Takahashi¹, Taro, Stewart C. Sutherland¹, Colm Sweeney¹, Alain Poisson², Nicolas Metzl², Bronte Tilbrook³, Rik Wanninkhof⁴, Richard A. Feely⁵, Christopher Sabine⁵, Jon Olafsson⁶, Nicolas Bates⁷ and Yukihiro Nojiri⁸

¹Lamont-Doherty Earth Observatory, Palisades, NY 10964, U.S.A. E-mail: taka@ldeo.columbia.edu, ²Laboratoir de Biogeochimie et Chimie Marines, Universite Pierre et Marie Curie, Paris, France, ³Antarctic CRC and CSIRO Marine Research, Hobart, Tasmania 7001, Australia, ⁴AOML, National Oceanographic and Atmospheric Administration, Miami, FL 33149, U.S.A., ⁵PMEL, National Oceanographic and Atmospheric Administration, Seattle, WA 98115, U.S.A., ⁶University of Iceland and Marine Research Institute, 121, Reykjavik, Iceland, ⁷Bermuda Biological Station for Research, GE 01, Bermuda and ⁸National Institute for Environmental Studies, Tsukuba, Japan

Net sea-air CO₂ flux over the global oceans: a climatological mean based on sea-air pCO₂ difference

Based on about 1.3 million measurements of surface water pCO₂ obtained since the 1960’s, the climatological, monthly distribution of pCO₂ in the global surface waters for non-El Niño conditions has been calculated with a spatial resolution of 4^o x 5^o for a reference year 1995. The observations made in the equatorial Pacific zone between 10^oN and 10^oS during El Niño events have been excluded from this analysis. The net sea-air CO₂ flux has been estimated using the wind speed square formulation of Wanninkhof (1992) for the CO₂ gas transfer coefficient and the mean monthly wind speed obtained from the 41-year NCEP record. The results summarized below represent an up-date for those published in Takahashi et al. (DSR, 2002), that yielded a global ocean CO₂ uptake of 2.22 Pg-C/yr for 1995 on the basis of about 0.94 million measurements. The new estimate is 2.12 Pg-C/yr for the same reference year 1995. In terms of the uptake flux per unit ocean area, the North Atlantic and the Southern Ocean are most significant CO₂ sinks due mainly to cold temperatures and intense summer photosynthesis, while the Pacific as a whole takes up least because of the high sea-to-air flux over the equatorial areas.

Lat. Band Pacific Atlantic Indian Southern Global

N. of 50°N (95) 0.00 -0.40 - - -0.40

14°N-50°N (95) -0.66 -0.34 +0.07 - -0.94

14°S-14°N (95) +0.79 +0.15 +0.18 - +1.12

14°S-50°S (95) -0.50 -0.31 -0.67 - -1.48

S. of 50°S (95) - - - -0.42 -0.42

--------------------- ------------ ---------- ------------ ----------- ----------

Total (95) -0.36 -0.91 -0.42 -0.42 -2.12

% of Uptake 17 43 20 20 100

% of Ocean Areas 47 23 17 13 100