interpreting rockfall activity on an outcrop talus slope system in the southern japanese alps using an integrated survey approach abstract understanding relationships between meteorological conditions and rockfall activity is important for the management of rockfall risks as well as for the estimation of future rockfall activity under climate change seasonal activity of rockfall on talus slopes depends on the actual triggers of rockfall which in turn may vary as well between outcrops because of different rockfall sources and the influence of topography in this study we interpret spatial and temporal variations in rockfall activity and related sediment transfer processes in an outcrop talus slope system in central japan through monitoring using rock temperature and moisture sensors sediment traps and time lapse cameras in addition tree ring analysis has been added to understand possible changes of rockfall activity over longer time periods results suggest that the frequency of grouped gravel transport i e soil creep was higher than that of individual transport i e rockfall and dry ravel on the talus slope whereas rockfall likely is the predominant process from the outcrops observations from sediment traps showed that coarse gravel is characterized by higher bounce heights and that it travelled longer distances than fine gravel rockfall from the outcrops was most active during dormancy of trees which locally lasts from autumn to early spring and can be related to freeze thaw cycles in contrast rockfall and other sediment transfer processes were monitored on the talus slope all year round secondary movement of gravels on the talus slope such as soil creep during rainfall events likely triggers rockfall during times when the outcrops are not producing rockfall i e from late spring to summer consequently our results suggest that the spatio temporal rockfall activity varies substantially between outcrops and talus slopes and that differences in process behavior should be taken into account in future disaster mitigation measures

three dimensional surface velocities of storstrommen glacier greenland derived from radar interferometry and ice sounding radar measurements non steady state vertical velocities of up to 5 m y 1 exceed the vertical surface parallel flow components over much of the ablation area of storstrommen a large outlet glacier from the east greenland ice sheet neglecting a contribution to the vertical velocity of this magnitude results in substantial errors up to 20 also on the south north component of horizontal velocities derived by satellite synthetic aperture radar interferometry insar measurements in many glacier environments the steady state vertical velocity component required to balance the annual ablation rate is 5 to 10 m y 1 or more this indicates that the surface parallel flow assumption may be problematic also for glaciers in steady state here we derive the three dimensional surface velocity distribution of storstrommen by using the principle of mass conservation to combine insar measurements from ascending and descending satellite tracks with airborne ice sounding radar measurement of ice thickness the results are compared to insar velocities previously derived by using the assumption of surface parallel flow and to velocities obtained by inin situ gps measurements the velocities derived by using the principle of mass conservation are in better agreement with the gps velocities than the previously calculated velocities derived with the assumption of surface parallel flow

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

growth of greenland ice sheet interpretation an observed 0 23 m year thickening of the greenland ice sheet indicates a 25 to 45 excess ice accumulation over the amount required to balance the outward ice flow the implied global sea level depletion is 0 2 to 0 4 mm year depending on whether the thickening is only recent 5 to 10 years or longer term 100 years if there is a similar imbalance in the northern 60 of the ice sheet area the depletion is 0 35 to 0 7 mm year increasing ice thickness suggests that the precipitation is higher than the long term average higher precipitation may be a characteristic of warmer climates in polar regions

time variable gravity observations of ice sheet mass balance precision and limitations of the grace satellite data time variable gravity data from the gravity recovery and climate experiment grace mission have been available since 2002 to estimate the mass balance of the greenland and antarctic ice sheets we analyze current progress and uncertainties in grace estimates of ice sheet mass balance we discuss the impacts of errors associated with spherical harmonic truncation spatial averaging temporal sampling and leakage from other time dependent signals e g glacial isostatic adjustment gia the largest sources of error for antarctica are the gia correction the omission of l 1 terms nontidal changes in ocean mass and measurement errors for greenland the errors come mostly from the uncertainty in the scaling factor using release 5 0 rl05 grace fields for january 2003 through november 2012 we find a mass change of 258 41 gt yr for greenland with an acceleration of 31 6 gt yr2 and a loss that migrated clockwise around the ice sheet margin to progressively affect the entire periphery for antarctica we report changes of 83 49 and 147 80 gt yr for two gia models with an acceleration of 12 9 gt yr2 and a dominance from the southeast pacific sector of west antarctica and the antarctic peninsula

deformation in the vicinity of ice divides calculs numeriques aux elements finis de la variation de la vitesse horizontale avec la profondeur au voisinage d une difference de la glace symetrique isotherme et ou glissement sur un lit plat

