A Taste of the Traverse: How to Cross Antarctica without a Plane

Editor's note: Paleoclimate researcher Pete Akers (Institut des Géosciences de l’Enivironnement or IGE in Grenoble, France) is a participant in the 2019-20 East Antarctic International Ice Sheet Traverse (Project EAIIST). Pete is writing about the project in a special series for Category 6. See Pete's author page for other posts in the series.

“Convoi, convoi! On va sept.”  (Convoy, convoy! We go seven.)

The crackle of the radio abruptly snaps you back to reality from whatever trance you’ve developed while gazing for a couple hours at the dual monotony of Antarctic snow and the sled directly ahead of you.

“Ah”, you realize,“the second half of the traverse caravan must be getting a little too close to the sleds ahead and now your group needs to slow down.”

You downshift your tractor into seventh gear from your current eighth and check to make sure your engine RPM and exhaust temperature are still good. With no other notices coming through the radio, it’s time to crank the music back up and continue your steady march across the windy moonscape of the East Antarctic plateau. After all, it’s still six long days until you reach Concordia.

Figure 1. Snow from horizon to horizon: pretty much what you will see anywhere inland in East Antarctica.

East Antarctica is one of the, if not THE, most inhospitable places on Earth. As soon as you leave the coast and head inland onto the snow and ice, you are entering a region where no higher lifeforms can survive other than a few passing birds and very well-equipped humans.

The year-round stations deep in the interior of the ice sheet need vast amounts of fuel and food to support their scientific missions, all brought in from outside the continent. Additionally, the stations are always in need of new or replacement vehicles and maintenance parts. This means that each station requires the import and transfer of thousands of tons of supplies, all made during a short summer window.

The French-Italian Concordia station high on the plateau at Dome C supplies itself in part through a series of “supply traverses” that carry fuel and heavy equipment on sleds pulled by tractors. These traverses start from the Cap Prud’homme base near coastal Dumont d’Urville (DDU) station in Adélie Land, where supplies can be delivered to Antarctica by icebreaker boats and planes. (See map of study area, as discussed in the first post.)

After loading up heavy duty sleds with gear and filling the fuel tank sleds, a caravan of two snow plows, six tractors, and twelve to twenty sleds sets off for Concordia, 650 miles (1100 kilometers) away. These supply traverses are staffed by around 10 people from Cap Prud’homme, and some of these workers have decades of Antarctic experience. The first of these supply traverses leaves Cap Prud’homme in mid- to late November, with two additional traverses completed before the summer season ends in February.

Figure 2. EAIIST members and Cap Prud’homme staff watch as sleds are pulled from Prud’homme station to this staging zone several kilometers away from the station. The initial ascent from Prud’homme is steep and requires multiple tractors to carry each sled, so each sled is brought to the staging zone individually before being hooked together as a caravan. The ocean and icebergs can be seen in the distance.

The official research traverse of our EAIIST mission covers our departure from Concordia station to the Megadunes site, as well as the subsequent return to Concordia. However, as mentioned in my previous blog post, we packed and organized the majority of our equipment for EAIIST at Cap Prud’homme, and all the tractors, sleds, and gear for EAIIST have to get to Concordia from Prud’homme somehow. For this, we embarked on our own “science traverse” on 23 November, two days after the first supply traverse of the season also left for Concordia. While the primary goal of our science traverse was simply to drive and get our caravan to Concordia, we also took the opportunity to do some science sampling along the way. Really, it’s almost impossible to get a group of scientists traveling together without some form of sampling and research happening!

The EAIIST caravan

Although this journey to Concordia station was not officially the EAIIST campaign, our caravan was largely complete and in the same composition as our later actual mission. The main components of our science caravan are:

Vehicles

Our caravan is pulled by five tractors specially modified for Antarctic traverses. They can hold two passengers, and a single tank of fuel gets you about 11-12 driving hours. We have an additional vehicle equipped with a snowplow that usually drives ahead of the caravan to break a path for the caravan to drive on. The plow also flattens the snow around the lunch and overnight stops for easier walking and work.

Figure 3. One of the snow tractors used to pull the sleds on our caravan. Note the treads and engine cover that help the tractor perform in the snow and cold. The sled behind it is the living quarters sled.

