Vegetation influences Arctic warming

tundra

Grassy tundra with dwarf shrubs in the Siberian Arctic. © Gabriela Schaepman-Strub/ University of Zurich

As a result of global warming, glaciers are melting in the Arctic and permafrost is thawing – with global consequences. However, one important factor has not yet been taken into account in climate models: vegetation. Scientists have now discovered which types of vegetation keep the Arctic soil cool and which also contribute to its warming. These findings could make it easier to predict in future how climate change will affect the region.

The Arctic vegetation ranges from dry grassland steppes and wetlands to scrubland with dwarf shrubs and barren landscapes dominated by mosses and lichens. The different plant types have an impact on how much the Arctic soil absorbs the heat from the sun's rays. Some plants reflect it and keep the ground cool, others conduct the heat into the ground.

vegetation in view

The resulting exchange of thermal energy between the atmosphere and the ground affects how global warming affects the Arctic. It is currently warming more than twice as fast as the rest of the world. This thaws permafrost, melts glaciers, and leads to extreme drought and fires. These problems do not remain local, but have global effects, for example through the emission of greenhouse gases from the thawing permafrost soil or influences on global weather patterns. It is all the more important to find out more about the warming of the region and its consequences.

For this purpose, a team led by Jacqueline Oehri from the University of Zurich examined the various vegetation zones of the Arctic to determine what effect they have on the warming of the large area. To do this, they analyzed data from 64 Arctic measuring stations between 1994 and 2021. Among other things, the scientists evaluated the flow of thermal energy as a function of the plant cover on the ground and various weather parameters. Their focus was primarily on the summer season from June to August, since that is when the sun's rays are strongest and the potential energy absorption of the soil is greatest.

Significant differences depending on the plant type

The result: the different types of vegetation have a significant influence on how much or little the ground and air warm up. The differences between the individual vegetation types were sometimes as great as between the glacier surface and grassland. It was also shown that the surface of a landscape characterized by shrubs wakes up from hibernation earlier than other types of vegetation. "The dark branches of the bushes protrude from the snow cover early on, absorbing solar radiation and conducting the heat to the ground surface long before the snow has melted," explains Oehri.

In the next step, the collected data can now be used to refine climate models and make more accurate regional climate forecasts. "We now know which plant communities have a particularly cooling or warming effect via energy exchange. Now we can calculate how the changes in plant communities seen in many areas of the Arctic will affect permafrost and climate,” says Oehri’s colleague Gabriela Schaepman-Strub. For this purpose, the research team would like to see more measuring stations in the Arctic, especially in landscape types that have so far only been insufficiently recorded.

Source: University of Zurich; Specialist article: Nature Communications, doi: 10.1038/s41467-022-34049-3

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