Multi-scale remote sensing-based glacier monitoring in the Aksu-Tarim Catchment in Xinjiang/China
Final Report Abstract
Glaciers in the Aksu-Tarim Catchment are resources of fresh water and are of cardinal importance both for the ecosystem and the agriculture in the arid Tarim Basin in northwest China. Therefore knowledge about glacier characteristics and changes is highly relevant for sustainable development of this region. Within this project for the first time a consistent glacier inventory for the entire Aksu-Tarim Catchment and other parts of central Tien Shan was generated using satellite imagery. The overall glacier area in the year ~2008 was about 6350 km^2. This inventory was also an important contribution to the first globally complete glacier inventory which is frequently used by many studies. Declassified stereo imagery from US spy satellite missions such as Corona and Hexagon are suitable sources of information from the 1960s and 1970s. However, the image geometries are complex and low contrast over snow and in dark shadow hampers the generation of suitable DEMs in these areas. In this project, algorithms for data pre- and postprocessing were developed to minimize distortions of the images and eliminate outliers of the generated DEMs in order to obtain the best possible results. Using this imagery it could be determined that glaciers lost an area of about 250 km² or about 0.11% per year between 1975 and 2008. The investigated glaciers showed predominant downwasting in the ~1975–1999 period with an average thickness decrease of slightly more than 10 m resulting in an average mass loss of about 0.35 m w.e. a^−1 (w.e.= water equivalent). The highest mass loss could be observed for the western and northern catchments. Detailed investigations of the area south of the highest peak of Tien Shan revealed slightly less mass loss in the period before ~2000 (1976–1999: −0.42±0.23 m w.e.a^−1), than thereafter (1999–2009: −0.23±0.19 m w.e.a^−1). Further important findings are that (a) glacier mass loss accounted for about 20% of the runoff of Asku River and (b) that although glacier area loss was relatively low the mass loss is similar to the global average. A reason for this is that many of the large glaciers are heavily covered by supraglacial debris which have stagnant termini, did not or only little retreat but were significantly downwasting. During the investigation of glacier changes several indications for past and present glacier surges (rapid glacier advances) were found and it was decided to investigate this phenomenon more in detail. Overall 39 possible surge-type glaciers were identified. The largest surge events were observed in Central Tien Shan where two glaciers advanced several kilometres. A further important finding was the occurrence of large amount of subsurface ice, identified in the field using geophysical investigations and by remote sensing remote sensing techniques. Of specific hydrological importance is debris-covered dead ice which showed significant surface lowering indicating ice melt. The achieved project data and results are of high value for modelling of current and future the response of glaciers to climate and their hydrological importance. Several studies already utilised the data and could confirm the high importance of glacier melt for runoff. The runoff is projected to further increase within the next decades until a tipping point is reached and the runoff will start to decline with continued glacier shrinkage. It should finally also be noted that the PI became a well-recognised researcher and frequently asked glacier expert during the project period as indicated by several contributions to newpaper articles (e.g. in Berliner Tagessspiegel, Die Welt, Züricher Tagesanzeiger) and radio interviews (e.g. Deutschlandfunk).
Publications
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(2012): Climate change impacts on glaciers and runoff in Central Asia. Nature Climate Change 2: 725-731
Sorg, A., Bolch, T., Stoffel, M., Solomina, O., Beniston, M.
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(2013): Glaciers characteristics and changes in the Sary-Jaz River Basin (Central Tien Shan) 1990-2010. Remote Sensing Letters 4(8): 725–734
Osmonov, A., Bolch, T., Xi, C., Kurban, A., Guo, W.
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(2013): Heterogeneous mass loss of glaciers in the Aksu-Tarim Catchment (Central Tien Shan) revealed by 1976 KH-9 Hexagon and 2009 SPOT-5 stereo imagery. Remote Sensing of Environment 130: 233-244
Pieczonka, T., Bolch, T., Wei, J., Liu, S.
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(2014): Untersuchung und Visualisierung von Gletschergeschwindigkeiten im Zentralen Tien Shan auf Basis von optischen Satelliten-Fernerkundungsdaten. DGPF Tagungsband 23/2014: pp. 8
Kröhnert, M., Pieczonka, T., Bolch, T., Buchroihtner, M.
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(2015): Glacier area and mass changes since 1964 in the Ala Archa Valley, Kyrgyz Ala-Too, northern Tien Shan. Лёд и Снег (Ice and Snow) 55(1): 28-39
Bolch, T.
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(2015): Mass changes of Southern and Northern Inylchek Glacier, Central Tian Shan, Kyrgyzstan, during ∼1975 and 2007 derived from remote sensing data, The Cryosphere 9: 703-717
Shangguan, D. H., Bolch, T., Ding, Y. J., Kröhnert, M., Pieczonka, T., Wetzel, H. U., Liu, S. Y.
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(2015): Region-wide glacier mass budgets and area changes for the Central Tien Shan between ~1975 and 1999 using Hexagon KH-9 imagery. Global and Planetary Change, 128: 1-13
Pieczonka, T., Bolch, T.
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(2015): Strong glacier mass loss in the Tien Shan over the past 50 years. Nature Geoscience
Farinotti, D., Longuevergne, L., Moholdt, G., Düthmann, D., Mölg, T., Bolch, T., Vorogushyn, S., Güntner, A.
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(2016): Knowledge about glacier mass changes in High Asia significantly improved due to TUD-IfK research, Kartographische Bausteine 40 (= Vom Gelände zur Karte … Festschrift anlässlich des 65. Geburstages von Prof. Manfred Buchroithner) 13-24
Bolch, T., Pieczonka, T., Holzer, N., Peters, J., Mukherjee, K., Bhattacharya, A.
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(2016): Less Water from the Mountains? Consequences of Glacier Changes in Central Asia. In: Freedman, E., Neuzil, M. (Eds.) Environmental Crises in Central Asia: From Steppes to Seas, from Deserts to Glaciers. Routledge, 13-24
Hagg, W., Bolch, T.
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(2017): Glacier мass loss during the 1960s and 1970s in the Ak-Shirak range (Kyrgyzstan) from multiple stereoscopic Corona and Hexagon imagery. Remote Sensing 9(275): pp. 18
Goerlich, F., Bolch, T., Mukherjee, K., Pieczonka, T.
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(2017): Surge-type glaciers in the Tien Shan (Central Asia). Arctic, Antarctic and Alpine Research 49(1): 147–171
Mukherjee, K., Bolch, T., Goerlich, F., Kutuzov, S., Osmonov, A., Pieczonka, T., Shesterova, I.
