Possible effects of iron fertilization in the Southern Ocean on atmospheric CO2 concentration

Fortunat Joos, Ulrich Siegenthaler, Jorge Louis Sarmiento

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Recently, it was proposed (Baum, 1990 and Martin et al, 1990a, 1990b) that the southern ocean should be fertilized with iron to stimulate biological productivity, thus enhancing the flux of organic carbon from surface to depth, thereby lowering the concentration of inorganic carbon in surface water and in turn the atmospheric CO2 concentration. We explore the possible impact of a hypothetical iron fertilization on atmospheric CO2 levels during the next century using a high‐latitude exchange/interior diffusion advection model. Assuming as an upper‐limit scenario that it is possible to stimulate the uptake of the abundant nutrients in the southern ocean, the maximum atmospheric CO2 depletion is 58 ppm after 50 years and 107 ppm after 100 years. This scenario requires completely effective Fe fertilization to be carried out over 16% of the world ocean area. Sensitivity studies and comparison with other models suggest that the errors in these limits due to uncertainties in the transport parameters, which are determined by calibrating the model with radiocarbon and validated with CFC‐11 measurements, range from −29% to +17%. If iron‐stimulated biological productivity is halted during the six winter months, the additional oceanic CO2 uptake is reduced by 18%. Possible changes in surface water alkalinity alter the result of iron fertilization by less than +9% to −28%. Burial of the iron‐induced particle flux as opposed to remineralization in the deep ocean has virtually no influence on the atmospheric response for the considered time scale of 100 years. If iron fertilization were terminated, CO2 would escape from the ocean and soon cancel the effect of the fertilization. The factors which determine the atmospheric CO2 reduction most strongly are the area of fertilization, the extent to which biology utilizes the abundant nutrients, and the magnitude of future CO2 emissions. The possible effect of fertilizing the ocean with iron is small compared to the expected atmospheric CO2 increase over the next century, unless the increase is kept small by means of stringent measures to control CO2 emissions.

Original languageEnglish (US)
Pages (from-to)135-150
Number of pages16
JournalGlobal Biogeochemical Cycles
Volume5
Issue number2
DOIs
StatePublished - Jan 1 1991

Fingerprint

Iron
iron
ocean
Surface waters
Nutrients
Productivity
Fluxes
Emission control
surface water
Advection
productivity
Alkalinity
Organic carbon
remineralization
nutrient
inorganic carbon
Carbon
alkalinity
effect
advection

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Global and Planetary Change
  • Environmental Chemistry
  • Atmospheric Science

Cite this

Joos, Fortunat ; Siegenthaler, Ulrich ; Sarmiento, Jorge Louis. / Possible effects of iron fertilization in the Southern Ocean on atmospheric CO2 concentration. In: Global Biogeochemical Cycles. 1991 ; Vol. 5, No. 2. pp. 135-150.
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title = "Possible effects of iron fertilization in the Southern Ocean on atmospheric CO2 concentration",
abstract = "Recently, it was proposed (Baum, 1990 and Martin et al, 1990a, 1990b) that the southern ocean should be fertilized with iron to stimulate biological productivity, thus enhancing the flux of organic carbon from surface to depth, thereby lowering the concentration of inorganic carbon in surface water and in turn the atmospheric CO2 concentration. We explore the possible impact of a hypothetical iron fertilization on atmospheric CO2 levels during the next century using a high‐latitude exchange/interior diffusion advection model. Assuming as an upper‐limit scenario that it is possible to stimulate the uptake of the abundant nutrients in the southern ocean, the maximum atmospheric CO2 depletion is 58 ppm after 50 years and 107 ppm after 100 years. This scenario requires completely effective Fe fertilization to be carried out over 16{\%} of the world ocean area. Sensitivity studies and comparison with other models suggest that the errors in these limits due to uncertainties in the transport parameters, which are determined by calibrating the model with radiocarbon and validated with CFC‐11 measurements, range from −29{\%} to +17{\%}. If iron‐stimulated biological productivity is halted during the six winter months, the additional oceanic CO2 uptake is reduced by 18{\%}. Possible changes in surface water alkalinity alter the result of iron fertilization by less than +9{\%} to −28{\%}. Burial of the iron‐induced particle flux as opposed to remineralization in the deep ocean has virtually no influence on the atmospheric response for the considered time scale of 100 years. If iron fertilization were terminated, CO2 would escape from the ocean and soon cancel the effect of the fertilization. The factors which determine the atmospheric CO2 reduction most strongly are the area of fertilization, the extent to which biology utilizes the abundant nutrients, and the magnitude of future CO2 emissions. The possible effect of fertilizing the ocean with iron is small compared to the expected atmospheric CO2 increase over the next century, unless the increase is kept small by means of stringent measures to control CO2 emissions.",
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Possible effects of iron fertilization in the Southern Ocean on atmospheric CO2 concentration. / Joos, Fortunat; Siegenthaler, Ulrich; Sarmiento, Jorge Louis.

In: Global Biogeochemical Cycles, Vol. 5, No. 2, 01.01.1991, p. 135-150.

Research output: Contribution to journalArticle

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