Day 3: Choking the Oceans

Date posted: January 26, 2009
Posted in: 100 Days of Science | climate change
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Global warming has the potential to dramatically expand the oceans’ so-called dead zones, oxygen-poor areas that fish avoid and where less mobile organisms like clams and crabs can’t survive.

Most dead zones are located where rivers empty into the ocean, dumping agricultural fertilizers and other pollutants. A new study by a team of Danish researchers, released yesterday in Nature Geoscience, predicts that such zones could grow by a factor of 10 or more in a scenario of unchecked global warming.

I wrote an article for National Geographic News about dead zones back in August, in which I reported on study by Robert Diaz of the Virginia Institute of Marine Science. He and his team documented an expansion of these hypoxic areas that has already taken place. As of August, Diaz and a co-author had discovered 400 known dead zones in coastal waters worldwide, compared to 305 in the 1990s. The numbers were up from 162 in the 1980s, 87 in the 1970s, and 49 in the 1960s. In the 1910s, four dead zones had been identified. That study appeared in the August 15 issue of Science.

In the new study, lead author Gary Shaffer, of the University of Copenhagen, and his team used computer models to show that changing circulation patterns in the ocean could weaken in response to global warming, causing oxygen-depleted zones to expand and invade the deep ocean. They warn that expansion of dead zones could lead to fish and shellfish kills and, eventually, wide-scale alterations in nutrient cycling and productivity.

Shaffer used his results as a call to action: “Reduced fossil fuel emissions are needed over the next few generations to limit ongoing ocean oxygen depletion and acidification and their long-term adverse effects,” he said in a press release.

Meanwhile, the Independent, a UK publication, has reported that an international team of researchers plans to add iron supplements to a 186-square-mile patch of the Southern Ocean, as a potential answer to global warming. The Independent reports:

“As the waters are short of iron, this is expected to lead to an explosive growth of plankton, which will take up carbon dioxide from the air. The  scientists hope that, when the plankton die and their bodies sink deep into the ocean, they will take the carbon with them, keeping it out of the atmosphere for centuries. Applied on a large enough scale, they believe this could help stave off climate change, while increasing food for whales. Commercial firms have already announced plans to make money from such schemes.”

I’m no climate scientist, but my hunch is that we should clean up the global mess we’ve created with our brilliant innovations, before we throw more brilliant innovations at it. Just sayin. (Also ocean-related: Deeply sad Associated Press YouTube video of the whales that died on a sand bar near Australia, last weekend.)

That said, iron supplements have long been debated as a way to enhance the ocean’s ability to hoard carbon, thereby lightening its load in the atmosphere. Still under embargo until Wednesday is a new study that gets to exactly how much carbon the iron could offset. Stay tuned …

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