Life in the subnivean zone
Light, fluffy snow falls as I write. Snow globe snow; Ivory Snow snow; wedding confetti snow.
It was anthropologist Franz Boas who first wrote that the Inuits of northern Canada have a lot of words for snow. Boas lived with the Inuits of Baffin Island and learned their language.
In the century since he introduced the concept, the numbers have been exaggerated to the point that it’s been debunked as a hoax. It even has a name: “The Great Eskimo Vocabulary Hoax.”
Debate remains, but it might be that everyone is right.
In Yupik and Inuit languages, many suffixes can be added to a root word. The word count snowballs if the many suffix possibilities are included.
No doubt people whose livelihood depends on getting around on snow will have a lot of words describing various snow conditions.
We use adjectives, not suffixes, and coverage of the Sochi Olympics included numerous adjectives to describe snow: heavy, icy, slushy and — perhaps — salty. The world watched as a lot of athletes competed in a lot of sports that depend on ice and snow.
Turning from winter sports to the natural world of plants and animals, snow helps that world function, too.
Snow forms an insulating blanket that traps geothermal heat to create what’s called the “subnivean zone” — literally below the snow.
Trapped heat from the Earth’s core melts the snow at the base of the snow pack, creating an air space.
When snow cover is eight inches or more, ground temperatures rarely fall below 32 degrees Fahrenheit no matter what the air temperature above the snow.
Like a feather-down jacket, light, fluffy snow insulates best.
A world of insects, fungi, plants and animals exists in the snug subnivean world, protected from winter’s deep freeze, temperature fluctuations, and cold, drying winds.
Seemingly lifeless, snow-covered fields host a world of activity as mice and voles traverse their runways and the occasional weasel pursues them.
The red squirrel that pokes its head up through snow under backyard birdfeeders retreats to the warmth of the snowpack when temperatures plummet. Chipmunks rarely emerge to the cold air, surviving instead on food cached during the fall.
These are animals that don’t pack on the fat in fall, and they wouldn’t survive winter cold without refuge in the subnivean microclimate.
Snowcover also offers protection from many predators, although great horned owls and foxes can come crashing through snow to grab mice or vole.
Another snow crasher is a benign one: a grouse diving into snow where its body heat creates a thermal snow cave.
As for plants, an insulating blanket of snow protects roots and buds from constant freeze and thaw cycles. Similar to frost heaves that form on pavement, soils heave without the protection of snow.
Backyard gardeners know to lay down a protective mulch layer in the absence of snow.
Although dormant, plants lose moisture in buds and branches. Winter’s drying winds can be an ill wind that blows no good for natural and landscaped vegetation.
Despite the familiar saying that “April showers bring May flowers,” the insulating protection of snow is more essential to spring blooms.
Come the spring thaw, snowmelt seeps slowly into the ground to restore aquifers as well as the temporary vernal pools that are breeding nurseries for a diversity of amphibians and other wildlife.
As often is the case in nature, a balance of interrelated factors can be a delicate one.
Two springs ago, when the Harris Center’s Vernal Pool Project started up in Peterborough, vernal pools were hard to find. That winter’s modest snowfall resulted in modest groundwater and vernal pool gains. A lack of spring rains compounded the problem.
Ideal snow depth for a functioning subnivean zone is about eight inches at a minimum. If significant winter cold arrives before snowfall, plants and small mammals suffer high mortality.
Once the snowpack does arrive, unseasonable winter rains can penetrate the subnivean zone to freeze or drown it.
These days, global climate change is a growing focus and concern. Ongoing change brings with it unpredictable fluctuations in local weather as well as warming on a global scale.
The deep chills and unusual snow along the East Coast this winter qualify as local weather. Local weather has nothing to do with global climate change.
Globally, January was the fourth warmest weather on record.
As weather continues to fluctuate locally, and the climate continues to warm globally, impacts will include the subnivean zone.