Occurrence, evolution and ice content of ice‐debris complexes in the Ak‐Shiirak, Central Tien Shan revealed by geophysical and remotely‐sensed investigations

Abstract

Rock glaciers and large ice‐debris complexes are common in many mountain ranges and are especially prominent in semi‐arid mountains such as the Andes or the Tien Shan. These features contain a significant amount of ice but their occurrence and evolution are not well known. Here, we present an inventory of the ice‐debris complexes for the Ak‐Shiirak, Tien Shan's second largest glacierised massif, and a holistic methodology to investigate two characteristic and large ice‐debris complexes in detail based on field investigations and remote sensing analysis using Sentinel‐1 SAR data, 1964 Corona and recent high resolution stereo images. Overall, we found 74 rock glaciers and ice‐debris complexes covering an area of 11.2 km2 (3.2% of the glacier coverage) with a mean elevation of about 3950 m asl. Most of the complexes are located south‐east of the main ridge of Ak‐Shiirak. Ground penetrating radar (GPR) measurements reveal high ice content with the occurrence of massif debris‐covered dead‐ice bodies in the parts within the Little Ice Age glacier extent. These parts showed significant surface lowering, in some places exceeding 20 m between 1964 and 2015. The periglacial parts are characterised by complex rock glaciers of different ages. These rock glaciers could be remnants of debris‐covered ice located in permafrost conditions. They show stable surface elevations with no or only very low surface movement. However, the characteristics of the fronts of most rock glacier parts indicate slight activity and elevation gains at the fronts slight advances. GPR data indicated less ice content and slanting layers which coincide with the ridges and furrows and could mainly be formed by glacier advances under permafrost conditions. Overall, the ice content is decreasing from the upper to the lower part of the ice‐debris complexes. Hence, these complexes, and especially the glacier‐affected parts, should be considered when assessing the hydrological impacts of climate change. © 2018 John Wiley & Sons, Ltd.

Ice Mass Loss in the Central Andes of Argentina Between 2000 and 2018 Derived From a New Glacier Inventory and Satellite Stereo-Imagery

“…This thinning can be observed in the three examples, although it is more remarkable in the glacier located at the Tunuyán basin ( Figure 9A). This behavior is similar to that previously observed over ice masses in the Tien Shan, were most of the surface lowering also occurred in the transitional zone or "ice-debris complexes" (Bolch et al, 2019). This last study also evidences more stable mass balance rates in areas with thick debris coverage in transition to rock glaciers.…”

Surface velocity fields of active rock glaciers and ice‐debris complexes in the Central Andes of Argentina

“…Though not explicitly citing Berthling (2011), but largely following the proposed definition, the ING allows for glacial and non‐glacial ice origin in rock glaciers, as well as a combination of both sources in single landforms, and assigns all of these landforms to the same class. In arid to semi‐arid mountain ranges, however, a clear distinction is often complicated by the juxtaposition of debris‐covered glaciers, moraine complexes and rock glaciers (Janke et al ., 2015; Monnier and Kinnard, 2015; Bolch et al ., 2019). Here we adopt the term ‘ice‐debris complex' as an umbrella for such landforms that contain elements of debris‐covered glaciers that grade into rock glaciers in their lower parts (IANIGLA, 2018d; Bolch et al ., 2019), a form frequently found in the Central Andes (Bodin et al ., 2010; Monnier and Kinnard, 2015).…”

Decoupled kinematics of two neighbouring permafrost creeping landforms in the Eastern Italian Alps

“…Composite landforms originating from the interaction of glacier remnants and permafrost (hereafter called Glacial‐Permafrost Composite Landforms – GPCL) have been recently described in many permafrost areas of the Alps, and in other regions such as the Pyrenees, South America and Asia, with several examples of rock glaciers derived from the evolution of Little Ice Age (LIA) glacial deposits or closely related to them (Lugon et al, ; Monnier et al, ; Janke et al, ; Dusik et al, ; Seppi et al, ; Monnier and Kinnard, ; Kellerer‐Pirklbauer and Kaufmann, ; Kenner, ; Bolch et al, ). In their upper part, these landforms are composed of a glacier, which is generally fed by avalanches and extensively covered by debris.…”