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| Titel |
Rates of consumption of atmospheric CO2 through the weathering of loess during the next 100 yr of climate change |
| VerfasserIn |
Y. Godderis, S. L. Brantley, L. M. François, J. Schott, D. Pollard, M. Déqué, M. Dury |
| 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 ; 10, no. 1 ; Nr. 10, no. 1 (2013-01-09), S.135-148 |
| Datensatznummer |
250017463
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| Publikation (Nr.) |
 copernicus.org/bg-10-135-2013.pdf |
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| Zusammenfassung |
Quantifying how C fluxes will change in the future is a complex task for
models because of the coupling between climate, hydrology, and
biogeochemical reactions. Here we investigate how pedogenesis of the Peoria
loess, which has been weathering for the last 13 kyr, will respond over the
next 100 yr of climate change. Using a cascade of numerical models for
climate (ARPEGE), vegetation (CARAIB) and weathering (WITCH), we explore the
effect of an increase in CO2 of 315 ppmv (1950) to 700 ppmv (2100
projection). The increasing CO2 results in an increase in temperature
along the entire transect. In contrast, drainage increases slightly for a
focus pedon in the south but decreases strongly in the north. These two
variables largely determine the behavior of weathering. In addition,
although CO2 production rate increases in the soils in response to
global warming, the rate of diffusion back to the atmosphere also increases,
maintaining a roughly constant or even decreasing CO2 concentration in
the soil gas phase. Our simulations predict that temperature increasing in
the next 100 yr causes the weathering rates of the silicates to increase
into the future. In contrast, the weathering rate of dolomite – which
consumes most of the CO2 – decreases in both end members (south and
north) of the transect due to its retrograde solubility. We thus infer
slower rates of advance of the dolomite reaction front into the subsurface,
and faster rates of advance of the silicate reaction front. However,
additional simulations for 9 pedons located along the north–south transect
show that the dolomite weathering advance rate will increase in the central
part of the Mississippi Valley, owing to a maximum in the response of
vertical drainage to the ongoing climate change.
The carbonate reaction front can be likened to a terrestrial lysocline
because it represents a depth interval over which carbonate dissolution
rates increase drastically. However, in contrast to the lower pH and
shallower lysocline expected in the oceans with increasing atmospheric
CO2, we predict a deeper lysocline in future soils. Furthermore, in the
central Mississippi Valley, soil lysocline deepening accelerates but in the
south and north the deepening rate slows. This result illustrates the
complex behavior of carbonate weathering facing short term global climate
change. Predicting the global response of terrestrial weathering to
increased atmospheric CO2 and temperature in the future will mostly
depend upon our ability to make precise assessments of which areas of the
globe increase or decrease in precipitation and soil drainage. |
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