Data Set ID:
NSIDC-0603

Average Annual Layer Thickness of the WAIS Divide Ice Core from Visual Stratigraphy, Version 1

This data set includes ~50 m averaged annual layer thicknesses down to 3403 m depth at the West Antarctic Ice Sheet (WAIS) Divide ice core as observed visually using diffuse transmitted light opposite a planed surface in a light-shielded booth in the core-processing line at the National Ice Core Lab in Denver, CO.

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Geographic Coverage

Parameter(s):
  • Snow/Ice > Ice Depth/Thickness > Thickness
Spatial Coverage:
  • N: -79.4676, S: -79.4676, E: -112.0865, W: -112.0865

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 January 2005
Temporal Resolution: Varies
Data Format(s):
  • Microsoft Excel
Platform(s) GROUND-BASED OBSERVATIONS
Sensor(s): VISUAL OBSERVATIONS
Version: V1
Data Contributor(s): Matthew Spencer
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.

  • Fitzpatrick, J., D. E. Voigt, J. Fegyveresi, N. T. Stevens, M. Spencer, J. Cole-Dai, R. Alley, G. E. Jardine, E. D. Cravens, L. Wilen, T. J. Fudge, and J. McConnell. 2014. Physical properties of the WAIS Divide ice core, Journal of Glaciology. 60. 1181-1198. https://doi.org/10.3189/2014JoG14J100

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Detailed Data Description

The first column in the data file is depth in meters of the average annual layer thickness to the nearest meter. The second column contains the ~50 meter averaged annual layer thickness for the corresponding adjacent depth in the first column. The second column thicknesses are also in meters, with a precision calculated to the nearest millimeter.

Format

Data are in Microsoft Excel 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/nsidc0603_spencer/ directory. Within this directory, there is one file: WAIS Divide 50 m averaged annual layer thickness from visual stratigraphy.xlsx.

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File Size

The data file is 38 KB.

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Spatial Coverage

West Antarctic Ice Sheet Divide ice core. WAIS Divide is situated 24 km west of the Ross–Amundsen ice flow divide and 160 km east of the Byrd ice core site.

79.4676° South, 112.0865° West

Surface elevation at drill site: 1766 m.

Spatial Resolution

Depth of WAIS Divide deep ice core is 3405 m, with annual layer thickness averaged every ~50 m.

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Temporal Coverage

Temporal coverage of the ice core is from 67,748 calibrated years B. P. to 2005.

Temporal Resolution

The temporal resolution varies.

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Parameter or Variable

Parameter Description

50 meter averaged annual layer thickness in meters, calculated to the nearest millimeter.

Sample Data Record

Figure 1 shows a sample from the WAIS Divide 50 m averaged annual layer thickness from visual stratigraphy.xlsx data file. The first column contains depth measurements in meters, and the second column contains 50 meter averaged annual layer thickness for the corresponding depth in the first column. These thicknesses were averaged from the specified depth in the row to the depth of entry in the next row, so each depth in the column is the top depth for the averaged layer thickness reported, i.e. 0 depth is the measurement from the top down to 48 m. Duplicate depths reflect two measurements to within <1 m with different averaged layer thicknesses.

sample data
Figure 1. Sample Data Record
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Software and Tools

The data file can be opened using any software capable of reading Microsoft Excel files.

Quality Assessment

The visual stratigrapher considered each annual layer's depth to have an uncertainty at least 10% as great as the corresponding thickness. However, averaged over 50 m, this uncertainty might be reduced. Comparisons with the official depth-age scale for WAIS Divide, derived through other means (electrical, isotopic, etc.), suggests the actual uncertainty in the annual layer thickness are within 10% for most of the core, but not for the brittle-ice depths (650–1300 m), where the uncertainty likely exceeds 20%.

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Data Acquisition and Processing

Data Acquisition Methods

Average annual layer thicknesses were observed visually using diffuse transmitted light opposite a planed surface in a light-shielded booth in the core-processing line at the National Ice Core Lab in Denver, Colorado, USA. Visual stratigraphy of each approximately 1 m long segment of the entire WAIS Divide main core was conducted. Data reported here are annual thicknesses averaged over ~50 m, which is the depth range of the log books used for the core processing line. See Taylor et al. 2004 for more information on the methodology.

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Derivation Techniques and Algorithms

A comparison of the annual-layer thickness determined by visual stratigraphic means versus the annual-layer thickness as determined from the WDC06A–7 depth–age scale (which was produced without input from the visual stratigraphy results) is presented in Figure 2. Data in Figure 2 were averaged over ~50 m intervals, which is the depth range covered per logbook used in the visual stratigraphy (Fitzpatrick et al. 2014).

comparison of annual layer thickness
Figure 2: Comparison of mean annual-layer thicknesses as derived from visual stratigraphy and from the WDC06A-7 time scale (Fitzpatrick et al. 2014).

Error Sources

Near some depths, the exact location of the layer closest to each end of each core section was less accurately observed than those farther into the core. Thicknesses of years spanning two core sections were omitted in calculating average thicknesses, yet this has little effect on the averaged data (Fitzpatrick et al. 2014).

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References and Related Publications

Contacts and Acknowledgments

Matthew K. Spencer
Lake Superior State University
325 Crawford Hall
Sault Ste. Marie, MI 49783

Acknowledgments: 

This effort was aided by previous experience the stratigrapher gained while visually examining the entire ice core returned from Siple Dome, Antarctica as described in Taylor et al. 2004.

Document Information

Document Creation Date

11 March 2015

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