Cold

by Bill Streever

  This is the permafrost tunnel, built by the U.S. Army Corps of Engineers in the 1960s to test tunneling equipment. The idea was to bore into frozen hillsides, perhaps turning them into missile silos and bunkers. Cold War thinking, so to speak. Now the tunnel is used for research and education. A worn display panel shows visitors a picture of a very calm Dwight D. Eisenhower next to Nikita Khrushchev, whose fist is raised. I am here with a Russian permafrost expert based at the University of Alaska. Pointing out the photographs of Eisenhower and Khrushchev, he laughs at the way the world has changed.

  The hill itself is of loess —finely ground particles originating when rocks were pulverized by massive rivers of ice in the Brooks Range, north of here. This grinding goes on today under what is left of the glaciers, but most of it occurred when the glaciers were more extensive, from seventy thousand years ago to a mere ten thousand years ago, and before that, on and off for two and a half million years. The ice, sometimes miles thick, flowed down hills and across valleys, carrying with it stones and boulders and rocks. The bottom of the glacier, with its load of rock, acted as a massive, slow-moving mill, reducing granite mountainsides to dust as fine as flour — the same stuff that today paints the water of glacial lakes azure. But when the glaciers pulled back, the flour was everywhere. Gales blew where warming ground met glacial ice. The gales picked up the flour, scattering it through central Alaska, restacking it in drifts that became hills.

  A walk into the permafrost tunnel is a walk through time. The lighting, the air-conditioning system, the signs, the very feel of the place speak of the Cold War. The sweeping scars of the tunneling machine, now decades old, remain frozen in place. And the walls themselves range to more than forty thousand years old. The walls of this tunnel — the earth of this hill — have been frozen solid for forty thousand years.

  Frozen soil is not a rarity. Something like one-fifth of the world’s land area lies within the permafrost zone. Poke a steel rod into the ground in northern Alaska, and you will hit frozen ground. The same rod will hit frozen ground in northern Russia, northern China, northern Norway, Iceland, and Greenland. It will hit frozen ground on certain mountaintops at the latitude of California. It will hit frozen ground in parts of Patagonia. Late in the summer, the rod will penetrate eighteen inches, thirty inches, three feet, and then hit what feels like bedrock. But it is a bedrock of frozen sand or gravel or fine glacial flour, glued together by ice. In some places, three-quarters of the soil is in fact frozen water. Put a building on this stuff, heat the building and warm up the ground, and the ice will start to melt.

  What makes this tunnel unusual is that the government dug into the frozen ground, then kept it frozen. In summer, the massive air conditioner keeps the tunnel chilled near its entrance, where warm drafts sneak past doors. The earth here is like a giant cooler, its outer layers insulating its inside, keeping the tunnel walls in the low twenties. In these latitudes and farther north, the surface expression of frozen ground is visible everywhere, in the form of polygons and frost boils and slumped ground. Here you can walk right through that frozen ground. You get the worm’s-eye view.

  The place stinks. It is a forty-thousand-year-old smell of mixed mold and musty dirt and cold, something like the smell of a refrigerator that has gone too long unopened. The tunnel is twenty feet in diameter and roughly round in cross section. One passage leads back into the hill more or less horizontally, while another slants downward. We head in horizontally, taking advantage of a metal walk-way. Roots stick out from the walls and ceiling. It is easy to imagine that these roots are alive, reaching down from the birch and alder trees growing on the hillside. But in fact we are well below the root zone. Ten feet beneath the surface, the ground never thaws, and living tree roots do not penetrate into permanently frozen ground. The roots in the tunnel walls are the frozen remains of Pleistocene plants. And what is this? The bones of a long-extinct steppe bison: a jawbone, a femur, a vertebra. In the wall, a horn stands frozen in time. The steppe bison was common here thirty thousand years ago but has been extinct for thousands of years.

