Making the Unseen Seen
Drilling ice cores in the frozen Antarctic, as described by geochemist and paleoclimatologist Bess Koffman.
Have you been to Antarctica? If you’ve been to the coast, where most visitors go, you’ll undoubtedly picture majestic peaks glinting in the sun, glaciers fracturing in slow-motion down to the midnight-blue sea. You’ll see white-capped waves lapping at Seussian icebergs, natural sculptures for those lucky enough to catch a glimpse of them before they disappear. You may think of penguins: tuxedoed Adélies with white rings around their eyes, leaping out of the surf or sliding along the snow on their bellies, pink-stained from krill-laced guano. Or maybe your mind’s eye sees a cluster of stately Emperors, with their golden feathers and imperial bills. They stand as a welcoming committee on the Ross Ice Shelf when you arrive at Pegasus Field en route to McMurdo Station. These are undeniably emblematic visions of Antarctica.
Though I am fond of penguins, and love to feast my eyes on extinct Mount Discovery or smoking Mount Erebus, these images are not what I see when I think of the Antarctic “deep field.” Let me take you to the part of Antarctica that I know. If you’ve been there too, you’ll nod and smile knowingly. For only those who have experienced the deep field during austral summer—the flat, endless plains of snow on the plateau—will know what I mean by flat light. It’s what pilots call “flying in a bowl of milk.” Seeing without seeing. The whole world loses contrast, and you are lost between snow and sky.
But let me step back for a moment. What brought me to Antarctica? The first time I visited the icy continent, I was working as a research technician at the Palmer Station Long-Term Ecological Research (LTER) site. My first real job out of college had me venturing out twice a week into the Southern Ocean by Zodiac inflatable boat to collect water samples. I conducted experiments on microbes to learn about the role they play in the ocean’s carbon cycle. Though invisible to the naked eye, bacteria and other single-celled organisms are central to many ocean processes. Given Palmer Station’s location on Anvers Island, I reveled in the majestic peaks, sky-blue glaciers, surreal sculpted icebergs, and clamoring penguins. I loved every minute of it. Well, almost.
The Southern Ocean gets its stormy reputation from the westerly winds that encircle Antarctica, blowing endlessly in a ring around the southernmost continent.
Although I stayed relatively close to shore on my sampling missions, the relentless winds rarely failed to raise a swell. Ocean swells have a particular effect on my stomach. More than the rolling, pitching, or yawing motions one can experience at sea, it is the heaving motion—the slow up, down, up, down—that signals to my inner ear that all is not right with the world. In fact, all I could do was send the brass “messenger” down the cable to close my sample bottles before I sacrificed my breakfast to the hungry ocean. Must not contaminate the samples with my extra carbon. Hold it together. By the end of the field season in late January, I determined that my future in climate research would be based firmly on land.
Fast-forward three years and I once again find myself in Antarctica. This time I am a graduate student, enrolled in a Ph.D. program at the University of Maine. I am in Antarctica to help collect a deep ice core—thousands of meters long—to reconstruct past climate history. It turns out that ice cores, extracted from glaciers and ice sheets on terra firma, are easy on the stomach.
Travel to the deep field takes one through McMurdo Station, the US Antarctic Program’s major hub and the largest research station on the continent. Once again I am enthralled by 14,000-foot peaks, gregarious penguins, and shimmering, icy seas. The occasional seal humps its way past the industrial buildingscape of McMurdo, sometimes described as “a liberal arts college in a gravel pit.” In the frenetic summer season of October through February, it’s a city that never sleeps. The two weeks we spend here are dedicated to safety trainings and science logistics while we await a weather window to fly by LC-130 Hercules aircraft to the middle of West Antarctica. We learn skills like how to survive a night of exposure by digging a snow trench. One popular activity involves simulating a search for a lost comrade in whiteout blizzard conditions—by wearing buckets over our heads.