Living Quarters

The living quarters for the traverse are, like most of the non-fuel and non-gear sleds, made from converted shipping containers. We have bunks that sleep up to 10 people, a couple desk spaces, and a kitchen/dining room. As you might imagine, space is quite tight, but we all manage to fit together for meals. The living quarters also has our communications, with satellite phone and very basic email. Internet access is very slow and costly, so it is typically reserved only for critical needs and reports.

Figure 4. The dining area of the living quarters.

Figure 5. A view from a four-person sleeping room of the living quarters, with a good feel for the tight fit of the whole place.

Generator Sled

Power for the living quarters and science labs is produced by a large generator housed in another converted shipping container. This space also holds our shower, sink, and toilets, as well as some additional desk space and dry goods storage. There is no direct access between the living quarters and this sled, meaning that if you need to use the toilet in the night, you have to gear up and brave the Antarctic elements for a quick 100 ft (30 m) walk outside.

Science Labs

We have two laboratories on the traverse. Our warm lab is heated to typical room temperature and houses most of our computer-based equipment as well as some tools and supplies. Our cold lab is used to process any ice cores taken in the field, with cutting and bagging of the ice cores done inside the lab. The cold lab is equipped with a cooling unit to maintain the temperature well below freezing at all times, but once we are a couple days’ travel distance from the coast, we can turn off the unit because the outside ambient temperature will be cold enough to keep everything nice and frozen inside. The roofs of both labs are used for storing Styrofoam crates that hold collected snow and ice samples, while small walkways around the perimeter of the lab sleds offer additional space for storing crates and gear.

Figure 6. The inside of the warm lab, with all equipment strapped down and/or packed away for travel.

Figure 7. The cold-lab sled, with Styrofoam containers to store snow and ice core samples on the roof and sides. The equipment at front is our largest ice coring device, and the saw-blade–like object is a pulley used when raising and lowering the core drilling bit.

Gear Sleds and Fuel

The rest of our caravan consists of large sleds packed with seismic and weather stations, food storage, jet fuel to drop off at snow runways, and other bulky items. We also carry several specially designed fuel tank sleds that hold all the fuel needed for the vehicles and generator.

Figure 8. One of our gear sleds (left) and a fuel sled (right).

Configuration

All these sleds and vehicles are hooked together by ropes into two groups: the “life caravan” with two tractors, the living quarters, generator sled, and science labs, and the “convoy” with three tractors, gear sleds, and fuel. The tractors share the load of the sleds better when hooked together, particularly on the steeper and uneven sections of the traverse.

The traverse to Concordia

Each day on the traverse was defined by our strict driving schedule:

7:00 am - Breakfast

7:45 am – Warm-up 0.5-mi (1-km) lap for tractors to prepare engines

8:00 am - Caravan departure for morning driving leg

1:30 pm - Lunch stop with some minimal science work

2:30 pm - Caravan departure for afternoon driving leg

8:00 pm - Stop for night, refueling, general maintenance, and science work

9:00 pm - Dinner

The traverse was able to drive between 6 and 9 mph (10-13 km/hr) and cover 60-90 mi (100-130 km) per day. At this rate, it usually takes 9-11 days to travel the 650 mi (1100 km) and 9 degrees of latitude to reach Concordia. All team members drive the tractors, and on average each member drove for three-quarters of the day, with a couple of people rotating through different tractors through the day to serve as relief drivers. Stopping the traverse during the driving legs is avoided unless absolutely necessary because the sleds can sink in soft snow and tend to freeze to the surface once stopped, making re-starting the caravan difficult. This, of course, cannot be avoided during lunch and overnight, so the departure of the caravans after these breaks is a carefully orchestrated and communicated series of timed starts and gear shifts that get the individual parts of the caravan moving.

The most difficult part of the traverse for the tractors is the very beginning. The ice sheet rises relatively steeply from the coast: Concordia sits at over 10,000 ft (3100 m) in elevation, but you gain two-thirds of this elevation (or more than a mile) in the first three days of travel on the traverse. To the human eye, this still appears to be a fairly gentle slope, but any incline is significant when you are trying to pull tons of weight on sleds. For the first couple of hours’ drive from Cap Prud’homme, extra tractors help pull the caravan up the initial climb. Once the path levels off some, these tractors detach and head back to Prud’homme, and the caravan is on its own for the next 650 mi (1100 km).

