This year’s UN COP26 Conference will focus a lot on climate change and its impact on our world. Researchers from UEA’s School of Environmental Sciences at Norwich Research Park are involved in a project to measure how effective vegetation is in extracting carbon from our atmosphere.
Over the past few decades, the Arctic has been warming more than twice as fast as the rest of the planet. At the same time, long-term atmospheric carbon dioxide measurements have shown that the amount of carbon absorbed into and emitted by plants and soil - the terrestrial ecosystem – have increased substantially in the Arctic over many years.
Scientists had assumed this terrestrial ecosystem was playing a significant role in the changes they are seeing in the Arctic carbon cycle, but they lacked a technique to measure carbon uptake and release separately, which is key in understanding how the biosphere responds to climate change driven by fossil fuel emissions.
But a new study based on the modelling of atmospheric measurements of a related chemical - carbonyl sulfide - is providing insights into this important process in the Arctic boreal region, the area of the North American Arctic where vegetation grows.
Carbonyl sulfide is a simple molecule that is very similar to CO2, consisting of one carbon atom, one oxygen atom and a sulfur atom. It is present in the atmosphere in tiny amounts (parts per trillion). Uptake by plants is the dominant process that removes it from the atmosphere. Unlike CO2 it is not emitted from plants when they decay, which enables scientists to take more accurate measures of the amount of carbon being taken up by plants.
A project, which is part-funded by NASA and led by researchers at the National Oceanic and Atmospheric Administration (NOAA), alongside a team of international scientists including those from UEA’s School of Environmental Sciences, has developed a new way of analysing atmospheric measurements of carbonyl-sulfide, together with atmospheric CO2 measurements, to provide information on the total amount of carbon absorbed by land vegetation during photosynthesis.
Professor Parvadha Suntharalingam, from UEA’s School of Environmental Sciences, said: “This work gives us new and valuable information about the processes controlling CO2 uptake by land-based vegetation in the boreal area of the Arctic.
“Carbonyl sulfide is absorbed by plants during photosynthesis, but unlike CO2, it is not released back into the atmosphere by the ecosystem respiration processes. It therefore gives us a way of separating the two key processes - photosynthesis and respiration - that control how CO2 is exchanged between the land vegetation and the atmosphere.
“This research gives us new estimates of the uptake of carbon by terrestrial ecosystems in North American high-latitude regions. It also investigates the influence of other environmental factors - such as temperature and solar radiation - on the processes controlling carbon uptake by these high-latitude ecosystems.”
UEA researchers provided data and information on the oceanic sources of carbonyl sulfide to the atmosphere – ocean emissions are the largest global source. The team estimated plants in Arctic boreal region absorb 3.6bn metric tons of carbon during photosynthesis each year from the atmosphere.
Historical data shows that spring and autumn soil temperatures have increased noticeably from the 1980s. Researchers found that in spring, the warmer soil temperature helps to ramp up the photosynthetic uptake of carbon as sunlight floods the region. However, in autumn, the amount of carbon taken up by plants is reduced because of the dwindling amount of sunlight.
In contrast, when it came to emitting CO2, scientists found the rate was mainly controlled by temperature.
So, what are the implications for the future? Well, one of the big unknowns about the future of the Arctic is whether plant communities there will continue to increase their carbon uptake as atmospheric CO2 rises. One way to obtain a clearer picture is to take more carbon sulfide measurements.
If Arctic surface temperatures continue to rise, the Arctic may start emitting more CO2 than it absorbs, thus exacerbating climate change. Expanding the observation network of atmospheric carbon sulfide measurements could improve scientists’ ability to monitor how much carbon land plants are removing from the atmosphere as CO2 levels increase and climate changes, which would help to improve climate projections of the Arctic region and understanding of carbon cycle-climate feedbacks in the earth system.
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