Four decades of glacier variations at Muztagh Ata (eastern Pamir): a multi-sensor study including Hexagon KH-9 and Pléiades data
- 1Institut für Kartographie, Technische Universität Dresden, Helmholtzstraße 10, 01069 Dresden, Germany
- 2Institut für Geographie, Friedrich-Alexander Universität Erlangen-Nürnberg, Wetterkreuz 15, 91058 Erlangen, Germany
- 3Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China
- 4Geographisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
Abstract. Previous in situ measurements have indicated a slight mass gain at Muztagh Ata in the eastern Pamir, contrary to the global trend. We extend these measurements both in space and time by using remote sensing data and present four decades of glacier variations in the entire mountain massif. Geodetic mass balances and area changes were determined at glacier scale from stereo satellite imagery and derived digital elevation models (DEMs). This includes Hexagon KH-9 (year 1973), ALOS-PRISM~(2009), Pléiades (2013) and Landsat 7 ETM+ data in conjunction with the SRTM-3 DEM (2000). In addition, surface velocities of Kekesayi Glacier, the largest glacier at Muztagh Ata, were derived from amplitude tracking of TerraSAR-X images (2011). Locally, we observed strong spatial and temporal glacier variations during the last four decades, which were, however, on average not significant for the entire massif. Some south-west-exposed glaciers fluctuated or advanced, while glaciers with other aspects rather experienced continuous shrinkage. Several glaciers such as Kekesayi indicate no measurable change at their frontal position, but clear down-wasting despite mostly thick debris coverage at low altitudes. The surface velocity of this debris-covered glacier reach up to 20 cm per day, but the lowest part of the tongue appears to be stagnant. The low velocity or even stagnancy at the tongue is likely one reason for the down-wasting. On average, the glaciers showed a small, insignificant shrinkage from 274.3 ± 10.6 km2 in 1973 to 272.7 ± 1.0 km2 in 2013 (−0.02 ± 0.1 % a−1). Average mass changes in the range of −0.03 ± 0.33 m w.e. a−1 (1973–2009) to −0.01 ± 0.30 m w.e. a−1 (1973–2013) reveal nearly balanced budgets for the last 40 years. Indications of slightly positive rates after 1999 (+0.04 ± 0.27 m w.e. a−1) are not significant, but confirmed by measurements in the field.