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Data Set ID: 
NSIDC-0619

Synthesis of Thwaites Glacier Dynamics: Diagnostic and Prognostic Sensitivity Studies of a West Antarctic Outlet System, Version 1

This data set consists of experimental output from a higher-order finite-element model that was utilized in conjunction with existing data sets to isolate essential physical processes affecting Thwaites Glacier (TG) in the Amundsen Sea Embayment (ASE) of West Antarctica.

Geographic Coverage

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Mass Balance/Ice Sheet Mass Balance
  • Frozen Ground > Ground Ice
  • Snow/Ice > Ice Depth/Thickness
  • Sea Ice > Ice Extent
  • Snow/Ice > Ice Extent
  • Snow/Ice > Snow/Ice Temperature > Ice Temperature
  • Sea Ice > Ice Temperature
  • Snow/Ice > Ice Velocity
Spatial Coverage:
  • N: -74.05, S: -76.65, E: -105.28, W: -110.06

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 January 1973 to 31 December 2500
Temporal Resolution: Not specified
Data Format(s):
  • NetCDF
Platform(s) Not specified
Sensor(s): Not specified
Version: V1
Data Contributor(s): Byron Parizek, Donald Blankenship, Todd Dupont, John Holt
Please contact the data provider for the correct Data Citation for this data set.

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.

  • Parizek, B. R.. 2013. Dynamic (in)stability of Thwaites Glacier, West Antarctica, Journal of Geophysical Research-Earth Surface. 118. 638-655. https://doi.org/10.1002/jgrf.20044

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Detailed Data Description

A higher-order finite-element model is utilized to explore the effects of ice-ocean interactions, ice-shelf buttressing, basal properties (stress distribution, topography, sliding, rheology, and grounding-zone processes), surface mass balance, and inland dynamic perturbations on the present and future dynamics of Thwaites Glacier. This particular model is ideally suited for the broad nature of this investigation, as it incorporates efficient yet regionally reasonable simplifications of the stress field (higher-order), system geometry (2-d flowline), and mass-momentum-ocean coupling (mechanical ice and plume ocean). The model is constrained by data sets (including regional maps of ice thickness, surface elevation, basal topography, and ice surface velocity) and geophysical data analyses (including increasing the spatial resolution of surface and basal elevations and characterizing the sub-glacial interface of grounded ice as well as the grounding-zone transition between grounded and floating ice). Figure 1 shows the model domain for the different elements of the model.

The simulation for each process is described in Parizek et al. (2013).

Model Domain
Figure 1. Model Domain
Format

The data files are in Network Common Data Form (netCDF) format and are identified with the .nc file extension. 

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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0619_parizek/ directory. Within this directory, there is one folder, Thwaites_NSF, which contains 23 NetCDF (.nc) files.

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File Naming Convention

The netCDF files are named according to the the Sea-level Response to Ice Sheet Evolution (SeaRISE) naming conventions outlined at http://websrv.cs.umt.edu/isis/index.php/Output_Format.

This section explains the file naming convention used for this product with examples.

Example File Names:
BPA1_A_D2_C1_E0.nc
NNNn_X_Dd_Xx_Ee.nc

Refer to Table 1 for the valid values for the file name variables listed above.

Table 1. File Naming Convention Description
Variable Description
NNN three letter characters for name, either a group name like PSU for Penn State, or an individual name made up by the first character of the first name followed by the first two characters of the last name
n model number (n = 1 if you have only one model)
X experiment category, either A for Antarctica, or G for Greenland
D denotes model dimension
d model dimension identifier (1 for 1D, 2 for 2D, 3 for 3D)
X C denotes model climate treatment
S denotes model sliding treatment
M denotes model ocean treatment
x

c = model climate identifier (1 for constant climate, 2 for 4th Assessment future climate forcing (see below)
e assigned as 0=constant climate fixed at 2004 values; 1=1x, 2=1.5x, 3=2x the anomalies from ensemble mean of 18 AR4 models for the A1B emissions scenario)

s = model sliding identifier (1 for sliding forcing with experiment number (see below),
e assigned as 1=2x, 2=2.5xm abd 3=3x amplification factor on u(b))

m = model ocean forcing identifier (1 for ocean forcing with experiment number (see below),
e assigned as 1=2m/yr, 2=20m/yr, 3=200m/yr, 4=coupled ocean-ice subshelf melt rates)

E denotes experiment category
e experiment number (0 for no forcing, versus >0 for forcing experiments as detailed above)

Example File Names:
BPA1_A_D2_T3_E1.nc 
NNNn_X_Dd_Tt_Ee.nc

Refer to Table 2 for the valid values for the file name variables listed above.

