Data Set ID:
NSIDC-0590

Iceberg Capsize Kinematics and Energetics, Version 1

This data set represents a typical single iceberg capsize experiment. Included in this data set are all the parameters of the plastic iceberg's density and dimensions, the density of the water surrounding the iceberg, and the value of gravitational acceleration. The timeseries data consists of all the kinematic and energetic variables as a function of time for the iceberg capsize experiment.

NSIDC does not archive these data.

Parameter(s):
  • Glaciers/Ice Sheets > Icebergs
  • Sea Ice > Icebergs
  • Snow/Ice > Ice Velocity
Data Format(s):
  • NetCDF
Spatial Coverage:
N: 42, 
S: 41, 
E: -87, 
W: -88
Platform(s):Laboratory
Spatial Resolution:Not SpecifiedSensor(s):EX-FH20
Temporal Coverage:
  • 1 January 2011 to 1 January 2014
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Douglas MacAyeal

Geographic Coverage

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.

  • Burton, J. C., J. M. Amundson, D. S. Abbot, A. Boghosian, M. Cathles, S. Correa-Legisos, K. N. Darnell, N. Guttenberg, D. M. Holland, and D. R. MacAyeal. 2012. Laboratory Investigations of Iceberg Capsize Dynamics, Energy Dissipation and Tsunamigenesis, J. Geophys. Res. 117. F01007. https://doi.org/10.1029/2011JF002055

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Detailed Data Description

Laboratory experiments were conducted designed to quantify the stability and energy budget of buoyancy-driven iceberg capsize. Box-shaped icebergs were constructed out of low-density plastic, hydrostatically placed in an acrylic water tank containing freshwater of uniform density, and allowed (or forced, if necessary) to capsize. The maximum kinetic energy (translational plus rotational) of the icebergs was 15 percent of the total energy released during capsize, and radiated surface wave energy was one percent of the total energy released. The remaining energy was directly transferred into the water via hydrodynamic coupling, viscous drag, and turbulence. The dependence of iceberg capsize instability on iceberg aspect ratio implied by the tank experiments was found to closely agree with analytical predictions based on a simple, hydrostatic treatment of iceberg capsize. This analytical treatment, along with the high Reynolds numbers for the experiments (and considerably higher values for capsizing icebergs in nature), indicates that turbulence is an important mechanism of energy dissipation during iceberg capsize and can contribute a potentially important source of mixing in the stratified ocean proximal to marine ice margins. This data set represents a typical single iceberg capsize experiment. Users will find all the parameters of the plastic iceberg's density and dimensions, the density of the water surrounding the iceberg, and the value of gravitational acceleration. The timeseries data consists of all the kinematic and energetic variables as a function of time for the iceberg capsize experiment (Burton et.al. 2012).

Format

Data are provided in Network Common Data Form (NetCDF) (.nc) format.

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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0590_macayeal/ directory. Within this directory, there is one file, Iceberg_capsize.nc.

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File Size

22 KB

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Spatial Coverage

North Latitude: 41.0° N
South Latitude: 42.0° N
East Longitude: 87.0° W
West Longitude: 88.0° W

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Temporal Coverage

Data were collected from 01 January 2011 to 01 January 2014.

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Parameter or Variable

Iceberg Velocity
Iceberg Kinetic Energy

Parameter Description

Variables include the x, y positions and velocities of the iceberg's center of mass (x is the horizontal coordinate and y is the vertical coordinate), the angular orientation and angular velocity of the iceberg relative to the center of mass, the potential energy of the iceberg, the translational kinetic energies, and rotational kinetic energies of the iceberg.

Sample Data Record

Figure 1 is sample data from the BND_data_2011.xls data file.

sample data
Figure 1. Sample Data Record
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Software and Tools

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Data Acquisition and Processing

The laboratory model fjord consisted of an optically clear acrylic aquarium tank that is 244 cm long, 30 cm wide, and 30 cm tall, and has walls that are 1.3 cm thick. Refer to Figure 2. The tank was filled with fresh tap water at room temperature of density ρw = 997 kg m-3. The depth of the water, D, was varied from 11.4 to 24.3 cm. The icebergs used in the experiments were machined out of low-density polyethylene plastic that had a density of Ρi =920 ± 1 kg m-3, which was calculated by measuring the mass and dimensions of the icebergs. For all icebergs the precapsize height, H, and length parallel to the axis of rotation during capsize, L, were held constant at 10.3 cm and 26.7 cm, respectively. The length L was chosen to be slightly shorter than the transverse width of the tank (30 cm) in order to minimize contact friction with the tank walls due to small rotations of the icebergs in the x-y plane. The width of the icebergs, W, was varied from 2.5-10.2 cm, so that the aspect ratio ε = W/H varied from approximately 0.25 to 1.0 (Burton et.al. 2012).

In order to measure the height of the waves produced by a capsizing iceberg, a small, spherical, closed cell styrofoam buoy was placed approximately 25 cm from the iceberg at the beginning of each run. This distance is sufficiently close to the capsize event so that waves reflected off the walls of the tank do not affect our wave amplitude measurements. Due to the very low density of the styrofoam, the buoy was well coupled to the water surface and thus measured the height of the water's surface at that location as a function of t. The experiments were recorded with a Casio EX-FH20 video camera, which was set to record 30 frames per second. The camera resolution was typically 16 pixels cm-1, although we increased the resolution to 93 pixels cm-1 (by zooming in) to measure buoy displacements (Burton et.al. 2012).

In order to track the positions and angular orientations of the icebergs, black sticker dots were placed in each corner of the rectangular face of the icebergs. Refer to Figure 2. The position of each dot was located in each frame of the movie using custom feature-tracking software written in Mathematica (Wolfram Research). Once the positions of the dots were known in every movie frame, the center mass of the iceberg was calculated as the mean position of the four dots, and the angular orientation was calculated by measuring the vector angle between the vertical (gravitational) direction and the direction of the iceberg parallel to the height, H. All angles reported here are measured between the H axis and the vertical, which ranges from -90° to 90°. Although the camera was leveled before each video session, small tilts were still possible within our measurement accuracy. To provide a good measurement of the vertical direction in each video, we used the water level as a perpendicular plane to the vertical. The water level line was extracted from the first frame of each video, fitted to a linear model z = (tan θw) x + b, and the resulting angle θw was subtracted from all other angles measured in the video (Burton et.al. 2012).

Diagram of the laboratory setup
Figure 2. Diagram of the Laboratory Setup (top). The Camera's Field of View (bottom).
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References and Related Publications

Contacts and Acknowledgments

Douglas R. MacAyeal
University of Chicago
Geophysical Sciences
5734 S. Ellis Ave.
Chicago, IL 60637

Acknowledgments: 

This research was supported by NSF OPP Grant Number ANT0944193.

Document Information

DOCUMENT CREATION DATE

August 2014

No technical references available for this data set.
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