National Snow and Ice Data Center

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1 National Snow and Ice Data Center This data set (NSIDC-0484), part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program, provides the first comprehensive, high-resolution, digital mosaics of ice motion in Antarctica assembled from multiple satellite interferometric synthetic-aperture radar data. Data were acquired during the International Polar Year 2007 to These maps were built from spring 2009 data from the Canadian Space Agency (CSA)'s and MacDonald, Dettwiler and Associates Ltd. (MDA)'s RADARSAT-2, spring data from European Space Agency (ESA)'s Envisat Advanced Synthetic Aperture Radar (ASAR), and fall data from the Japan Aerospace Exploration Agency (JAXA)'s Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR), complemented by patches of CSA's RADARSAT-1 data from fall 2000 and ESA's Earth Remote Sensing Satellites ERS-1 and -2 data from spring Each radar instrument contributes its unique coverage and performance level. The final mosaics assemble 900 satellite tracks and more than 3,000 orbits of radar data. Data acquisitions between 2006 and 2011 are courtesy of the IPY Space Task Group. Data are available via FTP at 450 m and 900 m spacings, in both binary format (.dat) with an ENVI text header (.txt) and NetCDF. Note. These data are considered provisional pending a review by the MEaSUREs program. Once the data have been reviewed, this statement will be removed from this documentation. The generation of this data set and its scientific interpretation are discussed in the following citation. We kindly request that you acknowledge the use of this data set by referencing the following citation: Rignot, E., J. Mouginot, and B. Scheuchl Ice Flow of the Antarctic Ice Sheet, Science, Vol. 333(6048): doi /science These data are offered free of charge. You may use these data freely, provided that you cite NSIDC as the source, and provide an acknowledgment in any published papers. The following examples show how to cite the use of these data sets in a publication. List the principal investigators, year of data set release, data set title and version number, dates of the data you used (for example, March to June 2004), publisher: NSIDC, and digital media. Rignot, E., J. Mouginot, and B. Scheuchl MEaSUREs InSAR-Based Antarctica Ice Velocity Map. Boulder, Colorado USA: NASA EOSDIS Distributed Active Archive Center at NSIDC. [list dates of data used]. Category Data format Spatial coverage Spatial resolution Binary with ENVI text header NetCDF Southernmost Latitude: 90 S Northernmost Latitude: 60 S Westernmost Longitude: 180 W Easternmost Longitude: 180 E 450 m 900 m Temporal coverage and resolution Data were collected between 1996 and Projection description File naming convention File size Parameters Procedures for obtaining data Polar stereographic with true scale at 71 south antarctica_ice_velocity_[450m/900m].dat antarctica_ice_velocity_[450m/900m].nc 1300 MB (450 m) 300 MB (900 m) Ice velocity (vx, vy) Error Data are available via FTP. 1. Contacts and Acknowledgments 2. Detailed Data 3. Data Access and Tools 4. Data Acquisition and Processing 5. References and Related Publications 6. Document Information Dr. Eric Rignot University of California, Irvine Department of Earth System Science 1 von :14

2 Croul Hall Irvine, California USA Dr. Jeremie Mouginot University of California, Irvine Department of Earth System Science Croul Hall Irvine, California USA Dr. Bernd Scheuchl University of California, Irvine Department of Earth System Science Croul Hall Irvine, California USA NSIDC User Services National Snow and Ice Data Center CIRES, 449 UCB University of Colorado Boulder, CO USA phone: fax: form: Contact NSIDC User Services These data were generated through a grant from the NASA MEaSUREs program. Spaceborne Synthetic Aperture Radar (SAR) acquisitions were provided through the following data grants: ALOS PALSAR: Japan Aerospace Exploration Agency (JAXA) ENVISAT ASAR, ERS-1, ERS-2: European Space Agency (ESA) RADARSAT-1, RADARSAT-2: Canadian Space Agency (CSA) Data acquisitions between 2006 and 2011 are courtesy of the International Polar Year (IPY) Space Task Group. Figure 1. Antarctic ice velocity derived from ALOS PALSAR, Envisat ASAR, RADARSAT- 2 and ERS-1/2 satellite radar interferometry color coded on a logarithmic scale. (Rignot, Mouginot, and Scheuchl 2011) These data are available in the following formats: Binary file with ENVI text header NetCDF Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/datasets/nsidc0484_measures_antarc_vel_v01/ directory. The 00README.txt file in this directory contains additional information about the data set. Data files are stored by spatial resolution in the /450m/ and /900m/ subfolders. Each folder contains the data files listed in Table 2, where [450m/900m] denotes the corresponding spatial resolution. Example file names:.../450m/antarctica_ice_velocity_450m.dat.../900m/antarctica_ice_velocity_900m.dat 2 von :14

