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Abstract Northern peatlands have been a carbon sink since their initiation. This has been simulated by existing process‐based models. However, most of these models are limited by lacking sufficient processes of the N cycle in peatlands. Here, we use a peatland biogeochemistry model incorporated with N‐related processes of fixation, deposition, gas emission, loss through water flow, net mineralization, plant uptake and litterfall to project the role of the peatlands in future radiative forcing (RF). Simulations from 15‐ka BP to 2100 are conducted driven by CMIP5 climate forcing data of IPSL‐CM5A‐LR and bcc‐csm1‐1, including warming scenarios of RCP 2.6, RCP 4.5 and RCP 8.5. During the Holocene, northern peatlands have an increasing cooling effect with RF up to −0.57 W m−2. By 1990, these peatlands accumulate 408 Pg C and 7.8 Pg N. Under warming, increasing mineral N content enhances plant net primary productivity; the cooling effect persists. However, RF increases by 0.1–0.5 W m−2during the 21st century, mainly due to the stimulated CH4emissions. Northern peatlands could switch from a C sink to a source when the annual temperature exceeds −2.2 to −0.5°C. This study highlights that the improved N cycle causes higher CO2‐C sink capacity in northern peatlands. However, it also causes a significant increase in CH4emissions, which weakens the cooling effect of northern peatlands in future climate.
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Peatlands and their carbon dynamics in northern high latitudes from 1990 to 2300: a process-based biogeochemistry model analysis
Abstract. Northern peatlands have been a large C sink during the Holocene,but whether they will keep being a C sink under future climate change isuncertain. This study simulates the responses of northern peatlands tofuture climate until 2300 with a Peatland version Terrestrial EcosystemModel (PTEM). The simulations are driven with two sets of CMIP5 climate data(IPSL-CM5A-LR and bcc-csm1-1) under three warming scenarios (RCPs 2.6, 4.5 and8.5). Peatland area expansion, shrinkage, and C accumulation anddecomposition are modeled. In the 21st century, northern peatlands areprojected to be a C source of 1.2–13.3 Pg C under all climate scenariosexcept for RCP 2.6 of bcc-csm1-1 (a sink of 0.8 Pg C). During 2100–2300,northern peatlands under all scenarios are a C source under IPSL-CM5A-LRscenarios, being larger sources than bcc-csm1-1 scenarios (5.9–118.3 vs.0.7–87.6 Pg C). C sources are attributed to (1) the peatland water table depth(WTD) becoming deeper and permafrost thaw increasing decomposition rate; (2) net primary production (NPP) not increasing much as climate warms becausepeat drying suppresses net N mineralization; and (3) as WTD deepens,peatlands switching from moss–herbaceous dominated to moss–woody dominated,while woody plants require more N for productivity. Under IPSL-CM5A-LRscenarios, northern peatlands remain as a C sink until the pan-Arctic annualtemperature reaches −2.6 to −2.89 ∘C, while this threshold is −2.09to −2.35 ∘C under bcc-csm1-1 scenarios. This study predicts anorthern peatland sink-to-source shift in around 2050, earlier than previousestimates of after 2100, and emphasizes the vulnerability of northernpeatlands to climate change.
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- PAR ID:
- 10420536
- Date Published:
- Journal Name:
- Biogeosciences
- Volume:
- 20
- Issue:
- 1
- ISSN:
- 1726-4189
- Page Range / eLocation ID:
- 251 to 270
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/bg-20-251-2023
