Recent Warming Has Resulted in Smaller Gains in Net Carbon Uptake in Northern High Latitudes

• Published in: Journal of Climate
• Main Authors: Zhu, Peng, Zhuang, Qianlai, Welp, Lisa, Ciais, Philippe, Heimann, Martin, Peng, Bin, Li, Wenyu, Bernacchi, Carl, Roedenbeck, Christian, Keenan, Trevor
• Other Authors: Purdue University West Lafayette, ICOS-ATC (ICOS-ATC), 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)-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), Max-Planck-Institut für Biogeochemie (MPI-BGC), University of Illinois at Urbana-Champaign Urbana (UIUC), University of Illinois System, Tsinghua University Beijing (THU), Max Planck Institute for Biogeochemistry (MPI-BGC), Max-Planck-Gesellschaft, Lawrence Berkeley National Laboratory Berkeley (LBNL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Carbon cycle; Carbon dioxide; Ecological models; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Barrow; Alaska
• Online Access: https://hal.science/hal-02899764; https://hal.science/hal-02899764/document; https://hal.science/hal-02899764/file/qt961981nz.pdf; https://doi.org/10.1175/JCLI-D-18-0653.1

International audience Carbon balance of terrestrial ecosystems in the northern high latitudes (NHL) is sensitive to climate change. It remains uncertain whether current regional carbon uptake capacity can be sustained under future warming. Here the atmospheric CO2 drawdown rate (CDR) between 1974 and 2014, defined as the CO2 decrease in ppm over the number of days in spring or summer, is estimated using atmospheric CO2 observations at Barrow (now known as Utqiaġvik), Alaska. We found that the sensitivity of CDR to interannual seasonal air temperature anomalies has trended toward less carbon uptake for a given amount of warming over this period. Changes in interannual temperature sensitivity of CDR suggest that relatively warm springs now result in less of a carbon uptake enhancement. Similarly, relatively warm summers now result in greater carbon release. These results generally agree with the sensitivity of net carbon exchange (NCE) estimated by atmospheric CO2 inversion. When NCE was aggregated over North America (NA) and Eurasia (EA), separately, the temperature sensitivity of NCE in NA has changed more than in EA. To explore potential mechanisms of this signal, we also examine trends in interannual variability of other climate variables (soil temperature and precipitation), satellite-derived gross primary production (GPP), and Trends in Net Land–Atmosphere Carbon Exchanges (TRENDY) model ensemble results. Our analysis suggests that the weakened spring sensitivity of CDR may be related to the slowdown in seasonal soil thawing rate, while the summer sensitivity change may be caused by the temporally coincident decrease in temperature sensitivity of photosynthesis. This study suggests that the current NHL carbon sink may become unsustainable as temperatures warm further. We also found that current carbon cycle models do not represent the decrease in temperature sensitivity of net carbon flux. We argue that current carbon–climate models misrepresent important aspect of the carbon–climate feedback and bias the ...