Representation of northern peatlands in a surface model : development of a hydrological scheme and estimates of their methane emissions

• Main Author: Largeron, Chloé
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Université Grenoble Alpes, Gerhard Krinner, Philippe Ciais
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2016
• Subjects: Permafrost; Model; Land surface; Methane; Projections; Peatland; Pergélisols; Modèle; Surface continentale; Méthane; Projections futures; Tourbières; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; permafrost
• Online Access: https://theses.hal.science/tel-01724557; https://theses.hal.science/tel-01724557/document; https://theses.hal.science/tel-01724557/file/LARGERON_2016_archivage.pdf

Peatlands are widely present in northern latitudes and especiallyin permafrost regions. They contain a high carbon stock and are one ofthe greatest natural sources of methane. Their representation in a climate model is crucial to improve the one of the carbon cycle. Moreover, the contribution of methanepeatland emissions remains uncertain.Methane emissions from peatlands strongly depend on the climate and are influenced primarily by temperature and soil moisture. Meanwhile, climate change is particularlysevere at these latitudes and leads to thawing permafrost with increasing the active layer depth. This large carbon reservoir may be partially mobilized and emitted asCO2 or CH4, depending on hydrological conditions at the surface.The aim of this PhD thesis is to represent northern peatlands in the ORCHIDEE land surface model. This development is carried out in the version of the model that incorporatesprocesses in high latitudes such as the soil freezing. Peatlands are represented by a specific hydrological scheme which improves the exchange of energy and water. The difficulty isbased on the representation of local peatlands processes across a global climate model. Some biological properties were also considered to represent bettervegetation of these environments. To do so, peatlands are integrated as a new type ofvegetation and represented by a fraction of a grid, based on observations. Thehydrological behaviour and the impact of this integration are estimated at the boreal scale as well asregionally. This development then allows estimate changes in the hydrology of peatlands due to global warming. Studying the changes in hydrology of peatlands by the end of th 21st century will improve the prediction of future changes in their CH4 emissions.This development work was then applied to determine the evolution of methane emissions. Peatlands are one of the largest natural sources of methane and control more than 70% interannual variability of atmospheric concentration of CH4. Methane emissions result from various ...