TY - JOUR
T1 - The control of atmospheric pCO 2 by ocean ventilation change
T2 - The effect of the oceanic storage of biogenic carbon
AU - Kwon, Eun Young
AU - Sarmiento, Jorge Louis
AU - Toggweiler, J. R.
AU - Devries, Tim
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2011
Y1 - 2011
N2 - A simple analytical framework is developed relating the atmospheric partial pressure of CO 2 to the globally-averaged concentrations of respired carbon (C soft) and dissolved carbonate (C carb) 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 ΔpCO 2/pCO 2 =-0.0053Δ C soft + 0.0034Δ C carb suggests that atmospheric pCO 2 would decrease by 5.3% and increase by 3.4% when C soft and C carb increase by 10 mol kg -1, respectively. Using this analytical framework along with a 3-D global ocean biogeochemistry model, we show that the response of atmospheric pCO 2 to changes in ocean circulation is rather modest because ∼30% of the change in atmospheric pCO 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 pCO 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 pCO 2 is only 14-34 ppm. The large uncertainty ranges in atmospheric pCO 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 pCO 2 of 80-100 ppm.
AB - A simple analytical framework is developed relating the atmospheric partial pressure of CO 2 to the globally-averaged concentrations of respired carbon (C soft) and dissolved carbonate (C carb) 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 ΔpCO 2/pCO 2 =-0.0053Δ C soft + 0.0034Δ C carb suggests that atmospheric pCO 2 would decrease by 5.3% and increase by 3.4% when C soft and C carb increase by 10 mol kg -1, respectively. Using this analytical framework along with a 3-D global ocean biogeochemistry model, we show that the response of atmospheric pCO 2 to changes in ocean circulation is rather modest because ∼30% of the change in atmospheric pCO 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 pCO 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 pCO 2 is only 14-34 ppm. The large uncertainty ranges in atmospheric pCO 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 pCO 2 of 80-100 ppm.
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U2 - 10.1029/2011GB004059
DO - 10.1029/2011GB004059
M3 - Article
AN - SCOPUS:80053551480
SN - 0886-6236
VL - 25
JO - Global Biogeochemical Cycles
JF - Global Biogeochemical Cycles
IS - 3
M1 - GB3026
ER -