core records renewed surface ocean cooling and northward readvance of the winter sea ice field such early holocene cooling is common to cores from the high latitude atlantic sector and might be brought about by expansion of the weddell gyre circulation at that time

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

application of inventory data for estimating characteristics of and regional climate change effects on mountain glaciers a pilot study with the european alps a parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate change effects on mountain glaciers for past and potential climate scenarios glacier changes for assumed mass balance changes are calculated as step functions between steady state conditions for time intervals that approximately correspond to the characteristic dynamic response time a few decades of the glaciers in order to test the procedure a pilot study was carried out in the european alps where detailed glacier inventories had been compiled around the mid 1970s total glacier volume in the alps is estimated at about 130 km3 for the mid 1970s strongly negative mass balances are likely to have caused a loss of about 10 20 of this total volume during the decade 1980 90 backward calculation of glacier length changes using a mean annual mass balance of 0 25m w e a 1 since the end of the little ice age around 1850 ad gives considerable scatter but satisfactory overall results as compared with long term observations the total loss of alpine surface ice mass since 1850 can be estimated at about half the original value an acceleration of this development with annual mass losses of around 1 m a 1 or more as anticipated from ipcc scenario a for the coming century could eliminate major parts of the presently existing alpine ice volume within decades

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

landsat based inventory of glaciers in western canada 1985 2005 abstract we report on a glacier inventory for the canadian cordillera south of 60 n across the two western provinces of british columbia and alberta containing 30 000 km2 of glacierized terrain our semi automated method extracted glacier extents from landsat thematic mapper tm scenes for 2005 and 2000 using a band ratio tm3 tm5 we compared these extents with glacier cover for the mid 1980s from high altitude aerial photography for british columbia and from landsat tm imagery for alberta a 25 m digital elevation model dem helped to identify debris covered ice and to split the glaciers into their respective drainage basins the estimated mapping errors are 3 4 and arise primarily from seasonal snow cover glaciers in british columbia and alberta respectively lost 10 8 3 8 and 25 4 4 1 of their area over the period 1985 2005 the region wide annual shrinkage rate of 0 55 a 1 is comparable to rates reported for other mountain ranges in the late twentieth century least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover the highest relative ice loss in british columbia 24 0 4 6 occurred in the northern interior ranges while glaciers in the northern coast mountains declined least 7 7 3 4

flow and retreat of the late quaternary pine island thwaites palaeo ice stream west antarctica multibeam swath bathymetry and sub bottom profiler data are used to establish constraints on the flow and retreat history of a major palaeo ice stream that carried the combined discharge from the parts of the west antarctic ice sheet now occupied by the pine island and thwaites glacier basins sets of highly elongated bedforms show that at the last glacial maximum the route of the pine island thwaites palaeo ice stream arced north northeast following a prominent cross shelf trough in this area the grounding line advanced to within similar to 68 km of and probably reached the shelf edge minimum ice thickness is estimated at 715 m on the outer shelf and we estimate a minimum ice discharge of similar to 108 km 3 yr 1 assuming velocities similar to today s pine island glacier similar to 2 5 km yr 1 additional bed forms observed in a trough northwest of pine island bay likely formed via diachronous ice flows across the outer shelf and demonstrate switching ice stream behavior the style of ice retreat is also evident in five grounding zone wedges which suggest episodic deglaciation characterized by halts in grounding line migration up trough stillstands occurred in association with changes in ice bed gradient and phases of inferred rapid retreat correlate to higher bed slopes supporting theoretical studies that show bed geometry as a control on ice margin recession however estimates that individual wedges could have formed within several centuries still imply a relatively rapid overall retreat our findings show that the ice stream channeled a substantial fraction of west antarctica s discharge in the past just as the pine island and thwaites glaciers do today

ice core evidence of westerly and monsoon moisture contributions in the central tibetan plateau stable isotopes are a primary tool for inferring past temperature changes and atmospheric moisture variability from ice cores a 33 m ice core representing the period 1850 2004 was retrieved from the tanggula mountains central tibetan plateau 5743 m a s l in august 2005 annual average stable isotope d 18 o dd values generally increase during the period while the second order parameter of deuterium excess d excess generally decreases high annual average d excess values 18 2 throughout the ice core suggest a significant contribution of continental recycled moisture d excess values shift from relatively higher values during 1850 1940 to lower values since the 1940s annual isotope values and reconstructed accumulation are compared with climate indices local station temperature records and northern india monsoon precipitation significant correlation is observed between d 18 o and the southern oscillation nino3 4 and dipole mode indices annual average d excess values revealed a significant negative correlation with the dipole mode index results suggest a relatively greater contribution of westerly dominated continental moisture prior to the 1940s and an increase in the contribution of moisture evaporated under more humid conditions since the 1940s

continuous profiles of electromagnetic wave velocity and water content in glaciers an example from bench glacier alaska usa we conducted two dimensional continuous multi offset georadar surveys on bench glacier south central alaska usa to measure the distribution of englacial water we acquired data with a multichannel 25 mhz radar system using transmitter receiver offsets ranging from 5 to 150 m we towed the radar system at 5 10 km h 1 with a snow machine with transmitter receiver positions established by geodetic grade kinematic differentially corrected gps nominal 0 5 m trace spacing for radar velocity analyses we employed reflection tomography in the pre stack depth migrated domain to attain an estimated 2 velocity uncertainty when averaged over three to five wavelengths we estimated water content from the velocity structure using the complex refractive index method equation and use a three phase model ice water air that accounts for compression of air bubbles as a function of depth our analysis produced laterally continuous profiles of glacier water content over several kilometers these profiles show a laterally variable stratified velocity structure with a low water content 0 0 5 shallow layer 20 30 m underlain by high water content 1 2 5 ice

