Margaret Wertheim |
| Photo by Jaime Ramos for National Science Foundation |
Dave Marchant is fanatical about ice. Especially ancient ice. In the Beacon Valley of Antarctica he believes he has found the oldest ice in the world, glacial substrate laid down 10 million years ago. For the past 18 years, Dr. Marchant, a professor of Earth sciences at Boston University, has been coming to the Antarctic to study its glaciers and to look for signs of climate change during the long course of our planet’s history. Marchant has discovered a location where he believes we can uncover a continuous record stretching back millions of years. Of the Valley’s unusual glacial forms, Marchant would tell me: “As far as understanding climate change, these are the greatest archives on Earth. In my opinion they’d be the bible of climate change.”
I had come to the Antarctic at the invitation of the National Science Foundation to learn about ice, and from the day I landed at its base at McMurdo I had been hearing Marchant’s name. But his tiny encampment is one of the more remote field camps the NSF supports, and the only way to get there is by helicopter. During the austral summer, the NSF maintains a fleet of choppers for ferrying scientists and their equipment to and from the field camps; they would try to fit me into their schedule, I was told, but no guarantees.
Logistics in the Antarctic have been particularly difficult this season. Four years ago, a humongous iceberg known as B15 broke off from the Ross Ice Shelf north of McMurdo and started drifting into McMurdo Sound. Soon after its secession, the initial berg broke up into several pieces, but its largest fragment, B15-A, is still 80 miles long and has a total area of 1,200 square miles, almost the size of Long Island. The presence of this behemoth has interrupted the normal patterns of wind and ocean currents, and because of this disturbance the entire surface of the sound is frozen solid.
B15-A has been making life hell for Antarctica’s humans and also for the region’s penguins. During November, penguins should be nesting, the males sitting on the eggs while the females go to the sea to feed. In normal years there is usually about 10 miles of ice from the coastline where the rookeries are located out to the open water, and the birds can make that trek without much trouble, Dr. Steve Alexander told me. An affable, laconic English biologist, Alexander is the manager of McMurdo’s Crary Science Laboratory, the logistical hub for Antarctic science. This year, however, the penguins must cross nearly 80 miles of ice, “which is too far to make it worth their while,” Alexander said. The birds have been abandoning their rookeries, leaving their eggs and waddling away.
Where the penguins have to walk across the ice, people have to bash their way through it. Each year in late January, McMurdo is restocked with provisions by a supply ship that can reach the base only in the wake of an icebreaker. The usual 10 to 15 miles of coverage is no sweat, Alexander said, but 80 miles of ice up to 16 feet thick is a pretty formidable challenge. When I arrived, the base was abuzz with talk about whether the supply ship would be able to get in. All of which made my trip to Beacon Valley less than a high priority.
The Physiology of Freezing
It is no coincidence that the local term for being in Antarctica is “on the ice” — as in the oft-asked question “How many seasons have you been on the ice?” As a newbie, I signaled my neophyte status in myriad ways, from my ignorance of the argot to my wimpy need to bundle up in four layers of clothing every time I set foot out the door. Even in summer, the average temperature on the Antarctic coast (where McMurdo lies) is around -15°C. In winter it drops to -30°C. Inland, the summer average is around -40°C and the winter average -70°C. The coldest temperature ever recorded on Earth, -89.2°C, was at the Russian Vostok Station. All this is without considering the wind-chill factor, which can easily shave off another 20 to 30 degrees. The day I spent at the South Pole I felt as if my mind had crystallized — the chill penetrated so deep, I could barely breathe, let alone think. And that was in the middle of summer.
The dangers of cold to living flesh were explained to me by McMurdo’s field and safety training officer, Brian Johnson. Before being deployed beyond McMurdo, all personnel must undergo a course in “extreme-cold-weather survival.” After a long disquisition on the physiological effects of hypothermia, Johnson launched into a spirited description of what he called “the frostbite continuum.” After the first phase of redness, skin exposed to extreme cold begins to turn a waxy white, indicating that the cells beneath the surface have frozen solid. This icy state is usually unnoticed by the victim but visibly evident to others. If tissue remains like this for long, the skin will begin to turn blue, then black, as the cells die off through lack of oxygen. It is extremely important, Johnson explained, that in the white phase you get heat to the tissue so blood can begin to flow again, but whatever you do, he said, you mustn’t rub the affected patch, for the vigorous motion will cause the ice crystals to tear the delicate fabric of the cells.