  The Russian tells me of plant material found in the tunnel that was still green after thousands of years. Grass had been covered with snow in a summer blizzard, and then the snow was buried under blowing soil. Likewise, the bison bones had been buried by the blowing loess, preserved for thousands of years. Occasionally, whole animals, flesh intact, are preserved in the permafrost. In 1979, a Fairbanks gold miner found a frozen steppe bison. That is to say, he found not only bones and teeth but a frozen carcass complete with skin and muscles and hair. Claw and tooth marks show that it was killed by an extinct lion. It had frozen so quickly after its death that scavengers could not pick it to pieces. In the holes left behind by the lion’s teeth, coagulated blood remained frozen in tiny pools. Shortly after the kill, or during the kill itself, snow may have been falling. The lion may have fed on the carcass for several days or even weeks but abandoned it before spring, leaving meat and flesh and bones behind. One can imagine the lion wandering away, overtaken and bewildered by blowing snow. At first the snow drifts against the carcass. Later, loess carried by wind or a landslide settles on top of the snow. The dead steppe bison is buried. A new layer of permafrost forms. Years pass. Miners dig into the icy ground. A university professor becomes involved. Carbon dating of a piece of skin shows that the bison died thirty-six thousand years ago. The carcass stands today in a glass case at the Museum of the North in Fairbanks, resurrected, looking more like a Texas longhorn than the modern bison of the Great Plains.

  We walk past and through different features of frozen ground. I stand beneath an ice wedge — the same sort of ice wedge that forms polygons in the ground farther north. Near Prudhoe Bay, the ground is laced with these things, but they are visible only in their effect on the ground’s surface. If the first few feet of soil around Prudhoe Bay were magically removed, the ground would become a honeycomb of ice. The soil, intact, obscures this reality. Here, underground, I can see the wedges themselves. The ancient ground expanded in summer and contracted in autumn, opening cracks. The cracks filled with water, and the water froze. The cycle was repeated again and again. And then the ice wedges were buried under the blowing loess that would become the walls of this tunnel. Looking at an ice wedge in the wall of the tunnel, I see a record of the process. Sediment tracks run up and down its body, marking each year’s sequence of cracking and freezing, reminiscent of tree rings. The wedge is more than four feet wide at its top. Conservatively, it took hundreds of years to form.

  Water is strange stuff. Most substances, when cooled, contract. This is why thermometers work: mercury shrinks as it cools and expands as it warms. Warmth makes the molecules in a substance move faster. They dance around, bumping into one another. As the temperature increases, they dance faster, and when they bump into one another, they push harder. They need more space. A cooler temperature means slower movement, softer collisions, and less space. This holds true for water, but only to thirty-nine degrees. After that, the water molecules start to line up. The water thickens. Hydrogen atoms in one molecule attract oxygen atoms in others. The process of crystallization begins. At thirty-two degrees, the water starts to freeze. The molecules line up like tiny soldiers in formation, with orderly space between them. Newly frozen water is nine percent bigger than liquid water. Once frozen, if it continues to cool, expansion stops, and like most substances it shrinks.

  Small caves and hollows line the tunnel’s walls. The ice holding the walls together has not melted, but some of it has sublimated — disappeared into the air as vapor without ever going through a liquid phase. The walls are frozen and steaming at the same time. This is true, too, of snow and ice at the surface — in glaciers, in freezers. The vaporization of ice — evaporation from the solid phase — is the basis of the freezer burn that ruins frozen meat and fish.

  Among the ice wedges, veins of ice run horizontally along the tunnel walls like veins of coal in a Virginia mountainside. The Russian calls
this “segregation ice.” It forms in keeping with another strange property of water: liquid water in finely grained soil is sucked toward colder zones in the soil. We stare at a vein of segregation ice, a one-inch-thick stratum of what looks like almost pure ice.

  “People call it cryogenic suction,” the Russian says, “as though that explains everything. But cryogenic suction is a very complicated mechanism.” In freezing soils, liquid water adheres to soil particles, forming thin layers of water around each grain of soil. Molecules are bound more tightly to thin layers of water than to thick layers of water, and thin layers of water tend to attract molecules of water from nearby thicker layers. When soil starts to freeze, the layers of liquid water turn to ice and become thinner. Liquid water moves from warmer parts of the soil to parts of the soil where ice is forming. Water is sucked toward what is sometimes called the “freezing front.” Segregation ice forms.

