Recent research led by Rúna Magnússon from Wageningen University and Research (WUR) and Alexandra Hamm from the Department of Physical Geography, Stockholm University, has explored how increasing summer rainfall due to climate change will impact permafrost thaw in the Arctic.

Working with sprinkler during one of the irrigation days. Photo: Anna Johansson.

Rapid Arctic Warming

Air temperatures in the Arctic are rising approximately three times faster than the global average. This accelerated warming is causing permafrost to thaw, which in turn releases greenhouse gasses such as carbon dioxide and methane. This phenomenon, known as the permafrost carbon feedback, exacerbates global warming.

Increased Precipitation in the Arctic

Warmer air holds more moisture, leading to increased precipitation. Although the Arctic is not expected to experience extreme flooding events like those seen in recent years in Western Europe, heavier summer rainfall is anticipated.

Field and Modeling Experiments

Fieldwork during the installation of sensors. Photo: Anna Johansson.

The impact of air temperature on permafrost thaw and carbon release is well-documented. However, the role of summer rainfall is less understood. To investigate this, an international collaboration initiated a series of field and modeling experiments.

In 2018, Rúna Magnússon led a field manipulation experiment in Siberia, using moisture and temperature sensors to monitor the soil after artificial irrigation with water from nearby ponds. The study found that very wet summers increase soil temperature, enhancing permafrost thaw and the permafrost carbon feedback.

Due to the COVID-19 pandemic and geopolitical challenges, further experiments in Siberia were halted. Instead, in 2022, in a collaborative effort, we recreated the experiment in the Svalbard archipelago. We irrigated 64 plots across five locations with ~10,250 liters of water to simulate heavy late summer rainfall. In 2023, Rúna and her group simulated early summer rainfall to assess different timing effects. In this study, we concluded that heavy summer rainfall in Svalbard is unlikely to significantly affect soil temperatures or permafrost thaw, indicating a limited impact on the permafrost carbon feedback in maritime climates.

Putting it all together

Using a state-of-the-art numerical model, we then assessed the impact of summer rainfall across the Arctic. The model suggests what we have seen in the field: permafrost in continental climates, such as Siberia, is more likely to experience soil warming from increased heavy summer rainfall. In contrast, permafrost in maritime climates does not seem to be affected as much or may even experience a slight reduction in the warming rate.

Future Research

Conducted over six years, this project has faced interruptions due to a global pandemic and geopolitical issues but provides initial insights into the role of precipitation in permafrost thaw and carbon release. To fully understand the holistic consequences of climate change on the permafrost carbon feedback more work and standardized protocols for experiments like those conducted in this series are needed.

Video with fieldwork in action

Links to papers:

Siberia

Svalbard

Synthesis

Contact

Alexandra Hamm
Personal webpage