In a report released February 6, NOAA scientists report the ocean circulation system has been slowing down since the mid-1970?s, causing an increase in ocean surface temperatures along the Equator in the Pacific Ocean and a decrease of carbon dioxide released into the atmosphere.
According to NOAA, ?These circulation changes are linked to the shifts in the climate of western North America, and can affect Pacific fisheries. They may be part of the naturally occurring ocean and atmosphere phenomenon called the Pacific Decadal Oscillation, which has a roughly 50-year cycle. But they also could be influenced by greenhouse gases.?
According to Michael McPhaden, a senior research scientist at NOAA?s Pacific Marine Environmental Laboratory in Seattle, ?Looking back at records for the past 50 years, we found that the ocean currents flowing in the north-south direction have been slowing down in the tropical Pacific Ocean since the mid-1970s.?
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David Stauth has posted a story on the Oregon State University website, based on research done by OSU professor of geosciences Peter Clark, saying that one of the odd possibilities that could emerge from global warming is that much of Europe, robbed of the ocean current patterns that help keep it warm, could abruptly enter a deep freeze and have a climate that more closely resembles Alaska than the modest temperatures it now enjoys.
Researchers from Oregon State University have explored this potential phenomenon, and the fluctuations in ocean currents that could trigger it. It?s by no means certain that climatic changes of this magnitude and speed will come to pass, but even the reasonable possibility that they might is a cause for concern.
?To answer difficult questions such as this we depend a lot on our computer models, and in this area different models reach different conclusions,? says Peter Clark, one of the world's leading experts on glaciers and prehistoric climate changes. ?What is fairly clear is that if the ocean circulation patterns that now warm much of the North Atlantic were to slow or stop, the consequences could be quite severe. This might also happen much quicker than many people appreciate. At some point the question becomes how much risk do we want to take??
The big variable is whether changes in global temperature and rainfall patterns might affect a gigantic conveyor belt of warm, less-salty surface water that moves from the tropical Atlantic Ocean until it finally becomes so cold and salty in the far north Atlantic that it sinks, moves south and continues the circulation pattern. This process, called thermohaline circulation, only happens in two regions of the Earth's polar areas. But it is responsible for much ocean circulation, including the critical currents that help keep parts of North America and Europe far warmer than they would otherwise be, considering the far north latitudes at which they lie. Most of Great Britain is at the same latitude as central Canada and would otherwise have the same kind of weather.
The circulation process that keeps Europe warm is not inevitable. Research suggests it may have fluctuated or even stopped numerous times in Earth?s distant past, and it?s especially sensitive to moderate increases in temperature or influxes of fresh water. The same very cold, very salty water that sinks in the far North Atlantic Ocean won?t sink if it?s just a little bit warmer or a little bit less salty. It appears these changes have happened before and the change took place suddenly?not in thousands of years but in decades.
?This system does not respond in what we call a linear manner,? Clark says. ?Once you start putting on the brakes, this circulation pattern could slow down faster and faster and eventually stop altogether.?
Research has found that some of the Earth?s most rapid climatic shifts of up to 15 degrees in decades or less have occurred in the past during glacial periods, when large ice sheets advanced from the polar regions as far south as New York City. Some scientists have theorized that the wild temperature fluctuations of the last ice age may have retarded the evolution and development of humans as a species, as they struggled to cope with rapidly changing conditions.
We are now in an ?interglacial? period that may have less volatility, but could also be coming to an end.
Global warming will simply delay the inevitable, Clark says, because it?s about time for Earth to enter its next ice age. There?s a fairly well-defined pattern on Earth of about 10,000-year-long interglacial periods followed by 90,000-year-long ice ages, and the current interglacial period is already more than 10,000 years old.
?At this point we just aren?t sure what to expect in terms of climatic volatility,? Clark says. ?But the more we learn about them, it becomes clear that these thermohaline circulation patterns are quite sensitive to temperature and influxes of fresh water, such as you might get with changing precipitation patterns triggered by global warming, not to mention melting ice caps or glaciers.?
The surprise is that the same greenhouse effect that makes the Earth warmer could have the opposite effect on much of Europe by slowing or shutting down the warm ocean circulation patterns on which it depends.
The collapse of the thermohaline circulation patterns that dictate Europe?s climate has raised so much concern that Great Britain recently launched a $40 million research program to analyze this phenomena and its possible implications. And the National Academy of Sciences recently issued a report about the ?inevitable surprise? of ?climate changes with startling speed.?
To learn more about this, read ?The Coming Global Superstorm? by Whitley Strieber and Art Bell, now in paperback at all bookstores. It will soon be made into both a television and feature film.
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