Palsa Uplift Identified by Stable Isotope Depth Profiles and Relation of δ¹⁵N to C/N Ratio

Summary

This field study demonstrates that stable nitrogen isotope (δ15N) depth profiling, when related to C/N ratios, can reliably identify the depth at which permafrost uplift perturbs peat structure in palsas. By analysing two peatland sites in northern Sweden, the authors identified a characteristic δ15N pattern with peak values at the 'turning point' where uplift occurs, allowing dating of permafrost aggradation to the Little Ice Age period. The approach offers a novel palaeoclimate and permafrost dynamics assessment tool for peatland systems.

UK applicability

This methodology may have limited direct application to UK lowland agriculture, as the UK has no extensive active permafrost or palsa systems. However, the isotopic profiling technique could inform palaeoecological studies of past periglacial conditions in upland regions during the last glacial cycle, and the approach to detecting soil perturbation via stable isotopes could be adapted for other UK soil dynamics research.

Key measures

δ15N values, C/N ratios, depth profiles, peat accumulation rates, timing of permafrost aggradation onset

Outcomes reported

The study used δ15N depth profiles in relation to C/N ratios to detect peat perturbation caused by permafrost-driven palsa uplift in two Swedish peatlands. Nine of ten soil profiles showed a detectable perturbation signal at the depth of permafrost-initiated uplift, with permafrost aggradation onset dated to between 80–545 years ago (mean 242–365 years), coinciding with the Little Ice Age.

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