The journal Nature Communications has published research by scientists from TSU (Russia), Umeå University (Sweden), and Midi-Pyrenees Observatory (France). For the first time, the article provides a comprehensive assessment of carbon emissions from the surface of rivers and lakes in Siberia – one of the least studied, but largest, northern ecosystems in the world, experiencing rapid permafrost thawing. The total transport of dissolved organic carbon by all Siberian rivers to the Arctic Ocean was also analyzed, and it was found that nine times less carbon enters there than the water bodies of Siberia emit.
– From 2016 to 2018, we collected data on representative lakes and rivers of Siberia for a distance of more than 2,000 km, including along the main channel of the largest waterway in the Arctic – the Ob River, – says Sergei Vorobyov, one of the authors of the article. – The results showed that the contribution of Siberia to the supply of carbon to the Arctic Ocean and the atmosphere was greatly underestimated, and thus the influence of the macroregion on the formation of the climate on the planet.
The scientists used two methods: they analyzed the concentration of dissolved carbon in water and estimated the scale of emissions using cameras on which sensors were installed that register the concentration of CO2.
Research has shown that not only warm but also cold regions of Siberia, rich in permafrost, make an important contribution to the overall high level of carbon emissions. Warming has accelerated in high-latitude regions, with average annual temperatures rising faster than the global average. Thus, scientific evidence suggests that in the north of Siberia over the past 50 years, the temperature has increased by four degrees. This makes the permafrost more vulnerable to thawing.
– When permafrost melts, it releases a significant amount of organic carbon, which leads to its decomposition and the release of carbon dioxide (CO2) and methane (CH4) into the atmosphere, – explains Sergey Vorobyov. – A significant part of terrestrial inorganic and organic carbon enters inland waters, which entails additional emissions of carbon dioxide and methane from the surface of the water into the atmosphere. The scale of carbon emissions also depends on the type of permafrost zones. Sporadic (insular) and discontinuous permafrost are more susceptible to melting than continuous permafrost, so their contribution to carbon emissions is more noticeable.
In general, the scale of the emissions turned out to be much higher than previously assumed. On average, carbon emissions from the surface of inland waters were 0.08-0.10 Pg C yr−1.
The release of carbon to the atmosphere from inland waters was almost an order of magnitude higher than the export of carbon by rivers to the Arctic Ocean. According to the authors, the scale of emission may be due to the flat terrain of Western Siberia, a large number of bodies of water and a long transit time of water, and favorable conditions for the decomposition and degassing of carbon obtained from land in inland waters.
The authors of the article emphasize the need for further research on carbon emissions, which will contribute to a better understanding of regional differences in the modern carbon cycle and will help to better predict the future of the climate in poorly studied areas sensitive to warming.