Spatiotemporal dynamic characteristics of typical temperate glaciers in China.

China's temperate glaciers have a relatively warm and humid climate and hydrothermal conditions at low latitudes. Temperate glaciers, however, have larger ablation, higher ice temperatures, relatively fast movement speeds, and a significant sliding process at the bottom. As a result, these glaciers are more significantly affected by climate change. On the basis of topographic maps, aerial photography, and Landsat OLI images, and combined with existing research results, this paper systematically analyzed the temporal and spatial dynamic characteristics of typical temperate glaciers. The results are as follows: (1) From the 1950s to the 1970s, compared with other types of glaciers, temperate glaciers showed strong retreat and ablation trends in terms of area, length, speed, and mass balance. (2) The reduction rates of glacier areas of Kangri Garpo, Dagu Snow Mountain, Yulong Snow Mountain (YSM), and Meili Snow Mountain (MSM) in China's temperate glacier areas all exceeded 38%, which was far above the national average of 18% from the 1950s to the 2010s. (3) The recent length retreat rates of Azha Glacier, Kangri Garpo, and Mingyong Glacier, MSM, Hailuogou Glacier (HG), Gongga Snow Mountain (GSM), and Baishui River Glacier No. 1 (BRGN1), YSM were above 22 m/a, which was faster than the retreat rates of other regions. (4) Consistent with glacier retreat, temperate glaciers also had a faster ice flow speed. The ice flow velocities of the BGN1, HG, Parlung River Glaciers No. 4 and 94, and Nyainqêntanglha were, respectively, 6.33-30.78 m/a, 41-205 m/a, 15.1-86.3 m/a, and 7.5-18.4 m/a, which was much faster than the velocity of other types of glaciers. (5) Mass loss of temperate glaciers was most dramatic during the observation period (1959-2015). The annual mass balance from eight typical temperate glaciers fluctuated between - 2.48 and 0.44 m w.e., and the annual average change rate of mass balance (- 0.037 m w.e./a) was much higher than that in China (- 0.015 m w.e./a, p < 0.0001) and globally (- 0.013 m w.e./a, p < 0.0001).