Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks.

Large stocks of soil organic carbon (SOC) have accumulated in the Northern Hemisphere permafrost region, but their current amounts and future fate remain uncertain. By analyzing dataset combining >2700 soil profiles with environmental variables in a geospatial framework, we generated spatially explicit estimates of permafrost-region SOC stocks, quantified spatial heterogeneity, and identified key environmental predictors. We estimated that Pg C are stored in the top 3 m of permafrost region soils.

Large loss of CO in winter observed across the northern permafrost region.

Recent warming in the Arctic, which has been amplified during the winter, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO). However, the amount of CO released in winter is highly uncertain and has not been well represented by ecosystem models or by empirically-based estimates. Here we synthesize regional observations of CO flux from arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain.

Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw.

Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO ) and methane (CH ) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland.

Tundra landscape heterogeneity, not interannual variability, controls the decadal regional carbon balance in the Western Russian Arctic.

Across the Arctic, the net ecosystem carbon (C) balance of tundra ecosystems is highly uncertain due to substantial temporal variability of C fluxes and to landscape heterogeneity. We modeled both carbon dioxide (CO ) and methane (CH ) fluxes for the dominant land cover types in a ~100-km sub-Arctic tundra region in northeast European Russia for the period of 2006-2015 using process-based biogeochemical models. Modeled net annual CO fluxes ranged from -300 g C m  year [net uptake] in a willow fen to 3 g C m  year [net source] in dry lichen tundra.

Nongrowing season methane emissions-a significant component of annual emissions across northern ecosystems.

Wetlands are the single largest natural source of atmospheric methane (CH ), a greenhouse gas, and occur extensively in the northern hemisphere. Large discrepancies remain between "bottom-up" and "top-down" estimates of northern CH emissions. To explore whether these discrepancies are due to poor representation of nongrowing season CH emissions, we synthesized nongrowing season and annual CH flux measurements from temperate, boreal, and tundra wetlands and uplands.

A pan-Arctic synthesis of CH and CO production from anoxic soil incubations.

Permafrost thaw can alter the soil environment through changes in soil moisture, frequently resulting in soil saturation, a shift to anaerobic decomposition, and changes in the plant community. These changes, along with thawing of previously frozen organic material, can alter the form and magnitude of greenhouse gas production from permafrost ecosystems. We synthesized existing methane (CH ) and carbon dioxide (CO ) production measurements from anaerobic incubations of boreal and tundra soils from the geographic permafrost region to evaluate large-scale controls of anaerobic CO and CH production and compare the relative importance of landscape-level factors (e.