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Why polar bears may follow the sunspots.

Why polar bears may follow the sunspots

Most scientists cringe at suggestions that the 11-year sunspot cycle might influence bizarre factors on Earth, such as the number of polar bears hunted down each year. But a new study adds an intriguing twist to the polar bear proposal. Two researchers report finding a statistical link between the sunspot cycle and the severity of winter sea-ice near Newfoundland since the 1920s.

In some years, southerly winds blow an abnormal amount of Arctic sea-ice southward to Newfoundland, causing problems for shipping, fishing and oil-drilling efforts in the area. In other years, the ice is much less severe. Brian T. Hill and Stephen J. Jones of the Institute for Marine Dynamics in St. John's, Newfoundland, say their statistical studies of sea-ice records suggest that such variations follow the solar cycle -- a small waxing the waning of the sun's energy output, with an average period of about 11 years. They describe their findings in the April 15 JOURNAL OF GEOPHYSICAL RESEARCH.

The statistical link between ice and solar cycle appears strongest, they say, when the calculations take into account another factor called the quasi-biennial oscillation (QBO) -- a pattern of stratospheric winds circling Earth's tropics and reversing direction about every 1 to 1-1/2 years. The researchers found the best match between ice severity and solar variations during years when the stratospheric winds blew from the west. In the last three years, several scientists have described similar statistical links between the solar cycle and Earth's weather patterns during the westerly phase of the QBO (SN: 5/14/88, p.310).

Hill and Jones suggest that periods of strong solar activity could somehow set up patterns of high air pressure that keep sea-ice from blowing south toward Newfoundland. If so, the polar bear link could make some sense, Hill speculates, because years of mild sea-ice might restrict the bears' travels.

Statistical correlations between solar cycle and variations on Earth, while tantalizing, remain quite controversial. Meteorologists can't currently explain how minute changes in the sun's radiation could cause such large variations in Earth's weather.
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Publication:Science News
Date:May 19, 1990
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