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IceBridge WISE L2 Geolocated Ice Thickness and Surface Elevation

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.

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

Citing These Data

Literature Citation

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.

We kindly request that you cite the use of this data set in a publication using the following citation example. For more information, see our Use and Copyright Web page.

Data Citation

Rignot, Eric, Jeremie Mouginot, Chris F. Larsen, Young Gim, Donald Kirchner. 2013. IceBridge WISE L2 Geolocated Ice Thickness and Surface Elevation, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://nsidc.org/data/irwis2.html.

Overview

Platform

DHC-3

Sensors

Warm Ice Sounding Explorer (WISE)

Spatial Coverage

Southeastern coastal Alaska
Southernmost Latitude: 58.7°
Northernmost Latitude: 61.7°
Westernmost Longitude: -148.6°
Easternmost Longitude: -137.1°

Spatial Resolution

Ranges from 20 m to 500 m dependent on along-track, cross-track, and aircraft height characteristics

Temporal Coverage

16 March 2012 to 25 March 2012

Temporal Resolution

Annual

Parameters

Ice Thickness Measurements

Data Format

Fixed-width, space-delimited ASCII text files

Metadata Access

View Metadata Record

Version

Version 1.0

Get Data

FTP

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Eric Rignot
Department of Earth System Science
University of California, Irvine
Irvine CA, 92617, USA

Jeremie Mouginot
Department of Earth System Science
University of California, Irvine
Irvine CA, 92617, USA

Young Gim
Jet Propulsion Laboratory
4800 Oak Grove Dr.
Pasadena, CA 91109

Donald Kirchner
Department of Physics and Astronomy
University of Iowa
Iowa City, Iowa, USA.

Technical Contact

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
e-mail: nsidc@nsidc.org

Acknowledgements

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.

2. Detailed Data Description

The data set includes measurements for Elevation, Surface, Bottom, and Thickness.

Format

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.

File and Directory Structure

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.

File Naming Convention

The CSV files are named according to the following convention. File name variables are described in Table 1:

IRWIS2_Data_20120316.csv

IRWIS2_Data_20120316.csv.xml

Where:

Table 1. File Naming Convention Description
Variable Description
IRWIS2 Short name for IceBridge Radar WISE L2 Ice Thickness
Data Data file
YYYY 4-digit year
MM 2-digit month
DD 2-digit date
.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.

File Size

CSV text files range from approximately 726 KB to 3.2 MB.

Volume

The entire data set is approximately 14 MB.

Spatial Coverage

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

Spatial Resolution varies by surface characteristics and aircraft flown, as shown in Table 2

Table 2. Spatial Resolution
Data Resolution
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.

Projection and Grid Description

These data are provided in WGS-84 geodetic coordinates and WGS-84 ellipsoid elevation reference.

Temporal Coverage

These data were collected as part of Operation IceBridge funded campaigns from 16 March 2012 to 25 March 2012.

Temporal Resolution

Annual

Parameter or Variable

The WISE L2 Ice Thickness data set contains measurements for Elevation, Surface, Bottom and Thickness.

Parameter Description

The CSV ASCII text files contain fields as described in Table 3.

Table 3. MATLAB File Parameter Description
Parameter Description Units
LAT Latitude Degrees North
LON Longitude Degrees East
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
NA
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*
NA

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).

Sample Data Record

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.

sample data record

3. Data Access and Tools

Get Data

Data are available via FTP.

Software and Tools

CSV files may be opened by any text viewing program.

4. Data Acquisition and Processing

Theory of Measurements

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.

Data Acquisition Methods

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.)

Derivation Techniques and Algorithms

Processing Steps

  1. The first stage of data processing is an incoherent averaging of radar echoes in the azimuth direction, followed by a range migration using an Omega-K algorithm.
  2. The resulting echo diagrams are semi-automatically digitized to record the position of the ice surface and of the glacier bed.
  3. The digitized bed is checked at crossing points with other tracks or other datasets for consistency to limit the possibility of false detection, for instance due to off-nadir radar reflections.

Error Sources

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).

Sensor or Instrument Description

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.

5. References and Related Publications

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.

Related Data Collections

Related Web Sites

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)

6. Document Information

Acronyms and Abbreviations

The acronyms used in this document are listed in Table 4.

Table 4. Acronyms and Abbreviations
Acronym Description
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
L2 Processing Level-2
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

Document Creation Date

25 November 2013

Document Revision Date

.....

Document URL

http://nsidc.org/data/docs/daac/icebridge/irwis2/index.html