Impact of Vegetation Change on Surface Energy Budget during Growing Seasons in the Arctic

Vegetation change induced by the global warming has motivated active research on energy-water budgets at high latitudes. Treeline has been advancing in the Polar Ural Mountains of Russia, yet a substantial loss of tree cover was observed for a range of locations based on the 20-year record of MODIS NDVI and vegetation data. Due to the scarce volume of direct observations of heat fluxes in the high-latitude regions with pronounced vegetation changes, impacts on surface energy budget remains little explored, particularly at the regional scales. A physically based model, maximum entropy production model (MEP), is used to estimate surface energy budgets at the boreal forest - tundra transitional zone of Western Siberia between 2000 and 2020. The model is validated using field data from energy budget towers in the Polar Ural Mountains that have been monitoring the transitional zone of vegetation change from forest to tundra since 2018. Latent heat flux is found to be the most sensitive component of surface energy budget to the vegetation change with negative correlation. Net radiation, sensible heat flux, and ground heat flux are less sensitive to vegetation change during growing seasons. The improved understanding of the relationship between vegetation cover change and surface energy budget provides insights on how future Arctic ecosystems will impact its terrestrial energy-water relations the Arctic.