Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3
Thawing of permafrost in a warming climate is governed by a complex interplay of different processes of which only conductive heat transfer is taken into account in most model studies. However, observations in many permafrost landscapes demonstrate that lateral and vertical movement of water can hav...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-02-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/9/523/2016/gmd-9-523-2016.pdf |
| Summary: | Thawing of permafrost in a warming climate is governed by a complex interplay
of different processes of which only conductive heat transfer is taken into
account in most model studies. However, observations in many permafrost
landscapes demonstrate that lateral and vertical movement of water can have a
pronounced influence on the thaw trajectories, creating distinct landforms, such as thermokarst ponds and lakes, even in areas where permafrost is otherwise
thermally stable. Novel process parameterizations are required to include
such phenomena in future projections of permafrost thaw and subsequent climatic-triggered
feedbacks. In this study, we present a new land-surface scheme
designed for permafrost applications, CryoGrid 3, which constitutes a
flexible platform to explore new parameterizations for a range of permafrost
processes. We document the model physics and employed parameterizations for
the basis module CryoGrid 3, and compare model results with in situ
observations of surface energy balance, surface temperatures, and ground
thermal regime from the Samoylov permafrost observatory in NE Siberia. The
comparison suggests that CryoGrid 3 can not only model the evolution of the
ground thermal regime in the last decade, but also consistently reproduce the
chain of energy transfer processes from the atmosphere to the ground. In
addition, we demonstrate a simple 1-D parameterization for thaw processes in
permafrost areas rich in ground ice, which can phenomenologically reproduce
both formation of thermokarst ponds and subsidence of the ground following
thawing of ice-rich subsurface layers. Long-term simulation from 1901 to 2100
driven by reanalysis data and climate model output demonstrate that the
hydrological regime can both accelerate and delay permafrost thawing. If
meltwater from thawed ice-rich layers can drain, the ground subsides, as well as the formation of a talik, are delayed. If the meltwater pools at
the surface, a pond is formed that enhances heat transfer in the ground and
leads to the formation of a talik. The model results suggest that the
trajectories of future permafrost thaw are strongly influenced by the
cryostratigraphy, as determined by the late Quaternary history of a site. |
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| ISSN: | 1991-959X 1991-9603 |