June 5, 2023
Vegetation regulates energy exchange in the Arctic

Vegetation regulates energy exchange in the Arctic

Newswise — The heat waves that swept across Europe this summer made many people realize how important plants are when it comes to cooling the environment. But how do the different types of vegetation in the Arctic affect the exchange of energy between the Earth’s surface and its atmosphere? This is a very relevant question, as the area is of great importance for the climate. The Arctic is warming at more than twice the global average rate leading to thawing of permafrost and melting of glaciers on a regional scale. Globally, this warming is reflected in consequences far beyond the Arctic, for example cold damage to ecosystems in East Asia.

Similar heat flow difference as between glaciers and grasslands

An international team led by two researchers from the Department of Evolutionary Biology and Environmental Studies of the University of Zurich (UZH) now has 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 ignored in climate models, is one of the key factors in the exchange of energy between the earth’s surface and the atmosphere. “It is remarkable that in summer the difference in heat flux between two types of vegetation – such as a landscape dominated by lichens and mosses and one with shrubs – is about the same as the surface of glaciers and green meadows,” says postdoc Jacqueline Oehri . first author of the study.

Vegetation types associated with data from 64 measuring stations

Arctic vegetation is very diverse and ranges from dry grasslands and wetlands to shrublands dominated by dwarf shrubs as well as barrens with mosses and lichens. The researchers correlated this vegetation diversity with all available energy exchange data collected from 64 measuring stations in the Arctic between 1994 and 2021. Their focus was on the summer months between June and August, when sunlight and therefore energy absorption is particularly high. Depending on the type of vegetation, either the surface or the air is heated to varying degrees. In addition, with the increase in the density of bushes, the earth warms up earlier after winter. “The dark branches of shrubs emerge early from under the snow, absorb sunlight and bring it to the surface long before the snow melts,” explains Oehri.

Cooling vegetation can maintain permafrost in the tundra

“Our findings on energy flows in the Arctic are highly relevant, as the maintenance of permafrost is highly dependent on heat flow to the ground,” says UZH Professor Gabriela Schaepman-Strub. The study’s data make it possible to integrate the effects of different plant communities and their distribution into climate predictions. Researchers can thus use improved climate models to estimate whether and to what extent arctic tundra vegetation plays a role in cooling the earth’s surface.

Precision models require additional measuring stations

“We now know which plant communities have a particularly strong cooling or warming effect through energy exchange. This enables us to determine how changes in plant communities, which are occurring in many regions of the Arctic, affect the permafrost and climate,” says Schaepman-Strub. This requires improvements in data collection, in particular. Although the Arctic is changing rapidly and has a significant impact on global climate dynamics, there are only a few reliable measuring stations in this region. In addition to calling for current stations to remain in operation, the study authors believe new stations are needed in these types of Arctic landscapes that could only be partially analyzed due to insufficient data.

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