With a melted Arctic sea route, control over the Arctic becomes incredibly strategic. It becomes most optimal shipping route in the world and quickly connects Europe, Asia, and North America. You really want to have your navy there.
China covets Taiwan because of naval strategy more than any other reason. This is the same reason America wants Greenland. It isn't Trump that wants it so bad, it's the DoD.
Look at China's posture on and dealings with Greenland. They really want to be there, and for good reason.