Glacier Surface Velocity Fields and their Seasonal Variation at West Kunlun, China, Detected by ALOS/PALSAR data

Spatio-temporal distribution of glaciers in the Third Pole Environment (TPE) responds sensitively to global climate change. Moreover, meltwater from them plays a critical role for regional industries in the nearby arid areas. It is, therefore, fundamentally important to monitor their spatio-temporal changes. Nevertheless, glacier measurement data in the Tibet have been limited because of a number of logistic, political, and technical issues. We detected surface velocity fields of a number of temperate glaciers in west Kunlun, China, using pixel-offset (feature-tracking) technique based on the ALOS/PALSAR data; PALSAR is an L-band Synthetic Aperture Radar (SAR) sensor onboard ALOS (Advanced Land Observation Satellite) that was launched in January 2006 by Japan Aerospace eXploration Agency (JAXA). The data sets cover an area of ~15,000 km^2 to the north of Gozha lake in west Kunlun. While the area includes Guliya ice cap, where long-term ice-core records have been extensively examined (e.g., Thompson et al. 1997), the spatial and temporal changes in the surface velocity fields of nearby glaciers have not been reported, to our knowledge, presumably because of logistic problems. The temporal coverage is Sep. 2007 to Jan. 2010 with a nominal time interval of 46 days. At Duofeng Glacier, for instance, the maximum surface velocity is estimated to be ~30 cm per day on average from January to February, while it approaches ~50 cm per day from June to July. The maximum velocity is found at ~5500 m above sea level, which is about half of the total height range of the glacier. We also measured surface velocity fields at other valley glaciers.