Natural History

The Surging Ice

In 1986, Hubbard Glacier, north of Yakutat, suddenly decided to surge forward, cutting off Russell Fjord from the rest of the Pacific Ocean. A group of warmhearted but ill-advised wildlife lovers set out to save the marine mammals that had been trapped behind the glacier. Catching a dolphin from an inflatable boat isn't that easy -- they didn't accomplish much, but they provided a lot of entertainment for the locals. Then the water burst through the dam of ice and the lake became a fjord again, releasing the animals anyway. In 2002 it happened again (no rescue this time). Ships were warned away as the 70-square-mile lake, having risen 61 feet above sea level, quickly drained through a 300-foot-wide channel with a whoosh. Geologists say it could happen again any time.

Bering Glacier, the largest in North America (about 30 by 145 miles in area), can't decide which way to go. Surging and retreating on a 20-year cycle, it reversed course in 1995 after bulldozing a wetland migratory bird stopover, and speedily contracted back up toward the mountains. Yanert Glacier surged 100 yards a day in 2000 after moving 100 yards a year since 1942. The next year Tokositna Glacier started galloping after 50 years of quiet. In 1937, surging Black Rapids Glacier almost ate the Richardson Highway. In Prince William Sound, Meares Glacier plowed through old-growth forest. On a larger scale, all the land of Glacier Bay -- mountains, forests, sea floor -- is rising 1 1/2 inches a year as it rebounds from the weight of melted glaciers that 100 years ago were a mile thick and 65 miles longer.

Yet these new and erased lands are just small corrections around the margins compared to all the earth has done in setting down, wiping out, and rewriting the natural history of Alaska. In the last ice age, 15,000 years ago, much of what is Alaska today was a huge glacier. Looking up at the tops of granite mountains in Southeast Alaska, especially in the Lynn Canal, you can see a sort of high-water mark -- the highest point to which the glaciers came in the ice age.

Some 7-year-old children worry about the bogeyman or being caught in a house fire. When I was that age, living with my family in Juneau, I was worried about glacier ice. I had learned how Gastineau Channel was formed, I had seen Mendenhall Glacier, and I had heard how it was really a river of ice, advancing and retreating. I came to fear that while I slept another ice age would come and grind away the city of Juneau.

It's possible that a glacier could get Juneau -- the city fronts on the huge Juneau Ice Field -- but there would be at least a few centuries' warning before it hit. Glaciers are essentially just snow that doesn't get a chance to melt. The snow accumulates at higher elevations until it gets deep enough to compress into ice and starts oozing down the mountainside. When the ice reaches the ocean, or before, the melt and calving of icebergs at the leading edge reaches equilibrium with the snow that's still being added at the top. The glacier stops advancing, becoming a true river of ice, moving a snowflake from the top of the mountain to the bottom in a few hundred years. When conditions change -- more snow or colder long-term weather, for example -- the glacier gets bigger; that's called advancing, and the opposite is retreating. Sometimes something strange will happen under the glacier and it will surge. Bering Glacier started to float on a cushion of water, and Yanert Glacier slid on a cushion of mud. But most of the time, the advance or retreat is measured in inches or feet a year.

It took some time to figure out how glaciers work. The living glaciers of Alaska, like living fossils from the last ice age, helped show the way. In the 1830s, scientists in Switzerland found huge rocks (now called glacial erratics) that appeared to have moved miles from where they had once been a part of similar bedrock. Scientists theorized that ancient glaciers shaping the Alps must have moved the rocks. John Muir, the famous writer and naturalist, maintained in the 1870s that the granite mountains of Yosemite National Park had been rounded and polished by the passing of glaciers that melted long ago (he was only partly right). He traveled to Alaska to prove it. Here, glaciers were still carving the land -- they had never finished melting at the end of the last glacial period -- and Muir could see shapes like those at Yosemite in the act of being created. Glacier Bay, which Muir "discovered" when guided there by his Alaska Native friends, was a glacial work in progress, as it still is today.

When you visit, you can see for yourself how the heavy blue ice and white snow are streaked with black rock and dust that were obviously gouged from mountains and left in hills at the faces and along the flanks of the glaciers, in debris piles called moraines. At Exit Glacier, in Kenai Fjords National Park, you can stand on a moraine that wraps the leading edge of the glacier like a scarf and feel the cold streaming off spires of clicking ice -- like standing in front of a freezer with the door open. Find another hill like that, no matter where it is, and you can be pretty sure a glacier once came that way. Likewise, you can see today's glaciers scooping out valleys in the mountains.

