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Conference Agenda

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Session Overview
Session
C2: ID.10302 Himalayan Glacier Dynamics
Time:
Tuesday, 05/Jul/2016:
9:00am - 10:00am

Session Chair: Noel Gourmelen
Session Chair: Hui Lin
Workshop: Hydrology & Cryosphere
Location: Building 7-220#, School of Resources and Environmental Science, Wuhan University

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Presentations
Oral presentation

Climatic glaciers slowdown in the Pamir-Karakoram-Himalaya region

Noel Gourmelen1, Amaury Dehecq1, Emmanuel Trouve2

1University of Edinburgh, United Kingdom; 2LISTIC, Annecy, FR;

Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a contrasted picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. Several studies based on field measurements or remote sensing have shown a dominant slow-down of mountain glaciers globally in response to these changes. But they are restricted to a few glaciers or small regions and none has analysed the dynamic response of glaciers to climate changes at regional scales.

Here we present a region-wide analysis of annual glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 4 m/yr. The change in velocities over the last 25 years is analysed with reference to regional glacier mass balance and topographic characteristics. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more complex patterns consisting of mixed acceleration and decrease of ice velocity in regions that are known to be affected by stable mass balance and surge-like behavior.

Gourmelen-Climatic glaciers slowdown in the Pamir-Karakoram-Himalaya region_Cn_version.pdf

Oral presentation

Glacier Area And Mass Changes In The Eastern Pamir Plateau, China Since The Early 1960s As Derived From Remote Sensing Data

Shiyin Liu1, Zhen Zhang2, Zongli Jiang3, Junfeng Wei4, Tobias Bolch5, Donghui Shangguan6, Junli Xu7, Wanqin Guo8, Weijia Bao9

1Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of; 2Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of; 3School of Architecture and Urban Planning, Hunan University of Science and Technology, Xiangtan, Hunan, China; 4School of Architecture and Urban Planning, Hunan University of Science and Technology, Xiangtan, Hunan, China; 5Geographisches Institut, Universitat Zurich, Switzerland; 6Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of; 7Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of; 8Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of; 9Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, China, China, People's Republic of;

The eastern Pamir Plateau with an average elevation of about 4000 m above sea level is an important glacierized area in western China. Glaciers in the eastern Pamir Plateau are primary water source of tributaries of the arid endorheic Tarim River Basin which is key to the local social and economic activities at downstream area. There are 1265 glaciers in the region with a total area of 2054.0±75.9 km2, around one-sixth of the total glacier area of the whole Pamir Plateau. To derive glacier outlines in different years and to compile glacier inventories of the region, we have used topographical maps based on aerial photogrammetry (1960~1965, 1971/76), Landsat MSS(1972)/ETM+(2009) images. We also used EOS TERRA ASTER ((2013/14)) archives, Shuttle Radar Terrain Mission(SRTM), Cartosat-1(2014) to generate volume change of glaciers by differencing multi-temporal digital elevation models (DEM), and with Sentinel-1 SAR (10/2014~6/2015) and ALOS/PALSAR (2~4/2008) and Landsat /OLI (10/2013~7/2015) to generate surface velocity field of some glaciers especially the changing processes of a surging glacier on the north slope of Mount Kongur Tagh. Our results indicated that glaciers in the region have been retreating by 10.8±1.1% of the total area in 1963, or -0.2±0.0% annually, though 14 glaciers have been found advancing and one surging in 2015. The pattern of glacier area change was like that found for glaciers in other regions. Small glaciers displayed in larger retreat rate, i.e., glaciers of 0.1–0.5 km2 in area lost their area by 21.6%±2.0% while it was -4.8%±0.4%l for glaciers >10 km2. Meanwhile, almost half of the area decrease (49.8%) came from glaciers in the 1–5 km2 range, which lost 123.8±12.1 km2. The largest retreat has been found for Glacier 5Y663L0023 with a speed at -48.9±3.12 m/a and the largest advance for Glacier 5Y663L0023 by +99.2±3.12 m/a during 2001 and 2009. The surge of a tributary of Karayaylak Glacier happened in 2015 without changing its total area.

