timing and origin of recent regional ice mass loss in greenland within the last decade the greenland ice sheet gris and its surroundings have experienced record high surface temperatures mote 2007 box et al 2010 ice sheet melt extent fettweis et al 2011 and record low summer sea ice extent nghiem et al 2007 using three independent data sets we derive for the first time consistent ice mass trends and temporal variations within seven major drainage basins from gravity fields from the gravity recovery and climate experiment grace tapley et al 2004 surface ice velocities from inteferometric synthetic aperture radar insar rignot and kanagaratnam 2006 together with output of the regional atmospheric climate modelling racmo2 gr ettema et al 2009 and surface elevation changes from the ice cloud and land elevation satellite icesat sorensen et al 2011 we show that changing ice discharge d surface melting and subsequent run off m r and precipitation p all contribute in a complex and regionally variable interplay to the increasingly negative mass balance of the gris observed within the last decade interannual variability in p along the northwest and west coasts of the gris largely explains the apparent regional mass loss increase during 2002 2010 and obscures increasing m r and d since the 1990s in winter 2002 2003 and 2008 2009 accumulation anomalies in the east and southeast temporarily outweighed the losses by m r and d that prevailed during 2003 2008 and after summer 2010 overall for all basins of the gris the decadal variability of anomalies in p m r and d between 1958 and 2010 w r t 1961 1990 was significantly exceeded by the regional trends observed during the grace period 2002 2011 2012 elsevier b v

glacier velocities and dynamic ice discharge from the queen elizabeth islands nunavut canada recent studies indicate an increase in glacier mass loss from the canadian arctic archipelago as a result of warmer summer air temperatures however no complete assessment of dynamic ice discharge from this region exists we present the first complete surface velocity mapping of all ice masses in the queen elizabeth islands and show that these ice masses discharged 2 6 0 8 gt a 1 of ice to the oceans in winter 2012 approximately 50 of the dynamic discharge was channeled through non surge type trinity and wykeham glaciers alone dynamic discharge of the surge type mittie glacier varied from 0 90 0 09 gt a 1 during its 2003 surge to 0 02 0 02 gt a 1 during quiescence in 2012 highlighting the importance of surge type glaciers for interannual variability in regional mass loss queen elizabeth islands glaciers currently account for 7 5 of reported dynamic discharge from arctic ice masses outside greenland

methods for inferring regional surface mass anomalies from gravity recovery and climate experiment grace measurements of time variable gravity 1 the gravity recovery and climate experiment grace will deliver monthly averages of the spherical harmonic coefficients describing the earth s gravity field from which we expect to infer time variable changes in mass averaged over arbitrary regions having length scales of a few hundred kilometers and larger to accuracies of better than 1 cm of equivalent water thickness these data will be useful for examining changes in the distribution of water in the ocean in snow and ice on polar ice sheets and in continental water and snow storage we describe methods of extracting regional mass anomalies from grace gravity coefficients spatial averaging kernels were created to isolate the gravity signal of individual regions while simultaneously minimizing the effects of grace observational errors and contamination from surrounding glacial hydrological and oceanic gravity signals we then estimated the probable accuracy of averaging kernels for regions of arbitrary shape and size

hybrid inventory gravimetry and altimetry higa mass balance product for greenland and the canadian arctic abstract we present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery cryosphere attributed mass trends derived from satellite gravimetry and ice surface elevation trends derived from airborne and satellite altimetry we use this algorithm to assess mass balance across greenland and the canadian arctic over the sep 2003 to oct 2009 period at 26 km resolution we evaluate local algorithm inferred mass balance against forty in situ point observations this evaluation yields an rmse of 0 15 mwe a and highlights a paucity of in situ observations from regions of high dynamic mass loss and peripheral glaciers we assess mass losses of 212 67 gt a to the greenland ice sheet proper 38 11 gt a to peripheral glaciers in greenland and 42 11 gt a to glaciers in the canadian arctic these magnitudes of mass loss are dependent on the gravimetry derived spherical harmonic mass trend we invert we spatially partition the transient glacier continuity equation by differencing algorithm inferred mass balance from modeled surface mass balance in order to solve the horizontal divergence of ice flux as a residual this residual ice dynamic field infers flux divergence or submergent flow in the ice sheet accumulation area and at tidewater margins and flux convergence or emergent flow in land terminating ablation areas which is consistent with continuum mechanics theory

greenland ice sheet mass balance reconstruction part i net snow accumulation 1600 2009 ice core data are combined with regional atmospheric climate model version 2 racmo2 output 1958 2010 to develop a reconstruction of greenland ice sheet net snow accumulation rate at g spanning the years 1600 2009 regression parameters from regional climate model rcm output regressed on 86 ice cores are used with available cores in a given year resulting in the reconstructed values each core site s residual variance is used to inversely weight the cores respective contributions the interannual amplitude of the reconstructed accumulation rate is damped by the regressions and is thus calibrated to match that of the rcm data uncertainty and significance of changes is measured using statistical models a 12 or 86 gt yr 21 increase in ice sheet accumulation rate is found from the end of the little ice age in 1840 to the last decade of the reconstruction this 1840 1996 trend is 30 higher than that of 1600 2009 suggesting an accelerating accumulation rate the correlation of at g with the average surface air temperature in the northern hemisphere satnht remains positive through time while the correlation of at g with local near surface air temperatures or north atlantic sea surface temperatures is inconsistent suggestinga hemispheric scale climateconnection an annualsensitivityof at g to satnhtof 6 8 k 21 or 51 gt k 21 is found the reconstuction at g correlates consistently highly with the north atlantic oscillation index however at the 11 yr time scale the sign of this correlation flips four times in the 1870 2005 period

