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.

This is the third year in the past four that has demonstrated significantly unusual ocean events, the researchers say, a period unlike any on record. The events have not all been the same. This year's ocean behavior is particularly bizarre, and there is no proof what is causing it.

But extreme variability such as this, OSU researchers say, is consistent with what scientists believe will occur as a result of global warming.

"All the climate models predict increased variability associated with global climate change," said Jane Lubchenco, professor of marine biology at OSU. "And there is no doubt that what is going on right now off Oregon is not normal."

In May and June when seasonal "upwelling" events should have begun that bring cold, nutrient rich water to the surface, the ocean was 8-11 degrees warmer than usual and had chlorophyll levels, a measure of productivity, about one-fifth to one-sixth of normal, said Lubchenco.

As a result, scientists were observing dead birds on beaches, major declines in fisheries, and other symptoms of a marine food web that was literally starving.

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

"The near-shore ocean right now looks like a brown pea soup," said Lubchenco, a director of the Partnership for Interdisciplinary Studies of Coastal Oceans, a research cooperative on the West Coast. "Just in the past couple weeks there was a spectacular bloom of diatoms."

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

The oceans and life they support are in a delicate physical and biological balance to sustain the marine ecosystem, Lubchenco said. Unusually wide variations in natural systems can lead to critical problems -- as they have repeatedly in recent years. The intense "dead zone" events that occurred in 2002 and 2004 killed a wide range of fish, 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 with the U.S.D.A. Forest Service, is an expert on the ecological impacts of global climate change. What is happening right now in the ocean off the Pacific Northwest is consistent with the expected impact of global warming, he said.

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

Global warming will cause high pressure systems and other weather phenomena to become more intense and concentrated, Neilson said, and sometimes get unusual systems locked into place for weeks or months at a time -- just like the events that last winter gave Southern California drenching rains while the usually-rainy Pacific Northwest enjoyed a balmy winter.

"These climatic blocking patterns can also persist for longer periods, year after year and even for decades," Neilson said. "We see this in terrestrial weather patterns all the time. But the oceans and land are all part of the same planet, and what affects one will also affect the other."

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

One possibility is that the ocean right now is becoming increasingly organized, meaning that currents and other mechanisms are shifting around in time and space to deal with and transport the increased heat they are absorbing, Neilson said. Heat always moves from the tropics to the polar regions, and during stable climate periods this process is fairly 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 recent years is very unusual," he said. "We may be beginning another fundamental phase change right now in how these ocean systems and circulation patterns will operate for decades to come. But we'll only know for sure later on, by looking backwards at the event."

"We can't say for sure yet that this volatility is being caused by global warming," he said. "But this is exactly the type of thing you would expect to see."