WETCHIMP-WSL: intercomparison of wetland methane emissions models over West Siberia
Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This risk is particularl...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-06-01
|
| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/12/3321/2015/bg-12-3321-2015.pdf |
| Summary: | Wetlands are the world's largest natural source of methane, a powerful
greenhouse gas. The strong sensitivity of methane emissions to environmental
factors such as soil temperature and moisture has led to concerns about
potential positive feedbacks to climate change. This risk is particularly
relevant at high latitudes, which have experienced pronounced warming and
where thawing permafrost could potentially liberate large amounts of labile
carbon over the next 100 years. However, global models disagree as to the
magnitude and spatial distribution of emissions, due to uncertainties in
wetland area and emissions per unit area and a scarcity of in situ
observations. Recent intensive field campaigns across the West Siberian
Lowland (WSL) make this an ideal region over which to assess the performance
of large-scale process-based wetland models in a high-latitude environment.
Here we present the results of a follow-up to the Wetland and Wetland
CH<sub>4</sub> Intercomparison of Models Project (WETCHIMP), focused on the West
Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over
this domain in terms of total CH<sub>4</sub> emissions, simulated wetland areas,
and CH<sub>4</sub> fluxes per unit wetland area and compared these results to an
intensive in situ CH<sub>4</sub> flux data set, several wetland maps, and two
satellite surface water products. We found that (a) despite the large scatter
of individual estimates, 12-year mean estimates of annual total emissions
over the WSL from forward models
(5.34 ± 0.54 Tg CH<sub>4</sub> yr<sup>−1</sup>), inversions
(6.06 ± 1.22 Tg CH<sub>4</sub> yr<sup>−1</sup>), and in situ observations
(3.91 ± 1.29 Tg CH<sub>4</sub> yr<sup>−1</sup>) largely agreed; (b) forward
models using surface water products alone to estimate wetland areas suffered
from severe biases in CH<sub>4</sub> emissions; (c) the interannual time series of
models that lacked either soil thermal physics appropriate to the high
latitudes or realistic emissions from unsaturated peatlands tended to be
dominated by a single environmental driver (inundation or air temperature),
unlike those of inversions and more sophisticated forward models; (d)
differences in biogeochemical schemes across models had relatively smaller
influence over performance; and (e) multiyear or multidecade observational
records are crucial for evaluating models' responses to long-term climate
change. |
|---|---|
| ISSN: | 1726-4170 1726-4189 |