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Abstract:
Since the Last Glacial Maximum, boreal wetlands have accumulated substantial amounts of peat, estimated
at 180–621 Pg of carbon. Wetlands have significantly
affected the atmospheric greenhouse gas composition in the
past and will play a significant role in future changes of
atmospheric CO2 and CH4 concentrations. In order to investigate
those changes with an Earth system model, biogeochemical
processes in boreal wetlands need to be accounted
for. Thus, a model of peat accumulation and decay
was developed and included in the land surface model
JSBACH of the Max Planck Institute Earth System Model
(MPI-ESM). Here we present the evaluation of model results
from 6000 yr BP to the pre-industrial period. Over this
period of time, 240 Pg of peat carbon accumulated in the
model in the areas north of 40 N. Simulated peat accumulation
rates agree well with those reported for boreal wetlands.
The model simulates CH4 emissions of 49.3 TgCH4 yr−1
for 6000 yr BP and 51.5 TgCH4 yr−1 for pre-industrial times.
This is within the range of estimates in the literature, which
range from 32 to 112 TgCH4 yr−1 for boreal wetlands. The
modelled methane emission for the West Siberian Lowlands
and Hudson Bay Lowlands agree well with observations. The
rising trend of methane emissions over the last 6000 yr is in
agreement with measurements of Antarctic and Greenland ice cores.
