What is a polar vortex and why is it hitting us?

CINCINNATI -- Stepping outdoors in the Tri-State Monday and Tuesday was akin to walking into a freezer.

Wind chills reached into the -30s and Cincinnati tied its record low temperature Monday evening set in 1924 for Jan. 6 at -7 degrees.

The cause? Experts say we’re the victims of a polar vortex.

But what really is this weather phenomenon and how is it bringing these super cold temperatures to so much of the U.S.?

According to CNN , a polar vortex is the circulation of strong, upper-level winds that normally surround the North Pole in a counterclockwise direction. These winds keep the bitter cold air locked away in the Arctic regions of the Northern Hemisphere and away from the U.S. 

This cold air reaches us when the vortex becomes distorted and dips much farther south than normal, allowing cold air to spill southward. 

The Washington Post weather editor Jason Samenow described a polar vortex as a “a low-pressure center” that “at times, will slip its tentacles southward and bring cold air outbreaks into the U.S., but this year, we're seeing a huge chunk of it, most of it descending into the U.S."

This leak of cold air is known as the Arctic Oscillation and it can switch from a positive phase to negative phase a few times per year. This oscillation -- namely the negative phase where the polar winds are weaker -- tends to lead to major cold air outbreaks in North America, Europe and Asia.

The big question that is being debated is whether global warming is responsible for this vortex oscillation and extreme cold.

Experts at CNN had this to say:

In short, yes, it could be. It seems counterintuitive that global warming could cause significant cold snaps like this one, but some research shows that it could. We know that different types of extreme weather can result from the overall warming of the planet, melting of the Arctic Sea ice, etc. This includes extreme distortions of the jet stream, which can cause heat waves in summer and cold snaps in winter.”

Scientific American said:

"More and more Arctic sea ice is melting during summer months. The more ice that melts, the more the Arctic Ocean warms. The ocean radiates much of that excess heat back to the atmosphere in winter, which disrupts the polar vortex. Data taken over the past decade indicate that when a lot of Arctic sea ice disappears in the summer, the vortex has a tendency to weaken over the subsequent winter."

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