“This continent is the highest, driest, coldest, windiest, and emptiest place on Earth.”— US Antarctic Program Participant Guide, 2014–16.
High in the Transantarctic Mountains, the McMurdo Dry Valleys are the largest part of Antarctica not covered with ice. Instead, a seemingly endless carpet of boulders and rocks flows into networks of steep cliffs and valleys—some over a mile deep, recalling the canyons of the American Southwest, but unimaginably more vast. Almost nothing lives there. There are no people around for hundreds of miles. This is Earth’s most ancient landscape, frozen in time for millions of years.
For more than a quarter-century, David Marchant, a Boston University professor of earth and environment and head of the BU Antarctic Research Group, has been exploring the Transantarctic Mountains, methodically piecing together the story of the landscape and past climate change and what it has to tell us about the future of our warming planet. As a graduate student in geology years ago, Marchant would spend up to 100 days at a stretch in the Dry Valleys, living in an unheated tent during what passes for summer in Antarctica, learning to read the landscape by walking and asking himself questions: How did that boulder get there? What about the sandstone? What do those cracks in the rocks mean—what caused them?
Since then, Marchant has led research expeditions into the Transantarctic Mountains nearly every year. With funding from the National Science Foundation (NSF), he has made major discoveries that have upended longstanding scientific views about the age, environment, and climate of the region. Seeing things that earlier geologists had missed, he is widely regarded as a pioneering leader in the field of Antarctic geomorphology, a science that strives to add the “why” to “how” a landscape looks. As passionate about teaching as he is about research, Marchant is now training the next generation of geomorphologists, imparting to his students his knowledge of how to understand the origin and evolution of this landscape.
From early November through December 2014, Marchant led a team of graduate students on his 26th trip to the Dry Valleys, where they spent eight weeks living in unheated tents under 24-hour sunlight, doing fieldwork long into the night. For Marchant and his students, each trip begins with a series of questions: Exactly how old are the Dry Valleys? Why did ice first form there? When did the climate cool so dramatically that even the hardiest tundra plants and animals became extinct? What can ancient, buried ice tell us about the future of our warming planet, and the potential threat of sea level rise?
What happened to this massive ice sheet in the past?
During his early years as a geologist, says Marchant, the idea that marine-based ice sheets could collapse with modest warming was just starting to be discussed seriously at academic meetings. Antarctic glacial geology was considered, at that time, somewhat esoteric. Today, however, with accurate satellite measurements showing real-time ice loss in the West Antarctic ice sheet, Antarctica is regarded as a central area of modern scientific research. The Dry Valleys are situated along the East Antarctic ice sheet, which contains almost 70 percent of all fresh water on Earth, and which has so far remained relatively stable—a good thing for all of us, because if it were to melt, global sea levels would rise 200 feet, putting all of Boston and many other coastal cities underwater. The key question, especially for a geologist like Marchant, is this: What happened to this massive ice sheet in the past? Did some of it melt during natural climate warmings that occurred several million years ago (during, for example, the Pliocene Epoch, when global atmospheric temperatures were on average about 3°C warmer than today?). If it did, does that suggest that it might melt in the future with atmospheric warming created by the burning of fossil fuels?
For Marchant and his team, the answers are in the landscape and the ice that lies beneath.
Unraveling the mysteries of the Antarctic Dry Valleys starts here at BU, in the Digital Image Analysis Lab, where Marchant and his students pace in front of 12-foot-tall high-definition video screens, poring over thousands of satellite images and aerial photographs of the Transantarctic Mountains. They are looking for field sites for the next expedition. Specifically, they are searching for polygons, networks of cracks in the landscape caused by thermal contraction and expansion. Similar patterns can be seen in landscapes all over the world, but Marchant and his team are looking for “sublimation polygons”—a term Marchant coined—which are indicative of shallow, buried ice, hidden beneath just one or two meters of debris. It’s this ice that Marchant believes may hold the key to the history—and future—of the East Antarctic ice sheet.