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

anisotropy of electrical conductivity of the excavation damaged zone in the mont terri underground rock laboratory summary electrical resistivity measurements were performed to characterize the anisotropy of electrical resistivity of the excavation damaged zone edz at the end face of a gallery in the opalinus clay of the mont terri underground rock laboratory url the data were acquired with a combination of square arrays in 18 zones on the gallery s face and in two series of four boreholes perpendicular to the face each data set is independently inverted using simulated annealing to recover the resistivity tensor both the stability and the non uniqueness of the inverse problem are discussed with synthetic examples the inversion of the data shows that the face is split in two domains separated by a tectonic fracture with different resistivity values but with a common orientation the direction of the maximum resistivity is found perpendicular to the bedding plane and the direction of minimum resistivity is contained in the face s plane these results show that the geo electrical structure of the edz is controlled by a combination of effects due to tectonics stratigraphy and recent fracturing produced by the excavation of the gallery

increasing rates of ice mass loss from the greenland and antarctic ice sheets revealed by grace 1 we use monthly measurements of time variable gravity from the grace gravity recovery and climate experiment satellite gravity mission to determine the ice mass loss for the greenland and antarctic ice sheets during the period between april 2002 and february 2009 we find that during this time period the mass loss of the ice sheets is not a constant but accelerating with time i e that the grace observations are better represented by a quadratic trend than by a linear one implying that the ice sheets contribution to sea level becomes larger with time in greenland the mass loss increased from 137 gt yr in 2002 2003 to 286 gt yr in 2007 2009 i e an acceleration of 30 11 gt yr2 in 2002 2009 in antarctica the mass loss increased from 104 gt yr in 2002 2006 to 246 gt yr in 2006 2009 i e an acceleration of 26 14 gt yr2 in 2002 2009 the observed acceleration in ice sheet mass loss helps reconcile grace ice mass estimates obtained for different time periods

recent large increases in freshwater fluxes from greenland into the north atlantic 1 freshwater fw fluxes from river runoff and precipitation minus evaporation for the pan arctic seas are relatively well documented and prescribed in ocean gcms fluxes from greenland on the other hand are generally ignored altogether despite their potential impacts on ocean circulation and marine biology here we present a reconstruction of the spatially distributed fw flux from greenland for 1958 2010 we find a modest increase into the arctic ocean during this period fluxes into the irminger basin however have increased by fifty percent 6 3 0 5 km3 yr 2 in less than twenty years this greatly exceeds previous estimates for the ice sheet as a whole the rate of increase since 1992 is 16 9 1 8 km3 yr 2 the cumulative fw anomaly since 1995 is 3200 358 km3 which is about a third of the magnitude of the great salinity anomaly gsa of the 1970s if this trend continues into the future the anomaly will exceed that of the gsa by about 2025

evaluating the role of climate cooling in iceberg production and the heinrich events bond et al 1 recently presented evidence for the frequent occurrence in the pleistocene epoch of periods of massive iceberg discharge into the north atlantic ocean heinrich events each lasting a few thousand years the cause of these events is uncertain but one possibility1 is repeated advances of the laurentide ice sheet during episodes of cooler climate here i examine this idea using a model of the laurentide ice sheet driven by orbitally forced variations in insolation with and without three additional 3 000 yr long cooling episodes imposed just before the occurrence of the three most recent heinrich events hi h2 and h3 in the model the cooling event preceding hi when the climate was relatively warm and deglaciation was about to begin led to increased calving but those preceding h2 and h3 which occurred during the last ice age when the climate was very cold led to reduced iceberg calving it thus seems unlikely that the heinrich events generally reflect a direct response of the laurentide ice sheet to climate cooling