Table 2. File Naming Convention Description
Variable Description
NNN three letter characters for name, either a group name like PSU for Penn State, or an individual name made up by the first character of the first name followed by the first two characters of the last name
n model number (n = 1 if you have only one model)
X experiment category, either A for Antarctica, or G for Greenland
D denotes model dimension
d model dimension identifier (1 for 1D, 2 for 2D, 3 for 3D)
T denotes combinations of climate, sliding, and/or ocean treatments
t multiple forcing identifier (1 for climate, sliding, and ocean, 2 for climate and sliding, and 3 for climate and ocean forcings with experiment number (see below),
e assigned with the following amplification factors if that particular forcing is included
1= 1x AR4, 2x u(b), 2m/yr subshelf melt rates
2= 1x AR4, 2x u(b), coupled ice-ocean melt rates
3_T1= 1x AR4, coupled ice-ocean melt rates, and higher resolution topography around the grounding zone
E denotes experiment category
e experiment number (0 for no forcing, versus >0 for forcing experiments as detailed above)

Example File Names:
BPA1_A_D2_T3_E4_GZ1.nc 
NNNn_X_Dd_Tt_Ee_GZx.nc

Refer to Table 3 for the valid values for the file name variables listed above.

Table 3. File Naming Convention Description
Variable Description
NNN three letter characters for name, either a group name like PSU for Penn State, or an individual name made up by the first character of the first name followed by the first two characters of the last name
n model number (n = 1 if you have only one model)
X experiment category, either A for Antarctica, or G for Greenland
D denotes model dimension
d model dimension identifier (1 for 1D, 2 for 2D, 3 for 3D)
T denotes combinations of climate, sliding, and/or ocean treatments
t multiple forcing identifier (1 for climate, sliding, and ocean, 2 for climate and sliding, and 3 for climate and ocean forcings with experiment number (see below),
e assigned with the following amplification factors if that particular forcing is included
4_GZ1 = 3_T1 with enhanced basal melting and reduced friction within a 5-km grounding zone
5_GZ2 = 3_T1 with enhanced basal melting and reduced friction within a 6-km grounding zone
6_GZ3 = 3_T1 with enhanced basal melting and reduced friction within a 7-km grounding zone
7_GZ4 = 3_T1 with enhanced basal melting and reduced friction within a 10-km grounding zone
8_GZ5 = 3_T1 with enhanced basal melting and reduced friction within a 6-km grounding zone and the lower-resolution SeaRise basal topography around the grounding zone
E denotes experiment category
e experiment number (0 for no forcing, versus >0 for forcing experiments as detailed above)

Example File Names:
BPA1_A_D2_T3_E10_GZ3p.nc 
NNNn_X_Dd_Tt_Ee_GZ3p.nc

Refer to Table 4 for the valid values for the file name variables listed above.

Table 4. File Naming Convention Description
Variable Description
NNN three letter characters for name, either a group name like PSU for Penn State, or an individual name made up by the first character of the first name followed by the first two characters of the last name
n model number (n = 1 if you have only one model)
X experiment category, either A for Antarctica, or G for Greenland
D denotes model dimension
d model dimension identifier (1 for 1D, 2 for 2D, 3 for 3D)
T denotes combinations of climate, sliding, and/or ocean treatments
t multiple forcing identifier (1 for climate, sliding, and ocean, 2 for climate and sliding, and 3 for climate and ocean forcings with experiment number (see below),
e assigned with the following amplification factors if that particular forcing is included
9_GZ3p = effectively plastic (m =8) substrate across entire domain following forcing of linear viscous (m = 1) 6_GZ3
10_GZ3p = 9_GZ3p with an ~11% reduction in upstream flux)
E denotes experiment category
e experiment number (0 for no forcing, versus >0 for forcing experiments as detailed above)

Refer to Table 5 for the names and descriptions of the files in the data set.