Today, Alaska's 100,000 glaciers cover about 5% of its landmass, mostly on the southern coast. There are no glaciers in the Arctic -- the climate is too dry to produce enough snow. The northernmost large glaciers are in the Alaska Range, such as those carving great chasms in the side of Mount McKinley. At that height, the mountain creates its own weather, wringing moisture out of the atmosphere and feeding its glaciers. The Kahiltna Glacier flows 45 miles from the mountain, descending 15,000 feet over its course. The Ruth Glacier has dug a canyon twice as deep as the Grand Canyon, half filled with mile-deep ice. Similarly, fjords and valleys all over Alaska were formed by the glaciers of 50 ice ages that covered North America in the last 2.5 million years.

The Trembling Earth

Despite my early glacier phobia, I never had a similar fear of earthquakes. Living in Anchorage, I'd been through enough of them that, as early as I can remember, I generally didn't bother to get out of bed when they hit. Alaska has an average of 13 earthquakes a day, or 11% of all the earthquakes in the world, including 3 of the 10 largest ever recorded. On November 3, 2002, Alaska felt the world's largest earthquake of the year and one of the largest ever in the United States. My car rocked as I drove in Anchorage. Waves slopped across the bayous of Louisiana, and geysers at Yellowstone changed their size and period of eruptions. No one died and few people were injured because the quake occurred in such a sparsely populated area, the region between Anchorage and Fairbanks in the Alaska Range east of Mount McKinley. A 140-mile-long crack appeared right across that region, running over mountains and through glaciers. The land on each side moved laterally as much as 22 feet and vertically up to 6 feet. The Glenn Highway section known as the Tok Cut-off, between Glennallen to Tok, broke into many deep cracks. A tractor-trailer fell into one of them. Where the Interior highways crossed the big fault-line crack, lanes no longer lined up and the road got a new jog where it used to be straight.

It's all part of living in a place that isn't quite done yet. Any part of Alaska could have an earthquake, but the Pacific Rim from Southcentral Alaska to the Aleutians is the shakiest. This is where Alaska is still under construction. The very rocks that make up the state are something of an ad hoc conglomeration, still in the process of being assembled. The floor of the Pacific Ocean is moving north, and as it moves, it carries islands and mountains with it. When they hit the Alaska plate, these pieces of land, called terranes, dock like ships arriving, but slowly -- an island moving an inch a year takes a long time to travel thousands of miles. Geologists studying rocks near Mount McKinley found a terrane that used to be tropical islands. In Kenai Fjords National Park, fossils have turned up that are otherwise found only in Afghanistan and China. The slowly moving crust of the earth brought them here on a terrane that makes up a large part of the south coast of Alaska.

The earth's crust is paper thin compared to the globe's forces, and, like paper, it folds where two edges meet. Alaska's coast is bending down; farther inshore, where McKinley stands, it is bowing up. At Kenai Fjords National Park, you can see steep little rock islands flocked with birds: They are old mountaintops, shrinking down into the earth. The monolith of McKinley is a brand-new one growing higher.

Here's how it works: Near the center of the Pacific, underwater volcanoes and cracks that constantly ooze molten new rock are adding to the tectonic plate that forms the ocean floor. As it grows from the middle, the existing sea floor spreads at a rate of perhaps an inch a year. At the other side of the Pacific plate, where it bumps up against Alaska, there's not enough room for more crust, so it's forced, bending and cracking, downward into the planet's great, molten, recycling mill of magma. Landmasses that are along for the ride smash into the continent that's already there. When one hits -- the so-called Yakutat block is still in the process of docking -- a mountain range gets shoved up. Earthquakes and volcanoes are byproducts.

Living in such an unsettled land is a matter of more than abstract interest. The Mount Spurr volcano, which erupted most recently in 1992, turned day to night in Anchorage, dropping a blanket of ash all over the region. A Boeing 747 full of passengers flew into the plume and lost power in all its engines, falling in darkness for several minutes before pilots were able to restart the clogged jets. After that incident, the airport was closed until aviation authorities could find a way to keep volcanic plumes and planes apart. In the winter of 2005-06, the Anchorage airport repeatedly closed due to minor eruptions of Augustine Volcano, west of Homer. More than 80 volcanoes have been active in Alaska in the last 200 years. Earthquakes between 7 and 8 on the Richter scale -- larger than the 1994 Los Angeles quake -- occur once a year on average, and huge quakes over 8 averaged every 13 years over the last century. The worst of the quakes, on March 27, 1964, was the strongest ever to hit North America. It ranked 9.2 on the Richter scale, twisting an entire region of the state so land to the west sank 12 feet while on the east it rose 30 feet. More land moved laterally than in any other recorded earthquake as well. The earthquake destroyed much of Anchorage and several smaller towns, and killed about 131 people, mostly in sea waves created by underwater landslides. In Valdez, the waterfront was swept clean of people. In the Prince William Sound village of Chenega, built on a hill along the water, people started running for higher ground when the wave came. About half made it.

