The ongoing acceleration in rock glacier velocities concurrent with increasing air temperatures, and the widespread onset of rock glacier destabilization have reinforced the interest in rock glacier dynamics and in its coupling to the climate system. Despite the increasing number of studies investigating this phenomenon, our knowledge of both the fundamental mechanisms controlling rock glacier dynamics, and their long‐term behaviour at the regional scale remain limited. We present a general theory to investigate rock glacier dynamics, its spatial patterns and temporal trends at both regional and local scale. To this end, we combine a model to calculate rock glacier thickness with an empirical creep model for ice‐rich debris, in order to derive the Bulk Creep Factor (BCF), which allows to disentangle the two contributions to the surface velocities from (i) material properties and (ii) geometry. Thereafter, we provide two examples of possible applications of this approach at a regional and local scale.
Rock glaciers—ice-rich creeping landforms typical of permafrost mountain ranges—can develop an anomalous landslide-like behaviour called destabilisation. This behaviour is characterised by failure mechanisms (including cracks and crevasses) and increases in displacement rates by one to two orders of magnitude. Existing studies of this phenomenon have been limited to a small number of landforms and short time spans. Here, we systematically investigate the evolution of rock glacier kinematics over the past seven decades for the entire French Alps by combining observations of landform features indicative of the onset of destabilisation with data on displacements rates using aerial orthoimagery. We show that rock glacier velocities have significantly increased since the 1990s, concurrent with the development of destabilisation in 18 landforms that represent 5% of the 337 active rock glaciers. This pattern of activity correlates with rising air temperatures in the region, which suggests that a warming climate may play a role in this process.
Abstract. In recent years, observations have highlighted seasonal and
interannual variability in rock glacier flow. Temperature forcing, through
heat conduction, has been proposed as one of the key processes to explain
these variations in kinematics. However, this mechanism has not yet been
quantitatively assessed against real-world data. We present a 1-D numerical modelling approach that couples heat conduction to
an empirically derived creep model for ice-rich frozen soils. We use this
model to investigate the effect of thermal heat conduction on seasonal and
interannual variability in rock glacier flow velocity. We compare the model
results with borehole temperature data and surface velocity measurements from
the PERMOS and PermaSense monitoring network available for the Swiss Alps. We
further conduct a model sensitivity analysis in order to resolve the
importance of the different model parameters. Using the prescribed
empirically derived rheology and observed near-surface temperatures, we are
able to model the correct order of magnitude of creep. However, both
interannual and seasonal variability are underestimated by an order of
magnitude, implying that heat conduction alone cannot explain the observed
variations. Therefore, we conclude that non-conductive processes, likely
linked to water availability, must dominate the short-term velocity signal.
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