snow melt

Every year, more than 100 million tons of dust blow out of North Africa. Strong seasonal winds lift the dust from the Sahara Desert northward. A few times a year, the winds from the south are strong and persistent enough to drive the dust all the way to Europe.

On March 15, a large plume of Saharan dust blew out of North Africa and crossed the Mediterranean into Western Europe. European cities were blanketed with the dust, degrading their air quality, and turning skies orange. Alpine ski slopes were stained with the dust.

These dust events are associated with so-called atmospheric rivers that arise from storms. Such rivers usually bring extreme moisture but can also carry dust. Over the past 40 years, nearly 80% of atmospheric rivers over northwestern Africa have led to extreme dust events over Europe. The March 15 event was associated with Storm Celia, a powerful system that brought strong winds, rain, sleet, hail, and snow to the Canary Islands.

Atmospheric dust plays a major role in climate and biological systems. The dust absorbs and reflects solar energy and also fertilizes ocean ecosystems with iron and other minerals.

The climate effects of dust are complicated. Dust can decrease the amount of sunlight reaching the surface, affect cloud formation, and decrease temperatures. But dust also darkens the snowpack, leading to more rapid snowmelt. A 2021 dust event resulted in a rapid melt of Alpine snow, reducing its depth by half in less than a month.

The effects of this year’s dust event are not yet known, but this atmospheric river associated with Storm Celia appeared to carry less water and more dust compared with the 2021 event.

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An Atmospheric River of Dust

Photo, posted December 2, 2019, courtesy of Catherine Poh Huay Tan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Glaciers in the Himalayas have been melting and retreating, as have glaciers around the world. As is the case elsewhere, human-driven climate change is a major factor. But at the lofty heights of the Himalayas, warming temperatures are not the biggest culprit. Black carbon – released into the air by burning fossil fuels or biomass such as plants, trees, and shrubs – darkens the snow and causes it to absorb more of the sun’s heat. A recent study by an international team of scientist has identified another important factor: dust.

An estimated 5 billion tons of desert dust enters the Earth’s atmosphere every year. Dust from places like Saudi Arabia gets picked up by spring winds and gets deposited on the western sides of mountains, where it can make the air 10 times more polluted than most European cities. Dust blows across industrial and desert areas in the Indian subcontinent and the Middle East and lands in the Himalayas. According to the new study, this dust is often the dominant cause of snow melt in those areas.

Desert dust causes snow melt in the same way that black carbon does. Dirty snow absorbs sunlight more easily than clean snow.

Desert dust is a natural part of Earth’s systems, but the amount of it in the atmosphere has steadily increased since the Industrial Revolution, when humans greatly expanded into desert areas and broke through surface crust that held large amounts of dust in place.

There is not much we can do about desert dust, short of eliminating deserts. But the disappearance of the Himalayan ice pack – which sustains over a billion people – can be mitigated by reducing greenhouse gas emissions to address climate change .

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Himalayan glaciers melting because of high-altitude dust

Photo, posted March 13, 2018, courtesy of Sarunas Burdulis via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.