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Northern peatlands in permafrost regions contain a large amount of organic carbon (C) in the soil. Climate warming and associated permafrost degradation are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is uncertain. We incorporated a permafrost model, Northern Ecosystem Soil Temperature (NEST), into abiogeochemical model, DeNitrification-DeComposition (DNDC), to model C dynamics in high-latitude peatland ecosystems. The enhanced model was applied to assess effects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen, Sweden. DNDC simulated soil freeze-thaw dynamics, net ecosystem exchange of CO2 (NEE), and CH4 fluxes across three typical land cover types, which represent a gradient in the process of ongoing permafrost thaw at Stordalen. Model results were compared with multiyear field measurements, and the validation indicates that DNDC was able to simulate observed differences in seasonal soil thaw, NEE, and CH4 fluxes across the three land cover types. Consistent with the results from field studies, the modeled C fluxes across the permafrost thaw gradient demonstrate that permafrost thaw and the associated changes in soil hydrology and vegetation not only increase net uptake of C from the atmosphere but also increase the annual to decadal radiative forcing impacts on climate due to increased CH4 emissions. This study indicates the potential of utilizing biogeochemical models, such as DNDC, to predict the soil thermal regime in permafrost areas and to investigate impacts of permafrost thaw on ecosystem C fluxes after incorporating a permafrost component into the model framework. [ABSTRACT FROM AUTHOR]

The article explores climate sensitivity in the Anthropocene to avoid dangerous anthropogenic interference with the climate system. It discusses climate sensitivity which depends on climate feedbacks' sign and strength. It defines climate feedback which is induced by a climate forcing. It also discusses related topics including Earth's energy balance, feedback sensitivity, and carbon cycle feedbacks.

The article discusses a study on the role and implications of peat carbon in thawing permafrost soils in North America in response to global warming. It mentions that Northern peatlands comprise a large terrestrial carbon pool which plays a significant role in the carbon cycle. It also notes that most of it is in permafrost and is biogeochemically inert that will change with increased temperatures of soils caused by climate warming in the 21st century.

The article presents a study on the Holocene Peat Model (HPM), a simulation model designed to determine peat accumulation tested at a temperate bog in Ontario. It states that the HPM was made and evaluated considering factors such as hydrology, peat properties and the nature of plant communities. It adds that peat decomposition and dynamic peat accumulation models were combined in HPM. Moreover, it asserts that the HPM is capable of demonstrating balances in peatland carbon and watecycles.

We applied an inverse model to simulate global carbon (C) cycle dynamics during the Holocene period using atmospheric carbon dioxide (CO2) concentrations reconstructed from Antarctic ice cores and prescribed C accumulation rates of Northern Peatlands (NP) as inputs. Previous studies indicated that different sources could contribute to the 20 parts per million by volume (ppmv) atmospheric CO2 increase over the past 8000 years. These sources of C include terrestrial release of 40-200 petagram C (PgC, 1 petagram=1015 gram), deep oceanic adjustment to a 500 PgC terrestrial biomass buildup early in this interglacial period, and anthropogenic land-use and land-cover changes of unknown magnitudes. Our study shows that the prescribed peatland C accumulation significantly modifies our previous understanding of Holocene C cycle dynamics. If the buildup of the NP is considered, the terrestrial pool becomes the C sink of about 160-280 PgC over the past 8000 years, and the only C source for the terrestrial and atmospheric C increases is presumably from the deep ocean due to calcium carbonate compensation. Future studies need to be conducted to constrain the basal times and growth rates of the NP C accumulation in the Holocene. These research endeavors are challenging because they need a dynamically-coupled peatland simulator to be constrained with the initiation time and reconstructed C reservoir of the NP. Our results also suggest that the huge reservoir of deep ocean C explains the major variability of the glacial-interglacial C cycle dynamics without considering the anthropogenic C perturbation. [ABSTRACT FROM AUTHOR]

The effect of Land Use Change and Forestry (LUCF) on terrestrial carbon fluxes can be regarded as a carbon credit or debit under the UNFCCC, but scientific uncertainty in the estimates for LUCF remains large. Here, we assess the LUCF estimates by examining a variety of models of different types with different land cover change maps in the 1990s. Annual carbon pools and their changes are separated into different components for separate geographical regions, while annual land cover change areas and carbon fluxes are disaggregated into different LUCF activities and the biospheric response due to CO2 fertilization and climate change. We developed a consolidated estimate of the terrestrial carbon fluxes that combines book-keeping models with process-based biogeochemical models and inventory estimates and yields an estimate of the global terrestrial carbon flux that is within the uncertainty range developed in the IPCC 4th Assessment Report. We examined the USA and Brazil as case studies in order to assess the cause of differences from the UNFCCC reported carbon fluxes. Major differences in the litter and soil organic matter components are found for the USA. Differences in Brazil result from assumptions about the LUC for agricultural purposes. The effects of CO2 fertilization and climate change also vary significantly in Brazil. Our consolidated estimate shows that the small sink in Latin America is within the uncertainty range from inverse models, but that the sink in the USA is significantly smaller than the inverse models estimates. Because there are different sources of errors at the country level, there is no easy reconciliation of different estimates of carbon fluxes at the global level. Clearly, further work is required to develop data sets for historical land cover change areas and models of biogeochemical changes for an accurate representation of carbon uptake or emissions due to LUC. [ABSTRACT FROM AUTHOR]

We developed the McGill Wetland Model (MWM) based on the general structure of the Peatland Carbon Simulator (PCARS) and the Canadian Terrestrial Ecosystem Model. Three major changes were made to PCARS: the light use efficiency model of photosynthesis was replaced with a biogeochemical description of photosynthesis; 2. the description of autotrophic respiration was changed to be consistent with the formulation of photosynthesis; and 3. the cohort, multilayer soil respiration model was changed to a simple one box peat decomposition model divided into an oxic and anoxic zones by an effective water table, and a one-year residence time litter pool. MWM was then evaluated by comparing its output to the estimates of net ecosystem production (NEP), gross primary production (GPP) and ecosystem respiration (ER) from years of continuous measurements at the Mer Bleue peatland, a raised ombrotrophic bog located in southern Ontario, Canada (index of agreement [dimensionless]: NEP=0.80, GPP=0.97, ER=0.97; systematic RMSE [g C m-2 d-1]: NEP=0.12, GPP=0.07, ER=0.14; unsystematic RMSE [g C m-2 d-1]: NEP=0.15, GPP=0.27, ER=0.23). Simulated moss NPP approximates what would be expected for a bog peatland, but shrub NPP appears to be underestimated. Sensitivity analysis revealed that the model output did not change greatly due to variations in water table because of offsetting responses in production and respiration, but that even modest temperature increases could lead to converting the bog from a sink to a source of CO2. General weaknesses and further developments of MWM are discussed. [ABSTRACT FROM AUTHOR]