snow megadune fields on the east antarctic plateau extreme atmosphere ice interaction large dune fields occupy more than 500 000 km 2 of the east antarctic plateau the megadunes or long wavelength surface ripples have amplitudes of only a few meters wavelengths of a few kilometers and parallel crests which can extend one hundred kilometers they occur in areas characterized by low accumulation extensively recrystallized snow and strong scattering of the microwave part of the spectrum dune crests are oriented perpendicular to the regional katabatic wind direction snow megadunes are unlikely to be formed by simple wind transport of snow particles

ice dynamics of the allan hills meteorite concentration sites revealed by satellite aperture radar interferometry the ice flow conditions of a 100 x 100 km area of victoria land antarctica were analyzed with the synthetic aperture radar sar technique the area includes a number of meteorite concentration sites in particular the allan hills ice fields regional ice flow velocities around the mid western and near western ice fields and the allan hills main ice field are shown to be 2 5 m yr 1 these sites are located on a horseshoe shaped area that bounds an area characterized by higher ice flow velocities of up to 5 m yr 1 meteorite find locations on the elephant moraine are located in this high ice flow area the sar derived digital elevation model dem shows atypical low surface slopes for antarctic conditions which are the cause for the slow ice movements numerous ice rises in the area are interpreted to cap sub ice obstacles which were formed by tectonic processes in the past the ice rises are considered to represent temporary features which develop only during warm stages when the regional ice stand is lowered ice depressions which develop in warm stages on the lee side of ice rises may act as the sites of temporary build up of meteorite concentrations which turn inoperative during cold stages when the regional ice level rises and the ice rises disappear based on a simplified ice flow model we argue that the regional ice flow in cold stages is reduced by a factor of at least 3

tide model accuracy in the amundsen sea antarctica from radar interferometry observations of ice shelf motion 1 this study assesses the accuracy of tide model predictions in the amundsen sea sector of west antarctica tide model accuracy in this region is poorly constrained yet tide models contribute to simulations of ocean heat transfer and to the removal of tidal signals from satellite observations of ice shelves we use two satellite based interferometric synthetic aperture radar insar methods to measure the tidal motion of the dotson ice shelf at multiple epochs a single difference technique that measures tidal displacement and a double difference technique that measures changes in tidal displacement we use these observations to evaluate predictions from three tide models tpxo7 1 cats2008a opt and fes2004 all three models perform comparably well exhibiting root mean square deviations from the observations of 9 cm single difference technique and 10 cm double difference technique care should be taken in generalizing these error statistics because 1 the dotson ice shelf experiences relatively small semidiurnal tides and 2 our observations are not sensitive to all tidal constituents an error analysis of our insar based methods indicates measurement errors of 7 and 4 cm for the single and double difference techniques respectively a model based correction for the effect of fluctuations in atmospheric pressure yields an 6 improvement in the agreement between tide model predictions and observations this study suggests that tide model accuracy in the amundsen sea is comparable to other antarctic regions where tide models are better constrained these methods can be used to evaluate tide models in other remote antarctic waters

calculation of ice velocities in the jakobshavn isbrae area using airborne laser altimetry abstract the ability to measure velocities of fast moving glaciers is essential to the understanding and interpretation of their dynamics and related processes this is especially important in the jakobshavn drainage basin of the greenland ice sheet where a significant portion of the ice sheet mass loss occurs and the iceberg calving rate is high in this article we present a method for using airborne laser altimetry data to determine surface velocities in portions of the jakobshavn drainage basin that have distinct elevation features by examining correlations between repeat elevation surveys the motion of these features the most distinct of which are crevasses is tracked results show that for areas with a standard deviation in elevation in excess of 1 m displacement of features can be tracked to a precision of 1 2 m and the corresponding velocities can be retrieved the maximum velocity of the jakobshavn isbrae at its calving front is found to be nearly 7 km yr 1 ice stream boundaries and flow patterns can also be observed in the derived velocity data

improving insar elevation models in antarctica using laser altimetry accounting for ice motion orbital errors and atmospheric delays abstract ice dynamics is closely related to climate change however a lack of digital elevation models dems of sufficient horizontal resolution and vertical precision has been a major issue in dynamic studies for years existing antarctic dems are derived from satellite radar and laser altimetry as well as limited terrestrial data these sparse datasets result in poor spatial resolution hundreds of metres to 1 km in this paper we propose a method for generating high accuracy and high resolution dems using interferometric synthetic aperture radar insar and ice cloud and land elevation satellite icesat laser altimetry by reducing the influence of ice motion satellite orbital errors and topographically correlated atmospheric delays a case study in the grove mountains area shows that the insar dem has a root mean square rms error of 5 9 m which is better than the radarsat antarctic mapping project ramp 21 1 m and bamber 8 5 m dems the new dem is used to calculate ice velocity over the grove mountains area where gps measurements have been collected for comparison compared to the nasa making earth system data records for use in research environments measures insar based antarctica ice velocity map ice velocity estimates from long baseline interferogram and the new dem have a smaller rms error this suggests that with the new dem baseline length is no longer a limiting factor for the accuracy of insar based ice velocity mapping

a full coverage high resolution topographic model of greenland computed from a variety of digital elevation data in this paper a new high resolution elevation model of greenland including the ice sheet as well as the ice free regions is presented it is the first published full coverage model computed with an average resolution of 2 km and providing an unprecedented degree of detail the topography is modeled from a wide selection of data sources including satellite radar altimetry from geosat and ers 1 airborne radar altimetry and airborne laser altimetry over the ice sheet and photogrammetric and manual map scannings in the ice free region the ice sheet model accuracy is evaluated by omitting airborne laser data from the analysis and treating them as ground truth observations the mean accuracy of the ice sheet elevations is estimated to be 12 13 m and it is found that on surfaces of a slope between 0 2 and 0 8 corresponding to approximately 50 of the ice sheet the model presents a 40 improvement over models based on satellite altimetry alone on coastal bedrock the model is compared with stereo triangulated reference points and it is found that the model accuracy is of the order of 25 35 m in areas covered by stereo photogrammetry scannings and between 200 and 250 m elsewhere

