Antartica is building more ice than it is loosing and this has been confirmed by NASA, not that you need NASA to confirm if you know your Antarctic history. Back in the 1930 US Admiral Byrd(Spelling) built 3 radio towers down there. In the earl 1990's the tallest, 110 feet high, had only 7 feet protruding above ice. By very early 2000's it was totally covered and the ice levels were still rising.

As far as Artic history goes in the 1420's there were settlements and farms on the North Coast of Greenland and ships could circumnavigate the island. It is still not that warm up there.