When Marchant first began working in Antarctica, the Dry Valleys were considered ill-suited for glacial studies, specifically because of the preponderance of polygons. The general wisdom at the time was that when polygons form, the layering of near-surface sediments is disturbed by the movement of ice and soil through recurring freeze and thaw cycles—a process known as cryoturbation—which would preclude the existence of any data about the ancient environment. Polygons aside, many of Marchant’s colleagues encouraged him to abandon his investigation of the Dry Valleys, calling it “folly,” and arguing that the region lacked any of the standard evidence for typical glaciation. If he were to find ice at all, they said, it wouldn’t have anything to tell him about the evolution of the Antarctic environment. At the time, few geologist other than Marchant and two of his colleagues, George Denton from the University of Maine and David Sugden from the University of Edinburgh, believed that the upland regions of the Dry Valleys might have preserved a pristine, multi-million-year record of climate change and landscape evolution.
Ultimately, Marchant was able to use the dating of volcanic ash and numerical modeling to show that air temperatures in the Dry Valleys have remained too cold for the past several million years to allow any melting or cryoturbation. He developed a new model for the formation of these sublimation polygons, arguing that they would likely form where stagnant, buried glaciers were covered with one or two meters of surface debris. In 1993, Marchant’s belief was confirmed, when he and Noel Potter, a colleague from Dickinson College, discovered glacier ice buried beneath a vast field of polygons—the very sublimation polygons that Marchant had begun to decode. Since then, Marchant’s expeditions have begun with a rigorous examination of the landscape’s polygons, in the hopes of finding the ideal place to drill for ancient ice.
Checklist for an Antarctic expedition:
1. The Grant
Antarctic research is supported by the National Science Foundation’s Division of Polar Programs through competitive grants. In May, about 18 months before a proposed expedition, Marchant must submit a thoroughly documented research grant proposal to the NSF. Only a small percentage of all NSF grant proposals are funded. The NSF requires at least six months to deliberate over a proposal. It solicits multiple opinions from scientists around the world, enlists yet more reviews by scientists convened on special panels at NSF headquarters in Arlington, Virginia, and requires an assessment by NSF program managers and staff. Grant notifications are usually sent out anywhere from late December to mid-January.
2. Advance Planning
Assuming the grant proposal is approved, Marchant’s team starts planning in February, at least nine months before departure, refining field objectives, which may have changed according to recent research results and data collected during the last trip.
3. The Paperwork
By April, they submit to the NSF’s US Antarctic Program a 60- to 80-page document listing everything from the combined weight of everyone on Marchant’s team—crucial data for Antarctic helicopter flights—to how many rolls of duct tape they will need once they get there.
4. Virtual Fieldwork
In the Digital Image Analysis Lab, Marchant and his students study satellite imagery and aerial photographs of the McMurdo Dry Valleys. This is a crucial step in identifying which polygons they will investigate from their base camp in the Transantarctic Mountains.
5. Battery of rigorous physical exams
All candidates for the trip must be in good health to make the journey south. Though medical attention might only be an hour away, via helicopter, frequent storms that last for days could turn a routine medical issue into a potentially life-threatening crisis.
6. Getting the equipment to Antarctica
The packing list might include drilling supplies to core through rocks and ice; ground-penetrating radar (GPR), with multiple antennas for analysis of buried ice; meteorological sensors for recording air temperatures, relative humidity, solar radiation, wind speed, and soil moisture; computers to download terabytes of data; video supplies and infrared cameras to help link landscape change with local microclimate conditions. All of the gear is taken to FedEx for shipping to California. From there, it goes by boat and cargo plane to McMurdo Station, a major US research facility and the largest outpost in Antarctica.
Forty hours of commercial plane travel: The team’s usual flying route is from Boston to Los Angeles to Sydney, Australia, to Christchurch, New Zealand, the jumping-off point for Antarctica.
Two days in Christchurch: At the Clothing Distribution Center, each member of Marchant’s team is provided with two duffle bags of cold weather gear sized for them: multiple coats (including the infamous “Big Red” parka, which Marchant deems too big and bulky to walk in, let alone to wear while doing fieldwork), gloves, mittens, hats, several fleece pullovers and sweaters, long underwear, extra layers of polypropylene, socks, and “Bunny Boots” (military boots that keep warm air in—as well as moisture, which means perpetually sweaty socks).
