[5] Ocean Stays Cool, But pH is Dropping
Researchers who spend most of their time bobbing about on the deep Pacific have returned to their home ports with some good and bad news.
On the issue of sea water warming, there seems to be little of it going on. In fact, scientists who deployed a huge array of 3,000 robotic buoys throughout the world's oceans say the waters have not warmed for the past four years.
These drifting buoys are programmed to descend to depths of several thousand feet, then rise and record data on temperature, salinity and velocity. Once they reach the surface, they send the information to a satellite. Then, they depart once more to the deep and do it all over again.
According to a report aired on National Public Radio earlier this spring, NASA Jet Propulsion Laboratory scientist Josh Willis said the buoy data actually showed a slight cooling trend in the oceans for the past four years.
In 2006, he and others published a report that said the buoy array showed significant cooling in the first two years of their data collection. Later, they corrected their findings because they found that two datasets used in their analysis were biased.
His results jibe with other news coming out on the climate front, including a paper published May 1 in Nature by Richard Wood, a British climate scientist. Wood described a newer climate model that predicts over the next decade, "natural climate variations in the North Atlantic and tropical Pacific oceans will temporarily offset the projected anthropogenic warming: surface temperatures in Europe and North America may even cool a little during this period."
Wood and others since then have pointed out this is only a temporary situation, and eventually, CO2 levels will lead to sharp increases in global temperatures out 20 years or so.
CO2 may be affecting oceans already. Another group of scientists has found high levels of acidified ocean water for the first time off the West Coast, according to a May 22 report in Science Express, written by Richard A. Feely and Christopher Sabine, both oceanographers at NOAA's Pacific Marine Environmental Laboratory in Seattle.
They say the increasing acidity comes from increasing levels of CO2 absorbed by the oceans.
"Our findings represent the first evidence that a large section of the North American continental shelf is seasonally impacted by ocean acidification," said Feely, in a May 22 NOAA press release. "This means that ocean acidification may be seriously impacting marine life on our continental shelf right now."
Burke Hales, an associate professor in the College of Oceanic and Atmospheric Sciences at Oregon State University and co-author on the Science study, said water upwelled in recent years was last at the surface about 50 years ago and "was exposed to an atmosphere with much less CO2 than today, and future upwelled waters will probably be more acidic than today's because of increasing atmospheric CO2."
He said there was a strong correlation between recent hypoxia events off the Northwest coast and increasing acidification.
"The hypoxia is caused by persistent upwelling that produces an over-abundance of phytoplankton. When the system works, the upwelling winds subside for a day or two every couple of weeks in what we call a 'relaxation event' that allows that buildup of decomposing organic matter to be washed out to the deep ocean.
"But in recent years, especially in 2002 and 2006, there were few if any of these relaxation breaks in the upwelling and the phytoplankton blooms were enormous," Hales added. "When the material produced by these blooms decomposes, it puts more CO2 into the system and increases the acidification."
The scientists said they did not expect to see this extent of ocean acidification until the middle to the end of the century.
Cooler oceans may also play a role in increasing populations of jellyfish off the coast, according to a recent paper by NOAA Fisheries scientist Richard Brodeur. In another report soon to be published, Brodeur and his co-authors found that jellyfish and salmon do not seem to share much of the same turf, but jellyfish do seem to compete for the same types of plankton as sardines, anchovy, saury and herring, which in turn are important prey species to salmon diets.
Back in April, JPL scientists said the powerful La Niña that has cooled West Coast waters was slowly weakening, but was still very much in evidence, according to sea-level height data collected by the U.S.-French Jason oceanographic satellite, and packed extra punch from the cool PDO phase the region is now in.
"The comings and goings of El Niño, La Niña, and the Pacific Decadal Oscillation are part of a longer ongoing change in global climate," said JPL scientist Willis. "In fact, these natural climate phenomena can sometimes hide global warming caused by human activities. Or they can have the opposite effect of accentuating it." -B. R.
The following links were mentioned in this story:
NPR, The Mystery of Global Warming's Missing Heat
Nature 453, Climate change: Natural ups and downs
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