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The Ice at the End of the World

An Epic Journey into Greenland's Buried Past and Our Perilous Future

by Jon Gertner

More books on Science and Inventions

In 1961 - the year before he became the anchorman for CBS News - Walter Cronkite visited Camp Century, an unusual military compound on the Greenland ice sheet. Carved under the snow and ice, Camp Century had a main street and prefab housing for 250 soldiers and scientists - all powered by a pint-sized nuclear reactor. To get there, Cronkite endured a multiday haul from the edge of the ice sheet by 'wanigan' - a heated, insulated trailer hitched to a massive Caterpillar tractor traveling at the speed of a slow-walking human.

Cronkite's televised report was wide-eyed at the base's scale and audacity - there were mess halls, a church, and even the hair-cutting services of a barber named Jordon. When Cronkite asked Camp Century's commanding officer, Tom Evans, about his objectives, Evans rattled off three: "The first one is to test out the number of promising new concepts of polar construction. And the second one is to provide a really practical field test of this new nuclear plant. And, finally, we're building Camp Century to provide a good base, here, in the interior of Greenland, where the scientists can carry on their R&D activities."

When Evans talked to Cronkite, some researchers and soldiers working at Century were aware that his answer was not entirely forthright. There was another project at the encampment that Evans did not discuss. In trenches under the ice about a quarter mile from the main camp, an Army Corps engineer was secretly moving massive hunks of pig iron on a flatbed rail car - thousands of pounds of raw metal meant to approximate the weight of an intermediate range ballistic missile.

Many decades later, long after Camp Century had been abandoned, it would come to light that the US military was proposing something called the Iceworm system: a nuclear arsenal of 600 ballistic missiles, trained toward the Soviet Union, which would be in constant motion by rail under the Greenland ice sheet. Iceworm was never built. The military soon understood that Camp Century was doomed. At best it would last 10 years, they acknowledged, at which point the overburden of snow would push down on the roof, compress the walls, and thus destroy it.

Camp Century was a perfect example of Cold War paranoia and eccentricity: an improbable outpost that was expensive to build, difficult to maintain, and unpleasant to live within. The irony was that Camp Century was also the site of an inspired and historic engineering experiment. It just happened to be an experiment that the US Army didn't care that much about. In fact, the importance of the research project being conducted at Camp Century wouldn't be truly understood for decades.

It was there, in a cavern located dozens of feet below the surface of snow and ice, that scientists were perfecting a new method that would allow them to read Earth's history. A small number of glaciologists had already come to understand that the ice sheet probably contained a frozen archive of long-ago events and temperatures - that it was encrypted, in some yet-to-be-deciphered way, with a code to the past.

This code was locked within the ice amid the snow crystals that had fallen thousands of years before. The working assumption was that by drilling into the ice you could pull up a sample - a cylinder of ice that became known as a core - and use laboratory tools to unlock mysteries from the past. The deeper you drilled down, the farther you went back in time.

"The army allowed us to freeload with them," recalls Chet Langway, the geologist who was in charge of cataloging and analyzing the ice cores at Camp Century. And since the army was maintaining the appearance that the camp was for scientific research rather than for nuclear missile research, officials at Camp Century welcomed the prospect of showing visitors what the drillers were up to. Cronkite visited the early stages of the drilling project. "We were sort of a cover, if you will," Langway says, even though his team's goal - to reach bedrock - was deeply serious.

THE MASTERMIND OF the experiment at Camp Century was a dapper and sometimes irritable former professor named Henri Bader. Since the mid-1950s, Bader had worked as the chief scientist at the Army Corps' Snow, Ice, and Permafrost Research Establishment, known as SIPRE. Like Camp Century, this small organization was a product of the Cold War.

In a new world order where the United States was locked in competition with the Soviet Union, the geographical area separating the two superpowers comprised a vast frozen wasteland at the top of the world. SIPRE was created to help the army manage its troops in those frozen wastes - to research the properties of snow and ice so that men and women deployed to the far north could fight better, move better, work better.