monitoring ice sheet behavior from space satellite remote sensing has revolutionized ice sheet research a variety of instruments sensitive to different parts of the electromagnetic spectrum take what the human eye detects as a flat white desert and provide data sets rich in scientific information image based maps of ice sheets are becoming commonplace and have become an integral component of field work more than a pretty picture the digital character of the satellite data from these instruments has become fundamental to the production of elevation motion accumulation and reflectance data sets visible imagery shows the scientist a wealth of features that offer clues to the history and current behavior of the ice sheet radar and microwave imagery provide information from beneath the surface and have been used to estimate snow accumulation rates interferometry principles have recently been applied to measure surface topography and ice motion with unparalleled precision nonimaging instruments also keep a watchful eye monitoring the ice sheet for indications of growth or shrinkage further expansion of the uses of satellite data is anticipated in the future

pine island glacier antarctica a study of the catchment using interferometric synthetic aperture radar measurements and radar altimetry we have mapped the catchment region of pine island glacier antarctica using ers 1 and ers 2 radar altimetry and synthetic aperture radar sar interferometry the radar altimeter data were converted to a digital elevation model dem using an algorithm we developed that corrects for slopes and grids the surface elevation estimates in a single step we used the dem and precise postprocessed orbital ephemerides to generate terrain corrected and geolocated complex radar imagery interferometric pairs on both ascending and descending orbits corrected by means of the dem yielded components of ice surface motion in the radar look direction where possible we combined velocity components from ascending and descending tracks to produce vector velocities elsewhere the velocity was calculated by assuming the direction of motion is down the surface slope the velocity map reveals a system of tributaries that channel ice from the basin like catchment area into the fast flowing downstream trunk of pine island glacier none of the tributaries shows a clear onset region instead the ice speed gradually increases along with a gradual decrease in driving stress along each tributary we combined the velocity data with sparse information on ice thicknesses and snow accumulation rates to calculate an approximate mass balance we find that the region is in balance within an uncertainty of 30 of the total mass throughput

observations of ice sheet motion in greenland using satellite radar interferometry we present interferometric observations of ice sheet motion in western greenland based on pairs of ers 1 synthetic aperture radar sar images these observations provide the first detailed regional view of ice motion associated with dynamically supported topography near the margin of an ice sheet the interferograms of this area are much more complicated than other interferograms of ice sheets presented to date we devote the largest part of this paper to explaining the source of the complexity in these interferograms a synthetic interferogram based on a simple model helps to illustrate the effects of different components of the ice velocity field in interferometric data and suggests a method for estimating the large scale ice velocity field from such data

airborne differential sar interferometry first results at l band in recent years differential interferometry using spaceborne synthetic aperture radar sar sensors has become an established technique for detecting and monitoring centimetre scale deformations of the earth s surface as well as glacier flows and landslides although often very efficient the use of spaceborne sar data has several drawbacks namely phase artifacts caused by atmospheric effects and very low coherence due to long data acquisition intervals and the short radar wavelength of the sensor most important current spaceborne sensors are not able to ensure flexible monitoring of critical regions airborne sensors may overcome most of the problems mentioned above but up to now the operational use of airborne differential sar interferometry has been prevented by insufficiently accurate motion compensation of the platform in this letter first results of airborne differential interferometry using the german aerospace center dlr experimental sar system e sar in the interferometric repeat pass mode are addressed this includes an analysis of long term decorrelation behavior in l band and particularly the correction of residual motion errors in heavily decorrelated interferograms a first differential interferogram of agricultural and forested areas is presented and analyzed

improving digital elevation models over ice sheets using avhrr based photoclinometry advanced very high resolution radiometer avhrr images and a radar altimetry based digital elevation model dem covering part of the northeast greenland ice stream are combined to create an improved topographic map of the area using photoclinometry in this application of photoclinometry a dem is used to establish the photometric relationship for two avhrr images of a snow surface slopes from the dem are compared with avhrr data that are filtered i e blurred to the resolution of the dem to give an empirical photometric determination this is then used to convert unfiltered avhrr data into quantitative slope measurements of the surface in the along sun direction in each image resolving features not present or poorly represented in the dem co registration of the images is based on the assumption that the two slope fields from the images describe one continuous smooth surface the combined slopes are then converted to topography in the test case the technique adds topographic details with spatial scales of 3 to 20 km a comparison of our results with airborne laser elevation profiles demonstrates that the new technique recovers most of the topography that is missed by the dem the improved topographic map reveals a ten fold increase in local surface relief over the ice stream feature and shows the presence of shallow troughs over the shear margins of the feature

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

ice velocity measurements of langjokull iceland from interferometric synthetic aperture radar insar we have computed the velocity of langjokull ice cap lic iceland using insar data acquired by the european remote sensing satellite in 1994 and an ice surface elevation model derived from a gps survey conducted in 1997 the velocity map covers 68 of the 925 km 2 of lic eight principal outlet glaciers were identified along which ice velocities increased from zero at the ice divide to a maximum of 75 m a 1 when the insar velocity dataset is compared with surface gps measurements of ice flow determined in summer 2001 there is generally good agreement suggesting interannual and seasonal stability for much of the ice cap during this period however non zero ice velocities at the termini of four of the eight glaciers surveyed suggest that these glaciers were advancing in 1994 comparison of our gps and insar velocities suggests that sudurjokull experienced elevated velocity in late february 1994 which when other studies are considered appears to be consistent with a glacier surge

estimation of erosion deposition and net volumetric change caused by the 1996 skeiðararsandur jokulhlaup iceland from synthetic aperture radar interferometry using repeat pass satellite synthetic aperture radar interferometry we develop a methodology to measure flood induced erosion and deposition and apply it to a record 1996 glacier outburst flood jokulhlaup on skei ararsandur iceland the procedures include 1 coregistration of backscatter intensity images to observe morphological differences 2 mapping of interferometric phase correlation to identify preserved and modified surfaces and 3 construction correction and differencing of pre jokulhlaup and post jokulhlaup topography procedures 1 and 2 are robust and should be widely applicable to other fluvial environments while procedure 3 is complicated by uncertainties in phase measurement baseline estimate and atmospheric effects after a correction procedure involving interpolation of digital elevation model elevation differences across low correlation areas we find 4 m of elevation change are required to calculate volumes of erosion or deposition this condition was satisfied for the 40 km2 proglacial zone of skei ararsandur where we estimate 38 106 m3 of net sediment deposition along the ice margin 2 106 m3 of net erosion in channels downstream and a total net balance of 13 106 these estimates are supported by field observations and survey data collected in 1997

