The Himalaya and Karakoram (H–K) mountain ranges are home to over 32,000 glaciers that, together, contain almost half of the total volume of ice in a geographical region called “high-mountain Asia.” These gigantic ice masses of the high-mountain Asia are crucial to support ecosystems, regulate climate, and modulate the flow of rivers—impacting the lives of about 2 billion people  downstream. Unfortunately, due to global warming, the beneficial effects of these glaciers are gradually melting away and being replaced by hazards and natural disasters such as floods and droughts.

 

After decades of research, scientists have gathered abundant data to gain a solid understanding of how the H–K glaciers have been changing and of the many natural processes influenced by them. Although most glaciers in high-mountain Asia are on the decline, the changes they suffer and their effects on the landscape are far from simple and homogeneous. As such, it is important that we get a clear picture of what’s going on in this region to know what to look out for in the future, as well as make plans to mitigate the changing environment as much as possible.

 

To address this challenge, an international team of scientists, including Yong Nie and Prof. Xiaoqing Chen of the Chinese Academy of Sciences, recently wrote a comprehensive review about glacial changes and hydrological impacts in the H–K region. This review, which was published in Nature Reviews (Earth and Environment), first discusses observed changes in H–K glaciers, their causes, and the most likely future trends, with a focus on their hydrological impact on rivers and glacial lakes. Then, the researchers explain the far-reaching consequences of these glacial changes on societies and human activities. Finally, they touch upon what we can do to handle what’s coming. 

 

The shrinking of glaciers due to climate change has been most notable in the Himalaya region, where ice loss has been markedly accelerating since at least 1975. In stark contrast, the Karakoram glaciers have remained relatively stable, with some of them even growing larger since 2000. This bizarre phenomenon is known as the Karakoram anomaly: the glaciers in this region have struck a balance between ice ablation and ice accumulation due to a fortuitous combination of meteorological effects. Overall, however, the future doesn’t look very optimistic  for H–K glaciers, which are expected to continuously and consistently shrink by the end of the century under various climate change scenarios. 

 

Such melting would come at a great price for anyone living or working alongside rivers fed by H–K glaciers. Scientists predict that, at first, rivers will be generally more prone to flooding due to changes in runoff components. Glacial-lake outburst floods, an especially dangerous type of floods that can cause severe disasters, will likely become more frequent. Moreover, the modulating effect of glaciers on streamflow probably decreases, leaving them more dependent on rainfall and at the mercy of droughts during extended periods of scarce rain. “All these changes could negatively impact downstream populations and infrastructure, including the thriving hydropower sector and some of the world’s largest irrigated agriculture systems, by making water flow more extreme and unpredictable,” warns  Dr. Chen . 

 

The authors further explain how we can prepare to face a potentially bleak future. They emphasize the importance of additional research to gain a better understanding on glacial processes and their effects downstream. Installing weather stations, river-flow gauges, and glacial monitoring systems, as well as conducting more field surveys, could be a solid first step. Moreover, the researchers explain that international cooperation between Asian countries in the H–K region will be essential to establish hazard-warning systems and, perhaps most importantly, reduce greenhouse gas emissions. “Our review highlights the dangers to these nations that will come from continued loss of the H-K glaciers, and, therefore, the tremendous economic and social benefits to be gained from mitigating climate change by lowering emissions ,” remarks  Dr. Nie.

 

About Professor Xiaoqing Chen

Xiaoqing Chen is a Professor at Chinese Academy of Sciences, Chengdu, China, and is the corresponding author of this study. He has more than 50 research publications to his credit.

 

Editor's note: The study was supported by STEP,a TPE related science project.