Vegetation types as key in energy regulation of Arctic landscapes. | Polarjournal
The energy balance in the Arctic is determined by the degree of vegetation cover. Researchers at the University of Zurich were able to show that the different types play just as important a role as snow cover, summer temperature or latitude. Image: Greenland, Michael Wenger

It may come as a surprise, but the Arctic is not only an icy ocean, but especially on land, it is a diverse land surface covered with vegetation. And it is precisely this plant growth in the different zones that is important when it comes to creating energy balances, which are important feedbacks in the climate system. To date, however, vegetation types and zones have been put in second place in climate modeling and have been greatly simplified. A research group led by the University of Zurich has now shown that vegetation types play a key role in the Arctic summer energy balance.

Arctic vegetation, whether grass steppes, wetlands, or shrub regions, plays as important a role in the summer heat flux between the Earth’s surface and the atmosphere as latitude and summer temperature. This is the result of the study by Dr. Jacqueline Oehri and Professor Gabriela Schaepman-Strub of the University of Zurich, who conducted the work together with an international research team. The results were published in the prestigious journal Nature Communications this week.

Flickering air over the ground of the nearly dry tundra in Nunavut blurs the muskoxen. The flickering is caused by air turbulence, caused by temperature differences between the ground and the water in front of it. Image: Dr Michael Wenger

In their study, the research team used data from monitoring stations at a total of 64 sites across the Arctic and that had been collected over a 27-year period, providing for the first time a long-term view of what was happening across the Arctic and the different types of vegetation. “Previous either focus on qualitative descriptions of conditions at different sites, or only cover limited geographic extents,” the authors write in their paper. Analysis of the data showed that the type of vegetation determines whether air or soil warms more when solar radiation acts in summer.

The shrubs’ dark branches emerge from under the snow early, absorb sunlight and pass it on to the surface long before the snow melts away

Dr. Jacqueline Oehri, University of Zurich

The extent of this was surprising: “Remarkably, 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 between the surface of glaciers and green grasslands,” says Dr. Oehri, the lead author of the study. In addition, the team found that vegetation type, i.e. whether it is dry tundra or bush tundra, affects the seasonality of energy balance. “The shrubs’ dark branches emerge from under the snow early, absorb sunlight and pass it on to the surface long before the snow melts away,” Dr. Oehri continues.

Arctic warming brings more and more plants from the south to the Arctic north. This has implications for climate, soil, and Arctic wildlife. Image: Dr Michael Wenger

According to the research team, the results of the study provide an important contribution to climate modeling. “Our findings on the energy flows in the Arctic are extremely relevant, since the preservation of permafrost depends to a large extent on the heat flux into the ground,” says Professor Gabriela Schaepman-Strub. “We now know which plant communities have a particularly pronounced cooling or warming effect through energy exchange. This enables us to determine how changes in plant communities, which are occurring in many regions in the Arctic, are affecting permafrost and the climate.” That’s because among the changes associated with Arctic warming is the spread of southern plant species into the far north. This in turn influences the warming of the permafrost. And this is literally the foundation on which the Arctic landscape is built.

Dr Michael Wenger, PolarJournal

Link to the study: Oehri, J., Schaepman-Strub, G., Kim, JS. et al. Vegetation type is an important predictor of the Arctic summer land surface energy budget. Nat Commun 13, 6379 (2022). https://doi.org/10.1038/s41467-022-34049-3

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