Atmospheric CO₂ from Flask Air Samples at Cape Matatula, American Samoa

Graphics    Data

C.D. Keeling and T.P. Whorf

Carbon Dioxide Research Group, Scripps Institution of Oceanography, University of California, La Jolla, California 92093-0444, U.S.A.

Period of Record

1981-2001

Methods

Atmospheric CO₂ samples were collected at approximately weekly intervals. Samples are collected in 5-L evacuated glass flasks, and then returned to the Scripps Institution of Oceanography (SIO) where CO₂ concentrations have been determined using an Applied Physics Corporation (APC) nondispersive infrared gas analyzer. Further information on measurements, calibration procedures and analysis is available in the references listed below.

American Samoa (Cape Matatula), U.S. Territory,
Pacific Ocean rocky costal promontory
14°15' S, 170°34' W
30 m above MSL

Trends

The average of unflagged data for the first full year of measurements (1982) was 340.6 ppmv; values for 2001 averaged 369.8 ppmv, for an upward trend of 1.54 ppmv/year. Graphics here show the first and last year of data, to display the change in mean over time and the annual patterns. Long term trend curves are better displayed using the SIO's monthly averaged data. The annual pattern of CO₂ at American Samoa is unlike that for other stations. It does not have a single, clearly defined peak during the late winter months. This is because the air arriving at American Samoa does not come from a single dominant source, but rather from diverse sources in both hemispheres, and possibly includes air that has been "circulating around" within the tropics for as much as a month or more before arriving at the sampling location. For more information, see Manning et al., 2003.

References

• Guenther, P.R., A. Bollenbacher, C.D. Keeling, and D. Moss. 2002 Technical Report: Infrared Analyses of NOAA Primary CO₂-in-Air Reference Gas Standards at SIO, 1991-1999.
• Guenther, P.R., G. Emanuele, and C.D. Keeling. 2002. Alternative Formulation of 1985-1999 Calibrations after Re-calibration of 4cc Chanber Volume of Mercury Manometer. Addendium to: Scripps Reference Gas Calibration System for Carbon-Dioxide-in Nitrogen and Carbon Dioxide-in-Air Standards: Revision of 1999, February 2002.
  See Diagram of the constant-volume mercury-column manometer.
• Keeling, C.D., R.B. Bacastow, A.F. Carter, S.C. Piper, T.P. Whorf, M. Heimann, W.G. Mook, and H. Roeloffzen. 1989. A three-dimensional model of atmospheric CO₂ transport based on observed winds: 1. Analysis of observational data. In D.H. Peterson (ed.), Aspects of Climate Variability in the Pacific and the Western Americas, 165-236, Geophysical Monograph 55, American Geophysical Union, Washington, DC.
• Keeling, C.D., T.P. Whorf, M. Wahlen & J. van der Plicht. 1995. Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980, Nature 375, 666-670.
• Keeling, C.D., S.C. Piper, R.B. Bacastow, M. Wahlen, T.P. Whorf, M. Heimann, and H.A. Meijer. 2001. Exchanges of Atmospheric CO₂ and ¹³CO₂ with the Terrestrial Biosphere and Oceans from 1978 to 2000. I. Global Aspects. SIO Reference No. 01-06 (Revised from SIO Reference No. 00-21), June 2001.
• Keeling, C.D., P.R. Guenther, G. Emanuele III, A. Bollenbacher, and D.J. Moss. 2002. Scripps Reference Gas Calibration System for Carbon Dioxide-in-Nitrogen and Carbon Dioxide-in-Air Standards: Revision of 1999 (with Appendix and Addendum). SIO Reference Series No. 01-11.
  See Diagram of the constant-volume mercury-column manometer.
• Manning, A.C.., R.F. Keeling, L.E. Katz and W.J. Paplawsky. 2003. Interpreting the seasonal cycles of atmospheric oxygen and carbon dioxide concentrations at American Samoa Observatory. Geophysical Research Letters, Vol. 30, No. 6, pp 66-1 - 66-4.

10/2004