Data Set ID: 
NSIDC-0664

SUMER Antarctic Ice-shelf Buttressing, Version 1

This data set, part of the French National Research Agency’s project on Survey and Modelling of East Antarctica (SUMER), consists of high-resolution information about ice-shelf buttressing for the whole of Antarctica. Buttressing is inferred from known ice geometry and ice motion with the Elmer/Ice ice flow model. Input sources are Bedmap2, MEaSUREs surface ice velocities, and the MEaSUREs grounding-line positions.

This is the most recent version of these data.

Version Summary: 

initial release

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Data: Data integrity and usability verified

Documentation: Key metadata and user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools

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Parameter(s):
  • SNOW/ICE > ICE VELOCITY
Data Format(s):
  • NetCDF
Spatial Coverage:
N: -60, 
S: -90, 
E: 180, 
W: -180
Platform(s):ALOS, ENVISAT, ERS-1, ERS-2, RADARSAT-1, RADARSAT-2
Spatial Resolution:
  • 1 km x 1 km
Sensor(s):ASAR, PALSAR, SAR
Temporal Coverage:
  • 1 September 1996 to 1 September 2009
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Gaël Durand, Fabien Gillet-Chaulet, Olivier Gagliardini

Geographic Coverage

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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.

Durand, G., F. Gillet-Chaulet, O. Gagliardini, and J. J. Fürst. 2016. SUMER Antarctic Ice-shelf Buttressing, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/FWHORAYVZCE7. [Date Accessed].

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Detailed Data Description

This data set, part of the French National Research Agency’s project on Survey and Modelling of East Antarctica (SUMER), consists of high-resolution data about ice-shelf buttressing for the whole of Antarctica. Buttressing is inferred from known ice geometry and ice motion with the Elmer/Ice ice flow model. Input sources are Bedmap2, MEaSUREs surface ice velocities, and the MEaSUREs grounding-line positions. The data set consists of eight files, which comprise eight two-dimensional fields for the floating ice shelves of Antarctica. 

Format

Data are in binary NetCDF (.nc) format.

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File and Directory Structure

Data are available via FTP and HTTPS sites. Each file contains four variables, x, y, grid-mapping, and one variable specific to the file. The x, y, grid-mapping variables define the polar stereographic projection of the data, which is true scale at 71° S. Table 1 provides the file names, the file-specific variable, and descriptions. For all files, -9999 signifies no data. For more information on buttressing, refer to the Parameter Description section below.

Table 1. File Names and Descriptions
File Name Variable Description
bmax_nsidc_sumer_buttressing_v1.0.nc bmax Maximum buttressing as derived by data assimilation with the Elmer/Ice ice flow model. The maximum is attained in the second principal stress direction, i.e., the direction of maximal extensive stress. [No units] 
bmin_nsidc_sumer_buttressing_v1.0.nc bmin Minimum buttressing as derived from data assimilation with the Elmer/Ice ice flow model. The minimum is attained in the first principal stress direction, i.e., the direction of minimal extensive stress. [No units]
bflow_nsidc_sumer_buttressing_v1.0.nc bflow Buttressing calculated in flow direction on the basis of data assimilation with the Elmer/Ice ice flow model. [No units]
ev21_nsidc_sumer_buttressing_v1.0.nc ev21 X-component of the normalised second principal stress vector. The stress tensor was inferred from data assimilation with the Elmer/Ice ice flow model. [No units]
ev22_nsidc_sumer_buttressing_v1.0.nc ev22 Y-component of the normalised second principal stress vector. The stress tensor was inferred from data assimilation with the Elmer/Ice ice flow model. [No units]
velx_nsidc_sumer_buttressing_v1.0.nc velx X-component of the ice velocities inferred from data assimilation with the Elmer/Ice ice flow model. The model was run in shallow-shelf approximation mode, a vertically integrated form of the force balance equations. [m/a]
vely_nsidc_sumer_buttressing_v1.0.nc vely Y-component of the ice velocities inferred from data assimilation with the Elmer/Ice ice flow model. The model was run in shallow-shelf approximation mode, a vertically integrated form of the force balance equations. [m/a]
visc_nsidc_sumer_buttressing_v1.0.nc visc Ice viscosity parameter B as inferred from the assimilation of velocity and ice thickness observations. The underlying constitutive equation is non-linear with an exponent of n=3. The viscosity parameter is related to the rate factor or fluidity parameter A via A=1/(Bn). [106 Pa a(1/3)]

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    File Size

    The .nc files are 231 MB each.

