An Assessment of Thermokarst Driven Changes in Land Cover of the Tanana Flats Wetland Complex of Alaska from 2009 to 2100 in response to Climate Warming

Abstract:

Ongoing climate warming has the potential to affect terrestrial ecosystems and the services they provide to local and regional communities, particularly in high latitude regions. Rising temperatures have increased permafrost vulnerability to thawing. In boreal region, ice-rich permafrost degradation may result in the subsidence of the ground surface and the transition from permafrost plateau forest to wetland ecosystems, with dramatic changes in ecosystem structure and function, e.g. vegetation composition, energy balance, and carbon and nutrient cycles. However, this disturbance is poorly represented in existing ecosystem models. A state-and-transition model, the Alaska Thermokarst Model (ATM), is being developed to predict thermokarst initiation and expansion and to keep track of the associated vegetation transitions in boreal and arctic regions. The drivers of these transitions in the boreal region are highly related to climate, topography, fire disturbance and forest fragmentation. In this study, we applied the ATM in a large wetland complex in Interior Alaska (the Tanana Flats) to predict changes in land cover associated to thermokarst from 2009 to 2100. Preliminary simulations over a 10 km x 10 km area of the Tanana Flats suggests that permafrost plateau forests will decrease by 34.9% and collapse scar fens and bogs will increase by 88.3% in this region. After further testing and refinement of the ATM, a next step will be to couple the ATM with a process-based ecosystem model to evaluate the effects of thermokarst dynamics on carbon dynamics.