“The Arctic atmosphere is key to understanding climate change”

A decrease in sea ice, changing vegetation, reduced biodiversity, plastic pollution and altered atmospheric processes: these are just some of the climate-change topics that the 40 scientists participating in the GLACE expedition will tackle. Organized by the Swiss Polar Institute (SPI) and supported by the Swiss Polar Foundation, this expedition will circumnavigate Greenland clockwise for two months between the end of July and the end of September 2019 (see inset below for details).

Fifteen research projects were selected to be run onboard. One of them, which will study how airborne particles influence the Arctic environment, is being led by EPFL. Athanasios Nenes, the principal investigator on that project and a professor at EPFL’s Laboratory of Atmospheric Processes and their Impacts (LAPI), tells us about this important research.

• What is the Arctic atmosphere made of?

The Arctic is a unique environment. It is one of the most climate-sensitive regions on Earth, warming twice as fast as the global average. This accelerated warming is thought to be driven by complex interactions between ice, the atmosphere, the biosphere and the ocean, and airborne particles – also known as aerosols – are thought to play a significant role in this. Much of how the particles interact with the Arctic atmosphere and climate is still unknown.

• What exactly will you study during the expedition?

We will study where the particles found in the Arctic come from – forest fires, biogenic and other natural sources as well as anthropogenic emissions – and how they impact the local climate by absorbing or reflecting sunlight and by affecting clouds. For example, we will look for specific types of molecules that persistently remain dark and absorb sunlight for very long periods of time – including well after they have fallen from the sky and been deposited on ice, which can accelerate melting. The goal is to understand which particles exacerbate the rapid climate change experienced in the region and which tend to help cool the climate.

• Do air particles play an especially important role in the Arctic?

Yes – numerous roles, in fact. Some serve to warm the climate, while others reflect sunlight and, in so doing, can cool the region. Yet others may carry nutrients, like nitrogen, phosphorous, iron and copper; when these nutrient-rich particles fall into the Arctic Ocean, they can act as a fertilizer and promote phytoplankton growth. Phytoplankton is at the bottom of the food chain and absorbs atmospheric carbon dioxide during photosynthesis – so it is very important. We would also like to see if there are significant amounts of airborne biological particles – that is bacteria, viruses and biological debris from both ocean and land activity. Compared to other types of aerosols, there are few biological particles, but some of them are extremely good at triggering ice formation in clouds. When this happens, clouds can rapidly precipitate, and this can greatly affect the amount of sunlight hitting the Earth’s surface. If the cloud cover in the Arctic changes systematically, then we may see rapid changes in ice cover and the local climate.

• What can such tiny air particles teach us about global warming?

Air particles are a key component of the Arctic environment, a complex and rapidly changing system. Studying them is difficult, however, because they act in so many different ways: they can affect clouds, warm or cool the air, melt ice, lead to changes in the biosphere, and the list goes on. If this were not enough, these effects are subtle yet ongoing in ever-changing processes. This opportunity to go to the Arctic and precisely characterize the sources, properties and functions of Arctic aerosol is critically important for our ability to understand current and future changes in the region and around the world.