Trekking on a hot, sunny day looking up at craggy, black mountains we got to a high point and were met with an enormous glacier sliding down towards us. The width and height of it was awe inspiring and a completely new visual experience for me. So what were we looking at? The glacier in question was Glacier Grey situated in one of Patagonia's most well know National Parks, Torres del Paine.
The glaciers found in Patagonia are valley glaciers which are located in temperate glacial settings. There is little sea ice, no ice shelves, and no ice sheets. The minimum average temperatures are above 0°C and summer temperatures are higher than 10°C. Anyway enough of the science and onto the colour. Seems that it's all about light - The blue colour is caused by the absorption of red and yellow light, leaving the blue to shine through. The longer the path light travels in ice, the more blue it appears.
During the summer, the ice surface melts and new overlying ice layers compress the remaining air bubbles. Now, any light that enters travels a longer distance within the ice before it emerges. This gives the red end of the spectrum space enough to be absorbed, and the light returned at the surface is blue.