Saturday, February 15, 2014

Plastic snow

Sastrugi - the sharp features of a windswept snow surface bordering fractured plates of ice in middle of photo.

When I was younger, I had one word to refer to all that white stuff in winter: snow. As I got older and had more experiences with it, particularly through snowboarding, I realized that not all snow is created equal. Snow taxonomy has a history much older than winter ecologists, and much of the rich language found in cold climates to describe snow has been adapted by winter ecologists (like the Russian sastrugi - above, or Innuit qali - below).

Snow can be grouped into three categories:
  1. Falling snow
  2. Snow on the ground
  3. Surface-generated ice features (like ice needles being pushed up from the ground on wet trails, hoar frost, icicles seeping out of cracks in bedrock)

Qali describes snow hanging from trees (like in the image above). Because our snow the other night fell in a frenzy of blustery winds, there wasn't a whole lot of qali left on the trees. Sintering is a natural process where snowflake crystals fuse together. Sintering can happen due to pressure (like stepping on the snow pack) or temperature (melt-freeze together). Because the snow crystals actually bond together, qali will act as a liquid moving in slow motion. Snakes, like in the image above, are common features in northern woods after a good snow storm. We observed a spot today where the sintered snow had bent down around the rock, creating a perfect overhang for a weasel to pop in and out of while hunting.

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