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

early detection and in depth analysis of deformation phenomena by radar interferometry the spaceborne differential interferometric sar dinsar technique may play an important role in the measurement of land deformation phenomena especially in urban suburban and industrial areas in order to fully exploit its capabilities and increase its operational use this paper proposes two complementary levels of analysis the first one is a comprehensive low cost screening in order to detect unknown subsidence phenomena over large areas this analysis which provides a first estimation of deformations has to be performed using a limited set of sar images the second level includes an in depth quantitative analysis based on large image stacks which requires more image acquisition and data processing resources this type of analysis can be typically used to study deformation phenomena of special relevance where an effective support to the decision makers requires a fully quantitative estimation of deformations the two levels of analysis were proved over a test area of about 2100 km2 located in catalonia spain without any a priori information seven deformation phenomena were detected using a reduced set of interferograms furthermore the quantitative analysis of a subsidence of small spatial extent which was based on ascending and descending datasets confirmed the capability of dinsar to quantitatively assess deformation phenomena

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

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

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

positive mass balance during the late 20th century on austfonna svalbard revealed using satellite radar interferometry determining whether increasing temperature or precipitation will dominate the cryo spheric response to climate change is key to forecasting future sea level rise the volume of ice contained in the ice caps and glaciers of the arctic archipelago of svalbard is small compared with that of the greenland or antarctic ice sheets but is likely to be affected much more rapidly in the short term by climate change this study investigates the mass balance of austfonna svalbard s largest ice cap equilibrium line fluxes for the whole ice cap and for individual drainage basins were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio echo sounding these fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was 5 6 2 0 10 8 m 3 a 1 three basins in the quiescent phase of their surge cycles contributed 75 of this accumulation the remaining volume may be attributable either to as yet unidentified surge type glaciers or to increased precipitation this result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere

ice sheet motion and topography from radar interferometry both topography and motion information are present in repeat pass ers 1 interferograms over ice sheets the authors demonstrate that the topography is separable from the surface displacement field when a sequence of radar images are available if the velocity field is constant over the time span of observation the topography can be derived from differential interferograms formed from sequential observations with this measurement a pure displacement field can then be obtained by removal of the topographic contribution to the interferometric phase at each pixel further they discuss how the vertical and horizontal components of displacement affect the interferometrically derived motion field they illustrate their approach with four successive 3 day repeat ers 1 images of a flow feature in northeastern greenland

a baseline combination method for precise estimation of ice motion in antarctica differential synthetic aperture radar interferometry d insar is a powerful method for measuring surface deformation such as in studies of the earthquake cycle volcano deformation monitoring land subsidence monitoring and glaciological studies however its application to glaciological studies is limited by the lack of accurate digital elevation models dems particularly over the antarctic ice sheet previous studies on ice motion using d insar are mostly based on short baseline interferograms because these data sets are insensitive to dem errors unfortunately short baseline interferograms are often unavailable in this paper we refine the insar technique by using a combination of two interferograms to make accurate ice flow velocity measurements the refined technique is tested in the grove mountains area east antarctica ice flow velocities from the baseline combination method are in good agreement with those measured by short baseline interferograms this method is also capable of reducing phase errors by combining the appropriate data sets the reliability of the data sets is assessed by defining a baseline combination parameter and ensuring that it is less than or equal to 1 0 with this method we are able to extend the usefulness of d insar for glaciological studies

improving avhrr resolution through data cumulation for mapping polar ice sheets abstract data cumulation is a digital image processing technique in which several scenes of the same area taken under similar viewing conditions are combined into a single image of enhanced spatial and radiometric resolution this is effected by the reduction of aliasing in the along scan and along track sampling of scenes and by the reduction of noise content in the combined scene the technique hinges on two key steps accurate image coregistration to a precision significantly better than 1 pixel and cumulation of multiple image data grids derived from the individual images into a single image we report here on the development and initial results of the application of data cumulation using advanced very high resolution radiometer avhrr satellite images of the polar ice sheets the process can improve the real spatial resolution of avhrr data in the along scan direction from 1000 m to 650 m and in the along track direction from 1400 m to 700 m justifying a decrease in pixel size to about 500 m the technique is demonstrated in an image of a portion of the ross ice shelf in antarctica

a spatially adjusted elevation model in dronning maud land antarctica based on differential sar interferometry in this paper a new digital elevation model dem is derived for the ice sheet in western dronning maud land antarctica it is based on differential interferometric synthetic aperture radar sar from the european remote sensing 1 2 ers 1 2 satellites in combination with icesat s geoscience laser altimeter system glas a dem mosaic is compiled out of 116 scenes from the ers 1 ice phase in 1994 and the ers 1 2 tandem mission between 1996 and 1997 with the glas data acquired in 2003 that served as ground control using three different sar processors uncertainties in phase stability and baseline model resulting in height errors of up to 20 m are exemplified atmospheric influences at the same order of magnitude are demonstrated and corresponding scenes are excluded for validation of the dem mosaic covering an area of about 130 000 km2 on a 50 m grid independent icesat heights 2004 2007 ground based kinematic gps 2005 and airborne laser scanner data als 2007 are used excluding small areas with low phase coherence the dem differs in mean and standard deviation by 0 5 10 1 1 1 6 4 and 3 1 4 0 m from icesat gps and als respectively the excluded data points may deviate by more than 50 m in order to suppress the spatially variable noise below a 5 m threshold 18 of the dem area is selectively averaged to a final product at varying horizontal spatial resolution apart from mountainous areas the new dem outperforms other currently available dems and may serve as a benchmark for future elevation models such as from the tandem x mission to spatially monitor ice sheet elevation

