Photo Gallery: Extreme Ice Survey

Glaciers coat the valley north of Mont Blanc near Chamonix, France. At a length of 8 miles (12 kilometers), Mer de Glace, or Sea of Ice, is one of the largest glaciers in the Alps.

Estimates indicate the Alps have lost about half their glacial ice in the past century. And if climate change trends continue, they could lose 50 to 80 percent of their remaining glaciers by 2100.