WHEN THEY SET OUT across the frozen landscape of Svalbard this past spring, the women already knew their expedition was going be extremely challenging physically. But that didn’t turn out to be the hardest part of the journey. The hardest part was having to make decisions in threatening situations and adapt on a daily basis. Like the time when, five days into their expedition, a storm was closing in fast and they decided to dig themselves into snow caves instead of pitching their tents.

“We had heard so many horror stories from expeditions in Svalbard where people were surprised by storms. And it isn’t that the wind is so bad, which it is of course, and it can break your tent, but the problem is mostly drift snow,” expedition member Silje Smith-Johnsen explained. “Your tent can be completely swept under and you can spend an entire night just digging yourself out.” Smith-Johnsen was trained in constructing emergency shelters like this, but in her ten years of visiting and conducting research in the Arctic had never been forced to do so in the field. “When we made our snow caves, it was such a good decision. It was warm, calm, and quiet. We were there with our burners, telling stories. It was such a lovely time. Outside it was mayhem,” she said.

For 29 days, from March 30 to April 27, the four women — Nina Adjanin, Anne Elina Flink, Heïdi Sevestre, and Smith-Johnsen — traversed vast glaciers, sea ice, mountains, and valleys on skis, pulling their belongings behind them, relying on nothing but their physical strength, expert knowledge, and willpower to see them through. (The original team was supposed to comprise six scientists, but two members — Dorothée Vallot and Alia Khan — had babies in the months leading up to the expedition and had to stay behind.) All but one of the “Climate Sentinels” as they call themselves, are glaciologists by training. Adjanin, an expert mountaineer, is a social scientist who researches technology and distance learning in extreme environments.

The scientific purpose of their expedition was to collect snow samples across a 458 km transect of the frozen Arctic to improve our understanding of the carbon cycle. But the team’s core mission transcended the cool objectivity of data points: They were determined to leave no footprint on the landscape they work to protect. They wanted to prove that carbon-neutral field research is possible, even in some of the world’s most extreme environments.

With no mechanized vehicles, heated shelters, or a reliable source of electricity, the women braved the drama of the polar world — the sudden storms, the crumbling ice floes, and yes, even encounters with polar bears — in order to “show the new face of polar research,” to inspire women to break past stereotype-driven expectations, and to encourage the rising generation of scientists to reconsider how science is done in the field.

“WE WANTED TO WORK differently [from] how we had been trained, in a way that was more respectful to the environment,” Sevestre explained to me during one of two pandemic-style videoconferences I held with the Climate Sentinels after their expedition. Sevestre, a French national currently based in the French Alps, has conducted research in Svalbard, Greenland, and Antarctica for more than 10 years studying the dynamics of glaciers. In recent years, she has been focusing on science policy and communication and heads the global outreach effort of the International Cryosphere Climate Initiative, a network of policy experts and researchers working to preserve Earth’s ice and snow-covered regions.

The team members, who are all in their early 30s and fearless outdoors explorers, refuse to identify a leader, and it was clear throughout our conversation that the bond between them abhors a hierarchy. But Sevestre is the strong voice of the team, who sets out the Sentinels’ position on the important issues of sustainability and feminism warmly and confidently. She explained to me that the days when polar science was conducted on skis are long gone, and that most field projects today rely on energy-intensive means of transport, either helicopters or snowmobiles, to hover above and zip around the ice. To the Climate Sentinels, this goes against the need for low-carbon practices in all industries, including polar science itself, if we are to avoid the worst-case projections for global warming.

The idea of a low-emissions expedition took seed five years ago when the women, who knew each other from shared fieldwork experiences in Svalbard and polar research conferences, began talking about the enormous carbon footprint of polar research. “We wanted to organize an expedition that was in our image, and to really take control of the kind of fieldwork we wanted to do,” Sevestre said. Svalbard emerged as an obvious location for their trip, since they had all had previous experience working there.

The Svalbard archipelago is situated midway between the North Pole and the northernmost coast of Norway’s mainland. In 1933 Christiane Ritter, the first European woman to overwinter in Svalbard, described the archipelago as permeated with “a titanic drama,” where “people are intoxicated by the vital breath of untamed nature.” Today it remains one of the most dynamic landscapes in the world, and globally it is the environment that is changing the fastest due to the effects of a warming climate. The seasonal sea ice connects the islands and separates them in the summer. Fjords and glaciers continuously redraw the contours of land. Polar bears move on and off the shore hunting for seals among the spring ice floes. It is an unpredictable, volatile environment that can undergo dramatic transformation on the scale of hours.

