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February
16, 2007 The California
Current system has
experienced significant changes during the past decade, resulting in
dramatic
variations in the ecosystem characterized by shifts in phytoplankton
production, expanding hypoxic zones, and the collapse of marine food
webs off
the western coast of the But the researchers
stopped short
of saying that climate change was the definitive cause. "This coming year
will be
important," said Jack Barth, a professor of oceanic and atmospheric
sciences at "Our research has
shown
there is a 'wobble' in the Jet Stream that in some years has tended to
overpower the more historic day-to-day variations in climate in favor
of these
two- to three-week wind patterns that influence upwelling and
ultimately, ocean
production." Eight scientists,
including five
with ties to During that El
Niño, ocean waters
off the West Coast grew warmer, nutrients decreased, biological
production was
reduced, and species from zooplankton to salmon disappeared, were
drastically
reduced or moved from their typical habitats. The El Niño
capped what had been
a series of years through the 1990s characterized by warm waters and
weak
upwelling. That regime ended
abruptly in
late 1998, and the California Current system entered a four-year period
of cold
ocean conditions, according to Bill Peterson, a NOAA oceanographer who
works
out of OSU's "Zooplankton stocks
more
than doubled in biomass, and the zooplankton community structure
suddenly
changed to one dominated by cold-water, lipid-rich species," Peterson
said. "Salmon stocks rebounded immediately and the good conditions
lasted
for four years. But the cold-water period ended as quickly as it began,
in late
2002, and the ecosystem began to revert to conditions seen during the
1990s." Before the change,
however, the
West Coast experienced an unprecedented invasion of sub-arctic water in
the
summer of 2002. This cold, nutrient-rich water triggered massive
phytoplankton
production in the surface waters, and as the organisms decayed and sank
to the
bottom, they sucked oxygen out of the lower water column, leading to
hypoxia
and marine die-offs. And though the ocean
waters
warmed over the next four years, the West Coast experienced hypoxia
events
every summer, according to Francis Chan, a senior research assistant
professor
at "When it comes to
upwelling
and phytoplankton production, there can be too much of a good thing,"
Chan
said. "Although the low-oxygen zone has varied in intensity from year
to
year, 2006 saw an unexpected expansion and degradation in oxygen
conditions. At
least 3,000 square kilometers of the continental shelf along the "This latest hypoxic
event," he added, "was off the charts." Nature threw a
different wrinkle
at the What this showed
scientists is
that changes to the system are multi-faceted. Large-scale changes have
an
imprint on the entire ecosystem, but there are surprises in local
systems that
may depend on the timing of winds as much as their overall strength and
duration. "We used to think we
could
look at the wind and predict runs of salmon," Peterson said. "That's
not necessarily the case. It's a lot more complex out there." Bruce Menge, an "I think what we're
seeing
is that the Pacific Decadal Oscillation has shifted," Menge said.
"The 20- to 30-year cycles are becoming less prominent than these
four-year cycles. What we don't yet know is whether these last couple
of
four-year cycles are just blips, or the whole system has gone haywire."
Oregon State
University's Jane
Lubchenco, a co-organizer of the West Coast variability symposium and
past
president of the AAAS, said the bottom line is that the dramatic events
of the
past few years have shown how vulnerable our oceans are to changes in
overall
climate – and how quickly ecosystems respond. "Wild fluctuations
in the
timing and intensity of the winds that drive the system are wreaking
havoc with
the historically rich ocean ecosystems off the West Coast," Lubchenco
said. "As climate continues to change, these arrhythmias may become
more
erratic. Improved monitoring and understand of the connection between
temperatures, winds, upwelling and ecosystem responses will greatly
facilitate
capacity to manage those parts of the system we can control."
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