Showing papers by "Robert Bindschadler published in 1993"

Greenland Ice Sheet Surface Properties and Ice Dynamics from ERS-1 SAR Imagery

Abstract: 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.

Analysis of synthetic aperture radar data collected over the southwestern Greenland ice sheet

Abstract: Analyses of the first aircraft multi-frequency, Polarimetric synthetic aperture radar (SAR) data acquired over the southwestern Greenland ice sheet are presented. Data were collected on 31 August 1989 by the Jet Propulsion Laboratory SAR using the NASA DC-8 aircraft. Along with curvilinear patterns associated with large-scale morphologic features such as crevasses, lakes and streams, frequency and polarization dependencies are observed in the P-, L-and C-band image products. Model calculations that include firn grain-size and volumetric water content suggest that tonal variations in and between the images are attributable to large-scale variations in the snow-and ice-surface characteristics, especially snow wetness. In particular, systematic trends in back-scatter strength observed at C-band across regions of changing snow wetness are suggestive of a capability to delineate boundaries between snow facies. Ice lenses and ice pipes are the speculated cause for similar trends in P-band back-scatter. Finally, comparison between SEASAT SAR data collected in 1978 and these airborne data collected in 1989 indicate a remarkable stability of surface patterns associated with the locations of supraglacial lake and stream systems.

Siple Coast Project research of Crary Ice Rise and the mouths of Ice Streams B and C, West Antarctica: review and new perspectives

Abstract: Satellite imagery is used as a basis to review and critique the results of studies at the mouths of Ice Streams Β and C and Crary Ice Rise. In many cases, these past analyses are extended by taking advantage of the broad coverage within each image. New perspectives are provided by the image data and some longstanding controversies are resolved. The grounding line is easily delineated and mapped in areas covered by imagery. Extensive areas of grounded ice with complex patterns of flow stripes are identified on the flanks of Crary Ice Rise. The imagery also allows a corrected map of surface topography in the vicinity of the Downstream Β camp. New questions are posed by hitherto unseen features. Data from the IGY traverse of the Ross Ice Shelf in 1957 are included to demonstrate that large changes have occurred in the past almost 30 years in the area upstream of Crary Ice Rise. These changes include modifications in the surface topography, elimination of crevasses and increases in the ice thickness by approximately 60 m.

Snow and ice applications of AVHRR in polar regions: report of a workshop held in Boulder, Colorado, 20 May 1992

Abstract: The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17–22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.

The detailed net mass balance of the ice plain on Ice Stream B, Antarctica: a geographic information system approach

Abstract: Field data of ice thickness, velocity and accumulation of the ice plain region of Ice Stream B, Antarctica, are organized into a geographic information system (GIS) and used to calculate the spatial pattern of net mass balance Overall, the ice plain is thickening at a rate of 013 ± 005 m a−1 Large uncertainties of the high-resolution calculations are reduced by spatial averaging, revealing a number of areas significantly out of balance Ice in the broad diverging flow field is mostly thinning but a thinner region of the ice plain which includes ice raft “a” is thickening Thickening is also indicated farther downstream on the ice plain, matching the thickening already calculated to be occurring upstream of Crary Ice Rise The patterns of net mass balance for the two major tributaries of Ice Stream Β are asymmetric, demonstrating a real difference in the current dynamics of these two tributaries

Radar studies at the mouths of Ice Streams D and E, Antarctica

Abstract: Ice thickness measurements have been carried out at the mouths of ice streams D and E, West Antarctica using a surface-based impulse radar. These studies have been undertaken as a part of the continuing effort to understand the state of the West Antarctic Ice Sheet and its response to climate change. Thickness measurements will be used in the mass balance calculation currently in progress and to better understand features in the surface topography seen at low angle sun illumination in the satellite imagery. Results show that the discharge areas of ice streams D and E are thickening by approximately one meter per year, and thus that these ice streams are likely loosing mass. Aperiodic wavelike features in the surface topography are described which pose interesting questions about migration of the grounding line and ice stream dynamics.

Snow and Ice Applications of AVHRR in Polar Regions: Report of a Workshop

Abstract: The third symposium on Remote Sensing of Snow and Ice, organized by the International Glaciological Society, took place in Boulder, Colorado, 17-22 May 1992. As part of this meeting a total of 21 papers was presented on snow and ice applications of Advanced Very High Resolution Radiometer (AVHRR) satellite data in polar regions. Also during this meeting a NASA sponsored Workshop was held to review the status of polar surface measurements from AVHRR. In the following we have summarized the ideas and recommendations from the workshop, and the conclusions of relevant papers given during the regular symposium sessions. The seven topics discussed include cloud masking, ice surface temperature, narrow-band albedo, ice concentration, lead statistics, sea-ice motion and ice-sheet studies with specifics on applications, algorithms and accuracy, following recommendations for future improvements. In general, we can affirm the strong potential of AVHRR for studying sea ice and snow covered surfaces, and we highly recommend this satellite data set for long-term monitoring of polar process studies. However, progress is needed to reduce the uncertainty of the retrieved parameters for all of the above mentioned topics to make this data set useful for direct climate applications such as heat balance studies and others. Further, the acquisition and processing of polar AVHRR data must become better coordinated between receiving stations, data centers and funding agencies to guarantee a long-term commitment to the collection and distribution of high quality data.

Monitoring of the Greenland Ice Sheet using ERS-1 synthetic aperture radar imagery

Abstract: ERS-1 Synthetic Aperture Radar (SAR) imagery is shown to be suitable for monitoring the climate of the Greenland ice sheet and for measuring changes in its marginal position. Four distinct hydrologic zones are easily recognized. Zone boundaries align closely with elevation. Seasonal changes in at least one of these zones indicate that late Winter is a better time than late Summer for the collection of images intended for long term monitoring. Subtle variations of the backscatter intensity from the highest portions of the ice sheet where melting never occurs are believed to indicate surface topography.

The First Annual West Antarctic Ice Sheet (WAIS) Science Workshop

Abstract: A compilation of abstracts presented at the workshop are presented. The goal was to answer the question, what is the future behavior and potential for rapid collapse of the West Antarctic Ice Sheet (WAIS)? The workshop was organized into four sessions corresponding to the four objectives identified as necessary to reach the WAIS workshop goal: history, current behavior, internal dynamics, and environmental interactions. Presentations were organized by their relevance to each objective, rather than by discipline.