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

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

three dimensional observations of faulting process in westerly granite under uniaxial and triaxial conditions by x ray ct scan abstract observations of spatial fault development in granite undergoing compression provide new insights into the process of faulting dry intact westerly granite samples were loaded under a confining pressure of 100 mpa triaxial conditions and 5 mpa uniaxial conditions and the progress of faulting was controlled by maintaining the increment of circumferential displacement at a constant rate which apparently stiffened the machine the samples were unloaded after they experienced some degree of stress drop and were successfully recovered before faulting progressed further a conventional medical x ray ct scanning system was used to image the sample interiors three dimensional fault systems were detected with sequential x ray ct images it was found that three dimensional reconstruction by x ray ct images yields not only three dimensional images of the fault system but also provides fault cross section images with much less artificial noise artifacts than does direct x ray ct imaging three dimensional images show that a fault system that developed under uniaxial conditions is much more complicated than a fault system produced by triaxial conditions in addition the fault plane produced under uniaxial conditions is inclined at a lower angle to the maximum compressive axis than under triaxial conditions comparing x ray ct images we show that a fault nucleates locally on the sample surface just after peak stress then develops into the final fault plane in the residual stress stage of the complete stress strain relationship under triaxial conditions

asperities barriers characteristic earthquakes and strong motion prediction recent results from paleoseismology suggest that earthquakes recurrent on a given fault may often have the same characteristic length and amount of slip stable asperities and barriers which survive many earthquakes can explain these results the activity of volcano usu japan since 1977 which produced a dacite dome with a total upheaval of 180 m offered a great opportunity to study the recurrence behavior of a fault seismologists at hokkaido university revealed a family of repeated earthquakes with nearly the same amount of slip generated from the same fault plane on the crater wall along which the dome moved upward this family can be explained by the existence of a stable asperity on the crater wall and is called the asperity type family they found however another type of family of earthquakes which share the same fault plane but show a great range of variation in the amount of slip the behavior of the latter family can be explained by the presence of weak barriers over a fault plane defined by strong stable barriers and this family is referred to as the barrier type family this type of earthquake model has been used successfully in the interpretation of observed strong motion acceleration spectra from california and the results reveal the stability of local stress drop among different earthquakes the agreement found between local stress drops estimated from strong motion data and those inferred from geological observation supports the possibility for predicting earthquake strong motion directly from geological observation of the causative fault

clay mineral provenance of sediments in the southern bellingshausen sea reveals drainage changes of the west antarctic ice sheet during the late quaternary the belgica trough and the adjacent belgica trough mouth fan in the southern bellingshausen sea pacific sector of the southern ocean mark the location of a major outlet for the west antarctic ice sheet during the late quaternary the drainage basin of an ice stream that advanced through belgica trough across the shelf during the last glacial period comprised an area exceeding 200 000 km 2 in the west antarctic hinterland previous studies mainly based on marine geophysical data from the continental shelf and slope focused on the bathymetry and seafloor bedforms and the reconstruction of associated depositional processes and ice drainage patterns in contrast there was only sparse information from seabed sediments recovered by coring in this paper we present lithological and clay mineralogical data of 21 sediment cores collected from the shelf and slope of the southern bellingshausen sea most cores recovered three lithological units which can be attributed to facies types deposited under glacial transitional and seasonally open marine conditions the clay mineral assemblages document coinciding changes in provenance the relationship between the clay mineral assemblages in the subglacial and proglacial sediments on the shelf and the glacial diamictons on the slope confirms that a grounded ice stream advanced through belgica trough to the shelf break during the past thereby depositing detritus eroded in the west antarctic hinterland as soft till on the shelf and as glaciogenic debris flows on the slope the thinness of the overlying transitional and seasonally open marine sediments in the cores suggests that this ice advance occurred during the last glacial period clay mineralogical acoustic sub bottom and seismic data furthermore demonstrate that the palaeo ice stream probably reworked old sedimentary strata including older tills on the shelf and incorporated this debris into its till bed the geographical heterogeneity of the clay mineral assemblages in the sub and proglacial diamictons and gravelly deposits indicates that they were eroded from underlying sedimentary strata of different ages these strata may have been deposited during either different phases of the last glacial period or different glacial and interglacial periods additionally the clay mineralogical heterogeneity of the soft tills recovered on the shelf suggests that the drainage area of the palaeo ice stream flowing through belgica trough changed through time c 2009 elsevier b v all rights reserved

glacigenic and associated marine sediments in the weddell sea fjords of spitsbergen and the barents sea a review abstract studies of glacigenic and associated marine sediments in the weddell sea fjords of spitsbergen and barents sea show that during periods of limited glacial coverage interstadials large amounts of material may be brought into the sea mainly by meltwater the major load is deposited relatively close to the icefront 1 at times of maximum glacial extent grounded ice extends onto the shelf with the shelf edge as the outer limit and land and inner shelf areas are eroded main glacial depositional sites are then the outer shelf and shelf edge the sedimentary environment outside an ice shelf is characterized by low clastic supply mainly deposited from icebergs due to low turbidity and a supply of nutrient rich water biogenic matter accumulates leading to a glaciomarine sequence rich in bioclastics sea level lowering results in grounding and seaward expansion of the ice shelf subsequent eustatic rise causes the grounded ice to float deglaciation and sea level rise reduces clastic input to the shelves glacial sediments are reworked and carbonates may accumulate forming tillite carbonate sequence e g late precambrian break up of marine ice sheets such as the barents sea ice sheet seems to have taken place stepwise in response to eustatic rise and climatic changes

