PORTLAND - A scientific paper published last month says that the ecosystem structure of the ocean off the Columbia River has undergone a massive shift since 1998 when a strong El Nino event was followed by a rapid La Nina episode.

"The transition ... was possibly the most dramatic and rapid episode of climate change in modern times," said NOAA Fisheries' researchers William Petersen and Franklin Schwing, in their paper, published in the September issue of "Geophysical Research Letters".

Average ocean temperatures off the Oregon coast decreased by one degree C. (or more than two degrees F.) in 1999, while salinity increased. Coastal sea levels dropped as well, indicating stronger upwelling and a faster California current.

The authors said plankton biomass has doubled off California since 1998, rising to values not seen since the 1970s and cold water fish like anchovies have increased by an order of magnitude, "a primary food source for adult Chinook and coho salmon."

In the past several years, west coast salmon populations have rebounded from extremely low levels, setting records in some cases.

Reduced productivity of salmon and cod in the Gulf of Alaska also tracks with the notion that a regime shift has occurred, the authors said, which has "changed ecosystem production and structure throughout the northeast Pacific Ocean."

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