Monitoring glacier variations on Geladandong mountain, central Tibetan Plateau, from 1969 to 2002 using remote-sensing and GIS technologies

Using Geographical Information System (GIS) and remote-sensing technologies, we describe quantitative measurements of glacier variations in the Geladandong mountain region of central Tibet. Data from Landsat images at three different times, 1973-76, 1992 and 2002, are compared with glacier areas digitized from a topographic map based on aerial photographs taken in 1969. We find that while some glaciers have advanced during the past 30 years, others have retreated. The area of retreat is much larger than that of advance. The total glacier area has decreased from 889 km(2) in 1969 to 847 km(2) in 2002, a reduction of almost 43 km(2) (i.e. 4.8% decrease, or an average of 1.29 km(2) a(-1)). The variation of glacier area in the Geladandong mountain region is not as large as in other regions within the Tibetan Plateau. Glacier areas decreased 4.7 km(2) (i.e. an average of 0.68 km(2) a(-1)) during 1969-76, 15.4 km(2) (0.96 km(2) a(-1)) during 1976-92, and 22.4 km(2) (2.24 km(2) a(-1)) during 1992-2002, suggesting accelerated glacier retreat in recent years. The recession rates of glacier termini also increased. It is likely that the increase in summer air temperature is the major reason for glacier shrinkage in the Geladandong mountain region.