Increasing glacier end-of-summer snowline altitudes in the trans-Himalayan region of Ladakh

This work presents a spatiotemporal analysis of 5729 individual end-of-summer snowline altitude (SLA) observations. These data points were derived from manual mapping of 2257 glaciers across four periods (1977, 1994, 2009, and 2019) in the trans-Himalayan region of Ladakh. The study shows that snowline altitudes (SLAs) have risen on over 85% of glaciers investigated. The average SLA changed from a slight decrease of −0.93 m a⁻¹ between 1977 and 1994 to an increase of +8.47 m a⁻¹ between 2009 and 2019. Rising SLAs were accompanied by a 0.03°C a−1 increase in regional mean annual air temperature between 1979 and 2019. Spatial variability in the rate of SLA change from basin to basin suggests that the sensitivity of glacier SLAs to the general rise in temperature is modulated by other climate factors, such as proportions of solid vs. liquid precipitation. Our analysis reveals that in the Suru and Zanskar basins, the regional mean SLA has risen to a level that now exceeds the maximum elevation of approximately 15% of the investigated glaciers. In these cases, the snowline has overshot glacier highest elevations by up to 350 m, effectively eliminating their accumulation zones. Thus, these ice masses have a negative mass balance and, no longer sustainable under current climatic conditions, will disappear.