This data set consists of outputs of several numerical models simulating ice stream flow over undulated bed, interaction of ice stream flow, and subglacial and supraglacial hydraulic systems. All simulations are performed for idealized geometries using finite-element models.
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Interaction of Ice Stream Flow with Heterogeneous Beds, Version 1
Geographic Coverage
Spatial Coverage: |
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Spatial Resolution: | Not Specified |
Temporal Coverage: |
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Temporal Resolution: | Not specified |
Parameter(s): |
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Platform(s) | Not specified |
Sensor(s): | Not specified |
Data Format(s): |
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Version: | V1 |
Data Contributor(s): | Olga Sergienko |
Metadata XML: | View Metadata Record |
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.
Sergienko, O. 2014. Interaction of Ice Stream Flow with Heterogeneous Beds, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N53R0QS6. [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.
Sergienko, O.. 2012. The Effects of Transverse Bed Topography Variations in Ice-flow Models, J. Geophys. Res. 117. F0311. http://dx.doi.org/10.1029/2011JF002203
Sergienko, O.. 2013. Glaciological Twins: Basally Controlled Subglacial and Supraglacial Lakes, International Glaciological Society. 59. 3-8(6). http://dx.doi.org/10.3189/2013JoG12J040
Detailed Data Description
This data set consists of outputs of several numerical models simulating ice stream flow over undulated bed, interaction of ice stream flow, and subglacial and supraglacial hydraulic systems. The detailed descriptions of the models and numerical experiments are provided in (Sergienko 2012). and (Sergienko 2013). All simulations are performed for idealized geometries using finite-element models. The data are provided on a rectangular grid in a native MATLAB (.mat) format and in netCDF (.nc) format.
Subglacial lakes beneath ice streams of Antarctica and supraglacial lakes observed on the flanks of the Greenland ice sheet may seem to be unrelated. The former derive their water from energy dissipation associated with basal friction, the latter from atmospherically driven surface melting. However, using numerical models of ice and water flow, it is shown that they share a common relationship to basal conditions that implies that surface lakes (or depressions that could host lakes under warmer atmospheric conditions) and basal lakes might exist in tandem (Sergienko 2013).
The main goal of this study is to widen our understanding of the applicability limits of the classical and much used flowband model in simulations of ice-flow response to basal topography. To achieve this goal, the performance of a 2-dimensional flowline model for isothermal ice flow over an idealized undulating bed is compared with both analytic treatments under linear rheology and a numerical 3-dimensional full Stokes model with non-linear rheology. The analytic treatment for the linear rheology is done by means of transfer functions (Jóhannesson 1992 and Gudmundsson 2003). These functions describe how basal conditions (variable topography and slipperiness) affect ice flow and are transmitted to the surface. They are derived from a solution of first-order perturbation of Stokes equations with corresponding boundary conditions. An advantage of transfer functions is that they are analytical. However, their applicability is limited to linear rheology and small perturbations in basal topography and slipperiness. A more general case, in which the bedrock undulations have arbitrary amplitudes and ice rheology obeys Glen's flow law is treated by numerical methods (Sergienko 2012).
In all experiments, the results of the three-dimensional calculations are compared to the results of the two-dimensional calculations in the flowband setting. In addition to a geometry suitable to the transfer functions application, a more complicated geometry, resembling an outlet glacier is considered for numerical simulations. This geometry is also used to assess effects of the lateral boundaries (Sergienko 2012).
MATrix LABoratory (MATLAB) (.mat) and Network Common Data Form (netCDF) (.nc)
Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0583_sergienko/
directory. Within this directory, there are two folders, bumps
and lakes
. The files inside these folders contain model outputs in MATLAB (.mat) and netCDF (.nc) formats simulating the effects of an isolated bump on ice flow. The model geometry, setup, and boundary conditions are described in Sergienko (2012). See Tables 1 and 2 for a description of each file.
