Distribution, morphometry, and ice content of ice‐wedge polygons in Tombstone Territorial Park, central Yukon, Canada

Abstract

Investigations of the regional distribution of ice‐wedge polygons and wedge‐ice volume allow for the assessment of the vulnerability of permafrost landscapes to thaw‐induced disturbances and related ecological feedbacks. Ice‐wedge polygons have been described in multiple studies in flat terrain and low‐gradient hillslopes, but few studies have examined ice‐wedge polygons in mountainous terrain. This study investigates the distribution, morphometry, and wedge‐ice content of ice‐wedge polygons in Tombstone Territorial Park, a mountainous permafrost region in central Yukon. Results show that ice‐wedge polygons occupy 2.6% of the park and preferentially develop in woody sedge peat, glaciofluvial, and alluvial deposits along the lower reaches of the Blackstone and East Blackstone rivers on hillslopes ≤1°. The morphometry of five of six polygonal sites studied showed statistically similar polygon sizes and trough angles, while showing different development stages based on vegetation type, surface wetness, and spatial pattern. The estimation of wedge‐ice volumes in the ice‐wedge polygons is 8–22% and is comparable to that of other Arctic regions. However, the estimated wedge‐ice volume represents a minimum value because older generations of ice wedges are truncated 3–4 m below the surface with no evidence of surface polygons, and the polygonal network can be obscured by slope processes, vegetation, and ice‐wedge inactivity. This study provides insights into the application of morphometric and soil parameters for the assessment of ice‐wedge polygon distribution and development stages.

Thermal contraction crack polygons in Nunavik (northern Quebec): Distribution and development of polygonal patterned ground

“…Our results appear to be consistent with these assumptions, but the nature of the substrate is often associated with landforms. 31,69 Our results also show some inconsistencies with the often expressed idea that hexagonal polygons are formed in fine, homogeneous deposits while orthogonal polygons are found in coarse and heterogeneous materials. 1,4,5,26,71 Further insight into the This study provides the first broad-scale empirical dataset describing the spatial distribution of TCCPs, ice-wedge polygons, and their characteristics over a large part of Nunavik.…”

“…It has been suggested that grain size distribution of soil materials and networks and that thermal contraction coefficients may vary with different sediment deposits. 31,68,69 Thus, the stress field within certain substrates would not be homogeneous, such as in tills which are composed of various sediment sizes. 69 However, it can be deduced from our statistics that the shape and extent of the ground surface area exposed to cooling largely determine the 3D homogeneity (mainly orthogonal intersections) or heterogeneity (mainly hexagonal and random intersections) of the temperature gradients in the ground that induce the stress field responsible for thermal contraction cracking.…”

“…Some similar observations have been made previously. 31,[67][68][69] For instance, Haltigin et al 69 proposed that hexagonal and orthogonal networks may derive from different evolutionary paths; that is, orthogonal patterns do not evolve or transition into hexagonal patterns over time, as opposed to other theories implying that networks change after a substantial number of freeze-crack cycles. 4,5,26,27,71 For the orthogonal networks, some vertices may curve slightly over time, but the junction angles will remain mostly at 90 , and no evidence of pre-existing orthogonal cracks was found in the hexagonal polygons (Figure 5c,d).…”

“…4,5,26,27,71 For the orthogonal networks, some vertices may curve slightly over time, but the junction angles will remain mostly at 90 , and no evidence of pre-existing orthogonal cracks was found in the hexagonal polygons (Figure 5c,d). More recently, Frappier and Lacelle 31 suggested that the spatial pattern of polygons is mostly influenced by the nature of the substrate. Our results appear to be consistent with these assumptions, but the nature of the substrate is often associated with landforms.…”

“…1,6,[9][10][11][12][13]21 They are located exclusively in permafrost environments and cover almost a million square miles (2,600,000 km 2 ) in tundra and boreal forest across the Northern Hemisphere. 28 They occur widely in nonbedrock permafrost environments, such as lowland areas, tundra wetlands, alluvial plains, along hilltops, and on glacial deposits, 6,9,13,[29][30][31] and can have different morphologies, being either low-centered, flat, or high-centered. 9 Baydjarakhs, 32 also spelled baydzherakh, 20,33 are patterned fields of mounds resulting from advanced ice-wedge melting in high-centered polygons (see section 8 Terminological note).…”