Determining the rate and shape of Arctic Greening

“We saw landscapes where permafrost has largely collapsed over large areas,” says Sebastian Doetterl, Professor of Soil Resources, with great concern. He has just returned from a field campaign on Svalbard, an archipelago lying at about 78 degrees north latitude, where the thermometer usually climbs to an average of 9 degrees Celsius in summer.

He and 11 other researchers from ETH Zurich, the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and several Norwegian partner institutions had travelled there in mid-July after lengthy, complex and nerve-racking preparations. The team’s goal was to explore the background and mechanisms of the phenomenon known as Arctic Greening – and Svalbard is an ideal field laboratory for this.

One of the biggest and toughest endeavours

Just a few days ago, Doetterl was kneeling in the tundra in wind- and rainproof clothing and a woolly hat to collect soil samples. Now, he sits in his office in shorts and a T-shirt. He seems weary, but the change from the chilly Arctic to the August heat of Zurich isn’t the only reason: the field research on Svalbard itself was challenging – or rather the general conditions there were.

“In terms of scale and difficulty, this endeavour really put my previous fieldwork campaigns in the shade,” Doetterl says. “I’ve never had to deal with such difficult conditions to organize a field campaign as I did on this project, and that’s despite the fact that we also do a lot of field research in regions like the Congo.”

First, the coronavirus pandemic delayed the start of the project by more than a year. Then Russia started its war against Ukraine in February, meaning that the research team wasn’t allowed to use infrastructure operated by the Russian state on Svalbard, which it largely relied on for access to more remote regions. Luckily and almost last minute, the team’s Norwegian partners were able to charter a sailing ship and crew to form an expedition at short notice so that the researchers had a roof over their heads and could reach their study areas.

But the problems were not over: shortly before departure in July, a pilots’ strike at the Scandinavian airline SAS threw the whole venture into jeopardy once more. “If our doctoral students hadn’t reacted so quickly and rebooked flights for all the members of the expedition with other airlines, we would never have made it to Svalbard in the first place,” Doetterl says.

Exploring ecological changes in the Arctic

Longyearbyen, the capital of Svalbard, is the starting point for the team of plant ecologists, soil scientists, geoecologists and microbiologists to investigate the local patterns and mechanisms of Arctic Greening in the coming years as part of an ETH+ project. In addition to Doetterl’s group, the project involves researchers led by Jake Alexander, Cara Magnabosco, Simone Fior (all at ETH Zurich) and Aline Frossard at WSL.

The impetus for this research project came from the fact that global warming is rapidly changing ecosystems. These changes are proceeding at an even faster pace in the Arctic than elsewhere in the world. Temperatures in the high North, for example, have seen a much greater increase than global average temperatures over the past three decades.

This not only causes the glaciers and permafrost to melt, but is also changing soils and plants in the Arctic tundra. Between 1984 and 2012, 30 percent of the tundra in North America became greener, a NASA study has shown. But why some areas of tundra green up more strongly and more quickly than others is probably related to local soil fertility, hydrology and microclimate.

For one thing, the ETH and WSL researchers are focusing on native and introduced plants and how they are reacting to warming. The scientists are also studying how soil development is accelerating and biogeochemical cycles are changing. To this end, they are studying natural tundra soils as well as disturbed soils near settlements and nutrient-rich soils in the vicinity of bird colonies.

Moreover, the researchers want to find out what role microbes play in plant colonisation of young soils and how microbial communities change in better developed soils. From their data, the researchers ultimately hope to derive a model that incorporates changes in vegetation, soils and microorganisms and can be used to predict future changes in Arctic ecosystems and the biogeochemical cycles therein.

Improvisation was the order of the day

Despite all the travails the team faced, Doetterl and the other PIs are very satisfied with how the expedition went. “On site, almost everything went as we had hoped,” he says happily. All the participants were highly motivated; they looked after each other and maintained a very good and collegial working relationship. “That’s not something you can take for granted on a project as difficult as this one and under the sometimes cramped conditions on the ship,” Doetterl says.

With the exception of one location – the authorities closed a settlement because of a stray polar bear – they were able to access all study areas as planned and collect samples: a total of 1.2 tons of soil material. Some of this the researchers shipped frozen to Zurich, where the material will be analysed in the laboratory next winter. In addition, they collected hundreds of plant samples and seed material for experiments back in Zürich, as well as hundreds of microbiological samples.

Research on Spitsbergen

To preserve the genetic material these samples contained, they had to be immediately frozen in the field and transported in liquid nitrogen at −80 degrees Celsius. Given the lack of power supply for this in the wilderness, the researchers sent a tank containing 400 litres of liquid nitrogen at a pressure of 4 bar to Spitsbergen in advance. But the tank developed a leak, so by the time it reached the island after three weeks in storage in Tromsø, there were barely 100 litres left in it. The pressure had sunk to 1 bar. “It was just about enough!” Doetterl says.

The scientists also had to improvise equipment to deal with a software error that caused one of the three drones they had brought along to crash into the ground on its very first mission. However, the cameras it was carrying were still intact. Customizing a new solution on site, the researchers mounted the sensors on the tip of a metal pole that was 4 metres long and took spectral images for all their study sites in a way that was time-consuming but nevertheless with high quality and resolution.

Laboratory work and trip to northern Norway

The intensive first field season will now be followed by a lot of laboratory work and another fieldwork mission next summer. There, the team will study soils, microbial communities and plant ecology in the southern, low Arctic tundra in Norway. This habitat is the warmer equivalent of the high Arctic tundra of Svalbard. After that, it will be time to analyse the extensive data, which will form the basis for an analyses of future biogeochemical cycles in the changing Arctic and their implementation in land surface models. Overall, the project is scheduled to run until 2025.

The fact that this project went so well despite all the adversities was thanks to the three doctoral students involved: Jana Rüthers, Lena Bakker and Sigrid Trier Kjaer. “They’re the ones who organised all the logistics so well, which saved the project. That was a huge achievement,” Doetterl says happily.