Contributed by: filbert Thursday, November 15 2007 @ 07:24 PM CST
A team of NASA and university scientists has detected an ongoing reversal in Arctic Ocean circulation triggered by atmospheric circulation changes that vary on decade-long time scales. The results suggest not all the large changes seen in Arctic climate in recent years are a result of long-term trends associated with global warming.
The team, led by James Morison of the University of Washington’s Polar Science Center Applied Physics Laboratory, Seattle, used data from an Earth-observing satellite and from deep-sea pressure gauges to monitor Arctic Ocean circulation from 2002 to 2006. They measured changes in the weight of columns of Arctic Ocean water, from the surface to the ocean bottom. That weight is influenced by factors such as the height of the ocean’s surface, and its salinity. A saltier ocean is heavier and circulates differently than one with less salt.
The very precise deep-sea gauges were developed with help from the National Oceanic and Atmospheric Administration; the satellite is NASA’s Gravity Recovery and Climate Experiment (GRACE). The team of scientists found a 10-millibar decrease in water pressure at the bottom of the ocean at the North Pole between 2002 and 2006, equal to removing the weight of four inches of water from the ocean. The distribution and size of the decrease suggest that Arctic Ocean circulation changed from the counterclockwise pattern it exhibited in the 1990s to the clockwise pattern that was dominant prior to 1990.
Reporting in Geophysical Research Letters, the authors attribute the reversal to a weakened Arctic Oscillation, a major atmospheric circulation pattern in the northern hemisphere. The weakening reduced the salinity of the upper ocean near the North Pole, decreasing its weight and changing its circulation.
“Our study confirms many changes seen in upper Arctic Ocean circulation in the 1990s were mostly decadal in nature, rather than trends caused by global warming,” said Morison.
“While some 1990s climate trends, such as declines in Arctic sea ice extent, have continued, these results suggest at least for the ‘wet’ part of the Arctic – the Arctic Ocean – circulation reverted to conditions like those prevalent before the 1990s,” he added.
The Arctic Oscillation was fairly stable until about 1970, but then varied on more or less decadal time scales, with signs of an underlying upward trend, until the late 1990s, when it again stabilized. During its strong counterclockwise phase in the 1990s, the Arctic environment changed markedly, with the upper Arctic Ocean undergoing major changes that persisted into this century. Many scientists viewed the changes as evidence of an ongoing climate shift, raising concerns about the effects of global warming on the Arctic.
It shouldn’t be long before the climate change zealots figure out how to argue that this non-global-warming related phenomenon is caused by global warming.
The fact is that we do not have a good understanding of how the overall climactic system of the Earth works. The computer models which are the core of the alarmist camp’s arguments are just that–simplified computer models which make a whole raft of assumptions about how the Earth’s climate operates. Not all of those assumptions are necessarily so.
Is is smart to get off of hydrocarbons and to generally conserve energy? Of course. But claiming that disaster is right around the corner is, to be blunt, not supported by the science.