According to a 2021 study in the Journal of Glaciology, over the next 40 years the average mass of Svalbard’s more than 2,100 glaciers, which cover 59 percent of the region, is anticipated to enter a phase of accelerating decline even under the temperature targets of the Paris Accords. This will mean a shorter snow season and more rain. The combined runoff from glaciers and land is expected to more than double by 2060.

Scientists have, of course, long studied this region and how it is being impacted by climate change. The archipelago is dotted with research stations. But “most expeditions traverse [Svalbard] North to South, or South to North,” explained Smith-Johnsen, a native of Norway who has special training as an Arctic Nature Guide and has just completed her doctorate in glaciology. “We wanted to fill in the gaps in knowledge… We wanted to collect snow samples where none had previously been collected,” she said.

Conceiving an expedition is one thing, bringing it to fruition quite another.

To do that, the Sentinels decided on a route that would traverse the archipelago from Northwest to south Svalbard. “We looked at all the black carbon data, and it is collected around the big research settlements, which are Longyearbyen, Ny-Ålesund, and Hornsund in the South. You can plot a circle around these areas and this is where the research is done. We tried to come up with a route that filled in the gaps in between, where no data at all had been collected,” she explained.

But conceiving an expedition is one thing, bringing it to fruition quite another. To raise the necessary funding the Sentinels approached corporate partners and private donors directly. “We had to fight every step of the way,” Sevestre said. “I remember contacting sponsors who were extremely skeptical. They kept digging, asking ‘Are you sure you know Svalbard enough? Do you think you will finish the expedition? How confident are you in the team?’ We had to try and prove ourselves twice as hard because we were women.”

The Covid-19 pandemic added further challenges. Not only were the Sentinels forced to postpone their plans by a year, they also couldn’t organize a team training in advance of the actual expedition. Preliminary team-training activities to test equipment and gauge the physical capabilities of the team are typical for polar or high-altitude work. It is an opportunity to fine-tune the weight of the pulkas, the Nordic sleds they used to pull their belongings, to test the durability and performance of field gear, and for the team members to bond. Instead, the women had to leave such testing to last minute adjustments before their trip, and trust that everything would go smoothly.

SINCE 1920, with the exception of the war years 1941 to 1945, Svalbard has been under Norwegian control. A coal mining community rose and fell on the islands in the twentieth century, and today the main economies here are fishing and science. A year-round community of polar scientists is situated in the town of Longyearbyen, the northernmost settlement on Earth. This is where the Climate Sentinels met in mid-March.

The women spent a week together in Longyearbyen packing their rations, practicing avalanche and glacier rescue, first aid, shooting, and getting to know the two huskies who would be helping them pull their equipment. On March 30 after almost 14 hours of sailing, the team reached Ny-Ålesund — a village with research stations and scientists from over 10 different countries — the starting point of their expedition.

The Sentinels had split their expedition roughly into three ten-day segments — broken by pit stops to replenish supplies, send back snow samples to Longyearbyen, and rest. The first leg took them from Ny-Ålesund to Pyramiden, a former Soviet settlement that’s morphing into a popular spot for tourists and explorers. This leg involved crossing some large glaciers and deep fjords. From there they trudged another eight days southward to the former mining town of Sveagruva. The last leg of the expedition, from Sveagruva to the Polish research station of Hornsund, involved a week of skiing through “one of the most alpine looking fjords of the archipelago,” according to a description on the Sentinels’ website. It was also “the most technical and wildest” leg as the team was “highly dependent on sea ice, and vulnerable to highly crevassed glaciers.”

Throughout the trip the women averaged 15 to 20 kilometers a day on skis, weather permitting. Occasionally they were forced to ski through the night to find shelter due to bad weather. For the first two weeks of their trip the Sentinels were plagued almost daily by storms. They skied against gusts that exceeded 36 meters per second.

“In all these windy and difficult situations, we had to stop for science. It is cold, but you stop, dig, put on gloves, collect the sample and only then move on,” Adjanin, a German citizen by birth and citizen of the world by choice, explained to me. “In my previous expeditions, there have always been more people. When we climb in the Himalayas, for example, if you don’t have a lighter you can always go and ask another expedition for a lighter. And here, it was just us. For me that was a very powerful change,” she said.

When they reached Pyramiden, on day 12 of their trip, the researchers decided to leave their dogs with friends and fellow scientists stationed there, who would return them to Longyearbyen. “The dogs ate two kilos of food each every day and they were not used to assisting skiers. It wasn’t worth keeping them, and in some cases, it became dangerous, as they did not keep to a straight line,” Sevestre said. “We missed their company, of course, but it was the right decision,” Smith-Johnsen added.

