Resource: Arctic Haze

Print Background Essay

There is often a haze in the Arctic skies—especially during the winter and early spring. Instead of the clear blue skies one might expect to see over the region, the air looks dirty. From the ground, the sky looks pale instead of blue; from the air, there is a reddish-brown layer of haze hovering above Earth's surface. This diminished visibility is due to the presence of fine particles in the atmosphere, which scatter sunlight and reduce the transparency of the air.

Some of the particulates in Alaska's atmosphere may be of natural origin, such as sand and sea salt, but most of the aerosols—tiny particles suspended in the air—are the result of human activities. For example, sulfates, a large component of the haze, are the result of the burning of fossil fuels such as coal and oil. However, the Arctic region is not a significant source of these aerosols; the pollution that causes the haze originates in industrialized areas outside of the Arctic.

Pollution produced in lower latitudes can travel thousands of miles to the Arctic via air currents. In particular, atmospheric circulation patterns (essentially convection currents), caused by the temperature difference between the north polar region and the tropics, bring air masses northward. As the warmer, less dense air near the equator rises and flows toward the Arctic, it picks up and transports pollutants within it; emissions produced in Europe could reach the Arctic in just a matter of days. However, when the warmer, polluted air flows over the cold air mass above the Arctic, it gets "trapped" because the atmosphere is stabilized. Especially during the winter, when there is little or no sunlight to warm the ground or air, the air temperature increases with height—there is a temperature inversion—which inhibits atmospheric movement. This stability also minimizes the formation of precipitation, which typically removes pollutants from the air. As a result, the particulates may be trapped over the Arctic for up to a month, creating a haze.

Air pollution in the Arctic affects more than the appearance of the sky. For instance, some pollutants from the haze are deposited in the snow and ice and enter into ecosystems, where they can cause damage. Air pollution also affects climate change; for example, dark pollutants such as soot darken snow and ice, thus lowering albedo (the measure of how much solar radiation is reflected from Earth's surface) and creating an ice-albedo feedback loop that accelerates melting. In addition, the presence of aerosols forms smaller, more numerous cloud droplets, making clouds more reflective; thus, pollution in the atmosphere makes clouds more effective at reflecting sunlight back into space, contributing to a cooling effect. However, recent research has found that the Arctic haze has the opposite effect; it increases surface temperatures by increasing the ability of clouds to reflect escaping radiation back to Earth, acting like a blanket to trap heat at the surface.

To learn more about how pollutants affect food chains, check out Contaminants in the Arctic Food Chain and Contaminants in the Arctic Human Population.

To learn more about how pollution affects albedo, check out Earth’s Albedo and Global Warming.

To learn more about global winds, check out Giving Rise to the Jet Stream.

Print Questions for Discussion

• In the beginning of his study, the scientist expected that the air in the Arctic would be pristine. What was the basis for his assumption?
• How can you explain the presence of tiny particles in the air around an industrial city, for example, Detroit? How can you explain the presence of tiny particles in the Alaskan air, far from sources of pollution?
• Why does the pollution remain in the air so long in the Arctic?
• Do you agree or disagree with the idea that plants, animals, land, water, and air are part of a whole living organism? Explain your answer.
• Why should we be concerned about environmental degradation in other parts of the world?