In the summer you can see just how rugged a glacier is, while in the winter it looks smooth covered in many feet of snow. But for the ice to build the snow has to last year round, which it hasn't done below 5 or 6 thousand feet. So the ice slides down the gorge and out into the valley, melting all summer long. The ice is built only up above in the year round snow fields. So, no the glaicers are not built back up each winter. Mount McKinley rising over the Ruth Glacier, 'the gateway' and 'the great gorge', Denali National Park, summer, Alaska.