Do you have a link that says what you are saying?What you are supposed to know, but apparently do not, is that the center bottom of the Atlantic is the fault that pushes NA and Greenland...
The North American plate is moving to the west-southwest at about 2.3 cm (~1 inch) per year driven by the spreading center that created the Atlantic Ocean, the Mid Atlantic Ridge.
There will be a "closest to the pole" moment for Greenland too. NA passed that point 20-25 million years ago, and when it did, it started moving on the vector it currently has, away from the pole. Before that, NA was, like Greenland is, moving NW and towards the pole.
That 600 miles to the pole line is indisputable truth. Greenland and Ellesmere in ice age. Everything else is more than 600 miles from the pole and hence NOT in ice age. The end of the North American Ice Age was quite recent, within the past 10-20k years. But just like Greenland, it started when NA got to 600 miles to the pole, and looked different before being scraped off for 30-50 million years...
One artist attempt, wrong because NA and Greenland are connected in the photo, but in reality never were...
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