the retreat of glaciers in response to recent climate warming in western china glaciers in china are primarily located in the tibetan plateau tp and surrounding high mountains the chinese glacier inventory indicates that there are 46 377 glaciers in western china meteorological records indicate that air temperature in western china has risen by 0 2 c per decade since 1951 and 1998 was the warmest year precipitation in the region increased by 5 10 per decade from 1953 to 1997 using remote sensing and geographic information system methods we have monitored the changes in 5000 glaciers over the past 50 years we conclude that 80 of glaciers in western china have retreated losing 4 5 of their combined areal coverage although some glaciers have advanced in addition regional differences characterize glacier changes over the past few decades for example glaciers in the central and northwestern tp were relatively stable while glaciers in the mountains surrounding the tp experienced extensive wastage mass balance variations for some glaciers show accelerated ice shrinkage in the last two decades

marine geological constraints for the grounding line position of the antarctic ice sheet on the southern weddell sea shelf at the last glacial maximum abstract the history of grounded ice sheet extent on the southern weddell sea shelf during the last glacial maximum lgm and the timing of post lgm ice sheet retreat are poorly constrained several glaciological models reconstructed widespread grounding and major thickening of the antarctic ice sheet in the weddell sea sector at the lgm in contrast recently published onshore data and modelling results concluded only very limited lgm thickening of glaciers and ice streams feeding into the modern filchner and ronne ice shelves these studies concluded that during the lgm ice shelves rather than grounded ice covered the filchner and ronne troughs two deep palaeo ice stream troughs eroded into the southern weddell sea shelf here we review previously published and unpublished marine geophysical and geological data from the southern weddell sea shelf the stratigraphy and geometry of reflectors in acoustic sub bottom profiles are similar to those from other west antarctic palaeo ice stream troughs where grounded ice had advanced to the shelf break at the lgm numerous cores from the southern weddell sea shelf recovered sequences with properties typical for subglacially deposited tills or subglacially compacted sediments these data sets give evidence that grounded ice had advanced across the shelf during the past thereby grounding in even the deepest parts of the filchner and ronne troughs radiocarbon dates from glaciomarine sediments overlying the subglacial deposits are limited but indicate that the ice grounding occurred at the lgm and that ice retreat started before 15 1 corrected 14c kyrs before present bp on the outer shelf and before 7 7 corrected 14c kyrs bp on the inner shelf which is broadly synchronous with ice retreat in other antarctic sectors the apparent mismatch between the ice sheet reconstructions from marine and terrestrial data can be attributed to ice streams with very low surface profiles similar to those of ice plains that had advanced through filchner trough and ronne trough at the lgm considering the global sea level low stand of 130 m below present a low surface slope of the expanded lgm ice sheet in the southern weddell sea can reconcile grounding line advance to the shelf break with limited thickening of glaciers and ice streams in the hinterland this scenario implies that ice sheet growth in the weddell sea sector during the lgm and ice sheet drawdown throughout the last deglaciation could only have made minor contributions to the major global sea level fluctuations during these times

a major trough mouth fan on the continental margin of the bellingshausen sea west antarctica the belgica fan a 330 km length of the little known continental shelf edge and slope of the bellingshausen sea west antarctica is investigated using multibeam swath bathymetric and sub bottom profiler evidence the shelf break is at 650 700 m across the 150 km wide belgica trough and to either side is about 500 m when full glacial ice advanced across the shelf to reach the shelf break it was partitioned into fast and slow flowing elements with an ice stream filling the trough this had important consequences for the nature and rate of sediment delivery to the adjacent continental slope off belgica trough the upper continental slope has convex outward contours indicating a major sedimentary depocentre of gradient 1 2 degrees acoustic profiles and cores from the depocentre show a series of diamictic glacigenic debris flows the depocentre is interpreted as a trough mouth fan built largely by debris delivered from the ice stream the slope is steeper beyond the trough margins at up to 6 degrees the main morphological features on the bellingshausen sea slope are gully systems and channels major canyons and late quaternary slides are absent most gullies and channels are found on the fan gullies are about 15 25 m deep a few hundred metres wide and some are 25 km long the largest channel is over 60 km long about a kilometre wide and 10 to 15 m deep the channels provide pathways for sediment by passing of the upper slope and transfer to the continental rise and beyond by turbidity currents gullies on the bellingshausen sea margin cut through debris flows on the slope assuming the debris flows are linked mainly to downslope transport of diamictic debris when ice was at the shelf edge under full glacial conditions then those gullies cut into them formed during deglaciation belgica fan is 22 000 km 2 in area and about 60 000 km 3 in volume it is the largest depocentre identified to date on the continental margin of the west antarctic ice sheet fed by an interior ice sheet basin of approximately 200 000 km 2 c 2008 elsevier b v all rights reserved

analysis of the internal structure of rocks and characterization of mechanical deformation by a non destructive method x ray tomodensitometry abstract tomodensitometry is a new non destructive method which reveals the internal structure of rocks through analysis of x ray images without any damage to the sample the scanner gives a radiological density which is a function of gravimetric density and mineralogy for limestones and sandstones an attempt is made to quantify the relation between radiological density and porosity spatial variations in the values of the radiological density measured on rock core specimens that are deformed and fractured in a triaxial cell are then related to the intensity of experimental volumetric deformation

