Sunday, June 25, 2006
California Current Warming?
This is the time of the year when the ocean off the California coast should be at its most lush, teeming with vast schools of krill to feed whales and salmon as well as plenty of baby rockfish for seabirds, seals and fishermen's nets.
But based on new counts from the National Oceanic and Atmospheric Administration, federal researchers are reporting an odd summer and a scarcity of some sea life from San Diego to Newport, Ore., for the second year in a row. And some scientists wonder if the warming of the world's oceans and atmosphere is playing a part.
"The upwelling that we normally expect in the springtime hasn't kicked in,'' said Frank Schwing, a NOAA oceanographer in Pacific Grove.
"We think there might be real consequences for the seabirds, fish and mammals.''
On the Farallon Islands, krill-eating Cassin's auklets are producing only a few chicks this year. Common murres, although plentiful in numbers, for the most part can't find the rockfish to keep their young alive.
Many scientists believe that the years of 2005 and 2006 should have been cold ones in the California Current, the band of coastal water from Baja California to British Columbia, according to calculations of naturally alternating cold and warm periods over the past millennia.
By now, the offshore waters should be roiling with plankton and the shrimp-like krill, the foundation of the ocean's food chain. Instead, the researchers say, the organisms appear to be in short supply.
Oceanographers are scratching their heads over the brand-new data. While they believe that global warming may be throwing off natural climate regimes, they don't know how the warming might eventually affect the California Current.
"Is it just natural variability of the climate or is it part of the brave new world that we associate with global climate change?'' Schwing said.
The white-bellied gray Cassin's auklets signal potential disaster for some species of seabirds, an early indicator of the ocean's health. The birds are abandoning their Farallon nests, a sign that they can't find enough krill.
Russ Bradley, a PRBO Conservation Science biologist who monitors birds on the islands, called 2006 "an incredibly poor year'' for the stocky robin-sized bird. Its numbers have declined to 25,000 in 2004 from about 105,000 in 1972.
The penguin-like common murres, which number more than 200,000, apparently haven't been able to locate the small rockfish they feed their hatchlings. On this largest murre colony south of Alaska, researchers see parent birds trying unsuccessfully to stuff anchovies three times the size of baby rockfish into hungry mouths.
Rockfish counts are the lowest in 24 years of NOAA monitoring by offshore vessels, meaning that the fish stocks for Pacific snapper and other rockfish may be low in 2008 to 2012 when they would come to market. The inch-long krill is also turning up low numbers, report NOAA scientists.
The California ocean system is fed by both transport of colder, rich waters from the North Pacific and upwelling of deep sea life-filled cold waters. Only recently, scientists determined that warm and cold periods have alternated for thousands of years according to 15- to 20-year cycles called climate regimes, in part driven by the currents from the North Pacific and changes in atmospheric pressure and the direction of winter winds.
In this scheme, this should be a cold period.
But this winter, like last, the cold waters harboring nutritious krill, copepods and other zooplankton didn't come from the North Pacific. And in the timing of ocean life, that's when the spawned rockfish larvae and other organisms needed them.
In spring, the normal upwelling of nutrients that promote growth of the phytoplankton, the tiny plants that feed the zooplankton, petered out in late May in the California Current. The upwelling could restart but it would be too late for the auklets and the rockfish.
"The years 2005 and 2006 have been awful,'' said Steve Ralston, a NOAA supervisory research fishery biologist in Santa Cruz, who returned this week from a 40-day vessel cruise from Cape Mendocino to San Diego.
The average catch rate of 100-day-old shortbelly rockfish was 24 per trawl over the past quarter century. In May and June 2005, the average rate was 0.15 fish per trawl, the lowest on record. This year is comparable to 2005, he said.
"We're getting El Niño-like conditions in non-El Niño years,'' Ralston said.
In El Niño years, the California Current is influenced by the powerful short-term fluxes of warm water that are precipitated by a failure of trade winds at the equator. But such an oceanwide effect hasn't been seen.
"If you throw snake-eyes in craps two times in a row, what can you say? Is it bad luck or is that the way it is?'' Ralston asked.
In Newport, Ore., another NOAA oceanographer, Bill Peterson, has found low numbers of copepods, tiny crustaceans and krill in the 2006 counts. But upwelling started up last weekend and may improve numbers, he said.
A NOAA team in the Pacific Northwest is now searching for juvenile salmon as part of the current count. Preliminary results show that the numbers are better than last year, Peterson said.
It's also too early to tell the biological effects on the krill-eating blue whales and humpbacked whales.
"If it turns out that the entire California Current is having a real low year, there probably could be an effect on a whale population,'' said Steve Reilly, director of the protected resources division in NOAA.
Scripps Institution of Oceanography biologist John McGowan, who started studying ocean conditions more than 50 years ago, said Thursday that there was "a great deal of disruption going on in food webs and it's climate related.''
"The carbon dioxide in the atmosphere right now is sufficient to keep trapping heat for a good many years into the future even if we don't put any more into the atmosphere,'' he said, citing the imbalance between the amount of heat coming in from the sun and the amount of heat going out into space.
"The California Current goes up and down like the stock market, but the ups and down are warmer,'' McGowan said, "and there's a long-term trend upward just as there is in the stock market.''