sustained increase in ice discharge from the amundsen sea embayment west antarctica from 1973 to 2013 we combine measurements of ice velocity from landsat feature tracking and satellite radar interferometry and ice thickness from existing compilations to document 41 years of mass flux from the amundsen sea embayment ase of west antarctica the total ice discharge has increased by 77 since 1973 half of the increase occurred between 2003 and 2009 grounding line ice speeds of pine island glacier stabilized between 2009 and 2013 following a decade of rapid acceleration but that acceleration reached far inland and occurred at a rate faster than predicted by advective processes flow speeds across thwaites glacier increased rapidly after 2006 following a decade of near stability leading to a 33 increase in flux between 2006 and 2013 haynes smith pope and kohler glaciers all accelerated during the entire study period the sustained increase in ice discharge is a possible indicator of the development of a marine ice sheet instability in this part of antarctica key points sustained ase mass flux increase 77 since 1973 thwaites accelerated by 33 during the last 6 years speed changes are pervasive and rapid major implications for ice flow modeling 2014 american geophysical union all rights reserved

surface velocity and mass balance of ice streams d and e west antarctica over 75 000 surface velocity measurements are extracted from sequential satellite imagery of ice streams d and e to reveal a complex pattern of flow not apparent from previous measurements horizontal and vertical strain rates calculated from surface velocity indicate that the bed experiences larger basal shear where the surface of these ice streams is rougher ten airborne radar profiles and one surface based radar profile of ice thickness make possible the calculation of mass balance for longitudinal sections of each ice stream improved data collection methods increase data density substantially reducing random errors in velocity however systematic errors continue to limit the ability of the flux differencing technique used here to resolve local variations in mass balance nevertheless significant local variations in mass balance are revealed while overall ice streams d and e are in approximate equilibrium an earlier estimate of the net mass balance for ice stream d is improved

acceleration and spatial rheology of larsen c ice shelf antarctic peninsula the disintegration of several antarctic peninsula ice shelves has focused attention on the state of the larsen c ice shelf here we use satellite observations to map ice shelf speed from the years 2000 2006 and 2008 and apply inverse modeling to examine the spatial pattern of ice shelf stiffness results show that the northern half of the ice shelf has been accelerating since 2000 speeding up by 15 between 2000 and 2006 alone the distribution of ice stiffness exhibits large spatial variations that we link to tributary glacier flow and fractures our results reveal that ice down flow from promontories is consistently softer with the exception of churchill peninsula where we infer a stabilizing role for marine ice we conclude that although larsen c is not facing imminent collapse it is undergoing significant change in the form of flow acceleration that is spatially related to thinning and fracture copyright 2011 by the american geophysical union

warm ocean is eroding west antarctic ice sheet 1 satellite radar measurements show that ice shelves in pine island bay have thinned by up to 5 5 m yr 1 over the past decade the pattern of shelf thinning mirrors that of their grounded tributaries the pine island thwaites and smith glaciers and ocean currents on average 0 5 c warmer than freezing appear to be the source the synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini and the drawdown of grounded ice shows that antarctica is more sensitive to changing climates than was previously considered

tidally driven stick slip motion in the mouth of whillans ice stream antarctica we show that the ice plain in the mouth of whillans ice stream formerly ice stream b antarctica moves by stick slip motion during a spring tide period rapid motions regularly occur near high tide and during falling tide this correlation is weaker during a neap tide period when the tidal magnitudes are less precise timing of these motion events suggests that they propagate through the region with a mean velocity of 88 ms 1 we hypothesize that this speed is associated with the propagation of shear waves through a wet subglacial till motion events are also seen on more smoothly flowing floating ice event delays are very short between grounded and floating stations suggesting the events propagate through the ice shelf as an elastic wave we further hypothesize the events are caused by the interaction of a sticky bed the accumulation of stored elastic strain through the compression of ice by upstream inflow and tidal forcing motion events seem to be triggered either by reduction of vertical normal stresses at high tide or by the increase of shear stresses from sub shelf ocean currents during falling tide event magnitudes are not related to the length of the preceding quiescent period suggesting significant viscous dissipation within the till