mass balance and surface movement of the greenland ice sheet at summit central greenland during the grip deep drilling in central greenland the ice sheet topography and surface movement at summit has been mapped with gps measurements of the surface velocity are presented for a strain net consisting of 13 poles at distances of 25 60 km from the grip site some results are the grip site is located approximately 2 km nw of the topographic summit the surface velocity at the gisp 2 site is 1 7 m yr in the w direction the present mass balance at summit is calculated to be 0 03 0 04 m yr i e close to steady state this result is the best now available for summit a small thinning rate might be a transient response of the greenland ice sheet due to the temperature increase at the wisconsin holocene transition

mass balance of the greenland ice sheet at dye 3 the mass balance of the greenland ice sheet a t dye 3 is estimated on the basis of 0 bserva tions of ice thickness accumulation rate surface velocities and surface strain rates the calculations indicate a rate of increase of surface elevation of 3 cm year with 95 confidence limits of 3 cm year and 9 cm year previous estimates of the mass balance of the greenland ice sheet by the same method reported large imbalances these are most probably due to lack of precise data and the use of quantities measured at the surface as representative of depth averaged quantities the most reliable observations indicate that the interior regions of the greenland ice sheet are at present thickening at a rate of a few centimetres per year a contributing cause for this may be the slow thinning of a bottom layer of relatively soft wisconsin ice resume bilan de masse de l lndlandsis groenlandais a dye 3 le bilan de masse est estime it partir des mesures d epaisseur taux d accumulation vitesses et vitesses de deformation superficielles le calcul don ne un epalss lssement de 3 cm an 1 avec un intervalle de confiance au seuil de 95 allant de 3 cm an 1 it 9 cm an i les estimations anterieures du bilan de l lndlandsis obtenues par la meme methode sont examinees on en deduit que les valeurs de bilan tres eloignees de l equilibre sont certainement dues au manque de donnees preclses et ou a i utilisation de donnees superficielles comme valeurs moyennes sur une

history of the greenland ice sheet paleoclimatic insights abstract paleoclimatic records show that the greenland ice sheet consistently has lost mass in response to warming and grown in response to cooling such changes have occurred even at times of slow or zero sea level change so changing sea level cannot have been the cause of at least some of the ice sheet changes in contrast there are no documented major ice sheet changes that occurred independent of temperature changes moreover snowfall has increased when the climate warmed but the ice sheet lost mass nonetheless increased accumulation in the ice sheet s center has not been sufficient to counteract increased melting and flow near the edges most documented forcings and ice sheet responses spanned periods of several thousand years but limited data also show rapid response to rapid forcings in particular regions near the ice margin have responded within decades however major changes of central regions of the ice sheet are thought to require centuries to millennia the paleoclimatic record does not yet strongly constrain how rapidly a major shrinkage or nearly complete loss of the ice sheet could occur the evidence suggests nearly total ice sheet loss may result from warming of more than a few degrees above mean 20th century values but this threshold is poorly defined perhaps as little as 2 c or more than 7 c paleoclimatic records are sufficiently sketchy that the ice sheet may have grown temporarily in response to warming or changes may have been induced by factors other than temperature without having been recorded

