Several Arctic and boreal research studies have shown the strong role of high latitude terrestrial ecosystems in the modulation of the climate by exchange of energy, momemtum and moisture between land surface and atmosphere. The changes in climate also have consequences on ecosystems and ecosystem carbon fluxes due to the ecosystems sensitivity to temperature and precipitation changes. A difference in temperature of ±1K can be decisive for the survival or death of plants. Therefore, it is essential to better understand the feedback between climate and ecosystem changes. To assess the influence of ecosystem-induced summer albedo changes occurring north of 50N on climate the Community Climate System Model version 3 (CCSM3) simulations are performed without and in conjunction with the summer-albedo change data from simulations performed with the Terrestrial Ecosystem Model (TEM version 7) for 2003 to 2053. These simulations are denoted REF and ALB hereafter.
The spatial distribution of TEM-simulated summer albedo shows mostly a decrease over the Pan-Arctic, corresponding to an increase in aboveground vegetation biomass. With decreasing summer albedo one would expect an increase in soil and near-surface temperatures. However, near-surface temperature decreases up to 1.5K in Alaska, western and southern Siberia, central Asia, the Middle East, China, the eastern and western part of Africa and South America. The decease in near-surface temperature occurring over Pan-Arctic may be caused due to increasing cloudiness over North Atlantic Ocean and western Siberia whereas the decrease in temperature occurring outside the range of albedo changed likely reflects the change in surface wind speed in response to albedo change. Consequently, the advection of cold air from western and southern Siberia is enhanced. Intensification of the tropical easterly jet in ALB is responsible for advection of cold air from southern Siberia to eastern and w! estern part of Africa and South America in summer. Near-surface temperature also decreases in winter and spring due to increase in snow cover. Changes in soil temperature follow the same pattern as near-surface temperature.