estimation of arctic glacier motion with satellite l band sar data offset fields between pairs of jers 1 satellite sar data acquired in winter with 44 days time interval were employed for the estimation of arctic glacier motion over svalbard novaya zemlya and franz josef land the displacement maps show that the ice caps are divided into a number of clearly defined fast flowing units with displacement larger than about 6 m in 44 days i e 50 m year the estimated error of the jers 1 offset tracking derived displacement is on the order of 20 m year occasionally azimuth streaks related to auroral zone ionospheric disturbances were detected and dedicated processing steps were applied to minimize their influence on the estimated motion pattern our analysis demonstrated that offset tracking of l band sar images is a robust and direct estimation technique of glacier motion the method is particularly useful when differential sar interferometry is limited by loss of coherence i e for rapid and incoherent flow and large acquisition time intervals between the two sar images the jers 1 results obtained using sar data acquired by a satellite operated until 1998 raise expectations of l band sar data from the alos satellite launched in early 2006

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

tributaries of west antarctic ice streams revealed by radarsat interferometry interferometric radarsat data are used to map ice motion in the source areas of four west antarctic ice streams the data reveal that tributaries coincident with subglacial valleys provide a spatially extensive transition between slow inland flow and rapid ice stream flow and that adjacent ice streams draw from shared source regions two tributaries flow into the stagnant ice stream c creating an extensive region that is thickening at an average rate of 0 49 meters per year this is one of the largest rates of thickening ever reported in antarctica

flow of glaciar moreno argentina from repeat pass shuttle imaging radar images comparison of the phase correlation method with radar interferometry high resolution radar images of glaciar moreno argentina acquired by the shuttle imaging radar c sir c on 9 and 10 october 1994 at 24 cm wavelength l band are utilized to map the glacier velocity both interferometrically and using the phase correlation method the precision of the interferometric ice velocities is 1 8 cm d 1 6 m a 1 1 the phase correlation method measures ice velocity with a precision of 14 cm d 1 50 m a 1 with image data at a 6 m sample spacing acquired 1 day apart averaged strain rates are measured with a precision of 10 4 d 1 at a 240 m sample spacing with the phase correlation method and 10 5 d 1 with radar interferometry the phase correlation method is less precise than radar interferometry but it performs better in areas of rapid flow is more robust to temporal changes in glacier scattering and measures the glacier velocity in two dimensions with only one image pair using this technique we find that glaciar moreno flows at 400 m a 1 in the terminal valley and 800 m a 1 at the calving front in agreement with velocities recorded a decade ago assuming steady state flow conditions the vertical strain rates measured by sir c are combined with prior data on mass ablation to estimate the glacier thickness and ice discharge the calculated discharge is 0 6 0 2 km3 ice a 1 at 300 m elevation and 1 1 0 2 km3 ice a 1 at the equilibrium line elevation 1150 m which yields a balance accumulation of 6 1m ice a 1

northern larsen ice shelf antarctica further retreat after collapse changes of larsen ice shelf antarctica and the surrounding glaciers after its collapse in 1995 were investigated using satellite radar imagery with emphasis onchanges in the glaciers which previously nourished the ice shelf north of seal nunataks the large glaciers retreated several kilometres inland of the previousgrounding line the velocity field of drygalski glacier the largest glacier in this area was mapped by means of interferograms derived from pairs of ers syntheticaperture radar images from 1995 and 1999 the main part of the glacier showed significant acceleration of flow over these 4 years with an increase of veocity upto three fold at the terminus similar accelerations were observed by means of interferometry on several other grounded glaciers suggesting that the removal ofice shelves could lead to an effect on eustatic sea level for larsen b the northernmost surviving part of larsen ice shelf the retreat of the ice front to october2000 is documented

