Glacier Boundary Layer Thermal Coupling and Nonlinear Warming Feedbacks

Abstract

Abstract

Mountain glaciers are considered one of the sentinels of climate change. Their response to atmospheric warming is usually supposed to be linear and spatially uniform. Recent observational and modelling studies indicate that the near-surface processes in the boundary layer of glaciers are a very strong control over glacier-atmosphere interactions and create partial thermal decoupling between glacier surface air temperatures and the outer atmosphere. This buffering effect results from due to katabatic wind and surface energy balance processes, which reduce glacier melt rates due to warming in the region, but, as glaciers thin, fragment, and recede, the buffering effect diminishes, leading to nonlinear warming feedbacks and sudden increases in melt rates. The review provides existing knowledge about the thermal coupling of glacier boundary layers (GBLs), the processes of decoupling and recoupling, and findings on the implications of the process on glacier mass- balance modelling. Understanding boundary layer dynamics is essential for improving projections of the glacier change, hydrological impacts, and climate interactions in a warming world.