post processing removal of correlated errors in grace data 1 gravity fields produced by the gravity recovery and climate experiment grace satellite mission require smoothing to reduce the effects of errors present in short wavelength components as the smoothing radius decreases these errors manifest themselves in maps of surface mass variability as long linear features generally oriented north to south i e stripes the presence of stripes implies correlations in the gravity field coefficients here we examine the spectral signature of these correlated errors and present a method to remove them finally we apply the filter to a model of surface mass variability to show that the filter has relatively little degradation of the underlying geophysical signals we seek to recover

a community based geological reconstruction of antarctic ice sheet deglaciation since the last glacial maximum a robust understanding of antarctic ice sheet deglacial history since the last glacial maximum is important in order to constrain ice sheet and glacial isostatic adjustment models and to explore the forcing mechanisms responsible for ice sheet retreat such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and sub antarctic islands here we report a new synthesis of those datasets based on an accompanying series of reviews of the geological data organised by sector we present a series of timeslice maps for 20 ka 15 ka 10 ka and 5 ka including grounding line position and ice sheet thickness changes along with a clear assessment of levels of confidence the reconstruction shows that the antarctic ice sheet did not everywhere reach the continental shelf edge at its maximum that initial retreat was asynchronous and that the spatial pattern of deglaciation was highly variable particularly on the inner shelf the deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small antarctic contribution to meltwater pulse 1a we discuss key areas of uncertainty both around the continent and by time interval and we highlight potential priorities for future work the synthesis is intended to be a resource for the modelling and glacial geological community

composition and origin of early cambrian tiantaishan phosphorite mn carbonate ores shaanxi province china abstract the tiantaishan phosphorite mn carbonate ores occur in the early cambrian tananpo formation in complexly folded and faulted rocks located in southern shaanxi province about 65 10 6 tonnes of 17 p 2 o 5 ore reserves exist and mn ore reserves are about 8 3 10 6 tonnes of 18 mn the stratigraphic sequence in ascending order consists of black phyllite black to gray phosphorite ore black phyllite rhodochrostone ore mn mixed carbonates and dolostone data are presented from microprobe mineral chemistry whole rock chemistry stable isotopes of carbonates x ray mineralogy petrographic and sem observations and statistical analysis of chemical data the dominant ore forming minerals are hydroxy and carbonate fluorapatite and ca rhodochrosite with mg kutnahorite and dolomite comprising the mn mixed carbonate section pyrite occurs in all rock types and alabandite mns occurs throughout the rhodochrostone section the mean p 2 o 5 content of phosphorite is 31 and argillaceous phosphorite is 16 while the mean mno content of rhodochrostone ore is 37 phosphorite ores are massive spheroidal laminated and banded while rhodochrostone ores have oolitic spheroidal and granular fabrics the most distinguishing characteristics of the ores are high total organic carbon toc contents mean 8 4 in the phosphorite and high p 2 o 5 contents mean 2 7 in the rhodochrostone ore the atypically high toc contents in the tiantaishan phosphorite probably result from very strong productivity leading to high sedimentation rates accompanied by weak reworking of sediments poor utilization of the organic matter by bacteria and or partial replacement of bacterial or algal mats by the apatite the depositional setting of the ores was the margin of an epicontinental seaway created as a direct consequence of global processes that included break up of a supercontinent formation of narrow seaways creation of extensive continental shelves overturn of stagnant metal rich deep ocean waters and marine transgression water depth increased from deposition of the black phyllite sequence through deposition of the mn mixed carbonate sequence then shallowed again during deposition of the overlying dolostone sequence bottom waters were mostly dysoxic to suboxic but fluctuated from oxic to anoxic productivity was high during deposition of the black phyllite sequence increased during precipitation of phosphorite and then decreased to moderate levels during precipitation of rhodochrostone ores biosilica contributions occur in each lithology but are greatest in rhodochrostone changes in sedimentation were determined by changes in water depth productivity upwelling sea level change and ventilation of the depositional basin the source of the phosphorus was organic matter produced in great quantities during deposition of the black phyllite and phosphorite sequences in a zone of coastal upwelling organic matter accumulation was rapid globally mn was supplied by overturn of stagnant metal rich deep ocean waters which were redistributed to areas of coastal upwelling and seaways that process may have been initiated by latest proterozoic glaciations which would have promoted density stratification and accumulation and storage of metals regionally mn was supplied by terrigenous input into the shallow seaway and hydrothermal input into the deeper water parts of that seaway locally mn sources included leaching and transport of metals from the sediment column manganese was stored locally in low oxygen not anoxic seawater prior to mn ore formation the source of the carbon in the mn carbonates and dolostones was predominantly seawater bicarbonate and secondarily co 2 derived from the oxidation of organic matter in the bacterially mediated diagenetic zone of sulfate reduction