3 Table 2. File and Directory File antarctica_ice_velocity_[450m/900m].dat Velocity, binary file (big endian) antarctica_ice_velocity_[450m/900m]_error.dat Error estimate, binary file (big endian) antarctica_ice_velocity_[450m/900m].hdr antarctica_ice_velocity_[450m/900m]_error.hdr Header files for reading.dat files into ENVI antarctica_ice_velocity_[450m/900m].nc Velocity, NetCDF format antarctica_ice_velocity_[450m/900m]_info.txt ASCII text file with projection information Files range from approximately 350 MB to 1.4 GB. The data set spans the continent of Antarctica. Southernmost Latitude: 90 S Northernmost Latitude: 60 S Westernmost Longitude: 180 W Easternmost Longitude: 180 E Spatial Coverage Map Figure 2. Antarctic ice velocity derived from (A) PALSAR, (B) ASAR, (C) RADARSAT-2, and (D) RADARSAT-1 and ERS-1 and 2 satellite radar interferometry color coded on a logarithmic scale and overlaid on a MODIS mosaic of Antarctica. Projection is polar stereographic at 71 S secant plane. Thick black lines delineate major ice divides. (Rignot, Mouginot, and Scheuchl 2011) Spatial Resolution The velocity maps are provided at 450 m and 900 m spacings. Projection Polar stereographic with true scale at 71 S. The data used in this data set were collected between 1996 and Detailed information is provided in Section 4: Data Acquisition and Processing. These maps provide velocity data for the Antarctic Ice Sheet at 450 m and 900 m spacings. Each data point contains velocity information (meters per year) in the x and y direction as defined by the polar stereographic grid (vx and vy respectively). Error estimates for the velocity magnitude are also provided, however, these values should be used more as an indication of relative quality rather than absolute error. More information about the error estimates is provided in the Quality Assessment section as well as in Rignot, et al Parameter 3 von :14

4 Table 3. Variable Variable vx vy err Velocity in m/year in x direction Velocity in m/year in y direction Estimated error in velocity magnitude A detailed description of these data and their quality is provided in Rignot, et al., The precision of ice flow mapping varies with the sensor, the geographic location, the technique of interferometric analysis (see Section 4 for details), the time period of analysis, the repeat cycle, and the amount of data stacking. The error estimates are summarized in Table 4. The error map in Figure 3 takes into account the following error sources: Error of speckle tracking and interferometric phase analysis respectively Errors caused by ionospheric perturbations (strongest in the azimuth direction, stronger in L-band compared to C-band, stronger in the East Antarctic Ice Sheet (EAIS) compared to the West Antarctic Ice Sheet (WAIS) because ionospheric perturbations are more abundant near the magnetic pole Data stacking (reduces the error noise as the square root of the number of interferometric pairs averaged) Respective weight of each instrument in the mosaicking The total error is the square root of the sum of the independent errors squared. More details on the error estimates are provided in Rignot, et al., 2011 (supplementary online material). Table 4 provides the error in ice velocity mapping for each sensor, without data stacking, in range (Rg) and azimuth (Az). Table 4. Error in Ice Velocity Mapping (m/yr) Sensor Repeat Cycle (day) Pixel Size Speckle Tracking PhaseRg Rg (m) Az (m) Rg (m/yr) Az (m/yr) (m/yr) IonosphereAz (m/yr) Total Error (m/yr) ALOS (WAIS) ALOS (EAIS) ASAR RADARSAT RADARSAT ERS-1 and N/A 1 Figure 3. Velocity magnitude error on a linear scale color coded from 1 to greater than 16 m/yr. Thick black lines delineate major ice divides and the grounding line (Rignot, et al. 2011). Data are available via FTP. Registered users will receive notification about any product changes and new data availability. Please complete the User Registration Form to receive these notifications. Data volume 450 m spacing: 2.8 GB 900 m spacing: 0.7 GB Total volume: 3.5 GB Data are accessible using a variety of software. MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry MEaSUREs InSAR-Based Ice Velocity Maps of Central Antarctica: 1997 and von :14