A man of medium height with a goatee and thinning, combed-back hair, Bader smoked heavily and carried himself with an intimidating air that bordered on imperiousness. He was a genius at mixing the practical needs of the military with his own curiosity and goals. To Bader, the layered ice sheet promised to capture a year-by-year record of climactic and atmospheric history, meaning that if one could figure out how to read precise temperatures in these layers, one would find (as Bader put it) "a treasure trove."

Just as important, the layers were depositional: Everything in Earth's atmosphere had been deposited there along with the snow that turned to ice. In theory, that meant that an ice core from deep in the ice sheet would contain telltale vestiges from, say, the start of the industrial revolution, and include evidence of how atmospheric gases and pollution intensified over time.

An ice core might likewise contain traces of ash that blanketed the earth after the volcanic explosions of Krakatoa in Indonesia (in 1883) or maybe even Vesuvius, near Pompeii (in 79 AD). And judging by how thick the center of the ice in Greenland appeared to be, the record might go back much, much further.

Moreover, trapped in the ice sheet were bubbles of air. In the late 1940s and early 1950s, Bader worked on bubbles in some early ice cores drilled in Alaska. "He could see the bubbles were under pressure," his SIPRE colleague Carl Benson recalls. "Now, the bubble is recording the atmosphere at the time the bubble is sealed off. And in other words, these little bubbles in the ice have a history of what the climate was like at the time. He knew this. We knew this, but it was a question of: How do you measure it?"

Bader did not expect to find answers quickly. But he saw that the extraction of what he called 'deep cores' from the ice sheet would be the first step to unlocking those secrets. The drilling group made some test holes, with mixed results, in 1961 and 1962. The effort to go from top to bottom began in earnest in October 1963. Bader estimated the distance was about a mile down. He expected the drilling team would reach near to bedrock in four months.

DRILLING RIGS THAT are customized to recover ice cores are fantastically complicated contraptions. To work properly, these machines must go a mile or two down a narrow hole, digging into the ice inch by inch. During this process, a length of core - a cylinder of ice anywhere from 3 to 10 feet - must safely be carved out of the ice sheet, gripped, severed, and pulled to the surface by a winch. Then the drill must go back down and carve deeper. For the Camp Century drilling, Henri Bader suggested creating a new kind of drill, one that would use a hollow-tipped 'thermal' bit - a hot ring of metal that melted the ice as it went down and produced long cylinders of the ice core.

Keeping the ice in rigorous order would be just as crucial as a good drill. If a team lost track of the sequence in which the cores came out of the ice the scientists could lose track of climate history and jeopardize their entire experiment. For that reason, on most summer days during the early 1960s, the cores that reached the surface in Camp Century's drilling trench were carefully bagged and logged and stored in cardboard tubes on racks against the wall.

Before they were put away, however, Chet Langway would usually look them over closely on a light table. Cores that came from closer to the surface exhibited seasonal stripes, and sometimes pockets of frozen dust, suggesting remnants of an ancient volcanic eruption or dust storm. But as the drill reached farther down, the cores were less obviously marked with annual layers.

What's more, Langway could see that some cores came to the surface hazy and loaded with bubbles, resembling cylinders of frozen milk, whereas deeper ice emerged clear like glass - only to become hazy a few weeks later as gases that had been under tremendous pressure deep in the ice sheet coalesced back into bubbles. Some of the cloudy, bubbly ice could be as fragile as crystal stemware. Minutes after retrieving it from the drill's core barrel, Langway could see it fracture, and hear it crackle, as the air inside 'relaxed' in reaction to the pressure changes at the surface.

Herb Ueda was usually the technician in charge of the day-to-day drilling work. He would typically fly in to Camp Century every April and stay until September. By his own assessment, his family was dirt poor. He grew up in the Northwest and often worked as a laborer alongside his parents in crop fields and orchards. After the attack on Pearl Harbor in December 1941, Ueda and his family were forced by the American government to move from the Tacoma, Washington, area to Idaho, to an internment camp for Japanese-Americans. For three years, his family lived in what was essentially a concentration camp, ringed with barbed wire, with about 9,000 other Japanese-Americans.

