Penetrating polar ice

The prospect of trekking up to Greenland, drilling into its ice sheet, and extracting a core to bring back and analyze in a freezing laboratory was an idea that, in the pre-World War II United States, attracted no one. Midwesterners know winter cold about as well as anybody, of course, but the country as a whole has no particular cultural affinity for the world of glaciers. European boys like Alfred Wegner may have grown up dreaming of heroic exploits on the polar ice, but the dreams of American youth were more likely to be set in warmer climes.Whatever territorial claims to the far north of Greenland that the polar expeditions of the American Robert Peary had established at the turn of the century were bartered away at the first opportunity in a telling transaction with Denmark in 1917. The United States ceded to the Danes all interests in northern Greenland and paid an additional $25 million in gold in exchange for the Virgin Islands. Norwegian hunters and fishermen kicked up a fuss when Denmark subsequently claimed Greenland as a colony, but there were not many complaints in the United States about the deal. Even as the importance of Greenland's weather to the growing trans-Atlantic aviation industry was becoming increasingly evident, among researchers in the United States the study of ice caps and glaciers was somebody else's science.

In 1940, German troops invaded Denmark and soon established a valuable radio aviation weather station on the east coast of Greenland. In 1941, the United States agreed to protect Denmark's sovereignty while using Greenland militarily to help secure the status quo in the Northern Hemisphere. The U.S. Coast Guard destroyed the German weather station in 1944, and the United States fought off several attempts by the Germans to regain a weather observation foothold in Greenland. Weather forecasts from Greenland were critical to the operations of Allied forces in the North Atlantic.

In 1947, the war over, Denmark asked that the 1941 Greenland agreement be rescinded. By then, however, the United States had laid claim to a new territorial interest in the region. Terms of an agreement that was finally reached in 1951 gave the United States the right to build an air force base at Thule and to member states of the North Atlantic Treaty Organization the right to use all military facilities on the island. In the 1950s, as the chill of the Cold War descended, the United States Army had a new adversary in mind and new national imperatives. It was intent on maintaining a strategic presence in Greenland to keep a close polar eye on the Soviet Union. Before long, the Distant Early Warning system formed a necklace of 63 radar stations along the 69th parallel from northwestern Alaska through central Greenland.

Pursuing a new interest in the geophysics of cold regions, the Army created a new unit within its Corps of Engineers. The Snow, Ice and Permafrost Research Establishment first set up shop at the University of Minnesota at St. Paul and then moved into its own special laboratory in Wilmette, Illinois, north of Chicago. The Pentagon's choice to develop the new science program was a young Swiss geologist, then teaching at Rutgers University in New Jersey, who had called the military's attention to the lack of cold regions research in the United States.

Henri Bader had spent the war years in various mining enterprises in South America and the West Indies, although he was best known in the United States as an authority on snow. A student of the eminent Swiss geologist Paul Niggli, Bader in 1938 had written the first chapter of Snow and Its Metamorphism, a famous work on the subject that the U.S. Army translated from the German and published in 1954. The War Department General Staff had sent Bader to Europe to survey the state of the art of cold regions research in England, France, Switzerland, and Germany, where ice and snow and alpine glaciers had been studied for years, and it was his report on the subject in 1947 that spearheaded the creation of the Army's new lab.

What most interested European researchers about alpine glaciers, aside from their inclination to collapse into dangerous avalanches, were the patterns they left on the landscape during their long-term advances and retreats in response to climate fluctuations. These telltale patterns and deposits, the moraines of rubble and the boulders left in odd places, were central to Louis Agassiz's successful argument for the existence of ice ages in Earth's history, one of the great achievements of nineteenth-century geology and a subject that continues to enthrall scientists. It was this line of geological thought—the grand movement of glaciers in response to long-term climate change—that became the frame of reference and the standard for the timescale of change for generations of earth scientists.

What most interested Henri Bader, however, was a very different line of thought that was first taken up by Ernst Sorge at Eismitte. Looking at glaciers through the eyes of a mineralogist, Bader wanted to learn everything there was to know about their actual content. His years of mining in Argentina and Colombia may have inspired this thinking of snow and ice as a special kind of ore that was worthy of very close examination. Bader traveled to Alaska as a member of a pioneering expedition that drilled 100 meters into the Taku Glacier and extracted a core. This early exploratory work in ice from a temperate region, the Juneau Icefield, wasn't exactly what he had in mind, but it seemed to prove the concept. It was Henri Bader's audacious ambition, in the mid-1950s, to find a way to penetrate the ice caps of Greenland and Antarctica and investigate the composition of polar ice in ways that would reveal its finest details. This brilliant idea was inspired by a singular insight: that locked in the polar ice is a unique record of atmospheric conditions going far back in time.