increased ice loading in the antarctic peninsula since the 1850s and its effect on glacial isostatic adjustment antarctic peninsula ap ice core records indicate significant accumulation increase since 1855 and any resultant ice mass increase has the potential to contribute substantially to present day glacial isostatic adjustment gia we derive empirical orthogonal functions from climate model output to infer typical spatial patterns of accumulation over the ap and by combining with ice core records estimate annual accumulation for the period 1855 2010 in response to this accumulation history high resolution ice sheet modeling predicts ice thickness increases of up to 45 m with the greatest thickening in the northern and western ap whilst this thickening is predicted to affect grace estimates by no more than 6 2 gt yr it may contribute up to 7 mm yr to the present day gia uplift rate depending on the chosen earth model with a strong east west gradient across the ap its consideration is therefore critical to the interpretation of observed gps velocities in the ap

revisiting grace antarctic ice mass trends and accelerations considering autocorrelation previous grace derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model including also semi annual annual and tidal aliasing terms are not serially correlated we consider ice mass change time series for antarctica and show that significant autocorrelation is in fact present we examine power law and autoregressive models and compare them to those that assume white uncorrelated noise the data do not let us separate autoregressive and power law models but both indicate that white noise uncertainties need to be scaled up by a factor of up to 4 for accelerations and 6 for linear rates depending on length of observations and location for the whole of antarctica east antarctica and west antarctica the scale factors are 1 5 1 5 and 2 2 respectively for the trends and for the accelerations 1 5 1 5 and 2 1 substantially lower scale factors are required for offshore time series suggesting much of the time correlation is related to continental mass changes despite the higher uncertainties we find significant 2 sigma accelerations over much of west antarctica overall increasing mass loss and dronning maud land increasing mass gain as well as a marginally significant acceleration for the ice sheet as a whole increasing mass loss

trace metal pollution of soils in northern england data from a regional geochemical survey of topsoils n 818 in rural and peri urban areas over a single parent material coal measures are used to identify two types of trace metal pollution severe local contamination at 20 sites and widespread diffuse pollution in more densely populated areas median concentrations of several trace metals in topsoils were significantly higher in areas of high compared to low population density percentage increases in parenthesis as 31 cu 39 fe 7 mo 26 36 ni 29 pb 20 sn 40 and zn 11 four potential pathways of diffuse trace metal pollution are postulated coal ash dispersal atmospheric aerosols derived from coal combustion the historical spreading of sewage waste and those related to road vehicles the statistical analysis of geochemical data classified by local human population density can be an effective means of identifying the magnitude and extent of diffuse pollution and could help to establish natural background levels

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

recent antarctic ice mass loss from radar interferometry and regional climate modelling observed estimates of ice losses in antarctica combined with regional modelling of ice accumulation in the interior suggest that east antarctica is close to a balanced mass budget but large losses of ice occur in the narrow outlet channels of west antarctic glaciers and at the northern tip of the antarctic peninsula

the melting history of the late pleistocene antarctic ice sheet spatial and temporal variations in the sea levels of the past 20 000 years around the globe place constraints on the melting history of the major late pleistocene ice sheets the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9 000 6 000 years ago when it may have lagged behind minor melting of the antarctic ice sheet continued throughout the holocene

