Mysterious force disrupts wind currents in the stratosphere

For more than six decades, scientists have been monitoring a pattern of winds called the “quasi- biennial oscillation,” but recent disruptions unlike anything witnessed previously now has those researchers wondering if those changes will have an impact on the planet’s climate.

Chances are, you’ve never paid much mind to the quasi-biennial oscillation, and there’s a good reason for that, according to Paul Newman, the Chief Scientist for Earth Sciences at the NASA Goddard Space Flight Center in Maryland: for 60-plus years, it has followed the same cycle.

As Earth & Space Science News (EOS) explained, each cycle begins with strong westerly winds flowing through the stratosphere near the equator. Over the course of approximately 12 months, those winds gradually become weaker and descend to the lower part of the stratosphere. Easterly winds then replace them, until they begin to weaken and sink as well, after which time they will be replaced by westerly winds. The entire process lasts approximately 28 months.

First measured in 1953 and first named the quasi-biennial oscillation in the 1960s, this pattern of winds has followed its 28-month cycle like clockwork – until late 2015, that is, when scientists at Goddard observed the weakening westerly winds move back upwards instead of completing their decent, blocking the downward movement of the easterlies. This new pattern persisted for nearly six months before the old cycle seemed to return in July 2016.

Cause, potential lasting impact still to be determined, researchers say

Newman and his colleagues, who reported on the unusual sequence of events in the latest issue of the journal Geophysical Research Letters, said that there was no apparent immediate effect on the weather or climate as we experience it from Earth’s surface. Nonetheless, they were left with many questions, including what causes the sudden changes, and could it happen again?

“The quasi-biennial oscillation is the stratosphere’s Old Faithful,” Newman explained in a statement Friday. “If Old Faithful stopped for a day, you’d begin to wonder about what was happening under the ground… It’s really interesting when nature throws us a curveball.”

Now that they have detected the disruption, the NASA researchers are focused on trying to find the possible causes and the potential implications of this event. The quasi-biennial oscillation can have a significant effect on ozone levels at both the equator and the poles – in fact, they said that the phenomenon can cause as much as a 10% fluctuation in equatorial ozone layers.

Currently, Newman’s team has two hypotheses for what might have caused the unusual changes to the wind patterns: the El Niño of 2015-16, which was especially strong, or long-term increases in global temperatures. The scientists said that they are now working to determine if this was a once-in-a-lifetime fluke or a repeating/more permanent shift that could have a prolonged impact on the planet.


Image credit: NASA