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Desert dust with iron has impact on ocean, global climate

Rosenstiel School scientist, others cite need for prioritized research

VIRGINIA KEY, FL (April 1, 2005) — The iron present in African dust appears to play a major role in global climate change through its impact on ocean biology, but because of the complexity of the processes it needs to be studied methodically. That is the conclusion of a multi-authored article in this week's April 1st issue of Science. “Global Iron Connections Between Desert Dust, Ocean Biogeochemistry, and Climate” outlines the issues regarding iron and our global climate and the research needed to resolve them.

Dr. Joseph M. Prospero, one of the authors and a professor in the Division of Marine and Atmospheric Chemistry at UM's Rosenstiel School for Marine and Atmospheric Science, was recently recognized by the American Geophysical Union and the American Association for the Advancement of Science for his long career researching the global transport of African mineral dust.

“Without question, the iron carried by dust has played prominently in the chemistry of the atmosphere, oceans, and sediments,” Dr. Prospero said. “Carbon dioxide is the major cause of global warming, and iron can play a role in reducing the amount of carbon dioxide through its impact on the marine biosphere. For this reason there's an international push to study this issue. However, we must be methodical. We need to understand nature's delicate biogeochemical balance and how iron dust has played a role in today's climate, so that we don't create new environmental problems as we try to understand the old ones.”

Iron is essential for all organisms. In plants, it is needed to produce enzymes required for photosynthesis. Photosynthesis removes carbon dioxide from the Earth's atmosphere-ocean carbon system and produces oxygen. Dust, which normally contains several percent iron, is transported from land through the atmosphere to the oceans and affects ocean biogeochemistry and the conversion of carbon dioxide to organic matter. Plants and marine organisms that die and sink to the deep ocean serve, in effect, to remove carbon dioxide from the atmosphere. Mineral dust is the main source of iron in the open oceans. But, the cycle is extremely complex as other variables factor into dust migration. Changes in climate such as droughts and increased wind speeds will increase the transport of dust through the atmosphere to the oceans. Human activities in arid regions can lead to increased wind erosion; inappropriate agriculture and overgrazing by animals are especially destructive.

Some researchers have experimented with fertilizing the ocean with iron to increase the absorption of atmospheric carbon dioxide so as to mitigate global climate change. However, science isn't clear on the consequences of these changes. There is great concern that the intensive fertilization of the ocean with iron could lead to vast and potentially disastrous changes in ocean ecosystems.

The 15 researchers who co-authored the Science article with Dr. Prospero noted that there are “considerable uncertainties in our understanding of these interactions requiring research that integrates across the whole earth system.” Research should be prioritized to explore how dust migrates and how well the windborne iron is absorbed or used by marine organisms. This kind of iron dust research is essential to improve global models for realistic global climate predictions.

Rosenstiel School is part of the University of Miami and, since its founding in the 1940s, has grown into one of the world's premier marine and atmospheric research institutions.

Ivy Kupec
Communications Director
Rosenstiel School of Marine & Atmospheric Sciences
University of Miami
305.421.4704 (o)
305.984.7107 (m)
ikupec@rsmas.miami.edu