Ice crystals are not only sharp; they also have the unusual property of taking up more space than the water from which they were formed. Water is one of the very rare substances that expands when it freezes — ice is 8 percent less dense than liquid H20, which is the reason why ice floats, and this singular fact has made life on Earth possible. If, like most liquids, water contracted when it froze, the denser, heavier ice would drop to the bottom of the sea, and the world’s oceans would long ago have solidified into an unmeltable mass.
But if ice is physically necessary for Life as a whole, for individual lives it is almost universally lethal. (Anyone cryogenically frozen today would be so badly cell-damaged, if they were ever reanimated it is hard to see how life would be tolerable.) In order to preserve flesh below 0°C, you need to replace the water with a fluid that remains liquid — in effect, antifreeze. Scientists have been trying to invent a suitable substance for years; aside from cryogenicists, surgeons would like to use such a fluid for preserving transplant organs. So far they have met with limited success, yet within the Antarctic seas, aquatic creatures have long ago solved the problem and happily swim in water at a perpetual subzero chill.
On the bottom level of the Crary Lab, communities of sea stars, sea urchins and giant flealike isopods splash about in tanks cooled to a crisp -2°C. Alexander, who began his career in the Antarctic studying benthic (or deep-sea) ecology, explained that these invertebrates resolve the problem of living below freezing by the simple expedient of “maintaining their internal salinity at close to that of the sea itself.” Just as salt is used to de-ice roads in Boston and Manhattan, so it staves off freezing in the polar oceans. Call it the saline solution.
But vertebrates such as fish have evolved over millions of years with a physiology that would not tolerate such increased saltiness. “Antarctic fish have a little more salt in their bodies than you and I, but not a lot more,” Alexander explained. And yet in the Crary Lab tanks, schools of small perchlike fish are happily defying the subzero barrier. “They actually don’t survive if you raise the temperature,” Alexander noted. They belong to the suborder of notothenioidei, a group of Antarctic species that have evolved the ability to manufacture within their bodies a truly bizarre variety of antifreeze. Utterly banal to look at, each fish was quietly performing a miracle.
The man responsible for resolving the notothenioid puzzle is Dr. Arthur (Art) DeVries, one of the legends of Antarctic science. A great gruff bear of a fellow with a rumbling baritone and a distracted air, DeVries is a molecular biologist and physiologist at the University of Illinois, Urbana, who has devoted three decades of his life to the unorthodox biology of polar fish. Yet even he seems amazed by how notothenioids deal with ice. Although the Antarctic seas are liquid, DeVries explained that ice crystals are constantly forming at the bottom and floating up to the surface. Notothenioids breathe in these fragments through their gills and ingest them as they eat. Since their bodies are in thermal equilibrium with the seawater (and hence also at several degrees below zero), these crystals ought to nucleate immediate freezing in the surrounding fish flesh — but that is not occurring.
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The extraordinary nature of this condition was brought home to me by Alexander in a dramatic demonstration. From out of a freezer in the Crary Lab aquarium, Alexander took a beaker of supercooled water — not seawater, but very pure regular water, which can be forcibly chilled to around -4°C without freezing (unlike tap water, which is laced with impurities and would inevitably freeze at this temperature). Into the beaker Alexander dropped a tiny sliver of ice. As I watched, a wave of crystallization spread out from this seed, the imprint of its genesis visible in a shimmering pattern radiating from the center and resembling the delicate architectonic structures in mineral exhibits at science museums. We are so used to seeing ice in its featureless, ice-cube-tray form, I had not realized it could behave this way.
In Alexander’s demonstration, the merest fragment of ice “viralized” the beaker, forcing its contents from a liquid into a solid state. So why don’t the fish freeze when they ingest? The reason turns out to be stranger than anything biologists have dreamed of, nature once again besting man in its protean imaginative potential. DeVries has discovered that the fish produce a protein — called an antifreeze glycoprotein — that envelops the ice crystals and ferries them off to their spleens. By surrounding the ice in a protective shell, the glycoprotein prevents it from viralizing the liquid in the fish’s cells.
