Science Service System

Summary of Proposal MTH2974

TitleDerive the precise 3D motion field of mountain glaciers and build the functional model between motion changes and mass balance
Investigator Jia, Li - Central South University, School of Geoscience and Info-Physics
Team Member
Prof. Xiaoli, Ding - Hong Kong Polytechnic University, Department of Land Surveying and Geo-Informatics
Dr. Lei, Zhang - Hong Kong Polytechnic University, Department of Land Surveying and Geo-Informatics
Prof. Zhiwei, Li - School of Geosciences and Info-Physics, Central South University, Department of Geomatics
SummaryAlong with the global climate warming, the interest in the dynamics of high mountain glacier has greatly increased due to the observations of the accelerated mass loss of mountain glaciers since 1980.Several indexes have been adopted to represent or measure glacier massbalance changes, such as glacier thickness, area coverage, terminus position,equilibrium line latitude, accumulation area ratio, ablation degree day factorand runoff. However,one index, the glacier motion, which is closely correlated with the massbalance, has not been given sufficient emphasis due to lack of efficient spatial mapping technique. For glaciers, mobility is one of their essential characters. It is glacier motion that controls the balance of mass flux between accumulation and ablation zone, and determines the glacierís geometry andextent directly. A glacier flows at a balance velocity, when its driving and resisting forces are in equilibrium. The driving forces are the stresses generated as a result of gravity that is factored by the glacier mass and bed slope. Since in general glaciers have already adjusted their bed slope to produce sufficient stresses to maintain the balance velocity, glaciersí mass become the major determinant of driving forces. Significant deviations from the balance velocity are likely to be a result of losing balance between driving and resisting forces. However, for land terminatedmountain glacier the mass loss is mainly in the form of shrinking ordown-wasting (stationary thinning). Therefore, it is difficult to derive exact mass balance changes from motion measurements. However, since on land thevariation of flow driving force is more likely to occur than that of the resisting force, precise knowledge of glacier motion can still provide critical information on mountain glacierís dynamics in response to climate change. At present, a wide range of researches on mountain glacier motion have been conducted. However, apart from presenting the knowledge of glacier flow speed and mechanisms, the previous researches have never deduced quantitative glacier mass changes information from the glacier motions, i.e. the significance ofglacier motion measurement has not been fulfilled yet. Relative to the mountain glacier velocity measurement, the thickness change measurement can directly tell the quantitative mass change information. However, the conduction of representative thickness change measurement is often hindered by the paucity ofsuitable images.Despite the DLR has initiated a mission (TanDEM-X) which aims at acquiring the globalDEM using a cutting-edge technique, Bistatic InSAR, the data collection lastfor about 3 years, 2011-2014. The time sampling for glacier changes monitoring is still limited in the past and near future. By contrast, the SAR image pairs suitable for monitoring the glacier motion, i.e. the normal repeat track monostatic image pairs, are numerous. Regarding this situation, we will first derive the precise 3D motion field from multi-temporal TerraSAR-X image using MAI,MT-InSAR and Offset-Tracking. Meanwhile, the same period glacier mass changes will be derived by geodetic method. Basing on the two dataset, we build the mathematic relationship between the glacier motion changes and mass changes and examine the model on new mountain glaciers of the same thermal type. The time sampling of glacier mass change study would be much more flexible. In this way the mountain glacier motion monitoring have chance to exert more value. About 150 TerraSAR-X images will be required and the deliverables of this project may include several journal papers and some algorithms on the integration of multi-track and multi-temporal InSAR observations. The research is funded by the National Science Foundations of China(No. 41474007, Jan 2015~Dec 2018).

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