Multi-decadal evolution of ice-debris complexes at Muztagh Ata (Eastern Pamir) derived from Corona KH-4A and Pléiades stereo images

Abstract. Ice-debris complexes are glacial-periglacial transitional landforms including rock glaciers that provide important insights into geomorphological evolution and represent substantial yet overlooked water reservoirs. However, their formation and evolution remain poorly constrained. Here, we investigate ice-debris complexes at Muztagh Ata, Eastern Pamir, using historical Corona KH-4A stereo images acquired in 1967 and very-high-resolution Pléiades tri-stereo data acquired in 2013 and 2019 to reconstruct elevation changes over five decades and derive surface velocities for the recent period. Our results reveal a three-zone geomorphological organization comprising a glacier, a glacier-affected, and a periglacial zone. The glacier-affected zone exhibits extensive thermokarst features and substantial surface lowering, locally exceeding 100 m between 1967 and 2019, whereas the periglacial zone is dominated by rock glaciers with maximum surface velocities of up to 6 m/yr. These zones occupy approximately 39.4 km², 6.5 km², and 9.4 km², respectively. Despite their considerably smaller area, the glacier-affected and periglacial zones experienced ice volume losses comparable to those of the glacier zone during 1967–2019. Our observations suggest that multiple evolutionary pathways can operate simultaneously within a single ice-debris complex. Glacier-affected landforms may progressively evolve into rock glaciers, whereas debris-covered glaciers may advance onto or become embedded within pre-existing rock glaciers. This study provides new insights into the evolution of ice-debris complexes and highlights the need to incorporate these landforms into glacier inventories and hydrological models for water resource assessments in High Mountain Asia and other mountainous regions on Earth.