Climate scientists are warning that a disruption to the polar vortex could inflict one of the harshest winters for decades as it sweeps the US East coast later this month.
Judah Cohen, a climate researcher at Atmospheric and Environmental Research, says that a polar vortex disruption, which could hit by the end of December or start of January, would be the “single most important determinant of weather this winter”.
A polar vortex disruption occurs when the stratosphere suddenly warms, causing winds to decrease or change direction. Research suggests Sudden Stratospheric Warming (SSW) events become more prevalent as solar activity declines. Our sun is currently going through one of deepest solar minimums in over 100 years, with solar cycles 24 and 25 likely ushering in the start of the next Grand Solar Minimum (for more on that click here).
“Confidence is growing in a significant Polar Vortex disruption in the coming weeks.” Dr Cohen tweeted. “This could be the single most important determinant of the weather this winter across the Northern Hemisphere.”
When the vortex is stable, winter conditions over the United States and Europe tend to be rather ordinary. But when the vortex is disrupted, an ordinary winter can suddenly turn severe and memorable for an extended duration. “[It] can affect the entire winter,” Cohen said in an interview.
Rewind to February of last year to understand the implications. Up to that point, the vortex had held in its stable state, and the winter was a mild, unremarkable one. But then, abruptly, the vortex split.
The fracture set off a chain reaction, which first unleashed a punishing blast of cold in Europe and Asia. The media dubbed the cold snap the “beast from the east” as frigid Siberian air flooded the continent.
Then, the piercing cold hit the Lower 48 states in March. It triggered four consecutive nor’easters along the East Coast, where the polar air collided with the relatively mild Atlantic waters.
Its effects lasted weeks. “We were still feeling the impacts into the end of April,” Cohen said.
Polar vortex disruptions appear to be on the increase — they have defined the character of several other recent winters, including 2009-2010, the snowiest on record in parts of the Mid-Atlantic, and 2013-2014, which was abnormally cold, especially in the Great Lakes.
Research shows blocking persistence increases when solar activity is low, causing weather patterns to become locked in place at high and intermediate latitudes for prolonged periods of time.
During a solar minimum, the jet stream’s usual Zonal Flow (a west–east direction) reverts to more of a Meridional Flow (a north-south direction).
This is exaggerated further during a Grand Solar Minimum, like the one we’re likely entering now, and explains why regions become unseasonably hot or cold and others unusually dry or rainy, with the extremes lasting for an extended period of time.
Mikhaël Schwander, et al, 2017 — “The zonal flow characteristic of westerly types is reduced under low solar activity as the continental flow for easterly and northerly types is enhanced. This is also confirmed by the higher blocking frequency over Scandinavia under low solar activity.”
And the paper goes further:
“The 247-year-long analysis of the 11-year solar cycle impact on late winter European weather patterns suggests a reduction in the occurrence of westerly flow types linked to a reduced mean zonal flow under low solar activity. Based on this observational evidence, we estimate the probability to have cold conditions in winter over Europe to be higher under low solar activity than under high activity.”— Mikhaël Schwander, et al, 2017
Disruptions to the jet stream and SSW events are the new darling of the Global Warming camp. However, the scientific community has been comfortable with the ‘natural’ mechanisms for decades — as this article from 1975’s Science News would indicate:
The cold times have returned.
Cut some wood.
Grand Solar Minimum