changes in ice dynamics elevation and mass discharge of dinsmoor bombardier edgeworth glacier system antarctic peninsula abstract the northern antarctic peninsula is one of the fastest changing regions on earth the disintegration of the larsen a ice shelf in 1995 caused tributary glaciers to adjust by speeding up surface lowering and overall increased ice mass discharge in this study we investigate the temporal variation of these changes at the dinsmoor bombardier edgeworth glacier system by analyzing dense time series from various spaceborne and airborne earth observation missions precollapse ice shelf conditions and subsequent adjustments through 2014 were covered our results show a response of the glacier system some months after the breakup reaching maximum surface velocities at the glacier front of up to 8 8 m d in 1999 and a subsequent decrease to 1 5 m d in 2014 using a dense time series of interferometrically derived tandem x digital elevation models and photogrammetric data an exponential function was fitted for the decrease in surface elevation elevation changes in areas below 1000 m a s l amounted to at least 130 15 m between 1995 and 2014 with change rates of 3 15 m a between 2003 and 2008 current change rates 2010 2014 are in the range of 1 7 m a mass imbalances were computed with different scenarios of boundary conditions the most plausible results amount to 40 7 3 9 gt the contribution to sea level rise was estimated to be 18 8 1 8 gt corresponding to a 0 052 0 005 mm sea level equivalent for the period 1995 2014 our analysis and scenario considerations revealed that major uncertainties still exist due to insufficiently accurate ice thickness information the second largest uncertainty in the computations was the glacier surface mass balance which is still poorly known our time series analysis facilitates an improved comparison with grace data and as input to modeling of glacio isostatic uplift in this region the study contributed to a better understanding of how glacier systems adjust to ice shelf disintegration

greenland ice sheet surface properties and ice dynamics from ers 1 sar imagery c band synthetic aperture radar sar imagery from the european space agency s ers 1 satellite reveals the basic zonation of the surface of the greenland ice sheet the zones have backscatter signatures related to the structure of the snowpack which varies with the balance of accumulation and melt at various elevations the boundaries of zones can be accurately located with the use of this high resolution imagery the images also reveal a large flow feature in northeast greenland that is similar to ice streams in antarctica and may play a major role in the discharge of ice from the ice sheet

velocity map of the thwaites glacier catchment west antarctica the two dimensional surface velocity of thwaites glacier west antarctica was mapped with 23 ascending and 22 descending orbit european remote sensing satellite synthetic aperture radar ers sar interferograms time range 1995 2000 the velocity map covers 175 500 square km from the amundsen coast to the southern turning point of the satellite orbit and comprises over 80 of the thwaites catchment

ice velocity determined using conventional and multiple aperture insar abstract we combine conventional interferometric synthetic aperture radar insar and multiple aperture insar mai to determine the ice surface velocity on the langjokull and hofsjokull ice caps in iceland in 1994 this approach allows the velocity of the 20 principal ice cap outlet glaciers to be fully resolved we show that mai leads to displacement estimates of finer resolution 15 versus 150 m and superior precision 5 versus 15 cm to those afforded by the alternative technique of speckle tracking using sar data acquired in ascending and descending orbits we show that ice flows within 15 of the direction of maximum surface slope across 66 of the ice caps it is therefore possible to determine ice displacement over the majority of the ice caps using a single sar image pair thereby reducing errors associated with temporal fluctuations in ice flow

new and improved determinations of velocity of ice streams b and c west antarctica measurements of velocity have been made on and next to ice streams b and c west antarctica the results are more precise than previous work and constitute a 93 increase in the number of values these velocities are used to describe the confluence of flow into the ice streams and the development of fast ice stream flow the onset of fast streaming flow occurs in many separate tributaries that coalesce down glacier into the major ice streams for those inter stream ridges that have been studied the flow is consistent with steady state along ice stream b gradients in longitudinal stress offer little resistance to the ice flow the transition from basal drag control to ice shelf flow is achieved through reduced drag at the glacier base and increased resistance associated with lateral drag velocities in the trunk of ice stream c are nearly zero but those at the up glacial head are similar to those at the head of ice stream b

