Response of glacial lakes to glacier and climate changes in the western Nyainqentanglha range.

The western Nyainqentanglha (WNT) range, located in the transition zone between large-scale atmospheric circulations, has an abundance of glacial lakes and glaciers. In the warmer climate of recent decades, the glacial lakes and glaciers in the WNT range could have changed substantially. Here, glacial lake and glacier changes for the entire WNT range between 1976 and 2018 are examined. The results show that, between 1976 and 2018, the number of glacial lakes (>0.0036 km) increased by 56% from 192 to 299 and their total area increased by 35% from 6.75 ± 0.13 km to 9.12 ± 0.13 km. The glacial lakes expanded faster in 2001-2018 (0.08 km/yr) than in 1976-2001 (0.04 km/yr), and faster on the southern side of the mountain range than on the northern side. Correspondingly, the rates of glacier area shrinkage and surface elevation thinning between 2000 and 2018 were -4.15 km/yr and -0.29 ± 0.06 m/yr, respectively, greater than the respective rates of -3.91 km/yr and -0.24 ± 0.11 m/yr in 1976-2000. The glacier retreat and elevation thinning to the south of the main divide are greater than to the north, with the exception of the thinning rate in 2000-2014 which is possibly due to precipitation differences. With the rapid retreat of glaciers, many glacial lakes are changing from proglacial lakes to unconnected glacial lakes. The increases in the number and area of glacial lakes are moving toward higher elevations, accompanying the retreat of glaciers and the increase in the mean elevation of glaciers. The observed increased precipitation also supports the increases of glacial lakes. The accelerating glacier loss and lake expansion in the WNT range imply a strong impact of climate change on the cryosphere over the past few decades.