Deciphering transitions within ice–debris complexes in the Northern Tien Shan through surface characteristics and internal structure

Ella Wood, Tobias Bolch, Vassiliy Kapitsa, Francesca Baldacchino, Viktor Blagovechshenskiy, Foteh Rahimov, Alibek Taskynbayev, Lothar Schrott

2026

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DOI 10.1002/esp.70309
Data confidence 70 medium
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Abstract

Abstract Rock glaciers situated within interconnected complexes of glaciers, moraines and glacier forefields are common in the Tien Shan. This study investigates four rock glaciers within ice–debris complexes in the Ulken Almaty valley, northern Tien Shan, Kazakhstan, through the integration of geophysical data on internal structure and remotely sensed surface velocities. Combined ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) surveys were conducted on the larger Morennyi and Gorodetsky complexes, with GPR profiles on further two rock glaciers. Geophysical analyses identified a heterogeneous internal structure, with ice content and structural features varying across morphological units. We characterised the geomorphic units within the two larger complexes, delineating an upper glacially dominated zone and a lower periglacially dominated rock glacier zone. Buried glacial ice bodies were present within the upper rock glacier zone on both the Morennyi and Gorodetsky complexes, likely deposited during advances of the upslope glaciers. These ice bodies were identified through high ERT resistivities of ~7 MΩm and supported by structural reflections within the GPR radargrams. Surface velocities increased in both magnitude and coherence across the transition between the glacial and periglacial zones, reflecting changes in internal structure and surface morphology. We also emphasise the importance of debris availability and connectivity in the development and flow activity of individual units. Understanding the interplay between the glacial and periglacial components of these systems is essential when considering their hydrological and geomorphic role.