This short article from Maclean’s describes the Canadian Shift:
http://www.macleans.ca/society/life/in-the-midst-of-the-canadian-vowel-shift/
More details can be found in the Wikipedia entry:
https://en.wikipedia.org/wiki/Canadian_Shift
or in this article:
http://www.meredithtamminga.com/documents/CLA2008_Sadlier-Brown_Tamminga.pdf