Ueda nevertheless finished high school, got drafted, and served in the US Army. Afterward, he pursued a degree in mechanical engineering at the University of Illinois. He was 29 and setting out to find work in Chicago, when in the course of interviewing for jobs he got a call from "some kind of a snow and ice lab." It was SIPRE. The next summer, Ueda flew to Greenland and learned how to drill holes in ice.

Ueda was much less focused on what the cores might say about the history of the Earth than how to get them out of the ice sheet. He soon knew every quirk and problem of the drilling rig. It was slow and difficult work, and Ueda was increasingly frustrated by the thermal drill. On average, it melted through the ice sheet at only about 1 inch per minute.

In 1964, on a field trip to Oklahoma, several Army Corps engineers discovered an old oil rig. "They found it abandoned, in some cornfield somewhere," Ueda recalled. "The owner offered to sell it to us for $10,000, so we bought it, and we modified it to work in ice." This 'electrodrill' was shipped by air to Camp Century in the spring of 1965.

It was an ungainly machine - 83 feet long and weighing 2,650 pounds, not including the drilling tower and 8,000 feet of thick cable that provided the drill's stability and power. At the tip, the electrodrill had a hollow, circular cutting bit studded with diamonds that rotated at a rate of 225 revolutions per minute. "We were getting cores 20 feet long with this drill," Ueda recalls of the summer of 1965. "And so you can cover a lot of depth like that. On a good day we could do more than 100 feet."

Now Ueda was moving fast. This was a bit of needed encouragement, because by the end of summer, Camp Century was beginning to collapse around him. Inside the trenches, heat from the buildings, humans, and machinery was softening and destabilizing the floors and walls. Main street - the wide trench that ran through the center of camp - was bedded with what Langway recalls as filthy white quicksand.

At the same time, snow falling on the surface 40 feet above was piling up and pushing down on the ceilings. To live in Camp Century, residents had always needed to master their fear of a catastrophic collapse. But things were getting worse. As many as 50 men were on duty and tasked with shaving and trimming the walls and ceilings - usually with chain saws - to maintain the camp's viability. It was a losing battle.

In the late spring of 1966, the team returned to Trench 12 and started up the electrodrill. Their coring work was still the same: cut, grip, sever; pull the core up for capture and analysis; repeat. On July 4, 1966, they hit bedrock at 4,450 feet. A photo exists from the day that Ueda reached bottom: Wearing army fatigues and an insulated hat, he stands beside a long cylinder of ice and rock that has been slid from a drilling sleeve onto a trough for observation. He looks fairly amazed and also relieved. Ueda would later recall that it was the most satisfying minute of his career. It had taken six years to get there.

To celebrate the accomplishment, some of the men at Century took a small chip of ice from a core that approximately dated to the birth of Christ and toasted the occasion by putting it in a glass of Drambuie.

The summer of 1966 marked Camp Century's final season as an army base. The nuclear reactor would eventually be moved stateside, but it was first taken back to the military base at Thule, 140 miles away, along with Camp Century's wanigans, tractors, and trucks. But almost everything else was left in the Camp Century trenches: prefabricated huts that served as dorms and mess halls, tables, chairs, sinks, mattresses, bunks, urinals, the billiards table. Waste products from the camp - human sewage, diesel fuel, toxic chemicals such as PCBs, and radioactive coolant from the reactor - were left behind, too.

The working assumption was that everything would soon be crushed by the overburden of snow anyway. And after that, it would be locked forever into the ice sheet.

CHET LANGWAY, THE ranking scientist, left Camp Century with more than a thousand ice cores. In time, they would prove to be the only thing of lingering value that came out of the military's strange Camp Century experiment. He used army transport planes to ship the ice to a freezer near Hanover, New Hampshire, which was where he was now working.

Langway went around the world looking for help in interpreting the trace gases and shreds of evidence in the Camp Century cores. One of his eventual scientific partners had already become fascinated with the work in Greenland. In 1964, a Danish scientist named Willi Dansgaard had visited Camp Century with some colleagues from Copenhagen to conduct a chemistry study on the ice sheet. Dansgaard never actually made it to the drilling trench during his trip. Nor did he get to meet Langway or Herb Ueda at that time. He was informed by one of the camp's military officers that he was unauthorized to observe the coring experiment.

