Investigating mountain glacier motion with the method of SAR intensity-tracking: Removal of topographic effects and analysis of the dynamic patterns

Accurate knowledge of glacier motion variations can provide critical information for assessing glacier mass balance changes. For fast-flowing high mountain glaciers, SAR Intensity-tracking may be the most appropriate technique to measure their motions. However, due to the slant range imaging mode, topographic relief can give rise to pixel disalignments in SAR image and then bring errors to SAR Intensity-tracking. As a result, the application of SAR Intensity-tracking has been limited to SAR pairs with short baselines, because the use of image pairs with long baselines would suffer significant topographic effects over mountainous regions. This paper presents an improvement to SAR Intensity-tracking by adding an explicit procedure of topographic correction. Such correction will not only significantly increase the accuracy of the SAR pairs with shorter baselines, but also allow the image pairs with longer baselines to be taken advantage of, instead of letting them to be dismissed otherwise. Using the improved SAR Intensity-tracking technique, we derive the highly precise motion variation patterns of 11 giant glaciers in Tuomuer-Khan Tengri Mountain Ranges, one of the largest glacial centers in Tien Shan. The results manifest that most glaciers there saw flow deceleration during the observation interval (6 January 2007-4 March 2011), except the Northern and Southern Inylchek Glacier. Regarding the glacier motion mechanism, ice thermal character and climate features there, we deduce that the flow acceleration and deceleration should be the sign of glacier mass gain and loss, respectively, and the sharp and slight flow decelerations should correspond to remarkable and mild mass loss, respectively. We confirm these deductions by exploring the close link between the long-term motion variations and the dynamic patterns of these glaciers. The obvious diversities of the dynamic patterns among the studied glaciers are ascribed to the discrepancies of the glaciers' location and scale. Longer observations are still needed to confirm or redefine these findings in the future though. Provided that the precipitation keeps increasing, whether the glaciers in Tuomuer-Khan Tengri Mountain Ranges will regain mass or not has not been determined yet.