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| Titel |
Northern hemisphere peatland carbon cycle dynamics over the Holocene - modelled with the MPI-Earth System Model |
| VerfasserIn |
Robert J. Getzieh, Victor Brovkin, Thomas Kleinen, Egor Dyukarev, Eugenia A. Golovatskaya |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054511
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| Zusammenfassung |
| Peatlands of the high northern latitudes store about 450 petagrams of carbon and constitute a
significant natural source of methane (CH4) even though they cover only 3 % of the global
land surface. By storing carbon and removing carbon dioxide (CO2) from the atmosphere,
boreal peatlands have globally had a cooling effect on millennial timescales. Undisturbed
boreal peatlands are likely to continue functioning as a net carbon sink. On the other hand,
these carbon pools might be destabilised in the future since they are sensitive to climate
change. Given that processes of peat accumulation and decay are closely dependent on
hydrology and temperature, this balance may be altered significantly in the future.
As a result, northern peatlands could have a large impact on carbon cycle-climate
feedback mechanisms and therefore play an important role in global carbon cycle
dynamics.
However, global biogeochemistry models used for simulations of carbon cycle dynamics
in past and future climates usually neglect peatland processes. Our approach aims at the
evaluation of the feedback of boreal wetlands to climate through fluxes of CO2 and CH4 on
millennial time scales. For this purpose, we developed a generic model of peatland carbon
dynamics which is part of the Max Planck Institute Earth System Model (MPI-ESM) land
surface module JSBACH. Carbon accumulation is calculated as the net balance of
productivity and decomposition. The key factor is the water table depth which controls
decomposition rates. These are more than an order of magnitude lower in anoxic
conditions. Model output consists of carbon accumulation rates, peat height, net primary
production, fraction of carbon above respectively below water table, CH4 and CO2
emissions.
We have conducted a Holocene run (6000 years) of our model of peat dynamics, which
we forced with Holocene climate data from a model run with MPI-ESM (Fischer
et al.). The distribution of peatlands was determined using a dynamic model of
wetland extent (accompanying poster by Stacke et al.), which was coupled to the
JSBACH-peat model asynchronously. After these 6000 years, we get total peat storage
in the northern high and temperate latitudes (above 45° N) comparable to recent
estimates. Additionally, our model gives estimates of CH4 emissions during the
Holocene.
For additional validation on the local scale, we also forced the model with 10 years of
observed climate data from specific sites, e.g. the Bakchar Bog near Tomsk, Russia. This
enabled the comparison of seasonal dynamics of biomass, net primary production, net
ecosystem production, and peat accumulation rates with JSBACH-peat simulation output. |
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