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| Titel |
Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization |
| VerfasserIn |
A. Oschlies, W. Koeve, W. Rickels, K. Rehdanz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 12 ; Nr. 7, no. 12 (2010-12-17), S.4017-4035 |
| Datensatznummer |
250005106
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| Publikation (Nr.) |
 copernicus.org/bg-7-4017-2010.pdf |
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| Zusammenfassung |
| Recent suggestions to slow down the increase in atmospheric carbon dioxide
have included ocean fertilization by addition of the micronutrient iron to
Southern Ocean surface waters, where a number of natural and artificial iron
fertilization experiments have shown that low ambient iron concentrations
limit phytoplankton growth. Using a coupled carbon-climate model with the
marine biology's response to iron addition calibrated against data from
natural iron fertilization experiments, we examine biogeochemical side
effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF)
that need to be considered when attempting to account for possible
OIF-induced carbon offsets. In agreement with earlier studies our model
simulates an OIF-induced increase in local air-sea CO2 fluxes by about
73 GtC over a 100-year period, which amounts to about
48% of the
OIF-induced increase in organic carbon export
out of the fertilized area. Offsetting CO2 return
fluxes outside the region and after stopping the fertilization at 1, 7, 10,
50, and 100 years are quantified for a typical accounting period of 100
years. For continuous Southern Ocean iron fertilization, the
CO2 return flux
outside the fertilized area cancels about
20%
of the fertilization-induced
CO2 air-sea flux within the fertilized area on a 100-yr timescale. This
"leakage" effect has a
radiative impact
more than twice as large as the simulated
enhancement of marine N2O emissions. Other side effects not yet
discussed in terms of accounting schemes include a decrease in Southern Ocean
oxygen levels and a simultaneous shrinking of tropical suboxic areas, and
accelerated ocean acidification in the entire water column in the Southern
Ocean
at the expense of reduced globally-averaged surface-water
acidification. A prudent approach to account for the OIF-induced carbon
sequestration would account for global air-sea CO2 fluxes rather than
for local fluxes into the fertilized area only. However, according to our
model, this would underestimate the potential for offsetting CO2
emissions by about 20% on a 100 year accounting timescale. We suggest that a
fair accounting scheme applicable to both terrestrial and marine carbon
sequestration has to be based on emission offsets rather than on changes in
individual carbon pools. |
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