Bader believed that polar ice contains information that is obscured in the ice of glaciers in warmer climates. Rain and heavy summer melting cause water to percolate deeply through the critical high-elevation "accumulation area" of glaciers in temperate climates, Bader observed, and so "washes out much of the detail of the record of past precipitation." In contrast, in the perpetual cold of polar climates, summer temperatures remain below freezing, so all precipitation falls as snow, depositing layers that remain frozen and "dry" and relatively unchanged. To Bader this was a vital difference. It meant that "the detail" was intact; the sequence of weather and climate events at high latitudes was preserved, each year layered upon the other, like the growth rings of a tree, a faithful record of climate history.

That was his theory, at least. But exactly what were these mysteries in the polar ice? Were they really worth solving? Was it even physically possible to drill into a polar ice cap and extract a core? And exactly how would one go about deciphering the information extracted? It was totally exploratory, and it looked very expensive and troublesome. No one had succeeded in boring into the polar ice at any great depth and, in fact, no one could say with any certainty in the mid-1950s that, mechanically speaking, it could be done. A critical and unlikely moment in the history of climate science was at hand.

Here was a European, an irascible, urbane alpine scientist, espousing a very European idea about the scientific value of studying glaciers—not their advances and retreats over geological time, like most glaciologists, but their actual content. Here he was, chief scientist of a research and engineering laboratory with the wherewithal of the American military and a national security mission to find out everything there was to know about cold regions. To the Army brass in the 1950s, polar ice was most interesting as a kind of amorphous rock, a potential building material, as surfacing for landing strips and possibly bomb shelters. However, what interested the Army most about the ice cap was not what it might reveal but what it might hide. Could it hide intercontinental ballistic missiles? Could it hide tanks and even aircraft? Even with the demands of the Korean War being felt, the military's Cold Warriors were going to follow this line of thought as far as it would take them. The Army and its engineers wanted to know about the hardness of the ice, its tensile strength, and its deformation characteristics. Deep-time, deep-core ice research into ancient climates was not on their drawing boards.

So what in the world could bring together Bader's bold yet almost dreamy expectations that something scientifically valuable would come of deep-core drilling and the U.S. military's totally pragmatic determination to conquer the ice? As it happened, Bader had some remarkably good timing on his side.

The summer of 1957 would mark the beginning of a unique global scientific undertaking known as the International Geophysical Year, or IGY. Nations on both sides of the Iron Curtain somehow were managing to plan and execute an ambitious, coordinated research agenda that would enrich the physical sciences of Earth for years to come. Thousands of geologists, oceanographers, meteorologists, and other earth scientists were going to be dispatched around the world on a wide variety of field investigations. Among the major subjects of international research would be the mysterious continent of Antarctica.

As an influential member of the Committee on Polar Research of the National Academy of Sciences, Bader proposed that the United States sponsor a project to drill as deeply as physically possible into the Antarctic ice cap and extract an ice core of the interior of the polar glacier. To the U.S. committee appointed by the National Academy of Sciences to determine the American contributions to the IGY, Bader offered a tantalizing description of its possibilities.

"Two thirds of the area of the Greenland ice sheet and practically all of the Antarctic ice sheet are permanently dry," he noted, and temperatures are almost always subfreezing. All precipitation falls as snow. So every snowfall, including everything that fell with it— volcanic ash, meteorites, spores, and bacteria—is "separately and safely filed for future reference" by being buried under later snowfalls.

"The Greenland and Antarctic snow layers are a treasure trove for the scientist." Bader noted, and added that the treasure was not without military importance. In the ice was a record of the global atmosphere's response to the nuclear age since the first atomic detonations in 1945. Scientists monitoring radioactive fallout could go back several years into the "files" of polar ice in Greenland and Antarctica and measure some things they may have missed.

By analyzing snows back to preindustrial times, Bader also thought it would be possible to track atmospheric contamination by industrial activity.

Bader succeeded in persuading the U.S. National Committee to sponsor a project to extract two deep cores from the Antarctic ice sheet, at Marie Byrd Station in the interior and on the Ross Ice Shelf. Such an ambitious undertaking would require substantial preparation. A scientific and engineering crew would have to be sustained in a very remote and extreme environment for months at a time. Bader proposed a field test project in Greenland, where the U.S. military presence was already established. Roughnecks could experiment with drilling methods and equipment, and scientists could explore different techniques of ice core analysis. From a scientific point of view, the research program outlined by Henri Bader most logically would have fit within the purview of the U.S. Geological Survey, a venerable agency with a long history of earth science research. In the 1950s, however, some other secret logistical and strategic Cold War imperatives were at play. The U.S. committee accepted Bader's proposal that his own Army lab, the Snow, Ice and Permafrost Research Establishment (or SIPRE), would do the job.

