20-year observation of Alaskan permafrost forests reveals 20% increase in CO₂ sink

The permafrost in the Arctic is covered by forests. One possible result of global warming is that the melting of this permafrost may release large amounts of organic carbon from the soil, while forests on permafrost may grow and absorb more CO₂. Long-term observational studies are needed to determine the effects of global warming on the entire permafrost.

A joint research group led by Associate Professor Masahito Ueyama of the Graduate School of Agriculture at Osaka Metropolitan University, Associate Professor Hiroki Iwata of the Faculty of Science at Shinshu University, and Assistant Professor Hirohiko Nagano of the Graduate School of Science and Technology at Niigata University, used a meteorological observation tower with the capability of real-time monitoring of the CO₂ source and sink in forests to monitor their changes over 20 years from 2003 in a forest in Alaska, U.S.A. The analysis revealed that the CO₂ sink during 2013-2023 increased by about 20% compared to the previous decade. The increase was attributed to increased photosynthesis, mainly due to recent increases in precipitation and CO₂ concentrations.

The long-term observation data over 20 years for a forest on permafrost disclosed in this publication marked a world record length of observation for permafrost forest research. This data also revealed a persistent increase in the CO₂ sink in a high-latitude forest and its causal association with the atmospheric hydrological cycle and anthropogenically increased CO₂ concentrations.

Even longer-term observational studies are needed since it is difficult to apply the findings and data from this 20-year observation directly to future predictions associated with predicted further acceleration of global warming. Nevertheless, the findings and data from the present study are expected to help validate and improve global warming prediction models and thereby contribute to improving the accuracy of global warming predictions.

Since various ecosystems are established in high-latitude regions, the results obtained for a single forest cannot be used as knowledge applicable to the entire ecosystem in these regions. Therefore, it is desirable to conduct international joint research by bringing the data from surveys at more sites together. The study was published as an advanced online publication in PNAS.

Ueyama said, "It took a lot of patience to maintain and manage the observation systems exposed to a harsh environment for more than 20 years and accumulate high-quality data. The Arctic wilderness, the northern lights that I see during maintenance each year, and the connections with researchers in Japan and other countries that increased as my research developed are a great source of vitality."

Journal Information
Publication: PNAS
Title: Anomalous wet summers and rising atmospheric CO₂ concentrations increase the CO₂ sink in a poorly drained forest on permafrost
10.1073/pnas.2414539121