Year round gardening in sub arctic climates may not be worth the effort. You are better off preserving your harvest rather than fighting winter with a lot of energy. Extend the growing season, select appropriate plants and plant where plants want to be and keeping the fresh like qualities of your garden harvest are some of these better options. This page gives you reference to many ways you can keep your harvest; root cellars, canning, pickling and freezing. are discussed below.
Some information sources
Canning:
At growing a greener world click here
Bell cannon lessons click here
Canning 101youtube click here
Pickling
Pickling dill cucumbers click here
Quick pickling veggies click here
Sauerkraut instructions click here
Freezing
General freezing instructions click here
Blanching timetable click here
Cool Storage
Storing potatoes click here
Alaskan root cellar click here