Snowpack is a vital source of water and food for billions of people around the world, especially in regions that depend on snowmelt from high mountains.
However, snowpack is also vulnerable to the effects of climate change, which can reduce its amount and duration.
A new study by scientists at the Pacific Northwest National Laboratory (PNNL) suggested that there is a silver lining to this bleak scenario: cleaner snow can boost future snowpack predictions and mitigate some of the impacts of warming temperatures.
The difference between clean and dirty snow
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Snow is not just snow, according to Dalei Hao, the first and corresponding author of the study. There are different types of snow, depending on the amount and nature of the particles that settle on it.
These particles can come from human activities, such as car emissions or wood burning, or from natural sources, such as dust.
They can affect how snow reflects and absorbs sunlight, which in turn affects how fast it melts.
Clean snow, which has fewer dark particles, reflects more sunlight and stays cooler than dirty snow, which has more dark particles that absorb more sunlight and heat up faster.
Dirty snow can also transfer its warmth to nearby clean snow, accelerating the melting process. This phenomenon is known as the snow-albedo feedback.
The researchers used a global climate model to simulate how different factors, such as temperature, pollution, dust, and snow grain shape, influence future snowpack in the Northern Hemisphere.
They found that temperature was the most important factor, followed by the effect of dark particles.
They also found that the shape of snow grains, which can vary from spherical to irregular, can affect how tightly they pack together and how much air they trap, which can influence their thermal properties.
The researchers projected that by the end of the 21st century, under a high-emission scenario, the average snow water equivalent (SWE), which measures the amount of water contained in a given volume of snow, would decrease by 43% in the Northern Hemisphere.
However, when they accounted for the expected reduction in pollution and dust due to stricter emission regulations and improved land management practices, they found that the SWE decline would be only 23%.
This means that cleaner snow can help slow down the loss of snowpack in the future.
The study also showed that cleaner snow can delay the peak timing of snowmelt by about 10 days, which can have significant implications for water management and agriculture.
Earlier snowmelt can cause flooding in spring and water shortages in summer, affecting crop production and food security.
Delaying snowmelt can help avoid these problems and provide more reliable water supply throughout the year.
The study focused on the Northern Hemisphere, where most of the global population lives and where most of the mountain ranges are located.
The researchers said that their findings are applicable to regions such as North America, Europe, Central Asia, and parts of East Asia.
They also said that their study highlights the importance of considering multiple factors that affect future snowpack predictions and the need for more accurate measurements and observations of snow properties.
