Multi-year observations reveal a larger than expected autumn respiration signal across northeast Eurasia

• Published in: Biogeosciences
• Main Authors: Byrne, Brendan, Liu, Junjie, Yi, Yonghong, Chatterjee, Abhishek, Basu, Sourish, Cheng, Rui, Doughty, Russell, Chevallier, Frédéric, Bowman, Kevin W., Parazoo, Nicholas C., Crisp, David, Li, Xing, Xiao, Jingfeng, Sitch, Stephen, Guenet, Bertrand, Deng, Feng, Johnson, Matthew S., Philip, Sajeev, Mcguire, Patrick C., Miller, Charles E.
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), This research has been supported by the National Aeronautics and Space Administration (grant nos. 80NSSC21K1068, NNH17ZDA001N-OCO2, and NNH18ZDA001N-TE).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: CO2; Arctic; Boreal ecosystems; Soil carbon; [SDU]Sciences of the Universe [physics]; permafrost
• Online Access: https://insu.hal.science/insu-03824351; https://insu.hal.science/insu-03824351/document; https://insu.hal.science/insu-03824351/file/bg-19-4779-2022.pdf; https://doi.org/10.5194/bg-19-4779-2022

International audience Site-level observations have shown pervasive cold season CO 2 release across Arctic and boreal ecosystems, impacting annual carbon budgets. Still, the seasonality of CO 2 emissions are poorly quantified across much of the high latitudes due to the sparse coverage of site-level observations. Space-based observations provide the opportunity to fill some observational gaps for studying these high-latitude ecosystems, particularly across poorly sampled regions of Eurasia. Here, we show that data-driven net ecosystem exchange (NEE) from atmospheric CO 2 observations implies strong summer uptake followed by strong autumn release of CO 2 over the entire cold northeastern region of Eurasia during the 2015-2019 study period. Combining data-driven NEE with satellite-based estimates of gross primary production (GPP), we show that this seasonality implies less summer heterotrophic respiration (R h ) and greater autumn R h than would be expected given an exponential relationship between respiration and surface temperature. Furthermore, we show that this seasonality of NEE and R h over northeastern Eurasia is not captured by the TRENDY v8 ensemble of dynamic global vegetation models (DGVMs), which estimate that 47 %-57 % (interquartile range) of annual R h occurs during August-April, while the data-driven estimates suggest 59 %-76 % of annual R h occurs over this period. We explain this seasonal shift in R h by respiration from soils at depth during the zero-curtain period, when sub-surface soils remain unfrozen up to several months after the surface has frozen. Additional impacts of physical processes related to freeze-thaw dynamics may contribute to the seasonality of R h . This study confirms a significant and spatially extensive early cold season CO 2 efflux in the permafrost-rich region of northeast Eurasia and suggests that autumn R h from subsurface soils in the northern high latitudes is not well captured by current DGVMs.