Lunatics or Climate Fixers?

The ocean has already absorbed nearly one-third of the carbon emissions from human activities, and scientists hope it can shoulder even more of the burden. Ocean Iron fertilization is among the cheapest options. Ocean fertilization is a form of geoengineering  that involves adding iron to the upper layers of the ocean to stimulate phytoplankton activity  in an attempt to remove carbon from the atmosphere and, thus, abate global warming.

Photosynthetic plankton act like tropical rainforests, sucking CO2 from the atmosphere. Their populations are often limited by a scarcity of iron, which sifts into the ocean in windblown dust from deserts, in volcanic ash, and even from underwater hydrothermal vents. Extra iron would stimulate a bloom, the thinking goes, causing plankton to take up extra carbon. The carbon would sink into the depths in the form of dead plankton, or the feces or bodies of organisms that eat them. In theory, the carbon would be entombed for centuries.

Ocean scientists contended in 2021 that ocean fertilization  experiments were a priority and called for the United States to spend up to $290 million on even larger ones that would spread 100 tons of iron across 1000 square kilometers of ocean. Already, researchers next year plan to pour iron across a patch of the Arabian Sea (Center for Climate Repair at the University of Cambridge.)

But skeptics note that a recent survey of 13 past fertilization experiments found only one that increased carbon levels deep in the ocean. That track record is one reason why making iron fertilization a research priority is “barking mad,” says Wil Burns, an ocean law expert at Northwestern University. Stephanie Henson, a marine biogeochemist at the United Kingdom’s National Oceanography Centre, also worries about surprise consequences of the approach, likening it to the catastrophic introduction of rabbits to Australia ecology. “You could just imagine something like that happening in the oceans completely by accident.”

Excerpts from Warren Cornwall, To Draw Carbon, Ocean Fertilization Gets Another Look, Science, Dec. 17, 2021

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