Active Layer Thickness Prediction on the Western Antarctic Peninsula

Wilhelm, Kelly; Bockheim, James G.; Kung, Samuel

doi:10.1002/ppp.1845

Cited by 12 publications

(63 citation statements)

References 29 publications

(35 reference statements)

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“…Secondly, the fixed 0.1 % minimum difference between the total and unfrozen water contents (to avoid division by zero in the Stefan equation) likely results in different amounts of latent heat of phase change entering the calculations than in the original paper by Wilhelm et al . (), which may lead to significant differences in the predicted ALTs due to the exponential nature of the equation. In fact, changes in the unfrozen water content in the order of tenths of a per cent may produce decimetre‐ to metre‐scale differences in the predicted ALTs in cases when little water is involved in the phase change.…”

Section: Alt Predictionsmentioning

confidence: 97%

“…Note that Wilhelm et al . () incorrectly used the expression ρL for the volumetric latent heat of phase change in their Equations 1 and 2 (i.e. excluding the water content members).…”

Section: Alt Predictionsmentioning

confidence: 99%

“…The ALT recalculations most closely match the original ALTs predicted by Wilhelm et al . () when the unfrozen water contents are set close to or equal to total water contents. Under these conditions, the recalculated values of ALT average 4.6–8.9 m at the solifluction lobe and climate station sites, and 10.1–16.5 m at the bedrock summit site (Figure ; Table ).…”

Section: Alt Predictionsmentioning

confidence: 99%

“…Black solid and dashed horizontal lines represent the original average ALTs and their standard deviations reported by Wilhelm et al . ().…”

Section: Alt Predictionsmentioning

confidence: 99%

“…Wilhelm et al . () examined the ability of the Stefan and Kudryavtsev equations and the HYDRUS thermal model to predict maximum active‐layer thickness (ALT) and active‐layer temperature dynamics at three sites located on Amsler Island (Palmer Archipelago), in the Western Antarctic Peninsula region. The ALT was predicted to be 4.7–8.7 m in soils and unconsolidated materials, and 11.9–18.6 m in bedrock.…”

Section: Introductionmentioning

confidence: 98%

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Discussion on ‘Active Layer Thickness Prediction on the Western Antarctic Peninsula’ by Wilhelmet al. ()

Uxa

2016

Permafrost and Periglac. Process.

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Wilhelm et al. (2015) employed the widely used Stefan and Kudryavtsev equations to predict the maximum active‐layer thickness (ALT) on Amsler Island, Western Antarctic Peninsula. Their predictions far exceed the observations of ALT reported from other parts of the region. Here, I demonstrate that the values of ALT are significantly overestimated by the predictive equations because the authors incorrectly assumed that little or no latent heat of phase change is absorbed during thawing. Although the area is the warmest in the Antarctic Peninsula region, with a rapid increase in air temperature and permafrost temperatures close to 0 °C, the active layer is likely to be substantially thinner than values predicted by Wilhelm et al. (2015). Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Alt Predictionsmentioning

confidence: 97%

“…Note that Wilhelm et al . () incorrectly used the expression ρL for the volumetric latent heat of phase change in their Equations 1 and 2 (i.e. excluding the water content members).…”

Section: Alt Predictionsmentioning

confidence: 99%

Section: Alt Predictionsmentioning

confidence: 99%

“…Black solid and dashed horizontal lines represent the original average ALTs and their standard deviations reported by Wilhelm et al . ().…”

Section: Alt Predictionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Discussion on ‘Active Layer Thickness Prediction on the Western Antarctic Peninsula’ by Wilhelmet al. ()

Uxa

2016

Permafrost and Periglac. Process.

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Influence of soil properties on active layer thermal propagation along the western Antarctic Peninsula

Wilhelm

Bockheim

2016

Earth Surf Processes Landf

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The rate of energy transfer through soils is an important factor governing the active layer (seasonal thaw layer) in polar regions. Energy is transferred through conductive and convective means, which are primarily influenced by the bulk density and water content of soils. With global temperatures changing, it becomes important to understand how soil properties influence heat transfer and active layer depths in climatically sensitive regions, such as the Antarctic Peninsula. In this study we analyzed conductive energy transfer through several soil types on Amsler Island and Cierva Point in the central region of the western Antarctic Peninsula. Active layer temperatures on Amsler Island were monitored every three hours using iButton thermistors installed at regular depth intervals down to 2 m. Soil textures were loamy to sandy with water contents between 5 and 27%. Freezing and thawing transmission rates for all soils ranged from 1.4 to 6.9 cm/day. Thermal transmission rates were fastest in sandy soils with low water contents, indicating that the large, interconnected pores of the sandy soils facilitated the quick movement of heat with water flow through the soil profile. Snow accumulation differences also played a significant role on winter thermal propagation by providing a thermal barrier between the ground surface and atmosphere. Although there was a wide range in thermal transmission among the soils, active layer depths had little variation (7.8-9.7 m). This consistency derives from the greater dependence of very thick active layers on long-term climatic conditions rather than on soil properties. The presence of thick moss significantly slowed thermal transmission and decreased active layer thicknesses. These effects primarily are due to the high heat capacity of water and air retained within the moss, slowing thermal transmission rates, acting as a thermal buffer between atmospheric conditions and the underlying soils.

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Reply to Uxa (2016) Discussion on Active Layer Thickness Prediction on the Western Antarctic Peninsula by Wilhelmet al.(2015)

Wilhelm

Bockheim

2016

Permafrost and Periglac. Process.

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Uxa () used alternative assumptions to calculate active‐layer thicknesses (ALTs) on Amsler Island, Western Antarctic Peninsula, and concluded that assumptions in Wilhelm et al. () overestimate ALTs in the region. Here, we accept that the core of his argument is correct, but we contend that observations using multiple devices, along with the HYDRUS model, indicate that in some cases assumptions used by Uxa () overcompensate and predict an unrealistically thin active layer for the study area. Observed and predicted ALTs are much greater than would be expected, relative to measurements farther to the north. Such a thick active layer could be due to glacial proximity and topographically controlled hydraulic features that promote wetter‐than‐expected soils. Copyright © 2016 John Wiley & Sons, Ltd.

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Active Layer Thickness Prediction on the Western Antarctic Peninsula

Cited by 12 publications

References 29 publications

Discussion on ‘Active Layer Thickness Prediction on the Western Antarctic Peninsula’ by Wilhelmet al. ()

Discussion on ‘Active Layer Thickness Prediction on the Western Antarctic Peninsula’ by Wilhelmet al. ()

Influence of soil properties on active layer thermal propagation along the western Antarctic Peninsula

Reply to Uxa (2016) Discussion on Active Layer Thickness Prediction on the Western Antarctic Peninsula by Wilhelmet al.(2015)

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