Where:
Variable
|
Description
|
||||||
---|---|---|---|---|---|---|---|
*
|
Denotes that there are two file format extensions for each of these files:
|
File Name
|
Description
|
---|---|
IS_2D_no_sliding.* | 2D (x-z along the flow cross-section) simulations of ice flow with ice frozen to its bed |
IS_2D_sliding.* | 2D (x-z along the flow cross-section) simulations of ice flow with sliding at ice bed |
IS_no_sliding.* | 3D simulations of ice flow with ice frozen to its bed and periodic conditions at the lateral boundaries. |
IS_sliding.* | 3D simulations of ice flow with sliding at ice bed and periodic conditions at the lateral boundaries. |
OG_width20km_no_sliding.* | 3D simulations of ice flow in parabolic shape geometry with width 20 km and ice frozen to its bed and lateral boundaries. |
OG_width20km_sliding.* | 3D simulations of ice flow in parabolic shape geometry with width 20 km and sliding at the ice bed and lateral boundaries. |
OG_width3km_no_sliding.* | 3D simulations of ice flow in parabolic shape geometry with width 3 km and ice frozen to its bed and lateral boundaries. |
OG_width3km_sliding.* | 3D simulations of ice flow in parabolic shape geometry with width 3 km and sliding at the ice bed and lateral boundaries. |
File Name
|
Description
|
---|---|
lakes_bump.* | Simulations of ice stream flow over a Gaussian bump and consequent formation of subglacial and supraglacial lakes. |
lakes_sticky_spot.* | Simulations of ice stream flow over a sticky spot - a circular patch with enhanced basal resistance - and consequent formation of subglacial and supraglacial lakes. |
This section explains the file naming convention used for this data set.
Variable
|
Description
|
---|---|
IS | Ice stream geometry model |
OG | Outlet glacier geometry model |
lakes | Lakes geometry model |
no_sliding | Basal condition |
sliding | Basal condition |
sticky_spot | Basal condition |
bump | Geometry |
2D | Model type |
width20km | Model type |
width3km | Model type |
Data are in rectangular arrays. Table 4 describes the arrays. Note that not all files contain all arrays.
Variable
|
Description
|
---|---|
X
|
along the flow coordinate (km) |
Y
|
across the flow coordinate (km) |
Z
|
vertical coordinate (m) |
B
|
bed elevation (m) |
H
|
ice thickness (m) |
u
|
ice velocity, x-component (m/yr) |
v
|
ice velocity, y-component (m/yr) |
w
|
ice velocity, z-component (m/yr) |
u_cs
|
ice velocity of a longitudinal cross-section x-component (m/yr) |
w_cs
|
ice velocity of a longitudinal cross-section z-component (m/yr) |
Taux
|
basal shear stress, x-component (kPa) |
Tauy
|
basal shear stress, y-component (kPa) |
Sxx
|
deviatoric stress, xx-component (kPa) |
Syy
|
deviatoric stress, yy-component (kPa) |
Sxy
|
deviatoric stress, xy-component (kPa) |
Sxz
|
deviatoric stress, xz-component (kPa) |
Sxx_cs
|
deviatoric stress of a longitudinal cross-section, xx-component (kPa) |
Sxz_cs
|
deviatoric stress of a longitudinal cross-section, xz-component (kPa) |
Wb
|
subglacial water thickness (m) |
Ws
|
supraglacial water thickness (m) |
110 MB
North Lat: 78° S
South Lat: 78° S
Spatial Resolution
Variable
Data were collected from 01 June 2009 to 31 July 2013
Ice Thickness
Ice Velocity
Bed and Surface Elevation Dviatoric Stresses
Subglacial and Supraglacial Water Depth
Software and Tools
In order to view the netCDF files, you can download a free tool from NASA:
Panoply netCDF, HDF, and GRIB Data Viewer.
In order to use the MATLAB files, you need to acquire this software.
Data Acquisition and Processing
References and Related Publications
Contacts and Acknowledgments
Olga Sergienko
Princeton University
Atmospheric and Oceanic Sciences Program, GFDL
201 Forrestal Rd, Office 347
Princeton, NJ 08544
This research was supported by NSF OPP Grant Number 0838811.
Document Information
Document Creation Date
April 2014.
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