Soil Physical and Environmental Conditions Controlling Patterned-Ground Variability at a Continuous Permafrost Site, Svalbard

Watanabe, Teiji; Matsuoka, Norikazu; Christiansen, Hanne H.; Cable, Stefanie

doi:10.1002/ppp.1924

Cited by 18 publications

(27 citation statements)

References 17 publications

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“…The role of rims as preferential outlets of subsurface heat is consistent with the idea that topographic highs in ice wedge polygons cool more efficiently than depressed areas (Christiansen, 2005;Gamon et al, 2012;Watanabe et al, 2017), but conflicts with the idea previously suggested by Lachenbruch (1966), that rim development gradually suppresses ice wedge cracking by increasing snow entrapment in the troughs. It is important to acknowledge that our model does not fully negate Lachenbruch's hypothesis, as conditions not incorporated into the sensitivity analysis, such as vegetation differences between the rims and center, can also influence snow accumulation patterns and energy exchange between the ground and atmosphere (Gamon et al, 2012).…”

Section: Sensitivity Of Ice Wedge Temperatures To Topographysupporting

confidence: 67%

“…This conclusion is supported by prior field studies. In Svalbard, for example, Christiansen (2005) suggested that most of the cooling experienced by an ice wedge occurs through the rims, and Watanabe et al (2017) observed that ice wedge cracking is most active in polygons with well-developed rims hosting minimal snow cover. Along the Beaufort Sea coast in northwestern Canada, it has been observed that ice wedges beneath well-developed troughs crack infrequently, presumably due to the insulation provided by increased snow cover (Mackay, 2000;Burn, 2004).…”

Section: Sensitivity Of Ice Wedge Temperatures To Topographymentioning

confidence: 99%

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Microtopographic control on the ground thermal regime in ice wedge polygons

et al. 2018

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Abstract. The goal of this research is to constrain the influence of ice wedge polygon microtopography on near-surface ground temperatures. Ice wedge polygon microtopography is prone to rapid deformation in a changing climate, and cracking in the ice wedge depends on thermal conditions at the top of the permafrost; therefore, feedbacks between microtopography and ground temperature can shed light on the potential for future ice wedge cracking in the Arctic. We first report on a year of sub-daily ground temperature observations at 5 depths and 9 locations throughout a cluster of lowcentered polygons near Prudhoe Bay, Alaska, and demonstrate that the rims become the coldest zone of the polygon during winter, due to thinner snowpack. We then calibrate a polygon-scale numerical model of coupled thermal and hydrologic processes against this dataset, achieving an RMSE of less than 1.1 • C between observed and simulated ground temperature. Finally, we conduct a sensitivity analysis of the model by systematically manipulating the height of the rims and the depth of the troughs and tracking the effects on ice wedge temperature. The results indicate that winter temperatures in the ice wedge are sensitive to both rim height and trough depth, but more sensitive to rim height. Rims act as preferential outlets of subsurface heat; increasing rim size decreases winter temperatures in the ice wedge. Deeper troughs lead to increased snow entrapment, promoting insulation of the ice wedge. The potential for ice wedge cracking is therefore reduced if rims are destroyed or if troughs subside, due to warmer conditions in the ice wedge. These findings can help explain the origins of secondary ice wedges in modern and ancient polygons. The findings also imply that the potential for re-establishing rims in modern thermokarst-affected terrain will be limited by reduced cracking activity in the ice wedges, even if regional air temperatures stabilize.

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Section: Sensitivity Of Ice Wedge Temperatures To Topographysupporting

confidence: 67%

Section: Sensitivity Of Ice Wedge Temperatures To Topographymentioning

confidence: 99%

Microtopographic control on the ground thermal regime in ice wedge polygons

et al. 2018

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“…The ice‐wedge research site is located on the outermost part of a large late Holocene alluvial fan in the Adventdalen valley, central Svalbard (Figure a). Adventdalen is a broad U‐shaped valley surrounded by flat‐top, 800–900 m high mountains composed of sedimentary rocks of Early Permian to Eocene age.…”

