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Another 'Dead Zone' May Loom Off Oregon Coast

Date:
August 22, 2005
Source:
Oregon State University
Summary:
The Pacific Ocean off of Oregon has experienced a die-off of birds, declining fisheries and wildly fluctuating conditions in the past few months, and has set the stage for another hypoxic "dead zone" like those of 2002 and 2004, according to experts at Oregon State University.
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CORVALLIS - The Pacific Ocean off of Oregon has experienced adie-off of birds, declining fisheries and wildly fluctuating conditionsin the past few months, and has set the stage for another hypoxic "deadzone" like those of 2002 and 2004, according to experts at Oregon StateUniversity.

This is the third year in the past four that has demonstratedsignificantly unusual ocean events, the researchers say, a periodunlike any on record. The events have not all been the same. Thisyear's ocean behavior is particularly bizarre, and there is no proofwhat is causing it.

But extreme variability such as this, OSU researchers say, isconsistent with what scientists believe will occur as a result ofglobal warming.

"All the climate models predict increased variability associatedwith global climate change," said Jane Lubchenco, the Wayne and GladysValley Professor of Marine Biology at OSU. "And there is no doubt thatwhat is going on right now off Oregon is not normal."

In May and June when seasonal "upwelling" events should have begunthat bring cold, nutrient rich water to the surface, the ocean was 8-11degrees warmer than usual and had chlorophyll levels, a measure ofproductivity, about one-fifth to one-sixth of normal, said Lubchenco.As a result, scientists were observing dead birds on beaches, majordeclines in fisheries, and other symptoms of a marine food web that wasliterally starving.

Then in mid-July, it appears that a normal, strong upwelling eventfinally began, bringing cool water and lots of nutrients. The resultingintense bloom of microscopic plants coupled with low oxygen levels nearthe ocean floor set the stage for another "dead zone" event this year.

"The nearshore ocean right now looks like a brown pea soup," saidLubchenco, a director of the Partnership for Interdisciplinary Studiesof Coastal Oceans, a pioneering research cooperative on the West Coast."Just in the past couple weeks there was a spectacular bloom ofdiatoms."

Some upwelling is essential and desirable. But too much can lead toa glut of phytoplankton which in turn decay and, in combination withthe right types of winds and currents, lead to over-consumption of theremaining oxygen in the water and a die-off of marine life.

The oceans and life they support are in a delicate physical andbiological balance to sustain the marine ecosystem, Lubchenco said.Unusually wide variations in natural systems can lead to criticalproblems - as they have repeatedly in recent years. The intense "deadzone" events that occurred in 2002 and 2004 killed a wide range offish, crabs and other marine species, literally suffocating them.Dissolved oxygen levels at the time were historically low.

Ronald Neilson, a professor of botany with OSU and ecologist withthe U.S.D.A. Forest Service, is an expert on the ecological impacts ofglobal climate change. What is happening right now in the ocean off thePacific Northwest is consistent with the expected impact of globalwarming, he said.

"We can't yet prove that the ocean changes you are seeing in thePacific are the result of global warming," Neilson said. "But there'sstrong evidence that long-term climate change will also result in amajor increase in short-term variability, on the time frame of months,years or decades."

Global warming will cause high pressure systems and other weatherphenomena to become more intense and concentrated, Neilson said, andsometimes get unusual systems locked into place for weeks or months ata time - just like the events that last winter gave Southern Californiadrenching rains while the usually-rainy Pacific Northwest enjoyed abalmy winter.

"These climatic blocking patterns can also persist for longerperiods, year after year and even for decades," Neilson said. "We seethis in terrestrial weather patterns all the time. But the oceans andland are all part of the same planet, and what affects one will alsoaffect the other."

A global oceanic "index" that measures such factors as temperatureand barometric pressure showed a fundamental increase in volatilitybeginning with the Dust Bowl of the 1930s, Neilson said. It fluctuatedin one long trend from the 1940s to 1970s, and began another patternfrom the 1970s to around the present, he said. But just in the past fewyears, this index has once again been extremely volatile.

One possibility is that the ocean right now is becoming increasinglyorganized, meaning that currents and other mechanisms are shiftingaround in time and space to deal with and transport the increased heatthey are absorbing, Neilson said. Heat always moves from the tropics tothe polar regions, and during stable climate periods this process isfairly orderly and predictable. When the climate changes, Neilson said,the process is expected to become much more extreme and variable.

"The wide variability and oscillation of ocean patterns in recentyears is very unusual," he said. "We may be beginning anotherfundamental phase change right now in how these ocean systems andcirculation patterns will operate for decades to come. But we'll onlyknow for sure later on, by looking backwards at the event." "We can'tsay for sure yet that this volatility is being caused by globalwarming," he said. "But this is exactly the type of thing you wouldexpect to see."


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Materials provided by Oregon State University. Note: Content may be edited for style and length.


Cite This Page:

Oregon State University. "Another 'Dead Zone' May Loom Off Oregon Coast." ScienceDaily. ScienceDaily, 22 August 2005. <www.sciencedaily.com/releases/2005/08/050819123253.htm>.
Oregon State University. (2005, August 22). Another 'Dead Zone' May Loom Off Oregon Coast. ScienceDaily. Retrieved April 16, 2024 from www.sciencedaily.com/releases/2005/08/050819123253.htm
Oregon State University. "Another 'Dead Zone' May Loom Off Oregon Coast." ScienceDaily. www.sciencedaily.com/releases/2005/08/050819123253.htm (accessed April 16, 2024).

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