Biome differences in surface energy balance strongly affect climate. However, arctic vegetation is considered sufficiently uniform that only a single arctic land surface type is generally used in climate models. Field measurements in northern Alaska show large differences among arctic ecosystem types in summer energy absorption and partitioning. Simulations with the Arctic Regional Climate System Model demonstrate that these variations in land surface parameters and ecological processes cause variation in surface fluxes that is sufficiently large to affect the regional climate. Plausible changes in arctic vegetation in response to high-latitude warming would feed back positively to local summer warming. This local warming could extend into the boreal zone. Climate feedbacks that operate during the growing season are particularly likely to impact vegetation and ecosystem properties. These field and model results suggest that vegetation changes within a biome could be climatically important and warrant consideration in regional climate modeling.