TY - JOUR
T1 - On the influence of debris cover on glacier morphology
T2 - How high-relief structures evolve from smooth surfaces
AU - Mölg, Nico
AU - Ferguson, James
AU - Bolch, Tobias
AU - Vieli, Andreas
N1 - Funding Information:
This study was funded by the SNSF project #200021_169775 “Understanding and quantifying the transient dynamics and evolution of debris-covered glaciers”. We greatly appreciate the provision of the ice thickness data by A. Bauder, the Laboratory of Hydraulics, Hydrology and Glaciology (VAW), and the group of Exploration and Environmental Geophysics (EEG) of ETH Zurich. Debris thickness measurements were conducted and supported by R. Ganarin, A. Cicoira and M. Schulthess. The UAV campaign was supported by A. Cicoira. The authors appreciate the constructive and open comments by D. Swift and an anonymous reviewer and acknowledge their contribution to the improvement of this manuscript.
Funding Information:
This study was funded by the SNSF project #200021_169775 “Understanding and quantifying the transient dynamics and evolution of debris-covered glaciers”. We greatly appreciate the provision of the ice thickness data by A. Bauder, the Laboratory of Hydraulics, Hydrology and Glaciology (VAW), and the group of Exploration and Environmental Geophysics (EEG) of ETH Zurich. Debris thickness measurements were conducted and supported by R. Ganarin, A. Cicoira and M. Schulthess. The UAV campaign was supported by A. Cicoira. The authors appreciate the constructive and open comments by D. Swift and an anonymous reviewer and acknowledge their contribution to the improvement of this manuscript.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/5/15
Y1 - 2020/5/15
N2 - Debris-covered glaciers receive increasing attention during the current period of sustained negative mass balance and expanding debris cover. The debris cover induces various feedback mechanisms that shape the evolution of the glacier geometry, and also the glacier surface. Although the surface morphology of many debris-covered glaciers is markedly different from that of debris-free glaciers, only a few studies have combined different processes to investigate these characteristic glacier surfaces in order to improve our knowledge of glacier evolution on a wider spatial and temporal scale. Debris-covered glacier tongues can consist of parts with a smooth surface as well as surfaces of high local relief with abundant ice cliffs in the lower end. In this study we analysed the evolution of the surface features of Zmuttgletscher, a debris-covered glacier in Switzerland, over a period of 140 years using time series of historic maps, high resolution digital elevation models and glacier velocities, as well as data on debris cover extent and thickness. Our results reveal insights into the up-glacier expansion of the debris cover over time and the formation of medial moraines in the prolongation of the uppermost areas where debris emerged on the glacier surface. Moraine ridge prominence increased during periods of negative mass balance, and troughs developed in debris-free areas between ridges, persisting even after a continuous debris cover had developed. The changing surface morphology inhibits across-glacier meltwater flow, both supra- and subglacially. Accordingly, we found that large cryo-valleys with ice cliffs have formed down-glacier of the troughs where meltwater runoff accumulates. The meanders of these valleys have enlarged over time, especially by ice cliff backwasting at steep slopes, and most of the glacier width today is affected by such high-relief erosion features. We find that about 75% of all ice cliffs are located in this high-relief zone. The volume lost at these erosion features has increased by a factor of five since the 1980s, but is still very small in comparison to the high glacier-wide thinning rates.
AB - Debris-covered glaciers receive increasing attention during the current period of sustained negative mass balance and expanding debris cover. The debris cover induces various feedback mechanisms that shape the evolution of the glacier geometry, and also the glacier surface. Although the surface morphology of many debris-covered glaciers is markedly different from that of debris-free glaciers, only a few studies have combined different processes to investigate these characteristic glacier surfaces in order to improve our knowledge of glacier evolution on a wider spatial and temporal scale. Debris-covered glacier tongues can consist of parts with a smooth surface as well as surfaces of high local relief with abundant ice cliffs in the lower end. In this study we analysed the evolution of the surface features of Zmuttgletscher, a debris-covered glacier in Switzerland, over a period of 140 years using time series of historic maps, high resolution digital elevation models and glacier velocities, as well as data on debris cover extent and thickness. Our results reveal insights into the up-glacier expansion of the debris cover over time and the formation of medial moraines in the prolongation of the uppermost areas where debris emerged on the glacier surface. Moraine ridge prominence increased during periods of negative mass balance, and troughs developed in debris-free areas between ridges, persisting even after a continuous debris cover had developed. The changing surface morphology inhibits across-glacier meltwater flow, both supra- and subglacially. Accordingly, we found that large cryo-valleys with ice cliffs have formed down-glacier of the troughs where meltwater runoff accumulates. The meanders of these valleys have enlarged over time, especially by ice cliff backwasting at steep slopes, and most of the glacier width today is affected by such high-relief erosion features. We find that about 75% of all ice cliffs are located in this high-relief zone. The volume lost at these erosion features has increased by a factor of five since the 1980s, but is still very small in comparison to the high glacier-wide thinning rates.
KW - Debris-covered glacier
KW - Ice cliffs
KW - Medial moraine
KW - Surface morphology
UR - http://www.scopus.com/inward/record.url?scp=85080040137&partnerID=8YFLogxK
U2 - 10.1016/j.geomorph.2020.107092
DO - 10.1016/j.geomorph.2020.107092
M3 - Article
AN - SCOPUS:85080040137
SN - 0169-555X
VL - 357
JO - Geomorphology
JF - Geomorphology
M1 - 107092
ER -