But even that huge earthquake wasn't an unusual occurrence, at least in the earth's terms. Geologists believe the same Alaska coast sank 6 feet in an earthquake in the year 1090.

The Frozen Tundra

The northern Interior and Arctic parts of the state are less susceptible to earthquakes and, since they receive little precipitation, they don't have glaciers, either. But there's still a sense of living on a land that's not permanent, since most of northern Alaska is solid only by virtue of being frozen. When it thaws, it turns to mush. The phenomenon is caused by permafrost, a layer of earth a little below the surface that never thaws -- or at least, you'd better hope it doesn't. Buildings erected on permafrost without some mechanism for dispersing their own heat -- pilings, a gravel pad, or even refrigerator coils -- can thaw the ground below and sink into a self-made quicksand. With the climate warming, sections of the trans-Alaska pipeline are leaning, and many miles of highway in Interior Alaska are being rebuilt each year because the ground they traverse has turned to mush due to increased average temperatures (more on this below).

The Arctic and much of the Interior are a swampy desert. Annual precipitation measured in Barrow is the same as in Las Vegas. Most of the time, the tundra is frozen in white; snow blows around, but not much falls. It melts in the summer, but the water can't sink into the ground, which remains frozen. Liquid water on top of the permafrost layer creates huge, shallow ponds. Alaska is a land of 10 million lakes, with 3 million larger than 20 acres. Birds arrive to feed and paddle around those circles and polygons of deep green and sky blue.

Permafrost makes the land do other strange things. On a steep slope, the thawed earth on top of the ice can begin to slowly slide downhill like a blanket sliding off the side of a bed, setting the trees at crazy angles. These groves of black spruce -- the only conifer that grows in this kind of ground -- are called drunken forests, and you can see them in Denali National Park and elsewhere in the Interior. Permafrost also can create weird tundra, with shaky tussocks the size of basketballs that sit a foot or two apart on a wet, muddy flat. From a distance it looks smooth, but walking on real basketballs might be easier. In other places, freezing and thawing processes create ponds with straight sides and sharp corners, polygons that appear manmade.

The permafrost also preserves many things. Although few and far between, tractor tracks remain clearly delineated for decades after they're made, appearing as narrow, parallel ponds reaching from one horizon to the other. The meat of prehistoric mastodons, still intact, has been unearthed from the frozen ground. On the Arctic Coast, the sea eroded ground near Barrow that contained ancient ancestors of the Eskimos who still inhabit the same neighborhood. In 1982, a family was found that apparently had been crushed by sea ice up to 500 years ago. Two of the bodies were well preserved, sitting in the home they had occupied and wearing the clothes they had worn the day of the disaster, perhaps around the time Columbus was sailing to America.

Sea ice is the frozen ocean that extends from northern Alaska to the other side of the world. For a few months of summer, it pulls away from the shore. Then, in October, icebergs floating toward land are cemented together by new ice forming along the beach. But even when the ice covers the whole ocean, it still moves under the immense pressure of wind and current. The clash creates towering pressure ridges -- piles of broken ice that look like small mountain ranges and are about as difficult to cross.

The National Weather Service keeps track of the ice pack and issues maps and predictions you can find on the Internet (www.arh.noaa.gov). Eskimo hunters traveling on the ice by snowmobile need this information, as do crabbers who tempt disaster by fishing the south-moving ice edge in the fall, and shippers looking for the right moment in the summer to venture north with barges of fuel and other supplies for the coast of the Arctic Ocean. Sometimes there is barely time in the summer to get there and back before the ice closes in again in the fall.

The Rainforest

By comparison, southern coastal Alaska is warm and biologically rich. Temperate rainforest ranges up the coast from Southeast Alaska into Prince William Sound, with bears, deer, moose, wolves, and even big cats living among the massive western hemlock, Sitka spruce, and cedar. This old-growth forest, too wet to burn in forest fires, is the last vestige of the virgin, primeval woods that seemed so limitless to the first white settlers who arrived on the east coast of the continent in the 17th century. The trees grow on and on, sometimes rising more than 200 feet high, with diameters up to 10 feet, and falling only after hundreds or even thousands of years. When they fall, the trees rot on the damp moss of the forest floor and return to soil to feed more trees, which grow in rows upon their nursery trunks.