Table 5. Data Set File Description
File Name Approximate File Size Description
BPA1_A_D2_C1_E0.nc 2.7 MB Constant-climate control run; fixed at 2004 values
BPA1_A_D2_C2_E1.nc 2.7 MB Climate forcing of 1x the anomalies from ensemble mean of 18 AR4 climate models for the A1B emissions scenario
BPA1_A_D2_C2_E2.nc 2.7 MB Climate forcing of 1.5x the anomalies from ensemble mean of 18 AR4 climate models for the A1B emissions scenario
BPA1_A_D2_C2_E3.nc 2.7 MB Climate forcing of 2x the anomalies from ensemble mean of 18 AR4 climate models for the A1B emissions scenario
BPA1_A_D2_S1_E1.nc 2.7 MB Sliding forcing with 2x amplification factor on u(b)
BPA1_A_D2_S1_E2.nc 2.7 MB Sliding forcing with 2.5x amplification factor on u(b)
BPA1_A_D2_S1_E3.nc 2.7 MB Sliding forcing with 3x amplification factor on u(b)
BPA1_A_D2_M1_E1.nc 2.7 MB Ocean forcing with subshelf melt rates of 2 m/yr
BPA1_A_D2_M1_E2.nc 2.7 MB Ocean forcing with subshelf melt rates of 20 m/yr
BPA1_A_D2_M1_E3.nc 2.7 MB Ocean forcing with subshelf melt rates of 200 m/yr
BPA1_A_D2_M1_E4.nc 2.7 MB Ocean forcing with subshelf melt rates from coupled ocean-ice models
BPA1_A_D2_T1_E2.nc 2.7 MB C1S1M4 combination forcings. See above for the surface, bed, and ocean components included here.
BPA1_A_D2_T2_E1.nc 2.7 MB C1S1 combination forcings. See above for the surface, bed, and ocean components included here.
BPA1_A_D2_T3_E1.nc 2.7 MB C1M1 combination forcings. See above for the surface, bed, and ocean components included here.
BPA1_A_D2_T3_E2.nc 2.7 MB C1M4 combination forcings. See above for the surface, bed, and ocean components included here.
BPA1_A_D2_T3_E3_T1.nc 2.7 MB T1=C1M4 above with higher resolution topographic data around the grounding zone and activation of ocean coupling for entire simulation
BPA1_A_D2_T3_E4_GZ1.nc 2.7 MB T1 with enhanced basal melting and reduced friction within a 5 km grounding zone.
BPA1_A_D2_T3_E5_GZ2.nc 2.7 MB T1 with enhanced basal melting and reduced friction within a 6 km grounding zone.
BPA1_A_D2_T3_E6_GZ3.nc 2.7 MB T1 with enhanced basal melting and reduced friction within a 7 km grounding zone.
BPA1_A_D2_T3_E7_GZ4.nc 2.7 MB T1 with enhanced basal melting and reduced friction within a 10 km grounding zone.
BPA1_A_D2_T3_E8_GZ5.nc 2.7 MB T1 with enhanced basal melting and reduced friction within a 6 km grounding zone and the lower resolution SeaRISE basal topography.
BPA1_A_D2_T3_E9_GZ3p.nc 2.7 MB Effectively plastic (m = 8) substrate across entire domain following forcing of linear viscous (m = 1) GZ3 run
BPA1_A_D2_T3_E10_GZ3p.nc 2.7 MB GZ3p with an ~11% reduction in upstream flux
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File Size

The NetCDF files are approximately 2.7 MB each.

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Volume

The entire data set is approximately 62 MB.

