Cold (18 page)

There may be differences, too, among Europeans and Africans and Asians. During the Korean War, it became evident that frostbite
was more prevalent among black soldiers than among white soldiers. On average, black men were four times more likely than
white men to suffer injuries from the cold, and black women were twice as likely to suffer injuries as white women. “Arabs,”
wrote a doctor reporting these data, “appear to be similarly predisposed, as are individuals from warmer climates.” But individual
variability would be considerable, with some black men and Arabs facing the cold with far more aplomb than most of their white
colleagues.

Blood circulation to the skin and hands is greater in Inuit people — Eskimos — than in Europeans, apparently protecting them
from frostbite. Norwegian fishermen have shown similar tendencies. Korean and Japanese ama divers — traditionally women who
dive on a breath of air after seaweed, shellfish, and pearls — have a legendary tolerance for cold water. A century ago, they
often dove topless, spending hours each day in the water. Today they wear wet-suit tops or tights. Whatever physiological
tolerance they once had has diminished but not disappeared.

A certain amount of adaptation is possible. In 1960, a University of Alaska physiologist named Laurence Irving noticed two
students wandering around the Fairbanks campus in light clothes and without shoes. The students were adhering to the rites
of a religious sect that discouraged the wearing of shoes, a practice that must have originated somewhere warmer than central
Alaska. Irving put the students in a room chilled to thirty-two degrees, then measured the temperature of their fingers and
toes for an hour. Their toes and fingers would cool off, then warm up again, apparently as blood vessels constricted but then
dilated, sending warm blood to the extremities before they became dangerously cold. The students did not shiver until after
fifty minutes. Irving did the same with an air force volunteer but had to discontinue the experiment after thirty minutes.
“The airman’s toes,” he wrote, “became so painful and he began to shiver so violently that I caused him to terminate the test
lest he shake himself apart.”

Quebec City postal workers, walking from mailbox to mailbox through the Canadian winter, grow more cold tolerant as winter
wears on. Heart rate and blood pressure drop. Workers in Antarctica are said to adapt over time by increasing their core temperature.
Charles Wright, who traveled with Scott in Antarctica but was not chosen for the fatal trek to the pole, trained himself for
the cold even as a child. “For some incredible reason,” he told an interviewer, “I thought it was a good thing — I was living
in Toronto at the time — to toughen oneself a bit, so I wore the same clothes in summer and winter.”

Habituation to cold might disappear after a few winters in Florida but be regained with a return to colder regions. By contrast,
the genetically programmed tolerance of the Alacalufe, the Australian Aborigine, and the Inuit would be more long lasting.
But all of this habituation in human postal workers and Arctic explorers, all of the genetically conferred advantages of the
Alacalufe and the Australian Aborigine and the Inuit, offer no more than the smallest advantages. Compared to the arctic fox
or the wolf or the musk ox, compared to the ground squirrel or the wood frog or the poorwill, the most cold-hardened human,
if forced to rely on physiology alone, is as fragile as thin ice. A human without thick clothes or shelter or fuel will freeze
to death in conditions too warm to trigger shivering in a moose. At the end of summer, the human response is primarily one
of putting on clothes, lighting a fire, and turning up the thermostat. Or, alternatively, of frostbite and death by hypothermia.

I
t is December third and twenty-six degrees in Anchorage. Heat leaks through roofs, and melting snow drips over gutters, turning
into thick icicles that threaten to crash down, dangerous, not sharp enough to impale but heavy enough to bludgeon. The sky
is over-cast, the clouds forming a vaporous blanket that holds in the heat. Thanksgiving week, with six straight days below
zero, has defrosted. The clear, cold nights of November, loitering in the teens, have migrated.

The entire state suffers in the heat. Juneau, the capital, hit thirty-nine. Anchorage is warmer than Chicago, Des Moines,
Minneapolis, Salt Lake City, and Grand Rapids, and almost as warm as Omaha, Seattle, and Albuquerque. The North Slope hit
twelve degrees. Fairbanks, in the icy interior, is in the positive digits, four above.

This is inconvenient but not terribly unusual. In 1929, Anchorage hit fifty-one degrees on December third. People in Anchorage
grow accustomed to winter heat waves driven by what fur traders called the chinook winds — winds that came from the land of
the Chinook tribe, in the Pacific Northwest. The Alaskan version of the chinook winds blow into Anchorage with some regularity,
their hot breath melting the snow, leaving streets filled with water and turning forest floors into slushy swamps. It happens
so abruptly that the chinook winds are sometimes said to eat the snow. On the mountainsides above Anchorage, chinook winds
can reach hurricane strength. The loss of roofs from hillside houses is not unknown, giving wealthy homeowners exceptional
but unexpected views of crisp winter skies. Anchorage is not unique in suffering from these winds. In 1972, a chinook wind
blew into Loma, Montana, raising temperatures from 54 below to 49 above, a change of 103 degrees in twenty-four hours.

But today’s heat wave did not blow in on a chinook wind. It was forecast by the National Weather Service in October. Using
data from satellites and ocean buoys moored in water more than three miles deep, the National Weather Service warned that
we would have an El Niño year. A week ago, the Climate Prediction Center in Maryland issued an advisory: “El Niño conditions
should intensify during the next one to three months.” For Alaska, this December through February will be warmer than normal.

