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Data Set ID:
IDBMG4

IceBridge BedMachine Greenland, Version 3

This data set contains a bed topography/bathymetric map of Greenland based on mass conservation, multi-beam data, and other techniques. The data set also includes surface elevation, ice thickness and an ice/ocean/land mask.

Version Summary:

Version 3 includes ocean bathymetry all around Greenland based on data from NASA’s Ocean Melting Greenland (OMG) and other campaigns of bathymetry measurements. The subglacial bed topography has also been updated by including more ice thickness data and constraining the ice thickness at the ice/ocean interface based on bathymetry data when available.

Geographic Coverage

Parameter(s):
  • Bathymetry/Seafloor Topography > Bathymetry
  • TOPOGRAPHY > TERRAIN ELEVATION > BED ELEVATION > Bed Elevation
  • Snow/Ice > Ice Depth/Thickness > Ice Thickness
  • Glaciers/Ice Sheets > Glacier Elevation/Ice Sheet Elevation > Surface Elevation
Spatial Coverage:
  • N: 90, S: 60, E: 10, W: -80

Spatial Resolution:
  • 150 x 150
Temporal Coverage:
  • 1 January 1993 to 31 December 2016
Temporal Resolution: Not specified
Data Format(s):
  • NetCDF
Platform(s) DC-8, P-3B
Sensor(s): MCoRDS
Version: V3
Data Contributor(s): Mathieu Morlighem
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Morlighem, M. et al. 2017. IceBridge BedMachine Greenland, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/2CIX82HUV88Y. [Date Accessed].

Literature Citation

As a condition of using these data, we request that you acknowledge the author(s) of this data set by referencing the following peer-reviewed publication.

  • Morlighem, M., C. Williams, E. Rignot, L. An, J. E. Arndt, J. Bamber, G. Catania, N. Chauché, J. A. Dowdeswell, B. Dorschel, I. Fenty, K. Hogan, I. Howat, A. Hubbard, M. Jakobsson, T. M. Jordan, K. K. Kjeldsen, R. Millan, L. Mayer, J. Mouginot, B. Noël, C. O'Cofaigh, S. J. Palmer, S. Rysgaard, H. Seroussi, M. J. Siegert, P. Slabon, F. Straneo, M. R. van den Broeke, W. Weinrebe, M. Wood, and K. Zinglersen. 2017. BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation, Geophysical Research Letters. 44. . http://dx.doi.org/10.1002/2017GL074954

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Detailed Data Description

Format

The data are in NetCDF 1.6 file format.

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File and Directory Structure

Data NetCDF file, BedMachineGreenland-2017-09-20.nc, is on the HTTPS site, https://daacdata.apps.nsidc.org/DATASETS/IDBMG4_BedMachineGr/.

In the file name, "nc" indicates NetCDF file format, and 2017-09-20 indicates date of data file creation.

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File Size

The data file is approximately 2.1 GB

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Spatial Coverage

Spatial coverage for the data set currently includes Greenland and the Arctic.

Greenland / Arctic:
Southernmost Latitude: 60° N
Northernmost Latitude: 90° N
Westernmost Longitude: 80° W
Easternmost Longitude: 10° E

Spatial Resolution

The output product is generated at 150 m resolution. The true resolution varies between 150 m and 5 km.

Projection and Grid Description

Polar Stereographic North (70° N, 45° W), corresponding to EPSG 3413.

Heights are with respect to mean sea level (i.e. not the WGS84 ellipsoid).

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Temporal Coverage

Ice thickness data were collected between 1993 and 2016. The nominal date of this data set is 2007.

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Parameter or Variable

Parameter Description

The BedMachine data file contains parameters as described in Table 1.

Table 1. File Parameters and Units
Parameter Name Description Units
bed Bed elevation (bed topography) Meters
errbed Bed topography/ice thickness error Meters
geoid Geoid height above WGS84 Ellipsoid Meters
mask mask (0 = ocean, 1 = ice-free land, 2 = grounded ice, 3 = floating ice, 4 = non-Greenland land) Flag values (0 - 4)
source data source, Mass Conservation/kriging/bathymetry: (0 = none, 1 = gimpdem, 2 = Mass conservation, 3 = synthetic, 4 = interpolation, 5 = hydrostatic equilibrium, 6 = kriging, 7 = RTOPO-2, 8 = gravity inversion, 10+ = bathymetry data) Flag values (0 - 40)
surface Ice surface elevation Meters
thickness Ice thickness Meters
x projection y coordinate Meters
y projection y coordinate Meters

Sample Data Record

Figure 1 illustrates Greenland bedrock altitude and ice thickness.

