productivity and summer "upwelling" on the Pacific Northwest
coast appears to be strongly correlated to oscillating jet
stream patterns, according to a new study that draws
definitive links between short-term ocean effects and larger
In normal summer patterns, the research
found, there is a 20-day oscillation of the jet stream -- a
strong air flow about seven miles high -- that moves north and
south, and is tightly linked to normal upwelling activity and
the growth of phytoplankton and zooplankton, the basis of the
marine food chain.
It's less clear, scientists say, how long-term climate
changes, such as El Nino events or global warming, may be
affecting the jet stream. But the clear connection between the
jet stream and underlying marine productivity is significant
in itself, they said.
The study was published this week in the online version of
Proceedings of the National Academy of Sciences, a
professional journal, by researchers from Oregon State
University, the University of North Carolina, and the National
Marine Fisheries Service.
"We've known for some time that winds play a fundamental
role in controlling upwelling and biological productivity,"
said Ricardo Letelier, an associate professor of oceanography
at OSU. "But now we can better define the larger patterns that
force this action and the short-term biological fluctuations
Yvette Spitz, an OSU associate professor of oceanography,
also said that in the ocean off central Oregon, there appears
to be a very strong and well-defined 18-year cycle of
upwelling intensity, and an "upwelling index" in the region is
now at almost its highest value since the early 1990s -- a
time when, among other things, summer upwelling seems to be
delayed longer than usual, but then becomes very intense.
It's possible this is relevant to the recent hypoxic events
that have been observed in this region, they said, but more
research needs to be done before that linkage can be drawn.
There are probably multiple forces that are part of the
"The correlation between movements of the jet stream and
the underlying biological action in the ocean is really quite
strong," Spitz said.
When the system is operating in a healthy and productive
pattern, the scientists found, the jet stream oscillates north
and south, causing shifts in the wind patterns beneath it, and
causing an ebb and flow of nutrient enriched water on the
near-shore coast. This forms the basis for one of the world's
more productive fisheries.
This situation exists most of the time, although the study
documented two years out of 12 when the process broke down.
Other parts of the Pacific Ocean coast off North America
and Mexico have coastal upwelling also, the study noted, but
it is often less intense and more stable because the jet
stream is more distant and has less impact on these areas.
It's not certain what effect global warming or other
changes in ocean processes may have on these patterns, the