Washington Deserts in the American Southwest and around the globe are creeping toward heavily populated areas as the jet streams shift, researchers reported Thursday.
The result: Areas already stressed by drought may get even drier.
Satellite measurements made from 1979 to 2005 show that the atmosphere in the subtropical regions north and south of the equator is warming. As the atmosphere warms, it bulges out at the altitudes where the northern and southern jet streams slip past like swift and massive rivers of air. That bulging has pushed both jet streams about 70 miles closer to the Earth's poles.
Because the jet streams mark the edge of the tropics, in essence framing the hot zone that hugs the equator, their outward movement has allowed the tropics to grow wider by about 140 miles. That means the relatively drier subtropics move as well, pushing closer to places like Salt Lake City, where Thomas Reichler, co-author of the new study, teaches meteorology.
Details appear today in the journal Science.
Reichler suspects global warming is the root cause of the shift, but said he can't be certain.