Researchers See Reversal in Arctic Patterns

A team of climate researchers has discovered a reversal in circulating Arctic Ocean currents that indicates some of the polar region's recent changes may be periodic, rather than attributable to global warming.

Don't get too excited. The ice is still melting at unprecedented rates; and if that goes on, anybody reading this in a coastal town had better start thinking about trading in their SUV for a hydrogen-powered jet ski.

But many scientists had associated changes in regional ocean circulation patterns, most notably a post-1990 change from clockwise to counterclockwise, with the threat of broader climate shifts. Now it appears that short-term fluctuations may occur, on the time scale of a single decade.

"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 [University of Washington applied physicist
James] 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 team used data from deep-sea water pressure gauges, and from NASA's
Gravity Recovery and Climate Experiment (GRACE) satellite, which measures tiny changes in the Earth's gravity field caused by movement of water.

They attribute the re-reversal of ocean currents to a weakening Arctic
Oscillation, a major atmospheric circulation pattern in the northern hemisphere. This had been stable until about 1970, after which it varied substantially until about 1990, when it stabilized again. The most recent changes have apparently helped reduce the salinity of the upper ocean near the North Pole, decreasing its weight, and changing its circulation, the scientists said.

The researchers have published their results in Geophysical Research Letters.

NASA Sees Arctic Ocean Circulation Do an About-Face [NASA JPL]

(Image: Along with satellite data, the team used data produced by water pressure recorders installed at the bottom of the Arctic Ocean. Credit:
JPL)