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

ice sheet extent of the antarctic peninsula region during the last glacial maximum lgm insights from glacial geomorphology we present marine geological and geophysical data for the antarctic peninsula that call for a larger ice sheet reconstruction during the last glacial maximum lgm than suggested by previous studies such glacial reconstructions are important for quantifying post lgm sea level rise and providing boundary conditions for general circulation models megascale glacial lineations on the continental shelf surrounding antarctica provide documentation for grounded ice that was streaming swath bathymetry data nbp02 01 reveal lineations in each of the major glacial troughs except for smith trough which features grooves and bedrock drumlins 0 5 3 km spacing 1 20 elongation ratios on crystalline bedrock we place the maximum extent of ice at the seaward limit of the lineations at or near megascale glacial lineations imaged in this study and other areas surrounding antarctica including the ross sea pine island bay have a consistent morphology with elongation ratios of 80 1 and spacings of 200 600 m mode of 300 m in contrast lineations bundles canals et al 2000 in the gerlache boyd trough exhibit larger spacing 1 5 km and the upstream portions 7 km are carved directly into bedrock rather than till as suggested by previously unpublished air gun 120 hz seismic data these features have yet to be dated however they are believed to have been active during the lgm radiocarbon dates in glaciomarine sediments foraminifera and organic matter from seven glacial troughs indicate that megascale glacial lineations were formed during the lgm other geomorphic features such as the grounding zone wedge in the northwestern weddell sea formed when the ice sheet was retreating the initial retreat of the grounded ice from the outer shelf occurred by 18 500 cal yr b p the inner shelf was mostly ice free by 13 000 cal yr b p this is significantly earlier than numerical models which suggest antarctic deglaciation began at 12 000 cal yr b p this also suggests the peninsula area contributed to global sea level rise associated with meltwater pulse mwp 1a

monitoring the glacier changes in the muztag ata and konggur mountains east pamirs based on chinese glacier inventory and recent satellite imagery glaciers in the muztag ata and konggur mountains of the eastern pamir plateau northwestern china have been monitored by applying aerial photo stereo models 1962 66 and landsat tm 1990 and etm 1999 images all of which have been compared in order to detect areal and frontal changes through the past four decades the mean frontal retreat of glaciers in the muztag ata and konggur mountains increased from 6 0 m a 1 between 1962 66 and 1990 to 11 2 m a 1 between 1990 and 1999 with an overall glacier length reduction of 9 9 for the whole study period the glacier area has decreased by 7 9 mainly due to changes observed in the most recent period 1990 99 when the annual area loss almost tripled to 1 01 km 2 a 1 based on meteorological data from taxkogan station since 1957 we conclude that climate change particularly the rise in summer temperature after 1994 is the main forcing factor in glacier shrinkage

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

morphology and sedimentary processes on the continental slope off pine island bay amundsen sea west antarctica morphology and sedimentation on the pine island bay continental margin eastern amundsen sea is investigated using swath bathymetry parametric subbottom profiler topas records and sediment cores a major cross shelf trough extends to the continental shelf edge at 114 w through which fast flowing ice drained the west antarctic ice sheet under full glacial conditions the slope adjacent to the trough mouth is 4 whereas to the east and west it is steeper a bulge in bathymetric contours beyond and east of the trough mouth indicates some slope progradation elsewhere seismic reflection profiles indicate major shelf aggradation and minor slope progradation networks of gullies and channels dominate the slope adjacent to pine island bay in front of the trough mouth gullies at the shelf edge and uppermost slope connect directly with channels that continue to the continental rise other gullies connect indirectly with channels further downslope topas records indicate that gully channel systems acted as conduits for coarse grained sediment transfer cores comprise turbidites representing channel deposits and diamicton facies deposited by debris flows sandy turbidites interbedded with hemipelagic muds occur on the rise and abyssal plain the west antarctic ice sheet extended to the shelf edge during full glacials delivering water saturated till and turbid water directly to the continental slope along a line source gully channel systems are probably a product of sediment gravity flows derived from the release of water saturated till and turbid water along the ice sheet margin perhaps augmented subsequently by downslope flow of dense cold and saline water associated with sea ice production during the holocene the gully channel systems enable sediment to bypass the continental slope spatial variations in gully channel system morphology along the amundsen sea continental slope are probably linked to differences in sediment gravity flow processes and the rate and composition of sediment delivered to the shelf edge from the ice sheet cored sediments on the slope and abyssal plain record the widespread presence of turbidite sands indicating that downslope transfer of glacier derived sediments has taken place this supports our interpretation that submarine channels are derived from and are conduits for mass wasting submarine channels on the upper slope continue into the abyssal plain as far north as 67 s they are separated by sediment drifts and sediment waves resulting from the interaction between downslope turbidity current processes and along slope bottom currents similar deep sea sedimentary processes operate along much of west antarctica and the western side of the antarctic peninsula

distribution of glacial geomorphic features on the antarctic continental shelf and correlation with substrate implications for ice behavior surveys were conducted seaward of all the major drainage outlets of the antarctic ice sheet from the pennell coast north victoria land to marguerite bay antarctic peninsula the results show that the ice sheet extended onto the outer shelf glacial troughs occur offshore of all major glacial outlets where the substrate is crystalline bedrock ice flow tended to follow the structural grain of the bedrock deposited little sediment and eroded the underlying bedrock where ice flowed over relatively soft more easily eroded sedimentary strata the direction of ice flow was more directly offshore and depositional features characterize the sea floor in these areas the signature of the grounded ice consists of till deposits and large scale geomorphic features drumlins occur within the region of contact between crystalline and sedimentary substrates the different geological substrates are interpreted to have exerted a fundamental control on the behavior of past ice sheets the troughs in the areas of bedrock composed of sedimentary substrate are interpreted to have been occupied by relatively fast flowing ice ice streams and the troughs in the areas of crystalline substrate are interpreted to have been occupied by slower moving ice the area between these two zones was characterized by ice acceleration and is marked by drumlins

