The State of the Central Asian Cryosphere

Abstract Climate-induced changes in the cryosphere are substantial in Central Asia’s mountain regions. However, some major processes are still poorly understood, which is of fundamental importance as millions of people downstream and the whole ecosystem depend on the cryosphere’s water. The major mountain regions of Central Asia, the Tien Shan and the Pamir, exhibit diverse topographic and climatological settings resulting in a complex cryospheric response to climate change, reflected in different river runoff regimes and geohazard potential. Recent studies have documented significant shifts in the timing and magnitude of snowmelt in Central Asia during the last decades. Earlier snowmelt has become increasingly common due to rising temperatures. Looking ahead, snowmelt supply is expected to decrease sharply, with substantial variation across different river basins depending on climate change trajectories and emission scenarios. According to new regional-scale results based on the Global Glacier Evolution Model, the glaciers of Central Asia exhibit heterogeneous responses to climate change that reflect the diverse climatological and topographic setting. A decrease in glacier area and volume is prevailing. Over the rest of the 21st century, glaciers are expected to continue their decay, losing 58–85% of their present volume by 2100, depending on the climate scenario. In the Pamir, the highest and thickest glaciers are likely to survive the century, many regions in the Tien Shan and lower elevation basins will however experience pronounced ice volume reduction. The few available monitoring sites suggest rapid permafrost degradation across Tien Shan and Pamir raising the likelihood of mountain hazards with far-reaching impacts on downstream communities. Even with the limited observations, there is already evidence that thermally induced slope instabilities are increasing. Streamflow in Central Asia is primarily influenced by meltwater from both glaciers and seasonal snow, with snowmelt dominating runoff until early to mid-summer when glacier runoff becomes more significant. Our glacier model results indicate that annual runoff is expected to peak sooner in the Tien Shan catchments, while in the Pamir, peak annual streamflow will occur most likely towards the end of the century. In conclusion, water resources in Central Asia are affected by cryospheric degradation under ongoing climate change, and sustainable adaptation and mitigation strategies are urgently needed to protect the region’s livelihoods and ecosystems.

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