Abstract
Abstract. During the Last Glacial Maximum (LGM), a very cold and dry period around 26.5–19 kyr BP, permafrost was widespread across Europe. In this work, we explore the possible benefit of using regional climate model data to improve the permafrost representation in France, decipher how the atmospheric circulation affects the permafrost boundaries in the models, and test the role of ground thermal contraction cracking in wedge development during the LGM. With these aims, criteria for possible thermal contraction cracking of the ground are applied to climate model data for the first time. Our results show that the permafrost extent and ground cracking regions deviate from proxy evidence when the simulated large-scale circulation in both global and regional climate models favours prevailing westerly winds. A colder and, with regard to proxy data, more realistic version of the LGM climate is achieved given more frequent easterly winds conditions. Given the appropriate forcing, an added value of the regional climate model simulation can be achieved in representing permafrost and ground thermal contraction cracking. Furthermore, the model data provide evidence that thermal contraction cracking occurred in Europe during the LGM in a wide latitudinal band south of the probable permafrost border, in agreement with field data analysis. This enables the reconsideration of the role of sand-wedge casts to identify past permafrost regions.
Highlights
Permafrost is an important component of the climate system and is sensitive to variations in climate
The aim of this study is (1) to explore the possible benefit of using regional climate model data to improve the permafrost representation over France, (2) to decipher how the atmospheric circulation affect the permafrost boundaries in the models and (3) to test the role of ground thermal contraction cracking in wedge development during the Last Glacial Maximum (LGM)
We present the large-scale characteristics of the LGM climate derived from global climate model data that is used for dynamical downscaling in comparison with the respective PI simulations
Summary
Permafrost is an important component of the climate system and is sensitive to variations in climate. While enhanced greenhouse gas forcing leads to warming temperatures and, to permafrost thawing, the thawing itself leads to the release of greenhouse gases that were previously bound within the frozen soils. The greenhouse effect is enhanced and leads to further warming of the climate in a positive feedback (e.g. IPCC, 2019; Liu and Jiang, 2016a; Schuur et al, 2015). Current climate model simulations project a large range of uncertainties regarding the decrease in permafrost areas (e.g. IPCC, 2019; Schuur et al, 2015). It is necessary to evaluate the climate models under a wider range of climate conditions. This can be achieved by simulating past climates and comparing the results with proxy evidence
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