In May 1956, 26-year-old Chester C. Langway Jr. of Worcester, Massachusetts, was hired as a civilian researcher at SIPRE's new Wilmette, Illinois, laboratory. Langway, who had served 15 months with the Army in Korea and 38 months with the Air Force in Germany, had a freshly minted master's degree in geology from Boston University. Like most of his geology classmates, Langway had thought he was on his way into the business of exploring for oil and gas when he heard about the job opening at the Army lab, but the geology of ice sounded more interesting. By June he was in Greenland.

Drilling already was under way at Site 2, a location in northwestern Greenland that was chosen for its logistical convenience 220 miles east of Thule Air Base. A nearby Army research facility and radar station added to the convenience of Site 2. In the field of deep-core polar ice sheet drilling, the summer of 1956 was the beginning, and Site 2 was ground zero. Eventually Langway would write the first book describing this new field of

"stratigraphic analysis" of polar ice and devote his career to studying the various physical and chemical characteristics of deep cores. But in the summer of 1956 at Site 2, ice cores from the depths of a polar glacier were such a mystery, he recalled, that "nobody knew what they looked like, even." Putting the case more formally, Langway observed in his official report on the project that, while several exploratory expeditions had returned with valuable information on the upper few meters of old snow, "below the thin surface shell of the ice sheets lies an almost completely unexplored region about which little is directly known."

Success of the enterprise depended on a singular assumption: that the engineers could devise a mechanical drill capable of penetrating 1,000 feet or more into the ice with a hollow bit that would permit the extraction of core that was useful for careful scientific analysis.

However worthy the science, as a practical matter, how realistic was that goal? Researchers were about to discover that under extremes of pressure and temperature, ice, brittle and elastic in turn, behaves like no other substance on the planet. The job called for some creative engineering. As Army geologist G. Robert Lange described earlier efforts, "Results have been generally discouraging, with little or no usable core reported."

Summers in Greenland are cold and windy—miserable conditions for working with heavy equipment. The engineers dug themselves a big trench, 45 feet below the surface of snow, and covered it with a roof that the drilling mast punctuated like a spire. There was no escaping the intense cold, however, or the material contrariness of the ice. Drilling into deep polar ice was like working with a substance from another planet. Under such extremes of temperature and pressure, its physics are out of this world. One instant it turns to slush, the next it shatters like precious china. Boring an open hole would have been difficult enough, but extracting a well-preserved ice core demanded that roughneck drillers exercise the nearly impossible combination of brute power and extreme delicacy. During that first experimental summer in Greenland, even with all of the muscle and know-how of the U.S. Army at hand, and the nation's scientific and technical prestige at stake, there were times when an engineering solution seemed beyond reach.

Conventional drilling systems of the size and power required in Greenland and Antarctica had been designed for the petroleum industry to penetrate deep rock and sediment. The engineers were hoping that modifications to the heavyweight, industrial-strength tubular rotary drill would accommodate the special circumstances of extreme cold and the structural peculiarities of the ice. They were using what was known in the drilling business as a "Failing 1500," a rock drill graded to 1,500 feet depth, its pipe sectioned in 20-foot lengths. Langway would recall the Failing 1500 as "a terrible thing to manipulate" in the cold of northern Greenland. "You had to break pipe at 20 feet going down and coming up."

The drill employed compressed air as a rotating fluid to remove the ice cuttings, a circumstance that required several air compressors and a large heat exchanger to cool the compressed air. The chips of ice that melted from the frictional heat of the drill bit tended to refreeze and fuse together. Bits became stuck. Up and down it went, the entire string of pipe being dismantled with the retrieval of each section of ice. Much of the core was fractured or deformed by the process. Because the overlying burden put the ice under increasing pressure with depth, the deeper they drilled, the quicker the hole wanted to close. There were equipment failures and other unforeseen problems that are typical of elaborate operations in remote locales.

At the end of the summer of 1956, the drill had reached 305 meters—991 feet. Ice core was retrieved from about half that length overall. The deeper they drilled, the worse the ice core deteriorated. In his official report on the first season of effort, Lange accentuated the positive, promising that "although the quality of the core produced left a good deal to be desired, it appeared certain that improvements in quality and amount recovered could be assured by modification of equipment."

