Trends in 20th century and recent glacier fluctuations in the Karakoram Mountains

Abstract

The article provides an overview on the trends of 20th century and recent glacier fluctuations since the end of the 19th century in the Karakoram Mountains. Recent glacier variations in the subtropical mountain range of the Karakoram Mountains were surveyed on the base of field observations carried out in the period of 1992–2006 on 57 glaciers. Historical documents, such as photographs and travel reports, as well as air and satellite images have been included in the compilation. The occurrence of ice-dammed lakes, which have mainly been formed by advances of tributary glaciers into the trunk valleys, has been used as further indicators for glacier fluctuations. Even though a considerable part of the Karakoram glaciers have shown signs of glacier retreat, most of the longer glaciers (> 45 km), such as the Baltoro and Batura glaciers, have been rather stationary in the last century. Even some of the clean glaciers, such as the Yazghil and Barpu glaciers, did not retreat significantly. Singular glacier advances and surges occurred over the entire study period, whereas the average distance of the surges has apparently become smaller over time. The glacier behaviour of the avalanche-fed glacier is highly dynamic. Geomorphological indicators, as localised glacier thickening resulting in overtopping and breakthroughs of lateral moraines, the new moraine formation and the shape of the glacier tongue has to be handled carefully for drawing conclusions on the entire mass balance of a glacier. In the whole, the dynamics of the Karakoram glaciers proves to be different from the neighbouring mountain ranges, such as the Himalayas and Tienshan, which are characterized by a dominant glacier retreat. The reasons lie in the different topographical and climatic settings. Topography is apart from the complex climatic situation one of the major controlling factors governing the individual glacier fluctuations in the Karakoram Mountains.