Based on DEM differencing for glaciers with 1018.3 ± 12.99 km2 in area in the Muztag Ata and Kongur Tagh (MAKT) region from maps (1971/1976), SRTM (2000), ASTER (2013/14) and Cartosat-1 (2014) demonstrated that these glaciers have experienced an overall volume loss of –6.99 ± 0.80 km3 in ice volume equivalent to –0.15 ± 0.12 m/a water (w.e.) from 1971/76 to 2013/14 while their total area have shrunk by 1.9 ± 0.2%. The mass wastage speed was quicker at a rate of 0.19 ± 0.19 m w.e./a for the period ~1971/76–1999 than that by 0.14 ± 0.24m w.e./a during 1999–2013/2014. The period of 2009~2014 have even seen a slight expansion of glaciers in the study area.

Surging of glaciers in eastern Pamir has not ever been reported in literatures. Thanks to the locals reports and the available satellite images/SAR data archives, the surge of the western branch of Karayaylak Glacier happened during the early summer of 2015 as indicated by changes in surface velocity and elevation. The surface velocity was accelerated up to 20.40±0.42m/d during May 8 and May 15, 2015. The thinning was measured by 47.82±0.70m with maximum of 178.38±0.70m in the reservoir area and thickening by a maximum of 130.58±0.70 in the receiving area converging to the main trunk of the Karayaylak Glacier.

In summary, glaciers in the eastern Pamir Plateau have been retreating since the early 1960s displayed as area reduction and mass loss, however, advancing or even surging were observed for some glaciers in the region under a climate warming background.

Liu-Glacier Area And Mass Changes In The Eastern Pamir Plateau, China Since The Early 1960s As Derived_Cn_version.pdf

Oral presentation

Variation of Glacier Surface Velocities in the Tuomuer Region, Central Tien Shan, using Microwave and Optical Satellite Data

Zongli Jiang1, Shiyin Liu2, Tobias Bolch3, Melanie Kröhnert4

1HNUST, China, People's Republic of; 2CAREERI, China, People's Republic of; 3Technische Universität Dresden, Dresden, Germany; 4Technische Universität Dresden, Dresden, Germany;

We used both microwave (ENVISAT/ASAR, ERS, ALOS/PALSAR and Sentinel-1A) and optical (Landsat and ASTER) data to retrieve glaciers surface velocities in Central Tien Shan Mountains based on feature/speckle tracking methods. Debris-covered Koxkar, Tuomuer, North and South Inylchek glaciers were chosen as the case study for which time series of surface velocities were retrieved to compare with field measurements to validate the reliability and suitability of the method. The accuracy of the measurements was discussed and the results were compared to the results obtained by optical data. The dynamics of these glaciers were evaluated using coherence of interferometric SAR in the same time. In general, the results of the different data showed good agreements and shed light on the similarities and differences in glacier dynamics. All glaciers have annual velocities of more than 50m/a in the upper part of their tongues and low flow velocity with probably stagnant part at the termini. North Inylchek Glacier average surface velocity is lower than South Inylchek Glacier where large parts of the tongue flow faster than 100m/a. Tuomuer glacier is heavily debris-covered glacier and nourished by several tributaries. The trunk of the glacier shows slowly flow while tributaries flow relatively fast. A speed-up event at one tributary indicates probably a surge. Koxkar Glacier is also heavily debris-covered, the surface velocity is relative slower with large parts having very slow velocity or even being stagnant. Comparisons of multi-temporal data indicate slightly lower flow around 2010 than around 2002.

