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The Arctic is currently experiencing strong warming and associated environmental change. Threshold and non-linear responses associated with phase change between ice and water leave the terrestrial Arctic particularly susceptible to swift and disruptive transitions. A large-scale thawing of permafrost could initiate a diverse array of changes to Arctic vegetation, hydrology, and carbon cycling that can feedback onto the global climate system both positively and negatively. The magnitude of these potential terrestrial Arctic feedbacks remains difficult to quantify.
We will describe targeted improvements in the representation of permafrost in the Community Land Model (CLM) that address existing limitations in the capacity of Earth System Models to quantify permafrost-initiated terrestrial Arctic feedbacks. These improvements include updates to soil hydrology and thermodynamics, snow, and biogeochemical cycling.
We will show projections of 21st century permafrost thaw with the latest version of CESM/CLM and also projections from other global earth system models. We will then synthesize our current understanding, based in part on the improved CLM, of the integrated impact of projected permafrost thaw on the global climate system. Finally, scientific priorities from the observational, experimental, and modeling perspectives that are needed to better understand the permafrost carbon feedback will be outlined.