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Carbon-Isotopic Composition of Atmospheric CO2 since the Last Glacial Maximum

Data Set Summary

These data describe the concentration and carbon-isotopic composition (delta13CO2) of atmospheric CO2 from air trapped in ice between 27,000 and 1,300 years before present from Taylor Dome, Antarctica. Data are used to investigate the causes of the CO2 concentration increase that occurred during the transition between the last glacial maximum (LGM) and the Holocene. Data are in tab-delimited ASCII and Excel formats, and are available via ftp.

Citing These Data:

Please cite these data as follows:

Wahlen, M. 2002. Carbon-Isotopic Composition of Atmospheric CO2 since the Last Glacial Maximum. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N54F1NN5.

Dr. Wahlen asks that users cite any use of the CO2 concentration and delta13CO2 data between 27 kyBP and 11 kyBP with:

Smith, H. J., H. Fischer, D. Mastroianni, B. Deck, and M. Wahlen. 1999. Dual modes of the carbon cycle since the Last Glacial Maximum. Nature 400: 248-250.

Please cite any use of the CO2 concentration and delta13CO2 data between 10.6 kyBP and 1.3 kyBP with:

Indermühle, A., T. Stocker, H. Fischer, H. Smith, F. Joos, M. Wahlen, B. Deck, D. Mastroianni, J. Tschumi, T. Blunier, R. Meyer, and B. Stauffer. 1998. Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica. Nature 398: 121-126.

Overview Table

Category Description
Parameter(s)
  • Depth of sample (m)
  • st9810 ice age (kyB1950)
  • Sample air age (kyB1950)
  • CO2 (ppm)
  • delta13CO2 (per mil, VPDB)
  • Mean delta13CO2 (per mil, VPDB)
Spatial coverage Samples were extracted from ice cores at Taylor Dome, Antarctica.
Temporal coverage delta13CO2 and CO2 data range from 27 kyBP to 1.3 kyBP.
Data format Data are in tab-delimited ASCII and Excel formats.
File sizes Total data set size is 27 KB (2 KB ASCII file and 25 KB Excel file).
Procedures for obtaining data Data are available via ftp

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments:

Investigator Name(s) and Affiliation(s):

Martin Wahlen
Geological Research Division
Scripps Institution of Oceanography
La Jolla, CA 92093-0220

Technical Contact:

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgments:

This research was supported by NSF grant OPP-9615292 ("Carbon Dioxide and Carbon Isotopes in the Taylor Dome and Vostok Ice Cores").

2. Detailed Data Description:

Format and File Sizes:

Data are in tab-delimited ASCII and Excel formats. Total data set size is 27 KB:

  • "TD_data.txt" (ASCII file, 2 KB)
  • "TD_data.xls" (Excel file, 25 KB)

Each data file contains the following fields:

  • Depth of sample (m)
  • st9810 ice age (kyB1950)
  • Sample air age (kyB1950)
  • CO2 (ppm)
  • delta13CO2 (per mil, VPDB)
  • Mean delta13CO2 (per mil, VPDB)

The st9810 combined time scale is derived from geophysical measurements, gas-correlation with the GISP2 layer-counted chronology (central Greenland), and interpolation using gas and 10Be control points. Details are given in Steig et al. 1998. Ages are in thousands of years (ka), nominally referenced to 1950 AD (0 ka).

VPDB is a scale recognized by the National Institute for Standards and Technology (NIST) that is used for reporting relative abundances of 13C or 18O via the delta notation.

Spatial Coverage:

Samples were extracted from ice cores from Taylor Dome, Antarctica (77 degrees, 48 minutes south latitude; 158 degrees, 43 minutes east longitude), drilled in 1993 to 1994.

Study Area Location Map:

Taylor Dome, Antarctica

Temporal Coverage:

delta13CO2 and CO2 data range from 27 kyBP to 1.3 kyBP. delta13CO2 samples were collected between 09 February 1998 and 25 May 1998. CO2 concentration data were collected between 07 January 1998 and 29 July 1998.

Parameter or Variable:

The data file contains the following variables:

3. Data Access:

Data are available via ftp.

Related Data Collections:

Please see the Ice Core Gateway for other Antarctic ice core data.