This early, steep part is also where you have a risk of crevasses—large and deep cracks that develop on the edge of the ice sheet. Covered by drifted snow, they can easily swallow an entire tractor. Thankfully, a vehicle with ice-penetrating radar travels the path through the crevasse risk zone at the beginning of the season to check that the path is safe and find out whether any new crevasses have developed. The French traverse path from the coast is also blessed by having a relatively low number of crevasses compared to other traverses created or attempted in other parts of Antarctica.

Our science caravan set off from the Prud’homme staging area at 5 pm on 23 November, and soon we were leaving the open ocean and icebergs of Dumont d’Urville Bay far behind for the snow expanse of the East Antarctic ice sheet. Our first night’s stop greeted us with a gorgeous sunset and relatively pleasant weather: a little breeze and temperatures around 15°F (–10°C).

Figure 9. The tractors parked for the night and connected to the generator to keep their engines warm. The “sunset” backdrop is actually directly opposite the setting sun; in polar regions, these pastel-hued skies are very common shortly prior to the onset of the midnight sun or polar night. At these times, the sun grazes just below the horizon for long periods, and the usually brief twilight colors instead last for hours.

This “pleasant weather” was not to last, though, as we were entering one of the windiest regions on the planet. As we continued along our route toward Concordia, the katabatic winds picked up significantly. For the next week, the winds did not drop below 20 mph (30 km/hr) and at times were likely gusting well over 50-60 mph (80-100 km/hr). Combined with temperatures steadily dropping to –15°F (–26°C) and lower as we climbed in altitude, stepping outside the warm tractor cabin after a long driving leg proved to be a brutal shock to the senses.

Figure 10. Stiff katabatic winds drive drifting snow across the “road” to Concordia. This path was cleared two days earlier by plows on the supply traverse, and we followed in their track.

Protective cold-weather gear is provided for every French Antarctic traveler by the French Polar Institute. While each member develops their own personal outfit from the suite of options provided, the outfits all generally include thermal underwear and socks, work pants, an overshirt or sweater, heavy-duty snow boots, and a thick oversuit. Also needed are sunglasses to fight the very bright Antarctic landscape and some type of thermal hat. Since everyone generally looks the same in their provided oversuits, these last two options are usually the only distinctive feature for individuals, and you quickly learn to identify people outside based on what hat and glasses they are wearing.

At every lunch and night stop, each team member braved the wind and cold and quickly got to work on their assigned traverse tasks. My task at each stop was to take a shallow 5-ft (1.7-m) snow core, so I assembled our simplest coring equipment for this task: a 5-ft-long (1.7-m), 3.2-in-wide (8-cm) hollow metal coring bit that attaches to a hand drill. With this coring device, I walked a few dozen yards upwind from our caravan and literally drilled down into the snow with the coring bit. Being upwind of the caravan was very important for my work with nitrates, because the exhaust from the tractors is full of nitrate and other nitrogen-based compounds that would otherwise contaminate the samples. Luckily, the katabatic winds are so dominant here that the wind invariably blows from left to right across the path to Concordia. This means that snow to the left of the caravan path is extremely likely to be uncontaminated by our caravan or any previous supply caravans.

Once my core was drilled, I carried it back to the caravan where it was measured, bagged, and logged in our database. For the rest of the trip to Concordia, the core would be placed in a Styrofoam box that was stored outside on the cold lab peripheral walkway; the cold outdoor environment eliminates any risk of the core melting during transit. This core will later be analyzed in our lab in Grenoble, France, to determine the recent rate of snow accumulation based on density readings of the core.

I also take samples of the core every 0.8 in (2 cm) to see the changing concentration of nitrate and sulfate along its length. Since these concentrations vary seasonally (higher concentrations in summer, lower in winter), we can count back the seasonal cycles to learn the total age of the core. These shallow cores I took will not be very old; at only 5 ft (1.7 m), the cores will cover maybe a year or two of accumulation near the coast and 10 to 20 years closer to Concordia. However, they will help us achieve our goal of matching recent snow accumulation rates with snow nitrate isotope values.

Figure 11. Members of the EAIIST science team help me (middle) take a shallow snow core at a lunch stopping site. The white object I am holding is the coring drill bit. Image credit: Quentin Celle, IPEV (French Polar Institute Paul-Emile Victor).