Though we spend most of our time with logistics, McMurdo also allows us room to reflect on the “heroic age” of Antarctic exploration. I scramble up Observation Hill, a lava dome used by early explorers to get a clear view to the South, their vaunted destination. I sign up for a guided tour of Robert Falcon Scott’s Discovery Hut, built in 1902. Only a short walk from McMurdo, this hut served as a storehouse and refuge for the British Antarctic expeditions led by Scott and by Ernest Shackleton, including the latter’s ill-fated Ross Sea Party. Old woolen coats and mitts remain on display, while cans of food add color to the shelves. Morton’s Kippered Herring. Huntley and Palmer’s Superior Reading Biscuits. Special Dog Biscuits Supplied By Spratts Patent Limited Navy Army and Expedition Biscuit Manufacturer, London. Fry’s Pure Concentrated Cocoa, Makers to His Majesty the King. A burlap bag of frozen, withered onions gapes open to the drifting snow.
But this exploration is not to last: we are in McMurdo for science, and science must continue. Just as we begin to tire of the endless hubbub, the drab sheet-metal buildings, and the impersonal dining hall (though not the Frosty Boy soft-serve machine), it’s time for off-deck. In other words, we are flying to WAIS Divide. WAIS stands for the West Antarctic Ice Sheet, the smaller of Antarctica’s two longitudinal halves. The site was chosen because, like a watershed divide, glacial ice flows away in both directions. This means that while the ice layers at deeper depths are getting thinner and thinner over time, they exist in more or less the same place where the snow originally accumulated. For an ice core climate study, this constraint is important. It means that scientists can make apples-to-apples comparisons about the data collected from different layers of the ice sheet.
The WAIS Divide project is a large collaborative effort undertaken by the United States ice core community, with more than 20 academic and government institutions involved in recovering and analyzing the new core. As a graduate student, I am part of the core processing team. We are responsible for measuring and logging the core, then cutting it into one-meter lengths and packing it in insulated shipping containers for transport back to the United States. We carefully log each meter of the 3,405 meters drilled (11,171 feet, about the length of 30 American football fields). This entails measuring the top and bottom of each core, identifying any visible features, and labeling the ice with an orientation line and “up” arrows. It is critical that we always know which end of the ice is “up,” as this allows us to develop a continuous climate history from the ice core. We use a laser to measure depths precisely, and shine a bright light through the ice to look for features not obvious to the eye. Sometimes we find hairline fractures or cloudy bands that might signal past dust storms or volcanic eruptions. Over the course of six Antarctic field seasons, we drill and log over two miles of ice. I am lucky to participate in two of these seasons.
Of course, we can’t drill two miles of ice all at once. It’s an iterative process: the drill travels down the borehole by means of a giant winch. When it reaches fresh ice at the bottom of the hole, the drillers engage the cutters and start to drill a new core. We typically recover about three meters at a time. Then the “core dogs” break the core, and the drill travels back up the hole, the winch making its wraps slowly, precisely, one at a time. When the 15-meter (49-foot) steel drill comes back out of the borehole, it rotates from vertical to horizontal. Then the drillers manually disconnect the core barrel from the rest of the drill and lift it using a gantry crane. They then push the ice out of the barrel into a tray on a carefully leveled table. As it passes out of the barrel, the core slides through the FED, or fluid extraction device: a 3D vacuum that sucks drilling fluid off the surface of the ice. Fluid with a density equivalent to ice is used to keep the borehole from collapsing during the six-year drilling campaign.
All this work is done by dedicated engineers, specialists who spend their careers designing and building coring technologies. A few Antarctic veterans—scientists and others with specialized skills—also join the team. But once the core has been pushed out onto the table, it leaves the engineers’ realm and enters the domain of the core handlers.