Eight hours via military aircraft: The trip by LC-130 Hercules transport plane to McMurdo Station. They land on the floating Ross Ice Shelf. Special trucks and track vehicles take them to McMurdo.
Seven to ten days at McMurdo: They collect the equipment shipped months earlier, along with propane stoves, a small generator for charging equipment, tents, and other gear. They pack wooden crates with several weeks’ worth of food: instant oatmeal, pasta, frozen vegetables, the makings of chili, cheese, granola bars, chocolate, a lot of peanut butter, and “cabin bread” (New Zealand crackers that substitute for regular bread, which would fall apart in the field). Every two weeks or so, they will call for a helicopter to take them to a different field site and to bring additional wooden boxes of food. They will pack any field samples they have collected in the empty wooden boxes for transport back to McMurdo.
Fifty minutes: Helicopter flight to first campsite in the McMurdo Dry Valleys. The makeshift landing strip is whatever space the pilot can find between the rocks and boulders. They get off with their equipment. The helicopter disappears. Silence descends. They are there.
Average temperature here is -10°F. During the Antarctic summer—fall back in Boston—temperatures might reach into the twenties, but ferocious winds can make even that feel like well below zero. And yet Marchant’s team sleeps in unheated tents.
“There are two ways to approach fieldwork out here,” says Sean Mackay (GRS’15), a doctoral candidate in geomorphology who has made several trips to the Dry Valleys with Marchant. “One is ‘me versus the environment’—you’re wearing the thickest, warmest clothing you could possibly get. You figure out how to heat the tent, you have as good food as you possibly can. You get your information, you go back to your warm place as quickly as you can. You see it as ‘the other.’ You’re separated from it. You can’t really get things right.”
MARCHANT’S PHILOSOPHY:“You don’t heat the tent because then you never want to leave it.”
“The other way,” Mackay says, “which I learned from Dave, is you basically immerse yourself, you let the outside in. Dave’s approach has always been that you go out there and live in the landscape for two or three months at a time. He said to me, ‘The way I find things is with my feet.’ The more footsteps on the ground the more you see. You don’t heat the tent because then you never want to leave it.”
The tents are called Scott tents, after the early explorer, Robert Falcon Scott, who discovered the Dry Valleys in 1903 (“We have seen no living thing,” he wrote). Shaped like tepees, they are made of heavy canvas, held up by four steel poles, and tied by heavy rope to rocks to keep them from blowing away. Marchant has been inside one of these tents in gusts of 100 MPH. The tent held. Still, even the most seasoned mountaineers wonder how the tents will perform, especially during blizzards that can last for days, and even weeks, on end.
The only way to get water in the upland Dry Valleys is to melt snow or glacial ice on the propane stove. They won’t take showers for six weeks or longer, not until they get back to McMurdo Station.
Breakfast is instant coffee and oatmeal or cold cereal. Because they are too busy to stop working for lunch, they stash granola bars and chocolate bars in their pockets before heading out. They eat a lot of one-pot chili dinners, and pasta with frozen vegetables. In a setting like this, Marchant says, food is fuel. This is a research expedition in a hostile environment, he says, not adventure travel. He wants any extra space on the helicopters or in the field reserved for scientific equipment.
Some research teams do bring in more creature comforts, like giant generators to power microwaves and coffeemakers, and to heat the tents. But Marchant says trying to make Antarctica as comfortable as possible defeats the purpose of going to Antarctica. “I don’t want any distractions,” he says. “I want the students to be constantly thinking about their environment, not about when they can return to a heated camp with microwaveable food. Such distractions limit science. We go with minimal gear—just enough to make it somewhat comfortable—and devote all our time and energy to data collection and interpretation.”
Without distractions and with the 24 hours of sunlight that comes with the austral summer, his students don’t walk even a few feet without trying to figure out the landscape—the boulders, the rocks, the tiny grains of sediment, the volcanic ash—and how it all evolved. “It’s rare to be able to be so immersed in science,” Marchant says, “and it’s a gift I’d like to continue to provide my students.”
