During a glacial maximum the increased amount of water locked up in ice shields results in lower sea levels, which in some places like Atlantic Canada makes for some pretty interesting geography. This map of the area c 11,000 BC shows most of the Maritimes and Newfoundland still under ice, but with large ice-free islands exposed on the Scotian Shelf and Grand Banks and a major iceberg calving channel running through the Gulf of Saint Lawrence.
This Geological Survey of Canada site has a series of maps covering the changes from 20,000 to 12,000 years ago, plus a sea-levels animation that pits rising water against rebounding land in a multi-millennial turf war. [Stephen Harper took it down.]
[This site for the Mi'kmawey Debert Cultural Centre has two sets of maps showing regional deglaciation and Minas Basin deglaciation.]