B085-08
The resilience and vulnerability of the regional carbon sink in Alaska and Canada

Monday, 14 December 2020: 09:15
Virtual
Mary Farina1, Jennifer Watts2, Scott L Powell3, Kathleen E Savage2, Susan Natali2, John S Kimball4, Zhihua Liu5, Jinyang Du6, Yonghong Yi7 and Charles E Miller8, (1)Montana State University, Bozeman, MT, United States, (2)Woods Hole Research Center, Falmouth, MA, United States, (3)Montana State University Bozeman, Bozeman, MT, United States, (4)The University of Montana, Numerical Terradynamic Simulation Group, W.A. Franke College of Forestry & Conservation, Missoula, MT, United States, (5)University of Montana, Missoula, MT, United States, (6)University of Montana, Numerical Terradynamic Simulation Group, W.A. Franke College of Forestry & Conservation, Missoula, MT, United States, (7)University of California Los Angeles, Joint Institue for Regional Earth System Science and Engineering, Los Angeles, CA, United States, (8)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
Recorded Presentation
Abstract:
Rapid warming in Arctic-boreal ecosystems has the potential to alter near-future land-atmosphere exchanges of carbon dioxide (CO2) and methane (CH4). Warmer, longer growing seasons can lead to increasing trends in gross primary productivity (GPP). Warming soils and thawing permafrost can also expose large quantities of soil organic carbon to decomposition, potentially increasing ecosystem respiration (Reco) and offsetting gains in carbon uptake. Initial stages of permafrost thaw can lead to surface wetting and increases in CH4 emissions, while later thaw stages can lead to surface drying and decreases in CH4 emissions. Net CO2 and CH4 budgets are highly uncertain at regional and pan-Arctic scales, and remote sensing data-driven and bottom-up process models disagree in terms of the magnitude and sign of net carbon budgets (sink versus source). This study aims to improve understanding of spatio-temporal trends in net ecosystem exchange of CO2 (NEE) and CH4 emissions for ecosystems across Arctic-boreal North America. Daily carbon flux estimates from a process-based Terrestrial Carbon Flux (TCF) model (1-km spatial resolution) are used to compute annual and seasonal trends in GPP, Reco, NEE and CH4 emissions over years 2003-2019. Preliminary results for years 2003-2015 indicate that Arctic-boreal North America was a net CO2 sink, with a mean annual NEE of -217 ± 23 TgC year-1 (contributions from tundra regions, boreal forests, and boreal wetlands were 14%, 66%, and 20%, respectively). Mean annual CH4 emissions were 16 ± 0.5 TgC year-1 across Arctic-boreal North America. Accounting for the enhanced warming potential of CH4, the annual net carbon balance (NEE + CH4 in CO2 equivalence) was -57 ± 23 TgC year-1, with no significant trend over years 2003-2015. These findings improve understanding of carbon flux dynamics in Arctic-boreal North America. Ongoing work is investigating the impact of sub-grid-scale surface wetting and drying on CO2 and CH4 fluxes.
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