Jen Lamp (GRS’16), who is a doctoral candidate in earth sciences and came to BU to work with Marchant, has been on four expeditions to the Dry Valleys. “The first week I was freezing all the time,” she says. “I wasn’t sure I could do it. I was thinking, ‘I’m here for two months, why are we doing this?’” And then after about a week, she not only adjusted, but became a gung-ho convert to the Marchant approach to field geology in a polar desert.
“That’s how Antarctica is,” she says. “That’s how it should be. You’re torn out of this city world. The first week it’s really weird. But then it’s really nice not having to deal with the Internet and people and other distractions. You only have two months out of the year to do all your research in the field. You want to really be there.”
Research here is exciting, thrilling, fun, the adventure of a lifetime—and really, really hard. Instruments malfunction. LCD screens freeze. Batteries are stashed in pockets close to the body to keep them warm enough to function. They die anyway. Some days the wind blows so hard, at hurricane force, that they cannot leave the safety of the tent to do fieldwork. This is boot camp for scientists.
In any research project, things go wrong. But out here, things go wrong constantly. Or, as Sean Mackay puts it, “Everything never works.” They learn to improvise. It’s training in one of the essential qualities a scientist needs: perseverance.
First thing every morning they check in with McMurdo Station via satellite phone or radio to report that everyone is alive and well. If no contact is made, for whatever reason, McMurdo will dispatch a search-and-rescue helicopter; they never miss a check-in.
After breakfast, they head out in teams of two or more. They look for areas to target for collecting samples of rock, volcanic ash, sediment, and ice that can be geochemically tested and dated back in the lab in Boston. They piece together past climate change and how the ice sheet responded to those shifts by reading the landscape.
In everything they do, they are careful not to disturb the delicate environment any more than is absolutely necessary. Some days they move carefully across the landscape with ground-penetrating radar (GPR), a painstakingly slow but valuable method of mapping the geology below the ground surface. In recent years, the team has used GPR to map the location and internal structure of ancient glaciers buried beneath rubble. On other days, they scour the rubble itself, looking for an ideal polygon in which to drill for ancient ice. Marchant and his team look for polygons with deep troughs and elevated central domes that signal an undisturbed portion of ice below. Sometimes they hike for up to 10 miles before they find a suitable polygon. Many days can go by without finding a single one.
The virtual fieldwork Marchant and his students did back at BU gave them a head start in the search for buried ice. But as valuable as the high-resolution satellite imagery and other modern technology are for this research, Marchant says, there is no substitute for actual fieldwork in the Dry Valleys.
“None of the instrumentation leads us to make the next discovery,” he says. “It certainly adds incrementally, but the big leaps we make come from what we observe in the field. We’ll walk and we’ll talk. I’ll point to things, an ancient polygon here, a degraded polygon there; one that has ice underneath, one that doesn’t. You look for spacing and density and subtle, centimeter-scale depressions in the land surface. At first the students won’t see them. You’ll say, ‘You just walked over 10 thermal contraction cracks.’ Once you have your eye attuned to it, you start to see them everywhere.”
They dig soil pits by hand—and there is an art to digging the pits. In each pit there is the possibility of a 15-million-year-old record. The potential for daily discovery is a geologist’s dream, says Marchant.
Drilling into buried ice itself is tricky. Marchant’s team uses a dry drilling technique to avoid disturbing the pristine landscape, an approach that makes it much harder to drill. Without additional lubrication, minor meltwater generated from friction along the core barrel can instantly re-freeze, shutting down the entire drilling operation in seconds. Sometimes the ice cores are fractured and fall apart. When they are able to retrieve an intact core from deep within the ice, it is the culmination of years of preparation and effort.