We core handlers—a team of current (and future) graduate students and a few postdoctoral scientists—work on the “cold side” of the Arch. The cold side is kept at -30°C (-22°F), about 20°C colder than the ambient temperature, to reduce thermal stress on the ice. The ice is cold because it’s coming from deep within the ice sheet. We need to keep it cold so that it doesn’t crack and break. Fractures in the ice make it harder to melt and analyze, and also compromise sample cleanliness. What this means in practical terms is that we have three or four freezer units blowing frigid air on the cold side at all hours. Frost accumulates on surfaces and falls down as snow. To combat the cold, we wear insulated overalls, “bunny boots,” and red down-filled parkas fondly referred to as “Big Red.” Since we are wearing nearly identical outer layers, we learn to identify one another by our unique hats, many of them hand-knit. Mine is gray with a yellow snowflake pattern, knit densely of fine wool by my mother, with a double-thick band over the ears and fleece-lined flaps which tie under my chin. It’s like a Roman helmet made of wool. We have other tactics for keeping warm. In addition to the four squares a day served by the camp cooks, we snack frequently on high-calorie treats. We do jumping jacks to increase blood flow to the extremities. When all else fails, we head to the warming hut, where we change into spare gloves left warming by a heater.
A second consequence of the freezer fans, beyond the cold, is the sound they make. It’s noisy in the Arch. In fact, verbal communication is challenging. We get tired of shouting over the fans as we use lasers to measure the length of each core in its tray. My core handling partner Gifford and I devise a system of sign language. One person slides the laser down its track while the other logs information into the computer and a backup paper logbook. The laser beam shines across the core and provides accurate and precise measurements. Giff aligns the laser with the top of the core and pats his head. I click the button for “core top.” Giff slaps his rear; I click “core bottom.” He notices a small chip at the base of the core and taps his shoulder (chip on the shoulder, get it?). This core also has “dog marks,” scratches where the core dogs have gouged the ice. Giff lifts his hand and pinches his middle and ring fingers to his thumb as if making a doggie shadow puppet. I tap the computer accordingly.
Core handlers work in teams of two, with three shifts per day. Giff and I have the day shift this year, though next year I am put on night shift. Each shift has its perks. On day shift (shift one), we get to see more of our campmates: those not directly involved in the ice coring effort, who generally follow a typical workday schedule. This helps build a broader sense of community. Next year, I find the perk of night shift (shift three) to be the close sense of camaraderie that develops among us workers. With two drillers, two core handlers, our night cook, and a few random night owls, the night shift is the smallest group. It always feels a bit weird to be coming off work as everyone else rubs sleep from their eyes, though. And I never get used to eating pancakes for dinner. But this year, our schedule ebbs and flows with that of the majority of camp staff, and we make friends easily.
Camp takes a 24-hour rest period each week, which equates to one shift off. This pause gives us valuable time to catch up on sleep, do laundry, shower, and relax with campmates. I enjoy playing cribbage and Scrabble, and also making music with my co-workers. One of the drillers works part-time as a barista back home. On Sunday mornings he puts on his Starbucks apron and serves specialty coffee, teaching us the nuances of roast and grind. Off-hours are also devoted to exercise. I buy my first pair of skate-skis and learn how to skate on the “skiway,” which is groomed for planes equipped with skis. Despite its broad, flat expanse, I find many ways to succumb to gravity. Through time, I gain balance and coordination. Over 10 years later, skate-skiing remains a near-daily part of my life in winter.
The WAIS Divide camp is quite an operation. There are about 40 people in camp: mechanics, heavy-equipment operators, cooks, managers, drillers, scientists, a weather observer, and a medic. Cargo comes in regularly, some of it for us, some for other deep-field research that launches from our camp. A team of glaciologists flies in and drives off toward the coast in tracked vehicles. They are studying the stability of this ice sheet that we temporarily call home. The WAIS contains a massive amount of ice. Imagine a region with the combined area of California, Oregon, Washington, Idaho, Utah, Nevada, Arizona, and New Mexico covered with ice two miles thick. Although the smaller “half” of Antarctica, it gets the most attention, and for good reason. Unlike most of its sibling to the east, the WAIS sits on bedrock that is below sea level and slopes downward as you go inland. This makes it inherently unstable, as ice likes to float. As the relatively warm ocean water laps at the edge of the ice sheet, little by little the ice erodes. There are also signs that ice loss is speeding up. People are worried about the WAIS because it contains about 5 m (16 feet) of sea-level equivalent, enough to drown many coastal cities. Here at the WAIS Divide field camp, the ice at the bed is 1700 m (5600 feet) below sea level. When we drill past this depth, we celebrate with a beach party. My friend Dave, a driller, brings inflatable palm trees and grass skirts from home. Given the intense pace of our short field season, we appreciate a chance to relax and to celebrate our accomplishments.
