This data set contains depth sounder measurements of elevation, surface, bottom, and thickness for Alaska taken from the Warm Ice Sounding Explorer (WISE). The data were collected as part of Operation IceBridge funded aircraft survey campaigns.
Operation IceBridge products may include test flight data that are not useful for research and scientific analysis. Test flights usually occur at the beginning of campaigns. Users should read flight reports for the flights that collected any of the data they intend to use. Check IceBridge campaign Flight Reports for dates and information about test flights.
Rignot, E., J. Mouginot, C. F. Larsen, Y. Gim, and D. Kirchner. 2013. Low-frequency Radar Sounding of Temperate Ice Masses in Southern Alaska, Geophysical Research Letters, 40. http://dx.doi.org/10.1002/2013GL057452.
We kindly request that you cite the use of this data set in a publication using the following citation. For more information, see our Use and Copyright Web page.
Rignot, Eric, Jeremie Mouginot, Chris F. Larsen, Young Gim, Donald Kirchner. 2013. IceBridge WISE L2 Ice Thickness and Surface Elevation, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://dx.doi.org/10.5067/0ZBRL3GY720R.
Warm Ice Sounding Explorer (WISE)
Southeastern coastal Alaska
Ranges from 20 m to 500 m dependent on along-track, cross-track, and aircraft height characteristics
16 March 2012 to 25 March 2012
Ice Thickness Measurements
Fixed-width, space-delimited ASCII text files
Department of Earth System Science
University of California, Irvine
Irvine CA, 92617, USA
Department of Earth System Science
University of California, Irvine
Irvine CA, 92617, USA
Jet Propulsion Laboratory
4800 Oak Grove Dr.
Pasadena, CA 91109
Department of Physics and Astronomy
University of Iowa
Iowa City, Iowa, USA.
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
The radar depth sounder data and data products from WISE have been collected since 2006 using grant funding from NASA and NSF. This project was funded by a grant from NASA's Cryosphere Science Program, WBS Number 509496.02.08.01.62 and 281945.02.53.02.27.
The data set includes measurements for Elevation, Surface, Bottom, and Thickness.
The WISE L2 files are in Comma-Separated Values (CSV) text files. The radar data are divided into segments for each day of operation. The segment ID is YYYYMMDD where YYYY is the four-digit year, MM is the two-digit month from 1 to 12, DD is the two-digit day of the month from 1 to 31.
The data are organized in directories by date. Each directory contains CSV files, one file per frame, with geocoded layer information for all valid radar data sets with and without a visible bottom return. The directory contains a file for each segment as a concatenation of all the frames in that segment.
The CSV files are named according to the following convention. File name variables are described in Table 1:
|IRWIS2||Short name for IceBridge Radar WISE L2 Ice Thickness|
|.csv||indicates comma separated value ASCII text file|
Each data file is paired with an XML file containing platform, instrument, campaign, location,date, time and other associated metadata.
CSV text files range from approximately 726 KB to 3.2 MB.
The entire data set is approximately 14 MB.
Spatial coverage for the IceBridge WISE campaign in Southeastern coastal Alaska.
Southernmost Latitude: 58.7° N
Northernmost Latitude: 61.7° N
Westernmost Longitude: 148.6° W
Easternmost Longitude: 137.1° W
Spatial Resolution varies by surface characteristics and aircraft flown, as shown in Table 2
|Along-track||The final product has an along-track resolution of about 100 m and a sample spacing of about 25 m|
|Depth||17 m resolution and precision of about 35 m. Actual target location is ambiguous for a rough surface since the off-nadir returns in the antenna footprint can hide the nadir return.|
These data are provided in WGS-84 geodetic coordinates and WGS-84 ellipsoid elevation reference.
These data were collected as part of Operation IceBridge funded campaigns from 16 March 2012 to 25 March 2012.
The WISE L2 Ice Thickness data set contains measurements for Elevation, Surface, Bottom and Thickness.
The CSV ASCII text files contain fields as described in Table 3.
