Recent Acceleration of a Rock Glacier Complex, Ádjet, Norway, Documented by 62 Years of Remote Sensing Observations

Abstract

Recent acceleration of rock glaciers is well recognized in the European Alps, but similar behavior is hardly documented elsewhere. Also, the controlling factors are not fully understood. Here we provide evidence for acceleration of a rock glacier complex in northern Norway, from 62 years of remote sensing data. Average annual horizontal velocity measured by aerial feature tracking increased from ~0.5 myr−1 (1954–1977) to ~3.6 myr−1 (2006–2014). Measured by satellite synthetic aperture radar offset‐tracking, averages increased from ~4.9 to ~9.8 myr−1 (2009–2016) and maximum velocities from ~12 to ~69 myr−1. Kinematic analysis reveals different spatial‐temporal trends in the upper and the lower parts of the rock glacier complex, suggesting progressive detachment of the faster front. We suggest that permafrost warming, topographic controls, and increased water access to deeper permafrost layers and internal shear zones can explain the kinematic behavior.

Monitoring Rock Glacier Kinematics with Satellite Synthetic Aperture Radar

“…Facing the importance of documenting the changes occurring in the transfer rate of frozen debris over mountain slopes, the Swiss permafrost observation network PERMOS [18] has included a kinematics tier in its monitoring strategy, in addition to the observation of permafrost temperature and active layer trends. This is, however, not yet the case in other mountain regions or in the Global Terrestrial Network for Permafrost GTN-P [85], despite an increasing number of publications dedicated to this specific emerging geomorphological response to the climate warming [3,14,17,86,87]. In addition, inventories of rock glaciers and monitoring of rock glacier velocities is not explicitly mentioned by the Global Climate Observing System (GCOS) of the World Meteorological Organization (WMO) as being an essential climate variable (ECV) associated parameter, despite the fact that monitoring rock glacier velocities at the regional scale provides information on the impact of climate change on mountain slope stability, and rock glacier monitoring builds up a unique validation dataset of climate models for mountain regions, where direct permafrost (thermal state) measurements are scarce.…”

“…Rock glaciers typically occur in the following three forms: lobate (width-to-length ratio ≥1), tongue-shaped (width-to-length ratio <1), or spatulate (also termed piedmont type, these are tongue-shaped with a broadened terminus); depending on topography, several rock glaciers can merge or separate in flow direction [12,13].Annual rates of motion of rock glaciers range from a few millimeters (i.e., the lower boundary of detection accuracy) to several meters per year, whereby the surface of a rock glacier typically moves faster than the base through lateral velocities decreasing with depth. In addition, motion rates vary within the annual cycle [14], from year to year, as well as at the decennial time scale (e.g., [15][16][17][18]). During the last decade, an increasing number of studies have monitored in situ creep behavior of active rock glaciers in the European Alps [3,[18][19][20].…”

“…Annual rates of motion of rock glaciers range from a few millimeters (i.e., the lower boundary of detection accuracy) to several meters per year, whereby the surface of a rock glacier typically moves faster than the base through lateral velocities decreasing with depth. In addition, motion rates vary within the annual cycle [14], from year to year, as well as at the decennial time scale (e.g., [15][16][17][18]). During the last decade, an increasing number of studies have monitored in situ creep behavior of active rock glaciers in the European Alps [3,[18][19][20].…”

PYRENAIC ROCK GLACIERS: AN AIRBORNE AND MULTITEMPORAL LiDAR MONITORING CASE STUDY IN THE BESIBERRI AREA

“…Additionally, these type of Pyrenaic rock glaciers, located close to the 0 o C isotherm, are suitable for being very interesting natural 'sensors' for climatic change. Especially considering that the increase of velocity of rock glaciers in recent years have also been documented in the Alps (Bodin et al, 2018) and Northern Norway (Eriksen et al, 2018). Also, the fact that the multitemporal dataset used in this study is open access, easily available and will soon be covering all the Spanish mountain ranges, it can be widely used for assessing all the rock glaciers and understanding how they are responding to climate change in these past 5 years.…”

Evaluating the destabilization susceptibility of active rock glaciers in the French Alps

“…In this context, rock glaciers experiencing destabilization have recently become of interest. While active rock glaciers commonly present moderate interannual velocity variations that correlate with the ground temperature (Delaloye et al, 2008;Kellerer-Pirklbauer and Kaufmann, 2012; Evaluating the destabilization susceptibility of active rock glaciers 2009), destabilized rock glaciers are characterized by a significant acceleration that can bring the landform, or a part of it, to abnormally high velocities (Delaloye et al, 2013;Roer et al, 2008;Scotti et al, 2016;Lambiel, 2011;Eriksen et al, 2018). During this acceleration phase, morphological features typical of sliding processes, such as crevasses and scarps, appear and grow on the rock glacier surface.…”