Interesting. I just read a bit about it, and it can happen when a less dense warm air mass passes above a more dense cold air mass. The normal circumstances wouldn’t seem to produce something of the magnitude you are talking about though. Then I read these sentences:
“An inversion is also produced whenever radiation from the surface of the earth exceeds the amount of radiation received from the sun, which commonly occurs at night, or during the winter when the angle of the sun is very low in the sky. This effect is virtually confined to land regions as the ocean retains heat far longer. In the polar regions during winter, inversions are nearly always present over land.”
Ok, so what if an event causes an unheard of drop in the amount of solar radiation received from the sun? For example, if the upper atmosphere was suddenly choked with light colored particles creating a more reflective albedo effect? I’m thinking supermassive volcanic eruption or something of that nature. Air circulation patterns mean that the poles would be the last place for the dust to disperse to. If the dust from the larger volume of air near the middle of the planet concentrated in the smaller volume at the poles, packing the dust in tighter, combined with already lower temps at the poles, you could see a significantly colder inversion than in other regions.
And the evidence is becoming almost undeniable that a large comet or small asteroid struck North America about 12,500 years ago, and it was an Earth-changing event.