Effect of topography on the changes of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains

Abstract

Topography plays an important role in determining the glacier changes. However, topography has often been oversimplified in the studies of the glacier changes. No systematic studies have been conducted to evaluate the relationship between the glacier changes and topographic features. The present study provided a detailed insight into the changes in the two branches (east branch and west branch) of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains since 1993 and systematically discussed the effect of topography on the glacier parameters. This study analyzed comprehensive recently observed data (from 1992/1993 to 2018/2019), including mass balance, ice thickness, surface elevation, ice velocity, terminus, and area, and then determined the differences in the changes of the two branches and explored the effect of topography on the glacier changes. We also applied a topographic solar radiation model to analyze the influence of topography on the incoming shortwave radiation (SW in ) across the entire glacier, focusing on the difference in the SW in between the two branches. The glacier mass balance of the east branch was more negative than that of the west branch from 1992/1993 to 2018/2019, and this was mainly attributed to the lower average altitude of the east branch. Compared with the west branch, the decrease rate of the ice velocity was lower in the east branch owing to its relatively increased slope. The narrow shape of the west branch and its southeast aspect in the earlier period resulted in a larger glacier terminus retreat of the west branch. The spatial variability of the SW in across the glacier surface became much larger as altitude increased. The SW in received by the east branch was slightly larger than that received by the west branch, and the northern aspect could receive more SW in , leading to glacier melting. In the future, the difference of the glacier changes between the two branches will continue to exist due to their topographic differences. This work is fundamental to understanding how topographic features affect the glacier changes, and provides information for building different types of relationship between the glacier area and ice volume to promote further studies on the basin-scale glacier classification.

Vegetation Dynamics and Climate from A Perspective of Lag-Effect: A Study Case in Loess Plateau, China

“…Global warming has quietly impacted the terrestrial ecosystem over the last hundred years, with a series of problems affecting the environment change such as temperature increases, glacier ablation, sea-level rise [1][2][3][4], etc. Vegetation is very important for terrestrial ecosystems and is the hub that connects the atmosphere, soil, and water [5][6][7], which is a significant part of the hydrological cycle, biochemical cycle, as well as global energy cycle [8,9].…”