a method for separating antarctic postglacial rebound and ice mass balance using future icesat geoscience laser altimeter system gravity recovery and climate experiment and gps satellite data 5 3 and 19 9 mm yr 1 for postglacial rebound and ice mass trend respectively when smoothed over 250 km scales the largest source of error in the combined signals is the effect of the unknown time variable accumulation on the density of the ice column to estimate this contribution and so obtain better estimates of ice mass trend and postglacial rebound we add global positioning system gps measurements of vertical velocities as additional constraints using an empirical relation between the errors in postglacial rebound and ice mass trend that result from the unknown density variation within the ice column we are able to solve for all three unknowns in the problem ice mass trend postglacial rebound and the snow compaction trend the addition of a plausible distribution of gps measurements reduces the errors in estimates of postglacial rebound and ice mass trend to 3 4 and 15 9 mm yr 1 respectively index terms 1863 hydrology

a data calibrated distribution of deglacial chronologies for the north american ice complex from glaciological modeling article i nfo past deglacial ice sheet reconstructions have generally relied upon discipline specific constraints with no at tention given to the determination of objective confidence intervals reconstructions based on geophysical inversion of relative sea level rsl data have the advantage of large sets of proxy data but lack ice mechanical constraints conversely reconstructions based on dynamical ice sheet models are glaciologically self consistent but depend on poorly constrained climate forcings and sub glacial processes as an example of a much better constrained methodology that computes explicit error bars we present a dis tribution of high resolution glaciologically self consistent deglacial histories for the north american ice com plex calibrated against a large set of rsl marine limit and geodetic data the history is derived from ensemble based analyses using the 3d mun glacial systems model and a high resolution ice margin chronol ogy derived from geological and geomorphological observations isostatic response is computed with the vm5a viscosity structure bayesian calibration of the model is carried out using markov chain monte carlo methods in combination with artificial neural networks trained to the model results the calibration provides a posterior distribution for model parameters and thereby modeled glacial histories given the observational data sets that takes data uncertainty into account final ensemble results also account for fits between com puted and observed strandlines and marine limits given the model including choice of calibration parameters input and constraint data sets and vm5a earth rhe ology we find the north american contribution to mwp1a was likely between 9 4 and 13 2 m eustatic over a 500 year interval this is more than half of the total 16 to 26 m meltwater pulse over 500 to 700 years with lower values being more probable indicated by the barbados coral record fairbanks 1989 peltier and fairbanks 2006 if one assumes a 5 meter living range for the acropora palmata coral 20 ka ice volume for north america was likely 70 1 2 0 m eustatic or about 60 of the total contribution to eustatic sea level change we suspect that the potentially most critical unquantified uncertainties in our analyses are those related to model structure especially climate forcing deglacial ice margin chronology and earth rheology

ice flow of the antarctic ice sheet we present a reference comprehensive high resolution digital mosaic of ice motion in antarctica assembled from multiple satellite interferometric synthetic aperture radar data acquired during the international polar year 2007 to 2009 the data reveal widespread patterned enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent this view of ice sheet motion emphasizes the importance of basal slip dominated tributary flow over deformation dominated ice sheet flow redefines our understanding of ice sheet dynamics and has far reaching implications for the reconstruction and prediction of ice sheet evolution

rates of southeast greenland ice volume loss from combined icesat and aster observations 1 repeat satellite laser altimetry is critical for observing the rapidly changing mass balance of the greenland ice sheet however sparse sampling and high surface slopes over rapidly thinning coastal outlet glaciers may result in underestimation of mass loss here we supplement icesat derived surface elevation changes with differenced aster digital elevation models of outlet glaciers in southeastern greenland the region with the largest concentrated change in outlet glacier mass loss we estimate a 2002 2005 regional volume loss rate of 108 km3 yr our results are consistent with drainage scale grace and mass budget estimates when differences in observation periods are taken into account the two largest glaciers kangerdlugssuaq and helheim account for only 28 of the mass loss illustrating the combined importance of smaller glaciers and the need for complete observational coverage additionally we find that rapid concentrated thinning within the outlets represents a small contribution to the total volume change compared to dispersed inland thinning

retreat of the east antarctic ice sheet during the last glacial termination the east antarctic ice sheet retreated at the end of the last glacial period terrestrial and marine data suggest that the retreat began 14 000 years ago indicating that the east antarctic ice sheet probably did not contribute to meltwater pulse 1a 14 700 years ago

