Large carbon cycle sensitivities to climate across a permafrost thaw gradient in subarctic Sweden
<p>Permafrost peatlands store large amounts of carbon potentially vulnerable to decomposition. However, the fate of that carbon in a changing climate remains uncertain in models due to complex interactions among hydrological, biogeochemical, microbial, and plant processes. In this study, we es...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/13/647/2019/tc-13-647-2019.pdf |
| Summary: | <p>Permafrost peatlands store large amounts of carbon potentially vulnerable to
decomposition. However, the fate of that carbon in a changing climate remains
uncertain in models due to complex interactions among hydrological,
biogeochemical, microbial, and plant processes. In this study, we estimated
effects of climate forcing biases present in global climate reanalysis
products on carbon cycle predictions at a thawing permafrost peatland in
subarctic Sweden. The analysis was conducted with a comprehensive
biogeochemical model (<i>ecosys</i>) across a permafrost thaw gradient
encompassing intact permafrost palsa with an ice core and a shallow active
layer, partly thawed bog with a deeper active layer and a variable water
table, and fen with a water table close to the surface, each with distinct
vegetation and microbiota. Using in situ observations to correct
local cold and wet biases found in the Global Soil Wetness Project Phase 3
(GSWP3) climate reanalysis forcing, we demonstrate good model performance by
comparing predicted and observed carbon dioxide (<span class="inline-formula">CO<sub>2</sub></span>) and methane
(<span class="inline-formula">CH<sub>4</sub></span>) exchanges, thaw depth, and water table depth. The simulations
driven by the bias-corrected climate suggest that the three peatland types
currently accumulate carbon from the atmosphere, although the bog and fen
sites can have annual positive radiative forcing impacts due to their higher
<span class="inline-formula">CH<sub>4</sub></span> emissions. Our simulations indicate that projected precipitation
increases could accelerate <span class="inline-formula">CH<sub>4</sub></span> emissions from the palsa area, even
without further degradation of palsa permafrost. The GSWP3 cold and wet
biases for this site significantly alter simulation results and lead to
erroneous active layer depth (ALD) and carbon budget estimates. Biases in
simulated <span class="inline-formula">CO<sub>2</sub></span> and <span class="inline-formula">CH<sub>4</sub></span> exchanges from biased climate forcing
are as large as those among the thaw stages themselves at a landscape scale
across the examined permafrost thaw gradient. Future studies should thus not
only focus on changes in carbon budget associated with morphological changes
in thawing permafrost, but also recognize the effects of climate forcing
uncertainty on carbon cycling.</p> |
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| ISSN: | 1994-0416 1994-0424 |