Soil freezing has several direct and indirect impacts on climate. Particularly, it is ex- pected to play an important role in the climate's sensitivity in northern latitudes. In- deed, it directly influences high latitudes temperatures through large storage and re- lease heat at the interseasons, delaying cooling in autumn and warming in spring. Freezing also modifies the thermal and hydrological soil properties, leading to wa- terlogged soil and (seasonal) wetlands in high latitudes. Here, we focus on the direct thermal effect of soil freezing on climate change with the analysis of four GCM sim- ulations, performed with the french model LMDz, which has been adapted to polar climates. Runs were carried out both with the soil freezing process and without it . In each case, two runs correspond to modern climate and two others represent the end of the 21st century. Present-Day and Future simulations display some changes aspects of the surface temperature, precipitation, and soil humidity when taking into account for soil freezing. Two soil mechanisms (a thermal effect of frozen ground and an hy- drological effect) are identified and strongly constrain surface temperatures in boreal regions. We will also specifically discuss how possible feedbacks due to freezing in a GCM can modify regionally the simulated response of the model to anthropogenic climate forcing. We observe particularly different impacts of soil freezing on climate change in North America and Siberia, two regions where snow cover has a substential impact on freezing and thawing processes.
EGS General Assembly Conference Abstracts
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