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| Titel |
Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity |
| VerfasserIn |
T. Schneider von Deimling, G. Grosse, J. Strauss, L. Schirrmeister, A. Morgenstern, S. Schaphoff, M. Meinshausen, J. Boike |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-05), S.3469-3488 |
| Datensatznummer |
250117972
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| Publikation (Nr.) |
 copernicus.org/bg-12-3469-2015.pdf |
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| Zusammenfassung |
High-latitude soils store vast amounts of perennially frozen and therefore
inert organic matter. With rising global temperatures and consequent
permafrost degradation, a part of this carbon stock will become available
for microbial decay and eventual release to the atmosphere. We have
developed a simplified, two-dimensional multi-pool model to estimate the
strength and timing of future carbon dioxide (CO2) and methane
(CH4) fluxes from newly thawed permafrost carbon (i.e. carbon thawed
when temperatures rise above pre-industrial levels). We have especially
simulated carbon release from deep deposits in Yedoma regions by describing
abrupt thaw under newly formed thermokarst lakes. The computational
efficiency of our model allowed us to run large, multi-centennial ensembles
under various scenarios of future warming to express uncertainty inherent to
simulations of the permafrost carbon feedback.
Under moderate warming of the representative concentration pathway (RCP) 2.6
scenario, cumulated CO2 fluxes from newly thawed permafrost carbon
amount to 20 to 58 petagrams of carbon (Pg-C) (68% range) by the year
2100 and reach 40 to 98 Pg-C in 2300. The much larger permafrost degradation
under strong warming (RCP8.5) results in cumulated CO2 release of 42 to
141 Pg-C and 157 to 313 Pg-C (68% ranges) in the years 2100 and 2300,
respectively. Our estimates only consider fluxes from newly thawed
permafrost, not from soils already part of the seasonally thawed active
layer under pre-industrial climate. Our simulated CH4 fluxes
contribute a few percent to total permafrost carbon release yet they can
cause up to 40% of total permafrost-affected radiative forcing in the
21st century (upper 68% range). We infer largest CH4 emission
rates of about 50 Tg-CH4 per year around the middle of the 21st
century when simulated thermokarst lake extent is at its maximum and when
abrupt thaw under thermokarst lakes is taken into account. CH4 release
from newly thawed carbon in wetland-affected deposits is only discernible in
the 22nd and 23rd century because of the absence of abrupt thaw
processes. We further show that release from organic matter stored in deep
deposits of Yedoma regions crucially affects our simulated circumpolar
CH4 fluxes. The additional warming through the release from newly
thawed permafrost carbon proved only slightly dependent on the pathway of
anthropogenic emission and amounts to about 0.03–0.14 °C (68%
ranges) by end of the century. The warming increased further in the
22nd and 23rd century and was most pronounced under the RCP6.0
scenario, adding 0.16 to 0.39 °C (68% range) to simulated
global mean surface air temperatures in the year 2300. |
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