Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3

Geoscientific Model Development

J.Boike¹  B.Etzelmüller¹  S.Westermann¹  M.Heikenfeld¹  M.Peter¹  M.Langer¹  G.Krinner¹ 

DOI  :  10.5194/gmd-9-523-2016

学科分类：天文学(综合)

来源: Copernicus Publications

【 摘 要 】

Thawing of permafrost in a warming climate is governed by a complex interplayof different processes of which only conductive heat transfer is taken intoaccount in most model studies. However, observations in many permafrostlandscapes demonstrate that lateral and vertical movement of water can have apronounced influence on the thaw trajectories, creating distinct landforms, such as thermokarst ponds and lakes, even in areas where permafrost is otherwisethermally stable. Novel process parameterizations are required to includesuch phenomena in future projections of permafrost thaw and subsequent climatic-triggeredfeedbacks. In this study, we present a new land-surface schemedesigned for permafrost applications, CryoGrid 3, which constitutes aflexible platform to explore new parameterizations for a range of permafrostprocesses. We document the model physics and employed parameterizations forthe basis module CryoGrid 3, and compare model results with in situobservations of surface energy balance, surface temperatures, and groundthermal regime from the Samoylov permafrost observatory in NE Siberia. Thecomparison suggests that CryoGrid 3 can not only model the evolution of theground thermal regime in the last decade, but also consistently reproduce thechain of energy transfer processes from the atmosphere to the ground. Inaddition, we demonstrate a simple 1-D parameterization for thaw processes inpermafrost areas rich in ground ice, which can phenomenologically reproduceboth formation of thermokarst ponds and subsidence of the ground followingthawing of ice-rich subsurface layers. Long-term simulation from 1901 to 2100driven by reanalysis data and climate model output demonstrate that thehydrological regime can both accelerate and delay permafrost thawing. Ifmeltwater from thawed ice-rich layers can drain, the ground subsides, as well as the formation of a talik, are delayed. If the meltwater pools atthe surface, a pond is formed that enhances heat transfer in the ground andleads to the formation of a talik. The model results suggest that thetrajectories of future permafrost thaw are strongly influenced by thecryostratigraphy, as determined by the late Quaternary history of a site.

【 授权许可】

Unknown