observed changes of cryosphere in china over the second half of the 20th century an overview during approximately the past five decades changes in snow cover mountain glaciers frozen ground including permafrost sea ice and river ice have been observed in china however most data were published in chinese and thus unknown to the international communities here we review these published results to show an overview of cryospheric changes in china for the last 50 years long term variability of snow cover over the qinghai xizang tibetan plateau qxp is characterized by large interannual variability superimposed on a continuously increasing trend glacier changes in western china vary remarkably in different regions although in most mountains the glaciers display a retreating trend 80 or have even vanished some glaciers 20 are still advancing frozen ground including permafrost has experienced a rapid decay since the 1980s and these changes are occurring both in the qxp and in the cold regions of north china sea ice areas in the bohai and north yellow seas have been shrinking since the 1970s interannual variations possibly relate to the solar cyles and sea ice extent extremes relate to el nino southern oscillation enso events the freeze up and break up dates of river ice in north china in the 1990s are on average 1 6 days later and 1 3 days earlier respectively than the 1950s 1990 mean frozen duration and the maximum thickness of river ice are respectively 4 10 days shorter and 0 06 0 21 cm thinner in the 1990s than the average cryosphere the cryosphere in china is mainly located in the qinghai xizang tibetan plateau hereafter qxp the eastern tien shan the altai shan the east pamirs and northeast china the total number of glaciers in china is 46 298 with a total area of 59 406 km 2 and an ice volume of 5590 km 3 the permafrost and the seasonally frozen ground sfg cover an area of 1 49 10 6 and 5 28 10 6 km 2 accounting for 11 5 and 55 of chinese land territory respectively the snow covered area in china is around 9 0 10 6 km 2 and of this an area over 4 8 10 6 km 2 consists of unstable snow cover duration 60 days is mainly located in the qxp north xinjiang including the tien shan and the inner mongolia northeast china hereafter im nec regions the mean snow cover areas of these three regions are 2 3 10 6 0 5 10 6 and 1 4 10 6 km 2 respectively seasonal sea ice forms in the bohai sea and in the northern yellow sea of china sea ice forms in mid to late november reaches its

the 2008 09 surge of central yulinchuan glacier northern tibetan plateau as monitored by remote sensing the 2008 09 surge of central yulinchuan glacier cyg on the northwestern slope of muztag mountain tibetan plateau is studied based on satellite remote sensing the widely used cross correlation feature tracking method was used to collect satellite image control points and validate their geometric accuracies as well as to derive glacier surface velocity changes in glacier length and area were also retrieved results show that the surge of cyg initiated in may 2008 and terminated in july 2009 two diffluent glacier termini advanced 590 26 m 5 1 0 2 of the 2004 length and 182 26 m 1 8 0 3 respectively and glacier area increased by similar to 1 41 0 11 km 2 4 6 0 4 of the 2004 area during this period the most significant surge period was october 2008 to march 2009 when most of the terminus advances and area increases occurred the glacier surface drastically crevassed during this time as much as 1657 297 m of horizontal surface displacements were produced by surge ice and maximum surface speed reached 13 1 5 m d 1 results of transverse and longitudinal velocity profiles revealed two surge waves during this surge of cyg

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

gross structure of a fault during its formation process in westerly granite abstract we investigated the gross structure of a fault in three dimensions during its formation process the observed sample was westerly granite recovered from compression after peak stress but before dynamic rupture the sample was infused with a fluorescent resin mechanically stripped then observed with a stereo microscope under uv light the main fault plane was found to be macroscopically elliptical and the fault trace on each polished surface was identical to that detected by x ray ct scanning evidence suggests that the fault plane widened its cracked zone as it grew the gross structures of the fault system such as a step over structure and sub faults parallel to the main fault were also detected we conclude that the step over structure was formed during the fault formation process

glacigenic sediments on a passive continental margin as exemplified by the barents sea abstract reflection seismics data borehole data and gravity cores have been used to map the sedimentary facies of the epicontinental southwestern barents sea its continental margin and adjacent coastal areas an upper unconformity with a glacially eroded morphology extends over most of the continental shelf up to 300 m of stratiform glacigenic sediments overlie this unconformity these sediments can be grouped into seismic units which are separated by smooth or irregular erosional surfaces each sequence may be up to 150 m thick normally with a lateral extent of 100 300 km three dominant seismic signatures may be discerned semi transparent stratified and chaotic reflection patterns these sediments are partly glacifluvial in origin but on the whole they represent more or less tectonized glacimarine deposits the deeper troughs on the continental shelf contain an undeformed postglacial glacimarine marine trough fill the greatest thickness up to 1000 m of glacigenic sediments occurs at the shelf break and below the upper slope the depocentres are situated at trough mouth fans the sediments comprise several prograding sequences with a complex sigmoid oblique character indicating alternating upbuilding and depositional bypass erosion in the topset segment small and large scale slide scars are observed on the upper slope and debris lobes on the lower slope a marked progradation seems to have occurred during the plio pleistocene glacial periods this progradation also resulted in an unstable slope with various types of sediment gravity flows currents flowing along the slope were established during interglacials and gullying by cold dense shelf water and downslope transport occurred maximum net sedimentation rates are 0 2 m ka continental slope 0 4 m ka shelf break 0 1 m ka shelf stratiform diamictons 1 m ka shelf trough fills and 60 m ka fjord trough fills