Although the drillers had proven that it was at least possible to penetrate a polar ice sheet to 1,000 feet and retrieve the core, these early results must have been privately disappointing to Henri Bader, who dreamed of opening the archive of climate history he believed was stored in the ice sheets. Only a fraction of the ice had been penetrated. While he could assure members of the U.S. National Committee that their commitment to deep-core drilling in Antarctica would be nominally successful, the results were not likely to be spectacular science. As he described the technical details, he told the science officials that a practical limit seemed to have been reached.

The experience of 1956 led to an overstatement of the problem. According to Bader, the Greenland trials had shown that the depth of 300 meters "is very close to the maximum depth for core recovery in any high polar glacier." Experiments by Langway at the SIPRE laboratories showed that at about 230 meters down the pressure from the overlying snow reaches a level whereby the pressure on the embedded bubbles of air gradually exceeds the tensile strength of the ice. Because the original drills used air to blow cuttings out of the ice core hole—suddenly exposing the deep ice to lower pressure—cracking began even before the core reached the surface. While later drillers did encounter a so-called brittle zone of ice susceptible to cracking between 700 and 1,300 meters depth, the use of a viscous liquid in the hole rather than air prevented wholesale fracturing of the core. (Ice from the "brittle zone" is stored for several months at the drill site to allow slow equalization of pressures before those sections of core are processed.)

In Greenland, what Langway's drillers intended as a single field season of drilling trials was extended to a second summer of experimentation. At the end of the 1957 summer season, in a new hole at Site 2, drillers reached 411 meters—1,336 feet. Although some practical limit seemed to have been reached, the drillers had achieved their goal of penetrating deeper than 1,000 feet into the ice sheet. Overall, this first attempt to drill deeply into a polar ice sheet was regarded as a qualified success. To a depth of 110 meters, they had extracted continuous undisturbed ice core, and down to 305 meters, 80 percent of the core was recovered. Below 360 meters, only two 5-meter lengths were usable core. Significantly, the quality of the ice core was much improved over 1956, and Chester Langway had more than enough polar ice core for his purposes.

In the Southern Hemisphere's summer of 1957-1958, American drillers, using techniques developed in Greenland and the same equipment, a modified Failing 1500 rock drill, reached a depth of 308 meters at Byrd Station, Antarctica. During the next austral summer, drillers at Little America V, on the Ross Ice Shelf, Antarctica, extracted core from a depth of 256 meters. While using the same modified conventional oil field drilling system, the engineers at this second Antarctic core-drilling site improved their results by filling the ice hole with a dense fluid to prevent the pressure of the surrounding ice from collapsing the hole.

Difficult as it had been, the IGY deep ice core project was a success. From the Northern and Southern Hemispheres, thousands of feet of polar ice core had been retrieved. Although the study of polar ice had not attracted widespread interest outside the U.S. Army cold regions laboratory, the National Science Foundation was sufficiently impressed with its potential to continue its financial support of polar ice research beyond the IGY.

Bader and Langway wanted to go deeper, of course, to plumb the ice sheets to their very depths. How many tens of thousands of years of Earth's climate history still were hidden far down in the ice? If they were ever going to know, they were going to have to solve some major engineering problems.

And here was a mystery worthy of the name: What if they were able to completely penetrate the ice cap? What would they find? Solid, liquid, or gas? Bader speculated that they would find, at the bed of the glacier, a volume of dry natural gas under tremendous pressure from the great weight of the ice. In that event, he wrote, the drilling crew "must be then ready to seal the hole to prevent development of a gusher." Russian scientist Igor Zotikov speculated that the Antarctic ice cap lay over great pockets of compressed air held down by its enormous weight. According to Zotikov, "The stores of energy of the compressed air which has accumulated during the time of the existence of the icecap is tremendous and could turn the giant turbines of a great electric power station for many thousands of years."

For a time, however, the distance down to bedrock must have seemed as far away as ever. Although the IGY projects had proven the concept of deep-core drilling, to the scientists and the engineers they had also proven that they were not very likely to get anywhere near bedrock in Greenland or Antarctica with a conventional rotary drilling system. Even if it had worked perfectly, transporting the heavy conventional drilling equipment with its 20-foot lengths of steel pipe to remote polar locales was practically impossible and intolerably expensive. If the research was going to survive long beyond the IGY, some innovative engineering solutions were going to have to be created.

In 1957, at the Army lab in Wilmette, Bader asked Lyle Hansen to begin work on a completely new drilling system designed specifically for extracting cores from deep polar ice. Since returning from the Taku Glacier expedition in the summer of 1950, Bader had been thinking about a drill that would take advantage of the physical particularities of ice—a thermal drill. With a souped-up electric transformer, they would try to melt their way through the ice cap. The electrically heated drill would be winched up and down the hole on a cable, doing away with the oil rigs' heavy and cumbersome lengths of continuous steel pipe. The problem of the collapsing borehole would be solved by filling it with a fluid more dense than the ice and with a lower freezing point—a viscous cocktail of Arctic-grade diesel fuel and trichloroethylene, a heavy toxic solvent. A vacuum pump would draw meltwater through heated tubes up into a tank above the core barrel.