While I was taking this shallow core, another scientist took snow samples in a pit and along the surface for nitrate and water isotopes. Yet another scientist collected and bagged a filter that had trapped aerosols directly from the air the whole day while traveling, while our other teammates were busy refueling the tractors, cooking dinner, doing mechanical checks and repairs, and refilling our water tank with snow. Dinner may come late (scheduled for 9 pm, but we always wait for the last member to come in from their work before eating), but it’s a welcome time for rest and socializing after a long day.

After a day or two, the novelty of starting the drive across Antarctica wears off, and everyone settles into the routine of the traverse.

Figure 12. Hopefully you like this view, because you’re going to have it for 12 hours each day for 10 days straight.

Despite the vast monotony of the East Antarctic ice sheet, it can be quite beautiful up close. The winds blow streams of snow over the landscape and carve the surface into miraculous sculptures and shapes called “sastrugi”.

Sastrugi form when winds pack newly-fallen snow into hard drifts. Later winds further carve the drifts by physically eroding channels in some spots while depositing more blowing snow in other locations. In many cases, they made the landscape look like a flash-frozen ocean and smaller sections looked incredibly like sculptures of leaping dolphins or schools of fish. The entire East Antarctic Plateau’s surface is dominated by sastrugi; unlike most people’s mental image of Antarctica, almost no place is actually flat.

Figure 13. Some ornate sastrugi formations. These wind-carved structures were most developed between days 3 and 6 of our traverse, where the flat landscape and constant screaming winds combined to boost their growth to maximum dimensions and complexity. Here, the largest sastrugi reached over 3 feet (1 m) in height.

The sastrugi were much appreciated for giving us something to look at during the long drives; however, they also made for very bumpy driving that prevented much-desired naps during driving shift breaks.

As we continued to gain altitude over the days, the landscape gradually flattened and the winds lessened. With the lower winds, the sastrugi grew smaller and the road grew smoother. This signified our entry onto the East Antarctic Plateau. It would take us over five more days and 375 mi (600 km) to gain the final 2500 feet (750 m) of elevation and reach Concordia. Our transition to the East Antarctic Plateau roughly coincided with our last sunset of the trip; the combination of traveling ever poleward and the approaching solstice meant that the sun would be up for 24 hours until near the end of the EAIIST traverse mission in February.

Figure 14. A view of our last sunset of the traverse casting long rays of light across the sastrugi and drifting snow of the East Antarctic ice sheet.

After 10 days of driving, we caught up with the supply traverse 20 km from Concordia Station. The supply traverse was loaded heavier than us and therefore drove a little slower, and they also took a day to re-plow a refueling runway halfway between the coast and Concordia. The two caravans took the overnight stop together, and the mood was joyous at the welcome sight of friends during a reunion apéro (a pre-dinner gathering) to celebrate the imminent arrival at Concordia. The next morning, both caravans joined as one massive convoy to make the final push to Concordia. This caravan was the largest in French polar history (we were pulling every French sled available and all but a couple tractors left at Prud’homme) and possibly the largest in Antarctic history. In total we had 19 people, 11 tractors, 3 snowplows, 14 fuel tanks, and 16 gear, living, and workspace sleds. At one point an hour after our morning departure, we stretched over half a mile (1 km) from the first to last vehicle.

The first view of Concordia’s twin towers on the horizon was a welcome sight for all, followed shortly by radio contact with Concordia station. Concordia station researchers and workers took snowmobiles out to greet the caravan as we slowly made the last few kilometers to our destination, and the entire affair took the feel of a long-anticipated circus rolling into town. As we pulled into the station, we radioed the final gear downshifting sequence and took our convoy to a well-deserved final halt. We all stepped out into the crisp –25°F (–32°C) air and joined the gathered crowd of old and new friends.

Figure 15. Some of the residents of Concordia station (left) welcome the caravan as it approaches.

We would all take some rest over the next couple days, but soon it was back to work. The supply traverse headed back down to Cap Prud’homme after a couple days; after all, they would be needing to come back as the second supply traverse in the near future. The members of EAIIST began adding the final equipment and team members that were waiting for us at Concordia.

With our arrival in Concordia on December 3, we had four days of preparation before our departure on the first leg of the EAIIST traverse toward the Megadunes site. This time, there would be no pre-plowed road to follow—only a heading, six vehicles, and 10 determined team members, all venturing out across East Antarctica in the name of science.

Figure 16. The joint supply-science caravan approaching Concordia station on December 3, 2019. Concordia is barely visible as a dark spot near the horizon to the right of the traverse path.