Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 3111-3134, 2014
https://doi.org/10.5194/gmd-7-3111-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
18 Dec 2014
A simplified permafrost-carbon model for long-term climate studies with the CLIMBER-2 coupled earth system model
K. A. Crichton1,2, D. M. Roche3,4, G. Krinner1,2, and J. Chappellaz1,2 1CNRS, LGGE (UMR5183), 38041 Grenoble, France
2Univ. Grenoble Alpes, LGGE (UMR5183), 38041 Grenoble, France
3CEA/INSU-CNRS/UVSQ, LSCE (UMR8212), Centre d'Etudes de Saclay CEA-Orme des Merisiers, bat. 701 91191 Gif-sur-Yvette CEDEX, France
4Cluster Earth and Climate, Department of Earth Sciences, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
Abstract. We present the development and validation of a simplified permafrost-carbon mechanism for use with the land surface scheme operating in the CLIMBER-2 earth system model. The simplified model estimates the permafrost fraction of each grid cell according to the balance between modelled cold (below 0 °C) and warm (above 0 °C) days in a year. Areas diagnosed as permafrost are assigned a reduction in soil decomposition rate, thus creating a slow accumulating soil carbon pool. In warming climates, permafrost extent reduces and soil decomposition rates increase, resulting in soil carbon release to the atmosphere. Four accumulation/decomposition rate settings are retained for experiments within the CLIMBER-2(P) model, which are tuned to agree with estimates of total land carbon stocks today and at the last glacial maximum. The distribution of this permafrost-carbon pool is in broad agreement with measurement data for soil carbon content. The level of complexity of the permafrost-carbon model is comparable to other components in the CLIMBER-2 earth system model.

Citation: Crichton, K. A., Roche, D. M., Krinner, G., and Chappellaz, J.: A simplified permafrost-carbon model for long-term climate studies with the CLIMBER-2 coupled earth system model, Geosci. Model Dev., 7, 3111-3134, https://doi.org/10.5194/gmd-7-3111-2014, 2014.
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Short summary
Permafrost is ground that remains frozen for two or more consecutive years. An estimated 50% of the global below-ground organic carbon is stored in soils of the permafrost zone. This study presents the development and validation of a simplified permafrost-carbon mechanism for the CLIMBER-2 model. Our model development allows, for the first time, the study of the role of permafrost soils in the global carbon cycle for long timescales and for coupled palaeoclimate Earth system modelling studies.
Permafrost is ground that remains frozen for two or more consecutive years. An estimated 50% of...
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