Distributed Global Debris Thickness Estimates Reveal Debris Significantly Impacts Glacier Mass Balance
David R. Rounce, Regine Hock, Robert McNabb, Romain Millan, Christian Sommer, Matthias Braun, Philipp Malz, Fabien Maussion, J. Mouginot, Thorsten Seehaus, David Shean
Abstract
Abstract Supraglacial debris affects glacier mass balance as a thin layer enhances surface melting, while a thick layer reduces it. While many glaciers are debris‐covered, global glacier models do not account for debris because its thickness is unknown. We provide the first globally distributed debris thickness estimates using a novel approach combining sub‐debris melt and surface temperature inversion methods. Results are evaluated against observations from 22 glaciers. We find the median global debris thickness is ∼0.15 ± 0.06 m. In all regions, the net effect of accounting for debris is a reduction in sub‐debris melt, on average, by 37%, which can impact regional mass balance by up to 0.40 m water equivalent (w.e.) yr ‐1 . We also find recent observations of similar thinning rates over debris‐covered and clean ice glacier tongues is primarily due to differences in ice dynamics. Our results demonstrate the importance of accounting for debris in glacier modeling efforts.