From The Age of Consequences: The Foreign Policy and National Security Implications of Global Climate Change:
Tensions will increase between the United States and Canada, including clashes over fishing rights on both coasts. Two-thirds of Canadians rely on the Great Lakes (a relatively small watershed). Water levels are projected to decline by up to one foot in this century, attributable to increased evaporation, coupled with population growth. If the United States decides to divert water from the Great Lakes to compensate for the effects of climate change, the makings are in place for a fundamental clash of interests with Canada. There will also be an entirely new set of problems relating to navigation and resource rights, as the result of the opening of a northwest passage.
The passage concludes:
It cannot be excluded that Canada’s tensions with the United States will play into domestic issues affecting the stability of Canada itself: most notably, the western provinces’ new role as oil exporter.
...meaning, I suppose, that should it come to a U.S./Canada scuffle, who knows whose side Alberta will take?
This is one of the likely scenarios under "severe climate change". All in all a pretty grim read. One of the authors, incidentally, is John Podesta.