Glacier Changes and Their Linkage to the Climate-Topographic Context in the Borohoro Mountains, Tian Shan 1977-2018

Against the backdrop of climate change and socio-ecological sustainability, studying glacier changes provides essential knowledge to the basic water needs and security for regions and populations under such threats, such as Central Asia. Little attention has focused on glaciers in the northern periphery of the Chinese Tian Shan. This study aims to map a recent glacier inventory and examine the glacier area shrinkage and surface elevation change for the central massif of the Borohoro Mountains in the past 41 years. Using declassified Hexagon images (1977), Landsat 5 TM (1994 and 2007), Sentinel 2A (2018) and altimetry data from the Ice, Cloud and Land Elevation Satellite (ICESat) over 2003-2009 with the 30-m Shuttle Radar Topography Mission (SRTM) digital elevation model, multi-temporal glacier fluctuations and the influence of topographic and climatic factors were investigated. Results show that the glacier area decreased from 287.5 +/- 8.2 km(2) in 1977 to 215.8 +/- 4.1 km(2) in 2018, at a rate of 0.61 +/- 0.01% year(-1). Glacier disintegration has led to a gradual increase in the number of glaciers and reached 224 glaciers in 2018. The shrinkage was at the highest rate during the 1994-2007 period and the smallest during 1977-1994. Glacier size, hypsometry, and median, maximum, and range of elevation are the most significantly correlated parameters with the relative area change. The surface elevation changes from two of the largest glaciers revealed a stronger thinning on the southern slope compared to the northern slope. These observations of glacier loss are primarily driven by the marked warming trend since the 1970s and confirmed with the overall pattern of glacier retreat in the Tian Shan from previous studies.