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Spatial Coverage

Spatial coverage is:

Southernmost Latitude: 76.65° S
Northernmost Latitude: 74.05° S
Easternmost Longitude: 105.28° W
Westernmost Longitude: 110.06° W

Spatial Resolution

Spatial resolution varies between 0.1 km to 1 km.

Projection and Grid Description

Refer to Table 6 for the description of the projection and grid structure

Table 6. Projection and Grid Description
Projection and Grid Variables Value
grid_mapping_name polar_stereographic
false_easting 0
false_northing 0
straight_vertical_longitude_from_pole 0
latitude_of_projection_origin -90
standard_parallel 71
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Temporal Coverage

This modeling data set covers from 1973 to 2500.

Temporal Resolution

Temporal resolution is either weekly (arrays with a dimension = 27405) or decadal (arrays with a dimension = 54)

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Parameter or Variable

Ground Ice
Ice Depth/Thickness
Ice Extent
Ice Temperature
Ice Velocity
Ice Temperature
Glacier Mass Balance

Variable Description

Refer to Table 7 for the output variables descriptions.

Table 7. Output Variables Description
Variable Name Units Description
time yrs reported years (at constant decadal intervals) relative to 2004-1-1 0:0:0 (1973-2500)
tseries yrs reported years (at constant weekly intervals) relative to 2004-1-1 0:0:0 (1973-2500)
x m projection_x_coordinate (2D horizontal variables are 1D (with an associated flowband width); (x,y) coordinates for 1D nodes spaced at 5 km are recorded in the x and y variables)
y m projection_y_coordinate (2D horizontal variables are 1D (with an associated flowband width); (x,y) coordinates for 1D nodes spaced at 5 km are recorded in the x and y variables)
lat ° latitude
lon ° longitude
x_flowline m distance along flowline with 1-km resolution
ivol m3 ice volume (ice equiv.)
totig m3 grounded ice volume (ice equiv.)
totif m3 floating ice volume (ice equiv.)
iarea m2 area covered by ice
iareag m2 area covered by grounded ice
iareaf m2 area covered by floating ice
flowbandwidth m flowband width along the flowline (at x_flowline)
usruf m surface topography or elevation
topg m bedrock topography or elevation (Note: elevation of ice bottom = usurf - thk = topg for grounded ice)
thk m ice thickness
acab m/yr upper surface mass balance (ice equiv.)
bmelt m/yr lower surface mass balance (ice equiv.)
dHdt m/yr tendency of ice thickness (ice equiv.)
mask NA Integer mask: flag_values = 1 ice-free ocean, 2 ice-free land, 3 grounded ice, 4 floating ice
gline_flux m2/yr grounding line flux (ice equiv.)
uvelsurf m/yr flowline ice velocity at the surface
uvelbase m/yr flowline ice velocity at the base
tempsurf K ice temperature at the surface
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Software and Tools

In order to view the data, download the free software Panoply netCDF, HDF and GRIB Data Viewer from NASA.

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Data Acquisition and Processing

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References and Related Publications

Contacts and Acknowledgments

Byron R. Parizek
Penn State DuBois
Mathematics and Geosciences
181 Smeal Building
College Place
DuBois, PA 15801
USA

Don Blankenship
Institute for Geophysics
J.J. Pickle Research Campus
Bldg. 196 10100 Burnet Rd.
Austin, TX 78758
USA

Todd K. Dupont
University of California
Department of Earth System Science
3218 Croul Hall
Mail Code 3100
Irvine, CA 92697
USA

John W. Holt
Institute for Geophysics
University of Texas at Austin
4412 Spicewood Springs Rd. #600
Austin, TX 78759-8500
USA

Acknowledgments: 

This research was supported by NSF OPP grant numbers 0531211, 0632198, 0732844, 0758274, 0909335. Other grants supporting the research were the Center for Remote Sensing of Ice Sheets (CReSIS) grant number 0424589, NASA grant numbers NRA-04-OES-02, NNX-09-AV94G, NNX-10-AI04G, 10-CRYO10-0025, and the NASA Cryospheric Science program grant number 281945.02.53.02.19.

Document Information

Document Creation Date

October 2014

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