4. Data Acquisition and Processing:

The methods used for determining the CO2 concentration and carbon-isotopic composition of air trapped in ice are described in detail in Wahlen et al. (1991) and Smith et al. (1997). Briefly, these techniques involve the dry extraction of trapped gas by crushing ice samples at low temperature in order to avoid exposing the gas to liquid water, in which CO2 is soluble. CO2 concentration measurements have an internal precision of ± 3 parts per million by volume (ppmv, 2 sigma) and are calculated by comparison to three standards of precisely known compositions that are run with every sample. The Craig-corrected carbon-isotopic measurements, performed on a VG Prism II isotope ratio mass spectrometer, have a 1 sigma precision of ±0.075 percent, based on numerous analyses of the CO2 separated from an atmospheric air standard exposed to uncrushed ice, in order to simulate the conditions of a sample run and to check for fractionation during extraction. delta13CO2 is reported in normal delta notation as the per mil difference between the isotopic composition of the sample and standard VPDB carbon, [(13C/12C)sample/(13C/12C)VPDB - 1] * 1000).

The delta13CO2 values were corrected for the gravitational separation of gases of different masses in the firn, and for the presence of N2O, which results in isobaric interferences with CO2 during mass spectrometry. Gravitational separation in the firn (Craig et al. 1988; Schwander, 1989) was determined by using the values of delta15N2 of air trapped in Taylor Dome ice from Sucher (1997), following the approach of Sowers and Bender (1989). The gravitational correction for delta13CO2 is approximately 0.005 percent per meter. Carbon-isotopic data are corrected for the presence of N2O on the basis of calibrations performed in Wahlen's laboratory on CO2-N2O mixtures. The N2O concentrations of atmospheric air used for this correction, adapted from Leuenberger and Siegenthaler (1988), are linear interpolations of the following concentrations and dates: 275 ppb (0 kyBP to 9.25 kyBP) and 200 ppb (16.1 kyBP to 27.2 kyBP). The N2O correction is approximately 0.001 percent per ppb of N2O. The total 1 sigma uncertainty in the reported delta13CO2 of a single sample, including uncertainties in the gravitational and N2O corrections, is 0.085 percent. Duplicate analyses of samples with air ages of 2.19 kyBP and 17.2 kyBP have a 1 sigma uncertainty of 0.060 percent, and a triplicate analysis of the sample with an air age of 27.4 kyBP has a 1 sigma uncertainty of 0.049 percent. The depth-age scale and air age-ice age differences were calculated using a combination of flow modeling, correlating variations in the delta18O of the ice with the well-dated GISP2 record, and matching atmospheric CH4 concentrations and delta18O of O2 with variations seen in the GISP2 record (Steig et al. 1998).

5. References and Related Publications:

Craig, H., Y. Horibe, and T. Sowers. 1988. Gravitational separation of gases and isotopes in polar ice caps. Science 242: 1675-1678.

Indermühle, A., T. Stocker, H. Fischer, H. Smith, F. Joos, M. Wahlen, B. Deck, D. Mastroianni, J. Tschumi, T. Blunier, R. Meyer, and B. Stauffer. 1998. Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica. Nature 398: 121-126.

Leuenberger, M. and U. Siegenthaler. 1988. Ice-age atmospheric concentration of nitrous oxide from an Antarctic ice core. Nature 360: 449-451.

Schwander, J. 1989. The environmental record in glaciers and ice sheets, eds. H. Oeschger and C. C. Langway, Jr. John Wiley and Sons, Ltd., pp. 53-67.

Smith, H. J., H. Fischer, D. Mastroianni, B. Deck, and M. Wahlen. 1999. Dual modes of the carbon cycle since the Last Glacial Maximum. Nature 400: 248-250.

Smith, H., M. Wahlen, D. Mastroianni, and K. Taylor. 1997. The CO2 concentration of air trapped in GISP2 ice from the LGM-Holocene transition. Geophysical Research Letters 24(1): 1-4.

Sowers, T. and M. Bender. 1989. Elemental and isotopic composition of occluded O2 and N2 in polar ice. Journal of Geophysical Research 94: 5137-5150.

Steig, E., E. Brook, J.W.C. White, C. Sucher, M. Bender, S. Lehman, D. Morse, E. Waddington, and G. Clow. 1998. Synchronous climate changes in Antarctica and the North Atlantic. Science 282(5386): 92-95.

Sucher, C. 1997. Trapped gases in the Taylor Dome Ice Core: Implications for East Antarctic climate change. Master's Thesis, University of Rhode Island.

Wahlen, M., D. Allen, and B. Deck. 1991. Initial measurements of CO2 concentrations (1530 to 1940 AD) in air occluded in the GISP 2 ice core from central Greenland. Geophysical Research Letters 18(8): 1457-1460.

6. Document Information:

Document Creation Date:

June 2002

Document Revision Date:

July 2002

Document Curator:

NSIDC writers, nsidc@nsidc.org

Document URL:

http://nsidc.org/data/docs/agdc/nsidc0108_wahlen/index.html