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

Summary

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.

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title, publisher (NSIDC), and media format.

Sowers, T. 2007. Carbon-13 isotopic composition of atmospheric methane in firn air, Siple Dome, Antarctica. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5ST7MR2.

Overview Table

Category	Description
Data format	Microsoft Excel and Microsoft Word
Spatial coverage and resolution	Southernmost Latitude: 81.4030° S Northernmost Latitude: 81.4030° S Westernmost Longitude: 148.3023° W Easternmost Longitude: 148.3023° W Maximum depth: 122.08 mbs
Temporal coverage and resolution	Data collection: January 1995 and January 2001 Data coverage: 1820 to 2001
File naming convention	2007_Sowers.xls
Data file size	Approximately 37.5 KB
Parameter	δ13C of CH4
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

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

Technical Contact

Acknowledgements

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

2. Detailed Data Description

Format

Data are available in Microsoft Excel and Microsoft Word formats.

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)

File Descriptions

This data set consists of the following two files, available via FTP.

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

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.

Temporal Coverage

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

Parameter or Variable

Investigators measured δ¹³C of atmospheric CH₄ of 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).

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.

Quality Assessment

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

3. Data Access and Tools

Data Access

Data are available via FTP.

Related Data Collections

• Firn Air Inert Gas and Oxygen Observations from Siple Dome, 1996, and the South Pole, 2001
• Firn Air Isotope and Temperature Measurements from Siple Dome and South Pole
• Siple Dome Core Date from Measurement of the d18O of Paleoatmospheric O2
• Siple Dome Highlights: Stable isotopes

4. Data Acquisition and Processing

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

Sensor or Instrument

Mass spectrometer

Data Acquisition Methods

See investigator-provided documentation, PSU_method.doc.

5. References and Related Publications

Leckrone, K. J., and J. M. Hayes. 1998. Water-induced errors in continuous flow carbon isotope ratio mass spectrometry. Analytical Chemistry 70, 2737-2744.

Miller, J. B., K. A. Mack, R. Dissly, J. W. C. White, E. J. Dlugokencky, and P. Tans. 2002. Development of analytical methods and measurements of ¹³C/¹²C in atmospheric CH₄ from the NOAA Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network. Journal of Geophysical Research 107, 4178-4193.

Rice, A., A. A. Gotoh, H. O. Aijie, and S. C. Tyler. 2001. High-precision continuous-flow measurements of δ¹³C and δD of atmospheric CH₄ Analytical Chemistry 73, 4104-4110.

Santrock, J., S. A. Studley, and J. M. Hayes. 1985. Isotopic analyses based on the mass spectrum of carbon dioxide Analytical Chemistry 57, 1444-1448.

Sowers, T., S. Bernard, O. Aballain, J. Chappellaz, J.-M. Barnola, and T. Marik. 2005. Records of the δ¹³C of atmospheric CH₄ over the last 2 centuries as recorded in Antarctic snow and ice. Global Biogeochemical Cycles 19, doi:10.1029/2004GB002408.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

CMDL	Climate Monitoring and Diagnostics Laboratory
FTP	File Transfer Protocol
LGGE	Laboratory of Glaciology and Geophysical Environment
mbs	Meters below sea level
NOAA	National Oceanic and Atmospheric Administration
NSF	National Science Foundation
NSIDC	National Snow and Ice Data Center
OPP	Office of Polar Programs
PSU	Pennsylvania State University
URL	Uniform Resource Locator
VPDB	Vienna Pee Dee Belemnite (VPDB), the scale for reporting 13C relative abundances via the delta notation
‰	per mil (one part per thousand)

Document Creation Date

July 2007

Document URL

http://nsidc.org/data/docs/agdc/nsidc0310_sowers/index.html