The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-292 Manuscript under review for journal The Cryosphere Discussion started: 18 January 2019 c Author(s) 2019. CC BY 4.0 License. The role of debris cover in the evolution of Zmuttgletscher, Switzerland, since the end of the Little Ice Age Nico Mölg1, Tobias Bolch1, Andrea Walter1, Andreas Vieli1 1Department of Geography, University of Zurich, Zurich, 8057, Switzerland 5 Correspondence to: Nico Mölg (
[email protected]) Abstract. Debris-covered glaciers often exhibit large, flat, slow-flowing tongues. Many of these glaciers show high thinning rates today despite thick debris cover. Due to lack of observations, most existing studies have neglected the dynamic interaction between debris cover and glacier evolution over longer time periods. The main aim of this study is to reveal this interaction by reconstructing changes of debris cover, glacier geometry, flow velocities, and surface features of Zmuttgletscher (Switzerland), 10 based on historic maps, satellite images, aerial photographs, and field observations. We show that debris cover extent has increased from ~13% to >32% of the total glacier surface since 1859 and that the debris is sufficiently thick to reduce ablation compared to bare ice over much of the ablation area. Despite the debris cover the volume loss of Zmuttgletscher is comparable to that of debris-free glaciers located in similar settings whereas changes in length and area have been small in comparison. Increased ice mass input in the 1970s and 1980s resulted in a temporary velocity increase, as well as a lowering of the upper 15 margin of debris cover and exposed-ice area, and a reduction of ice cliffs.