Carbon cycle uncertainty in the Alaskan Arctic

[摘要] Climate change is leading to a disproportionately large warming in the highnorthern latitudes, but the magnitude and sign of the future carbon balanceof the Arctic are highly uncertain. Using 40 terrestrial biosphere models forthe Alaskan Arctic from four recent model intercomparison projects – NACP(North American Carbon Program) site and regional syntheses, TRENDY (Trendsin net land atmosphere carbon exchanges), and WETCHIMP (Wetland and WetlandCH₄ Inter-comparison of Models Project) – we provide a baseline ofterrestrial carbon cycle uncertainty, defined as the multi-model standarddeviation (σ) for each quantity that follows. Mean annual absoluteuncertainty was largest for soil carbon (14.0 ± 9.2 kg C m⁻²),then gross primary production (GPP)(0.22 ± 0.50 kg C m⁻² yr⁻¹), ecosystem respiration (Re)(0.23 ± 0.38 kg C m⁻² yr⁻¹), net primary production (NPP)(0.14 ± 0.33 kg C m⁻² yr⁻¹), autotrophic respiration (Ra)(0.09 ± 0.20 kg C m⁻² yr⁻¹), heterotrophic respiration(Rh) (0.14 ± 0.20 kg C m⁻² yr⁻¹), net ecosystem exchange(NEE) (−0.01 ± 0.19 kg C m⁻² yr⁻¹), and CH₄ flux(2.52 ± 4.02 g CH₄ m⁻² yr⁻¹). There were noconsistent spatial patterns in the larger Alaskan Arctic and boreal regionalcarbon stocks and fluxes, with some models showing NEE for Alaska as a strongcarbon sink, others as a strong carbon source, while still others as carbonneutral. Finally, AmeriFlux data are used at two sites in the Alaskan Arcticto evaluate the regional patterns; observed seasonal NEE was captured withinmulti-model uncertainty. This assessment of carbon cycle uncertainties may beused as a baseline for the improvement of experimental and modelingactivities, as well as a reference for future trajectories in carbon cyclingwith climate change in the Alaskan Arctic and larger boreal region.

[学科分类] 地球化学与岩石