Journal
GLOBAL CHANGE BIOLOGY
Volume 28, Issue 20, Pages 5973-5990Publisher
WILEY
DOI: 10.1111/gcb.16345
Keywords
carbon; climate; high Arctic; nitrogen; nitrous oxide; permafrost; vegetation
Funding
- Deutsche Forschungsgemeinschaft [390683824, GO1380/3-1, SCHA1322/12-1]
- Horizon 2020 Framework Programme [101003536, 647204, 951288]
- Max-Planck-Gesellschaft
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Increased nutrient availability following permafrost thawing affects the biogeochemical cycling, greenhouse gas exchange, and nitrous oxide emissions in high Arctic ecosystems. However, there is a weak fertilization effect due to a mismatch between the timing of peak vegetative growth and peak thaw depth, resulting in incomplete plant use of nutrients near the permafrost table.
Biogeochemical cycling in permafrost-affected ecosystems remains associated with large uncertainties, which could impact the Earth's greenhouse gas budget and future climate policies. In particular, increased nutrient availability following permafrost thaw could perturb the greenhouse gas exchange in these systems, an effect largely unexplored until now. Here, we enhance the terrestrial ecosystem model QUINCY (QUantifying Interactions between terrestrial Nutrient CYcles and the climate system), which simulates fully coupled carbon (C), nitrogen (N) and phosphorus (P) cycles in vegetation and soil, with processes relevant in high latitudes (e.g., soil freezing and snow dynamics). In combination with site-level and satellite-based observations, we use the model to investigate impacts of increased nutrient availability from permafrost thawing in comparison to other climate-induced effects and CO2 fertilization over 1960 to 2018 across the high Arctic. Our simulations show that enhanced availability of nutrients following permafrost thaw account for less than 15% of the total Gross primary productivity increase over the time period, despite simulated N limitation over the high Arctic scale. As an explanation for this weak fertilization effect, observational and model data indicate a mismatch between the timing of peak vegetative growth (week 26-27 of the year, corresponding to the beginning of July) and peak thaw depth (week 32-35, mid-to-late August), resulting in incomplete plant use of nutrients near the permafrost table. The resulting increasing N availability approaching the permafrost table enhances N loss pathways, which leads to rising nitrous oxide (N2O) emissions in our model. Site-level emission trends of 2 mg N m(-2) year(-1) on average over the historical time period could therefore predict an emerging increasing source of N2O emissions following future permafrost thaw in the high Arctic.
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