Why? Blue snow in Hoboken?

Been meaning to mention this… Did you notice that after one of our bigger storms this year – that we had a very unusual blue snow phenomenon?

Maybe I was the only one fascinated with nature (much less than social networking blabber), but it was definitely not a common occurrence. See below for an explanation!

Blue snow in Hoboken NJ scientific explanation

Blue Snow not blue for reasons you think

The picture displayed here were hard to find because most snow mounds in Hoboken become quickly disturbed or dirtied by footsteps, road salt, dog poop or just plain garbage. You have to reach the outskirts of town to find a relatively clean pile of the white stuff.

Below is an explanation from seismologist Larry Gedney from the Geophysical Institute at the University of Alaska Fairbanks:

Blue Snow and Ice – WHY?

It is a common misconception that the blue color exhibited by glaciers, old sea ice, or even holes poked into a snow bank is due to the same phenomenon that makes the sky blue–light scattering. But nature has more than one recipe for producing the color blue. In frozen water and in the sky the processes are almost the reverse of each other.

A blue sky results when light bounces off molecules and small dust particles in the atmosphere. Because blue light scatters more than red does, the sky looks blue except in the direction of the sun (particularly when the sun is near the horizon and the blue light is scattered out of the sunlight, leaving the red color of sunrises and sunsets).

When light passes through ice, however, the red light is absorbed while the blue is transmitted. Were the operating process scattering as in the atmosphere, then the transmitted light would be red, not blue. However, because of the large size of snow grains and ice crystals, all wavelengths of visible light are scattered equally. Scattering therefore does not play an appreciable role in determining the color of the transmitted light.

Trippy blue snow as seen in Hoboken NJ

It takes an appreciable thickness of pure ice to absorb enough red light so that only the blue is transmitted. You can see the effect in snow at fairly shallow depths because the light is bounced around repeatedly between ice grains, losing a little red at each bounce. You can even see a gradation of color within a hole poked in clean, deep snow. Near the opening, the transmitted light will be yellowish. As the depth increases, the corer will pass through yellowish-green, greenish-blue and finally vivid blue. If the hole is deep enough, the color and light disappear completely when all the light is absorbed.

The color of ice can be used to estimate its strength and even how long it has been frozen. Arctic Ocean ice is white during its first year because it is full of bubbles. Light will travel only a short distance before it is scattered by the bubbles and reflected back out. As a result, little absorption occurs, and the light leaves with the same color it had when it went in.

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.

Arctic explorers and mountain climbers know that old, blue ice with fewer bubbles is safer and stronger than white ice. An added bonus for explorers is knowing that floating camps built on blue ice will last longer.