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Earth Sense: Jet stream could bring more droughts

POSTED: April 7, 2013 1:00 a.m.

The sea ice in the Arctic is dwindling. NASA just posted images of a gigantic crack in the frozen cover.

The North Pole, and the Arctic around it, isn’t a land mass like the South Pole. It’s an ocean, with a relatively thin layer of ice on top. The ice pack on the Arctic Ocean has been decreasing since the late 1970s, and 2012 marked an all-time low since measurements began.

Experts are unsure what it means exactly in terms of climatic change and the weather we can expect in the years to come. The simplest way to picture it is to imagine the ice pack as a huge curbstone. The jet stream, which is the “fast lane” of airflow at high altitude, is forced to curve around it. With less ice in the way, the jet stream weakens and also shifts north. This allows for warmer masses of air from the south to make it farther north than they usually do, bringing lots of moisture from the subtropical oceans in the process. Some publications blame the melting of Arctic ice for the heavy snow loads that we’ve recently seen in New England, and especially in Europe.

Anchoring effects in the jet stream have been observed for a long time. For example, the Rockies force it to curve northward. On the Eurasian continent, world’s highest mountains, the Himalayas, anchor it to their south in winter and north in the summer.

The position of the jet stream plays a great role in determining where precipitation occurs, because it steers the large continental storm systems. For Georgia, this doesn’t mean that we can expect winter wonderland during the next few cold seasons. More ominously, a weakening and northward shift of the jet stream could have dire consequences during summer season. Large rain systems, which are rare enough during Georgia summers, would be largely absent from our area. And with the jet stream out of the way, the Bermuda High, a huge mass of dry, sinking air off the U.S. East Coast, could spread even deeper into the Southern states than it has in the past.

The result of such a shift is drought, stronger and more persistent than the droughts that have already troubled us in past decades. Even before definitive answers are available, it makes more sense than ever to focus on water conservation and management in the greater Atlanta area.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.


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