irreversible mass loss of canadian arctic archipelago glaciers 1 the canadian arctic archipelago caa contains the largest volume of glacier ice on earth outside of antarctica and greenland in the absence of significant calving caa glacier mass balance is governed by the difference between surface snow accumulation and meltwater runoff surface mass balance here we use a coupled atmosphere snow model to simulate present day and 21st century caa glacier surface mass balance through comparison with gravity recovery and climate experiment mass anomalies and in situ observations we show that the model is capable of representing present day caa glacier mass loss as well as the dynamics of the seasonal snow cover on the caa tundra next we force this model until 2100 with a moderate climate warming scenario ar5 rcp4 5 we show that enhanced meltwater runoff from caa glaciers is not sufficiently compensated by increased snowfall extrapolation of these results toward an ar5 multimodel ensemble results in sustained 21st century caa glacier mass loss in the vast majority 99 of the 7000 temperature realizations

lower eocene alluvial paleosols willwood formation northwest wyoming u s a and their significance for paleoecology paleoclimatology and basin analysis abstract the lower eocene willwood formation of northwest wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones nearly all of which show paleopedogenic modifications pedogenesis of willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation early local cementation by calcium carbonate and thin illuviation cutans on clastic grains pedogenesis in willwood mudstones is indicated by plant bioturbation insect and other invertebrate burrow casts and lebensspuren free iron aluminum and manganese mobilization including hydromorphic gleying sesquioxide and calcareous glaebule formation in lower parts of the solum presence of clay rich and organic carbon rich zones and well differentiated epipedons and albic and spodic horizons probable a horizons are also locally well developed occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin lenticular and unconnected fluvial sandstones in the willwood formation of the central and southeast bighorn basin suggest that these soils formed during times of rapid sediment accumulation the tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that willwood floodplains were broad and essentially featureless all willwood paleosols were developed on alluvial parent materials and are complex in that b horizons of younger paleosols were commonly superimposed upon and mask properties of suspected a and b horizons of the next older paleosols the soils appear to be wet varieties of the spodosol and entisol groups aquods and ferrods and aquents respectively though thick superposed and less mottled red purple and yellow paleosols resemble some ultisols most willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and or fluctuating water tables the up section decrease in frequency of gley mottles increase in numerical proportion and thickness of red versus orange coloration and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late willwood time this drying is believed to be related to creation of rain shadows and spacing of rainfall but not necessarily decrease in absolute rainfall due to progressive tectonic structural elevation of the mountainous margins of the bighorn basin

acceleration of the contribution of the greenland and antarctic ice sheets to sea level rise 1 ice sheet mass balance estimates have improved substantially in recent years using a variety of techniques over different time periods and at various levels of spatial detail considerable disparity remains between these estimates due to the inherent uncertainties of each method the lack of detailed comparison between independent estimates and the effect of temporal modulations in ice sheet surface mass balance here we present a consistent record of mass balance for the greenland and antarctic ice sheets over the past two decades validated by the comparison of two independent techniques over the last 8 years one differencing perimeter loss from net accumulation and one using a dense time series of time variable gravity we find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss in 2006 the greenland and antarctic ice sheets experienced a combined mass loss of 475 158 gt yr equivalent to 1 3 0 4 mm yr sea level rise notably the acceleration in ice sheet loss over the last 18 years was 21 9 1 gt yr2 for greenland and 14 5 2 gt yr2 for antarctica for a combined total of 36 3 2 gt yr2 this acceleration is 3 times larger than for mountain glaciers and ice caps 12 6 gt yr2 if this trend continues ice sheets will be the dominant contributor to sea level rise in the 21st century

relation of paleovegetation to geometry and cyclicity of some fluvial carbonaceous deposits abstract the fluvial lower eocene willwood formation bighorn basin wyoming is composed largely of red oxidized overbank sediment that has been extensively altered by soil formation within this matrix are two different types of dominantly fine grained drab to dark colored deposits that contain abundant plant remains the first are areally restricted lenticular bodies that truncate underlying mudstone layers these are interpreted as having formed in abandoned sections of channels deposits of the second type are tabular as much as 10 km in lateral extent and rest conformably on other floodplain sediment these units show a cyclic arrangement of sedimentary subunits sedimentologic and paleobotanic evidence suggests that these tabular deposits accumulated under a sequence of vegetatio al types including in succession a floodplain marsh a swamp forest and a drier ground floodplain forest these interpretations stress the interaction of vegetational succession soil characteristics and fluvial morphology in creating the chemical conditions that led to the preservation of organic matter the stratigraphic distribution of the two types of deposits within the willwood formation suggests that in the bighorn basin tectonism exerted a greater influence on the geometry of carbonaceous deposits than did climate

