Editor's note:  Wang Feiteng is a doctoral supervisor at the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences, deputy director of State Key Laboratory of Cryospheric Sciences, and director of Tianshan Glaciological Station. He currently serves as a member of the expert panel of World Meteorological Organization's Global Cryosphere Watch and a member of the expert team of Third Pole Regional Climate Center. The article reflects the author's opinions and not necessarily those of CGTN.

For 18 years, I have been trekking on snowy glaciers. Urumqi Glacier No. 1 of the Tianshan Mountains, in Shawan City, northwest China's Xinjiang Uygur Autonomous Region, is one of the glaciers where I have conducted scientific expeditions many times.

In 2004, when I was still a doctoral student, I followed my supervisor to climb this glacier with an altitude of more than 4,000 meters for the first time, and I was deeply impressed. The Tianshan Mountains are so high and the valleys are so deep that the closer you get to the glacier, the colder it gets. Just in one day, you can experience four seasons of the year.

However, due to global warming, the glacier has retreated severely. In 1993, Urumqi Glacier No. 1 split into two branches called the East and West Branches. From 1994 to 2018, the East and West Branches retreated rapidly at an average rate of 4.7 m/year and 5.7 m/year respectively, and the thickness of the glacier also decreased by approximately 10.6 m between 1980 and 2012.

As a result of the retreat, new steep moraine ridges emerged at the end of the glacier that was once easily accessible, making it difficult to climb over and posing great physical and mental challenges to the researchers. It is predicted that the glacier may disappear in 50 years without human intervention in the context of global warming.

Glacier protection depends on the concerted efforts of the whole human society to slow down the melting of glaciers as much as possible. As a result of global warming, the glaciers worldwide are melting at a faster pace and have been on constant concession. In response to global warming, China has been implementing the national strategy of addressing climate change, and is well on track to reach its goals of peaking carbon emission and achieving carbon neutrality. However, slowing down the rate of melting of the glacier has become a very urgent task.

Over the years, researchers in China have been looking for ways to protect glaciers. The main causes of faster glacier melting include increased positive degree day (PDD), increased ice temperature, reduced ice surface albedo and glacier fragmentation. The main source of energy for glacier ablation is short-wave radiation from the sun, so the albedo of the glacier surface largely determines the energy available for glacier ablation.

The idea of increasing the albedo of glaciers by laying insulation and reflective materials on the glacier surface in order to slow down glacier melting became what drives the proposal of "covering the glacier with quilts." The reason why such practice slows down the melting of glaciers can be boiled down to the energy balance at the glacier surface. When the energy gained at the surface is greater than the energy released, the glacier starts to melt or sublimate.

The energy balance at the glacier surface is mainly determined by the radiation balance. Glacier ablation occurs mainly in summer, through surface ablation, intra-glacial ablation and sub-glacial ablation, with surface ablation accounting for the largest share. Direct solar radiation and near-surface atmospheric turbulence are the main sources of heat that cause glacier ablation.

Therefore, blocking solar radiation and heat exchange on the glacier surface can effectively slow down glacier melting. The so-called "quilt" is actually a layer of heat-insulating and reflective materials on the surface of the glacier's ablation zone with the aim of increasing the surface albedo, thus slowing down the ablation.

Urumqi Glacier No. 1, a well-known continental glacier, and Sichuan Dagu Glacier, a temperate glacier, were selected as the testing fields. The Dagu Glacier was covered with geotextiles, while Urumqi Glacier No. 1 was covered with two types of materials: geotextiles and new nanomaterials.

The results showed that from August to October 2020, the 500 square meters of geotextiles led to a significant reduction in the rate of ice ablation in the covered areas of Dagu Glacier, and were able to slow down the thinning of glacier by up to one meter, compared with the uncovered areas, i.e. slowing down glacier ablation by about 70 percent.

From June to August 2021, the total covered areas of Urumqi Glacier No. 1 were 450 square meters. The glacial melt in the covered areas were slowed down by 29 percent to 56 percent compared with the uncovered areas. The slowdown was more significant in the areas covered with nanomaterials at around 56 percent.

From the results of the experiment, it is clear that the glacier cover has a significant protective effect in slowing down glacial melt amid global warming. However, the protective effect of different cover materials on glaciers is very different. The use of inexpensive, reusable and effective cover materials is the key to glacier protection. In addition, manpower and traffic access are the two constraints for the promotion of this method. Therefore, it is mainly applicable to glaciers in western China that are easily accessible.

Of course, such experiment is still in its infancy, and more in-depth and extensive research is needed to explore more cost-effective methods of glacier protection in the future.

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