single and multipolarimetric p band sar tomography of subsurface ice structure in this paper first results concerning the characterization of the subsurface of ice sheets and glaciers through single and multipolarization synthetic aperture radar sar tomography tomosar are illustrated to this aim the processing of data acquired in the framework of the european space agency icesar 2012 campaign is discussed icesar 2012 was conceived so as to support the secondary objectives of the future earth explorer mission biomass which will be a sar instrument with media penetration capabilities due to the use of the p band frequency in this regard a tomographic study of ice was motivated by the fact that cryospheric remote sensing is of fundamental importance in order to understand more in depth the morphology and the dynamic processes regulating ice sheets the main objective of the tomographic experiment of the campaign herein discussed was indeed to assess the capability of p band sar to retrieve any information about ice subsurface structure imaging has been achieved through tomosar techniques applied to airborne multibaseline data acquired in the southwest of greenland different imaging approaches are compared and the main results achieved are presented it is found that scattering in the upper layers of glacial subsurface can be achieved up to an extent of about 20 60 m conditional on the different types of glaciological zone observed moreover clear morphological structures have been found beneath the ice surface at one of the investigated sites

synthetic aperture radar interferometry coherence analysis over katmai volcano group alaska the feasibility of measuring volcanic deformation or monitoring deformation of active volcanoes using space borne synthetic aperture radar sar interferometry depends on the ability to maintain phase coherence over appropriate time intervals using ers 1 c band 5 66 cm sar imagery we studied the seasonal and temporal changes of the interferometric sar coherence for fresh lava weathered lava tephra with weak water reworking tephra with strong water reworking and fluvial deposits representing the range of typical volcanic surface materials in the katmai volcano group alaska for interferograms based on two passes with 35 days separation taken during the same summer season we found that coherence increases after early june reaches a peak between the middle of july and the middle of september and finally decreases until the middle of november when coherence is completely lost for all five sites fresh lava has the highest coherence followed by either weathered lava or fluvial deposits these surfaces maintain relatively high levels of coherence for periods up to the length of the summer season coherence degrades more rapidly with time for surfaces covered with tephra for images taken in different summers only the lavas maintained coherence well enough to provide useful interferometric images but we found only a small reduction in coherence after the first year for surfaces with lava measurement of volcanic deformation is possible using summer images spaced a few years apart as long as the surface is dominated by lavas our studies suggest that in order to make volcanic monitoring feasible along the aleutian arc or other regions with similar climatic conditions observation intervals of the satellite with c band sar should be at least every month from july through september every week during the late spring early summer or late fall and every 2 3 days during the winter

analyzing yengisogat glacier surface velocities with alos palsar data feature tracking karakoram china little is known about the detailed behavior of glaciers in the karakoram mountains advanced land observing satellite alos phased array type l band synthetic aperture radar palsar data were used to obtain the surface velocity of the yengisogat glacier in the karakoram mountains four alos palsar data sets with 46 days temporal baseline acquired from 2007 to 2009 covered all four seasons and were used to extract the offset fields and estimate annual average surface velocity based on seasonal velocities for the alos palsar data the synthetic aperture radar sar feature tracking procedures within the gamma software were utilized instead of sar interferometry because of low coherence in case of fast moving glaciers or large time intervals between the image acquisitions the accuracy of the measurements is discussed and the measurements were consistent with previous results from optical imagery feature tracking it was revealed that the south tributaries contributed to the main flow of the glacier with the glacier surface velocities of the south tributaries moving more rapidly than the north tributaries this was mainly attributed to the effect of the glacier s aspect in the glacier long term development point of view seasonal and spatial variations of the glacier surface velocity imply that the tributary south skamri glacier is probably surging this has previously been mentioned by some researchers such as copland et al the equilibrium line altitude was found to be at about 5 000 m a s l for south tributaries estimated from the surface velocity distribution along the glacier centerline

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

estimation of the surface velocity field of the aletsch glacier using multibaseline airborne sar interferometry this paper presents a methodology to process airborne interferometric synthetic aperture radar sar data to measure surface velocity fields svfs of temperate glaciers and applies it to data acquired over the aletsch glacier the first part of this paper deals with the main limitation in airborne interferometric sar to retrieve reliable interferometric products namely the existence of the so called residual motion errors inaccuracies on the order of a few centimeters in the navigation system an extended multisquint approach is proposed for their estimation in the case of nonstationary scenes the second part of this paper expounds an efficient methodology to derive svfs with airborne systems where the line of sight displacement is estimated using differential interferometry and the along track component by estimating the azimuth coregistration offsets the necessary steps to finally obtain the 3 d svf are also presented as well as the possibility of combining different acquisition geometries airborne interferometric sar data acquired by the experimental sar system of the german aerospace center over the aletsch glacier located in the swiss alps are used to evaluate the performance of the proposed approach the motion of the corner reflectors deployed in the scene is retrieved with an accuracy between 1 and 5 cm day using l band data

insar observations of ice elevation and velocity fluctuations at the flade isblink ice cap eastern north greenland 1 the 8500 km2 flade isblink ice cap fiic 81 15 n 15 0 w is the largest ice cap in greenland we use repeat pass interferometric synthetic aperture radar insar techniques to investigate the form and flow of the fiic european remote sensing satellite ers 1 and ers 2 data acquired in winter 1996 were used to form a 100 m resolution digital elevation model dem which we constrained using ice cloud and elevation satellite icesat laser altimeter elevation measurements from 2007 this insar dem was used to isolate the phase due to motion from seven ers tandem 1 day pairs of sar scenes acquired between 15 august 1995 and 7 february 1996 to produce one wintertime and two summertime velocity maps five of the eight major outlet glaciers draining the fiic are marine terminating and two terminate at a lake margin a maximum ice velocity of 581 m yr 1 was observed in mid august 1995 six of the eight major outlet glaciers exhibit seasonal velocity variations between late summer and winter and flow speeds vary by up to 20 over a 10 day period in august 1995 our findings show that while marine terminating glaciers flow faster than land terminating glaciers there is no simple relationship between glacier type and seasonality of ice motion

