Differential frost heave model for patterned ground formation:Corroboration with observations along a North Americanarctic transect

摘要

Frost boils in the Arctic are a manifestation of patterned ground in the form ofnonsorted circles. Active frost boils involve convection of water through the soil that canbring basic salts from depth to the surface. As such, active frost boils can mitigateacidification and thereby strongly influence the type of vegetation supported by Arcticsoils. The presence or absence of active frost boils is thought to play a pivotal role inestablishing the sharp demarcation between moist nonacidic tundra (MNT) and moistacidic tundra (MAT) in the Arctic. The focus of this paper is to corroborate the predictionsof a mathematical model that relates observable patterned ground features to ecosystemparameters with observations at the field sites along the North American Arctic Transect(NAAT) established by the Biocomplexity of Patterned-Ground Ecosystems Project.Model predictions indicate that recurrent one-dimensional frost heave can becomeunstable and evolve into multidimensional differential frost heave (DFH). A laboratoryfrost heave simulation produced a 28-cm pattern in an active layer of 10 cm, which agreeswith linear stability theory predictions. A finite element solution predicts three-dimensional patterns with approximately 3-m spacing develop in a 1.0-m active layer witha surface n factor of 0.35, which agrees well with field observations from the NAAT.The lack of significant frost boil activity in the MAT is a result of suppression of DFHowing to denser surface vegetation characterized by low n factors. Prominent active frostboils are observed in the MNT at higher latitudes with more sparse vegetationcharacterized by higher n factors that promote DFH. However, at the northernmost fieldsites frost boils cannot be generated even though the n factors are relatively high owingto very rapid freezing conditions that mitigate DFH.