Apparently
the intense curve of the jet stream can predict the variability of an entire
season and it is part of a 4,000 year pattern. Last winter”s curvy jet stream in North
America resulted in mild western temperatures and harsher cold temperatures in
the east. University of Utah researchers reveal that a similar pattern became
more pronounced 4,000 years ago, suggesting that it may worsen as Earth”s
climate warms.
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According to geochemist Gabe Bowen, senior author of the study, “If
this trend continues, it could contribute to more extreme winter weather events
in North America, as experienced this year with warm conditions in California
and Alaska and intrusion of cold Arctic air across the eastern USA.”
“A
sinuous or curvy winter jet stream means unusual warmth in the West, drought
conditions in part of the West, and abnormally cold winters in the East and
Southeast,” adds Bowen. “We saw a good example of extreme wintertime
climate that largely fit that pattern this past winter,” although typically
California is wetter.
The researchers note that scientists have already linked “Greenhouse”
gases to the current warming of the Earth’s climate and increased weather
extremes predicting the likelihood of their continuance.
But
the new study shows that the North American jet stream pattern for wintertime
weather extremes is millennia old — “a longstanding and persistent pattern
of climate variability,” Bowen says. Yet global warming may enhance the
pattern making winter weather extremes more frequent or severe or both.
“This is one more reason why we may have more winter extremes
in North America, as well as something of a model for what those extremes may
look like,” Bowen says. Human-caused climate change is reducing
equator-to-pole temperature differences; the atmosphere is warming online casino more at the
poles than at the equator. Based on what happened in past millennia, that could
make a curvy jet stream even more frequent and-or intense than it is now, he
says.
Bowen and his co-authors analyzed previously published data on
oxygen isotope ratios in lake sediment cores and cave deposits from sites in
the eastern and western United States and Canada. Those isotopes were deposited
in ancient rainfall and incorporated into calcium carbonate. They reveal jet
stream directions during the past 8,000 years, a geological time known as middle
and late stages of the Holocene Epoch.
Next, the researchers did computer modeling or simulations of jet
stream patterns — both curvy and more direct west to east — to show how changes
in those patterns can explain changes in the isotope ratios left by rainfall in
the old lake and cave deposits.
Read more at the University
of Utah.
Winter
covered home image via Shutterstock.