Constraining global air‐sea gas exchange for CO₂ with recent bomb ¹⁴C measurements

Abstract

[1] The 14 CO 2 released into the stratosphere during bomb testing in the early 1960s provides a global constraint on air-sea gas exchange of soluble atmospheric gases like CO 2 . Using the most complete database of dissolved inorganic radiocarbon, DI 14 C, available to date and a suite of ocean general circulation models in an inverse mode we recalculate the ocean inventory of bomb-produced DI 14 C in the global ocean and confirm that there is a 25% decrease from previous estimates using older DI 14 C data sets. Additionally, we find a 33% lower globally averaged gas transfer velocity for CO 2 compared to previous estimates (Wanninkhof, 1992) using the NCEP/NCAR Reanalysis 1 1954-2000 where the global mean winds are 6.9 m s À1 . Unlike some earlier ocean radiocarbon studies, the implied gas transfer velocity finally closes the gap between small-scale deliberate tracer studies and global-scale estimates. Additionally, the total inventory of bomb-produced radiocarbon in the ocean is now in agreement with global budgets based on radiocarbon measurements made in the stratosphere and troposphere. Using the implied relationship between wind speed and gas transfer velocity k s = 0.27hu 10 2 i(Sc/660) À0.5 and standard partial pressure difference climatology of CO 2 we obtain an net air-sea flux estimate of 1.3 ± 0.5 PgCyr À1 for 1995. After accounting for the carbon transferred from rivers to the deep ocean, our estimate of oceanic uptake (1.8 ± 0.5 PgCyr À1 ) compares well with estimates based on ocean inventories, ocean transport inversions using ocean concentration data, and model simulations.

First description of the Minnesota Earth System Model for Ocean biogeochemistry (MESMO 1.0)

“…We retained the Wanninkhof coefficient, because it remains the de facto standard in existing ocean carbon cycle models. However, a recent reanalysis of bomb 14 C inventory in the ocean, which constrains the global gas exchange coefficient, suggests that the Wanninkhof rate may be too high (Sweeney et al, 2007). As shown by Sarmiento et al (1992), gas exchange would have a more significant impact on "slow" equilibration gases such as 14 CO 2 than on "fast" gases such as CO 2 and CFCs, a result we confirmed with MESMO.…”

Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

“…To determine k, the revised empirical equation of Wanninkhof (1992) by Sweeney et al (2007) was used, that is,…”

“…d Air-sea gas transfer velocity was estimated using Liss and Merlivat (1986) equation. e Air-sea gas transfer velocity was estimated using Sweeney et al (2007) equation . East Siberian Arctic Shelf. In the northern East China Sea, CH 4 -rich effluents from the Yangtze River support the very high surface water [CH 4 ] (Zhang et al, 2008).…”

Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses

“…Very small accelerators have been developed (Synal et al 2000Skog 2007) for measuring 14 C. Voltages of 250 kV are used to destroy the molecular anions of 12 CH 2 and 13 CH, as then repeated collisions with gas molecules destroy them so that their abundance decreases exponentially with gas pressure (Lee et al 1984). The 14 N is eliminated by the use of negative ions.…”