distal alluvial deposits in a foreland basin setting the lower freshwater molasse lower miocene switzerland sedimentology architecture and palaeosols the lower freshwater molasse untere susswasser molasse crops out over a wide area of the swiss molasse basin coarse grained alluvial fan conglomerates dominate in proximal basin areas along the alpine front these conglomerates pass northwards into sandstones and mudstones of an extensive northeastward draining meandering river system which ran parallel to the basin axis sedimentological study of outcrops quarry exposures and boreholes in the basal miocene aquitanian has permitted detailed facies analysis of this distal alluvial sequence the distal aquitanian is made up of distinct architectural elements characterized by their geometries and sedimentary structures each may be assigned to a particular depositional setting meander belt levees crevasse channels and splays overbank fines and palaeosols and lacustrine meander belt sandstones were deposited in mixed load channels with a dominant bedload component sandstones commonly comprise amalgamated and locally stacked ribbon bodies 2 15 m thick and 150 1500 m wide interbedded rippled laminated and mottled fine grained levee sandstones and siltstones form lenticular packages up to 3 m thick and 30 100 m across small scale crevasse channel sandstones 2 4 m thick and 5 10 m across pass laterally into metre scale medium to fine grained crevasse sandstone sheets rare laminated lacustrine siltstones occur only in the north east part of the basin floodplain mudstones and marls make up the remainder of the succession these display a variety of pedogenic features recording cyclical palaeosol development palaeosols show strong variations in morphology and maturity both laterally across the floodplain and downstream along the basin axis reflecting local variation in aggradation rate associated with proximity to alluvial channel courses as well as regional variation in subsidence and floodplain drainage analysis of the organization and distribution of the various sediment bodies permits reconstruction of the fluvial system and allows development of a model for the sedimentary architecture of the lower freshwater molasse in the study area integration of palaeosol studies into a well defined architectural framework assists recognition of areal facies belts and may aid location of sand prone sequences in the subsurface

basin scale partitioning of greenland ice sheet mass balance components 2007 2011 a r t i c l e i n f o a b s t r a c t the current deficit in greenland ice sheet mass balance is due to both a decrease in surface mass balance smb input and an increase in ice discharge d output while smb processes are beginning to be well captured by observationally constrained climate modeling insight into d is relatively limited we use insar derived velocities in combination with ice thickness observations to quantify the mass flux f across a flux perimeter around the ice sheet at 1700 m elevation to quantify d we correct f for smb as well as changes in volume due to ice dynamics in the area downstream of the gate using a 1961 1990 reference climatology smb field from the mar regional climate model we quantify ice sheet mass balance within eighteen basins we find a 2007 2011 mean d of 515 57 gt yr 1 we find a 2007 2011 mean total mass balance of 262 21 gt yr 1

grace hydrological estimates for small basins evaluating processing approaches on the high plains aquifer usa the gravity recovery and climate experiment grace satellites provide observations of water storage variation at regional scales however when focusing on a region of interest limited spatial resolution and noise contamination can cause estimation bias and spatial leakage problems that are exacerbated as the region of interest approaches the grace resolution limit of a few hundred km reliable estimates of water storage variations in small basins require compromises between competing needs for noise suppression and spatial resolution the objective of this study was to quantitatively investigate processing methods and their impacts on bias leakage grace noise reduction and estimated total error allowing solution of the trade offs among the methods tested is a recently developed concentration algorithm called spatiospectral localization which optimizes the basin shape description taking into account limited spatial resolution this method is particularly suited to retrieval of basin scale water storage variations and is effective for small basins to increase confidence in derived methods water storage variations were calculated for both csr center for space research and grgs groupe de recherche de geodesie spatiale grace products which employ different processing strategies the processing techniques were tested on the intensively monitored high plains aquifer 450 000 km2 area where application of the appropriate optimal processing method allowed retrieval of water storage variations over a portion of the aquifer as small as 200 000 km2

the distinction between ground water gley and surface water gley phenomena in tertiary paleosols of the ebro basin ne spain abstract in studies of paleosols the distinction iron segregation due to either surface water or ground water fluctuatins is hardly ever made recognition of subsequent hydromorphic phases is even more rare nevertheless such distinctions can be made and are very useful in determining the paleoenvironment in this study we demonstrate that subsequent stages of hydromorphism and their sequence can be recognized in paleogene paleosols of the ebro basin it appears that in these carbonate rich hydromorphic oils goethite iron segregations are due to ground water influence while hematitic segregations are due to surface water the preservation of original mineralogy in this case is due to absence of late diagenetic transformations the results contradict the thesis that red colours in such paleosols would be the result of the late diagenesis in the studied samples mottledcolour patterns frequently indicate fairly advanced soil formation although weathering of primary minerals is almost absent detailed study of colour patterns gives much additional information on the post depositional environment

plant and mammal diversity in the paleocene to early eocene of the bighorn basin abstract abundant plant and vertebrate fossils have been recovered from fluvial sediments deposited in the bighorn basin wyoming during the first 13 m y of the tertiary here we outline and discuss changes in the composition and diversity of floras and faunas during this period which includes the recovery of terrestrial ecosystems from the k t boundary extinctions and later during the paleocene eocene transition the greatest global warming of the cenozoic floral diversity has been studied at three levels of spatial resolution sub local at individual collecting sites local along a single bed or stratigraphic horizon and basin wide regional sub local diversity shows a moderate increase from the early to late paleocene followed by a decrease across the paleocene eocene boundary then an increase into the later early eocene local heterogeneity was lower in paleocene backswamp floras although distinct groups of species dominated in different local fluvial settings such as backswamps and alluvial ridges heterogeneity of backswamp forests increased by about 65 from the early to late wasatchian early eocene the number of plant species inferred from the bighorn basin dataset rose gradually from the puercan to an early clarkforkian peak of about 40 species declined sharply to about 25 species by the clarkforkian wasatchian boundary then rose through the wasatchian to about 50 species a regional analysis of mammalian genera shows high turnover and a rapidly increasing number of genera within a million years of the k t boundary 10 50 genera a slight decline to 40 genera by the early clarkforkian then an increase from 40 to 75 genera by the late wasatchian our analyses found no major extinctions in mammals during the paleocene and early eocene in the bighorn basin but a one third decrease in the number of plant species at about the paleocene eocene boundary rates of taxonomic turnover were much higher for mammals than plants the diversity trends for plants and mammals show little congruence implying that the two groups responded in a very different manner to post k t extinction opportunities there is also little congruence between plant diversity levels and change in mean annual temperature mat as inferred from foliar physiognomy

paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin u s a abstract in the central appalachian basin at least two major climate changes affected sedimentation during the late paleozoic stratigraphically these two changes are indicated by the distribution of coal beds the variation in coal quality and the variation in rock lithologies in latest mississippian or earliest pennsylvanian time the climate changed from dry seasonal tropical to ever wet equable tropical the equable climate prevailed into the middle pennsylvanian influencing the morphology and geochemistry in peat forming environments many of the peat deposits which formed under the equable climate were probably domed raised bogs low concentrations of dissolved solids in peat formation water resulted in low buffering capacity organic acids caused acidic ph another climate change occurred in late middle pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and ph 4 to 7 in surface and near surface water throughout the remainder of the pennsylvanian the surfaces of peat deposits were probably planar not domed water in peat forming and other depositional environments became more nearly neutral the coal beds derived from these peats are highly variable in both ash and sulfur contents drier or more seasonal climates are also indicated by sequences of 1 calcareous sandstone and shale 2 nonmarine limestone that shows shallow water and subaerial exposure features and 3 calcareous paleosols that have caliche characteristics our data and observations indicate that physical depositional environment models for the origin of coal do not adequately explain variations in mineral matter content and composition in commercial quality coal beds in the central appalachian basin stratigraphic variation in mineral matter in coal beds and in syngenetic and early diagenetic minerals in rocks associated with the coal beds appears to be better explained by changes in geochemical conditions of nonmarine sedimentation paleoclimate was a principle control on these geochemical conditions

the formation of beds underlying carbonaceous shales as aquic paleosols examples from the bighorn basin of wyoming abstract drab grey mudrocks consistently occur below carbonaceous shales in lower tertiary alluvial sediments of the western interior basins of the usa superficially these mudrocks here termed underbeds look similar to underclays commonly found below coal beds however it is unclear whether the association between the carbonaceous shales and the underbeds is genetic or whether underbed features developed independently before the onset of carbonaceous shale deposition to solve this problem three underbeds and their associated carbonaceous shales were studied from upper palaeocene and lower eocene sections in the bighorn basin of wyoming the sedimentology structure organic content mineralogy and palaeopedology of these beds was examined results indicate that the precursors to these underbeds formed as aquic or hydromorphic soils in periodically dry swamps on a distal alluvial floodplain periodic drying of the upper most part of the substrate led to oxidation plant growth homogenisation of the sediment and degradation of organic matter however conditions were wet enough to inhibit mottling and downward leaching of minerals and facilitated the formation of hydrated iron oxides aquic soil formation ceased when a local rise in the water table caused water logging and permanently oxygen reduced conditions this allowed the accumulation of organic material and deposition of carbonaceous shales above the aquic soils during carbonaceous shale formation the aquic soils now underbeds below the shales were permanently water logged the distinctive features of these lower tertiary underbeds appear to have formed prior to organic accumulation burial and ground water saturation during formation of the overlying carbonaceous shales merely helped to preserve the homogeneous features of these underbeds

a relationship between alluvial backswamps and avulsion cycles an example from the willwood formation of the bighorn basin wyoming abstract stratigraphically limited intervals from the lower eocene willwood formation contain laterally extensive carbonaceous shales and ribbon sandstone networks associated with channel avulsion we present data from one such interval that documents the avulsion sequence vertical sections measured along the outcrop of this interval are similar and comprise a basal carbonaceous shale overlain by fine grained deposits on which weakly developed hydromorphic paleosols formed the paleosols enclose and are locally incised by ribbon sandstones some of which cut down to and partly through the carbonaceous shale the ribbons have width thickness ratios between 3 and 13 some ribbons cluster at a particular stratigraphic level which together with paleocurrent trends suggests that they formed channel networks sections are capped by yellow brown paleosols showing moderate pedogenic development we suggest that the carbonaceous shales developed in low lying topogeneous swamps in distal portions of the floodplain far from the trunk channel such a location set limits on the sediment that they received the mudrocks with weakly developed paleosols and associated ribbon sandstones are interpreted as crevasse splay complexes resulting from avulsion of the trunk river the ribbon sandstones represent ancient feeder channels of the avulsion complex the rapid influx of avulsion deposits appears to have been crucial to preserving the organic material and this study reveals an important and as yet uncharacterized link between trunk channel processes and the accumulation of organic rich deposits in distal alluvial swamps similar deposits are found in other stratigraphic units in the rocky mountain region and the development of these and other organic rich deposits should be reassessed in terms of channel avulsion

