Data Set ID:
NSIDC-0656

WDC 06A Mean Grain Size Data, Version 1

The data set comprises the mean grain sizes at the sampled depths derived from vertical thin sections and reflects the final WDC 06A timescale.

NSIDC does not archive these data.

Parameter(s):
  • Ice Core Records > Grain Size
Data Format(s):
  • Excel
Spatial Coverage:
N: -79.467, 
S: -79.467, 
E: -112.085, 
W: -112.085
Platform(s):Laboratory
Spatial Resolution:
  • 20 m
Sensor(s):DSLR
Temporal Coverage:
  • 1 January 2008 to 30 August 2013
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Joan Fitzpatrick, Eric Cravens

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.

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The data set comprises the mean grain sizes at the sampled depths derived from vertical thin sections and reflects the final WDC 06A timescale.

Detailed Data Description

The mean grain areas are based on the processing and analysis of 240 pixel/inch native resolution, 8-bit, RGB images. Users are cautioned that the utility of the mean value is limited. It is provided in this data set to facilitate comparison with older cores for which only the mean grain sizes are provided in the literature. Grain size distributions for the WAIS Divide core are not generally lognormal and the mean-normalized populations are not Gaussian. Refer to the Grain Size Full Population Dataset from WDC06A Core data set for the full grain size information.

Format

The data are in Microsoft Excel (.xls) format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0656_fitzpatrick directory. Within this directory, there is one file, WDC 06A Mean Grain Size.xlsx. The data file consists of two worksheets: "metadata"and "data". Refer to Table 1 for a description of the columns in the "data" worksheet.

Table 1. Column Content Description
Column Description
Nominal Depth (m) Nominal core sample depth in meters
True Top Depth (m) True top depth in meters as determined by the field core processing line (cpl) over the depth interval 120 - 580 m, and the National Ice Core Laboratory (NICL) cpls below this depth
Age before 1950 (yr) Age in years before 1950 based on the WDC06A-3 timescale
Mean Area VERT (mm2) Arithmetic mean of all areas evaluated for all grains in the sample (mm2)
Mean Equivalent Diameter VERT (mm) Arithmetic mean of all equivalent diameters (the diameter of a circle with area equivalent to the area of a given analyzed grain) evaluated for all grains in the sample (mm)
Mean Aspect Ratio (cm) Arithmetic mean of all aspect ratios (maximum caliper dimension divided by minimum caliper dimension) evaluated for all grains in the sample (cm)
Grain Count Number of observations (i.e. grains) in the sample

Refer to the "metadata" worksheet for more information.

File Size

The data file is 63 KB.

Spatial Coverage

The WDC 06A ice core was extracted at the WAIS Divide, Antarctica at 79.28° S and 112.05°.

Spatial Resolution

Spatial resolution is every 20 m along the sample core from 120 m to 3405 m.

Temporal Coverage

Temporal coverage for the data is 1 January 2008 to 30 August 2013. The paleo temporal coverage is 350 ybp to 67,309 ybp.

Parameter or Variable

Parameter

The parameter for the data set is grain size.

Sample Data Record

Refer to Figure 1 for a sample of the data in the file (this image is only a partial representation of the rows in the file). Figure 2 is an image of the "metadata" worksheet.

Sample Data
Figure 1. Sample Data 
Metadata
Figure 2. Metadata Worksheet

Software and Tools

Get Data

The data are available via FTP.

Software and Tools

To view the data, use Microsoft Excel.

Data Acquisition and Processing

Data Acquisition Methods

The WAIS (West Antarctic Ice Sheet) Divide ice core was recovered over five drilling seasons in West Antarctica from 2007/08 to 2011/12, with an additional replicate coring season in 2012/13. The drillhole was completed to a total depth of 3405 m at the end of the 2011/12 season. Processing of the WAIS Divide main core was completed over the course of four summer processing lines in 2008, 2010, 2011 and 2012 at the US National Ice Core Laboratory, Denver, Colorado. 

Derivation Techniques and Algorithms

Processing Steps

The vertical thin sections (VTS) were examined using a Nikon D90 DSLR camera at 20 m intervals along the ice core. The images were assembled using Photoshop™, analyzed using Fovea Pro™ plug-ins for Photoshop™, and summarized using StatMac™ plug-in for Excel™. See Fitzpatrick 2013 for a detailed methodology.

References and Related Publications

Contacts and Acknowledgments

Dr. Joan J. Fitzpatrick
U. S. Geological Survey
Geosciences and Environmental Change Science Center
P.O. Box 25046, DFC, MS 980
Lakewood, CO 80225 U. S. A.

Eric D. Cravens
U. S. Geological Survey
Geosciences and Environmental Change Science Center
P.O. Box 25046, DFC, MS 980
Lakewood, CO 80225 U. S. A.

Acknowledgments: 

This research was supported by NSF Division of Polar Programs (PLR) Grant Number 0539578 and the U. S. Geological Survey Climate and Land Use Change Program.

Document Information

DOCUMENT CREATION DATE

25 February 2013

DOCUMENT REVISION DATE

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

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