Another climate mystery – this time the QBO – for scientists to get their teeth into, as the Mail Online reports.
For more than 60 years, atmospheric scientists have observed the consistent behaviour of a wind pattern known as the ‘quasi-biennial oscillation’ – a phenomenon that repeats every 28 months. But in late 2015, the long-reliable pattern suddenly changed.
The winds have since returned to their normal course, and while no immediate effects were detected, astronomers are working to understand if this was just a one-time ‘black swan’ event, or a ‘canary in the coal mine’ signalling unseen conditions.
Scientists have measured the ‘quasi-biennial oscillation’ in the stratosphere since 1953, later coining its name in the 1960s. Over the course of roughly two years, winds in the tropical stratosphere circulate in easterly and westerly directions.
The westerly winds develop at the top, Nasa explains, and gradually make their way to the bottom. While this is happening, a layer of easterly winds takes the place above them, where they in turn descend and are replaced by westerlies.
Every 28 months, this pattern repeats. In late 2015, however, scientists noticed something different.
In this strange phenomenon, explained in a new paper published to Geophysical Research Letters, the researchers discovered that rather than allowing the easterly winds to descend, the westerlies appeared to move upward and block them.
This continued for nearly half a year, before returning to normal this past July. Researchers aren’t yet sure what this means, and are working to find out the significance of the disruption within a system that’s been consistent for so long.
‘The quasi-biennial oscillation is the stratosphere’s Old Faithful,’ said Paul Newman, Chief Scientist for Earth Sciences at Nasa’s Goddard Space Flight Center, Greenbelt, Maryland. ‘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.’
The stratosphere extends from roughly 10 to 30 miles above Earth’s surface, and the researchers say the quasi-biennial oscillation drives many of the conditions within this layer, including fluctuations in the ozone by 10 percent at the equator, between peaks of the easterly and westerly phases, and on levels of polar ozone depletion.
Researchers have proposed two possible explanations for this bizarre activity – this year’s El Niño, or the ongoing rise in global temperatures.
The team is studying the event to determine if it was simply a fluke, or if it could be a result of climate change with consequences that are yet to be known. And, they’re wondering what caused this anomaly, and if it will happen again.