Cold (32 page)

For humans, there is the issue of the cold itself, and winter damage to crops and roads and pipes, and fire hydrants frost-heaved
out of the ground. But there is also the issue of slipping on ice. Sledders and skiers suffer various sprains and breaks and
even death. States and cities have considered helmet laws for children on sleds. Walkers, too, are affected. An oil field
worker in northern Alaska slipped, apparently falling backward. The back of his head connected with the ice. He died.

And there are avalanches. A 2002 report from the Kenai National Wildlife Refuge describes the investigation of a herd of caribou
caught in an avalanche the previous winter. The herd, wandering across a steep slope, triggered the slide. “The helicopter
prop wash filled the sky with caribou hair,” the report says, “and caribou skulls and bones lay scattered over a large area.”
At least 143 caribou died under thousands of tons of suddenly moving snow.

It is April twenty-eighth here in Orlando, Florida, and pushing eighty degrees. On the North Slope, it is seven above. On
the North Pole, the thermometer flirts with ten above. On the South Pole, temperatures are dropping below minus sixty.

In 1905 on this date, Orlando thermometers dipped briefly to sixteen degrees. In 1940, Miami dropped to twenty-eight degrees.
In 1985, Jacksonville found the seven-degree mark, and Pensacola encountered five degrees. In 1899, Tallahassee experienced
subzero temperatures, falling to two below. People in Florida hate the cold. Many have moved here from places such as Detroit
and Minneapolis and Montana. My cabdriver, originally from Chicago, brags that he no longer owns a warm coat. Near the hotel
pool, a woman who grew up in Florida tells me that she cannot even imagine forty below.

“Imagine thirty degrees,” I tell her. “Now imagine eighty degrees. They are fifty degrees apart. Now imagine that same difference,
but downward from thirty degrees. That is twenty below. Subtract another twenty degrees, and you have forty below.” She stares
blankly, as if at a madman. Imagination cannot extrapolate beyond the temperatures it has experienced. I stand in the sun,
face upward, enjoying for the moment a latitudinal spring.

I
t is May fifth and hovering in the high forties on Prince William Sound, southeast of Anchorage, the site, seventeen years
ago, of the 1989
Exxon Valdez
oil spill. Prince William Sound is Alaska at its best: a piece of the ocean protected by snow-covered mountains, kelp and
barnacles visible through clear water, puffins and otters on the surface, the occasional bear foraging along the shore, orcas
and sea lions in the waves. Weather and time have washed away obvious remnants of the spill, but oil still sits beneath the
gravel on certain beaches, and biologists continue to argue over evidence of residual damage. The temperature swings noticeably
as our boat moves across the water, here finding a warm spot in the sun, here feeling the wind blowing down the slopes of
a snow-covered mountain, here chilled by a glacier. Young cow parsnip sprouts velvety green along the shore, and willows bud
on south-facing slopes. Spruce boughs stand dark green, having shed their winter burden of snow, but beneath the spruce, the
snow remains deep. Higher up, slabs of snow have collapsed, dropping two or three feet straight down and leaving obvious faults
in the snow. In places, the slabs have slid down the sides of mountains in avalanches of various dimensions. Where the mountains
catch the sun, entire ridgelines have slid. Below, the avalanche snow lies in piles taller than trees, burying God knows what.
The snow and ice have fractured pieces of the mountain’s marrow, then pulverized them, leaving dirty streaks of mountain grindings
exposed in fingers that reach downward across the snow-covered slopes.

On the water: flocks of kittiwake gulls, murrelets in groups of three and four, pigeon guillemots with their black-and-white
wings bobbing in the waves, groups of Dall’s porpoises as fast as torpedoes, scattered otters floating with their bellies
and paws exposed to the sun, and three humpback whales. All but the humpbacks have overwintered here or nearby, tolerating
the cold. The humpbacks are just back from Hawaii or Japan or Mexico, where they have fasted for months, focusing on singing
their famous love songs under the waves, frolicking and courting and mating. Now they move patiently, submerging to sieve
food from the rich, cold depths of Prince William Sound, then surfacing to breathe, then submerging to eat again. Their grazing
is like that of elephants, the movements of slow-motion ballet carried by tons of fleshy momentum.

Our boat pushes in toward Beloit Glacier. Beloit is a tidewater glacier, reaching out past land into the bay itself, a grand
remnant of a much bigger glacier that would have resided here in the late Pleistocene, shrinking and growing with warm spells
and cold spells for untold years. Waves lap along the glacier’s front, and ice thunders down directly into the sea, creating
violent waves that radiate outward. Occasionally, ice calves off underwater and rockets upward, emerging like a frozen submarine.
As we move closer, the boat’s steel hull crashes through increasingly large blocks of floating ice. A mile from the glacier,
we slow down and then drift with the ice, watching the glacier melt. Cold air sweeps down the glacier and out across a mile
of water. The Windbreaker on a man standing next to me flaps like a flag, and his hood fills like a wind sock. The glacier’s
breath mocks us, reminding us that spring is delayed, that summer is short, that winter will be back soon enough. We live
at the end of a time of glaciation and ice, in the warmish dusk of an ice age. The massive glaciations of the late Pleistocene
were only yesterday.