Here at least, Alaska does seem permanent. That sense helps explain why logging the rainforest is so controversial. Just one of these trees contains thousands of dollars' worth of wood. Vast Southeast lands owned by Alaska Native corporations were stripped of their old trees for the money they brought to their owners. But the great majority of this rainforest land belongs to the federal government, and a combination of environmental campaigns and economics put a stop to large-scale logging on that land while most of it remained virgin. When the Southeast Alaska logging economy died in the 1990s, the towns there suffered heavy economic blows. Tourism is taking the place of logging (with its own environmental and cultural impacts), but deep antipathy remains against logging opponents.

The rivers of the great coastal forests bring home runs of big salmon, clogging in spawning season like a busy sidewalk at rush hour. The fish spawn only once, returning by a precisely tuned sense of smell to the streams where they were hatched as many as 7 years before. When the fertilized eggs have been left in the stream gravel, the fish conveniently die on the beach, making a smorgasbord for bears and other forest animals. The huge Kodiak brown bear, sometimes topping 1,000 pounds, owes everything to the millions of salmon that return to the island each summer. By comparison, the grizzly bears of the Interior -- the same species as browns, but living on grass, berries, and an occasional ground squirrel -- are mere midgets, their weight counted in the hundreds of pounds. Forest-dwelling black bears grow to only a few hundred pounds.

Forests of Fire

Rainforest covers only a small fraction of Alaska. In fact, only a third of Alaska is forested at all, and most of this is the boreal forest that covers the central part of the state, behind the rain shadow of coastal mountains that intercept moist clouds off the oceans. Ranging from the Kenai Peninsula, south of Anchorage, to the Brooks Range, where the Arctic begins, this is a taiga -- a moist, subarctic forest of smaller, slower-growing, hardier trees that leave plenty of open sky between their branches. In well-drained areas, on hillsides and southern land less susceptible to permafrost, the boreal forest is a lovely, broadly spaced combination of straight, proud white spruce and pale, spectral paper birch. Along the rivers, cottonwoods grow, with deep-grained bark and branches that spread in an oaklike matrix -- if they could speak, it would be as wise old men.

Forest fires tear through Alaska's boreal forest each summer. In the newly warmed climate, million-acre years have become common, and in 2004, a record 6.5 million acres burned -- an area the size of Massachusetts. It's impossible to fight that much fire. Alaska has always allowed fire to take its course unless structures or certain resources are at risk. In most cases, forest managers do no more than note the occurrence on a map. Unlike the rainforest, there's little commercially valuable timber in these thin stands, and, anyway, trying to halt the process of nature's self-immolation would be like trying to hold back a river with your hands. The boreal forest regenerates through fire -- it was made to burn. The wildlife that lives in and eats it needs new growth from the burns as well as the shelter of older trees. When the forest is healthiest and most productive, the dark green of the spruce is broken by streaks and patches of light-green brush in an ever-changing succession.

This is the land of the moose. They're as big as large horses, with a long, bulbous nose and huge eyes that seem to know, somehow, just how ugly they are. Their flanks look like a worn-out shag carpet draped over a sawhorse. But moose are survivors. They thrive in land that no one else wants. In the summer, they wade out into the swampy tundra ponds to eat green muck. In the winter, they like nothing better than an old burn, where summer lightning has peeled back the forest and allowed a tangle of willows to grow -- a moose's all-time favorite food. Eaten by wolves, hunted and run over by man, stranded in the snows of a hard winter, the moose always come back.

In the summer, moose disperse and are not easily seen in thick vegetation. In the winter, they gather where walking is easy, along roads and in lowlands where people also like to live. Encounters happen often in the city, until, as a resident, you begin to take the moose for granted, or see them as a pest that eats decorative plantings and blocks bike trails. Then, skiing on a Nordic trail one day, you round a corner and come face to face with an animal that stands 2 feet over you. You can smell the beast's foul scent and see his stress, the ears pulled back on the head and the whites of the eyes showing, and you know that this wild creature, fighting to live till summer, could easily kill you.

Light & Darkness

There's no escaping the stress of winter in Alaska -- not for moose or people -- nor any shield from the exhilaration of the summer. In summer, it never really gets dark at night. In Fairbanks in June, the sun sets in the north around midnight, but it doesn't go down far enough for real darkness to settle, instead rising again 2 hours later. It's always light enough to keep hiking or fishing, and, in clear weather, it's always light enough to read. You may not see the stars from early May until sometime in August. Visitors have trouble getting used to it: Falling asleep in broad daylight can be hard. Alaskans deal with it by staying up late and being active outdoors.