changes in the west antarctic ice sheet since 1963 from declassified satellite photography comparison of declassified satellite photography taken in 1963 with more recent satellite imagery reveals that large changes have occurred in the region where an active ice stream enters the ross ice shelf ice stream b has widened by 4 kilometers at a rate much faster than suggested by models and has decreased in speed by 50 percent the ice ridge between ice streams b and c has eroded 14 kilometers these changes along with changes in the crevassing around crary ice rise imply that this region s velocity field shifted during this century

ice sheet grounding line dynamics steady states stability and hysteresis 1 the ice sheet ice shelf transition zone plays an important role in controlling marine ice sheet dynamics as it determines the rate at which ice flows out of the grounded part of the ice sheet together with accumulation this outflow is the main control on the mass balance of the grounded sheet in this paper we verify the results of a boundary layer theory for ice flux in the transition zone against numerical solutions that are able to resolve the transition zone very close agreement is obtained and grid refinement in the transition zone is identified as a critical component in obtaining reliable numerical results the boundary layer theory confirms that ice flux through the grounding line in a two dimensional sheet shelf system increases sharply with ice thickness at the grounding line this result is then applied to the large scale dynamics of a marine ice sheet our principal results are that 1 marine ice sheets do not exhibit neutral equilibrium but have well defined discrete equilibrium profiles 2 steady grounding lines cannot be stable on reverse bed slopes and 3 marine ice sheets with overdeepened beds can undergo hysteresis under variations in sea level accumulation rate basal slipperiness and ice viscosity this hysteretic behavior can in principle explain the retreat of the west antarctic ice sheet following the last glacial maximum and may play a role in the dynamics of heinrich events

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

timing of recent accelerations of pine island glacier antarctica 1 we have used interferometric synthetic aperture radar insar data and sequential landsat imagery to identify and temporally constrain two acceleration events on pine island glacier pig these two events are separated by a period of at least seven years 1987 1994 the change in discharge between two flux gates indicates that the majority of the increase in discharge associated with the second acceleration originates well inland 80 km from the grounding line an analysis indicates that changes in driving stress consistent with observed thinning rates are sufficient in magnitude to explain much of the acceleration

accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf acceleration exceeds 27 km 3 per year and ice is thinning at rates of tens of meters per year we attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf the magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change index terms 1827 hydrology glaciology 1863 1863 hydrology snow and ice 1827 3349 meteorology and atmospheric dynamics polar meteorology 6924 radio science interferometry 9310 information related to geographic region antarctica citation rignot e g casassa p gogineni w krabill a rivera and r thomas 2004 accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf geophys res lett 31 l18401 doi 10 1029 2004gl020697

mapping small elevation changes over large areas differential radar interferometry a technique that uses synthetic aperture radar sar images to measure very small 1 cm or less surface motions with good resolution 10 m over large swaths 50 km is presented along with experimental results the method could be used for accurate measurements of many geophysical phenomena including swelling and buckling in fault zones residual displacements from seismic events and prevolcanic swelling the method is based on sar interferometry where two images are made of a scene by simultaneously flying two physically separated antennas then the phases of corresponding pixels are differenced and altitude formation is deduced from some simple computation and image rectification it is also possible to use one antenna flown twice over the same scene then if the second flight exactly duplicates the track of the first an interesting possibility occurs there would be no phase changes between the images at all unless there was a physical change in the scene such as ground swelling that would alter the distance from some resolution element to the antenna since the phase changes all occur at the short carrier wavelength the basic limitation on sensitivity is only the phase noise in the system when the two imaging passes are made from flight tracks that are separated which is the case with the seasat images used here it is no longer possible to distinguish surface changes from the parallax caused by topography however with some additional computation a third image made at some other baseline may be used to remove the topography and leave only the surface changes this method was applied using seasat data to an imaging site in imperial valley california where motion effects were observed that were ascribed to the expansion of water absorbing clays phase change images of this area are shown along with associated ground truth about the presence of water problems with the technique are explored along with a discussion of future experimental possibilities on upcoming sar missions like earth observing system eos earth resources satellite ers 1 sir c and the venus imaging radar magellan