Figure 1. Greenland Bedrock Altitude and Ice Thickness

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Software and Tools

Software and Tools

See the NetCDF Resources at NSIDC page for tools to work with netCDF files.

The netCDF data file is compatible with HDF5 libraries, and can be read by HDF readers such as HDFView. If the netCDF file reader you are using does not read the data, see http://www.unidata.ucar.edu/software/netcdf/ and http://nsidc.org/data/netcdf/tools.html for information on updating the reader.

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Quality Assessment

An error estimate of the bed elevation and ice thickness is provided in the data set, illustrated in Figure 2.

Figure 2. Error Estimate of Greenland Bed Elevation and Ice Thickness

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Data Acquisition and Processing

Data Acquisition Methods

Source data used in deriving this product include:

Ancillary products used include:

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Derivation Techniques and Algorithms

Sparse, airborne, radar sounding-derived ice thickness data are combined with comprehensive, high-resolution, ice motion derived from satellite interferometric synthetic-aperture radar to calculate ice thickness based on Mass Conservation (MC). The MC method solves the mass conservation equation to derive ice thickness, while at the same time minimizing departure from the original radar-derived ice thickness data. The algorithm conserves mass fluxes while minimizing the departure from the original radar-derived ice thickness data. Ice surface motion provides a physical basis for extrapolating sparse ice thickness data to larger areas with few or no data. The method works best in areas of fast flow, where errors in flow direction are small and the glaciers slide on the bed. In the interior regions, where errors in flow direction are larger, kriging is used to interpolate ice thickness (Morlighem, et al 2014).

Ocean bathymetry is mapped by combining sparse bathymetry measurements from single and multibeam measurements and casts and RTopo-2 (Schaffer et al. 2016).

The algorithm neglects ice motion by internal shear, which is an excellent approximation for fast-flowing glaciers (>100 m yr-1) (Morlighem, et al 2014).

The bed topography is derived by subtracting the ice thickness from the Greenland Mapping Project (GIMP) Digital Elevation Model (http://bpcrc.osu.edu/gdg/data/gimpdem).

Version History

On 19 May 2015, the IceBridge BedMachine Greenland data were replaced by Version 2. Version 2 includes improved processing of some basins and adds some Operation IceBridge 2014 data. Heights are now provided with respect to mean sea level, instead of the WGS84 ellipsoid. The geoid is included in an additional field in the data.

On 25 September 2017, the IceBridge BedMachine Greenland data were replaced by Version 3. Version 3 now includes ocean bathymetry all around Greenland based on data from NASA’s Ocean Melting Greenland (OMG) and other campaigns of bathymetry measurements. The subglacial bed topography has also been updated by including more ice thickness data and constraining the ice thickness at the ice/ocean interface based on bathymetry data when available.

Error Sources

Sources of error include error in ice velocity direction and magnitude, error in surface mass balance and ice thinning rates.

In a trial setting with unusually dense radar sounding coverage, we report errors in the MC-inferred thickness of 36 m, only slightly higher than that of the original data. In areas less well constrained by radar-derived thickness data, or constrained by only one track of data, for example, in south Greenland, errors may exceed 50 m (Morlighem, et al 2013).

No or very little data were available for some fjords, and uncertainty may be high (>500 m).

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Sensor or Instrument Description

CReSIS Radar

The Center for Remote Sensing of Ice Sheets (CReSIS) Multichannel Coherent Radar Depth Sounder (MCoRDS) operates over a 180 to 210 MHz frequency range with multiple receivers developed for airborne sounding and imaging of ice sheets. See IceBridge MCoRDS L2 Ice Thickness for further information on the MCoRDS radar and the Level-2 data.

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References and Related Publications

Contacts and Acknowledgments

Mathieu Morlighem
Department of Earth System Science
University of California, Irvine
Irvine CA, 92617, USA

Acknowledgments: 

This work was performed at the University of California Irvine under a contract with the National Aeronautics and Space Administration, Cryospheric Sciences Program (#NNX15AD55G), and the National Science Foundation’s ARCSS program (#1504230), and in cooperation with the University of Bristol as part of the Basal Properties of Greenland project (NERC grant NE/M000869/1).

We would like to thank GRISO RCN (Greenland Ice Sheet Ocean Research Coordination Network) for their help in finding available bathymetry data.

Document Information

DOCUMENT CREATION DATE

25 September 2017

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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