Glacier change in China over past decades: Spatiotemporal patterns and influencing factors

China has the largest area of glaciers situated within the middle- and low-latitude areas worldwide. Rapid changes in mountain glaciers across western China in the last decades have not only affected glacial runoff and hazards but also had profound impacts on ecosystems and socioeconomic activities in the extensive cold and arid regions of Asia and even beyond. Therefore, research on glacier change is of significant importance for regional sustainability. This study re-analyzes the first and second Chinese Glacier Inventories (CGI-1 and CGI-2) and summarizes available in-situ observation-based studies on glacier mass balance and length to provide a spatially explicit and coherent national-scale assessment of glacier changes and associated influencing factors in recent decades. We connect the glaciers between CGI-1 (from the 1950s to the 1980s) and CGI-2 (from the 2000s to the 2010s) one by one to explore the area, volume, and Equilibrium Line Altitude (ELA) changes at both the individual glacier and river basin scales for the first time. The results show that the long-term area and volume changes in China's glaciers during the area-weighted average period from CGI-1 (around 1969) to CGI-2 (around 2008) were - 5.6%/decade and - 5.3%/decade, respectively, with a mean ELA change of 12.5 m/decade. Approximately 17.2% of the total number of glaciers in CGI-1 disappeared, only 5.5% of the glaciers advanced, and the majority of glaciers decreased in size during the period between CGI-1 and CGI-2, which was characterized by a shrinkage in area and volume and a rise in ELA or division into multiple branches. In-situ observation-based analysis shows that glacier length has reduced since at least the 1960s on average, and their trends have accelerated since the 1990s. The negative trend of mass balance was slightly larger than that of the reference glaciers globally during 1960-2019, while the mean mass loss in any given decade was lower than that of the global mean. The changes have different regional characteristics. Overall, the shrinkage increased from the interior to the southeast in the Tibetan Plateau and decreased from the northeast to the southwest in northern Xinjiang, including the Chinese Tien Shan Mountains. Climatic conditions, as reflected in annual mean temperature and precipitation, are the primary causes of different spatiotemporal patterns of glacier change. A significant positive correlation is observed between annual absolute area/volume changes and snowfall variations, and a significant negative correlation is found with rainfall variations, but there is no significant correlation between the indicators of air temperature and glacial changes at the river basin scale. Additionally, other local-scale factors, such as glacial morphology and topographic conditions, have exerted profound impacts on glacier retreat for individual glaciers.

Automated summary

China has the largest area of glaciers situated within the middle- and low-latitude areas worldwide. The rapid changes in mountain glaciers across western China in the last decades have affected ecosystems and socioeconomic activities. This study re-analyzes Chinese Glacier Inventories and provides a comprehensive assessment of glacier changes and associated influencing factors. The results show a significant decrease in glacier area and volume, along with a rise in Equilibrium Line Altitude. Climate conditions and regional characteristics play important roles in glacier change.