Physically Accurate Soil Freeze-Thaw Processes in a Global Land Surface Scheme

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Cuntz, Matthias, Haverd, Vanessa
• Other Authors: Ecologie et Ecophysiologie Forestières devient SILVA en 2018 (EEF), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Department Computational Hydrosystems UFZ Leipzig, Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research (UFZ), Commonwealth Scientific and Industrial Research Organisation (CSIRO)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: thaw; snow blizzards; soil; pergelisol; numerical models; global change; dégel; neige; stock de carbone; gel; sol; permafrost; modèle; changement climatique; [SDE.MCG]Environmental Sciences/Global Changes
• Online Access: https://hal.archives-ouvertes.fr/hal-01730005; https://doi.org/10.1002/2017MS001100

The model Soil-Litter-Iso (SLI) calculates coupled heat and water transport in soil. It was recently implemented into the Australian land surface model CABLE, which is the land component of the Australian Community Climate and Earth System Simulator (ACCESS). Here we extended SLI to include accurate freeze-thaw processes in the soil and snow. SLI provides thence an implicit solution of the energy and water balances of soil and snow as a standalone model and within CABLE. The enhanced SLI was tested extensively against theoretical formulations, laboratory experiments, field data, and satellite retrievals. The model performed well for all experiments at wide-ranging temporal and spatial scales. SLI melts snow faster at the end of the cold season compared to observations though because there is no subgrid variability within SLI given by the implicit, coupled solution of energy and water. Combined CABLE-SLI shows very realistic dynamics and extent of permafrost on the Northern hemisphere. It illustrated, however, also the limits of possible comparisons between large-scale land surface models and local permafrost observations. CABLE-SLI exhibits the same patterns of snow depth and snow water equivalent on the Northern hemisphere compared to satellite-derived observations but quantitative comparisons depend largely on the given meteorological input fields. Further extension of CABLE-SLI with depth-dependence of soil carbon will allow realistic projections of the development of permafrost and frozen carbon stocks in a changing climate.