Scientists blame record-breaking warm winter temperatures for Arctic oscillation, a global jet stream circling around the upper northern hemisphere and holding cold air around the North Pole
- Climate researchers say that the Arctic oscillation has kept the winter temperatures high
- The AO is a ring of fast wind that circles around the Arctic
- During some periods the ring is transformed into a kind of sinusoidal shape
- This pushes colder air from the Arctic down over the rest of the hemisphere
- The jet stream is currently in a flatter ring shape that traps the cold air
The record-breaking temperatures in January appear to be caused by shifts in the Arctic oscillation, a wavy ring of powerful wind circling around the Arctic at around 20 degrees latitude.
Shifts in the AO have a direct impact on global weather by influencing how much cold air is pushed down from the Arctic and spreads throughout the rest of the northern hemisphere.
During the year, the Arctic oscillation varies in shape, due to differences in atmospheric pressure.
Record high temperatures in January seem to be linked to the Arctic oscillation, a band of wind circling around the northern hemisphere and holding cold air near the poles or pushing it down to the rest of the hemisphere
According to the National Scow and Ice Data Center in Boulder, Colorado, a research group on climate change, the unusually warm temperatures in January are probably due to an extensive positive phase of the AO
During a positive phase, the jet stream is a relatively flat air ring and during its negative phase, the wind band becomes much more uneven, resembling a sinusoidal curve.
The AO is currently in a positive phase, the NSIDC director Mark Serreze told NBC News keeps the colder air around the Arctic at bay.
This has not only kept the winter temperatures high, but has minimized the number of seasonal storms that the AO would otherwise cause during a negative phase, as large amounts of air collide with different pressures.
“Storms tend to develop along the jet stream and are guided through it,” Serreze said.
“What we see is that the polar current has shifted from the front ray to the north and that Arctic air has just been captured at great latitudes.”
During a negative phase (left), the jet stream around the Arctic becomes uneven and looks more like a sinus curve, leading cold air further down into the hemisphere. During a positive phase (right), the jet stream forms a tighter ring that holds air near the pole
According to Serreze, changes in Arctic oscillation are not easy to model or predict, making larger seasonal patterns difficult to predict.
“This is actually an area of active research, because if we could predict it, we could really improve the predictability of weather conditions in the longer term,” he said.
“If you could say in November that the coming winter is preferably in a positive phase, it would be valuable for aviation or cities that, for example, plan snowplow budgets.”
According to global averages, January was the hottest month in recorded history and the fifth hottest in American history
The relationship between regional weather and global climate phenomena such as the Arctic oscillation is still unclear, but scientists say that changes in one part of the world inevitably affect other parts of the world, although they say how not always easy
The exact relationship between the AO and global warming is not fully understood, but Serreze says that changes in one part of the planet inevitably have consequences for other areas.
“We are already seeing warming of the North Pole at too great a speed compared to the rest of the planet,” he said.
“If we change the temperature gradient between higher and lower latitudes, the jet stream will respond to it.”
WHAT IS THE POLAR VORTEX?
The polar vortex is an atmospheric circulation pattern that is high above the poles, in a layer of the atmosphere called the stratosphere.
This structure can weaken as a result of abnormal warming in the poles, causing it to disintegrate into smaller “sister swirls” that can travel outside of their typical range.
The cleavage higher in the atmosphere can ultimately cause a similar phenomenon to “drip” to the troposphere – the layer of the atmosphere closest to the surface where most of us occur again.
A split in the polar vortex can cause both sudden and delayed effects, many of which are accompanied by falling temperatures and extreme winter weather in the Eastern US along with Northern and Western Europe.