measurement of glacier geophysical properties from insar wrapped phase a method is presented for calculating longitudinal glacier strain rates directly from the wrapped phase of an interferometric synthetic aperture radar insar interferogram assuming the ice flow path is known this technique enables strain rates to be calculated for scenes lacking any velocity control points or areas within a scene where the phase is not continuously unwrappable from a velocity control point the contributions to the error in the estimate of the strain rate are evaluated and recommendations for appropriate sar and insar parameters are presented an example using radarsat 1 insar data of an east antarctic ice stream demonstrates the technique for calculating longitudinal strain rate profiles and estimating tensile strength of ice 186 215 kpa from locations of crevasse initiation the strain rate error was found to be 17 corresponding to a tensile strength of ice error of 5 3

interferometric radar observations of glaciares europa and penguin hielo patagonico sur chile repeat pass l band interferometric synthetic aperture radar insar data for part of hielo patagonico sur chile were collected by the space shuttle based spaceborne imaging radar c sir c over a 4 day span in october 1994 three co registered complex sar images are used to generate phase coherence maps a digital elevation model dem and an ice velocity map the phase coherence maps indicate low coherence in the 5 15 km approaching the termini due to large displacements ice deformation and melting however the coherence is high over nearly all of the remaining imaged icefield ice velocity precision is greater than 2 cm d 1 while the dem is good to about 25 m a flow divide between two of the glaciers is mapped by locating a narrow band of near zero ice velocity horizontal ice surface velocity profiles calculated along flowlines show there is a high degree ofspatial variability reaching a peak value of 5 5 m d 1 located 3 5 km from the terminus of glaciar europa longitudinal strain rates along the center lines calculated from these velocities at the locations of the initiation of crevassing are used to compute the tensile strength of ice 169 224 kpa

is there a single surge mechanism contrasts in dynamics between glacier surges in svalbard and other regions 1 during the 1990s monacobreen a 40 km long tidewater glacier in svalbard underwent a major surge we mapped the surge dynamics using ers synthetic aperture radar images differential dual azimuth interferometry and intensity correlation tracking a series of 11 three dimensional 3 d velocity maps covering the period 1991 1997 show a months long initiation and years long termination to the surge with no indication of a surge front travelling downglacier during the surge the front of the glacier advanced 2 km the velocity and derived strain rate increased by more than an order of magnitude and maximum ice flow rates measured during 1994 were 5 m d 1 the spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed we combine these results with those published in the literature to construct a typical svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions especially those of variegated glacier in alaska the strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms

topography and dynamics of austfonna nordaustlandet svalbard from sar interferometry the ice caps of nordaustlandet svalbard represent one of the largest glaciated areas outside of antarctica and greenland they demonstrate a variety of different flow regimes within a comparatively compact area we report on the first interferometrically derived elevation models and velocity visualisations of austfonna this initial investigation had three purposes to determine whether the coherence and velocity characteristics of the region permitted interferometric survey to determine the accuracy of derived elevations and to assess the possibility of investigating time variant flow of the more dynamic ice bodies using differential interferometry a trio of coherent synthetic aperture radar images from ers 1 s first ice phase was identified the images were combined to separate the topographic and velocity components of the resultant interferograms the topographic phase difference was used to produce a digital elevation model of austfonna its accuracy relative to radio echo sounding derived tie points is 8 m and its resolution 40 m we also present synoptic views of the velocity held of three of austfonna s drainage basins and comment on the extraction of useful velocity information

explosive activity and generation mechanisms of pyroclastic flows at arenal volcano costa rica between 1987 and 2001 explosive activity at arenal and associated tephra fall that has occurred over the 14 year period from 1987 2001 is described explosions have been notably variable in both frequency and size a marked decrease in both frequency and quantity of tephra fallout occurred in early 1998 until the end of 2001 grainsize distributions of cumulative tephra samples collected once a month are typically bimodal aggregation causing premature fallout of fine ash and possibly fallout from ash plumes produced by pyroclastic flows are considered responsible for the bimodality of fallout scanning electron microscopy of the glass component of tephra from single explosions show predominantly blocky and blocky fluidal clast types interpreted as being the product of vulcanian type explosions fragmentation of a mainly rigid degassed magma body and a minor molten component is inferred for these explosions pyroclastic flows were produced either associated with the larger explosions by a mechanism of column collapse 1987 1990 or unrelated to explosions by partial collapse of the crater wall 1993 1998 2000 2001 pyroclastic flow activity has migrated from west to north during the period reported pyroclastic flow deposits are variable in the quantity of juvenile material and any associated surge component large juvenile blocks were partially molten on emplacement and many have a typical cauliform texture blocks with both juvenile and lithic textures indicate that at the summit magma was in intimate contact with the pre existing edifice rather than as a simple open crater or lava pool crater wall collapse may have been promoted by the reduction in explosive activity which has increased the lava accumulation at the summit and in turn increased instability of the summit region thus although explosive activity has waned if the lava output is maintained the hazard of pyroclastic flows is likely to continue

accuracy of topographic maps derived from ers 1 interferometric radar an interferometric radar technique for topographic mapping of surfaces promises a high resolution approach to the generation of digital elevation models the authors present analyses of data collected by the synthetic aperture radar instrument on board the ers 1 satellite on successive orbits use of a single satellite in a nearly repeating orbit is attractive for reducing cost and spaceborne hardware complexity also it permits inference of changes in the surface from the correlation properties of the radar echoes the data have been reduced to correlation maps and digital elevation models the correlation maps show that temporal correlation decreases significantly with time but not necessarily at a constant well defined rate likely depending on environmental factors when correlation among passes remains high however it is possible to form digital elevation models analyses of noise expected in ers 1 interferometric data collected over alaska and the southwestern united states indicate that maps with relative errors less than 5 m rms are possible in some regions however orbit uncertainties imply that tie points are required in order to reduce absolute height errors to a similar magnitude the authors find that about 6 tie points per 40 spl times 40 km scene with 5 m rms or better height accuracy are needed to keep systematic map height errors below 5 m rms the performance of the ers 1 radar system for topographic applications though useful for a variety of regional and local discipline studies may be improved with respect to temporal decorrelation errors and absolute height acuity by modifying the orbit repeat period and incorporating precise orbit determination techniques the resulting implementation will meet many but not all objectives of a global mapping mission

