| Glaciers flow velocity is an important parameter for the study of glacier dynamics, mass balance and climate change, and can provide precursory warning of glacier melting induced flooding, debris flowing, etc. As an advanced technique for spatial information acquisition, Synthetic Aperture Radar can monitor the ground surface motion with high precision under all weather. The unique advantages indicate that SAR is the optimum method for glacier monitoring.This study is focused on the approach of glacier motion monitoring using D-InSAR and Offset-Tracking technology. Aiming at meeting the demand of strong noise suppression for mountain glacier interferograms, a new two-step filter is developed. High spatial and temporal displacement fields of the Tuomuer mountain glaciers are acquired by applying the D-InSAR and Offset-Tracking technology to ERS and PALSAR image pairs respectively. Basing on these displacement fields, we sort out the natural events which affect the result, and analyze the mechanism of mountain glaciers’motion, and conclude the stability of glaciers in Tuomuer mountain. The main innovations and discovers include:1) A new two-step filter integrating the Contoured Median and Goldstein filter is developed. The new filter inherits the good edge preservation characteristics of the Contoured window filter and the strong smoothing capability of the Goldstein filter. In addition, it introduces the pseudo-coherence of interferogram to improve the adaptiveness of the Goldstein filter. Experimental results show that the proposed filter performs quite well not only in noise reduction, but also in detail preservation. Moreover, it can partially recover continuous interferometric fringes from area nearly without signals.2) We discover that the altitudes of the velocity peaks are close to the recorded snowlines, which indicates that detecting the changes of velocity peaks’position might provide a reference for monitoring the changes of the snowlines. The snowline changes are important parameter for estimating the accumulation area ratio (AAR) variations of the glacier, which can inverse quantitative mass balance changes. So this work is significative for mass balance study.3) The debris coverage of’Tuomuer style’Glacier and temporal continuity of SAR images make the D-InSAR and Offset-tracking successfully acquire continuous surface displacements. Several natural events such as snowfall in the firn basins, ablation of superimposed ice and development of crevasses in steep sections still have some influence on the results.4) The following rules of the Tuomuer-Khan Tengri Mountain Range Glacier’s motion are revealed:the velocity reduces from glacier axis to both sides, and increases from its origin to snowline and then reduces towards the end; the velocity is positively nonlinear correlated with the slope, especially when the slope increase sharply from3°to16°, the surge velocity will give rise to crevasses on the glacier; under the influence of glacial lake level changes, the velocity of tributary at the tail can surge to96cm/day; the summer velocity can be as high as two times of winter one; the normal velocity of the glacier trunk is between20and50cm/day, but can reach170cm/day in special place.5) The velocity changes among the observation years have been carefully examined. This along with the associated runoff measurements makes us conclude that the glaciers in the Tuomuer-Khan Tengri Range are in dynamic equilibrium between intensified melting and increased precipitation and glaciation, and their velocity will maintain stable in the near future. |
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