In the winter, on the other hand, you forget what the sun looks like. Kids go to school in the dark and come home in the dark. The sun rises in the middle of the morning and sets after lunch. At high noon in December, the sun hangs just above the southern horizon with a weak, orange light, a constant sunset. Animals and people go into hibernation.

As you go north, the change in the length of the days gets bigger. In Ketchikan, the longest day of the year, on the June 21 summer solstice, is about 17 hours, 20 minutes; in Fairbanks, 22 hours; and in Barrow, the longest day is more than 2 months. In contrast, in Seattle, the longest day is 16 hours, 15 minutes; and in Los Angeles, 14 hours, 30 minutes. On the equator, days are always the same length, 12 hours. At the North Pole and South Pole, the sun is up half the year and down the other half.

The best way to understand this is to model it with a ball and a lamp. The earth spins on its axis, the North and South poles, once a day around. When the axis is upright, one spin of the ball puts light on each point on the ball equally -- that's the spring and fall equinox, March 21 and September 21, when the day is 12 hours long everywhere. In the summer, the North Pole leans toward the light and the Northern Hemisphere gets more light than darkness, so during the course of one rotation, each northern spot is lighted more than half the time. In winter, the Southern Hemisphere gets its turn, and more than half the Northern Hemisphere is in shadow, meaning shorter days. As you go farther north in winter, the shadow gets larger, and the day in any one spot shorter. But no matter how the axis leans, the equator is always half light and half dark, like the entire globe as a whole.

In the North, on a long summer evening, you can almost feel the planet leaning toward the sun. The world lies under a bright, endless dome. In the winter, darkness falls as deep as space, and you can almost feel the earth's warmth wafting away into the universe as the freeze sinks ever deeper in the land. Now the rainforest rivers and permafrost lakes are hard ice, the salmon are away at sea, and the bears are asleep. The moose and other wintering animals burn their summer fat, a finite store of provisions that may or may not last. Up in the mountains, the glaciers grow.

The Warming Climate

In the past 2 decades, winters have warmed and shortened and summers have gotten hotter. Individual years are sometimes closer to the long-term norm, but the trend is for warming. Years of bizarrely warm weather have become common and records have been broken so often they are hardly noted. In Anchorage, where I live, that has meant ski seasons ruined by rainy weather, massive insect kills of trees, and extraordinary forest fire danger, among many other changes. My friends and I, who grew up in Anchorage, never heard thunder until our teens; now it's commonplace, even early in the summer. Starting in the summer of 2004, the ocean warmed so much we were able to swim in it in places. That's never been possible before in my 44-year life. Alaska didn't even smell like Alaska that summer. Something about how the sun heated the ground and the plants created an odor I remember from travels in the Lower 48, not here.

In Arctic Alaska, the changes are much more pronounced: Sea ice is withdrawing from shore, catastrophic erosion washing away bluffs and villages, permafrost softening and giving way, winters warming and shortening, and ecosystems becoming disrupted as plant and animal life is stressed by the new conditions. A team of 300 scientists from all the Arctic nations, including the United States, completed a 4-year Arctic Climate Impact Assessment in 2004 and 2005. The report documents the changes and says they were largely driven by human carbon dioxide emissions. It predicts more changes, most of them negative. For example, if the sea ice continues to melt at the current rate, this century will see the end of the ecosystem that lives upon it, including the likely extinction of the polar bear.

Carbon dioxide warms the earth by trapping the heat of the sun in the atmosphere, a phenomenon understood since the late 1800s. Climate records reconstructed from ancient ice show the amount of carbon dioxide in the atmosphere has closely matched average temperature and climate conditions for more than 400,000 years. Due to human burning of fossil fuels, the carbon dioxide level in the atmosphere now is higher than at any time in that period. And now Arctic temperatures are rising at a rate that appears unprecedented in thousands of years.

Does this mean adjusting your plans as a visitor? Yes and no. Tourists in recent years have enjoyed sunny weather, but also suffered through forest fire smoke and rainy skiing. But how the changes will play out in any particular year cannot be predicted, just as you cannot set your vacation dates based on a TV weather forecast. On the other hand, we may all need to adjust our plans. The amount of carbon dioxide each of us is responsible for emitting relates directly to the nonrenewable energy we use. You can help save Alaska by carpooling or turning off an extra light.

I've written a book on this subject, The Whale and the Supercomputer; On the Northern Front of Climate Change (North Point Press, $14), which tells the story of how Alaska's Iñupiat and scientists are experiencing and learning about the changing climate. You can read more about it on my website, at www.wohlforth.net.