Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models

• Published in: Biogeosciences
• Main Authors: Chadburn, Sarah, Krinner, Gerhard, Porada, Philipp, Bartsch, Annett, Beer, Christian, Belelli Marchesini, Luca, Boike, Julia, Ekici, Altug, Elberling, Bo, Friborg, Thomas, Hugelius, Gustaf, Johansson, Margareta, Kuhry, Peter, Kutzbach, Lars, Langer, Moritz, Lund, Magnus, Parmentier, Frans-Jan, Peng, Shushi, van Huissteden, Ko, Wang, Tao, Westermann, Sebastian, Zhu, Dan, Burke, Eleanor
• Other Authors: School of Earth and Environment Leeds (SEE), University of Leeds, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Department of Environmental Science and Analytical Chemistry Stockholm (ACES), Stockholm University, Department of Geodesy and Geoinformation Wien, Vienna University of Technology (TU Wien), School of Natural Sciences Vladivostok, Far Eastern Federal University (FEFU), Department of Earth Sciences Amsterdam, VU University Amsterdam, Alfred Wegener Institute Potsdam, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Department of Geosciences and Natural Resource Management Copenhagen (IGN), Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Department of Physical Geography Stockholm, Department of Physical Geography and Ecosystem Science Lund, Lund University Lund, Center for Earth System Research and Sustainability (CEN), Universität Hamburg (UHH), Alfred Wegener Institute for Polar and Marine Research (AWI), Aarhus University Aarhus, The Arctic University of Norway (UiT), Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University Beijing, Key Laboratory of Tibetan Environment Changes and Land Surface Processes - Institute of Tibetan Plateau Research, Institute of Tibetan Plateau Research - Chinese Academy of Sciences, Department of Geosciences Oslo, Faculty of Mathematics and Natural Sciences Oslo, University of Oslo (UiO)-University of Oslo (UiO), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Met Office Hadley Centre for Climate Change (MOHC), United Kingdom Met Office Exeter, European Project: 282700,EC:FP7:ENV,FP7-ENV-2011,PAGE21(2011)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Arctic; Jules; permafrost; Tundra
• Online Access: https://hal.archives-ouvertes.fr/hal-03225838; https://hal.archives-ouvertes.fr/hal-03225838/document; https://hal.archives-ouvertes.fr/hal-03225838/file/bg-14-5143-2017.pdf; https://doi.org/10.5194/bg-14-5143-2017

International audience It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow. We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI. The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that an improved simulation ...