observations beneath pine island glacier in west antarctica and implications for its retreat thinning ice in west antarctica is currently contributing about 10 of the observed rise in global sea level observations obtained from an autonomous underwater vehicle operating beneath pine island glacier west antarctica reveal that the glacier was recently grounded on a transverse ridge in the sea floor but now warm sea water flows through the widening gap above the ridge thinning ice in west antarctica resulting from acceleration in the flow of outlet glaciers is at present contributing about 10 of the observed rise in global sea level1 pine island glacier in particular has shown nearly continuous acceleration2 3 and thinning4 5 throughout the short observational record the floating ice shelf that forms where the glacier reaches the coast has been thinning rapidly6 driven by changes in ocean heat transport beneath it as a result the line that separates grounded and floating ice has retreated inland7 these events have been postulated as the cause for the inland thinning and acceleration8 9 here we report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that pine island glacier was recently grounded on a transverse ridge in the sea floor warm sea water now flows through a widening gap above the submarine ridge rapidly melting the thick ice of the newly formed upstream half of the ice shelf the present evolution of pine island glacier is thus part of a longer term trend that has moved the downstream limit of grounded ice inland by 30 km into water that is 300 m deeper than over the ridge crest the pace and ultimate extent of such potentially unstable retreat10 are central to the debate over the possibility of widespread ice sheet collapse triggered by climate change11 12

three dimensional glacial flow and surface elevation measured with radar interferometry outlet glaciers which serve to drain ice from ice sheets seem to be dynamically less stable in north greenland than in south greenland1 2 3 storstrommen a large outlet glacier in northeastern greenland which surged between 1978 and 1984 ref 2 has been well studied in general neither glacier surge mechanisms nor the geographical distribution of the surges are well known conventional satellite radar interferometry can provide large scale topography models with high resolution4 and can measure the radar line of sight component of ice flow vectors5 but cannot map full vector flow fields here we present an interferometry method that combines observations from descending and ascending satellite orbits which assuming ice flow parallel to the topographic surface allows us to use the differing view angles to estimate full three dimensional surface flow patterns the accuracy of our technique is confirmed by the good agreement between our radar based flow model and in situ global positioning system gps reference data at storstrommen radar measurements such as these made regularly and at high spatial density have the potential to substantially enhance our understanding of glacier dynamics and ice sheet flow as well as improve the accuracy of glacier mass balance estimates

velocities of the smith glacier ice tongue and dotson ice shelf walgreen coast marie byrd land west antarctica velocity measurements were made for two time intervals on the smith glacier ice tongue 1973 88 and 1988 90 and three on the dotson ice shelf 1972 88 1973 88 and 1988 90 the smith glacier ice tongue velocities for the two intervals are similar near the grounding line but show a progressive increase toward the terminus in the late 1980s the dotson ice shelf velocities remained virtually constant during all three time intervals the increased velocities of the smith glacier ice tongue may be attributed to a general loss of densely packed icebergs that buttressed the terminus during the 1970s but drifted out to sea during the late 1980s the smith glacier ice tongue receded as much as 10 km between 1973 and 1988 the dotson lee shelf 5 7 km in the same time period similar observations of drifting and ca1ving were made for the adjacent thwaites glacier ice tongue the cause of the loss of ice in the region is unknown but it may have been a change in winds or a warming of the air or water during the late 1980s

mountain glaciers and ice caps around antarctica make a large sea level rise contribution the intergovernmental panel on climate change ipcc estimates that the sum of all contributions to sea level rise for the period 1961 2004 was 1 1 0 5 mm a 1 leaving 0 7

