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Data Set ID:
NSIDC-0536

West Antarctica Ice Core and Climate Model Data, Version 1

This data set includes ice core water isotope data from Antarctic ice cores covering the last 200 to 2000 years.

Geographic Coverage

Parameter(s):
  • Ice Core Records > Isotopes > Ice Core
  • Ocean/Lake Records > Oxygen Isotopes
Spatial Coverage:
  • N: -65, S: -90, E: 180, W: -180

Spatial Resolution: Not Specified
Temporal Coverage: Not specified
Temporal Resolution: Not specified
Data Format(s):
  • ASCII Text
Platform(s) GROUND-BASED OBSERVATIONS
Sensor(s): CORING DEVICES
Version: V1
Data Contributor(s): Eric Steig
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.

Steig, E. J. 2013. West Antarctica Ice Core and Climate Model Data, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5QJ7F8B. [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.

  • Steig, E. J. et al. 2013. Recent Climate and Ice-sheet Change in West Antarctica Compared to the Past 2000 Years, Nature Geoscience. . . http://dx.doi.org/10.1038/NGEO1778

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Detailed Data Description

Changes in atmospheric circulation over the past five decades have enhanced the wind-driven inflow of warm ocean water onto the Antarctic continental shelf, where it melts ice shelves from below. Atmospheric circulation changes have also caused rapid warming over the West Antarctic Ice Sheet, and contributed to declining sea-ice cover in the adjacent Amundsen-Bellingshausen seas. It is unknown whether these changes are part of a longer-term trend. This data set uses water isotope (δ18O) data from an array of ice-core records to place recent West Antarctic climate changes in the context of the past two millennia. We find that the δ18O of West Antarctic precipitation has increased significantly in the past 50 years, in parallel with the trend in temperature, and was probably more elevated during the 1990s than at any other time during the past 200 years. However, δ18O anomalies comparable to those of recent decades occur about one percent of the time over the past 2,000 years. General circulation model simulations suggest that recent trends in δ18O and climate in West Antarctica cannot be distinguished from decadal variability that originates in the tropics. We conclude that the uncertain trajectory of tropical climate variability represents a significant source of uncertainty in projections of West Antarctic climate and ice-sheet change. (Steig 2013)

Ice-core locations are shown by filled circles. Blue shading shows the main Siple Coast and Amundsen Sea ice streams. Ice shelves are shaded grey. The inset map shows the locations of well-dated, annually resolved ice cores for which there are δ18O data available to at least 1994. The location of the WAIS Divide (WD) ice core is shown with a white-edged circle, the Pine Island Glacier (PIG) location is shown by the initials PIG, and the Byrd weather station location is shown by an open circle. (Steig 2013)

site map
Figure 1. Map of West Antarctica Showing the Ice Core Locations
Format

Data are provided in:

  • American Standard Code for Information Interchange (ASCII) Text (.txt)
  • Network Common Data Form (NetCDF) (.nc and .cdf)
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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/nsidc0536_steig/ directory. Within this directory, there are 17 text files. The ITASE data files contain five columns of data: Depth_top, Depth_bottom, Age_top, Age_bottom, dD (per mil), and d18O (per mil). The Steig_2013 data file contains annually averaged water isotope data for all the cores. The WAIS_D_2005A_d180.txt data file contains four columns of data: Top Age (yrs before 2000.0), Bottom Age Top Depth (m), Bottom Depth (m), and del18O (per mil). Figure 2 below shows the full directory stucture for this data set.

directory structure
Figure 2. File and Directory Structure

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File Naming Convention

This section explains the file naming convention used for this product with an example.

Example File Name: ITASE_1999_1.txt

ITASE_xxxx_yy.txt

Refer to Table 1 for the valid values for the file name variables listed above.

Where:

Table 1. File Naming Convention
Variable
Description
ITASE
Cores collected through the U.S. ITASE (International Trans-Antarctic Expedition) project.
xxxx
The year that field work commenced for that core; however, the core was often drilled in January of the following year.
yy
Refers to the order in which the cores were drilled, for example, 1 is the first core drilled, 2 is the second cored drilled and so on.
.txt
ASCII Text File

This section explains the file naming convention used for this product with an example.

Example File Name: WAIS_D_2005A_d180.txt

Refer to Table 2 for the valid values for the file name variables listed above.