slope failure dynamics and impacts from seafloor and shallow sub seafloor geophysical data case studies from the costa project holocene and slightly pre holocene submarine landslide are found both in high latitude glacial dominated margins and in lower latitude river dominated margins this paper constitutes a major assessment on some of the best studied submarine instabilities in the world we review and update from original data and literature reports the current state of knowledge of storegga traenadjupet and finneidfjord slides from the mid norwegian margin afen slide from the faeroe shetland channel big 95 slide and central adriatic deformation belt cadeb from continental slope and inner continental shelf settings off the ebro and po rivers in the mediterranean sea canary slide west of the westernmost youngest canary islands and gebra slide off the northern tip of the antarctic peninsula in the southern hemisphere i e those studied in the continental slope stability costa project the investigated slides range in size from the gigantic 90 000 km2 and almost 3000 km3 storegga slide to the tiny 1 km2 and 0 001 km3 finneidfjord slide not only do individual submarine landslides rarely involve processes precisely fitting with pre established categories mostly based on subaerial research but also they display complex mechanical behaviors within the elastic and plastic fields individual events can involve simultaneous or successive vertical to translational movements including block detachment block gliding debris flow mud flow and turbidity currents the need for an in depth revision of the classification criteria and eventually for a new classification system based on the new imaging capabilities provided by modern techniques is more than obvious we suggest a new system which for the moment is restricted to debris flows and debris avalanches volume calculation methods are critically reviewed and the relations between some key geomorphic parameters are established for the selected slides the assumed volume missing from scar areas does not necessarily match the actual volume of sediment remobilised by an individual event since in situ sediment can be remoulded and eventually incorporated during the slide downslope journey cadeb a shore parallel prodelta detached from its source is the exception to the good correlation found between across slope width and alongslope length with slide area height drop measured from the headwall upper rim to its foot correlates with the debris deposit maximum thickness unless the slide moves into restricted areas which prevent farther forward expansion of the deposit such as gebra and big 95 in such cases over thickened deposits are found a particularly loose and fluid behavior can be deduced for slides showing an over thinned character such as the canary slide that traveled 600 km scar areas and slip planes have been investigated with particular emphasis although slide headwalls might present locally steep gradients up to 23 for storegga slide the slope gradients of both the failed segment margins and the main slip planes are very low max 2 and usually around 1 and less an exception is the finneidfjord slide 20 5 that occurred in 1996 because of a combination of climatic and anthropogenic factors leading to excess pore pressure and failure mechanically distinct low permeable clayey weak layers often correspond to slip planes beyond the slide headwall since not only formation of these weak layers but also sedimentation rates are climatically controlled we can state that slide pre conditioning is climatically driven too run out distances reflect the degree of disintegration of the failed mass of sediment the total volume of initially failed material and transport mechanisms including hydroplanning commonly specific run outs could be attributed to distinct elements such as cohesive blocks and looser matrix as nicely illustrated by the big 95 slide total run outs usually correspond to matrix run outs since the coarser elements tend to rest at shorter distances outrunner blocks are finally a very common feature proving the ability of those elements to glide over long distances with independence of the rest of the failed mass in addition to pre conditioning factors related to geological setting and sedimentation conditions a final trigger is required for submarine landslides to take place which is most often assumed to be an earthquake in high latitude margins earthquake magnitude intensification because of post glacial isostatic rebound has likely played a major role in triggering landslides although it cannot be totally ruled out there is little proof at least amongst the costa slides that gas hydrate destabilisation or other processes linked to the presence of shallow gas have acted as final triggers

structure and mechanics of the hayward rodgers creek fault step over san francisco bay california a dilatational step over between the right lateral hayward and rodgers creek faults lies beneath san pablo bay in the san francisco bay area a key seismic hazard issue is whether an earthquake on one of the faults could rupture through the step over enhancing its maximum possible magnitude if ruptures are terminated at the step over then another important issue is how strain transfers through the step we developed a combined seismic reflection and refraction cross section across south san pablo bay and found that the hayward and rodgers creek faults converge to within 4 km of one another near the surface about 2 km closer than previously thought interpretation of potential field data from san pablo bay indicated a low likelihood of strike slip transfer faults connecting the hayward and rodgers creek faults numerical simulations suggest that it is possible for a rupture to jump across a 4 km fault gap although special stressing conditions are probably required e g harris and day 1993 1999 slip on the hayward and rodgers creek faults is building an extensional pull apart basin that could contain hazardous normal faults we investigated strain in the pull apart using a finite element model and calculated a 0 02 mpa yr differential stressing rate in the step over on a least principal stress orientation nearly parallel to the strike slip faults where they overlap a 1 to 10 mpa stress drop extensional earthquake is expected on normal faults oriented per pendicular to the strike slip faults every 50 500 years the last such earthquake might have been the 1898 m 6 0 6 5 shock in san pablo bay that apparently pro duced a small tsunami historical hydrographic surveys gathered before and after 1898 indicate abnormal subsidence of the bay floor within the step over possibly related to the earthquake we used a hydrodynamic model to show that a dip slip mechanism in north san pablo bay is the most likely 1898 rupture scenario to have caused the tsunami while we find no strike slip transfer fault between the hayward and rodgers creek faults a normal fault link could enable through going segmented rupture of both strike slip faults and may pose an independent hazard of m 6 earthquakes like the 1898 event

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

decadal changes in glacier parameters in the cordillera blanca peru derived from remote sensing we present spatial patterns of glacier fluctuations from the cordillera blanca peru glacier area terminus elevations median elevations and hypsography at decadal timescales derived from 1970 aerial photography 2003 spot5 satellite data geographic information systems gis and statistical analyses we derived new glacier outlines from the 2003 spot images and ingested them in the global land and ice measurements from space glims glacier database we examined changes in glacier area on the eastern and western side of the cordillera in relation to topographic and climate variables temperature and precipitation results include 1 an estimated glacierized area of 569 6 21 km 2 in 2003 2 an overall loss in glacierized area of 22 4 from 1970 to 2003 3 an average rise in glacier terminus elevations by 113 m and an average rise in the median elevation of glaciers by 66 m showing a shift of ice to higher elevations especially on the eastern side of the cordillera and 4 an increase in the number of glaciers which indicates disintegration of ice bodies annual air temperature showed a significant upward trend in the last 30 years with larger temperature increases at lower elevations there was a slight but not significant decrease in precipitation our results are consistent with glacier retreat and warming trends noted in the last three decades in the tropics

