Measurements of atmospheric O2/N2
Abstract
Improvements made to an established mass spectrometric method for measuring changes in atmospheric O2/N2 are described. With the improvements in sample handling and analysis, sample throughput and analytical precision have both been increased. Aliquots from each pair of flasks are repeatedly measured over a period of two weeks, with an overall standard error in each flask of +/- 4.5 per meg, corresponding to about 1 ppm O2 in air. Records of changes in O2/N2 from six global sampling stations (Barrow, American Samoa, Cape Grim, Amsterdam Island, Macquarie Island, and Syowa Station) are presented. Combined with measurements of CO2 from the same sample flasks, ocean and land carbon uptake were calculated from the two sampling stations with the longest records (Barrow and Cape Grim). The calculations take into account estimates of O2 outgassing from the oceans during the 1990's due to global warming (0.29 +/- 0.4 x 1014 mol of O2 yr-1; Keeling and Garcia 2002). From 1994-2001, the averaged ocean and land uptake of CO2 was 1.6 +/- 0.6 and 1.2 +/- 0.4 GtC yr-1, respectively. Interannual variability exists in both the ocean and land uptakes. In order to assess the potential sources of this variability, empirical orthogonal functions (EOF) of the three longest available atmospheric potential oxygen (APO) timeseries (Cape Grim, Barrow and American Samoa) were computed using the detrended and deseasonalized data averaged into months, and normalized. The dominant EOF appears statistically robust and explains 51% of the combined variance. It is characterized by loadings of the same sign and similar values at all three stations, suggesting that EOF1 may be related to fluctuations in the global mean APO, as opposed to geographic variability. Associations of EOF1 with various climatic fields and indices will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMGC72B0230H
- Keywords:
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- 0330 Geochemical cycles;
- 1094 Instruments and techniques;
- 4806 Carbon cycling