Geoengineering: Iron Dumping

A recent report in the journal Nature describes an innovative method for trapping greenhouse gases on the ocean floor for centuries, or longer.

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Earlier this year, reported on rising ocean and atmospheric temperatures.  This week, reports were released that detailed a new method, called “geoengineering,” or technology designed to alleviate global warming by reducing the effects of heat-trapping greenhouse gases, that has proven successful in trapping carbon deep within the ocean floor.  This will keep the carbon out of the atmosphere for many centuries or longer.
Dumping iron into the world’s ocean stimulates the growth of algae, an efficient way of removing carbon dioxide from the atmosphere.  In an initial study in 2004, scientists dumped seven tons of iron sulfate across 58 square kilometers of ocean off the coast of Antarctica.  The location plays a central role in the global carbon cycle, according to Christine Klass, a co-author of the study and a researcher at the Alfred Wegener Institute for Polar and Marine Research.  The experiment location, a 96.5 mile-wide self-enclosed eddy served as a giant “test tube.”  
The study was featured in the journal Nature, and dispels earlier concerns that iron fertilization can cause deplete oxygen and create conditions that are dangerous for other marine life.  Researchers had also held concerns that plankton blooms could be harmful to some species.   
Professor Victor Smetacek, also of the Wegener Institute, said of the study’s critics, "The time has come to differentiate: some geoengineering techniques are more dangerous than others. Doing nothing is probably the worst option.”  Dave Reay, senior lecturer in carbon management at the University of Edinburgh, said the study “represents a whole new ball game in terms of iron fertilization as a geoengineering technique,” while adding more study was still required.
The iron sulfate cases a “bloom” of diatoms -- algae that group together in large, slimy masses, and then sink to the ocean floor, as well as plankton, tiny plants that can absorb carbon dioxide.  The study showed that 50 percent of of plankton blooms sunk to depths lower than 1,000 meters, while a “substantial portion was likely to have reached the ocean floor” at a depth of 12,500 feet.
While scientists have spent the past eight years verifying their results, they are still cautious about this approach.  According to Dieter Wolf-Gladrow, another study co-author, iron seeding “cannot provide a solution for our CO2 problem.” Even under “very, very optimistic assumptions,” iron dumping would only absorb approximately 10 percent of our current carbon emissions.  
Professor Smetacek acknowledged that more observation was required to determine how many of the diatoms actually reached the ocean floor, as opposed to say, being eaten by krill which are subsequently eaten by whales. 
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