  “I have seen segregated ice one meter thick,” the Russian tells me. “I saw it personally.” He has heard of segregation ice twenty meters thick — sixty-six feet — but he has not seen it himself. He presents this information as though he does not believe it.

  We come to what looks like a small frozen pond or a puddle in the wall of the tunnel. It is shaped like a pond, seen edge on, ten feet across. At the bottom, the ice is dirty, as if it had been filled with silt, and at the top the ice is clear. The Russian calls it an “ice lens.” He says that it could have been a frozen pond that was covered by blowing soil and permanently insulated from the summer, but he thinks that it more likely formed underground, a small pocket of flowing groundwater that at some time in the distant past froze into place. We are at this point something like one hundred feet underground, surrounded by soil and ice laid down when steppe bison and mammoths and saber-toothed tigers roamed the surface. Above us, moving toward the surface, the ground is progressively younger. At the surface, the soil is almost brand-new, with four inches or so of fine soil blowing in and settling on top of the hill every hundred years. Below us, deeper underground, in the lower tunnel, it is older.

  We wander off the steel grating and into the lower tunnel, heading deeper and farther back into the Pleistocene. Our steps kick up clouds of fine soil. It is strikingly dry, bone-dry. Looking behind us, I see that the air is hazy with the clouds of fine soil. I feel grit in my teeth. I feel it in my hair. It is in my eyes. We look for a moment at what seems to be an old streambed, a layer of sand and stones worked round by flowing water in the distant past. Forty thousand years ago, where we stand now would have been a pretty little stream. Steppe bison would have grazed along its banks. Extinct lions would have stalked the bison and lapped water from the stream. We are forty thousand years underground.

  But we are not alone. The Russian once sent a sample from the tunnel’s wall to a friend at another laboratory. The sample contained living bacteria. His friend feeds the bacteria and grows it in a laboratory at temperatures hovering around five below zero. This stuff lives and breeds at temperatures where it should be frozen solid.

  Warmth is not always a good thing. It melts the permafrost. With soil that is as much as three-quarters ice, melting means subsidence. Water flows out of the soil. The ground, melted and drained, sinks. Pools form. The sun warms the pools, setting up convection currents in the water column that pump more heat into the ground. The pools grow wider and deeper. Trees that had once grown on top of the permafrost die in waterlogged conditions. Animal burrows flood. The landscape changes. Build a house on permafrost, and what felt like frozen bedrock beneath the foundation might flow away. The ground might slump. Your house might sag into a water-filled depression. Your neighbors — sourdoughs who know to insulate the ground before they build — might snicker behind your back. Or, this being Alaska, they might laugh in your face. They might invite you to laugh along with them. They might loan you a set of house jacks and offer a deal on a truckload of gravel and cement.

  The warmth can come from climate change — a warm winter, a hot summer, a year when the insulating blanket of snow fails to fall from the sky or disappears in early spring. Or the warmth can come from the hyperactive ambitions of human beings. In the 1800s, Alaskan gold miners who had found gold in streams reasoned that there would be more gold belowground, covered by frozen soil. They built fires in mine tunnels to melt the permafrost, loosening gravel from ancient streams buried well below the surface. Later, boilers were used to generate steam at the mine face. Some miners moved away from tunneling and instead stripped away the entire surface, melting the gold-bearing gravel with strings of pipes pumping water into what were called “thawing points.” By 1929, a single company had more than ten thousand thawing points operating simultaneously near Fairbanks. Two hundred specialized miners, called “point doctors,” pounded the points into the ground and made sure the water flowed. The result: pockmarked ground, thawed and ready for a dredge.

  Occasionally, people have built unheated additions onto their homes for storage or as garages, only to see the heated part of the house descend. The walk to the garage is uphill. Certain cabins in the Alaskan bush seem to have been built at odd angles or with deep sags. In Dawson City, northwest of Fairbanks, two frame buildings built during the Klondike gold rush lean together, the ground beneath warmed by the buildings above. To see them is to wonder just how much these people were drinking when they laid the foundations, but they are due not so much to alcohol as to warming and drunkenly subsiding ground.