responses of various sized alpine glaciers and runoff to climatic change this paper presents a glacier ice flow model that simulates changes to alpine glaciers of various sizes and their runoff response to climate change in the yili river basin in the tien shall mountains northwestern china it is suggested that the sensitivity of glaciers to climatic change is determined by glacier size the change in glacial runoff does not keep pace with climactic change as climate warms and glaciers retreat the glacier runoff tends to increase and then decrease the runoff peak and its timing depend not only on glacier size but also on the rate of air temperature rise

changes of glaciers and glacial lakes implying corridor barrier effects and climate change in the hengduan shan southeastern tibetan plateau changes of glaciers and glacial lakes and their causes were examined in the hengduan shan from 1990 to 2014 based on landsat tm etm oli images a total glacier area of 1298 8 62 1 km 2 and glacial lake area of 255 8 31 6 km were inventoried in 2014 the area of glaciers declined at an average rate of 0 40 0 26 a 1 while glacial lakes expanded at average rate of 0 12 0 03 a 1 over the past 24 years these changes probably resulted from an observable temperature increase and slight precipitation increase a corridor barrier effect formed by the longitudinal range gorge terrain may have had major impacts on the distributions and changes of glaciers and glacial lakes the ningjing yunling shan where glaciers and glacial lakes are sparsely distributed are an important geographic transition line in the hengduan shan because of the barrier effect of the mountain ranges against moisture from the southwest in contrast between the south and north there were small differences with respect to the distributions and changes of glaciers and glacial lakes owing to a north south corridor effect for water and heat transport and diffusion through the longitudinal gorges in the hengduan shan

reconstruction of the west antarctic ice sheet in pine island bay during the last glacial maximum and its subsequent retreat history abstract marine geological and geophysical studies were conducted to determine the late quaternary glacial history of the west antarctic ice sheet in pine island bay antarctica the data set includes sea floor imagery in the form of multibeam swath bathymetry and deep tow side scan sonar surveys distribution of sedimentary deposits and basal surface conditions are revealed through intermediate resolution seismic data and chirp 3 5 khz sub bottom profiles sedimentary deposits were sampled with piston cores and calcareous material was dated using ams radiocarbon techniques results from the study indicate the ice sheet was grounded on the outer shelf during its maximum extent sometime in the past thick ice flowing slowly and resting on crystalline bedrock was influenced by significant amounts of subglacial meltwater on the inner shelf thinner but more rapidly flowing ice characterized the seaward extent of the ice sheet which was grounded on a sedimentary substrate deglaciation occurred in two phases beginning soon after the last glacial maximum the outer most extension of the ice sheet retreated gradually pausing on a bathymetric high on the middle shelf by 16 000 14c years ago between 16 000 and 12 000 14c years ago ice sheet retreat resumed and may have proceeded rapidly to reach a present day position by 10 000 14c years ago

glacier changes on the tibetan plateau derived from landsat imagery mid 1970s 2000 13 glacier area changes on the tibetan plateau were studied in different drainage basins based on landsat satellite images from three epochs 263 in the mid 1970s 150 in 1999 2002 and 148 in 2013 14 three mosaics m1976 m2001 and m2013 with minimal cloud and snow cover were constructed and the uncertainty due to each epoch having a finite span was accounted for glacier outlines tpg1976 tpg2001 and tpg2013 were digitized manually with guidance from the srtm dem v4 1 and google earth imagery to achieve complete multi temporal coverage in a reasonable time only debris free ice was delineated area mapping uncertainty was evaluated at three study sites mount qomolangma everest mount naimona nyi mount geladandong where the largest differences between present and earlier measurements were within similar to 4 area differences with previous inventories ranged from 19 6 tpg1976 minus the first chinese glacier inventory to 3 6 and 1 1 tpg2013 and tpg2001 respectively minus the second chinese glacier inventory while the difference tpg2001 minus the gamdam glacier inventory was 10 4 glacier area on the plateau decreased from 44 366 2827 km 2 1 7 of the study area in the 1970s to 42 210 1621 km2 in 2001 and 41 137 1616 km2 in 2013 shrinkage was faster in external drainage basins of the southeast than in the interior basins of the northwest from a maximum of 0 43 a 1 1 60 a 1 during 19942013 in the mekong catchment down to a minimum of 0 12 a 1 in the tarim interior drainage

the depositional pattern and distribution of glacial interglacial sequences on the antarctic peninsula pacific margin the outer shelf on the antarctic peninsula pacific margin south of 63 30 s is underlain by pliocene pleistocene prograding sequences which have been produced mainly by the action of ice sheets grounded out to the shelf edge at times of glacial maximum most sediment in these sequences has probably been transported to the margin in a deforming basal till which implies deposition on a broad front a line source a representative prograding sequence mapped across an extensive network of multichannel seismic reflection lines has an elongate depocentre on the upper palaeoslope which is consistent with the grounded ice sheet model however it is likely that each sequence recognized on existing multichannel seismic data represents several ice advances depth to surface maps reveal a broad variation along the margin in the amount of progradation reflecting differences in sediment supply the pattern of progradation and the bathymetry of the outer shelf suggest that the main depocentre in the area studied was fed by an ice stream at times of glacial maximum seismic lines across the margin farther to the southwest indicate the existence of other depocentres several broad depositional lobes have probably coalesced to form the extensive outer shelf the present continental slope is smooth and steep and is not cut by major canyons a downslope change in seismic facies and scouring on the uppermost rise probably reflect downslope transitions from slumps to debris flows to turbidity currents these processes are likely to be most active at times of glacial maximum deep drilling data indicate that the rise sediments consist mainly of terrigenous turbidite and ice rafted detritus a marked upward change in seismic facies on the continental rise indicates a change to a higher energy sedimentary regime and appears to correlate with the start of glacial progradation on the shelf