the march 25 1998 antarctic plate earthquake the march 25 1998 antarctic plate earthquake mw 8 1 occurred 250 km from the nearest plate boundary in oceanic lithosphere with an age of 35 55 my analysis of aftershock patterns shows that the earthquake ruptured a fault or series of strike slip fault segments nearly 300 km long the strike of the fault s is nearly perpendicular to the north south trending fossil fracture zones which are the most marked bathymetric features of this region moment release during the mainshock was concentrated in two large subevents clearly visible in the teleseismic body wave waveforms modeling of these body waves using a finite fault source places the first of the two subevents near the point of rupture initiation on the eastern end of the fault with the second large subevent occurring 220 280 km to the west the two pulses of moment release are found to be separated in time by 65 s comparison of the relative s wave amplitudes of the first and second pulses suggests that a rotation of the focal mechanism by 10 occurred between the two subevents

sea level changes at the lgm from ice dynamic reconstructions of the greenland and antarctic ice sheets during the glacial cycles abstract new experiments were performed with three dimensional thermomechanical models of the greenland and antarctic ice sheets to simulate their behaviour during the glacial cycles to reconstruct their thickness and extent at the last glacial maximum lgm and to estimate their glacio eustatic contribution to the global sea level stand the calculations used improved ice dynamic and isostatic treatments updated datasets on higher grid resolutions and refined climatic treatments based on newly calibrated transfer functions between ice core records and climatic perturbations results are discussed from a reference run with standard parameters that is compared with available glacial geological observations and from a series of sensitivity experiments focusing on isostatic adjustment thermomechanical coupling climatic forcing mass balance changes and basal melting rates and viscosity changes of antarctic ice shelves for the antarctic ice sheet we find that volume changes are closely linked with grounding line changes of the west antarctic ice sheet at the lgm the grounding line extended close to the continental shelf break almost everywhere ice over central east antarctica was generally thinner than today and varied mainly in accordance with accumulation fluctuations for the greenland ice sheet melting is important only during interglacial periods and the most sensitive period concerns the size of the ice sheet during the eemian at the lgm the greenland ice sheet extended beyond the present coastline to cover at least the inner continental shelf and thinned by up to several hundred meters in central areas for a plausible range of parameters the experiments indicate that at the time of maximum sea level depression 21 kyr bp the antarctic ice sheet contributed 14 18 m to the sea level lowering and the greenland ice sheet 2 3 m significantly less than the older climap reconstructions whereas both ice sheets were at 21 kyr bp close to their maximum extent the experiments also indicate that their maximum volumes were reached only by 16 5 kyr bp greenland and 10 kyr bp antarctica equal to an additional sea level lowering of respectively 0 4 and 3 7 m holocene retreat was essentially complete by 5 kyr bp in greenland but is found to still continue today in west antarctica before reversing to growth during the next millenium the models were found to reproduce gross features of the ice sheet s history since the lgm in reasonably good agreement with available glacial geological data although observational control on ice thickness changes remains very limited

a 3 d coupled ice sheet sea level model applied to antarctica through the last 40 ky abstract we present results from a three dimensional ice sheet shelf model of antarctica coupled to a gravitationally self consistent global sea level model that incorporates maxwell viscoelastic deformation of the solid earth the coupled model captures complex post glacial changes in sea level associated with the gravitational deformational and rotational effects of the evolving surface mass ice plus ocean load over the global ocean including at the grounding lines of marine based ice the simulations are initiated at 40 ka and we focus on ice distributions and sea levels from the last glacial maximum to present our results extend and confirm the key conclusions of earlier work using a simplified 1 d ice sheet model by demonstrating that the sea level coupling has a significant stabilizing influence on marine ice sheet grounding lines the feedback of sea level changes into the ice sheet model acts to slow down the retreat and advance of the grounding line relative to simulations in which the full coupling is not incorporated differences in ice thickness between these simulations can reach 1 km close to the grounding line finally we perform preliminary comparisons of our results to relative sea level rsl histories and gps derived present day uplift rates at sites near the margins of antarctica we find that the coupling improves fits to uplift rates in several regions and that the rsl predictions of the coupled model yield a fit to the observations that is comparable to recent uncoupled simulations in which the underlying earth model was varied to obtain a best fit to the rsl histories