improved ice loss estimate of the northwestern greenland ice sheet 1 we estimate ice volume change rates in the northwest greenland drainage basin during 2003 2009 using ice cloud and land elevation satellite icesat laser altimeter data elevation changes are often reported to be largest near the frontal portion of outlet glaciers to improve the volume change estimate we supplement the icesat data with altimeter surveys from nasa s airborne topographic mapper from 2002 to 2010 and nasa s land vegetation and ice sensor from 2010 the airborne data are mainly concentrated along the ice margin and thus have a significant impact on the estimate of the volume change our results show that adding airborne topographic mapper and land vegetation and ice sensor data to the icesat data increases the catchment wide estimate of ice volume loss by 11 mainly due to an improved volume loss estimate along the ice sheet margin furthermore our results show a significant acceleration in mass loss at elevations above 1200m both the improved mass loss estimate along the ice sheet margin and the acceleration at higher elevations have implications for predictions of the elastic adjustment of the lithosphere caused by present day ice mass changes our study shows that the use of icesat data alone to predict elastic uplift rates biases the predicted rates by several millimeters per year at gps locations along the northwestern coast

determination of the flow properties at dye 3 south greenland by bore hole tilting measurements and perturbation modelling les donnees issues d inclinometrie a dye 3 groenland rendent possible le calcul du parametre de la loi de fluage en fonction de la profondeur ce parametre montre une importante variation lors de la transition holocene pleistocene en triplant sa valeur pour la glace formee au cours de la derniere glaciation les parametres d ecoulement et la topographie du lit sont utilises dans un modele de perturbation pour calculer les ondulations de surface et les taux de deformation

ice flow dynamics of the greenland ice sheet from sar interferometry synthetic aperture radar sar interferograms produced from esa s ers 1 satellite provide the first synoptic view of ice flow dynamics of the western sector of the greenland ice sheet glacial motion is detected in the radar ranging direction at millimetric scales across a complete sequence of snow accumulation and melting regimes despite significant variations in their radar scattering properties ice flow evolves from a slow regular motion at the higher elevations at lower elevations motion is strongly convoluted by meter scale undulations in surface topography which have a unique interferometric signature that enables a novel approach for retrieving flow direction inferred flow directions combined with surface displacements in the radar ranging direction yield ice velocity estimates that are within 6 of in situ measurements gathered along a 40 km survey line application of repeat pass sar interferometry to the entire greenland ice sheet should enable precise mapping of its ice flow dynamics at an unprecedented level of spatial detail

greenland ice sheet mass balance reconstruction part iii marine ice loss and total mass balance 1840 2010 abstractgreenland ice sheet mass loss to the marine environment occurs by some combination of iceberg calving and underwater melting referred to here as marine ice loss lm this study quantifies the relation between lm and meltwater runoff r at the ice sheet scale a theoretical basis is presented explaining how variability in r can be expected to govern much of the lm variability over annual to decadal time scales it is found that r enhances lm through three processes 1 increased glacier discharge by ice warming softening and basal lubrication sliding 2 increased calving susceptibility through undercutting glacier front geometry and reducing ice integrity and 3 increased underwater melting from forcing marine convection applying a semiempirical lm f r parameterization to a surface mass balance reconstruction enables total ice sheet mass budget closure over the 1840 2010 period the estimated cumulative 171 yr net ice sheet sea level contribution is 25 10 mm the rise punctuated by periods

reaction of the accumulation zone portions of glaciers to climatic change the response of the accumulation regions of glaciers to changes in accumulation rate and in surface temperature is calculated by considering perturbations to the ice flow the analysis is limited to glaciers in which flow is dominated by internal shear and not by bottom sliding and for which flowlines are geographically parallel in general glaciers begin to alter thickness immediately after a change in accumulation rate but the effect of a change in surface temperature is delayed by the time for this temperature change to penetrate to depth in the glacier a warming leads to glacial thinning the amount and timing of the response is very different for different glaciers characteristic times are on the order of tens of years for mountain glaciers and tens of thousands of years for the east antarctic ice sheet as an example the theory is applied to the ice sheet near byrd station antarctica for hypothetical changes in surface accumulation rate and temperature rates and amounts of thickness change are calculated and it is found that the measured thinning is probably too fast to have been caused by climatic variation alone the effects of hypothetical climatic variations on the depth age and depth temperature relationships through the ice sheet are also calculated it is hoped that the theory will prove valuable in the interpretation of future drill hole results