Over the course of geological time, the amount of carbon trapped in land and the oceans has waxed and waned. So has the amount of carbon dioxide in the atmosphere. These fluctuations correlate closely with changes in global temperatures. Therefore, studying the flow of carbon between land, water and atmosphere through geological ages can shed light on issues surrounding today's global warming.

New research described in the May 26 issue of Nature provides some missing pieces in the puzzle depicting the global carbon cycle over geological time. During what geologists call "oceanic anoxic events," it has long been suggested that a large amount of the greenhouse gas carbon dioxide is removed from the atmosphere by millions of microscopic organisms that dwell in the oceans. They do this by trapping carbon in their bodies. When they die, their bodies rain down to the ocean depths and are buried by sediment, locking away the trapped carbon from the atmosphere for million of years.

Scientists believe that during oceanic anoxic events the biological activity or "productivity" of these oceanic organisms is for some reason enhanced. On the other hand, perhaps the number of these oceanic organisms is somehow much greater during OAEs than during normal times.

Oceanic anoxic events are extremely unusual in other ways, too. They are often associated with mass extinction among many marine organisms and coincide with periods of intense global warming.

Scientists have long debated what causes OAEs. The prevailing theory is that a release of massive amounts of methane into the ocean is the root cause. The methane, in turn, oxidizes creating colossal amounts of carbon dioxide in the ocean and atmosphere, which depletes the oceans o
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Contact: Greg Borzo
gborzo@fieldmuseum.org
312-665-7106
Field Museum
25-May-2005