seasonal and interannual ice velocity changes of polar record glacier east antarctica we present a study of seasonal and interannual ice velocity changes at polar record glacier east antarctica using ers 1 2 envisat and palsar data with d insar and intensity tracking ice flow showed seasonal variations at the front of the glacier tongue velocities in winter were 19 less than velocities during summer no significant interannual changes were detected ice velocities in the grounding zone and grounded glacier did not show clear seasonal or interannual changes the distribution of the seasonal variations suggests that the cause for the changes should be localized possible causes are seasonal sea ice changes and iceberg blocking satellite images show that the sea ice surrounding polar record glacier undergoes seasonal changes frozen sea ice in winter slowed the huge iceberg and provided increased resistance to the glacier flow the interaction between the glacier tongue iceberg and sea ice significantly influences their flow pattern

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

mapping ice shelf flow with interferometric synthetic aperture radar stacking interferometric synthetic aperture radar insar observations of ice shelf flow contain ocean tide and atmospheric pressure signals a model based correction can be applied but this method is limited by its dependency upon model accuracy which in remote regions can be uncertain here we describe a method to determine two dimensional ice shelf flow vectors independently of model predictions of tide and atmospheric pressure by stacking conventional and multiple aperture insar mai observations of the dotson ice shelf west antarctica in this way we synthesize a longer observation period which enhances long period flow displacement signals relative to rapidly varying tide and atmospheric pressure signals and noise we estimate the error associated with each component of the velocity field to be 22ma 1 which could be further reduced if more images were available to stack with the upcoming launch of several satellite missions offering the prospect of regular short repeat sar acquisitions this study demonstrates that stacking can improve estimates of ice shelf flow velocity

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

textural development in sulfide matrix ore breccias in the aguablanca ni cu deposit spain revealed by x ray fluorescence microscopy abstract the intrusion hosted ni cu sulfide deposit at aguablanca in south western spain contains a high proportion of ores in the form of sulfide matrix ore breccias these are polymict comprising autoliths and xenoliths in sulfide rich and or sulfide poor matrices inclusion lithologies include calc silicate skarn rocks from the adjacent marbles ultramafic and mafic cumulates and remelted and recrystallized mafic rocks containing spinifex like textures breccia textures have been investigated at mm to cm scale using desk top and synchrotron based microbeam xrf mapping which reveal a number of distinctive common features disaggregation of inclusions into adjacent sulfide along original silicate grain boundaries complex reverse and oscillatory zoning in cr content of clinopyroxene grains within sulfide and inside inclusions narrow reaction rims between country rock clasts and enclosing silicates and preferential disposition of pyroxene crystals within pyrrhotite pentlandite aggregates original mss relative to inclusion poor chalcopyrite the observed range of textures is explained by a model of percolation of molten sulfide through a pre existing silicate matrix intrusion breccia preferentially displacing a cotectic or eutectic plagioclase pyroxene melt the process is analogous to that believed to have formed interspinifex ore in komatiite hosted deposits and also to that responsible for superficially similar sulfide matrix ore breccias at voisey s bay the preserved range of textures is interpreted as being due to late stage gravity driven percolation of sulfide liquid from above into a pre existing partially molten intrusion breccia this intrusion breccia itself may have been emplaced into the neck of the aguablanca stock in the waning stages of magma flow

estimation and analysis of the surface velocity field of mountain glaciers in muztag ata using satellite sar data muztag ata is a mountain known as the father of glaciers in the west of china however its glacier flow pattern has never been studied in this paper the velocity of mountain glaciers on muztag ata is mapped by two methods insar and offset tacking using sar data this map provides a detailed view of the features of glacier motion on muztag ata a special effort was also made to assess the accuracy of the glacier velocity estimates to ensure the accuracy of the derived results the validation of the results was conducted over two glaciers saliymek glacier and kuksay glacier the two methods yielded similar results that agree well with each other the patterns of glacier velocity on muztag ata suggest that mountain topography westerly winds and the monsoon have a strong influence our results show that motion of glaciers in the southern and western regions of muztag ata is faster than that in the northern and eastern regions eleven glaciers were identified along which glacier velocities exhibited distinctive behavior in terms of the spatial variability of the glacier motion the occurrence of the local flow maxima and minima at consistent locations over different parts of different glaciers suggests that the subglacial topography glacier size and glacier orientation affect the overall flow patterns the velocities are very low in the surface debris cover of some glaciers which suggests debris cover has an impact on glacier motion

the integration of jers 1 and ers sar in differential interferometry for measurement of complex glacier motion complex glacier motion in the grove mountains region antarctica is measured using four pass differential synthetic aperture radar sar interferometry insar the components of the motion vector field are resolved using a 44 day separation japanese earth resources satellite 1 jers 1 insar pair and a european remote sensing satellite 1 2 ers 1 2 tandem insar pair the 44 day temporal baseline provides the sensitivity required to observe the range of ice motion around 8 10 m a 1 and the 1 day short baseline provides the best choice for glacier digital elevation model reconstruction it is remarkable that the scattering field of the jers 1 pair remained coherent over the long time interval and the interferometric fringes are clear the overall ice flow is from east to west downslope and towards lambert glacier the regional flow is obstructed by nunataks extending north south with two wide gaps two narrow glaciers flow past the nunataks and rejoin each other at the downstream end regional morphology and the resolved flow in the grove mountains area suggests that ice flow is channeled throughout this eastern flank of lambert glacier

interferometric estimation of three dimensional ice flow using ascending and descending passes satellite radar interferometry sri provides an important new tool for determining ice flow velocity interferometric measurements made from a single track direction are sensitive only to a single component of the three component velocity vector observations from along three different track directions would allow the full velocity vector to be determined a north south looking synthetic aperture radar sar could provide these observations over large portions of the globe but not over large areas of the polar ice sheets the authors develop and demonstrate a technique that allows the three component velocity vector to be estimated from data acquired along two track directions ascending and descending under a surface parallel flow assumption this technique requires that there are accurate estimates of the surface slope which are also determined interferometrically to demonstrate the technique the authors estimate the three component velocity field for the ryder glacier greenland their results are promising although they do not have yet ground truth data with which to determine the accuracy of their estimates

