Calculating surface ocean pCO 2 from biogeochemical Argo floats equipped with pH: An uncertainty analysis

Type Article
Date 2017-03
Language English
Author(s) Williams N. L.1, Juranek L. W.1, Feely R. A.2, Johnson K. S.3, Sarmiento J. L.4, Talley L. D.5, Dickson A. G.5, Gray A. R.4, Wanninkhof R.6, Russell J. L.7, Riser S. C.8, Takeshita Y.3
Affiliation(s) 1 : Oregon State Univ, Coll Earth Ocean & Atmospher Sci, Corvallis, OR 97331 USA.
2 : NOAA, Pacific Marine Environm Lab, 7600 Sand Point Way Ne, Seattle, WA 98115 USA.
3 : Monterey Bay Aquarium Res Inst, Moss Landing, CA USA.
4 : Princeton Univ, Program Atmospher & Ocean Sci, Princeton, NJ 08544 USA.
5 : Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA.
6 : NOAA, Atlantic Oceanog & Meteorol Lab, Miami, FL 33149 USA.
7 : Univ Arizona, Dept Geosci, Tucson, AZ 85721 USA.
8 : Univ Washington, Sch Oceanog, Seattle, WA 98195 USA.
Source Global Biogeochemical Cycles (0886-6236) (Amer Geophysical Union), 2017-03 , Vol. 31 , N. 3 , P. 591-604
DOI 10.1002/2016GB005541
WOS© Times Cited 91
Abstract

More than 74 biogeochemical profiling floats that measure water column pH, oxygen, nitrate, fluorescence, and backscattering at 10 day intervals have been deployed throughout the Southern Ocean. Calculating the surface ocean partial pressure of carbon dioxide (pCO2sw) from float pH has uncertainty contributions from the pH sensor, the alkalinity estimate, and carbonate system equilibrium constants, resulting in a relative standard uncertainty in pCO2sw of 2.7% (or 11 µatm at pCO2sw of 400 µatm). The calculated pCO2sw from several floats spanning a range of oceanographic regimes are compared to existing climatologies. In some locations, such as the subantarctic zone, the float data closely match the climatologies, but in the polar Antarctic zone significantly higher pCO2sw are calculated in the wintertime implying a greater air-sea CO2 efflux estimate. Our results based on four representative floats suggest that despite their uncertainty relative to direct measurements, the float data can be used to improve estimates for air-sea carbon flux, as well as to increase knowledge of spatial, seasonal, and interannual variability in this flux.

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Williams N. L., Juranek L. W., Feely R. A., Johnson K. S., Sarmiento J. L., Talley L. D., Dickson A. G., Gray A. R., Wanninkhof R., Russell J. L., Riser S. C., Takeshita Y. (2017). Calculating surface ocean pCO 2 from biogeochemical Argo floats equipped with pH: An uncertainty analysis. Global Biogeochemical Cycles, 31(3), 591-604. Publisher's official version : https://doi.org/10.1002/2016GB005541 , Open Access version : https://archimer.ifremer.fr/doc/00383/49462/