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    Volume

    The volume of the data set is 1.8 GB.

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    Spatial Coverage

    Southernmost Latitude: 90°S
    Northernmost Latitude: 60°S
    Westernmost Longitude: 180°W
    Easternmost Longitude: 180°E

    Spatial Resolution

    Spatial resolution is 1 km.

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    Temporal Coverage

    Temporal coverage for this data set is 1 September 1996 to 1 September 2009.

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    Parameter or Variable

    The parameters for this data set include ice velocity and buttressing.

    Parameter Description

    Buttressing - In glaciology, buttressing is a normal force exerted by the ice shelf on the upstream grounded ice in a certain horizontal direction (Schoof, 2006; Gudmundsson et al., 2012; Gudmundsson, 2013). The normal force is inferred from the stress tensor choosing a certain horizontal direction n.  This force is compared to the vertically integrated hydrostatic pressure, a normal force, that the ocean water would exert if the ice shelf was removed up to this position. The ratio of these two forces determines the buttressing potential of the ice shelf. 

    Sample Data Record

    Figure 1. Sample Plot of X-Component of Normalised 2nd Principal Stress Vector
    Figure 2. Sample Plot of Y-Component of Normalised 2nd Principal Stress Vector

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    Software and Tools

    Software and Tools

    See NetCDF Software Tools for a list of resources for accessing NetCDF files.

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    Data Acquisition and Processing

    Data Sources

    Input data sources are Bedmap2, the MEaSUREs surface velocities and the MEaSUREs grounding-line positions. The ice geometry is exclusively informed from the Bedmap2 product: Bedmap2 - Ice thickness and subglacial topographic model of Antarctica. The MEaSUREs grounding-line positions were used to locate additional pinning-points which provide basal resistance. See MEaSUREs InSAR-Based Antarctica Ice Velocity Map  and MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry.

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    Processing Steps

    DATA PROCESSING STEPS
    The quantification of ice-shelf buttressing relies on the stress regime within the ice body (Gudmundsson, 2013). As the stress tensor is not an observed quantity on large scales, the Elmer/Ice ice flow model provided data assimilation.

    Data assimilation
    The stress tensor is inferred from assimilating geometry and velocity observations for the whole of Antarctica with the Elmer/Ice ice flow model (Fürst et al., 2015). Primary input to the assimilation is the Bedmap2 surface and bottom elevations (Fretwell et al., 2013) and MEaSUREs surface velocities from satellite interferometry (Rignot et al., 2011). The assimilation relies on standard inverse methods (Morlighem et al., 2010; Gillet-Chaulet et al., 2012; Arthern et al., 2015) and simultaneously infers a viscosity parameter B and a basal friction parameter b2. For details on the method and on the performance of the inversion on continental scales, please see Fürst et al., 2016 and Fürst et al., 2015.

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    References and Related Publications

    Contacts and Acknowledgments

    Gaël Durand
    Laboratoire de Glaciologie et Geophysique de l'Environnement
    gael.durand@lgge.obs.ujf-grenoble.fr

    Fabien Gillet-Chaulet
    Laboratoire de Glaciologie et Geophysique de l'Environnement
    fabien.gillet-chaulet@lgge.obs.ujf-grenoble.fr

    Olivier Gagliardini
    Laboratoire de Glaciologie et Geophysique de l'Environnement
    olivier.gagliardini@ujf-grenoble.fr

    Johannes Fürst
    University of Erlangen-Nürnberg
    Institute of Geography
    Erlangen Germany
    johannes.fuerst@fau.de

    Document Information

    DOCUMENT CREATION DATE

    August 2016

    No technical references available for this data set.

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