inland thinning of pine island glacier west antarctica the pine island glacier pig transports 69 cubic kilometers of ice each year from 10 of the west antarctic ice sheet wais it is possible that a retreat of the pig may accelerate ice discharge from the wais interior satellite altimetry and interferometry show that the grounded pig thinned by up to 1 6 meters per year between 1992 and 1999 affecting 150 kilometers of the inland glacier the thinning cannot be explained by short term variability in accumulation and must result from glacier dynamics

insar observations of the 1993 95 bering glacier alaska u s a surge and a surge hypothesis time varying accelerations were observed on bagley icefield during the 1993 95 surge of bering glacier alaska u s a using repeat pass synthetic aperture radar interferometry observations were from datasets acquired during winter 1991 92 pre surge winter 1993 94 during the surge and winter 1995 96 post surge the surge is shown to have extended 110 km up the icefield from bering glacier to within 15 km or less of the flow divide acceleration and step like velocity profiles are strongly associated with an along glacier series of central phase bull s eyes with diameters of 0 5 4 km these bull s eyes are interpreted to represent glacier surface rise fall events of 3 30 cm during 1 3 day observation intervals and indicate possible migrating pockets of subglacial water we present a surge hypothesis that relates late summer climate to englacial water storage and thence to the subglacial water dynamics pressurization hydraulic jacking depressurization and migration suggested by our observations

the potential of satellite radar interferometry and feature tracking for monitoring flow rates of himalayan glaciers abstract the stagnation of himalayan glaciers will only be exacerbated by a warming climate increasing hazards associated with glacier lake development frontal recession is a poor indicator of negative balance in this region where most glaciers are debris covered but reduced glacier flow rates provide a valuable warning of stagnation in situ measurements of velocity are understandably rare and remote sensing measurements have hitherto been limited by severe topography and lack of suitable data in this paper we compare two techniques to measure flow rates in everest region glaciers firstly satellite radar interferometry sri has recently become more viable because of improved digital elevation data and precision orbit models which now allow snapshots of velocities to be retrieved from ers imagery in the mid 1990s without ground control information secondly feature tracking between synthetic aperture radar sar images is found to be successful even on the small glaciers of this region because of the patterning associated with debris cover this technique extends through the 1990s and beyond the time frame over which velocities can be measured using the examples of the khumbu glacier flowing south into nepal and the kangshung glacier flowing east into china from the everest massif we compare sri and sar feature tracking in ers images consider the errors in these techniques and examine the potential to monitor flow rates across the region the techniques are found to be highly complementary and appropriate for monitoring flow rates in this region suggesting that routine monitoring of himalayan glaciers is possible the kangshung glacier appears to sustain relatively high flow rates of up to 10 cm day which along with a convex topographic profile indicates a healthy glacier not exhibiting significant negative mass balance in comparison much of the khumbu glacier appears to have stagnated the surface velocity at gorak shep is only 20 of a field based measurement in the 1970 s and the concave surface profile confirms the downwasting associated with a debris covered glacier in recession

analysis of the 1993 95 bering glacier alaska surge using differential sar interferometry differential spaceborne radar interferometry observations of west bagley icefield are used to measure surface velocity and topography bagley icefield is the accumulation area fur bering glacier which surged in two phases from spring 1993 through summer 1905 the observations presented are based on data collected during the winter of 1992 prior to the surge and during winter 1994 while the surge was in full progress both observation intervals correspond to 3 day repeat orbit phases of the ers i c band sar this paper gives an overview of the algorithms used to derive surface velocity vector fields and topography for valley glaciers from sar images the resulting high resolution velocity data clearly show west bagley icefield accelerating from its quiescent pre surge velocity by a factor of 2 7 in response to the bering glacier surge persistence of lnterfero metric phase coherence and the relatively moderate degree of acceleration on the western arm of bagley icefield suggest that the velocity increase may have been caused by increased longitudinal stress gradients resulting from coupling to the surging main trunk of bering glacier

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

accuracy of three dimensional glacier surface velocities derived from radar interferometry and ice sounding radar measurements we present a method for analyzing the errors involved in measuring three dimensional glacier velocities with interferometric radar we address the surface parallel flow assumption and an augmented approach with a flux divergence fd term the errors in an interferometric ers 1 2 satellite radar dataset with ascending and descending orbit data covering storstrommen glacier northeast greenland are assessed the fd error assessment is carried out on airborne 60 mhz ice sounding radar data from the same area a simple model of an interferometric radar system is developed and analyzed the error sources considered include phase noise atmospheric distortions baseline calibration errors a dry snow layer and the stationary flow assumption used in differential interferometry the additional error sources in the analysis of fd errors are noise bias and unknown variations of the ice thickness and approximations of the ice flow model the example glacier is now building up following a surge the analysis shows that in the case study presented the errors are small enough to justify the use of both the estimated surface parallel flow term of the vertical velocity and the estimated fd term of the vertical velocity

studies of multibaseline spaceborne interferometric synthetic aperture radars the authors have utilized a set of seasat synthetic aperture radar sar data that were obtained in nearly repeat ground track orbits to demonstrate the performance of spaceborne interferometric sar insar systems an assessment of the topography measurement capability is presented a phase measurement error model is described and compared with the data obtained at various baseline separations and signal to noise ratios finally the implications of these results on future spaceborne insar design are discussed

topographic mapping from interferometric synthetic aperture radar observations interferometric synthetic aperture radar observations provide a means for obtaining high resolution topographic terrain maps from data acquired simultaneously at two slightly displaced antennas calculation of the three dimensional coordinates of all the points in a radar image can be made from the combination of along track slant range and interferometer fringe measurements thus the result compensates for the layover exhibited by conventional radar maps and removes the false targets generated by multiple signal paths to a given object in the scene we have derived a topographic map of a portion of the san francisco bay area utilizing data that were recorded by a radar system mounted on a nasa cv990 aircraft and processed by a general purpose digital computer this map displays the height above sea level of a region approximately 11 km by 10 km in size sampled on an 11 m pixel grid uncertainties in the estimated height result from imprecise knowledge of the observational geometry radar bandwidth limitations and finite signal to noise ratios for our system each factor contributed approximately 3 4 m to a relative rms error of about 6 m additional global errors of the order of 10 m can result from inaccurate monitoring of aircraft attitude the statistical variation of the height measurements from the ocean portion of the map which we can presume to be quite flat is 2 10 m rms which is consistent with the theoretical estimate comparison of our results with u s geological survey contour maps indicates a high degree of correlation between the two sets of altitude data

