Share this story
Close X
Switch to Desktop Site

Haze over the Arctic: a climate experiment that no one planned

Scientists have often daydreamed about covering the Arctic with heat-absorbing soot. Would this warm the region enough to affect the climate? Man-made arctic haze has turned these idle dreams into reality. It is an unplanned climatic experiment.

That is why Canadian, Norwegian, and US scientists plan to carry out an intensive ground and air study of the haze in March and April. They need more data to assess the environmental importance of what they consider the oddest case yet found of long-range industrial pollution.

About these ads

As a phenomenon, arctic haze has been reported for a quarter of a century. But its true nature has been realized only in the past few years. Ground samples taken in Canada and Alaska show it is loaded with soot (carbon particles), acid, and toxic metals.

Kenneth A. Rahm of the University of Rhode Island and Glenn E. Shaw of the University of Alaska, two leading haze researchers, have concluded the main source is heavy industry in the central Soviet Union. They note that the term ''central'' may include parts of Europe as well as Siberia.

Among other indications, Shaw has found Landsat (Earth survey satellite) photos of Siberian smelting centers in which vast plumes of pollutants can be traced for many kilometers. These are typical of the kinds of sources that could contribute sulfur dioxide (acid) and heavy metals. Carbon soot presumably comes from burning coal.

The haze is of climatic concern mainly in the spring. Transported into the Arctic during the winter, its soot particles absorb heat in the lower atmosphere and on the surface. This could lead to warmer temperatures in the high Arctic during the spring. By summer, the haze is gone.

James T. Peterson of the US National Oceanic and Atmospheric Administration (NOAA) explains that the degree of such warming, if any, and its climatic importance are uncertain. There are not enough data on the haze to feed to climate-simulating computer programs. Hence the forthcoming three-nation study.

Scientists such as Rahm and Shaw are also concerned about acid and metal pollution. They published an extensive review of arctic haze last fall in the Naval Research Reviews, in which they emphasize that the ecological effects of these pollutants also need study. Little is known about what the acid may be doing to arctic food chains and the delicate web of tundra life.

To identify the Soviet Union as the main source of the haze is not to rule out possible contributions from Western Europe or North America. But it does show that pollution can sometimes travel surprisingly long distances. So far, the Soviet Union has refused to join in arctic-haze studies. It owes it to the world to help in understanding what could be a major climatic ''experiment.'' How old is the deep sea?

About these ads

As Earth's most striking characteristic, the ocean has been around for eons. But the age of its deep waters, considered its most stable region, has never been known with certainty. Paul D. Quay and Minze Stuiver of the University of Washington and H. G. Ostlund of the University of Miami say it may be a surprisingly young 500 years.

As the scientists point out in a report in Science, this has implications both for world climate and for plans to dispose of radioactive waste at sea.

Deep water forms when surface water sinks, having been made heavier by cooling or by evaporation, which concentrates its salt. Such water has been thought to move sluggishly and to remain below for long periods. Its turnover time is related to exchange of heat between air and sea, and thus is a regulator of climate.

The scientists took a new look at where surface water sinks and at the processes involved. They have dated deep water in several parts of the world, using the radioactive form of carbon known as C-14. Sea water absorbs C-14 from the air. Once it sinks, it can no longer replenish its C-14 supply, which gradually disappears due to radioactive decay. Thus the C-14 content of deep water is a measure of its age.

The study indicates deep-water replacement times of 510, 275, and 250 years for the Pacific, Atlantic, and Indian Ocean respectively. ''The deep waters of the entire world ocean are replaced on average every 500 years,'' the scientists say.

This is quite rapid, compared to what has been assumed before. It should alter predictions of computer simulations of climate. And it should make those who would dispose of radioactive wastes at sea think again about the presumed stability of the deep sea.

Follow Stories Like This
Get the Monitor stories you care about delivered to your inbox.