The Oregon situation is quite different from the Gulf of Mexico, which has a dead zone off the Mississippi River Delta that can blanket 6,000 to 7,000 square miles. That zone is caused by runoff from a huge swath of North America that pumps tons of nutrients, particularly nitrogen and phosphorous, into the gulf. That causes an enormous algae bloom, ending with a result that is similar to Oregon's.
Scientists on the West Coast say they have looked at the possibility of agricultural runoff, or various toxins, causing the Oregon dead zone, and they believe they have ruled that out. Measurements of oxygen in the water show that it is depletion of oxygen, caused by a fundamental change in wind patterns, that is at work there.
"This change from normal seasonal patterns and the increased variability are both consistent with climate change scenarios," Barth noted.
It may be an understatement to say the researchers are concerned, but at this point there are too many uncertainties to know just how serious the problem is and whether it will continue in the future. Figuring out local effects of global climate change is one of the most difficult challenges facing scientists today.
At first, scientists weren't even sure of what they were seeing. Is the dead zone really new, or could it be that scientists were just beginning to take the measurements that proved it was there?
To answer that, the scientists turned to those who know the waters best: commercial fishermen.
"We've met with some old timers who've spent four or five decades on the water, and we asked them if it's normal to pull up a crab pot and find dead crabs," Chan said. "The answer is definitely no."
But they're doing just that this year, and it will continue until the first winter storm blows in from the south, possibly as early as September. That will change ocean currents and mix the water column, allowing marine life to once again return to one of the nation's most beautiful and bountiful shorelines.