Investigating the Spread of Surface Albedo and Snow Sensitivity in CMIP6 Models

Abstract:

A large spread in surface albedo in the presence of snow (particularly across the boreal forest) was found in climate models evaluated during Phase 3 and Phase 5 of the Coupled Model Intercomparison Project (CMIP). We demonstrate that this large albedo spread persists in CMIP6 climate models. Knowledge based on the previous generations of CMIP models has shown that for the Northern Hemisphere on average, the large surface albedo spread is the primary source of uncertainties in simulated snow-albedo feedback strength, which accounts for much of the spread in simulated 21st century warming at high northern latitudes. However, the albedo biases depend heavily on the prescribed vegetation characteristics as well as their modeled interactions with snow. Furthermore, the contributions of model variation in the sensitivity of snow loss to the spread in snow albedo feedback are non-negligible. Based on these expectations we examine how CMIP6 model spread in simulated surface albedo varies regionally accounting for vegetation type and considering differences in the modeled sensitivity of snow cover loss. Preliminary results of this analysis will inform a large portion of uncertainty related to linkages between land cover, simulated winter albedo, snow sensitivity and warming across different vegetation dominated regions of the Northern hemisphere middle to high latitudes.