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

an improved mass budget for the greenland ice sheet extensive ice thickness surveys by nasa s operation icebridge enable over a decade of ice discharge measurements at high precision for the majority of greenland s marine terminating outlet glaciers prompting a reassessment of the temporal and spatial distribution of glacier change annualmeasurements for 178 outlet glaciers reveal that despite widespread acceleration only 15 glaciers accounted for 77 of the 739 29 gt of ice lost due to acceleration since 2000 and four accounted for 50 among the top sources of loss are several glaciers that have received little scientific attention the relative contribution of ice discharge to total loss decreased from 58 before 2005 to 32 between 2009 and 2012 as such 84 of the increase in mass loss after 2009 was due to increased surface runoff these observations support recentmodel projections that surface mass balance rather than ice dynamics will dominate the ice sheet s contribution to 21st century sea level rise

snow load effect on the earth s rotation and gravitational field 1979 1985 a global monthly snow depth data set has been generated from the nimbus 7 satellite observations using passive microwave remote sensing techniques in this paper we analyze 7 years of data 1979 1985 to compute the snow load effects on the earth s rotation and low degree zonal gravitational field a uniform sea level decrease has been assumed in order to conserve water mass the resultant time series show dominant seasonal cycles the annual peak to peak variation in j2 is found to be 2 3 x 10 o that in j3 to be 1 1 x 10 o and believed to decrease rapidly for higher degrees the corresponding change in the length of day is 41 us the annual wobble excitation is 4 9 marc sec 109 o for the prograde motion component and 4 8 marc sec 28 o for the retrograde motion component the excitation power of the chandler wobble due to the snow load is estimated to be about 25 db less than the power needed to maintain the observed chandler wobble the superior quality of the satellite data over conventional data acquired by ground observations and modeling is demonstrated we also discuss the role of atmospheric water and the problems arising from the lack of snow load observations over the antarctic and greenland ice sheets

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

revisiting greenland ice sheet mass loss observed by grace in this paper we discuss a new method for determining mass time series for 16 hydrological basins representing the greenland system gs whereby we rely on gravity recovery and climate experiment grace mission data in the same analysis we also considered observed mass changes over ellesmere island baffin island iceland and svalbard ebis the summed contribution of the complete system yields a mass loss rate and acceleration of 252 28 gt yr and 22 4 gt yr2 between march 2003 and february 2010 where the error margins follow from two glacial isostatic adjustment gia models and three processing centers providing grace monthly potential coefficient sets we describe the relation between mass losses in the gs and the ebis region and found that the uncertainties in all areas are correlated the summed contribution of ellesmere island baffin island iceland and svalbard yields a mass loss rate of 51 17 gt yr and an acceleration of 13 3 gt yr2 between march 2003 and february 2010 the new regional basin reconstruction method shows that the mass loss within the southeastern basins in the gs has slowed down since 2007 while mass loss in western basins increased showing a progression to the north of greenland

antarctica greenland and gulf of alaska land ice evolution from an iterated grace global mascon solution we have determined the ice mass evolution of the antarctica and greenland ice sheets ais and gis and gulf of alaska goa glaciers from a new grace global solution of equal area surface mass concentration parcels mascons in equivalent height of water the mascons were estimated directly from the reduction of the inter satellite k band range rate kbrr observations taking into account the full noise covariance and formally iterating the solution the new solution increases signal recovery while reducing the grace kbrr observation residuals the mascons were estimated with 10 day and 1 arc degree equal area sampling applying anisotropic constraints an ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances the details and causes of the spatial and temporal variability of the land ice regions studied are discussed the estimated mass trend over the total gis ais and goa glaciers for the time period 1 december 2003 to 1 december 2010 is 380 plus or minus 31 gt a exp 1 equivalent to 1 05 plus or minus 0 09 mma exp 1 sea level rise over the same time period we estimate the mass acceleration to be 41 plus or minus 27 gt a exp 2 equivalent to a 0 11 plus or minus 0 08 mm a exp 2 rate of change in sea level the trends and accelerations are dependent on significant seasonal and annual balance anomalies

a new methodology for detecting ice sheet surface elevation changes from laser altimetry data the integrated program surface elevation reconstruction and change detection serac was specifically designed and developed for detecting surface elevation and elevation changes from the ice cloud and land elevation satellite icesat icesat carried geoscience laser altimeter system glas with the primary goal of measuring elevation changes of the polar ice sheets to sufficient accuracy to assess their impact on global sea level glas had three lasers that operated sequentially with two to three campaigns per year the footprint size was about 70 m and the point to point spacing between neighboring laser points reached 170 m serac copes with different scenarios originally developed for calculating surface elevation changes of crossover areas it was extended to along track areas and the inclusion of non icesat laser data such as airborne topographic mapper atm an airborne laser scanning system developed by nasa wallops flight facility the adjustment system of serac simultaneously computes the shape of surface patches containing laser points of the same time epoch estimates surface elevation changes and approximates the time series of elevation changes by a polynomial after removing the seasonal cycle results shown in the second part of the paper demonstrate the potential of serac for calculating detailed ice sheet elevation and volume change histories greenland ice sheet volume changes calculated from a combined icesat atm data set show good agreement with previously published results and provide improved sampling in the rapidly thinning coastal regions of southern greenland moreover the polynomial approximation of the time series of surface elevation changes is taken to advantage in the last example of northwest greenland illuminating the intricate thinning thickening patterns that often vary considerably over short spatial scales