Volcanic ash can be found in abundance in the upland Dry Valleys—if you know where to look. Deposits are draped over buried soils, trapped in troughs between ancient polygons, and mixed in with sediment. In the skilled hands of Marchant and his team, volcanic ash turns the landscape into a giant time machine. Once dated, the age, distribution, and weathering state of each ash deposit provides a chronology of geological events extending back millions of years. Marchant and his students have used the dating of volcanic ash, as well as other techniques, to decode some of the most significant geological events and climate transitions that have shaped the world as we know it today.
In 2007, Marchant led a team, which included former graduate students Adam Lewis (GRS’05) and Jane Willenbring (GRS’01) (now assistant professors at North Dakota State University and University of Pennsylvania, respectively), to study one of the largest climate shifts of the Cenozoic Era (past 65 million years of geologic history): the Middle Miocene Climate Transition. They found and documented well-preserved fossils of tundra, moss, and insects sandwiched between layers of volcanic ash dated to 14.1 million years ago.
The fossils provided evidence for much warmer conditions than exist today, with reconstructed summertime temperatures at the fossil site of 41°F, and an environment similar to Patagonia at the southern tip of South America. The current summertime temperatures at the fossil site are -10°F. Just above the fossils, in a layer dated with volcanic ash as much as 13.9 million years old, the team found geologic evidence for dramatically colder and drier conditions. Climate reconstruction indicated summer temperatures well below freezing. Perhaps even more striking, says Marchant, is that the team found no evidence in the geological record for a subsequent return to warm conditions. The Middle Miocene Climate Transition they documented for Antarctica cooled the entire planet, and sent interior East Antarctica into a perpetual deep freeze from which it has yet to emerge.
In addition to looking for data on past climate, the team collects records of modern climate by using meteorological sensors that track wind speed, air temperature, soil moisture, soil temperature, and solar insolation. Toward the end of the trip, they connect their laptops to the sensors (they make sure the laptops are warm enough to function by wrapping them inside their coats) and download the data. Some of the sensors will remain in place on tripods anchored to the ground with wire and stakes until they return next year to collect more data.
Students sign on for the Dry Valleys trip not only because they want to go to Antarctica, but for the opportunity to go there with David Marchant, the master field geologist. “Dave’s the man,” says graduate student Andrew Christ (GRS’20). “It’s incredible to be in the field with him. You look out at a landscape and he can pick out a slope and how it wraps around something—or even just a bunch of sediment. He’ll look at it from far away and he’ll say, ‘I think that might be an old delta.’ I don’t know if I see that. Sure enough, we go there and find sands that have melted off a glacier.” The list of student volunteers grows every year.
Marchant has the ability to read the landscape, “with all its history and mysteries,” says Mackay. “He sees not only a story, but he sees it in time.”
Marchant has to assemble all the scattered, broken, and buried elements of that story—rocks, boulders, sediment, sand, volcanic ash, buried ice—himself. “It’s like you have a puzzle that someone’s put together,” Mackay says. “Then another person smashes it, it falls off the table onto the floor. There are some elements of it still put together, but 90 percent of it is missing. His job is to piece all of that back together—not only the pieces, but the process, changes in temperature, changes in ice. You have to put these pieces together to tell the big story.”
In recognition of his research into earth sciences and the East Antarctica Ice Sheet, in 1999 Marchant was awarded the prestigious W S Bruce Medal, which is given every five years by the Royal Society of Edinburgh. The medal has been bestowed upon a number of great polar scientists, including James Wordie, who was geologist and chief scientist on Ernest Shackleton’s 1914–16 trip to Antarctica.
Marchant has also won some of BU’s top teaching awards, including the Metcalf Award and the Dean’s Award for Excellence in Teaching. In June 2014, he was appointed a Howard Hughes Medical Institute (HHMI) Professor—one of just two ever appointed at BU—which recognizes outstanding scientists who are also pioneers in the classroom. As part of that award, Marchant will support at least three undergraduates a year on his research expeditions to Antarctica. For those who can’t make the trip, he says, the HHMI award will be used to fund technology development and instruction in BU’s Digital Image Analysis Laboratory. Undergraduates, with guidance from a technician and graduate students, will be able to see Antarctica from the lab, he says.
