Snow Cover Amplification and Permafrost Response to Vegetation Greenness Variation in the Arctic Tundra

The permafrost response to changes in Arctic vegetation remains controversial. We simulated the consequences of Arctic vegetation variation over the recent three decades using the Community Earth System Model and found that the greenness induced feedbacks were too weak to directly affect permafrost. However, such changes induced an air temperature perturbation, which is further amplified by the snow cover variation and finally leaves a footprint on soil temperature. While soil temperature at 1 m depth was affected little at the location with maximum increase of leaf area index, we found significant soil warming along the summer snowline between the Low and High Arctic, indicating a direct impact of snow cover variation. In the Low Arctic, the winter snowpack insulated the soil from colder air, resulting in less permafrost. In the High Arctic, snow persisted in the summer and had a strong protecting effect on permafrost by insulating soil from warmer summer air and reflecting solar radiation.