“This is entirely different from the way that most antifreezes work,” DeVries explained, his voice revealing the childlike awe that even the most seasoned scientists often feel in the face of nature’s fecund creativity. The liquid that Northeasterners pour into their car radiators, for example, prevents solidification by lowering the freezing point of the water. It’s the same principle as increasing the salinity. With the notothenioids, however, nature has hit upon a completely different strategy. I asked DeVries if this radical methodology wasn’t more akin to an immune response (immune cells also send special proteins to disable viruses), and he seemed to like the analogy.
Alexander had told me that DeVries had dreamed the notothenioid protein would revolutionize ice-cream production. More expensive, creamier ice creams have smaller ice crystals than cheaper, less smooth varieties, and reducing crystal size is apparently a major goal of ice-cream makers the world over. DeVries realized that his fish protein could solve this culinary conundrum, but according to Alexander he also decided it would be hard to persuade consumers to purchase an ice cream made from genetically engineered fish proteins, and the scheme never took off.
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The South Pole
Nowhere are the contingencies of living with ice more apparent than at the South Pole, that mythical singularity around which our world revolves. Geographically, the South Pole is located on a vast plateau atop a bed of ice three miles thick and spreading out for hundreds of miles in all directions. Seventy percent of the world’s fresh water is locked up in the Antarctic ice; if all of it were to melt, global sea level would rise 200 feet.
Flying in on a C-130 Hercules jet fitted with landing skis, it is hard not to be awed by the overwhelming whiteness of the place. With each passing mile, the utter purity of the landscape takes one visibly farther from the dominion of man. As we passed over the Transantarctic mountains, one of the young pilots from the contingent of Air National Guards who are stationed on the continent each austral summer pointed out an enormous, snaking path. White on white, its sinuous curve betrayed itself only by the most delicate variations in tone on the striations at its edge. It was one of the Antarctic interior’s monumental glaciers, some 20 miles wide, the pilot told me. Others in the region are up to 50 miles across. As happens so often here, it is almost impossible to judge scale, and neophytes constantly underestimate both distance and size.
We are used to thinking of ice as a static commodity, but a surprising lesson from the Antarctic is that ice has rhythms and flows of its own. Aside from the glaciers, whose dynamics scientists are only just beginning to understand, the edges of the continent are laced with vast “ice streams” that ebb and flow like tides. The Pole itself eludes our grasp because the plateau on which it resides is slowly moving. Each year on January 1, the skeleton crew wintering over at the NSF’s Amudsen-Scott South Pole Station place a flag in the frozen tundra at the precise geographic point of the Earth’s axis. Over the course of the following year it will be carried some 10 meters away, so that standing on the point today one sees a line of pennants stretching into the distance.
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This true or “geographical Pole” is complemented by the more permanent installation of a “ceremonial Pole,” a point marked by a soccer-ball-size sphere of polished steel surrounded by a semicircle of national flags from the countries that claim a stake in the continent. Ostensibly, the reason for each nation’s presence is the opportunity for scientific research, but as Alexander noted, the imagined mineral wealth beneath the ice is too juicy a potential prize not to have a hand in. Officially, the entire continent is a global commons; unofficially it is carved into chunks known as “dependencies” claimed by nations such as Argentina, Chile, New Zealand, France and the U.K.
The idea of possessing such a tractless immensity may seem ludicrous, but historically the first step toward ownership is habitation, and, in that sense, the U.S. stands alone at the Pole. Since the International Geophysical Year of 1957, the U.S. has maintained a permanent station at the Pole, and, as we ramp up for the 50th anniversary in 2007-2008, the most recent of its three incarnations is being completed.
The new South Pole Station is not merely an upgrade but a necessity, for the previous station, like the one before it, is being inexorably buried in ice. (Rather than melting, snowfall here simply builds up as part of the mass.) The new station too will eventually be engulfed, but not for a considerably longer period than its predecessors, said Dr. Jerry Marty, the NSF engineer who is in charge of its construction. In an innovative feat of engineering, the entire building is supported on columns that will gradually be jacked up over the next 40 to 50 years. “By that time,” Marty said, “who knows what technology we’ll have?” Building under these extreme conditions is the closest humans have come to building on another world, and according to Marty, NASA is keeping a close eye on the station’s progress.