For the rest of the journey the women on skis pulled their own supplies tightly packed on pulkas. These contained everything from their tents and scientific equipment to their food as well as their waste, which they did not leave behind. “We used fresh snow for potable water. We boiled it on a small stove and then kept it either in a thermos or in Nalgene bottles. I kept mine in a flexible bottle in my bra, keeping it warm against my skin,” Smith-Johnsen explained.

During the final push the women had to show yet again their ability to handle the unexpected. “So much ice in Hornsund that boats cannot reach the station” their friends at the station texted them, just as they were planning their approach. This meant they would not secure a passage home from Hornsund. So rather than ski there, the women went off course and called it a day at the empty settlement of Calypsobyen, where they spent a few days before being picked up by a boat that took them back to Longyearbyen.

DURING THE COURSE of their journey, the researchers collected a total of 92 snow samples, stopping regularly along their route. Scientific sampling chores were distributed evenly among them. At every sample site, they had to work fast to avoid cooling down after the intense skiing. Sweating can be life-threatening in the Arctic. Moisture does not evaporate easily in the cold, and damp layers of clothing can suck heat from the body, sometimes resulting in hypothermia. In order to avoid prolonged stops, the women worked synchronously. Adjanin wrote down the measurements, Smith-Johnsen took GPS coordinates and recorded the thickness of the snow cover at the sample site, Sevestre measured the snow density, while Flink was responsible for collecting the precious snow sample.

“You have to use plastic gloves, not touch the snow, not to contaminate it. It is sometimes way too cold to do this without warm gloves,” she told me. Temperatures in Svalbard at this time of year can drop to -25C. “We used a stove to cook our food, so there is a possibility of some traces of soot being around the hands, so you need to take extra care when collecting the sample.” Like the other team members, Flink has plenty of research as well as field experience. Originally from Sweden, she has spent two summers guiding scientists in Antarctica. “The snow that we sampled is fresh, this year’s snow,” she said. “It is a snapshot, and a Covid snapshot too. We hope it can help us understand the difference in emissions between pandemic and regular years.”

“The snow samples collected, on their own, weigh nothing. They are just a little bit of snow in a tube. But you have to insulate them with more snow and store them in a polystyrene box,” Flink explained. “At the end of the trip the box weighed around 4 kilos.” After the expedition the samples were shipped to Khan’s research team at the Western Washington University in Bellingham. There they will be assayed for their concentrations of total carbon, and what is known as “black carbon.” The latter is essentially partially combusted fuel, a fine soot that is carried into the air with emissions, which falls to the ground mixed in with precipitating snow. Black carbon can decrease the albedo effect of snow on the ground, that is, its reflective properties that help keep the Arctic cool.

Increasing deposits of black carbon hasten the melting of Arctic snow, contributing to an escalation of the planet’s warming. The Climate Sentinels collected the snow samples so they can decipher the origin and composition of the black carbon within. With the right laboratory work-up, it is possible to glean what kind of fuel — ranging from diesel inside a combustion engine to char from forest wildfires — was burned to produce a particular sample of black carbon. Eventually this information will be coupled with weather models, in order to sleuth out not only the nature, but also the geographic source of the pollutant.

“Recently we are seeing a real shift operating in the sources of black carbon that are being deposited in the Arctic,” Sevestre told me. “There are some sources that we already know a lot about, south of the Arctic Circle, such as from wildfires and areas where there is a lot of industrial activity. But more recently we are also seeing a lot of human activity in the Arctic, so these emissions are coming right from the Arctic itself. Wildfires have been raging in the Arctic even in winter.”

“It is very important to us that we get an academic result from this,” Flink added. “It was a main goal with this expedition; we would like to publish the results. But beyond that we want our data and findings to help inform local government and be part of public outreach too.”

“We realized very early on how extreme it is what we set out to do.”

Adjanin, who researches how technology can help aid remote learning about extreme environments, has been especially interested in figuring out how to make the polar regions more accessible to students. “Polar regions are on the curriculum for study at most universities, so how do we bring this part of the world to life? Public outreach through technology is the answer,” Adjanin told me. To that goal, as much as connectivity and the battery life of their solar-powered devices permitted, the Sentinels sent daily updates about their expedition through their Twitter and Instagram channels.

Post expedition, they continue to engage with students throughout the world to showcase their emphasis on sustainable data collection in the field. “I have been getting a number of prospective graduate students who have found me through Climate Sentinels,” Khan told me. “I am very grateful for that because it makes recruitment of highly motivated students easier.”

