Monday, March 8, 2010

Dead Zones On The March

When the tragic effects of global warming arrive, they're unlikely to present themselves in the spectacular form of a 1,000-meter wall of water or the demise of the dinosaurs.

They'll probably look more like creeping dead zones of hypoxia -- oxygen-starved pockets (the circus-clown variety, not Dittos Jeans) that suffocate most anything too slow to escape.

Given mainstream media's taste for the dramatic, it's gratifying to see big news outlets actually covering issues like this, so hats off to Les Blumenthal and McClatchy for this story. (Although illustrating the story with a dolphin is an odd choice, seeing as his oxygen isn't at issue.)

I read stories like McClatchy's and it gives me the heebie-jeebies.

Now, I live in a city that suffers frequent inversions, when cold air acts as a lid to trap warmer air that just hovers over us all like one of those dark clouds above an angry cartoon character. But it's not instantly fatal. What's more, I can escape in the short term -- to higher ground, or to the 'burbs, if not the countryside. Slow-moving sea creatures -- worms, mussels, starfish, urchins -- don't have that luxury. And even the faster movers' luck will run out if these blots of blight keep spreading.

This story is all about causality, of course, since we've known for a long time about a great many oceanic dead zones around the world (the McClatchy story says there are 400, and reliable sources put the number of "coastal dead zones" at around 50 a decade ago). For instance, the massive Gulf of Mexico dead zone, which at around 22,000 square kilometers is now bigger than the state of Israel, is largely a result of leaching and runoff from the Mississippi River.

So how do we know global warming's at fault in cases like those off the coast of the western U.S., where this story was focused? (It refers more broadly, however, to a growing problem in the Pacific, Atlantic and Indian oceans.)

Commendably, the McClatchy piece tries to explain. It quotes oceanographers Gregory Johnson of the National Oceanic and Atmospheric Administration in Seattle and Jack Barth of Oregon State University suggesting that the oxygen depletion has been growing quickly in recent decades, presumably correlative to rising global temperatures:

In some spots, such as off the Southern California coast, oxygen levels have dropped roughly 20 percent over the past 25 years. Elsewhere, scientists say, oxygen levels might have declined by one-third over 50 years.

"The real surprise is how this has become the new norm," said Jack Barth , an oceanography professor at Oregon State University . "We are seeing it year after year."

Barth and others say the changes are consistent with current climate-change models. Previous studies have found that the oceans are becoming more acidic as they absorb more carbon dioxide and other greenhouse gases.

The other indicator of global warming's role in all this, the article goes on to suggest, is the havoc that it plays with upwelling and downwelling, preventing the essential exchange of nutrient-rich, oxygen-poor water for oxygen-rich surface water that's nutrient-poor.

That pretty much sums up the two most compelling arguments in Blumenthal's piece pointing to rising temperatures -- and thus man, unless you're the Czech president or in the fossil-fuels business -- as a major factor in these expanding oceanic dead zones.

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