Signs of Winter 6: One Hundred Words for Snow!

(some information in this post was published in a January 23, 2014 blog)

Photo by E. S. Curtis, Wikimedia Commons

Frank Boas was an anthropologist who studied and lived with the Inuit people of northern Canada in the late Nineteenth Century. He is credited (or, sometimes, blamed) for observing that the Inuits have a hundred, words for snow. His logical explanation was that dominating or important components of a culture’s environment must be reflected in the diversity of their language about those factors. And, Inuits are absolutely surrounded by snow!

I don’t know if Inuits really have that many words for snow. I also don’t know if temperate climate dwelling people, as has been alleged, have at least as many words for liquid water (think pond, lake, river, creek, rill, run, puddle, etc). I am convinced, though, that anyone who likes to ski knows quite a number of combinations of adjectives and nouns for their much beloved sliding medium and, most importantly, I am convinced that despite obvious personal inconveniences and driving difficulties, winter is greatly improved when there is snow!

Photo by A. Kljatov, Wikimedia Commons

Snowflakes form in very cold clouds when a starting “nucleus” (which could be a few water molecules that have randomly formed a small crystal, or a suspended clay or dust particle, or even a pollen grain) collides with a very cold water droplet. This water droplet freezes on contact with the “nucleus” and forms an ice crystal. These crystals then adhere to more water molecules in the cloud to form the larger and larger crystals which eventually become snowflakes. Once these snowflakes reach a certain size they begin to fall down through the atmosphere and can add, depending on the water content of the air masses they are falling through, more and more water molecules to their expanding crystals.

The temperature and water content of the clouds and the underlying air determine the eventual size and shape of resulting snowflakes. Two snowflakes forming under identical conditions would, in spite of the old truism, be expected to be identical. The variability of conditions in any given cloud and in the surrounding air masses, though, makes forming identical snowflakes very unlikely. Kenneth Libbrecht at Caltech identifies thirty-five different types of snowflakes (great thanks to Kenneth for allowing the reprinting of his snowflake chart (from snowcyrstals.com)). Each type of snowflake is sculpted by the specific environment in which it originates.

Once on the ground the snowflakes accumulate and weather into a great variety of secondary shapes. There is powder snow (freshly fallen often low moisture snow that has not been compacted), crust snow (hard packed snow often iced together by rain), corn snow (lumpy snow made by freeze and thaw cycles), firn snow (old snow (more than a year old) that is granular but not excessively compacted), slush snow (partially melted snow often with puddles), snirt snow (snow covered with dirt and debris), watermelon snow (red colored snow due to the growth of an algae species), Yukimarimo snow (little balls of frost (seen in Antarctica), and more (maybe a hundred different kinds?)! Snowflakes can even (if they build up deeply enough and persist for long enough) compress themselves into massive systems of glacial ice.

Photo by J. Cotton, Flickr

The snow can also interact with the soil and surface litter and vegetation on which it falls to form a very interesting interface called the “subnivian space.”  The subnivia is a thin air layer found between the covering snow and the soil surface. It forms especially well when the snow layer becomes established prior to the hard freezing of the soil, and it is especially well established in complexly structured, “natural” soil-litter systems (as opposed to lawns or barren fields). Falling snow gathers on the surfaces of the irregular profile of the leaf litter and forms complex arches and domes over the dead plant materials. Heat from the unfrozen soil and also from the decomposition of the organic molecules in the leaf litter melts the contact snow layer which quickly re-freezes to form thin ice sheets which add to the structural strength and also to the insulating potential of the forming snow pack. A winter with a continuous snow cover will allow a significant and continuous subnivian space to form.

Photo by D. Sillman

Within this space (which may be several millimeters to even a couple of centimeters thick) a great variety of living organisms can be found. The micro-climate of the subnivia is sufficiently mild to allow temperature sensitive invertebrates (like beetles, collembola, mites and spiders) to continue their ecological activities of decomposition and predation throughout the winter season. Many small mammals (like voles, shrews and white footed mice) use the insulated subnivian space as shelter against the harsh surface conditions and also as a safe conduit between forage sites and their burrows. Within the subnivian space they are hidden from surface dwelling mammalian and avian predators like red foxes and hawks and owls. These predators can be observed in the winter standing very still on or just above the snow surface using their keen senses of hearing rather than vision to detect these subnivian mammals. Track histories of red foxes in particular reflect the slow, quiet stalking, pausing, and explosive digging through the snow cover as the foxes’ search for their subnivian prey.

It is a rare year that we have a continuous and appreciable enough snow cover to allow the formation of a true subnivia here in the lowlands of Western Pennsylvania. I have seen, though, vole tracks worn in the grass of my front yard converging onto the seed spill area under my bird feeders after our transient snows melt. The voles use the insulating and protective cover of even a few inches of snow to help themselves, like every other species around here, to my dearly purchased black oil sunflower seeds! I hope that they get some of the corn, too!