Lower albedo drives glacier melting on Qinghai-Tibet Plateau: study

Chinese researchers have found that albedo **reduction was an important driver of glacier melting on the Qinghai-Tibet Plateau and its surrounding areas.

The Qinghai-Tibet Plateau, known as “the water tower of Asia,” houses abundant glaciers vital to the regional water cycle and water resources in downstream areas.

The glaciers have been shrinking in recent years, mostly due to global warming. They are also profoundly modulated by surface albedos, according to a research article recently published in the journal Earth-Science Reviews. Albedo commonly refers to how well a surface reflects solar energy.

The researchers from the Chinese Academy of Sciences and Lanzhou University summarized the current status of the glaciers around the Qinghai-Tibet Plateau and its surrounding region.

Based on glacier surface snow albedo data, they investigated the potential impact of glacier surface snow albedo changes on glacier melting between 2001 and 2018. The results showed that glacier shrinkage was pronounced over the Himalayas and southeast of the plateau.

The regional distribution of the average albedos on the glacier surface during summer exhibited similar patterns to those of glacier retreat and mass balance changes, indicating a significant relationship between the annual glacier mass balance and glacier surface albedos.

The glaciers on the Qinghai-Tibet Plateau

It can be concluded that albedo reduction, together with rising temperatures and changing precipitation, was a significant driver of glacier melting on the Qinghai-Tibet Plateau, according to the study.

Based on the glacier surface summer albedos and snowmelt model, the researchers estimated that the effect of surface albedo reduction can drive about 30 to 60 percent of glacier melting.

Due to the strong absorption of light, black carbon in snow substantially contributed to albedo reduction, which enhanced glacier melting on the plateau in summer by approximately 15 percent, said the research.

Background: What is albedo?

** Albedo is the amount of sunlight (solar radiation) reflected by a surface, and is usually expressed as a percentage or a decimal value, with 1 being a perfect reflector and 0 absorbing all incoming light. When talking about albedo, the surface is almost always the surface of a planet like Earth.[2] White objects, such as a snowy hill have a high albedo. Conversely, dark objects, like pavement, have a low albedo.[3] The term can also refer to human made structures. In fact, energy efficient building design takes albedo into consideration whether a wall or ceiling warms the building or keeps it cool – resulting in a choice of a dark or light coating respectively.

For a given area, albedo is determined by more than just the composition of soil, it’s impacted by soil moisture, type of vegetation, and levels of urbanization. Different surfaces on the Earth have different albedos (shown in Figure 1) and that albedo varies with time. Changes in albedo occur as the amount of cloud cover changes. Likewise, changes in any surface cover, like snow, ice, and vegetation, shift the albedo. Albedo is one of the major properties that controls how much energy is absorbed by the surface of the Earth, the cloudiness and ground cover are important factors in climate models.

The Earth’s surface doesn’t have a single albedo, rather a number of different albedos that are combined into a single number to accurately describe how the Earth reflects and absorbs solar energy as a whole. Figures 2 and 3 below (see following link) illustrate different albedos around the world, and how those albedos change depending on the time of year. For both images, high albedos are represented by the colour white while lower albedos are a dark blue.

Reference: https://energyeducation.ca/encyclopedia/Albedo

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