|TIME||UTC||Seconds of day|
|THICK||Ice Thickness: Bottom minus Surface. Constant dielectric of 3.15 (no firn) is assumed for converting propagation delay into range. -9999 indicates no thickness available.||Meters|
|ELEVATION||Elevation referenced to WGS-84 Ellipsoid.||Meters|
|FRAME||Fixed length field. YYYY = year, MM = month, DD = day, HH = hour, MIN = minute, SS = second.||NA|
|SURFACE||Surface height referenced to WGS-84 Ellipsoid provided by an external dataset (see Dem_select below).||Meters|
|BOTTOM||Ice Bottom Elevation referenced to WGS-84 Ellipsoid. Constant dielectric of 3.15 (no firn) is assumed for converting propagation delay into range. -9999 indicates no thickness available.||Meters|
|QUALITY||1: High confidence pick
2: Medium confidence pick
3: Low confidence pick
|DATE||Day, Month, Year: DDMMYY||NA|
|DEM_SELECT||0: NASA IceBridge's University of Alaska, Fairbanks (UAF) LiDAR Scanner
1: National Elevation Model or Muskett et al. 2009*
Note (*): Where surface elevation is not recorded by the LiDAR (Dem_select=1), we employ a Digital Elevation Model (DEM) from the Shuttle Radar Mapping Mission and from Intermap Technologies, Inc. (ITI), both acquired in the year 2000 (Muskett et al. 2009), or the USGS National Elevation Model which we adjust vertically at both ends of the missing surface segments and linearly interpolate in between to best fit the UAF laser elevation data of March 2012 and account for ice elevation change between 2000 and 2012. This data filling occurs over less than 30 percent of the flight tracks (Muskett et al 2009).
The image below shows a selection of records from the IRMCR2_Data_20120320.csv data file. The fields in each record correspond to the parameters described in Table 3.
Data are available via FTP.
CSV files may be opened by any text viewing program.
Ice thickness is typically determined using data collected from waveforms with different pulse durations. Generally, all receive channels are used to produce the best result. The two reflections that are of most interest are the ice surface and ice bottom. The difference in the propagation time between the ice surface and ice bottom reflections is then converted into ice thickness using an estimated ice index of refraction of ice (square root of 3.15). The media is assumed to be uniform, that is, no firn correction is applied.
Data collection modes used for typical operation are described below in the Data Acquisition Methods section.
The radar is operated at a center frequency of 2.5 MHz, a 2 MHz bandwidth, with a sampling frequency of 20 MHz on 16 bits with a 50 μs data window, and a pulse repetition frequency of 1 kHz. The default operating power is 800 W peak power. In March 2012, WISE operated at 400 m above the surface on a DHC-3 Otter from Ultima Thule Lodge. For georeference of the data, a conventional GPS receiver is operated at 20 Hz along with the radar, with a precision of 10 m (Rignot et al 2013.)
The primary error sources for ice penetrating radar data are system electronic noise, multiple reflectors also known as multiples, and off-nadir reflections. Each of these error sources can create spurious reflections in the trace data leading to false echo layers in profile data. Multiple reflectors arise when the radar energy reflects off two surfaces more than once (or resonates) in the vertical dimension, and then returns to the receive antenna. Reflections occur in situations when two or more large reflectors are present with large electromagnetic constitutive property changes, such as the ice surface (air/ground), the bottom of the ice, and the aircraft body which is also a strong reflector. The radar receiver only records time since the radar pulse was emitted, so variation in the constant dielectric used to convert time into ice thickness may lead to errors of few percents (dielectric constant is assumed to be 3.15).
As described on the WISE Radar page, the Warm Ice Sounding Explorer (WISE) operates over a 1 to 5 MHz frequency range for airborne sounding of ice sheets and ice caps. The radar bandwidth is 2 MHz.
Muskett, R. R., C. S. Lingle, J. M. Sauber, A. S. Post, W. V. Tangborn, B. T. Rabus, and K. A. Echelmeyer. 2009. Airborne and Spaceborne DEM and Laser Altimetry-derived Surface elevation and Volume Changes of the Bering Glacier System, Alaska, USA, and Yukon, Canada, 1972–2006, Journal of Glaciology, 55(190):316–326.
Rignot, E., J. Mouginot, C. F. Larsen, Y. Gim, and D. Kirchner. 2013. Low-frequency Radar Sounding of Temperate Ice Masses in Southern Alaska, Geophysical Research Letters, 40, doi:10.1002/2013GL057452.
Warm Ice Sounder Explorer (WISE), Rignot Research Group, Department of Earth System Science, University of California Irvine (http://www.ess.uci.edu/group/erignot/projects/warm-ice-sounder-explorer-wise)
The acronyms used in this document are listed in Table 4.
|ASCII||American Standard Code for Information Interchange|
|CIRES||Cooperative Institute for Research in Environmental Science|
|CSV||Comma Separated Values ASCII file|
|DEM||Digital Elevation Model|
|FTP||File Transfer Protocol|
|GPS||Global Positioning System|
|NASA||National Aeronautics and Space Administration|
|NSF||National Science Foundation|
|NSIDC||National Snow and Ice Data Center|
|UAF||University of Alaska Fairbanks|
|URL||Uniform Resource Locator|
|UTC||Universal Time Code|
|WGS 84||World Geodetic System 1984|
|WISE||Warm Ice Sounding Explorer|
25 November 2013