Monitoring recent variations of the movements on the polythermal glaciers -a case study in the Nyainqêntanglha Mountains

The polythermal glacier is one of the dominant glaciers distributed widely in the transition zone of monsoon and continental climate, Tibetan Plateau. However, the glacier dynamics study of this type glacier is still limited in most of glaciated area due to the remote mountains, and high altitude issues. Meanwhile, the surface displacement of polythermal glacier appears strong variations both in seasonal and even shorter time-scales, based on the principles of glaciology mechanics. On one hand, this seasonal variations indicate drainage and movement of melting water between ice body and glacier bed. On the other hand, shorter variations relate to the amount of input water for this supraglacial drainage system. Here, we choose five typical polythermal type glaciers in Nyainqêntanglha Mountains, the south of Nam Co Lake, Tibetan Plateau for a case study. In this study we monitoring the ice surface displacement of these glaciers nearly two decades from 1993 to 2009 using features tracking method. Through this generation of ice motion maps, we intend to explore the association between spatial distribution of ice surface motion anomalies, and the possible patterns of ice speed variations during this period which responds to probable climate influence on surface melting.