Aside from these punctuating events, though, camp life remains focused on keeping the drill going. The drillers send down the drill, cut three meters of ice, bring it back up. Empty the barrel, clean out the chips, send the drill back down. We measure, log, record, cut the core into one-meter lengths using a chop saw, and package it up for shipping. As we fill insulated shipping containers with ice, we palletize them. Eventually four wooden pallets—like the ones you might see when a supermarket restocks its shelves—will go together onto a larger Air Force pallet, where the core boxes are draped in a custom-made insulated blanket for their trip back to McMurdo, and eventually the United States. As we get deeper and deeper into the ice sheet, the drill’s round-trip travel time becomes increasingly longer. This eases the burden on the core handlers just a bit. Things aren’t quite as hectic in our noisy freezer. But we continue to log and measure, sliding the laser on its track and tapping our heads and rears as the situation demands.
Time is a funny thing in the land of 24-hour sunlight. Although Giff and I work the “day shift,” our schedule is aligned not with the sun’s movement through the sky but with the clocks in McMurdo, which are set to those in Christchurch, New Zealand (our travel hub between the United States and Antarctica). Because Christchurch is roughly 75° of longitude away from us, the sun is actually rather low on the southern horizon when we awake, and the air is cold. I dress in my sleeping bag inside my 7 by 7 foot Arctic Oven tent, then tromp out into the snow. First I dump out my pee bottles (two dedicated, liter-sized Nalgenes) at the established pee flag, appreciating the aesthetics of large hoar crystals that form from the warm moisture. The liquid flows down a little moulin and disappears into the snow.
The snow underfoot is unlike any I’ve experienced elsewhere. It’s dense, made of small grains packed by wind. It squeaks underfoot as if I were walking on Styrofoam. The colder it is, the more it squeaks. Today, winds are calm, and the flags that mark the route from Tent City to the galley tent—erected in case of poor visibility—are limp. The sun hangs about 20° above the horizon, following its slow spiraling path around the sky. Here, above the Antarctic Circle, the world experiences one long day and one long night each year. I squeakily trudge to the galley and meet up with Giff for breakfast.
Another “day,” another eight-plus hours of logging core. We head to the warming hut to pull on our Carhartt overalls, Big Red parkas, and warm hats, then enter the Arch, greeting the night-shift drillers and core handlers as we relieve them of their duties. Giff and I fall into an easy rhythm: sliding the laser along its track, entering data, jumping jacks to warm up, lunch in the galley, cutting and packing core, loading boxes onto wooden pallets, logging more core, swinging our arms to send blood into our fingers. This is the unglamorous part of fieldwork in Antarctica.
Giff and I end our shift and emerge from the Drilling Arch to find that flat light has descended on WAIS Divide. Clouds have blown in. The light is now diffuse, the world gray. Snow melts into sky. Though we can see the tents, flags, and cargo lines that define the camp, we feel disoriented. As we walk the quarter-mile from the Arch back to the galley for dinner, Giff and I trip over small snowdrifts, our eyes unable to distinguish hill from valley. We could fall into a hole without ever seeing it.
I realize that this whole endeavor, our six-year field campaign to recover over two miles of ice, is like stumbling along in flat light. Each implacable meter of translucent gray ice is a step into the unknown. Though we log the occasional cloudy layer or black band of volcanic ash, the ice is essentially featureless. Unlike with trees and their growth rings, nothing tells us where one year ends and another begins. We cannot yet see the incredibly detailed climate history contained within the ice. The hills and valleys that define what will become the gold standard of Antarctic ice core records are still invisible. Not until the cores are sliced into many pieces, distributed among the diverse labs that will analyze them, and then melted and analyzed in excruciating detail by a small army of graduate students and technicians will the flat light fade away and the contrasts emerge. It will take many more years of work before the core reveals its secrets. Only then will we be able to make the unseen seen. The fieldwork is only the first step.