The Arctic is warming at twice the global average and this is predicted to affect a variety of biogeophysical variables, such as precipitation, permafrost temperature, ice mass, snow depth and the composition and composition of Arctic vegetation. On the other hand, different vegetation types influence the surface energy budget (SEB), which is the exchange of energy between the Earth’s surface and the atmosphere. It is therefore very important to ask how the different types of plants found in the Arctic affect the Earth’s energy budget, in order to understand how the exchange of energy in this sensitive area may change in the future.
An international team, led by two researchers from the Department of Evolutionary Biology and Environmental Studies of the University of Zurich (UZH), has now taken into account the factors driving the flow of terrestrial energy in the Arctic. They focused their study on the rotating earth north of 60° latitude, specifically on the extent of the rotating Arctic vegetation map (CAVM). At 64 different tundra and ice study sites across the region, they obtained half-hourly and hourly in-situ observations of energy dynamics and climate change from different monitoring networks, for the period between 1994 and 2021.
Their focus was on the summer months between June and August, when sunlight, and energy absorption, is at its highest. Depending on the type of vegetation, either the surface or the air warms at different rates. Additionally, with increased bush density the soil warms up earlier after winter. The first author of the study, Jacqueline Oehri, says: “The dark branches of the bushes emerge from under the snow early, absorb the sunlight and transmit it to the surface before the snow melts,” explains Jacqueline Oehri, the first author of the study.
In an effort to explain the differences in surface energy fluctuations in different areas, the scientists used discriminant analysis to compare the extent to which 15 selected drivers predicted the mean size of surface energy fluctuations. Drivers include factors such as cloud cover, snow cover, soil and permafrost characteristics, topography, precipitation, air temperature and vegetation type.
According to the researchers, the current Earth system models represent the Arctic vegetation as one or the other active type, while in fact it is very different. In their study, they measured the presence of all the main vegetation classes defined in the CAVM, namely bare structures, grassy tundra, prostrate dwarf-shrub tundra, erect-shrub tundra, wetland complexes, glaciers and boreal peat bog.
Their results, published in the journal Nature Communicationshowed that Arctic vegetation diversity, which is neglected in most climate models, is one of the main predictors of summer energy exchange between the land surface and the atmosphere.
“Surprisingly, in the summer the difference in temperature between the two types of vegetation – such as an area dominated by mosses and mosses, and one with shrubs – is almost the same as between the surface of the ice and the green pastures,” says Oehri.
Researchers suggest that different types of Arctic vegetation have different altitudes, productivity and albedos (solar radiation is reflected rather than absorbed), all of which can affect surface energy fluctuations. Moreover, they say that as the Arctic warms, the abundance and size of different plant species will change, which will further influence climate change.
“What we found about the energy flow in the Arctic is very important, because the maintenance of permafrost depends to a large extent on global warming,” says UZH professor Gabriela Schaepman-Strub. Survey data now make it possible to incorporate the effects of different plant communities, and their distribution, into climate predictions. So researchers can use improved climate models to calculate how much Arctic tundra vegetation is contributing to global warming.
“We now know which parts of plants have a direct cooling or heating effect through energy exchange. “This helps us to see how changes in many Arctic vegetation are affecting the ice and climate,” says Schaepman-Strub.
However, the study highlights important data gaps. Long-term, data on the annual energy variability of Arctic vegetation are still very scarce, and data are missing during autumn and winter in many areas. In addition, observations of bare tundra vegetation are few and far between, although this type of vegetation shows great differences in the flux of excess energy from other types of tundra. The authors believe that new stations are needed in those Arctic regions where data is incomplete, and they call for the current stations to remain operational.
The Arctic is changing rapidly and will have a major impact on the climate dynamics of the entire planet. This study shows the important role of plants in driving energy exchange, and emphasizes the fact that understanding and predicting how plants will be distributed in the Arctic in the future, will help scientists to make more accurate climate predictions in this fragile system, and globally. .
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She is Alison Bosman, Earth.com Staff writer