Amplification of climate model response to snow cover fraction parameterization through dynamic vegetation

We investigate the response of the Community Climate System Model to two different methods for estimating snow cover fraction. In the control case, snow cover fraction changes gradually with snow depth; in the alternative method, snow cover fraction initially increases with snow depth almost twice as fast as the control method. In cases where the vegetation was fixed, the choice of snow cover parameterization resulted in a very limited response of the model. With dynamic vegetation, however, the change was much more dramatic, where slight initial increases in snow cover fraction with the new parameterization led to large scale retreat of boreal vegetation, widespread cooling, and persistent snow cover over much of the boreal region during the boreal summer. This study highlights the importance of dynamic vegetation, both as an amplifier of feedbacks in the climate system and an essential consideration when implementing adjustments to existing model parameters and algorithms.