Spring came to the Pleistocene Ice Age about ten thousand years ago. Prior to the start of this recent interglacial, two great
ice sheets and many smaller ice fields and glaciers stretched across North America during a period of glaciation that lasted
a hundred thousand years. Today’s Beloit Glacier in Prince William Sound is to those ice sheets as a lemming is to a woolly
mammoth. During the periods of extensive glaciation, the sites of what would become Chicago, Seattle, Boston, Cleveland, and
Kansas City were perpetually snowed in. Just to the south, there was tundra, and to the south of that, forests and grasslands
that were stocked with horses and small camels and mastodons. Ground sloths the size of elephants lumbered about, hiding from
saber-toothed tigers and American lions. The short-faced bear stood more than five feet tall at its shoulders. Reared up on
its hind legs, it stood twelve feet tall. It has been said that the presence of this bear slowed the movement of humans across
the Bering Land Bridge, a now drowned stretch of land also called Beringia.

Even during the coldest periods of the Pleistocene Ice Age, some areas were surprisingly ice-free. Mountaintops stood above
the ice. Along the east and west coasts of North America, certain mountains blocked the moving ice sheets, leaving shadows
of open but sparsely vegetated ground. Strangest of all, most of interior Alaska, too dry to generate massive quantities of
snow, was free of the glaciers that blanketed most of northern North America. Alaska was windswept and brutally cold, but
not entirely buried in mile-thick snow and ice. And Alaska did not look like Alaska. With so much of the world’s water tied
up in ice, sea level was three hundred feet lower than it is today, and the Bering Land Bridge, as ice-free as the rest of
the state, joined North America and Russia. What is now St. Paul Island, a lonely postal address in the middle of the Bering
Sea, was then a low hill in what was likely a grassy plain. But the grassy plain did not look like today’s grassy plains.
Instead it was a mix of Arctic tundra and modern grassland, sometimes called the Arctic steppe. In its abundance of wild animals
and in their variety, the Arctic steppe resembled the Serengeti.

Wildlife in Beringia, on the Arctic steppe, was not the same as that found south of the great ice sheets, but it was similar.
Mammoths wandered in the grass with musk oxen, bison, elk, grizzly bears, and Dall sheep. During the warm interglacial periods
that came and went during the two and a half million years of the Pleistocene Ice Age, the corridors joining north to south
would open like icy gates, letting animals through from each direction. But if the warmth stayed too long, sea level would
rise and flood Beringia, closing the watery gate between Asia and America. The Beringia gate closed each time the sea rose
to within 125 feet of its current level.

The camel and the horse, both products of North American evolution, found their way north and eventually into Asia while the
gate was open, and later went extinct in North America. The gray wolf found its way east from Europe and then south, where
it met its much bigger and now very much extinct distant cousin the dire wolf. Deer and sheep may have arisen in the old world
and crossed to the new via Beringia. Each time the gates closed, the animals locked in on either side would evolve on their
own.

The ice gates — the massive glaciers and snowfields — separating north from south opened and closed to some degree in concert
with the Beringia gates. The animals south of the ice evolved differently than those north of the ice, developing esoteric
differences. The bison of Beringia had two shoulder humps and long curved horns, while the bison south of the ice had a single
hump and shorter horns. At one time, the grizzly bear may have been found only north of the ice, while the black bear may
have been found only to the south. The Dall sheep was found to the north, while the bighorn sheep was found to the south.

The ice created its own weather. Wind whipped off the edges of the ice sheets. Where ice sheets met the ocean, they chilled
the water, powering currents. Warm air meeting the ice cooled, and its moisture fell out as snow. Air blowing into the interior
of the sheets tended to be sucked dry. Over time, the interior ice sheets thinned, snow-starved. During the Pleistocene Ice
Age — the most recent ice age, the one that is dying now, choked by greenhouse gases — spring came and went repeatedly. Each
time that metaphorical spring came to the earth, the ice would retreat, biding its time through a millennial summer and then
advancing again. And each spring, in retreating, the ice would dump its water into the sea. Sea level would rise reasonably
quickly.

The land rose, too. Relieved of the weight of ice, the land, for ages pressed down by the sheer mass of the ice it had carried
on its shoulders, would rebound. Areas would flood with the rising sea level and then emerge, springing upward with the burden
of ice removed. Dry pastures and hilltops and mountainsides would emerge with fossils of shells, fish, crabs, and in at least
one case kelp, all speaking of a time when they were flooded by cold water.

The Canadian ecologist Evelyn Pielou put the timing of the Pleistocene Ice Age in perspective. “To make the relative lengths
of enormous stretches of time easy to visualize,” she wrote, “let us use as a model one decade to represent the past billion
years.” That would make the earth about forty-five years old. “On the scale of the model,” Pielou continued, “a glacial age
lasts a month or two.” One great ice age occurred seven or eight years ago, and another just two or three years ago, when
the continents shifted into position to separate the steady warmth of the tropics from the seasonal cold of the far north.
Each lasted a month or two, until the continents could drift a bit, opening a gate through which warm currents could carry
warm water north and cold currents could dump cold water south. The Pleistocene started last week. Things seem warm now, with
the great ice sheets pulled back and no more than a patch of snow covering Greenland, another over the North Pole, another
to the far south, and a few scattered snowfields and glaciers here and there. During this last week, the ice has expanded
and pulled back and expanded and pulled back again and again, at least nineteen times, responding to the level of carbon dioxide
in the atmosphere, the liveliness of the sun, and the Milankovitch cycle of an always changing tilt in the earth’s axis and
a stretching out of its orbit. If greenhouse gases do not kick this cycle out of kilter, as they almost certainly will, the
next expansion of the ice is only minutes away. Minutes being, of course, thousands of years.