In the summer of 1961, Chet Langway and the engineers took their new thermal drilling system back to northern Greenland and set up shop in the relative luxury of a curious experimental installation near Thule Air Force Base. Camp Century, the "City Under the Ice," was a secret Cold War installation that the Army had begun developing in 1959. Out on the ice of northern Greenland, 100 miles from Thule, a large and very elaborate military experiment was under way. With accommodations for some 200 men, enormous snow-covered trenches were laid out with dormitories, shops, theaters, clubs, and other amenities, including a well-equipped hospital and a well-stocked library, all powered by a little nuclear plant embedded in the ice. If the Soviet Union launched nuclear-tipped missiles at the United States, the thinking went, a counterattack could be mounted from this shelter under the ice. For such a critical Cold War mission, no expense was spared. The ice-coring project, expensive and difficult by standards of civilian science, must have seemed inconsequential at the time alongside grandiose military projects.

However, Camp Century was not long for this world. Movement within the ice sheet was deforming the tunnels, a circumstance that became increasingly troublesome and expensive. At one point, a team of about 50 men was devoted exclusively to keeping the tunnels open. More expense and trouble lay ahead. Under the terms of a treaty banning nuclear activity in Greenland and Antarctica, the nuclear plant was going to have to be removed. Although an alternate diesel-powered plant was available, the rapid closure of the tunnels was causing alignment problems in the power system. In 1966, the entire enterprise was abandoned, the little nuclear plant removed, and apparently just about everything else left to the crushing flow of the ice sheet.

About all that survives of Camp Century today is the name it gave to the ice core completed that last summer and the scientific history it made. By the summer of 1964, after trying three fluid-filled holes in the same trench at Camp Century, the crew had reached a maximum depth of 535 meters. The quality of the ice core was fairly good, although the thermal shock created stress in the core that caused additional fractures. By the third summer in northwest Greenland, it was clear to the crew that the thermal drill was not going to be the solution to the deep-core polar ice drilling problem that Bader and the Army engineers had hoped it would be.

A breakthrough came with a new oil well drill invented by Armais Arutunoff, who ran a little pump company in Bartlesville, Oklahoma. Suspended from a power cable, the electric motor and drive system was submersible in fluid. In 1965, the Army engineers took a reconditioned "Electrodrill" to Camp Century, inserted the diamond-cutting bit into the 535-meter hole, and quickly cored to a new record depth of 1,002 meters. During the next Northern Hemisphere field season, on July 4, 1966, the Army crew, using the Electrodrill, reached 1,387 meters—4,509 feet—and hit bedrock.

The new drill was then airlifted from Greenland to Byrd Station, Antarctica, where it reached the bottom of the Antarctic ice sheet at 2,164 meters in January 1968. During the following drilling season, however, when it was lowered back into the hole in an attempt to recover some material below the ice, the only drill capable of penetrating polar ice to bedrock became jammed and irretrievably lost. The United States would go for 20 years without a drill capable of producing a surface-to-bedrock core comparable to those garnered at Camp Century or Byrd Station, a circumstance that could have been a serious blow to the progress of polar ice analysis and the discovery of abrupt climate change were it not for the Danes.

At the University of Copenhagen, a team led by Niels Gundestrup designed and developed a deep-core drill system that finally would conquer the ice sheets of Greenland and Antarctica. Beginning in 1978, the three partners of the Greenland Ice Sheet Program (GISP)—the United States, Denmark, and Switzerland—used the Danish drill in southern Greenland at Dye 3, the U.S. radar station that was part of the Distant Early Warning network arrayed across the Arctic Circle from northwestern Alaska to Iceland. In the summer of 1981, the GISP team reached bedrock at 2,037 meters—6,620 feet—a mile and a quarter from the surface. "The core is of excellent quality," Gundestrup reported, "and no part of the core is known to be missing."

In the 1990s, when the European nations of the Greenland Ice Core Project (GRIP) penetrated the ice sheet from the high-elevation Summit all the way to the bottom at 3,028.8 meters, a distance of nearly two miles, they again turned to the Danish ISTUK drill. Twenty miles away, the U.S. drillers of the Greenland Ice Sheet Program-2 (GISP2) reached bedrock a year later with a new drill developed at the University of Alaska, Fairbanks.

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