Monitoring recent variations of the surface displacements of eight Nyainqêntanglha glaciers

Abstract. A polythermal glacier is one of the dominant types of glacier that is distributed widely in the transition zone of the monsoon and continental climates of the Tibetan Plateau. However, the study of the glacier dynamics of this type of glacier in most of the glaciated area is still limited owing to the remoteness of the mountains, and issues related to high altitude. Theoretically, the surface displacement of a polythermal glacier has strong variations both in the spatial and temporal scales. We chose eight typical polythermal type glaciers (Zhadang Glacier, Panu Glacier, Lalong Glacier, Tangse No. 2 Glacier, Xibu Glacier, Lisheng Glacier, Guila Glacier, and Guren Glacier) in the Nyainqêntanglha Mountains, the south of Nam Co Lake, Tibetan Plateau for a case study. In this study, we monitored the ice surface displacements of these glaciers for nearly two decades from 1993 to 2009 by using the feature-tracking method. The ice displacement measurements with sub-pixel accuracy were recorded over the entire areas of the Zhadang, Panu, Lalong, Tangse No. 2, Xibu, Lisheng, Guila, and Guren glaciers during this period. Through the comparison of ice surface displacements between 1993–2003 and 2003–2009, we found that the change of the displacements are observed in most areas of these studied glaciers, especially in the ablation zones. The magnitude of this change is about −51%, except in the Xibu Glacier (+24%), in terms of the average of the total displacements. The surface displacements that were extracted by spaceborne optical imagery are promising for potential detection of the mechanics of polythermal glaciers in the Nyainqêntanglha Mountains.