Where:

Table 2. File Naming Convention
Variable
Description
WAIS
Cores collected from the WAIS (West Antarctic Ice Sheet)
D
Stands for Divide
2005A
Refers to the first A ice core drilled in 2005
d180
delta18O per mil
.txt
ASCII Text File
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File Size

See Figure 2.

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Volume

1.79 MB

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Spatial Coverage

West and East Antarctica
Southernmost Latitude: 60° S
Northernmost Latitude: 90° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

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Temporal Coverage

Data Set Temporal Coverage
Data were collected from 15 December 1999 to 15 June 2011.

Paleo Temporal Coverage
01 January 1800 to 31 December 2010

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Parameter or Variable

Depth (m)
Age (calendar years)
Oxygen Isotopes (delta18O per mil)
Hydrogen Isotopes (deltaD per mil)

Sample Data Record

Figure 3 is a sample of the ITASE_2000_4 data file.

sample data record
Figure 3. Sample Data Record of the ITASE_2000_4 Data File
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Software and Tools

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Data Acquisition and Processing

Ice-core data presented in this data set include both previously published and new analyses of ice and firn cores, primarily from the United States' International Trans-Antarctic Expedition (ITASE). The development of depth-age scales for these cores was conducted using multi-parameter high-resolution chemistry. Water stable-isotope concentrations were measured by mass spectrometry and laser spectroscopy at the University of Washington, and are reported as δ18O deviations in per mil (h) from Vienna Standard Mean Ocean Water (VSMOW), normalized to VSMOW and Standard Light Antarctic Precipitation (SLAP), where δ18O=R/RVSMOW-1, R is the abundance ratio of 18O/16O in water, δ18OVSMOW =0:0% and δ18OSLAP=-55.5%. The ice-core δ18O composite records were produced by normalizing the mean over the data overlap period common to all cores. The spatial distribution of decadal-mean δ18O data from West Antarctic cores is indistinguishable from a normal distribution (p<0:05) based on a Lilliefors goodness-of-fit test. We use a one-tailed Student's t -test of the null hypothesis that a given decade mean comes from the same population as the 1990s (19912000) mean. Use of the non-parameteric Wilcoxon rank-sum test yields indistinguishable results. The significance level p of reported correlations accounts for the degrees of freedom reduced by the quotient (1-r1r2)/(1+r1r2), where ri is the lag-1 autocorrelation of time series i. The general circulation modelling results are from experiments with the ECHAM4.6 atmospheric GCM, at a horizontal resolution of T42 (~2:8°latitudex2.8° longitude) with 19 vertical levels, using observed Sea Surface Temperature (SST) as a boundary condition. In experiments using only tropical SSTs as the boundary condition, the atmospheric GCM is coupled to a slab ocean in the extratropics.

Data Acquisition Methods

Ice cores were collected over a period of 10 years under the US ITASE (International TransAntarctic Scientific Expedition) program. All oxygen isotope analyses were by mass spectrometry using equilibration with CO2.  All hydrogen isotope analyses were by reduction on Cr followed by mass spectrometry of H2, or by laser spectroscopy of H2O.   Resolution of the data is subannual (~3 cm/sample in most cases).

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Sensor or Instrument Description

Mass Spectrometry

An analytical technique that produces spectra of the masses of the molecules comprising a sample of material. The spectra are used to determine the elemental composition of a sample, the masses of particles and of molecules, and to elucidate the chemical structures of molecules, such as peptides and other chemical compounds. Mass spectrometry works by ionizing chemical compounds to generate charged molecules or molecule fragments and measuring their mass-to-charge ratios.

Laser Spectroscopy

A source of high-intensity optical, infrared, or ultraviolet radiation produced as a result of stimulated emission maintained within a solid, liquid, or gaseous medium. The photons involved in the emission process all have the same energy and phase so that the laser beam is monochromatic and coherent, allowing it to be brought to a fine focus

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References and Related Publications

Contacts and Acknowledgments

Eric Steig
University of Washington 
Earth and Space Sciences
70 Johnson HallBox 351310 
Seattle, WA 98195

Acknowledgments: 

This research was supported by NSF OPP Grant Number 0837988.

Document Information

Document Creation Date

August 2013

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No FAQs or How Tos available for this data set.

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