Cold (16 page)

During the Little Ice Age, the cod fishery in Iceland — a fishery that had been active for centuries — failed as certain fish
moved south to warmer water. The Dutch prospered when cod appeared in the North Sea. The range of man, of
Homo sapiens,
changed, too. Eskimo hunters showed up in Scotland. Iceland’s population fell by half, and the Norse abandoned settlements
in Greenland, or their inhabitants simply died. And then the weather broke. The Little Ice Age gave way to a warming trend,
perhaps helped along by carbon dioxide dumped into the air from the fires of man — first wood, then wood and coal, then wood
and coal and oil, all burning at once, all contributing to the slow construction of a global greenhouse. Bering headed north,
along with De Long and Greely and Peary and Cook. Amundsen and Scott and Shackleton headed south. Some of them retreated alive,
while others perished like the Norse in Greenland, like spruce trees rooted too far north, too far into the polar zones, too
far into the cold, and buffeted by deadly winds.

It is November twelfth and eighteen degrees in Anchorage. My migratory timing has sent me back early, back to the cold, back
to the coming of winter. Spring remains a long way off. The official start of winter is weeks away, but a thin veil of snow
covers trees and houses and grass. The lakes around Anchorage have frozen, and where wind has blown the snow clear, ice crystals
as big as flower buds blossom across their surfaces.

Here at Powerline Pass, above Anchorage, brown grasses poke out through thicker snow. Mixed with the grasses, fat stems of
flower stalks, brown and dry, have split open just above the snow, their seams burst by expanding ice. Thigh-high shrubs —
leafless, their bark scraped by moose teeth — stand with their heads and shoulders above the snow. Soon enough, the shrubs
will disappear until spring, sleeping under the snow, away from the bitter cold and the wind that will careen down the surrounding
slopes and through this mountain pass. The boughs of white spruce, sloped downward and out, already shed snow, and the snow
piles up around them, while the ground immediately beneath them remains bare, protected by the umbrella of the boughs themselves
and warmed by dark, sun-absorbing bark.

We are skiing, my son and I. For him it is the first ski of the season. He is awkward with his summer legs and new boots.
He falls twice, but ten-year-olds bounce well, and his falls hinder neither pace nor exuberance. It is good, at times, to
be in the cold. It stimulates the senses and the mind. Douglas Mawson, the Antarctic explorer, once wrote, “During the long
hours of steady tramping across the trackless snow-fields, one’s thoughts flow…. The mind is unruffled and composed and the
passion of a great venture springing suddenly before the imagination is sobered by the calmness of pure reason.” My son would
express it differently. He would say it is fun. It might seem that his thin frame would chill easily, but he routinely sheds
layers and complains when his teachers make him wear gloves at recess. Now he asks me to carry his hat and outer jacket, and
then he rushes down the trail, skis flopping in rapid clumsy steps, poles gripped ham-fisted too far from his body, dark hair
fluffed straight up by the discarded hat.

Stone Age pictures of skis and skiing appear on the walls of caves and on rocks. Four thousand years ago, the nomadic Sami,
now incorrectly known as Laplanders, skied after the reindeer herds of Scandinavia. The word “ski” comes from the Norwegian
skith,
which means, literally, “wooden stick.” Until very recently, skis were wooden sticks. Specifically, they were birch sticks.
Where my son and I ski now, we are too high for birch. There is only willow and spruce and alder. Our skis are made of a composite
material. At this elevation, composite trees are at least as scarce as birch.

The physics of skiing is surprisingly complex. The pressure of a ski on snow combined with the movement of the ski creates
friction, and friction generates heat. It is occasionally said, often with great authority, that the pressure of a ski lowers
the melting temperature of the underlying snow and that movement of the ski adds heat through friction, creating a microscopic
layer of liquid water that lets the ski slide. This explains why skis drag when temperatures drop. At minus thirty, when the
snow is too cold to melt into microlayers of liquid water, the skier ceases gliding and begins to scrape. But it turns out
that the idea of a microlayer of water between snow and ski may not be right. Something else may be going on. It may be that
the molecules of frozen water at the surface of the snow, while still frozen, are not bound as tightly to the crystal lattice
beneath. The surface molecules cannot grip other molecules above their heads and under their feet, so they slide around. It
is their lack of grip that makes snow and ice slippery. This is a question of academic importance to certain physicists. But
here is a fact: the Sami skiers did not care. They cared about reindeer. They learned by trial and error, not through the
fundamentals of physics. My son cares no more than a Sami skier. He cares about fun and exuberance and feeling alive on a
cool fall afternoon just beneath the treeline. He learns by falling and getting up and falling again.

Next to the trail we see a young moose, nascent antlers still intact, lounging in a snowbank, protected from the wind by a
depression in the snow, chewing. Hot clouds puff out of his nostrils, and his jaws move in grinding circles, chewing cud.
His expression, while dumb, is not quite so dumb as that of a cow. The peak of Denali — Mount McKinley — is visible far away
to the north, beyond Cook Inlet. The mountain, from here, is entirely covered with snow. The weather on Denali at this time
of year would be of Martian intensity, but at this distance it looks serene under its shroud of snow.

