Land cover and fluxes

Challenges: The Arctic and boreal land surface is home to a wide range of coupled processes with major feedbacks on the Earth System that have significant societal effects on the vulnerable economies of northern latitudes and Europe’s welfare. A major challenge is to estimate the Arctic greenhouse gas (GHG) budget. The current focus has been on measuring the two major carbon species CO₂ and CH₄ , however the existing network is still too sparse and most records are too short for differentiating interannual variability from long-term  trends in GHG exchange processes. Therefore it is crucial to maintain and improve the station network to measure both CO₂ and CH₄ in key ecosystems and across all seasons.

Results obtained in INTAROS. We identified the processes controlling CO₂ and CH₄ emissions during the fall period, discovered the occurrence of a later fall soil freezing during the last two decades which correlated with higher atmospheric CH₄ concentration from terrestrial ecosystems in the Arctic. The studies have identified how soil freezing was associated with a sudden increase followed by a drop in soil CO₂ concentration suggesting a peak emission to the atmosphere not captured by the ecosystem scale eddy covariance towers. The role of the spatial heterogeneity on CO₂ and CH₄ emission during the growing season and the fall period has been defined. Furthermore, the studies have identified how snowmelt and growing season length affected the carbon dynamics of tundra ecosystems.  A microbial community active during the cold period has been identified. The development and application of a microbial-explicitly model (CLM-Microbe) has been advanced by improving the model representation of methanogens and methanotrophs in the Arctic. This work has resulted in >25 peer-reviewed manuscripts; supported the research of five PhD students, two master students, six undergraduate students, with considerable interaction with lead scientists in the field, and included the project results in large undergraduate courses.

The team has also been working closely with the Alaska Native Corporation Ukpeaġvik Iñupiat Corporation (UIC) to develop a variety of activities to share the knowledge acquired by this project, and a general knowledge of the effect of climate change on the Arctic with the community and native school children. We disseminated the research results also to the wider scientific community through several EGU sessions we organized in collaboration with scientists from several other institutions in the US and Europe.

Left figures: Carbon flux (daily average) of (a) CH₄, (b) CO₂ and (c) CO₂ + CH₄ (with CH₄ expressed as CO₂-eq based on warming potential) at the three EC sites. The darker shaded portion represents the growing season, while the lighter shaded portion represents the zero-curtain period. Right figure: Location of the three EC towers in Barrow, Alaska. Copyright: Hashemi et al., 2021.

References:

Arndt et al., (2019a, 2019b, 2020)

Hashemi et al., (2021)