spread of ice mass loss into northwest greenland observed by grace and gps 1 greenland s main outlet glaciers have more than doubled their contribution to global sea level rise over the last decade recent work has shown that greenland s mass loss is still increasing here we show that the ice loss which has been well documented over southern portions of greenland is now spreading up along the northwest coast with this acceleration likely starting in late 2005 we support this with two lines of evidence one is based on measurements fromthegravityrecoveryandclimateexperiment grace satellite gravity mission launched in march 2002 the other comes from continuous global positioning system gps measurements from three long term sites on bedrock adjacent to the ice sheet the grace results provide a direct measure of mass loss averaged over scales of a few hundred km the gps data are used to monitor crustal uplift caused by ice mass loss close to the sites the grace results can be used to predict crustal uplift which can be compared with the gps data in addition to showing that the northwest ice sheet margin is now losing mass the uplift results from both the gps measurements and the grace predictions show rapid acceleration in southeast greenland in late 2003 followed by a moderate deceleration in 2006 because that latter deceleration is weak southeast greenland still appears to be losing ice mass at a much higher rate than it was prior to fall 2003 in a more general sense the analysis described here demonstrates that gps uplift measurements can be used in combination with grace mass estimates to provide a better understanding of ongoing greenland mass loss an analysis approach that will become increasingly useful as long time spans of data accumulate from the 51 permanent gps stations recently deployed around the edge of the ice sheet as part of the greenland gps network gnet citation khan s a j wahr m bevis i velicogna and e kendrick 2010 spread of ice mass loss into northwest greenland observed by grace and gps geophys res lett 37 l06501 doi 10 1029 2010gl042460

high resolution greenland ice sheet inter annual mass variations combining grace gravimetry and envisat altimetry abstract inter annual mass variations of the greenland ice sheet gris are important for improving mass balance estimates validation of atmospheric circulation models and their potential improvement by combining observed inter annual variations from gravity recovery and climate experiment grace and environmental satellite envisat altimetry data over the period from january 2003 to december 2009 we are able to estimate the nominal density with the objective of obtaining higher resolution mass changes using altimeter data at the inter annual scale we find high correlations between these two inter annual variations on the order of 0 7 over 60 of the gris in particular over the west side along the central ice divide significant negative correlations are found in parts of northeast and southeast gris where negative inter annual variation correlations were also found between mass change from grace and snow depth from ecmwf reanalysis in a previous study in the regions of positive correlation the estimated nominal densities range from 383 7 50 9 to 596 2 34 1 kg m 3 we demonstrate the feasibility of obtaining high resolution inter annual mass variation over southwest gris one of the regions with positive correlations based on density corrected envisat altimetry 2003 2009 a definitive explanation for the existence of regions of negative correlation remains elusive

ice sheet in peril earth s large ice sheets in greenland and antarctica are major contributors to sea level change at present the greenland ice sheet see the photo is losing mass in response to climate warming in greenland 1 but the present changes also include a long term response to past climate transitions on page 590 of this issue macgregor et al 2 estimate the mean rates of snow accumulation and ice flow of the greenland ice sheet over the past 9000 years based on an ice sheet wide dated radar stratigraphy 3 they show that the present changes of the greenland ice sheet are partly an ongoing response to the last deglaciation the results help to clarify how sensitive the ice sheet is to climate changes

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

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

the effect of fluctuations in surface density accumulation and compaction on elevation change rates along the egig line central greenland repeated measurements of density profiles and surface elevation along a 515 km section of the greenland ice sheet have been used to determine elevation change rates and the error in determining mass balance from these rates which arises from short term fluctuations in mass input compaction and surface density over the 28 months from spring 2004 to summer 2006 the average error over 100 km sections of the traverse ranged from 0 006 to 0 100 m a 1 the lowest values comparable with the system accuracy of the cryosat radar altimeter 0 033 m a 1 were found below 3000 m the surface density required to translate the elevation change into mass change decreased from 0 40 g cm 3 at an elevation of 2348 m to 0 33 g cm 3 at an elevation of 3264 m from the density profiles the equivalent values for a time period of 10 years were found to be 0 48 and 0 38 g cm 3 respectively

spatiotemporal interpolation of elevation changes derived from satellite altimetry for jakobshavn isbrae greenland estimation of ice sheet mass balance from satellite altimetry requires interpolation of point scale elevation change dh dt data over the area of interest the largest dh dt values occur over narrow fast flowing outlet glaciers where data coverage of current satellite altimetry is poorest in those areas straightforward interpolation of data is unlikely to reflect the true patterns of dh dt here four interpolation methods are compared and evaluated over jakobshavn isbrae an outlet glacier for which widespread airborne validation data are available from nasa s airborne topographic mapper atm the four methods are ordinary kriging ok kriging with external drift ked where the spatial pattern of surface velocity is used as a proxy for that of dh dt and their spatiotemporal equivalents st ok and st ked ked assumes a linear relationship between spatial gradients of velocity and dh dt which is confirmed for both negative pearson s correlation 0 85 and to a lesser degree positive 0 73 dh dt values when compared to atm data ked and st ked yield more realistic spatial patterns and higher thinning rates over 20 m yr 1 as opposed to 7 m yr 1 for ok spatiotemporal kriging smooths inter annual variability and improves interpolation in periods with sparse data coverage and we conclude therefore that st ked produces the best results using this method increases volume loss estimates from jakobshavn isbrae by up to 20 compared to those obtained by ok the proposed interpolation method will improve ice sheet mass balance reconstructions from existing and past satellite altimeter data sets with generally poor sampling of outlet glaciers

