Utilizing Suites of Isotopic and Elemental Tracers to Constrain Cryoturbation Rates and Patterns in a Non-Sorted Circle (Abisko, SE).

In this study, we apply a suite of elemental (C, N, Na, Mg, K, Ca, S, P, Pb, Cl) stable isotope (¹³C) and radioisotope (¹³⁷Cs, ²¹⁰Pb, ¹⁴C, ¹⁰Be) tracers to constrain the rates and patterns of soil movement due to cryoturbation in a non-sorted circle (NSC) near Abisko, Sweden. The distributions of elements in the NSC was highly variable, but SOC, Hg, 13C and 10Be exhibited convergent peaks for cryoturbated samples, solidifying interpretations of the surficial origins of cyroturbated parcels that were not identified in morphological sampling.

            Rates of surficial lateral creep estimated from ¹³⁷Cs and ²¹⁰Pb (0 – 2.55 cm yr-1) decreased with distance from the NSC center and were generally an order of magnitude greater than rates of subduction and subsurface movement estimated from ¹⁴C (0.04 – 0.27 cm yr^-1). Estimates of the previous surficial residence times of subsurface cryoturbated parcels based on ¹⁰Be and Hg inventories ranged from 238 – 3940 years. 

The slow apparent rates of subsurface material movement along with the extensive physical and chemical changes that these parcels undergo give an explanation for why recognizable organic materials do not come back up through the center of the frost boil even though the equilibrium cell model predicts that they should. This has implications for the long-term stability of soil organic carbon in these systems due to redistribution from physical processes.  Further applications of this tracer suite with a gridded sampling scheme in NSCs and detailed morphological descriptions should be able to resolve major unresolved questions in the genesis, cycling times and reponse to climate change of NSCs.