Get Data

DOWNLOADING DATA VIA FTP

Data can be downloaded through a Web browser or command line via FTP. When using a Web browser, the FTP link first directs you to an Optional Registration Form that if filled out, will allow you to receive notifications about updates or processing changes related to that specific data set. After completing the Optional Registration Form, the FTP directory becomes available. For additional help downloading data through an FTP client, go to the How to access data using an FTP client support page.

FTP

Data Set ID:
NSIDC-0583

Interaction of Ice Stream Flow with Heterogeneous Beds, Version 1

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.

Geographic Coverage

Spatial Coverage:
  • N: -78, S: -78, E: 0, W: 0

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 June 2009 to 31 July 2013
Temporal Resolution: Not specified
Parameter(s):
  • Snow/Ice > Ice Depth/Thickness > Ice Thickness
  • Snow/Ice > Ice Velocity
  • Topography > Terrain Elevation > Surface Elevation
Platform(s) Not specified
Sensor(s): Not specified
Data Format(s):
  • NetCDF
  • MATLAB
Version: V1
Data Contributor(s): Olga Sergienko

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.

Back to Top

Collapse All / Open All

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).

Format

MATrix LABoratory (MATLAB) (.mat) and Network Common Data Form (netCDF) (.nc)

Background color on
File and Directory Structure

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 Extension
Description
.mat MATLAB files.
.nc netCDF files.
Table 1. Files Contained in the Bumps Folder
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.
Table 2. Files Contained in the Lakes Folder
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.
Background color on
File Naming Convention

This section explains the file naming convention used for this data set.

Table 3. File Naming Conventions
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.

Table 4. Rectangular Array Descriptions
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)
Background color on
Volume

110 MB

Background color on
Spatial Coverage

North Lat: 78° S
South Lat: 78° S

Spatial Resolution

Variable

Background color on
Temporal Coverage

Data were collected from 01 June 2009 to 31 July 2013

Background color on
Parameter or Variable

Ice Thickness
Ice Velocity
Bed and Surface Elevation Dviatoric Stresses
Subglacial and Supraglacial Water Depth

Background color on

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.

Background color on

Data Acquisition and Processing

Background color on

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

Acknowledgements: 

This research was supported by NSF OPP Grant Number 0838811.

Document Information

Document Creation Date

April 2014.

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

Access complete Knowledge Base

Questions? Please contact:
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org