Back in Boston, in the lab, they unpack their crates of samples—rocks (as much as 2,000 pounds of them), volcanic ash, sediment, cores of ancient ice—and begin viewing the reams of data they’ve spent weeks collecting in the field. What does it all mean? Just how old—how many millions of years—are the samples? How do these new clues fit into the narrative of past climate change and Antarctica’s Dry Valleys, and what can they tell us about potential future changes?
The lab is the proving ground where theories are confirmed and upended. Until recently, scientists believed that ice couldn’t be preserved more than, say, 800,000 years. They presumed that ice in such a dry and cold climate would quickly sublimate into vapor. But then Marchant made a discovery: eight-million-year-old ice buried beneath thin rubble and dated volcanic ash. Subsequent numerical modeling and fieldwork solved the apparent conundrum: it turned out that, among other things, a millimeter-thick seal of protective ice forms a seasonal barrier on the ice surface, preventing rapid ice loss in areas where intense sublimation occurs. This barrier forms as vapor from the atmosphere seasonally diffuses down into the soil and freezes onto the buried ice.
That is the holy grail–to find and analyze pristine samples of multi-million-year-old atmosphere
The finding corroborated other work by the team and documented the extreme stability of the Dry Valleys landscape, showing that its upland regions have remained unchanged for the past 14 million years. In addition, the findings opened the possibility of reconstructing long-term atmospheric evolution by analyzing gas bubbles trapped in million-year-old ice.
From the BU Antarctic Research Field blog:
If Antarctica is the coldest and driest place on Earth, doesn’t that make it a lot like Mars? What can we learn about a place that is impossible to visit from a place that is only very difficult to visit?
A lot! Marchant and his ever-rotating army of graduate students have spent the past two decades building up a body of knowledge about the Antarctic Dry Valleys that makes this simple, compelling argument: if they can understand what is happening on the surface, they can understand what is happening below the surface, to a surprisingly high level of detail. So while humans can’t visit Mars—yet—the analytical techniques that Marchant’s team has been applying in Antarctica—in particular, the examination of satellite imagery to determine the location of buried ice deposits—can be applied to the Martian landscape. Buried ice can be located, and studied, on Mars, without ever going there.
So when Marchant and his students are working in the Dry Valleys, they are also coming very close to doing fieldwork on Mars.
As NASA gathered more and more high-resolution images from Mars, Marchant and his colleague at Brown University, James W. Head, compared those images with photographs of the polygons in the Dry Valleys. Many of the polygonal formations on the Martian surface showed the same specific geomorphic features as those in Antarctica, features that Marchant had proven were indicators of buried ice.
As part of the advance planning for NASA’s 2008 Phoenix Mars lander mission, officials consulted with Marchant and Head on what the Antarctic analogs might tell them about what Phoenix would find at the proposed landing site. Marchant and Head identified sublimation polygons in the site—just like the ones observed in Antarctica’s Dry Valleys. The conclusion: the chances for finding shallow buried ice were high. Phoenix found ice just below the surface.
In recent years, Marchant’s team has been applying his Antarctica research to questions about climate change and ice ages on Mars. They have found evidence for shallow, buried ice; debris-covered glaciers in craters, and huge ice sheets formerly occupying the Tharsis region of equatorial Mars—and mapped the impact of recent climate change on distribution of ice on Mars. Working with his colleague Head, Marchant says these studies now help inform their understanding of landscape evolution and climate change in Antarctica.
With the presence of shallow ice on Mars, and the recognition that Mars experiences alternating ice ages, the question arises: What about life on Mars? And here, too, Marchant and his colleagues are making progress. In addition to ancient atmosphere, buried ice in the Dry Valleys contains ancient microbes, many entombed for millions of years. With colleagues from Rutgers University, Marchant has found that some of the ancient DNA inside the microbes can be cultured, meaning the cells can be made to grow again under controlled conditions. These studies have helped define the factors that allow cells to remain viable over geologic timescales. This has led Marchant and his team to another question: If life on Earth can persist in ancient ice for millions of years, then could the ice buried just below the surface of the Red Planet offer clues about past life on Mars? And if ancient DNA is found on Mars, could it be resurrected?