Section: The Studied Ice‐wedge Sitementioning

confidence: 99%

“…The polygons occur mainly as quadrangles, pentagons and hexagons with an average diameter of about 20 m and three‐way junctions (Figure ). The surface morphology shifts into small polygons (< 3 m in diameter), earth hummocks and mudboils toward the loess‐free area higher on the fan …”

Section: The Studied Ice‐wedge Sitementioning

confidence: 99%

Ice‐wedge polygon dynamics in Svalbard: Lessons from a decade of automated multi‐sensor monitoring

Matsuoka

Christiansen²,

Watanabe

2018

Permafrost & Periglacial

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Twelve years of continuous monitoring of diverse ground properties reveals the dynamics of three ice wedges and adjacent ground in a low-centered polygon area in Svalbard. The monitoring documented ground displacements, the timing of crack generation, ground thermal and moisture conditions from the surface to the top permafrost, and snow conditions. The focus is on seasonal ground deformation in and around ice-wedge troughs, interannual variability of ice-wedge activity and thermal thresholds for ice-wedge cracking. Seasonal ice-wedge activity is mainly associated with frost heave and thaw settlement, as well as thermal expansion and contraction.In mid-to late winter, temporary expansion and cracking of troughs by thermal contraction occurs during rapid cooling periods. Following intensive ground microcracking events, troughs show rapid expansion and in some cases major cracking in the frozen active layer. A common threshold for cracking is identified by a combination of ground surface cooling below −20°C and a thermal gradient steeper than −10°C m −1 in the upper meter of ground, indicating that cracking requires both a brittle frozen layer and rapid ground cooling. Our results highlight that in marginal thermal conditions for ice-wedge activity, the primary control on ice-wedge cracking is rapid winter cooling enhanced by minimum snow cover. (eg, 5-8 ). These rules, however, give only rough estimates, because they ignore ground surface conditions (snow and vegetation), and short cold events rather than seasonal conditions may control thermal contraction cracking. 9,10 To date, the widely accepted rule is that ice-wedge pseudomorphs indicate the past presence of (probably continuous) permafrost. 1 Improving the precision of paleoclimatic reconstruction using wedge structures requires more precise ----------------------------------------------------This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…Although individual pattern types have some common features, which allow classification based on morphology and/or site characteristics (e.g. Treml et al , ; Feuillet et al , ; Watanabe et al , ), high variability of shape and size results from a wide range of environmental settings in which they develop (see Goldthwait, ; Washburn, ; Grab, ). Such variability makes it difficult to draw specific conclusions from a purely binary‐data approach.…”

Section: Introductionmentioning

confidence: 99%

Effect of Climate on Morphology and Development of Sorted Circles and Polygons

Uxa

Mida

Křížek

2017

Permafrost & Periglacial

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Sorted circles and polygons are widespread features of periglacial landscapes, but the controls on their development remain poorly understood, impeding their use as palaeoenvironmental indicators. We investigate the relationship of sorted circles and polygons to altitude in the northern Billefjorden area, central Svalbard. The patterns occur in two distinct elevation zones, below 200–250 m asl and above 600 m asl. The higher‐elevated patterns have smaller diameters and shallower sorting depths due to a thinner active layer at higher elevations, suggesting that sorted patterns can indicate climate conditions and ground thermal state when the patterns initiated. Geology is believed to be of less importance for pattern morphology in the study area, causing only its fine‐scale variations. The pattern diameter‐to‐sorting depth ratios have a median value of 3.57, consistent with previous studies and theoretical models of patterned‐ground formation involving circulation mechanisms. Large‐scale sorted patterns may develop over centennial timescales in this high‐Arctic environment. They are probably not in equilibrium with present‐day climate conditions and have probably formed throughout the Holocene. Copyright © 2017 John Wiley & Sons, Ltd.

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Soil Physical and Environmental Conditions Controlling Patterned-Ground Variability at a Continuous Permafrost Site, Svalbard

Cited by 18 publications

References 17 publications

Microtopographic control on the ground thermal regime in ice wedge polygons

Microtopographic control on the ground thermal regime in ice wedge polygons

Ice‐wedge polygon dynamics in Svalbard: Lessons from a decade of automated multi‐sensor monitoring

Effect of Climate on Morphology and Development of Sorted Circles and Polygons

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