Permafrost peatland dynamics during the Holocene: evidence of palsa transformation at Šuoššjávri, northern Norway

As scientists continue to better understand climate change, it is becoming increasingly apparent that ecosystems around the polar regions are warming at an accelerating rate. This poses a particular problem for climate-sensitive ecosystems, particularly permafrost peatlands. Permafrost peatlands are an exceptionally important ecosystem for carbon storage. representing ~45% of soil organic carbon in northern peatlands; however, as cooler conditions are imperative for preserving carbon-rich permafrost sediment, these peatlands are extremely vulnerable to warming. Degradation of permafrost peatlands could be damaging, as thawing permafrost turns the ecosystem into a source of carbon dioxide (CO₂), and subsequent waterlogging of the surface can increase methane. The long-term effects of permafrost degradation remain uncertain; as warming trends continue, permafrost thaw is expected to create a positive feedback loop which would further accelerate climate change. However, thawed permafrost peatlands also have the potential to create a negative feedback loop; productivity and peat/carbon accumulation rates can benefit from the increased nutrient availability and the proliferation of wetland habitats resulting from thawed permafrost.

The focus of this study is Šuoššjávri, a palsa mire located in northern Norway, within the discontinuous permafrost zone. Our project aims to assess the formation/collapse of palsas, their relationships with fire regimes and climate change, and their impacts on in-situ vegetation and carbon storage. We collected three peat cores in a ~10m transect from the top of a palsa to a thermokarst pond, around 3m apart. These cores were analysed using multiple palaeoecological proxies at high resolution (1 cm contiguous samples), to reconstruct past fire frequency, vegetation, hydrological change, and carbon storage over the past ~5000 years.

We hypothesise that (1) regional climatic warming has accelerated palsa degradation at Šuoššjávri, expressed through coupled shifts in ground subsidence, hydrological regime, vegetation composition, and a long-term decline in carbon accumulation; (2) hydrological reorganisation, reconstructed from plant macrofossils and peat physicochemical properties, is the dominant mechanism controlling vegetation succession during palsa destabilisation and collapse; and (3) early warning signals of an approaching critical transition—manifested as local wetting, directional vegetation change, and transient increases in carbon accumulation—systematically precede major palsa collapse events in the palaeoecological record.

This study is funded by NCN project no. 2021/41/B/ST10/00060