Someone has stapled a sign to a post next to the trail. The sign is fluorescent red, with the black silhouette of a grizzly
bear. In thick letters, danger! appears beneath the bear’s image, which seems to smile slightly, as if up to something. At
the bottom of the sign, in Magic Marker, someone has written, “Moose kill (by bear) near Williwaw Creek. Public use trail
closed.” It is dated November fifth, a week earlier. We scan the hills hoping that the bear will stand out against the snow.
All we see is the shadow of one mountain against another, with the bands of white spruce and shrubby willow creeping up the
slopes, the treeline running higher in the gullies, zigzagging its way as far as it can before petering out, and above that
just snow, and still higher on the steepest slopes exposed rock, wind-blown or just too steep to hold snow. It is in some
ways like a coral reef, with certain species occurring on the reef flats and others in the gullies protected from waves, and
the whole thing petering out in sand. After the Philippines, the wind, though hardly cold by any reasonable standard, bites
my cheeks. We ski onward, toward the pass.

Plants, without exception, do not migrate. Some die off each autumn, leaving behind seeds that germinate the following spring,
analogous to the overwintering eggs of insects. Some die off aboveground but have roots that survive underground. Certain
grasses and herbs and shrubs overwinter with their branches and leaves buried under snow, dormant and hidden, hibernating.
Trees, though, stand out in the open, dormant but exposed, not dug into a burrow or cave or snow mound like some cowering,
thin-blooded hibernator. The dahurian larch is the world’s northernmost tree of any real size. It looks something like a spruce,
but its needles turn orange and fall off each autumn. It can be three feet thick at the base of its trunk. It survives the
winter cold of the far north, standing in the open at temperatures of ninety below zero, not counting windchill. Its forests
look like stands of Christmas trees, sometimes densely packed but sometimes scattered, in Mongolia, North Korea, northern
China, and Siberia. It grows as far north as the Khatanga River valley on Russia’s Taymyr Peninsula, the northern extent of
mainland Asia. The latitude there is seventy-two degrees, two degrees farther north than the treeless tundra of Alaska’s North
Slope, where the dahurian larch is absent not because it cannot survive, but because the vagaries of geobotanical history
and the total absence of landscape gardeners have never brought it there. Make no mistake: this is one tough tree. The dahurian
larch is the plant kingdom’s answer to Apsley Cherry-Garrard and Father Henry and Ernest Shackleton. It knows how to handle
cold weather.

Other trees, softer than the dahurian larch, drop out one by one as the weather becomes colder. First the palm and the mosquito-infested
mangrove, killed by nothing more than a hard freeze, and then the shade-tree live oak with its thick branches spread out like
umbrellas, dead at eighteen degrees. The redwood and the southern magnolia and the slash pine give up at five degrees above.
The sweet gum is gone at seventeen below. Then the maple and the shagbark hickory and the hop hornbeam give way to the frost.
And finally it is too much even for the spruce and the dahurian larch, and the forests are gone. Almost gone, because there
are still the bonsai trees, the diminutive trees that hardly seem like trees at all, except that they have woody stems and
leaves and they are in fact species of birch and willow. There is
Betula nana,
a birch that grows no more than a few feet tall and looks nothing like its full-size cousin the white-barked
Betula papyrifera,
the paper birch, the tree of the birchbark canoe. And the willows:
Salix arctica, Salix ovalifolia, Salix reticulata,
and others, none more than a few inches tall. Compare these to
Salix nigra,
the black willow, the tree of the shifting sand islands and banks of the Mississippi River, its trunk obese, its branches
reaching higher than a ten-story building, its leaves longer than the full height of its Arctic cousins, its ability to survive
a real winter virtually nonexistent.

Some of the tiny cold-climate willows spread like vines across the ground, but others grow like stunted stately trees, with
thick trunks and smaller branches and dense accumulations of tiny leaves, all reduced, all low to the ground, forming forests
odd not only for their tiny size but also because the grass, in summer, towers above the trees. An ecologist looking at these
miniatures might describe an understory of trees and a canopy of grass. Reduced size lets these willows hide under snow, avoiding
the worst of the cold and the moisture-starved winter winds that would suck the water from frozen sap. Without snow cover,
the tiny trees would be forced to replace lost moisture, to somehow pull water from frozen ground. More likely, the trees
would die.

Many trees — perhaps most — can survive at temperatures far below those found where the trees grow. Cold of twenty below will
not kill the bald cypress, but the bald cypress is not found in climates this cold. The same is true for the Oregon white
oak and the red pine and eastern hemlock. Even the paper birch, the quaking aspen, and the black spruce, trees of the far
north, would survive in temperatures colder than those where they are found. But it is not only the cold and dry air they
have to face. It is the wind, and even the weight of snow. The wind, kicking up ground blizzards and carrying sharp-edged
ice crystals, can sand-blast a tree, stripping off bark on the upwind side and exposing raw tissue, killing and polishing
the cambium, the tissue beneath the bark that shuttles nutrients between leaves and roots. Blowing snow can kill the upwind
branches, leaving a tree that looks like a flag, its living branches all pointing downwind. It can prevent trees from growing
upward, leaving them prostrate on the ground. Or, for trees that struggle through the first ten or twenty or thirty feet of
height, it can leave a tree mop-headed, able to form thick concentrations of needles on branches high above the blowing snow
and ice of ground blizzards.

Accumulated snow, piled on in the absence of wind, can snap a tree in half. Trees forty feet tall sometimes hold more than
six thousand pounds of snow. Certain trees have evolved to shed snow. The branches of spruce trees arc gracefully downward,
allowing snow to slide to the ground. Fir boughs flex, dumping snow without breaking. When an ice storm hits a forest of oak
or maple or ash before leaves have been shed, the weight of ice on leaves fractures branches, limbs, and even trunks, or pulls
whole trees over, ripping their roots from the ground, sending them tumbling into houses, laying them across roads, or suspending
them in mid-descent on power lines, wreaking havoc. In Finland, on certain mountain slopes, breakage from snow loading controls
the extent of forestation. The treeline is controlled by the weight of snow.