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Dynamics of fossil fuel CO 2 neutralization by marine CaCO 3
Author(s) -
Archer David,
Kheshgi Haroon,
MaierReimer Ernst
Publication year - 1998
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 - 10.1029/98gb00744
Subject(s) - seafloor spreading , geology , dissolution , deep sea , carbon cycle , diagenesis , sedimentation , oceanography , atmosphere (unit) , weathering , alkalinity , carbonate , mineralogy , geochemistry , chemistry , paleontology , sediment , ecology , meteorology , ecosystem , physics , organic chemistry , biology
A detailed model of the ocean circulation and carbon cycle was coupled to a mechanistic model of CaCO 3 diagenesis in deep sea sediments to simulate the millennium‐scale response of the oceans to future fossil fuel CO 2 emissions to the atmosphere and deep sea. Simulations of deep sea injection of CO 2 show that CaCO 3 dissolution is sensitive to passage of high‐CO 2 waters through the Atlantic Ocean, but CaCO 3 dissolution has a negligible impact on atmospheric p CO 2 or the atmospheric stabilization CO 2 emission in the coming centuries. The ultimate fate of the fossil fuel CO 2 will be to react with CaCO 3 on the seafloor and on land. An initial CaCO 3 dissolution spike reverses the net sedimentation rate in the ocean until it is attenuated by an enhanced vertical gradient of alkalinity after about 1000 years. The magnitude of the initial spike is sensitive to assumptions about the kinetics for CaCO 3 dissolution, but subsequent behavior appears to be less model dependent. Neutralization by seafloor CaCO 3 occurs on a timescale of 5–6 kyr, and is limited to at most 60–70% of the fossil fuel release, even if the fossil fuel release is smaller than the seafloor erodible inventory of CaCO 3 . Additional neutralization by terrestrial CaCO 3 restores a balance between CaCO 3 weathering and seafloor accumulation on a timescale of 8.5 kyr, while the deficit of seafloor CaCO 3 (the lysocline) is replenished with an e ‐folding timescale of approximately 18 kyr. The final equilibrium with CaCO 3 leaves 7–8% of the fossil fuel CO 2 remaining in the atmosphere, to be neutralized by the silicate rock cycle on a time frame of hundreds of thousands of years.