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

joint inversion estimate of regional glacial isostatic adjustment in antarctica considering a lateral varying earth structure esa stse project regina a major uncertainty in determining the mass balance of the antarctic ice sheet from measurements of satellite gravimetry and to a lesser extent satellite altimetry is the poorly known correction for the ongoing deformation of the solid earth caused by glacial isostatic adjustment gia although much progress has been made in consistently modelling the ice sheet evolution throughout the last glacial cycle as well as the induced bedrock deformation caused by these load changes forward models of gia remain ambiguous due to the lack of observational constraints on the ice sheet s past extent and thickness and mantle rheology beneath the continent as an alternative to forward modelling gia we estimate gia from multiple space geodetic observations grace envisat icesat and gps making use of the different sensitivities of the respective satellite observations to current and past surface mass ice mass change and solid earth processes we estimate gia based on viscoelastic response functions to disc load forcing we calculate and distribute the viscoelastic response functions according to estimates of the variability of lithosphere thickness and mantle viscosity in antarctica we compare our gia estimate with published gia corrections and evaluate its impact in determining the ice mass balance in antarctica from grace and satellite altimetry particular focus is applied to the amundsen sea sector in west antarctica where uplift rates of several cm yr have been measured by gps we show that most of this uplift is caused by the rapid viscoelastic response to recent ice load changes enabled by the presence of a low viscosity upper mantle in west antarctica this paper presents the second and final contribution summarizing the work carried out within a european space agency funded study regina www regina science eu

predictions of secular geoid changes from late pleistocene and holocene antarctic ice ocean mass imbalance summary estimates on ice volume changes in antarctica from both contemporary mass imbalance during the last hundred to thousand years and ice volume changes during the last glacial cycles are difficult to obtain future satellite gravity missions monitoring secular changes in gravity as a proxy of mass changes of the antarctic ice sheet will therefore provide an additional important constraint on the antarctic ice sheet history we assess the contributions from both past ice volume changes during the last glacial cycles and present ice imbalances over antarctica using a variety of published ice models model predictions of secular changes of the geoid anomaly based on plausible mantle viscosity profiles enable us to discuss the importance of past and present ice volume changes and their characteristic signatures while uncertainties arising from the viscosity profile are of secondary importance for model predictions of the secular change of the geoid anomaly we expect significant bias of the observed signal from uncertainties in the timing of the end of deglaciation which is in agreement with previous studies hence the benefit of inferring present day antarctic ice imbalance from satellite gravity missions will depend on improvements to ice models for the last glacial cycle

rapid bedrock uplift in the antarctic peninsula explained by viscoelastic response to recent ice unloading abstract since 1995 several ice shelves in the northern antarctic peninsula have collapsed and triggered ice mass unloading invoking a solid earth response that has been recorded at continuous gps cgps stations a previous attempt to model the observation of rapid uplift following the 2002 breakup of larsen b ice shelf was limited by incomplete knowledge of the pattern of ice unloading and possibly the assumption of an elastic only mechanism we make use of a new high resolution dataset of ice elevation change that captures ice mass loss north of 66 s to first show that non linear uplift of the palmer cgps station since 2002 cannot be explained by elastic deformation alone we apply a viscoelastic model with linear maxwell rheology to predict uplift since 1995 and test the fit to the palmer cgps time series finding a well constrained upper mantle viscosity but less sensitivity to lithospheric thickness we further constrain the best fitting earth model by including six cgps stations deployed after 2009 the larissa network with vertical velocities in the range 1 7 to 14 9 mm yr this results in a best fitting earth model with lithospheric thickness of 100 140 km and upper mantle viscosity of 6 10 17 2 10 18 pa s much lower than previously suggested for this region combining the larissa time series with the palmer cgps time series offers a rare opportunity to study the time evolution of the low viscosity solid earth response to a well captured ice unloading event

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

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