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gfdl on-line bibliography > 2007 citations
Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements
| Sweeney, C., E. Gloor, A. R. Jacobson, R. M. Key, G. McKinley, J. L. Sarmiento, and R. Wanninkhof, 2007: Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements. Global Biogeochemical Cycles, 21, GB2015, doi:10.1029/2006GB002784. |
Abstract: The 14CO2 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
CO2. Using the most complete database of dissolved inorganic
radiocarbon, DI14C, available to date and a suite of ocean
general circulation models in an inverse mode we recalculate the ocean
inventory of bomb-produced DI14C in the global ocean and confirm
that there is a 25% decrease from previous estimates using older DI14C
data sets. Additionally, we find a 33% lower globally averaged gas transfer
velocity for CO2 compared to previous estimates (Wanninkhof,
1992) using the NCEP/NCAR Reanalysis 1 1954-2000 where the global mean winds
are 6.9 m s−1. 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 = 0.27
u 10 2
 (Sc/660)−0.5
and standard partial pressure difference climatology of CO2 we
obtain an net air-sea flux estimate of 1.3 ± 0.5 PgCyr−1 for
1995. After accounting for the carbon transferred from rivers to the deep
ocean, our estimate of oceanic uptake (1.8 ± 0.5 PgCyr−1)
compares well with estimates based on ocean inventories, ocean transport
inversions using ocean concentration data, and model simulations. |