Despite the expedition’s success, many scientists remain skeptical about the possibility of all polar research ever having a zero carbon footprint.

“Not all polar science can happen this way,” Dr. Nicholas Pilfold, a polar bear biologist who uses helicopters regularly to survey populations of polar bears in Western Hudson Bay in the Canadian Arctic, told me. “There are circumstances when motorized transport is required, and the burden shouldn’t be on the scientists to cut their emissions completely just because they are studying the climate. We are here to collect the necessary data that is required to inform the models and help us all act accordingly. The process of scientific enquiry should not be impeded.”

The Climate Sentinels do not entirely disagree. “We realized very early on how extreme it is what we set out to do,” Sevestre said. “It is very difficult to pull all your belongings with you for one month on skis and hope to collect the best data that you think you can get. It is not realistic to expect that this type of transportation should be applied to all fieldwork in the Arctic.”

What they hope instead is that their endeavor will inspire other scientists to, at the very least, consider ways to reduce the carbon impact of their field research. And that, it seems, is already happening. “We acknowledge that many instruments are too heavy or too power hungry to be taken out into the field by hand,” Adjanin said, “but lots of my colleagues, including engineering experts, are now thinking about how to adapt their tools to use less fuel in the field, to be less heavy, to help scientists lower their carbon footprint.”

WHEN I ASKED the women whether they argued during their trip they looked at me incredulously. “From the very beginning we were able to respect each other’s opinions, feelings, and intuitions, and we never had any egos in the way. This is how we avoided quite a lot of trouble,” Sevestre told me. “The truth is I am confident that the only reason we were able to complete the expedition was because we were an all-female team,” she added.

All-female teams are inherently different from both male-only and mixed-gender teams, Carole Jahme, a University College London-based evolutionary psychologist who studies the “female brain,” told me over a call. “Women have higher levels of estrogen — the hormone that’s necessary for the uptake of oxytocin — in their bodies than men,” she explained. “Oxytocin is the hormone that enhances cooperative behavior, social bonding, attachment, and, she added, “it also facilitates mind reading.” That latter bit gave me pause. So Jahme explained: “‘Mind reading’ is the ability to communicate non-verbally, by assessing a situation and responding to it quickly, intuitively, with confidence that the group will respond cohesively.”

“The only reason we were able to complete the expedition was because we were an all-female team.”

“If you are in a dangerous environment that is fluid and constantly changing like the Arctic, where you might need to think rather quickly, it certainly helps being able to communicate without speech and to implicitly know that you are in a group that cooperates without competition,” she said. “Males are different — they always compete and look to build a hierarchy within the group.”

In Jahme’s opinion, when the decisions are made based on the knowledge of only one of the team members, a dangerous outcome is more likely. “If it is okay to generalize,” Jahme continued cautiously, “in general, compared to females, males experience difficulty adapting to environmental change and will be slow or reluctant to adapt plans and conceive new goals. Females on the other hand view adaptation as a form of success, to the environment and their circumstances.”

The Climate Sentinels certainly bear out this assessment. Their original plan comprised a longer trip, along a different route. Instead, on several occasions they made emergency stops, deviated from their planned route, and sheltered in trappers’ huts instead of out in the open, especially where encounters with polar bears were likely. “I am so proud that we did not need to be rescued, that we completed our expedition,” Smith-Johnsen said.

It was refreshing to hear from Jahme a perspective that celebrated the achievements of women in polar science that were because of rather than despite their sex. Women are enormously underrepresented in climate science. They make up only 23 percent of the authors of the most recent report by the Intergovernmental Panel on Climate Change, for instance. “This is even more strongly the case in technical sciences such as glaciology,” Flink said. “When it comes to polar expeditions, this is starkly the case. We are here to increase the visibility.”

A particular challenge women face in field science, however, is integrating family planning with expedition work. Case in point: Vallot and Khan were indispensable core actors in the campaign to bring their project to life, but ended up being Climate Sentinels “at a distance,” since they both had babies in the months ahead of the expedition.

“After years of preparing for the campaign, specifically the scientific objectives, grant writing, and fundraising, it was hard to watch the field expedition from home,” Khan wrote to me over email.

“There should be more discussion around maternity and research and how to adapt fieldwork to it,” Vallot said.

Both Khan and Vallot are passionate about continuing their careers in glaciology and see a future that includes their children in the fieldwork they do. “I want my children to be aware of everything that I am doing and what the Climate Sentinels do,” Vallot told me. “I want to pass to my son and daughter the love of snow and ice.”