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Data Set ID:
NSIDC-0108

Carbon-Isotopic Composition of Atmospheric CO2 since the Last Glacial Maximum, Version 1

These data describe the concentration and carbon-isotopic composition (d13CO2) 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.

Geographic Coverage

Spatial Coverage:
  • N: -77.8, S: -77.8, E: 158.71, W: 158.71

Spatial Resolution: Not Specified
Temporal Coverage: Not specified
Temporal Resolution: Not specified
Parameter(s):
  • Ice Core Records > Carbon Dioxide
  • Atmospheric Chemistry > Carbon and Hydrocarbon Compounds > Carbon Dioxide
  • Ice Core Records > Ice Core Air Bubbles
  • Ice Core Records > Isotopes
Platform(s) GROUND-BASED OBSERVATIONS
Sensor(s): MASS SPECTROMETERS
Data Format(s):
  • Microsoft Excel
  • ASCII Text
Version: V1
Data Contributor(s): Martin Wahlen

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.

Wahlen, M. 2002. Carbon-Isotopic Composition of Atmospheric CO2 since the Last Glacial Maximum, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N54F1NN5. [Date Accessed].

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Detailed Data Description

Format

Each data file contains the following fields:

  • Depth of sample (m)
  • st9810 ice age (kyB1950)
  • Sample air age (kyB1950)
  • CO2 (ppm)
  • δ13CO2 (per mil, VPDB)
  • Mean δ13CO2 (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.

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File Size

Data are in tab-delimited ASCII and Excel formats:

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

Total data set size is 27 KB.

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Spatial Coverage

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

Study Area Location Map:

Taylor Dome, Antarctica

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Temporal Coverage

δ13CO2 and CO2 data range from 27 kyBP to 1.3 kyBP. δ13CO2 samples were collected between 09 February 1998 and 25 May 1998. CO2 concentration data were collected between 07 January 1998 and 29 July 1998.

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Parameter or Variable

The data file contains the following variables:

  • Depth of sample (m)
  • st9810 ice age (kyB1950)
  • Sample air age (kyB1950)
  • CO2 (ppm)
  • δ13CO2 (per mil, VPDB)
  • Mean δ13CO2 (per mil, VPDB)
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Software and Tools

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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 δ) 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 δ 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. δ13CO2 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 δ13CO2 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. 1988Schwander, 1989) was determined by using the values of δ15N2 of air trapped in Taylor Dome ice from Sucher (1997), following the approach of Sowers and Bender (1989). The gravitational correction for δ13CO2 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 δ uncertainty in the reported δ13CO2 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 δuncertainty of 0.060 percent, and a triplicate analysis of the sample with an air age of 27.4 kyBP has a 1 δ 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 δ18O of the ice with the well-dated GISP2 record, and matching atmospheric CH4concentrations and δ18O of O2 with variations seen in the GISP2 record (Steig et al. 1998).

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References and Related Publications

Contacts and Acknowledgments

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

Acknowledgements: 

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

Document Information

Document Creation Date:

June 2002

Document Revision Date:

July 2002

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