Modeling the Soil Moisture Response to Permafrost Thaw and Implications for the Permafrost-Carbon Feedback

Abstract:

The Arctic is currently experiencing rapid environmental change. Numerous studies have shown clear evidence of change that is pervasive throughout the terrestrial Arctic system including widespread permafrost thaw and associated thermokarst initiation, changes in lake distribution, shifts in vegetation community composition, as well as changes in a host of other ecosystem, carbon cycle, and hydrologic processes. Threshold and non-linear responses associated with phase change between ice and water leave the Arctic particularly susceptible to swift and disruptive change. The fate of the Arctic carbon cycle including the potential release of soil carbon as carbon dioxide or methane, as well as any counterbalancing carbon accumulation via enhanced vegetation growth, is fundamentally governed by present and future soil hydrologic states. Prior research suggests that the hydrologic response may contain two phases, an initial wettening associated with ice melt and surface subsidence leading to more wetlands and lakes, followed by drying once the permafrost table has deepened enough to open up new channels to the groundwater system.

Utilizing a version of the Community Land Model (CLM), the land model of CESM, that includes advances in the representation of permafrost water and carbon dynamics, we will explore how soil moisture and the water cycle in permafrost regions may change in response to permafrost thaw and assess the implications for the permafrost-carbon feedback.