Whatever our leaders’ territorial aspirations, the South Pole is a superb location for doing science, and the station is surrounded by a cluster of major scientific instruments. Under the auspices of the NSF, scientists from all over the world come here to study the atmosphere, the ionosphere and the magnetosphere. They monitor cosmic rays and have placed seismic instruments in the ice able to detect a nuclear detonation anywhere on Earth. Above all, they come here to study the cosmos, for with its pristine skies and its six-month-long night, the South Pole is an astronomer’s paradise. Several large telescopes are located in the region, and a huge new millimeter-wave telescope is currently under construction.
IceCube
Ironically, the most exciting astronomical project at the South Pole directs the gaze of its instruments not to the sky but down through the frozen plateau. Known as “IceCube,” it will be the world’s first neutrino telescope and the largest-ever scientific instrument. Instead of recording electromagnetic waves, IceCube will record tiny subatomic particles that are emitted by violent cosmological phenomena such as black holes, quasars and colliding galaxies. All of its 4,200 electronic sensors will be buried within the ice, which will itself act as a particle detector. Because the ice here is so pure, neutrinos can be detected by the tiny flashes of blue light known as Cherenkov radiation that are emitted during collisions with other particles.
During my day at the Pole, I was given a tour of the IceCube site by Dr. Darryn Schneider, a wry and windblown Australian astronomer with a knack for large data systems who is in charge of coordinating the signals from all 4,200 sensors within the computational framework. “There is no way this would be possible without computers,” Schneider told me. The entire apparatus, which consists of more than a million pounds of equipment, is a multinational effort involving hundreds of scientists and engineers spearheaded by the University of Wisconsin, where Schneider is based.
While handling the IceCube data is a difficult task, it pales beside the challenge of setting the sensors into the ice. As Schneider explained, the 4,200 individual instruments will be deployed in groups of 60, strung along a cable. In all there will be 70 sensor “strings,” with each string deployed into a separate hole 2.4 kilometers deep. The sensors themselves — each a package of exquisitely sensitive electronics encased inside a glass sphere — will be arrayed at depths between 1.4 and 2.4 kilometers, over a field of 1 square kilometer. (IceCube takes its name from the fact that the total detector array will occupy a volume of approximately one cubic kilometer.)
All this is fine in principle; in practice, no one has ever dug so many holes so deep into ice. Add to this the Antarctic Treaty’s injunction against polluting, and IceCube’s engineers cannot use any kind of traditional drilling equipment (which is typically powered by gasoline that seeps into the surrounding ground). The only way to drill these holes without polluting the ice, Schneider said, is to use hot water, and a good deal of IceCube’s $272 million budget has been spent on designing and building the hot-water drilling equipment.
The vast bulk of that machinery had arrived a few weeks before I did and had only just been installed several hundred meters from the new station. Much of it is housed in two long rows of bright-orange shipping containers, inside of which is the equipment to heat the water. Schneider opened the door of one container to show me what it all looked like. “Basically, they are modified car-wash units,” he said. Heating the water is one problem, getting it is another. The South Pole has ice galore but no liquid water. As with the station itself, water is obtained by melting ice inside what is known as a “Rod well.” Schneider took me over to a tall piece of pipe sticking out of the ice like a spout. About 30 feet below us, he said, hot water had been used to create a cavity or bubble, in turn generating more liquid, which was pumped back up to the surface. All of the IceCube holes would be “dug” with water pumped out of this Rod well, then heated to a scalding temperature by the car-wash boilers.
The trick, said Schneider, is that “The entire hole must be dug in a single hit.” The drill head is on the tip of a cable two and a half kilometers long, and once it has been sunk, the drill would be lost if the water were to freeze around it. This season the team tested the system successfully with a single hole, and, assuming things go according to plan, they will drill the rest over the next five years. One measure of the scale of this massive engineering project is the sheer amount of energy required to make each hole. Some 7,000 gallons of gasoline will be burned by the generators in heating the water for every individual hole. Or, as Jerry Marty put it, that’s nearly three C-130 cargo loads of petrol apiece! One of the more curious aspects of the Antarctic enterprise to date is that while it is verboten to leak hydrocarbons into the ice, there are no limits on the amount you can pump into the air.
Once the new instrument is up and running, Schneider and his colleagues will be able to measure precisely where cosmic neutrinos are coming from. Theories predict that they are emitted by supernovae and by the black holes believed to reside at the hearts of most galaxies?. IceCube should be able to confirm or deny these theories, and will help astronomers to search for the mysterious dark matter that permeates much of our universe.
