Surviving the Arctic Winter

The polar night does not arrive gently. Somewhere above the Arctic Circle the sun dips below the horizon one autumn afternoon and does not return for weeks or months, depending on how far north you stand. Temperatures fall far below freezing and stay there. The sea grows a skin of ice that thickens into a continent of its own. For most of the living world this would be a death sentence. For a remarkable few, it is simply the season they were built for.

Bodies Against the Cold

The first problem is heat, or rather the relentless loss of it. An animal in the Arctic winter is a warm object in a cold universe, and physics is forever trying to pull the two into balance. The survivors answer with insulation of astonishing quality. The Arctic fox wears a coat so dense that it does not begin to shiver until the air drops below roughly minus forty degrees Celsius, and its small ears and short muzzle reduce the surface area through which warmth can escape. The muskox grows a layer of underwool called qiviut, finer and warmer than almost any other natural fibre, beneath a long outer coat that reaches nearly to the ground.

Shape matters as much as covering. Animals of the far north tend toward the compact and the rounded, minimising the exposed surface that bleeds heat into the air. Their extremities run cooler than their cores by design, a system of blood vessels arranged so that warm arterial blood flowing outward passes close to cold venous blood returning inward, handing over its heat before it can be lost to the frozen ground underfoot. A reindeer can stand on ice for hours with legs barely above freezing while its vital organs stay comfortably warm.

Food is the second, harder problem. The land offers almost nothing green for much of the year, and so the winter residents turn to what remains. Muskoxen and reindeer use their hooves and muzzles to dig through snow for the frozen lichen and sedge beneath. The Arctic fox trails the great bears across the sea ice, scavenging the remains of their seal kills, and caches food in the brief abundance of summer against the famine to come. The ptarmigan, feathered to its very toes, buries itself in soft snow at night, using the drift as a blanket against the deeper cold of the open air.

The Strategy of Disappearance

Some animals solve the winter by refusing to be present for it. The Arctic ground squirrel performs one of the most extreme feats of hibernation known to science, cooling its body below the freezing point of water without turning to ice, its heart slowing to a beat every few seconds, its brain nearly silent for months on end. It survives on fat laid down in the short summer and emerges in spring as though no time has passed at all.

Others simply leave. Many birds that nest on the tundra in summer are gone long before the dark, having travelled thousands of kilometres to gentler latitudes. Caribou herds migrate in their tens of thousands toward sheltered valleys and the thin pickings of the forest edge. The winter Arctic is defined as much by who is absent as by who remains.

For those who stay, the dark is not empty. Under the aurora and the long blue twilight that passes for noon, life continues in a slower, fiercer register. A fox trots across the sea ice, nose down, listening for the movement of a lemming beneath the snow. A hare freezes white against white. Seals keep breathing holes open in the ice with their teeth, surfacing in the dark to a world of predators that have learned exactly where to wait. Nothing about it is comfortable. Everything about it is a masterwork of adaptation, a demonstration that life, given enough time, will find a way to inhabit even the hardest edges of the planet.

And then, one day, a thin band of gold appears on the southern horizon and holds a moment longer than it did the day before. The sun is coming back. The survivors have done the impossible thing once again: they have carried themselves, breathing and warm, straight through the heart of the winter and out the other side.