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

reconstruction of little ice age glacier area and equilibrium line attitudes in the central and western himalaya abstract glacial changes during the little ice age lia in the himalayan mountains are important for understanding changes in the monsoonal and westerly climate of the so called the third pole however knowledge of these changes and their dynamics remains limited because of the region s geographical inaccessibility in addition to geopolitical reasons in this study we used high resolution three dimensional images from google earth to identify lateral and terminal moraines as delineators of paleoglacier boundaries and mapped the boundaries of both modern and lia glaciers arcgis 9 3 software was applied to map data and to calculate glacier lengths and areas modern glacier surface elevation data were derived from srtm shuttle radar topography mission records three methods the toe to headwall altitude ratio thar the toe to summit altitude method tsam and the toe to ridge altitude method tram were used to estimate equilibrium line altitude ela the transient snowlines tsl of ninety one modern glaciers were acquired using landsat 8 oli images in late summer to evaluate the reliability of the calculated elas our results showed that the total length and total area of two hundred and twenty glaciers in the central and western himalaya cwh had decreased respectively by 35 and 31 since the lia the tram method was the preferred method for the reconstruction of elas the mean depression of elas from the lia to the first decade of the 21st century as reconstructed using the tram method was 123 m the ela depression and rate of change of glacier length and glacier area displayed generally increasing trends from west to east along the central and western himalaya suggesting that the moisture was most likely transported from an easterly direction these changes were more intensive on southern than northern slopes suggesting that southerly and westerly precipitation likely increased over the same period we speculated that the cwh had been influenced by both the indian summer monsoon ism and westerlies since the lia ism moisture as in modern times was the main factor controlling the distribution of glaciers during the lia further precipitation carried by the westerlies likely intensified along southerly pathways along the cwh during the lia

differences and cause analysis of changes in lakes of different supply types in the north western tibetan plateau most lakes of the tibetan plateau tp were experiencing quick expansion in recent decades a detailed study on the changes in lakes of different supply types will help to understand the cause of the changes by analysing area change of thirty four lakes and water level change of eight lakes in the northwestern tp all lakes are classified into three types non glacier fed lakes upstream lakes and glacier fed lakes the glacier fed lakes are separated into glacier fed p1 quick expansion region and glacier fed p2 slow expansion region combining the changes in precipitation temperature and evaporation less precipitation may be the main reason for lake shrinkage from 1976 to 1996 and quickly increasing precipitation led to the lakes expansion from 1996 to 2000 however after 2000 upstream lakes remained in a stable state with slight variation non glacier fed lakes and glacier fed p2 lakes exhibited a slightly increasing rate with high precipitation and high evaporation and glacier fed p1 lakes still expanded quickly based on the assumption of same precipitation and evaporation glacial meltwater may make an important contribution 52 to the increase in water storage of bangdag co and meima co the results suggest that glacial meltwater augments the increased rate of glacier fed p2 lakes and plays a much more important role in the expansion of glacier fed p1 lakes compared to other lakes

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

impacts of bottom corrugations on a dense antarctic outflow nw ross sea 1 prominent seabed corrugations axially oriented roughly down slope are present along the antarctic continental slope we use analytical and numerical model results to assess the potential impact of these corrugations on outflows of dense shelf water that contribute to antarctic bottom water down slope flow increases with increasing corrugation height and varies with along slope wavelength for parameters appropriate to the northwest ross sea where heights and wavelengths are 10 20 m and 1 5 km respectively we estimate that the corrugations increase the down slope transport of dense water relative to the smooth bottom case by 13 corrugations enhance entrainment and reduce along slope speed of the dense outflow larger amplitude corrugations 100 m observed in other regions may impact outflows elsewhere around the poorly mapped antarctic continental margin our results emphasize the need to consider small scale local topography when modeling dense outflows

investigating the crustal structure of a strike slip step over zone along the great glen fault strike slip step overs and bends are regions of anomalous deformation that may yield clues to the mechanical behavior of the earth s crust experimental reprocessing of a marine deep seismic reflection profile cutting across an 35 km wide right stepping step over developed on the great glen fault system north of the inner moray firth basin east of northwest highlands scotland reveals a restricted zone of prominent reflections and diffractions beginning at 7 8 km depth continuing as deep as the interpreted moho discontinuity at 26 27 km geological interpretation of this zone suggests a concentration of possible diffractors marking sharp structural disruption underlain by a 12 km thick layer of subhorizontal and moderately dipping reflectors that dominates the lower crust in the step over region the known kinematic history of the great glen fault system together with the observed direction of the step over implies that a zone of contraction would have formed within the step over during early caledonian sinistral strike slip the seismic reflection structure can be interpreted as developing by deformation associated with contraction and possible block rotation between the two fault segments such that the diffractive zone represents steep structure in a near vertical zone of strike slip which passes deeper into a layer of low angle dipping thrusts or shear zones the results of this study are consistent with a concept of mechanical detachment in the middle crust as documented for areas of contraction along active strike slip faults

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out

a new light on arresting mechanism of dynamic earthquake faulting classic analyses have shown that dynamic growth of a shear crack cannot be arrested in a uniformly stressed elastic medium with homogeneously distributed fracture strengths this leads to a general supposition that earthquake rupture growth is arrested by inhomogeneities in the distributions of strengths or stresses we propose a novel idea for arresting mechanism of dynamic crack growth in the simulation with no constraints on the crack geometry our analysis shows that the arresting occurs spontaneously soon after crack bending even in the homogeneous medium and that inhomogeneities are indispensable not for stopping crack growth but for its promotion