Rock glaciers on the run – understanding rock glacier landform evolution and recent changes from numerical flow modeling

Abstract

Abstract. Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment–ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment–ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.

The Dösen Rock Glacier in Central Austria: A key site for multidisciplinary long-term rock glacier monitoring in the Eastern Alps

“…The understanding of rock glacier kinematics and landform evolution is still in its infancy (Müller et al, 2016). Appropriate models for in-depth describing the dynamic behavior of rock glaciers do not exist at all.…”

“…This is mainly because the natural processes involved are to complex and hard to under-______ stand. For the time being only rather simple models exist which try to model rock glacier geometry and flow velocity as a function of, e.g., ground surface temperature, ice temperature changes and/or sediment input (Kääb et al, 2007;Hausmann et al, 2007;Müller et al, 2016). For example, these models can help to better understand or even proof the obvious correlation of surface temperature change with flow velocity change.…”

Rock glaciers in Daxue Shan, south-eastern Tibetan Plateau: an inventory, their distribution, and their environmental controls

“…In terms of their planar geometry, the length / width ratio was used to distinguish between lobate-(length / width ratio < 1) and tongue-shaped (length / width ratio > 1) rock glaciers ( Fig. 2) (Giardino and Vick, 1987;Martin, 1987;Barsch, 1996;Guglielmin and Smiraglia, 1998;Onaca et al, 2017). The overall aspect of each rock glacier was manually derived according to the main direction of flow.…”

“…Allen et al, 2008;Boeckli et al, 2012;Schmid et al, 2015;Sattler et al, 2016), and investigations of rock glacier dynamics (e.g. Haeberli et al, 2006;Liu et al, 2013;Müller et al, 2016;Wang et al, 2017b). However, compared with ice glaciers, rock glaciers remain poorly described and infrequently studied.…”

“…Bolch and Marchenko, 2009;Cremonese et al, 2011;Bolch and Gorbunov, 2014;Falaschi et al, 2014;Colucci et al, 2016;Janke et al, 2017;Wang et al, 2017b;Jones et al, 2018a), mapping of their spatial distributions and their relations with environmental controls such as topography and climate (e.g. Chueca, 1992;Brazier et al, 1998;Brenning, 2005;Janke, 2007;Johnson et al, 2007;Kenner and Magnusson, 2017;Onaca et al, 2017;Jones et al, 2018b), estimations of the distribution of permafrost based on rock glaciers (e.g. Allen et al, 2008;Boeckli et al, 2012;Schmid et al, 2015;Sattler et al, 2016), and investigations of rock glacier dynamics (e.g.…”