Apr. 1, 2005 – You probably consider those dust particles that make you sneeze and wheeze a nuisance, but those tiny pieces of matter could potentially affect the world’s climate, its oceans and even the food chain process, note the authors of a paper appearing in this week’s Science magazine.
In “Global Iron Connections Between Desert Dust, Ocean Biogeochemistry and Climate,” the authors – one of them Robert Duce, Distinguished Professsor of Oceanography and Atmospheric Sciences at Texas A&M University – conclude that dust, especially the iron in the dust, could have a global impact on the Earth far greater than anyone has believed.
Dust that contains iron is being swept up into the air from large arid and desert areas and eventually lands in the ocean, the paper says. And it’s not a small amount of dust: arid and desert areas occupy about one-third of the Earth’s surface.
Once reaching the ocean, iron-filled dust particles dissolve.
“This iron can then start a chain reaction of events in large areas of the ocean where it is the limiting nutrtient,” says Duce.
“Ocean plants growing in the area can be affected and, depending on the amount of iron present, the entire marine and biological productivity of the region can be impacted.”
In the 1930s, the “Dust Bowl” storms of that period produced huge swirling masses of dust that covered much of the western United States, Duce says. In the last 30 years, the results of human activity have been roughly the equivalent of a dust bowl itself – huge amounts of land have been cleared, construction has soared, population has increased and all of this has combined ultimately to change the terrain.
“With all of this dust reaching the ocean, the question is often asked: ‘Could you fertilize parts of the ocean with iron to increase productivity? The answer appears to be that it would not be a good idea. We just don’t understand enough about these types of growth cycles yet.”
The paper says that dust storm frequency in some areas of the world have increased, such as in China, North Africa and the United States—and perhaps Australia. These may be related to climate variability or land-use change caused by human activity.
The dust supply from the North African deserts directly affects tropical areas of the Atlantic and sometimes even Pacific oceans, the paper points out.
Duce says the typical dust particle contains only about 3.5 percent iron, but this amount is very significant considering the enormous amounts of dust that are swept up into the air and deposited into the oceans every year, roughly one billion tons.
“What is important to consider are the long-range effects of all of this dust entering the oceans,” Duce stresses.
“So there are some very big questions to be asked. If global warming is occurring as widely believed, what effect does this dust and its iron have on global warming? Would increasing the amounts of atmospheric dust cause the climate to cool because the dust would scatter more of the sun’s energy back into space? How does this iron-dust specifically affect marine productivity, and could changes in this productivity affect climate by taking carbon dioxide out of the atmosphere to fuel the growth of marine plants?
“We clearly need more research on this problem,” Duce adds. “This does not affect just one part of the Earth – it affects the entire Earth systems – land, atmosphere andn ocean. If this dust is changing significant atmospheric and marine life processes, we need to know about it. We definitely need a better understanding of the iron-dust cycle to find out what the long-range impacts could be for all of us.”
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