greenland high elevation mass balance inference and implication of reference period 1961 90 imbalance we revisit the input output mass budget of the high elevation region of the greenland ice sheet evaluated by the program for arctic regional climate assessment parca our revised reference period 1961 90 mass balance of 54 48gt a is substantially greater than the 0 21gt a assessed by parca but consistent with a recent fully independent input output estimate of high elevation mass balance 41 61gt a together these estimates infer a reference period high elevation specific mass balance of 4 8 5 4 cmw e a the probability density function pdf associated with this combined input output estimate infers an 81 likelihood of high elevation specific mass balance being positive 0 cmw e a during the reference period and a 70 likelihood that specific balance was 2 cmw e a given that reference period accumulation is characteristic of centurial and millennial means and that in situ mass balance observations exhibit a dependence on surface slope rather than surface mass balance we suggest that millennial scale ice dynamics are the primary driver of subtle reference period high elevation mass gain failure to acknowledge subtle reference period dynamic mass gain can result in underestimating recent dynamic mass loss by 17 and recent total greenland

greenland ice sheet mass balance distribution of increased mass loss with climate warming 2003 07 versus 1992 2002 we derive mass changes of the greenland ice sheet gis for 2003 07 from icesat laser altimetry and compare them with results for 1992 2002 from ers radar and airborne laser altimetry the gis continued to grow inland and thin at the margins during 2003 07 but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s the net balance changed from a small loss of 7 3g t a 1 in the 1990s to 171 4g t a 1 for 2003 07 contributing 0 5 mm a 1 to recent global sea level rise we divide the derived mass changes into two components 1 from changes in melting and ice dynamics and 2 from changes in precipitation and accumulation rate we use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation driven changes to mass changes increased losses from melting and ice dynamics 17 206 gt a 1 are over seven times larger than increased gains from precipitation 10 35 gt a 1 during a warming period of 2 k 10 a 1 over the gis above 2000 m elevation the rate of gain decreased from 44 to 28 gt a 1 while below 2000 m the rate of loss increased from 51 to 198 gt a 1 enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers as well as accelerating ice flow increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales

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

modeling of firn compaction for estimating ice sheet mass change from observed ice sheet elevation change changes in ice sheet surface elevation are caused by a combination of ice dynamic imbalance ablation temporal variations in accumulation rate firn compaction and underlying bedrock motion thus deriving the rate of ice sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion which do not involve changes in mass and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability we use a 25year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model we apply this formulation to icesat measurements of surface elevation change at three locations on the greenland ice sheet in order to separate the accumulation driven changes from the ice dynamic ablation driven changes and thus to derive the corresponding mass change our calculated densities for the accumulation driven changes range from 410 to 610kgm 3 which along with 900kgm 3 for the dynamic ablation driven changes gives average densities ranging from 680 to 790kgm 3 we show that using an average or effective density to convert elevation change to mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign

multiple paleosols of the late albian boulder creek formation british columbia canada fifteen lithified paleosols closely spaced in vertical sequence occur in the top 90 m of the late albian boulder creek formation in the foothills of northeastern british columbia canada the paleosols have well developed profiles 0 5 to 1 5 m thick including a b and c horizons the paleosols are characterized by their grey colour cutans vertical roots peds spherulitic siderite and absence of sedimentary structures the paleosols formed during a period when one or more basin wide unconformities occurred as a result of either eustatic sea level fluctuations or local tectonic events these unconformities represent the terrestrial record of a lowered base level which caused valley incision and decreased rates of sedimentation on the incised flood plain the climate was humid to subhumid overall the environment in which these soils developed was of low relief and subject to little erosion the water table was high for part of the year but there is also evidence of periodic drying and oxidation of organic debris cumulatively the paleosols in this interval may represent 150000 yr of non deposition

mass loss of greenland s glaciers and ice caps 2003 2008 revealed from icesat laser altimetry data 1 the recently finalized inventory of greenland s glaciers and ice caps gic allows for the first time to determine the mass changes of the gic separately from the ice sheet using space borne laser altimetry data corrections for firn compaction and density that are based on climatic conditions are applied for the conversion from volume to mass changes the gic which are clearly separable from the icesheet i e have a distinct ice divide or no connection lost 27 9 10 7 gt a 1 or 0 08 0 03 mm a 1 sea level equivalent sle between october 2003 and march 2008 all gic including those with strong but hydrologically separable connections lost 40 9 16 5 gt a 1 0 12 0 05 mm a 1 sle this is a significant fraction 14 or 20 of the reported overall mass loss of greenland and up to 10 of the estimated contribution from the world s gic to sea level rise the loss was highest in southeastern and lowest in northern greenland

local rates of ice sheet thickness change in greenland the rate of ice sheet thickness change is calculated for 10 sites in greenland by comparing measured values of ice vertical velocity and snow accumulation rate vertical velocities are derived from repeat surveys of markers using precision global positioning system techniques and accumulation rates are determined from stratigraphic analysis of firn cores the results apply to time scales covered by the firn core records which in most cases are a few decades a spectrum of thickness change rates is obtained ranging from substantial thinning to slow thickening the sites where ice sheet thinning is indicated are located near the ice sheet margin or in outlet glacier catchments interior and high elevation sites are predominantly in balance or thickening slowly uncertainties in the rates of thickness change are dominated by errors in the determination of accumulation rates the results of this work are broadly comparable with regional estimates of mass balance obtained from the analysis of catchment input vs discharge