But just hearing about it sharpened his obsession with its potential. In his diary Dansgaard wrote: "What a shame ...What the Americans are going to do with the ice core is unknown." Later, back in Denmark, musing about the drilling experiment again, he concluded that the Camp Century ice "would be a scientific gold mine for anyone who got access to it."

In 1966, when he heard of the coring's completion, he wrote Chet Langway a letter and proposed doing an analysis of the ice. One of Dansgaard's students would later say, "That letter is the birth certificate of ice core climate research."

Ice scientists are detectives at heart. Dansgaard was by that point one of the pioneers of measuring oxygen isotopes. These are the naturally occurring variations that reflect whether an oxygen atom has six or eight neutrons in its nucleus. The differences are expressed by comparing the prevalence in a water sample of the heavier and rarer isotope (18O) to the lighter and more common isotope (16O).

Dansgaard began some of this work in 1952, when he collected rainwater in his yard with a beer bottle and a funnel. What he then began to understand was that warm-weather storms produce moisture with a higher percentage of 'heavy' 18O than cold-weather storms. He made a further leap and soon concluded that the temperature of a cloud helps determine the amount of 18O in the snow or rain it produces. In essence:

Higher temperature = a higher concentration of 18O in H2O

Lower temperature = a lower concentration of 18O in H2O

Dansgaard surmised this made it possible to connect the oxygen makeup in the water of old ice with climate. In other words, if he had a sample from a deep ice core that could be dated to an approximate year, he could likely measure the concentrations of 18O in the ice. Then he could look at the results and discern the temperature of the surface air on the day the snowflakes fell to earth, even if it was 10,000 or 15,000 years ago.

The tool he used to do this was known as a mass spectrometer. Dansgaard prepared a sample of ice by processing it with carbon dioxide in a sealed container and then feeding part of the mixture into a small vacuum chamber. The instrument - the mass spec, as they called it in the lab - then bombarded the sample with electricity so as to charge its oxygen molecules; once charged, the sample could then be separated into the heavier and lighter components by passing it through a magnetic field.

The physics were complex but the outcome was simple: Within the machine, the heavy and light oxygen isotopes from the ice sample could be detected and their concentrations measured.

"I offered to measure the whole ice core from top to bottom," Dansgaard recalled of his 1966 offer to Langway, and Langway readily agreed. Dansgaard and several associates flew from Copenhagen to New Hampshire. The men cut 7,500 samples of the Camp Century ice core and brought them back to Denmark, where Dansgaard had technicians working long hours in his mass spec lab.

Out of that big trove of ice, he formulated his first study. On October 17, 1969, Dansgaard's team and Langway published the results in the journal Science, entitled "One Thousand Centuries of Climatic Record from Camp Century on the Greenland Ice Sheet." Dansgaard created a graph tracing the oxygen isotopes - and, in effect, the climate - back approximately 100,000 years.

Langway recalls, "When Willi made that, he shocked the world. Because one of the most difficult things to look at is the temperatures of the past. How do you get that information? You can’t get it by carbon-dating rocks. It doesn't work. But it can with gases in ice, if you've got a tag on their age."

In the Science article, Dansgaard wrote, "It appears that ice-core data provide far greater, and more direct, climatological detail than any hitherto known method." It was nevertheless clear to him that his study wasn't perfect. Many parts of the ice core were hard to read, and it seemed to be the case that chaotic changes in temperature characterized Earth's climate at various points during the period that stretched from 10,000 to 15,000 years before the present era.

This would have been about the time that the Earth was emerging from the last ice age. The period of wild, swinging indicators could have been some noise in the climate signal, errant pulses of information that need not be taken literally, for they might have originated in ice that had flowed and folded over bumps in the Greenland bedrock.

Then again, it might suggest something else with pressing importance in our own era: that climate can change quickly and drastically.

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