Meteorological Feedbacks on a Decaying Alpine Glacier

A developed boundary layer can decouple a glacier's response to the ambient meteorological conditions, though glacier retreat can limit this boundary layer development and increase a glacier’s sensitivity to climate change. We explore six years of distributed meteorological data on a small Swiss glacier in the period 2001-2022 to highlight its changing response to local conditions. We find an increased sensitivity (ratio) of on-glacier to off-glacier temperature changes as the glacier has retreated and its debris-cover area expanded. The glacier lost ~60% of area since 1994, coinciding with notable frontal retreat post 2005 and an observed switch from down-glacier to up-glacier winds in the upper ablation zone from 2001-2022. Increased sensitivity to external temperature changes is thus driven by a combination of increased up-glacier winds and the larger extent of ice exposed to warm air at a retreating, debris-covered glacier terminus. Calculated sensible heat fluxes on the glacier are therefore increasingly determined by the conditions occurring outside the boundary layer of the glacier, highlighting the expected negative feedback of smaller Alpine glaciers as the climate continues to warm and experience an increased frequency of extreme summers.