A recent volcanic eruption let scientists watch Mother Nature try out one of the geoengineering schemes that has been proposed to reduce the amount of carbon dioxide in the air, and therefore cool the planet. But the results of this natural experiment left a lot to be desired.
The geoengineering technique known as ocean fertilization calls for scientists to dump iron into the ocean to “fertilize” it and spur blooms of phytoplankton. These tiny photosynthetic organisms will suck up CO2 as they grow, the thinking goes, but will then die and tumble down to the sea floor, where the CO2 will be safely stored in the heaps organic matter.
The same thing can happen naturally, though, if a volcano happens to erupt and spews iron particles over the ocean. That’s exactly what happened in the summer of 2008.
In August 2008, scientists in the northeastern Pacific Ocean were shocked to witness a sudden, huge spike in the area’s plankton population. Their investigation traced the bloom to an ash cloud from a volcano that had erupted in the Aleutian Islands only a few days before. The ash, it turned out, had fertilized the ocean with thousands of tons of iron, on which the plankton gorged. [ScienceNOW]
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Of all the planet hacking possibilities floated as last-minute ways to stave off a climate catastrophe (building a solar shade for the Earth, injecting the atmosphere with sunlight-reflecting aerosols, etc.), iron seeding seems one of the more practical and feasible ideas. The scheme calls for the fertilization of patches of ocean with iron to spur blooms of plankton, which eventually die, sink, and sequester carbon at the seafloor.
However, worries over the consequences of tinkering with the ocean ecosystem have held up plans to attempt this. And now, in a study in the Proceedings of the National Academy of Sciences, researchers claim that such a plan could risk putting a neurotoxin into the food chain.
Iron seeders have targeted the large swaths of ocean surface with high levels of nitrate and low chlorophyll, where an injection of iron could potentially turn a dearth of plankton into a bloom. But too many phytoplankton can be a bad thing, especially when it comes to members of the genus Pseudonitzschia. This alga produces domoic acid, which it spews into the surrounding seawater to help it ingest iron [ScienceNOW]. Sea lions off California have gotten sick from the toxin. In Canada, three people died in the 1980s from eating shellfish that themselves had eaten Pseudonitzschia.
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A controversial geoengineering experiment that Greenpeace campaigned against (to little avail) has concluded, and researchers say their findings deal a major blow to the geoengineering technique known as ocean fertilization. As 80beats explained in January, the researchers dumped 20 tons of iron sulfate in the ocean near Antarctica in an effort to spur enormous blooms of phytoplankton, a type of algae; researchers theorized that when that plant life died and sank to the seabed it would lock away the carbon dioxide it had absorbed while growing. They hoped that widespread use of this technique could slow global warming.
While the iron did prove an algae bloom, researchers involved in the Lohafex project found that little biomass sunk down to the sea floor. Their results, announced in a press release, suggest that iron fertilisation could not have a major impact, at least in that region of the oceans. “There’s been hope that one could remove some of the excess carbon dioxide – put it back where it came from, in a sense, because the petroleum we’re burning was originally made by the algae,” said [researcher] Victor Smetacek…. “But our results show this is going to be a small amount, almost negligible” [BBC News]. Researchers also announced the surprising reason for that result: The plankton bloom wasn’t a carbon sequestration hot spot, instead it was an all-you-can-eat marine buffet.
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Sunshades in the stratosphere to reflect sunlight away from our planet. Dumping iron into the oceans to encourage algae blooms that would take up carbon dioxide. Painting every rooftop white. These are just a few of the geoengineering schemes that have been suggested to artificially alter the planet’s climate and counteract global warming.
Now researchers have helpfully ranked 17 proposals on their possible efficacy, saying that it’s past time to take a hard look at the ambitious ideas. “There is a worrying feeling that we’re not going to get our act together fast enough,” says [coauthor Tim] Lenton, referring to international efforts to limit greenhouse gas emissions. Scientists have reached a “social tipping point” and are starting to wonder which techniques might complement emissions cuts, he says [New Scientist]. The study, published in Atmospheric Chemistry and Physics, didn’t include an analysis of costs and environmental impacts.
Lenton says there has been too much hype and not enough analysis regarding geoengineering schemes, so he decided to start by asking a straightforward question. At the most basic level, earth’s surface temperature is governed by a balance between incoming Solar radiation and outgoing terrestrial radiation [Physics World]. The researchers examined how each of the geoengineering schemes would sway that balance, either by reflecting away solar radiation or reducing carbon dioxide that traps heat in the atmosphere. They found that a few proposed technologies could have a planet-wide cooling impact, but say those would be extremely hard to pull off.
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One of the most controversial geoengineering schemes that has been proposed to slow the course of global warming, ocean fertilization, received mixed reviews from a new study. The idea involves dumping iron into the ocean to nourish plankton and spur enormous blooms, which would then die off and fall to the sea floor, bringing the carbon dioxide they’d absorbed with them. Now, researchers studying natural plankton blooms near Antarctica have new evidence to fuel the debate over the efficacy of the process, and whether or not it can get our planet out of hot water.
Scientists took measurements around the Crozet Islands, where there are naturally occurring fluxes in iron levels. To the north of the islands levels of iron are boosted each year as iron-rich volcanic rocks are eroded and the nutrients are carried off by the current [Times Online]. Researchers observed a huge plankton bloom there that covered an area the size of Ireland and lasted for more than two months, while also studying the water to the south of the islands, where the prevailing ocean currents don’t carry dissolved iron and therefore plankton blooms don’t form naturally. The results, to be published tomorrow in Nature [subscription required], showed that iron-enriched waters do, as hoped, encourage more carbon to be stored on the ocean floor. But the efficiency of artificial iron fertilisation could be as much as 50 times lower than previous estimates [New Scientist].
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A German research ship carrying 20 tons of iron sulfate is currently motoring towards the South Atlantic, and the crew plans to dump its mineral cargo into the ocean in a controversial science experiment. The researchers will be testing a technique called ocean fertilization, in which iron is dumped into nutrient-poor waters to induce a huge blooms of phytoplankton. After the photosynthesizing plankton grows and absorbs carbon dioxide, researchers hope it will die and sink down to the seafloor still bearing that greenhouse gas in a natural form of carbon sequestration. Ocean iron fertilization is considered one of the more promising options for global-scale geoengineering, which aims to slow or reverse the effects of climate change caused by man’s burning of fossil fuels [Wired News].
But the so-called LOHAFEX experiment has raised the ire of some environmentalists, who worry about unknown consequences of interfering with the marine ecosystem. Ocean fertilisation experiments have been carried out on a few occasions in the past, but became controversial in 2007 when a company called Planktos announced it would dump iron fillings [sic] off the coast of the Galapagos islands. Some environmental organisations … expressed concerns that this was tantamount to pollution and, by affecting plankton at the bottom of the food chain could have unforeseen consequences [New Scientist]. The company Planktos went out of business and never conducted its experiment (largely due to the bad publicity), but the incident caused the UN Convention on Biological Diversity to ask countries not to permit ocean fertilization experiments.
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