Projected changes in atmospheric heating due to changes in fire disturbance and the snow season in the western Arctic, 2003-2100

In high latitudes, changes in climate impact fire regimes and snow cover duration, altering the surface albedo and the heating of the regional atmosphere. In the western Arctic, under four scenarios of future climate change and future fire regimes (2003-2100), we examined changes in surface albedo and the related changes in regional atmospheric heating due to: (1) vegetation changes following a changing fire regime, and (2) changes in snow cover duration. We used a spatially explicit dynamic vegetation model (Alaskan Frame-based Ecosystem Code) to simulate changes in successional dynamics associated with fire under the future climate scenarios, and the Terrestrial Ecosystem Model to simulate changes in snow cover. Changes in summer heating due to the changes in the forest stand age distributions under future fire regimes showed a slight cooling effect due to increases in summer albedo (mean across climates of -0.9 W m(-2) decade(-1)). Over this same time period, decreases in snow cover (mean reduction in the snow season of 4.5 d decade(-1)) caused a reduction in albedo, and a heating effect (mean across climates of 4.3 W m(-2) decade(-1)). Adding both the summer negative change in atmospheric heating due to changes in fire regimes to the positive changes in atmospheric heating due to changes in the length of the snow season resulted in a 3.4 W m(-2) decade(-1) increase in atmospheric heating. These findings highlight the importance of gaining a better understanding of the influences of changes in surface albedo on atmospheric heating due to both changes in the fire regime and changes in snow cover duration.