interferometric radar observations of glaciar san rafael chile interferometric radar observations of glaciar san rafael chile were collected in october 1994 by nasa s spaceborne imaging radar c sir c at both l 24 cm and c band frequency 5 6 cm with vertical transmit and receive polarization the c band data did not yield good geophysical products because the temporal coherence of the signal was significantly reduced after 24 h the l band data were however successfully employed to map the surface topography of the icefield with a 10 m uncertainty in height and measure ice velocity with a precision of 4 mm d 1 or 1 4 ma 1 the corresponding error in strain rates is 0 05 a 1 at a 30 m horizontal spacing the one dimensional interferometric velocities were subsequently converted to horizontal displacements by assuming a flow direction and complemented by feature tracking results near the calving front the results provide a comprehensive view of the ice flow dynamics of glaciar san rafael the glacier has a core of rapid flow 4 5 km in width and 3 5 in average slope surrounded by slowermoving ice not by rock ice velocity is 2 6 m d 1 or 0 95 km a 1 near the equilibrium line altitude 1200 m increasing rapidly before the glacier enters the narrower terminal valley to reach 17 5 m d 1 or 6 4 km a 1 at the calving front strain rates are dominated by lateral shearing at the glacier margins 0 4 0 7 a 1 except for the terminal valley section where longitudinal strain rates average close to 1 a 1 this spectacular longitudinal increase in ice velocity in the last few kilometers may be a fundamental feature of tidewater glaciers

estimation of ice sheet motion using satellite radar interferometry method and error analysis with application to humboldt glacier greenland satellite radar interferometry provides glaciologists with an important new tool for determining the motion and topography of large ice sheets we examine the sources of error in interferometrically derived ice motion measurements including those errors due to inaccurate estimates of the interferometric baseline several simulations are used to assess baseline accuracy in terms of tie point error and the number and distribution of tie points these results give insight into how best to select tie points and also demonstrate the level of accuracy that can be achieved examination of two representative cases likely to occur in mapping ice sheet motion leads to the conclusion that with adequate tie point information ice velocity can be measured accurately to within a few meters per year a method to correct horizontal velocity estimates for the effect of vertical displacement using surface slopes is also developed finally we estimate the single component velocity field for an area on humboldt glacier northern greenland using interferograms formed from ers i sar images we estimate that these velocity measurements are accurate to within 2 3 m year 1

synthetic aperture radar interferometry over rutford ice stream and carlson inlet antarctica we describe the calibration and interpretation of interferograms generated from ers i synthetic aperture radar single look complex sar slc images of the rutford ice stream area ground surveys provide over 100 tie points with which to optimise the interferometric baselines that separate nominally repeated satellite orbits covariant tie point errors are dealt with by constructing an error covariance matrix for the expected values of the unwrapped interferometric phases at the tie points with baseline parameters that minimise the weighted residual variance rms tie point residuals of less than i cm in slant range are obtained these are attributed to a combination of interferometric phase noise movement survey errors and inadequate slope information the image set used is inadequate for isolating the influences of topography and movement so the glaciological conclusions to be drawn are limited nevertheless the interferograms confirm that the whole of the upper 50 k m of carlson inlet flows at a speed less than a tenth of that of the neighbouring rutford ice stream also confirmed are the entry of faster moving ice into the lower reaches of carlson inlet and the position of part of the carlson inlet grounding line in general the distribution of the residuals suggests no significant differences in ice movement between 1978 and 1992 an exception is the neighbourhood of the shear margin between rutford ice stream and carlson inlet where inconsistencies between ground surveys over the periods 1984 86 and 1994 96 and interferograms from 1994 a n d 1996 suggest fluctuations in velocity of up to 10 m year 1

discovering anomalous dynamics and disintegrating behaviour in glaciers of chandra bhaga sub basins part of western himalaya using dinsar abstract glacier velocity is one of the important parameters to know about glacier dynamics its mass and health understanding glacier velocity also assists in the analysis of ice thickness ice flux and mass balance furthermore basin sub basin wise studies are helpful to understand the climate change over that region instead of monitoring individual glaciers in the current study the spatial distribution of glacier velocity is generated for the entire chandra and bhaga sub basins in the lahaul spiti district of himachal pradesh india using advanced land observing satellite 2 phased array type l band synthetic aperture radar 2 alos 2 palsar 2 differential interferometry pair images with a 14 days temporal gap the glaciers in chandra sub basin are found to have a high flow rate as compared to the glaciers in bhaga sub basin local slope and ice thickness which decrease towards the terminus in general control the movement of valley glaciers and lower movement rate is observed for most of glaciers towards the terminus frontal area however a few glaciers of bhaga sub basin demonstrate an accelerated movement in their frontal areas this irregular behaviour is also studied in this work and it is discovered that terrain slope and influx of melting water from adjacent glaciers are the major causes for such behaviour of these glaciers they are therefore prone to accelerated mass loss compared to other glaciers in the sub basin another key finding of the anomalous glacier dynamics study is the disintegrating behaviour of glaciers which is also identified by interpreting the responses of physical scattering mechanisms retrieved from glaciers using fully polarimetric alos 2 palsar 2 warming temperatures are expected to cause glacier retreat and separation of tributary glaciers from the main glacier body melt water from tributary glaciers can further accelerate glacier flow and ice melt in lower part of glacier trunk this can lead to formation of dead ice zones and disintegration of himalayan glaciers which are supported by numerous tributary glaciers therefore we expect that the loss in glacier area due to warming will be larger than the present prediction where mass loss is considered from conventional way