maybe i can try this...

i think we get the idea that if it's warming faster in the arctic then maybe that warmth can jump into the atmosphere, and split the vortex in half. it answers the question: where did the heat come from? i grasp this is easy to make sense of, it's just that the proposed physics of taking the heat from the land to the sky are getting a big thumbs down from the physicists, themselves.

but, you can at least make sense of a mechanism. what does it have to do with the sun?

well, it's kind of the opposite idea. every single winter, the vortex expands. but, this is a confusing way to state it, as the vortex does not expand so much as what was keeping it bottled up retreats. in physics, cold isn't actually a thing, but the absence of a thing, namely energy. so, the cold air doesn't expand; the hot air retreats. this isn't actually quite as simple as a reduction in sunlight, but it kind of is, though, yeah.

if the vortex expands far enough, it could break. it's less like pulling an elastic band apart and more like ripping a piece of bread in half. but, this would actually be a consequence of less energy in the atmosphere.

the air in the middle, where it's broken apart, would then be warmer because it's rushing in from all sides. you could imagine that being something more like ripping a bag of potato chips open. calling it "sudden warming" would then also be misleading, as it's really more of a sudden rushing.

we don't know which idea is right, yet. we know the mechanism for one of them is fishy, and we don't have definitive data for the other one, yet.