5 This data set provides ice velocity information for the entire Antarctic continent, derived from a variety of satellite radar interferometry data. Two techniques of interferometric analysis were used to generate the maps: 1. Speckle tracking in both along (azimuth) and across (range) track directions Calculation of two dimensional offsets in amplitude imagery 2. Combinations of (range) interferometric phases along two independent tracks Combination of interferometric phases of two independent tracks to retrieve the surface flow vector In both cases, surface parallel flow is assumed, a conventional approach for ice sheets. Ice velocity information for the Antarctic Ice Sheet was derived using satellite synthetic aperture radar interferometry (InSAR) data from spring 2009 data from the Canadian Space Agency (CSA)'s and MacDonald, Dettwiler and Associates Ltd. (MDA)'s RADARSAT-2, spring data from European Space Agency (ESA)'s Envisat Advanced Synthetic Aperture Radar (ASAR), and fall data from the Japan Aerospace Exploration Agency (JAXA)'s Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR), complemented by patches of CSA's RADARSAT-1 data from fall 2000 and ESA's Earth Remote Sensing Satellites ERS-1 and -2 data from spring Each radar instrument contributes its unique coverage and performance level. The final mosaics assemble 900 satellite tracks and more than 3,000 orbits of radar data. Data acquisitions between 2006 and 2011 were coordinated through the IPY Space Task Group. The 450 m map contains some minor improvements compared with the 900 m product, such as slightly better coverage in West Antarctica due to the inclusion of a few additional tracks and a tide correction for Ross and Ronne ice shelves (RADARSAT-2, 2009 tracks only). The Theory of Measurements section of the MEaSUREs InSAR-Based Ice Velocity Maps of Central Antarctica: 1997 and 2009 documentation contains additional details about this correction. Table 5 describes the data sources used in this data set. Table 5. Temporal and spatial coverage of source satellite data Platform Look Dir. Mode Repeat Cycle (day) Incidence Angle Resolution Swath (km) Frequency (GHz) # of Proc. Tracks Raw Data Volume Rg x Az (m) Year ERS-1 & 2 Right N/A x RADARSAT-1 Left S2-S x5-17x Right various x5-12x ENVISAT Right IS x /130/210 1/1/2 2007/2008/2009 RADARSAT-2 Left S5/EH /57 12x /14 4/1 2009/2011 ALOS PALSAR Right FBS x /204/296 2/6/9 2006/2007/2008 Rignot, E., S. Jacobs, J. Mouginot, and B. Scheuchl Ice Shelf Melting Around Antarctica. Science, 341(6143): doi: /science Rignot, E., J. Mouginot, and B. Scheuchl Ice Flow of the Antarctic Ice Sheet. Science, 333(6048): doi: /science Rignot, E., J. Mouginot, and B. Scheuchl Antarctic grounding line mapping from differential satellite radar interferometry. Geophys. Res. Lett., 38, L10504, doi: /2011gl Rignot, E., J. L. Bamber, M. R. Van Den Broeke, C. Davis, Y. H. Li, W. J. Van De Berg, & E. Van Meijgaard Recent Antarctic ice mass loss from radar interferometry and regional climate modelling. Nature Geoscience, 1(2), doi: /ngeo102 Michel, R., and E. Rignot Flow of Glacier Moreno, Argentina, from Repeat-Pass Shuttle Imaging Radar Images: Comparison of the Phase Correlation Method with Radar Interferometry. J. Glaciol. 45, The following related documents are available Table 6. Related Documents Document URL NASA MEaSUREs Data at NSIDC NASA MEaSUREs NSIDC MEaSUREs Data Web site NASA MEaSUREs Projects Web site The following acronyms are used in this document. Table 7. Acronyms Acronym ALOS Advanced Land Observing System ASAR Advanced Synthetic Aperture Radar CSA Canadian Space Agency 5 von :14

6 ERS Earth Remote Sensing Satellite ESA European Space Agency FTP File Transfer Protocol IPY International Polar Year JAXA Japan Aerospace Exploration Agency NASA National Aeronautics and Space Administration NSIDC National Snow and Ice Data Center PALSAR Phased Array Type L-band Synthetic Aperture Radar RADARSAT Radar Satellite SAR Synthetic Aperture Radar URL Uniform Resource Locator October 2011 September 2013 Search NSIDC Data Arctic Sea Ice News and Analysis Icelights: Answers to Your Questions Knowledge Base Reverb (NASA) IceBridge Portal Data Pool (Direct FTP for select data) Data Collections List Sea Ice Index (Passive microwave satellite data) MASIE (Daily sea ice extent, multi-source) Greenland Today Press Room Cryosphere Quick Facts All About Glaciers All About Snow All About Sea Ice Arctic Climatology - A Primer Ask Us Use & Copyright Web Policy Jobs Home Contact Us 2013, National Snow and Ice Data Center :: Advancing knowledge of Earth's frozen regions ASK US 6 von :14