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Data Set ID:

Carbon-13 Isotopic Composition of Atmospheric Methane in Firn Air, South Pole and Siple Dome, Antarctica, Version 1

This data set includes records of the delta carbon-13 (δ13C) of methane (CH4) in firn air from the South Pole and trapped in bubbles in a short ice core from Siple Dome, Antarctica. Using two firn air samples, one from January 1995 and the other from January 2001, investigators reconstructed records of the isotopic composition of paleoatmospheric methane covering the last 2 centuries, from 1820 to 2001.

Data are in Microsoft Excel and Microsoft Word formats and are available via FTP.

Geographic Coverage

  • Ice Core Records > Isotopes > Carbon-13 of Methane
Spatial Coverage:
  • N: -81.403, S: -81.403, E: -148.3023, W: -148.3023

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 January 1995 to 31 January 1995
  • 1 January 2001 to 31 January 2001
Temporal Resolution: Not specified
Data Format(s):
  • Microsoft Excel
  • Microsoft Word
Platform(s) LABORATORY
Version: V1
Data Contributor(s): Todd Sowers

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.

Sowers, T. A. 2007. Carbon-13 Isotopic Composition of Atmospheric Methane in Firn Air, South Pole and Siple Dome, Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: [Date Accessed].

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Detailed Data Description


Data are available in Microsoft Excel and Microsoft Word formats.

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Data File Structure

Each of the two data records contained in 2007_Sowers.xls consist of the following three columns.

Column title Description
Depth (mbs) Sample depth measured in units of meters below sea level
d13CH4 (‰ VPDB) delta carbon-13 (δ13C) of methane (CH4), in units of per mil Vienna Pee Dee Belemnite (VPDB), the scale for reporting 13C relative abundances via the delta notation
± (‰) 1 sigma uncertainty, in units of per mil (one part per thousand)
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File Descriptions

This data set consists of the following two files:

File Name Approximate file size Description
2007_Sowers.xls 37.5 KB Data file in Microsoft Excel format
PSU_method.doc 64.5 KB Investigator-provided data acquisition documentation in Microsoft Word format
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Spatial Coverage

Investigators collected samples of firn air in trapped bubbles from a short ice core from Siple Dome, Antarctica.

Southernmost Latitude: 81.4030° S
Northernmost Latitude: 81.4030° S
Westernmost Longitude: 148.3023° W
Easternmost Longitude: 148.3023° W

The maximum depth of the samples collected is 122.08 mbs.

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Temporal Coverage

Investigators collected two firn air samples, one in January 1995 and the other in January 2001.

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Parameter or Variable

Investigators measured δ13C of atmospheric CHof firn air in trapped bubbles from a short ice core from Siple Dome, Antarctica. This record corresponds to the time period between 1820 and 2001.

The concentrations of methane gas increased at an exponential rate during the anthropogenic period. High resolution measurements of the carbon-13 isotopic composition of methane from shallow ice cores will help to determine the relative contributions of biogenic (wetlands, rice fields, and ruminants) and abiogenic (biomass burning and natural gas) methane emissions to this increase.

Sample Data Record

These sample data were retrieved in January 1995.

Depth d13CH4
(mbs) (‰ VPDB) ± (‰)
0 -47.2099 0.1
20.1 -47.476 0.04
39.82 -48.121 0.03
59.99 -48.689 0.03
83.04 -49.343 0.06
89.88 -49.75 0.11
100.2 -50.153 0.03
105.38 -50.352 0.09
108.02 -50.29 0.12
110.03 -50.564 0.04

Sample Data Plot

The following sample data plot and caption are taken directly from Sowers et al. (2005).

Plot of d13C of CH4 data
Results of CH4 and δ13CH4 analyses on South Pole Firn air. A) CH4 data were measured on the 1995 samples at NOAA/CMDL (Tans, P., personal communication). The red and blue lines are the model predicted CH4 profiles from the Battle et al., (1996) (blue) and Rommelare et al., 1997 (red) firn models. B) δ13CH4 measurements at LGGE (red, 1995 and 2001) and PSU (blue, 2001 only).  Also plotted with a solid black line is the inferred firn air d13CH4 profile (2001) using the BOSCAGE-8 atmospheric output with 30% of total biomass burning assigned to anthropogenic activities and the Battle et al., 1996 firn air model. C) The Δδ13CH4 data are the difference between the 2001 and 1995 LGGE data.
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Software and Tools

Quality Assessment

Refer to Sowers et al. (2005) for quality assessment information.

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Data Acquisition and Processing

Refer to Sowers et al. (2005) for detailed information on theory of measurements, instrument descriptions, derivation techniques, and processing steps.

Data Acquisition Methods

See investigator-provided documentation, PSU_method.doc.

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Sensor or Instrument Description

Mass spectrometer

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References and Related Publications

Contacts and Acknowledgments

Todd A. Sowers
Department of Geosciences and the Environment Systems Institute
Pennsylvania State University
237 Deike Building 
University Park, PA 16802 USA


This research was funded by the National Science Foundation (NSF) Office of Polar Programs (OPP) grant 9526556 awarded to Todd Sowers.

Document Information

Document Creation Date

July 2007

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