In its sixth year, Pacific dead zone closer to surf
The dead zones appear to be linked to an unusually persistent northerly wind that pushes surface waters away from the coast. The cool waters (the blue area off the coast of Oregon in this map) that well up from deeper in the ocean are rich in nutrients but low in oxygen. Photo: NASA
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For the sixth year in a row, scientists have found oxygen-starved water off the coast of Oregon.
The large pool – not far beyond Oregon’s coast – is commonly known as a “dead zone.” It can potentially suffocate slow-moving creatures such as crabs and sea stars on the ocean floor. Francis Chan is a marine ecologist at Oregon State University.
Francis Chan: To find it just within a mile or two of the surf zone, is really something that we have never seen before. We really don’t see any records of oxygen levels this low, this close to shore.
The Gulf of Mexico dead zone is caused by nitrogen runoff from land. But Chan and other scientists believe the Oregon zone is caused by winds that move nutrient-rich water from the deep off-shore to the very near-shore. The nutrients feed algae, which eventually die, decompose, and deplete the water of oxygen.
Francis Chan: When we look out at the big Pacific ocean, we think that such a large marine ecosystem, that it’s not going to change very much from year-to-year. But I think these events are telling us that these are fairly dynamic systems and that fast and rather surprising changes can happen.
Our thanks to NOAA, the National Oceanic and Atmospheric Administration.
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Chan said one of the biggest factors in driving the appearance of low-oxygen ozones off the Oregon coast is climate variability. “And when I say climate,” he said, “I mean the year-to-year changes in both the kind of wind pattern that we have off the U.S. west coast and the kind of ocean water and currents that exist off the coast in a very large scale.
“For example, we know that last year we saw the largest and most severe low-oxygen zone near the Oregon shore. And as it turns out, that’s the result of some of the strongest upwelling winds that we have on record.
“As far as the long-term pattern, this is just such a new phenomenon to our coast and we don’t quite have a good handle on the major climate patterns that might be giving us these low-oxygen zones from year to year.
“Having said that,” he concluded, “I think that the key science message is that the continued re-appearance of these low-oxygen zones are telling us that the coastal ocean can be a pretty sensitive ecosystem. We can change fairly rapidly and fairly dramatically from a normally productive system to one where there’s quite a few surprises.”
OSU Scientists Detect Low-Oxygen Zones Forming Off Coast for Sixth Straight Year, press release from Oregon State University.
Our thanks to:
Francis Chan
Research Professor
Oregon State University
Nancy Rabalais
Executive Director
Louisiana Universities Marine Consortium
