Blue Iceberg, Upsala Glacier, Argentina - by Ricardo Bevilaqua.
Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of a glacier. During its travels, all of the air bubbles that are trapped in the ice are squeezed out, and the size of the ice crystals increases, making it clear. The ice is blue for the same reason water is blue. Namely, it is a result of an overtone of a OH molecular stretch in the water which absorbs light at the red end of the visible spectrum.