remote sensing of ice motion in antarctica a review abstract the antarctic ice sheet holds 91 of the global ice mass making it the biggest potential contributor to global sea level rise in order to evaluate the ice sheet s present and future response to global climate change detailed information about spatial and temporal ice mass dynamics is required while ice sheet surface mass balance can be estimated from regional climate models ice discharge is often determined from spaceborne measurements of ice thickness and ice motion at selected flux gates the retrieval of ice motion is not only critical for analysing the rate of ice transport into the ocean but also for investigating the spatial and temporal pattern or the driving forcings of antarctic ice flow dynamics this study provides a comprehensive review of state of the art spaceborne ice velocity measurements in antarctica based on 201 scientific papers published over the last three decades our analysis revealed a dominant interest in local and regional scale investigations yet the launch of the ers 1 2 and radarsat 1 sar satellites in the 1990s dramatically increased data coverage over the antarctic continent and enabled the first circum antarctic velocity product to be published in the late 2000s in recent years the improved imaging capabilities of landsat 8 led to a shift towards using mainly optical satellite data and enabled great advances in circum antarctic velocity mapping data from the currently operating sentinel 1 2 missions was applied in fewer studies but will play a crucial role in future ice motion studies e g as part of esa cci projects in addition we found a growing interest in high temporal resolution velocity change analyses based on the reviewed studies we moreover summarized the highly dynamic and locally variable flow pattern over the antarctic continent being in accordance with varying local and regional driving mechanisms despite the great advances in spaceborne ice velocity mapping in antarctica we report some major drawbacks and discuss future challenges and requirements to start with our study uncovered strong variations regarding the spatial availability of investigations while we found an aggregation of studies over selected glaciers we report a major lack of studies in all three antarctic sectors additionally many velocity datasets were created with strongly heterogeneous output parameters and were provided at coarse temporal resolution or at point based measurement locations only future studies should consequently aim at creating more uniform ice motion products at defined spatial and temporal coverage and resolution standards and at analysing particularly the least studied glaciers

marine ice sheet collapse potentially under way for the thwaites glacier basin west antarctica resting atop a deep marine basin the west antarctic ice sheet has long been considered prone to instability using a numerical model we investigated the sensitivity of thwaites glacier to ocean melt and whether its unstable retreat is already under way our model reproduces observed losses when forced with ocean melt comparable to estimates simulated losses are moderate 1 mm per year of sea level rise collapse in the different simulations within the range of 200 to 900 years

getz ice shelf melting response to changes in ocean forcing the large and complex getz ice shelf extends along nearly half of the west antarctic coastline in the amundsen sea and is exposed to a more variable ocean environment than most other pacific sector ice shelves ocean temperature salinity and dissolved oxygen profiles acquired near its sub ice cavity openings are used here to estimate seawater transports and meltwater fractions more complete coverage during 2000 and 2007 brackets most of the variability observed from 1994 to 2011 and yearlong records near one ice front support the use of summer profiles to determine annual basal melt rates we find area average rates of 1 1 and 4 1 m yr higher in 2007 when a larger volume of warmer deep water occupied the adjacent continental shelf and the ocean circulation was stronger results are consistent with changes in thermocline depths relative to ice shelf draft and mass transports onto the adjacent continental shelf we also calculate steady state and actual melting of 2 5 and 4 6 m yr in 2007 2008 from satellite measurements of ice flux modeled accumulation and thinning from 2003 to 2008 this implies a positive mass balance in 2000 but negative in 2007 when the getz was producing more meltwater than any of the larger slower melting or smaller faster melting ice shelves 2013 american geophysical union all rights reserved

widespread acceleration of tidewater glaciers on the antarctic peninsula over the last half century the antarctic peninsula ap has been among the most rapidly warming regions on earth this has led to increased summer snowmelt loss of ice shelves and retreat of 87 of marine and tidewater glacier fronts tidewater glacier flow is sensitive to changes in basal water supply and to thinning of the terminus and faster flow leads directly to sea level rise the flow rates of most ap tidewater glaciers have never been measured however and hence their dynamic response to the recent changes is unknown we present repeated flow rate measurements from over 300 glaciers on the ap west coast through nine summers from 1992 to 2005 we show that the flow rate increased by similar to 12 on average and that this trend is greater than the seasonal variability in flow rate we attribute this widespread acceleration trend not to meltwater enhanced lubrication or increased snowfall but to a dynamic response to frontal thinning we estimate that as a result the annual sea level contribution from this region has increased by 0 047 0 011 mm between 1993 and 2003 this contribution together with previous studies that assessed increased runoff from the area and acceleration of glaciers resulting from the removal of ice shelves implies a combined ap contribution of 0 16 0 06 mm yr 1 this is comparable to the contribution from alaskan glaciers and combined with estimated mass loss from west antarctica is probably large enough to outweigh mass gains in east antarctica and to make the total antarctic sea level contribution positive

