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The control of atmospheric p CO 2 by ocean ventilation change: The effect of the oceanic storage of biogenic carbon
Author(s) -
Kwon Eun Young,
Sarmiento Jorge L.,
Toggweiler J. R.,
DeVries Tim
Publication year - 2011
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2011gb004059
Subject(s) - seawater , environmental science , biogeochemistry , oceanography , atmosphere (unit) , deep sea , carbonate , atmospheric carbon cycle , geochemical cycle , carbon cycle , dissolved organic carbon , carbon fibers , carbon dioxide , carbon sequestration , geology , environmental chemistry , chemistry , ecosystem , ecology , meteorology , geography , materials science , composite number , composite material , organic chemistry , biology
A simple analytical framework is developed relating the atmospheric partial pressure of CO 2 to the globally‐averaged concentrations of respired carbon () and dissolved carbonate () in the ocean. Assuming that the inventory of carbon is conserved in the ocean‐atmosphere system (i.e. no seawater‐sediment interactions), the resulting formula of = −0.0053Δ + 0.0034Δ suggests that atmospheric p CO 2 would decrease by 5.3% and increase by 3.4% when and increase by 10 μ mol kg −1 , respectively. Using this analytical framework along with a 3‐D global ocean biogeochemistry model, we show that the response of atmospheric p CO 2 to changes in ocean circulation is rather modest because ∼30% of the change in atmospheric p CO 2 caused by the accumulation of respired carbon is countered by a concomitant accumulation of dissolved carbonate in deep waters. Among the suite of circulation models examined here, the largest reduction in atmospheric p CO 2 of 44–88 ppm occurs in a model where reduced overturning rates of both southern and northern sourced deep waters result in a four‐fold increase in the Southern Ocean deep water ventilation age. On the other hand, when the ventilation rate of the southern‐sourced water decreases, but the overturning rate of North Atlantic Deep Water increases, the resulting decrease in atmospheric p CO 2 is only 14–34 ppm. The large uncertainty ranges in atmospheric p CO 2 arise from uncertainty in how surface productivity responds to circulation change. Although the uncertainty is large, this study suggests that a synchronously reduced rate for the deep water formation in both hemispheres could lead to the large glacial reduction in atmospheric p CO 2 of 80–100 ppm.