  For victims of hypothermia, rewarming can be fatal. The core temperature of victims continues to drop even after they are brought into a warm environment. Some believe this afterdrop to be nothing more than heat loss from the victim’s core to the colder outer layers of the body. Even watermelons, taken from a freezer to a warm kitchen, suffer afterdrop: the warm inner core of the melon loses heat to the colder parts near the rind even as the outer parts begin to warm. Others believe afterdrop occurs when constricted blood vessels near the skin, reacting to the warmer air, reopen, allowing cold blood from the surface to flood the body’s core. To make things worse, the cold blood from the surface may be rich in lactic acids, overstressing an already stressed situation. Worst-case scenario: The cold blood hits the heart, causing ventricular fibrillation. The lower heart chamber quivers. The blood stops moving. The victim drops to the ground. The victim dies. This is more common than one might think. It happened after the School Children’s Blizzard. It happened to the German soldiers pulled from Norwegian coastal waters in 1940. It happened to sixteen Danish fishermen in 1979. The fishermen, in the water for more than an hour, climbed aboard a rescue boat, wrapped themselves in blankets, headed to the cabin for coffee, and one by one dropped dead.

  And then there is frostbite. Apsley Cherry-Garrard, of Scott’s South Pole expedition, wrote of treating frostbite: “Then you nursed back your feet and tried to believe you were glad — a frost-bite does not hurt until it begins to thaw. Later came the blisters, and then the chunks of dead skin.” In Napoleon’s campaigns, the men treated frostbite by warming their frozen extremities next to a fire. As one cannot actually feel a frozen extremity until the extremity warms up, it was not uncommon for Napoleon’s men to burn themselves during rewarming. The men learned to rub frozen extremities with snow. This was painful, too, but it did not cause burns.

  During the School Children’s Blizzard, rubbing with snow was the treatment of choice. Addie Knieriem, a young girl who survived the blizzard, was left with badly frozen feet. As always, the freezing had started in her skin, between the cells. The ice crystals drew water from within the cells, dehydrating the cells themselves. Eventually, the fluid remaining within the cells froze. Ice crystals tore cell membranes. The ice penetrated deeper into her tissues. Blood vessels froze. Tendons froze. Muscles froze. Her rescuers rubbed her feet with snow. As her feet warmed, the feeling returned with a vengeance. She felt as though someone was burning her feet. There would also have been a terrible, insatiable itchiness. Soon after, blood cells clotted in her
feet. The skin blistered. Her toes turned black. Her feet began to rot. Her room would have been filled with the foul stench of gangrene. Her toes were amputated, and then one of her feet. At this point, with limited painkillers, Addie may have wondered if warming up had been the wisest choice.

  Today frostbitten extremities are rewarmed in warm baths. Painkillers are administered. Antibiotics are used. Rubbing with snow is discouraged. Amputations remain common. C. Crawford Mechem, in a 2006 article, says that there are four degrees of frostbite. First-degree frostbite symptoms include swelling, a waxy look to the skin, hard white spots, and numbness. By the time third-degree frostbite occurs, symptoms include “blood-filled blisters, which progress to a black eschar over a matter of weeks.” In fourth-degree frostbite, there is what Mechem calls “full-thickness damage affecting muscles, tendons, and bone, with resultant tissue loss and sensory deficit.” In other words, tissue with fourth-degree frostbite is dead or as good as dead. Addie Knieriem, on the prairie, suffered from fourth-degree frostbite in her feet. On rewarming, Mechem says, one should expect “pain, throbbing, burning, or electric current-like sensations.” The last gasp of rewarmed nerve cells comes with intense cries of pain.

  Warmth can hurt plants and animals accustomed to the cold. On sunny winter days, pine needles absorb heat from the sun. This may, at first glance, seem like a good thing, a chance for a bit of midwinter photosynthesis. But as the needles warm, the water vapor inside them warms, too. The warmed water vapor leaks out of the needles. The pine tree suffers from what is sometimes called winter desiccation.