Four decades of glacier variations at Muztagh Ata (eastern Pamir): a multi-sensor study including Hexagon KH-9 and Pléiades data

Abstract

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 debriscovered 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.

Reconstruction of the mass balance of Muztag Ata No. 15 glacier, eastern Pamir, and its climatic drivers

“…The most distinct feature is that a slight mass gain has occurred since 1998, but a significant mass loss occurred during 1980-1997. This trend is consistent with the net accumulation of the Kuokuosele ice core from the Muztag Ata region (Drolkar and others, 2016), and is also consistent with the conclusion of Holzer and others (2015) (Table 4). This trend is opposite to the ongoing and widespread glacier recession in the monsoon region and in some regions in the westerlies zone, such as the Tian Shan and Qilian mountains, where the glaciers have shown a stronger retreat and mass loss after the 2000s (Bolch and others, 2012;Yao and others, 2012;Zhang and others, 2012;Azam and others, 2014;Farinotti and others, 2015;Yang and others, 2016).…”

“…The Shuttle Radar Topography Mission (SRTM) with a resolution of 90 m was used to obtain geographical coordinate information, altitude, slope and aspect. Because the glacier-covered area showed almost no changes between the 1970s and 2014 (Holzer and others, 2015;Zhang and others, 2016b), the model only uses the boundary of MZ15 glacier from the Second Glacier Inventory Dataset of China (Version 1.0) ( Guo and others, 2014). Lastly, monthly geopotential height/wind fields at the 300 hPa level obtained from the National Center for the Environmental Predictions-National Center for Atmospheric Research (NCEP/NCAR) were used to analyze the relationship between glacier mass change and macroscale atmospheric circulations.…”

“…1). This region is well suited for investigating the anomalous mass-balance changes in the northwestern TP due to the low rate of mass loss indicated by in situ and geodetic measurements (Yao and others, 2012; Holzer and others, 2015;Zhang and others, 2016b). In addition, meltwater from these glaciers is important for the water supply in the downstream oases.…”

“…In addition, meltwater from these glaciers is important for the water supply in the downstream oases. The Muztag Ata region contains 128 glaciers covering a total area of more than 377 km 2 (Holzer and others, 2015; Zhang and others, 2016b). The meltwater from these glaciers forms the headwaters of the Tarim River and contributes to over 60% of the discharge of some rivers (Yang, 1991).…”

Observation-Based Estimates of Global Glacier Mass Change and Its Contribution to Sea-Level Change

“…acceleration of rates. This has mostly been done with time series of area changes (e.g., Paul et al 2004b;Klein and Kincaid 2006;Narama et al 2010;Tennant et al 2012;Falaschi et al 2013) but also with changes in velocity (Heid and Kääb 2012;Quincey et al 2015) or elevation (Holzer et al 2015). A trend in any of these parameters is most useful for the determination of climate change impacts (e.g., an increase of mass loss or area shrinkage rates through time).…”