materials excerpted from Arctic Pollution Issues: A State of the Environment Report,
by the Arctic Monitoring and Assessment Program
The term "arctic haze" was coined in the 1950s to describe an unusual reduction in visibility that the crews of North American weather reconnaissance planes observed during their flights in the High Arctic. After further study of visibility data in the mid 1970s, it became clear that the haze was seasonal, with a peak in the spring, and that it originated from anthropogenic sources outside the Arctic. The most severe episodes occur when stable high pressure systems produce clear, calm weather. Visibility can be reduced to 30 kilometers (~19 miles), in spite of the otherwise clear weather.
Matthew Bean, a Yup'ik elder from Betel, Alaska, describes the changes he has seen in the sky: "Sometimes back, the skies on a clear day used to be deep blue all over, even at the horizon. Now you can hardly ever see that anymore, especially on the horizon. It is always pale blue, almost white or even dirty gray. It makes me sad to see what future generations are going to have to put up with."
The haze has been thoroughly analyzed. It consists of sulfate (up to 90 percent), soot, and sometimes dust. The particles are about the same size as the wavelength of visible light, which explains why the haze is so apparent to the naked eye. The composition of haze has been used as a chemical fingerprint to identify its sources. The presence of black carbon and a particular relationship between the metals vanadium and maganese indicate coal burning. Most of the particles originate in Eurasia.
The transport routes for the haze are well understood. Eurasian emissions are much more important than those in North America, in part because the Eurasian sources are 5-10 degrees further north than those in North America. Moreover, the Arctic air mass stretches relatively far south over the Eurasian landmass during the winter. The contaminants are thus picked up by the airmass that moves northward and over the pole in winter months.
Why is Arctic haze important? First, it completely changed the earlier notion that aerosol, or airborne pollution could only be local or regional. The cold, dry air in the polar regions allows particles to remain wind borne for weeks rather than days, which in turn allows sulfur contaminants to spread from industrial sources in Eurasia across the entire Arctic and into North America.
Second, haze particles might give metals and other contaminants a free ride to and within the polar region. Metals as well as some persistent organic compounds adhere to aerosols and could be deposited along with the aerosols. Substantial amounts of industrial contaminants may thus be washed out by precipitation occurring over major ocean areas surrounding the Arctic.
Arctic haze often appears in distinct bands at different heights because the warm dirty air is forced upward until it reaches the dome of cold air that sits over the North Pole in the winter. The clear, cold winter weather is one important reason why Arctic haze occurs in winter and spring and not in summer and fall.
The most apparent effect of the haze is that it reduces visibility.... In spite of their impact on visibility, the levels of sulfur compounds are much lower than those found in heavily polluted cities. Due largely to low deposition rates, the haze causes neither adverse effects on plants and animals, nor direct health problems in people.
Recently, Arctic haze has also been brought into discussions on global
climate change. Unlike regions with low surface reflectivity, acidic and
soot-laden aerosols over highly reflective snow tend to warm rather than
cool the spring Arctic atmosphere. At certain times of the year, a viewer
from space would see the North Pole as orange-brown rather than white
because of the soot in the haze. The consequences for global climate are
poorly understood and climate models are just starting to take the haze
into account. They suggest small but measurable effects.
For more information visit the Arctic Monitoring and Assessment Programme catalog online at http://www.grida.no/amap/amap.htm