Vegetation regulates energy exchange in the Arctic

Newswise — The heatwaves that swept across Europe this summer made many people realize the importance of plants when it comes to cooling down the environment. But how do the different types of vegetation in the Arctic affect the exchange of energy between the earth’s surface and the atmosphere? A highly topical question, because the region is of great importance for the climate. The Arctic is warming at more than twice the global average, leading to thawing of permafrost and melting glaciers regionally. Globally, this warming is reflected in consequences far away from the Arctic, for example in cold damage in ecosystems in East Asia.

Similar heat flux difference as between glaciers and grasslands

An international team led by two researchers from the Institute for Evolutionary Biology and Environmental Sciences at the University of Zurich (UZH) has now taken a closer look at the energy budget of the land surface in the Arctic. According to their study, the diverse vegetation of the Arctic, which is neglected in climate models, is one of the key factors in the exchange of energy between the Earth’s land surface and the atmosphere. “Remarkably, in summer the difference in heat flux between two types of vegetation – say, a landscape dominated by lichens and mosses and one dominated by shrubs – is about the same as between the surface of glaciers and green grasslands,” says postdoc Jacqueline Oehri, first author of the study.

Vegetation types linked to data from 64 measuring stations

Arctic vegetation is very diverse, ranging from dry grasslands and wetlands to shrubland dominated by dwarf shrubs and barrens with mosses and lichens. The researchers linked this vegetation diversity with all available energy exchange data collected by 64 measuring stations in the Arctic between 1994 and 2021. Her focus was on the summer months between June and August, when solar radiation and thus energy consumption are particularly high. Depending on the type of vegetation, either the surface or the air are heated to different degrees. In addition, the soil warms up earlier after the winter with increasing shrub density. “The dark branches of the shrubs emerge from beneath the snow early, absorbing sunlight and releasing it to the surface long before the snow melts,” explains Oehri.

Cooling vegetation can sustain permafrost on the tundra

“Our findings on the energy flows in the Arctic are extremely relevant, since the preservation of permafrost depends heavily on the heat input into the soil,” says UZH professor Gabriela Schaepman-Strub. The data from the study make it possible to include the effects of different plant communities and their distribution in climate predictions. With improved climate models, researchers can calculate whether and to what extent the tundra vegetation in the Arctic plays a role in cooling the land surface.

Precision models require additional measurement stations

“We now know which plant communities have a particularly strong cooling or warming effect through energy exchange. This allows us to determine how changes in plant communities that occur in many regions of the Arctic affect permafrost and climate,” says Schaepman-Strub. In particular, this requires improvements in data collection. Although the Arctic is changing rapidly and has a major impact on the climate dynamics of the entire planet, there are only a few reliable measuring stations in this region. The study authors not only call for existing stations to remain operational, but also believe that new stations are needed in those Arctic landscape types that could only be partially analyzed due to incomplete data.