The Oldest Ice on Earth
I had seen plateaus of ice and rivers of ice and fish that defied ice, and finally, two days before I was due to leave “the ice,” word came in that the following day I would be able to visit Dave Marchant and the world’s oldest ice. At the South Pole, I thought I had seen the most spectacular landscape Antarctica had to offer, but NSF representative Peter West had warned me that nothing compared to the raw beauty of Beacon Valley.
Taking off around midday from the McMurdo helo-port, the first 40 minutes took us cruising over the frozen tundra of the Sound. Below us, the ice was a vast Abstract Expressionist canvas, an endless vista of multihued and infinitely variegated white. Paul Murphy, our young English pilot, explained that early in the season the ice is clean with no tonal shades, but as the summer progresses dust blowing over from the McMurdo Dry Valleys paints a subtle pattern the pilots call sustrugi. Reaching the far side of the sound, we headed along the Farrar Glacier, its boundary with the sea marked by patches of brilliant blue “re-freeze” that is the hallmark of pure glacial ice.
We were heading inland, deep into the heart of a region first explored by Robert Scott and the great Antarctic explorers of the early 20th century. Suddenly Murphy banked left and we turned into a barren valley, the ground beneath us bare as the moon. On either side loomed towering cliffs, striped with huge bands of black and brown rock, each recording a different geological era. Just as we entered, it began to snow, which may sound like a mundane event, but is actually not so common. The Dry Valleys are so called for their extremely low precipitation rates — the region being, in Marchant’s words, a “hyperarid desert.” (For my previous article on the Dry Valleys, see www.laweekly.com/ink/05/11/features-wertheim.php.) Through the swirl of the snow, the midday sun was suffused into an unearthly radiance, and the striations of the cliffs seemed to glow from within.
Marchant’s encampment turned out to consist of just a tent and a grad student? — several other team members had already decamped. Oddly, apart from the snow, there was little ice to be seen, and the ground around us was covered in rubble. Marchant was clearly a man accustomed to the cold; his cheeks showed patches of recent frostbite damage, and his eyes had a glittering look that I was later told was likely due to a bout of snowblindness. From the moment we arrived, he bubbled forth about his beloved ice, which turned out to be a great deal closer than I’d imagined. Actually, he said, I was standing on it; the rubble was merely surface debris covering an ancient glacier that was spilling down in toffeelike waves from the top of the mountains behind us. The ice itself was less than a meter beneath my feet.
Inside the tent, Marchant pulled out an aerial photograph and started to describe the valley’s terrain. “Here,” he said, pointing to a spot near the top of the mountain, “we know this ice is 300,000 years old. And here,” pointing to a spot farther down the slope, “we know that’s 1.5 million years. And here, farther down, it’s 4 million.” All this was uncontroversial, Marchant said. But then he pointed to a place on the Valley floor not far from where the tent was pitched: “Here,” he said, “we believe this ice is 10 million years old.”
Marchant admits that his claim is controversial, and another glaciologist I spoke with back in the States disputed his evidence. But Marchant also has his supporters, and if he is right, he’ll have found a place with a record of the Earth’s climate dating “back into the Pliocene and even into the late Miocene era,” for trapped within glacial ice are tiny air bubbles containing pristine samples of the atmosphere from each era in which ice was laid down.
Initially, even Marchant was skeptical about his most ancient finds: “At first we thought this ice couldn’t be 10 million years old,” he told me, “but all the data we’ve generated over the past decade has been telling us it is.” Marchant wanted to take me on a walk to see some of his evidence, but the snowstorm was intensifying, and Murphy suddenly determined that unless we intended to stay the night we would have to leave immediately. Marchant directed Murphy to fly over the polygonal formations he had wanted me to see, forms that he said can occur only when ice has sublimated (or evaporated) from below the surface. “You see the same formations on Mars,” he said, evidence, he thinks, that there is also ice just beneath that alien ground.
As Murphy swooped the helicopter low over the fractured forms on our way out of the valley, Marchant’s voice crackled cheerily over the radio, inviting us to change our minds and stay out the storm. There are plenty of sleeping bags, he enthused, and, hey, “It’s chili night!”
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