ice sheet velocity mapping a combined interferometric and speckle tracking approach the first and second radarsat antarctic mapping missions amm 1 and 2 have now acquired interferometric synthetic aperture radar sar overmuch of the ice sheet the radarsat 24 day repeat cycle is nearly ideal for measuring slow ice motion e g 1 but application of sar interferometry is limited in faster moving areas with a 1day repeat period ers 1 2 tandem sar data are much better matched to fast motion but are not always available fortunately several authors have demonstrated the ability to measure velocity in fast moving areas by tracking sar speckle from image to image which works well even in the absence of visible features while these estimates have intrinsically lower resolution and poorer accuracy than direct phase measurements they serve well in areas where there are no data suitable for conventional interferometry this paper describes algorithms i have developed for merging interferometric and speckle tracking data from multiple swaths to form a single seamless mosaic of velocity at each point in the mosaic all the available data are combined to produce estimates of the velocity and the associated error this technique is demonstrated using radarsat data collected over lambert glacier antarctica during amm 1 and 2

acceleration of pine island and thwaites glaciers west antarctica recent satellite investigations revealed that in the 1990s the grounding line of pine island and thwaites glaciers west antarctica retreated several km the ice surface on the interior of the basins lowered 10 cm a 1 and pine island glacier thinned 1 6 m a 1 these observations however were not sufficient to determine the cause of the changes here we present satellite radar interferometry data that show the thinning and retreat of pine island glacier are caused by an acceleration of ice flow of about 18 2 in 8 years thwaites glacier maintained a nearly constant flow regime at its center but widened along the sides and increased its 30 15 mass deficit by another 4 in 4 years the combined mass loss from both glaciers if correct contributes an estimated 0 08 0 03 mm a 1 global sea level rise in 2000

surface velocity and ice discharge of the ice cap on king george island antarctica glaciers on king george island antarctica have shown retreat and surface lowering in recent decades concurrent with increasing air temperatures a large portion of the glacier perimeter is ocean terminating suggesting possible large mass losses due to calving and submarine melting here we estimate the ice discharge into the ocean for the king george island ice cap l band synthetic aperture radar images covering the time span january 2008 to january 2011 over king george island are processed using an intensity tracking algorithm to obtain surface velocity measurements pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data the maximum ice surface speeds reach 225 m a 1 and the total ice discharge for the analysed flux gates of king george island is estimated to be 0 720 0 428 gt a 1 corresponding to a specific mass loss of 0 64 0 38 m w e a 1 over the area of the entire ice cap 1127 km 2

dynamics and mass balance of four large east antarctic outlet glaciers this is the publisher s version also available electronically from http www ingentaconnect com

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change

cut marks and raw material exploitation in the lower pleistocene site of bell s korongo bk olduvai gorge tanzania a geometric morphometric analysis the lower pleistocene site of bell s korongo bk in olduvai gorge tanzania has been a key site for the study of the origin of human behaviour the lower archaeological levels of bk are characterized by anthropogenic activity related to the exploitation of megafauna elephant hippopotamus sivatherium and smaller game zebra wildebeest and antelopes these remains display a high frequency of cut marks the exceptional state of preservation of the bk fossil assemblage has allowed a wide range of different analyses that among other things detected the use of quartzite in butchering activities through the study of cut marks following up previous analyses this paper presents the study of a series of cut marks from the bk faunal assemblage using a 3d geometric morphometric methodological approach in order to determine the mineralogical properties of the quartzite used at the site bk cut marks are compared with experimentally produced cut marks using 9 mineralogically different quartzite types from olduvai gorge this comparative analysis provides valuable hints about the exact nature of the raw materials used in butchering activities the results presented here identify a preferential use of quartzite with a finer granular composition suggesting that hominin populations were already selecting the best raw materials for their use in specific activities 1 3 mya