Jiang-Variation of Glacier Surface Velocities in the Tuomuer Region, Central Tien Shan, using Microwave and_Cn_version.pdf
Jiang-Variation of Glacier Surface Velocities in the Tuomuer Region, Central Tien Shan, using Microwave and_ppt_present.pdf

Poster

Investigating The Use Of Regular And Swath Processed CryoSat Elevations For Retrieving Glacier Topography Over The Himalayas

Luca Foresta, Noel Gourmelen

School of GeoSciences, University of Edinburgh, United Kingdom;

Reference and repeat-observations of Glacier topography are critical to identify changes in ice thickness, provide estimates of mass gain or loss and quantify sea level change contribution. The lack of such sustained observations was already identified in the Integrated Global Observing Strategy (IGOS) Cryosphere Theme Report as a major shortcoming. Glaciers’ and ice caps thinning and retreat accounts for about half of the total ice loss from the Cryopshere [1]. This includes glaciers of the Himalayan range, where changes in mass balance have an important impact on environment as well as human society. Here we restrict our focus to selected regions of the Himalayas, which is part of the Dragon 3 study areas.

Observations of glaciers mass change at the global scale are limited, conventional altimetry measurements over Mountain Glaciers are sparse and characterized by relatively large errors. The ESA Altimetry mission CryoSat aims at gaining better insight into the evolution of the Cryosphere. CryoSat’s revolutionary design features a Synthetic Interferometric Radar Altimeter (SIRAL), with two antennas for interferometry. The corresponding SAR Interferometer (SARIn) mode of operation increases spatial resolution while resolving the angular origin of off-nadir echoes occurring over sloping terrain. The SARIn mode is activated over Mountain Glaciers providing the elevation for the Point Of Closest Approach (POCA) as a standard product.
Preliminary evaluation of CryoSat L2 elevation products over the Karakoram range show potential while noticing limitation related to the alpha-beta tracker [2].

In this study, we expand on the work of [2] by (i) extending the analysis of the alpha-beta tracker to the entire Himalaya Mountain chain, (ii) evaluating the quality of the L2 elevation product, (iii) processing CS intermediate data (L1b) into swath elevation. Swath elevations are obtained using a novel algorithm which exploits the full waveform of CS-SARIn mode takes when both signal and surface characteristics are favourable. Such technique has been used to produce measurements of ice elevation beyond the POCA [3-5]. The corresponding product, labelled L2Swath as opposed to regular ESA CS L2 elevation data, generally produces ice topography data with 10-100 fold finer resolution than L2 [3] and has the potential of providing ice elevation data over complex mountainous terrain. We present CryoSat-derived elevation over the Pamir, Karakoram and Everest regions, and examine the performance of the new algorithm by comparing the obtained elevation with high resolution DEMs derived from the SPOT-5 and Pleiades sensors. We find that the onboard-retracker design leads to observation of high elevation sections of the glaciers at the expense of the valley glaciers; swath processing of CryoSat provides an order of magnitude more elevations than standard POCA over the Himalayas region; the bias between CryoSat derived elevations and the validation dataset is in the range of [1-20] meters, some of which can be explained by the time difference between the datasets.

References :

[1] Vaughan, D.G., J.C. Comiso, I. Allison, J. Carrasco, G. Kaser, R. Kwok, P. Mote, T. Murray, F. Paul, J. Ren, E. Rignot,O. Solomina, K. Steffen and T. Zhang, 2013: Observations: Cryosphere. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

[2] Dehecq A., Gourmelen N., Shepherd A., Trouve E., Wingham D. Evaluation of Cryosat-2 for height retrieval over the Himalayan range, Proceeding, CryoSat-2 third user workshop, Mar 2013, Dresden, Germany.

[3] ESA STSE CryoTop project - http://www.stse-cryotop.org/

[4] Gray L., Burgess D., Copland L., Cullen R., Galin N., Hawley R. and Helm V. Interferometric swath processing of Cryosat data for glacial ice topography. The Cryosphere, 7(6):1857-1867, December 2013.

[5] Hawley R.L., Shepherd A., Cullen R., Helm V. and WIngham D.J. Ice-sheet elevations from across-track processing of airborne interferometric radar altimetry. Geophysical Research Letters, 36(22):L22501, November 2009.



 
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