Monitoring glacier flow rates dynamic of Geladandong Ice Field by SAR images Interferometry and offset tracking

Geladandong Ice Field is one of the largest ice fields in central Qinghai-Tibetan Plateau, also the water source of Yangtze River, Selin Co Lake and Chibozhang Co Lake. In this study, we aim to monitor the glacier flow rates and its change in 1990s and 2000s by Differential SAR Interferometry and offset tracking. We obtained SAR images acquired by ERS-1/2 and Envisat/ASAR in 1990s and 2000s then processed them with offset-tracking method, also validated with D-InSAR method. The result indicates that most glaciers in Geladandong Ice Fields kept stable flow rates at 15-30m/a during 1990s and 2000s. Some glaciers are identified as surge type. We selected two glaciers and studied the time series of flow velocity profiles. During the surging period, flow rate could be 3 to 10 time as normal years. These two glaciers forwarded their terminus during their surging period by Landsat optical monitoring. We concluded that during 1990s and 2000s most glaciers kept a stable flow velocity and some glacier surged during the study period therefore terminus forwarding cannot equal to mass gaining.