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

ice sheet mass balance assessment attribution and prognosis contrary to prior expectations that warming would cause mass addition averaged over the greenland and antarctic ice sheets and over the next century the ice sheets appear to be losing mass at least partly in response to recent warming with warming projected for the future additional mass loss appears more likely than not

mass balance of the greenland ice sheet from 1958 to 2007 we combine estimates of the surface mass balance smb of the greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge d to deduce the total ice sheet mass balance during that time period we find a robust correlation r2 0 83 between anomalies in smb and in d which we use to reconstruct a continuous series of total ice sheet mass balance we find that the ice sheet was losing 110 70 gt yr in the 1960s 30 50 gt yr or near balance in the 1970s 1980s and 97 47 gt yr in 1996 increasing rapidly to 267 38 gt yr in 2007 multi year variations in ice discharge themselves related to variations in smb cause 60 20 more variation in total mass balance smb and therefore dominate the ice sheet mass budget copyright 2008 by the american geophysical union

recent changes in thickness of the devon island ice cap canada 1 long term rates of thickness change were derived at several spatial scales using a variety of methods for most of the devon island ice cap nunavut canada basin wide thickness change calculations were derived for the accumulation zones of all major drainage basins as the area averaged volume difference between balance and insar fluxes at the altitude of the long term equilibrium line ela thickness changes for ablation zones were derived as a function of the surface mass balance flux across the el and calving flux averaged across the ablation areas average rates of thickness change are near zero in the accumulation zones of the northern and southwestern basins but reach 0 23 0 11 m a 1 w e in the southeast basin due to dynamic thinning thickness changes were also estimated along five major outlet glaciers as a function of flux divergence and net surface mass balance and along the belcher glacier by comparing elevation values derived from 1960s aerial photography with those derived from 2005 nasa airborne topographic mapper atm surveys ice dynamics have had a significant influence on the pattern of thickness change of all outlet glaciers examined in this study volume changes derived from the basin wide values indicate a net loss of 76 8 7 km3 water equivalent from the main portion of the ice cap from 1960 to 1999 contributing 0 21 0 02 mm to global sea level over this time this value is 44 greater than previous estimates of volume change based on volume area scaling methods and surface mass balance alone

elemental distribution and pyrite occurrence in a freshwater peatland alberta a continental minerotrophic peatland in alberta was studied for its botanical petrographical mineralogical and geochemical characteristics changes in peat stratigraphy and mineralogy are related and development toward oligotrophic conditions is recorded elemental concentration and distribution vary in the peat profile reflecting the influence of natural and anthropogenic factors on peat geochemistry many elements al as ba co cr fe mn th v accumulate in the zone of water table fluctuation as a result of changes in redox chemistry the relative elemental concentration at the surface and near surface e g as cr sb th ti v may also be attributed to atmospheric deposition related to anthropogenic activity chemical analysis al fe mg na si ti also reveals the presence of a non visible volcanic ash rich layer near the base of the peat profile possibly mazama tephra this study provides evidence of pyrite formation in a freshwater peat forming environment associated with high sul

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

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

mass changes of the greenland and antarctic ice sheets and shelves and contributions to sea level rise 1992 2002 changes in ice mass are estimated from elevation changes derived from 10 5 years greenland and 9 years antarctica of satellite radar altimetry data from the european remote sensing satellites ers 1 and 2 for the first time the dh dt values are adjusted for changes in surface elevation resulting from temperature driven variations in the rate of firn compaction the greenland ice sheet is thinning at the margins 42 2g t a 1 below the equilibrium line altitude ela and growing inland 53 2g t a 1 above the ela with a small overall mass gain 11 3g t a 1 0 03 mm a 1 sle sea level equivalent the ice sheet in west antarctica wa is losing mass 47 4g t a 1 and the ice sheet in east antarctica ea shows a small mass gain 16 11 gt a 1 for a combined net change of 31 12 gt a 1 0 08 mm a 1 sle the contribution of the three ice sheets to sea level is 0 05 0 03 mm a 1 t he antarctic ice shelves show corresponding mass changes of 95 11 gt a 1 in wa and 142 10 gt a 1 in ea thinning at the margins of the greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate the marked thinnings in the pine island and thwaites glacier basins of wa and the totten glacier basin in ea are probably ice dynamic responses to long term climate change and perhaps past removal of their adjacent ice shelves the ice growth in the southern antarctic peninsula and parts of ea may be due to increasing precipitation during the last century

simultaneous estimation of global present day water transport and glacial isostatic adjustment global water transport between oceans and continents during the transition from glacial to interglacial times has been enormous the viscoelastic solid earth has been responding to this unloading of large ice masses with a rise of the land masses in a process termed glacial isostatic adjustment in addition significant changes in the land ocean water distribution occur at present as both present day changes in the ice water thickness and glacial isostatic adjustment affect space geodetic measurements it is difficult to untangle the relative contributions of these two processes here we combine gravity measurements and geodetic data of surface movement with a data assimilating model of ocean bottom pressure to simultaneously estimate present day water transport and glacial isostatic adjustment we determine their separate contributions to movements in the geocentre which occur in response to changes in the earth s mass distribution with uncertainties below 0 1 mm yr 1 according to our estimates mass losses between 2002 and 2008 in greenland alaska yukon and west antarctica are 104 23 101 23 and 64 32 gt yr 1 respectively our estimates of glacial isostatic adjustment indicate a large geocentre velocity of 0 72 0 06 mm yr 1 in the polar direction we conclude that a significant revision of the present estimates of glacial isostatic adjustments and land ocean water exchange is required present day changes in the thickness of ice sheets and glacial isostatic adjustment both affect space geodetic measurements a combination of gravity measurements and geodetic data of surface movement with a data assimilating model of ocean bottom pressure allows the simultaneous estimation of present day water transport and glacial isostatic adjustment