Quantifying the Thermal and Permafrost Impacts of a Tundra Wildfire

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

Alaska is a fire-dominated ecosystem differing from the northern forests of the continental U.S. and Canada in many important aspects. The fire-prone areas of Alaska are primarily in the interior boreal forest region. The discontinuous nature of the permafrost distribution tends to promote a mosaic of vegetation types with dense forests of fire-prone black spruce and thick organic layers developing in permafrost areas that have not burned in recent history. Fires also occur, on a lower frequency, in the treeless tundra regions of the Seward Peninsula and Yukon Kuskokwim Delta. Although the cause is uncertain, fire records demonstrate a marked positive trend in the numbers of fires over the last 50 years on the Seward Peninsula. It is obvious that these fires will have marked impacts on surface energy balance, soil moisture dynamics and permafrost thermal regime, but these changes and their interactions have not been quantified in tundra regions. The PIs have operated numerous meteorological stations with extensive soil instrumentation in four locations on the Seward Peninsula and near Ivotuk for four years. One of these stations was destroyed in a severe fire last fall, presenting a devastating loss of instrumentation and at the same time, a unique opportunity to document quantifiably how this system will change following a fire. The damaged equipment was replaced within a few months to maintain a nearly continuous record of measurements in the burn area. This work would maintain six meteorological stations currently operating in that area. The significant annual variation previously documented at these sites necessitates maintenance of all stations to permit characterization of changes due to the fire as opposed to those due to temporal variations in climate. In addition, the group will utilize this opportunity to investigate the impacts of tundra fire on the surface energy balance and subsurface thermal regime. These studies will attempt to characterize the subtle influence of burn severity on both short-term impacts and consequences for long-term recovery. They will maintain the series of meteorological stations to document changes in the surface energy balance and collect distributed measurements of active layer thickness on the existing 1 km2 CALM grid (half of which was burned) to enable comparisons with measurements collected during the previous four years. They will supplement these measurements with other distributed measurements of subsurface moisture and temperature to characterize the impacts of wildfire, particularly with respect to burn severity. Intellectual Merit: While wildfires in the boreal forest regions of the world have been extensively studied, little is known about the impacts of tundra fires on the local ecosystem, regional climate or the permafrost and hydrologic regime. The permafrost is quite close to the surface due to the insulative capability of the thick tundra mat. How this system responds to such a drastic disturbance has not been rigorously studied. The existing climatologic network within this basin provides the basis of immediately and economically documenting the impacts and the process of recovery. Quantitative information on these processes is very important in light of the recent changes in climate and hydrologic regimes. Broader Impacts: Wildfire is probably the dominant agent controlling land surface change in Arctic and subarctic regions. The dramatic impacts immediately following a fire are quite obvious, but the longer-term effects are probably more important in their influence upon regional and global climate dynamics. This research will document those impacts and project long term trajectories of recovery. This understanding is critically important for correct parameterization of dynamic vegetation models and the climate simulations that consider a changing land surface.