SOURCE: Science Daily
DATE: March 27, 2019
SNIP: When the Arctic warmed after the ice age 10,000 years ago, it created perfect conditions for drought.
According to new research led by a University of Wyoming scientist, similar changes could be in store today because a warming Arctic weakens the temperature difference between the tropics and the poles. This, in turn, results in less precipitation, weaker cyclones and weaker mid-latitude westerly wind flow — a recipe for prolonged drought.
The temperature difference between the tropics and the poles drives a lot of weather. When those opposite temperatures are wider, the result is more precipitation, stronger cyclones and more robust wind flow. However, due to the Arctic ice melting and warming up the poles, those disparate temperatures are becoming closer.
“Our analysis shows that, when the Arctic is warmer, the jet stream and other wind patterns tend to be weaker,” says Bryan Shuman, a UW professor in the Department of Geology and Geophysics. “The temperature difference in the Arctic and the tropics is less steep. The change brings less precipitation to the mid-latitudes.”
“The Nature paper takes a global approach and relates the history of severe dry periods of temperature changes. Importantly, when temperatures have changed in similar ways to today (warming of the Arctic), the mid-latitudes — particularly places like Wyoming and other parts of central North America — dried out,” Shuman explains. “Climate models anticipate similar changes in the future.”
Currently, the northern high latitudes are warming at rates that are double the global average. This will decrease the equator-to-pole temperature gradient to values comparable with the early to middle Holocene Period, according to the paper.