Long before it came to the attention of meteorologists, El Niño was noticed by South American fishermen, who recognized warm
currents off Peru and Ecuador each year around Christmas. The warm currents killed the fishing. The fishermen named the annual
event El Niño, “the Little One,” in honor of the birth of Christ. Globally, El Niño has come to refer to those years when
the Christmas currents are unusually strong. The currents strengthen when trade winds blowing to the west weaken and unusual
volumes of warm water reach Peru and Ecuador. Global weather patterns respond. It rains in California. Australia dries out,
and bush fires burn out of control. Gulf of Mexico hurricanes become less prevalent. South China Sea typhoons become more
prevalent. Corals die in the Pacific Ocean. People catch marlin off the coast of Washington State. With El Niño, cold, clear
high-pressure air stalls between Alaska and Seattle. The pressure ridge forces warm winds forming along the Aleutian Islands
to swing north, toward Anchorage. The city will have rain within days.

This is no chinook wind, but our snow will be eaten all the same.

The moose is so well insulated that the southern border of its range is sometimes said to be set by its intolerance of heat.
A moose has two kinds of fur — thick guard hairs that give it color and finer underfur that keeps it warm. Piloerection is
the fluffing out of hair, often for the purpose of staying warm — for increasing the insulative effectiveness of hair. In
humans, piloerection, rendered useless by millions of years of evolution, causes goose bumps. In moose, the fur is so efficient
that piloerection does not occur until the mercury drops below minus ten. A moose’s metabolism does not increase until minus
twenty. But even on a mild winter night without wind, the moose will lose the energy equivalent of a Snickers bar every hour.
It needs to eat or lose weight. In fact, it does both.

A moose in Alaska’s Denali National Park might feed six hours each day, swallowing more than thirty pounds of branches and
bark. Then it ruminates for another twelve hours. In this context, ruminating is not a matter of turning something over in
the mind, as a human might do, but rather of chewing cud. Like a cow, the moose regurgitates partly digested food from its
first stomach, chews it, and reswallows. The jaw muscles, ruminating, generate heat. The four stomachs, churning, generate
heat. Microbial action in the gut generates heat. A ruminating moose might generate fifty percent more heat than a fasting
moose. But in winter, the food is tough to digest. Branches and bark are less nutritious than the fresh green shoots and leaves
and flowers of spring and summer. The amount of food that the moose can process is limited by the number of hours in a day.
It is possible for the moose to starve to death with its stomachs full, unable to keep up with energy demands.

The moose has to decide how hard it will search for food. Though seemingly dim-witted, it knows at some level that it is not
likely to find high-quality forage in the snow. It knows, too, that movement through snow is no easy task. It lifts its long
legs high to step over the snow and even plows through deep snow, looking for thinner patches, following the tracks of other
moose or wind-scoured frozen rivers or ski trails. But when the snow is deep, the moose must reduce its range. It may wander
over no more than ten or twenty acres, conserving energy, chewing its cud, burning its fat, stripping bark from trees. It
will sit in the snow in preference to standing, using the snow as a blanket. Foraging, successful or not, will use at least
twenty percent more energy than sitting in the snow. On sunny days, the moose will move into the open. On cold nights, it
will sleep under thick spruce cover. It will burn ten thousand calories or more in a day, twice that of a well-fed Arctic
explorer. Like the Arctic explorer, the moose will lose weight.

The moose has been called a “confronter” or a “tolerator” or, more descriptively, a “winter active,” because it confronts
winter. It tolerates winter. Winter actives neither hibernate nor migrate. The formula they pursue seems simple: take in as
many calories as you can, preserve your fat, and hope for the best.

Winter actives have fur that holds in heat. The arctic fox, curled up in a ball, wrapped in its own fur, lies comfortably
on the northern pack ice at forty below, steadfastly refusing to shiver. The winter coat of the caribou is so warm that the
animal uses less energy in winter than in summer. Musk oxen in small herds of ten or fifteen, when harassed, circle up, horns
out and heads down, their hair hanging matted, windblown and iced, their expressions Pleistocene. They refuse to run not because
they are stupid, but because their coats are so warm that to run is to overheat. Other animals have layers of fat that not
only buffer winter food shortages but also provide insulation. They wear sweaters of fat. An inch of fat provides more insulation
than an inch of wool. A male polar bear ambles across the pack ice throughout winter, feeding on seals. It enters the cold
season rotund, wearing the equivalent of eight or ten wool sweaters under its fur.

Where fur and fat are not enough, there is shelter. Gray squirrels, unlike ground squirrels, do not hibernate. Instead, they
make nests of twigs, maybe ten inches in diameter. Inside, a well-made gray squirrel’s nest might have twenty layers of leaves,
and inside the leaves might be finely shredded bark, and inside the finely shredded bark might be a four-inch-wide chamber,
a gray squirrel’s winter parlor, its home between bouts of foraging. Flying squirrels make similar nests. The insulation of
a flying squirrel nest can weigh five times more than the squirrel itself. Naturalist Bernd Heinrich once chased a flying
squirrel from its nest, put a hot potato in the insulated chamber, and watched it cool. At nine degrees outside, the potato
cooled less than thirty degrees in half an hour. Put another way, the potato was still hot enough to eat after thirty minutes
in a flying squirrel’s nest with the outside temperature at nine degrees above zero.

Winter actives have other tricks and adaptations. Beavers and muskrats huddle with their families, sharing their warmth. The
feet of snowshoe hares are so enlarged relative to their weight that they walk on the snow’s surface without breaking through.
Their foot loads, as they are called, are comparable to those of a human wearing snowshoes that are ten times the size of
a human foot. Caribou plant their front feet at a steep angle, supporting their weight in the snow on the hoof, the upper
part of each foot, and the dewclaw — a toelike protuberance sticking out from the back of what looks like the animal’s ankle.
Likewise, lynx, wolves, and wolverines float across the snow’s surface on enlarged feet.