Influences and interactions of inundation, peat, and snow on active layer thickness

Atchley, A. L.; Coon, Ethan T.; Painter, S. L.; Harp, Dylan R.; Wilson, Cathy J.

doi:10.1002/2016gl068550

Cited by 61 publications

(46 citation statements)

References 65 publications

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“…These two differences may explain why e.g. Atchley et al (2016) find a relatively small influence of water content on the insulating effect at the surface, since their model approach includes an organic layer. Although the focus of our study is on soil temperature, the process-based bryophyte and lichen scheme in JSBACH also provides an estimate of the organisms' net primary productivity (NPP).…”

Section: Discussionmentioning

confidence: 99%

Effects of bryophyte and lichen cover on permafrost soil temperature at large scale

2016

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Abstract. Bryophyte and lichen cover on the forest floor at high latitudes exerts an insulating effect on the ground. In this way, the cover decreases mean annual soil temperature and can protect permafrost soil. Climate change, however, may change bryophyte and lichen cover, with effects on the permafrost state and related carbon balance. It is, therefore, crucial to predict how the bryophyte and lichen cover will react to environmental change at the global scale. To date, current global land surface models contain only empirical representations of the bryophyte and lichen cover, which makes it impractical to predict the future state and function of bryophytes and lichens. For this reason, we integrate a process-based model of bryophyte and lichen growth into the global land surface model JSBACH (Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg). The model simulates bryophyte and lichen cover on upland sites. Wetlands are not included. We take into account the dynamic nature of the thermal properties of the bryophyte and lichen cover and their relation to environmental factors. Subsequently, we compare simulations with and without bryophyte and lichen cover to quantify the insulating effect of the organisms on the soil.We find an average cooling effect of the bryophyte and lichen cover of 2.7 K on temperature in the topsoil for the region north of 50 • N under the current climate. Locally, a cooling of up to 5.7 K may be reached. Moreover, we show that using a simple, empirical representation of the bryophyte and lichen cover without dynamic properties only results in an average cooling of around 0.5 K. This suggests that (a) bryophytes and lichens have a significant impact on soil temperature in high-latitude ecosystems and (b) a processbased description of their thermal properties is necessary for a realistic representation of the cooling effect. The advanced land surface scheme, including a dynamic bryophyte and lichen model, will be the basis for an improved future projection of land-atmosphere heat and carbon exchange.

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Section: Discussionmentioning

confidence: 99%

Effects of bryophyte and lichen cover on permafrost soil temperature at large scale

2016

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“…All analyses were conducted at the Daniel B. Stephens and Associates Laboratory. Measured thermal properties as a function of saturation were compared against common approximations for C and k typically used in thermal and cryohydrogeologic models (e.g., Atchley et al, ; Harp et al, ; Langer et al, ) in the absence of measured thermal properties: the volume fraction weighted approach for C from Hillel () and the Johansen () approach for k as presented in Peters‐Lidard et al (). Values for C for the constituents (i.e., air, water, and solid) are from Table 9.1 in Hillel (); organic matter was neglected.…”

Section: Methodsmentioning

confidence: 99%

Soil Physical, Hydraulic, and Thermal Properties in Interior Alaska, USA: Implications for Hydrologic Response to Thawing Permafrost Conditions

Ebel

Koch

Walvoord

2019

Water Resources Research

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Boreal forest regions are a focal point for investigations of coupled water and biogeochemical fluxes in response to wildfire disturbances, climate warming, and permafrost thaw. Soil hydraulic, physical, and thermal property measurements for mineral soils in permafrost regions are limited, despite substantial influences on cryohydrogeologic model results. This work expands mineral soil property quantification in cold regions through soil characterization from the discontinuous permafrost zone of interior Alaska, USA. Values extend beyond the range of prior measurement magnitudes in analogous regions, highlighting the importance of this data set. Rocky and silty upland soil landscape classifications and wildfire disturbance provided guiding frameworks for the sampling and analysis for potential implications for the hydrologic response to thawing permafrost. Bulk density (ρb), soil organic matter, soil‐particle size distributions (sand, silt, and gravel fractions), and soil hydraulic properties of van Genuchten parameters alpha and N had moderate evidence of differences between silty and rocky classifications. Burned and unburned sites had only moderate evidence of differences for silt fraction. Field‐saturated hydraulic conductivity (Kfs) was more variable at burned sites compared to unburned sites, which corresponded to observations of greater rooting depths at burned sites and observations of root paths in soil cores for Kfs measurement. Soil thermal properties suggested that gravel content may reduce the accuracy of commonly used estimation methods for thermal conductivity. This work provides soil parameter constraints necessary for hypothesis testing and site‐specific prediction with cryohydrogeologic models to examine controls on active layer and permafrost dynamics in upland boreal forests.

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“…This process of energy advection through taliks has been evaluated through numerical simulations (e.g., see review by Kurylyk et al, 2014). Some studies have used numerical models to project the development of taliks in terrestrial environments (Atchley et al, 2016;Engelhardt et al, 2010;Lawrence et al, 2012); however, few have documented and studied them in the field (Jin et al, 2006;Zenklusen Mutter & Phillips, 2012). The presence of relatively shallow taliks in terrestrial systems is rarely reported.…”

Section: /2017jf004469mentioning

confidence: 99%

“…Complete refreeze can generally be assumed in areas of continuous permafrost where low temperatures and abundant ground ice limit thaw (Woo & Young, ); however, talik conditions may also exist locally in colder climates where the ground thermal regime and high snow cover can restrict energy loss over winter. For example, using a permafrost thermal hydrology model and simulating future ALTs, Atchley et al (, Figure 4b) found that taliks may form at Barrow, Alaska, under inundated conditions with heavy snowfall.…”

Section: Introductionmentioning

confidence: 99%

“…In permafrost terrains, most ecological and hydrological processes of interest occur in the active layer, and consequently, there is a need to measure and document changes to active layer thickness (ALT) over long periods of time (Bonnaventure & Lamoureux, 2013;Brown et al, 2008;Tarnocai et al, 2004). The thickness of the active layer is dependent on the surface energy balance, which is affected by many factors, including air temperature (Åkerman & Johansson, 2008;Kane et al, 1991;Sannel et al, 2016), snow accumulation and soil moisture (Atchley et al, 2016;Guglielmin, 2006;Johansson et al, 2013), vegetation composition (Jean & Payette, 2014), slope aspect (Carey & Woo, 1999), and angle (Hannell, 1973). Natural or anthropogenic changes to these variables can lead to changes in ALT.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

et al. 2018

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Measurements of active layer thickness (ALT) are typically taken at the end of summer, a time synonymous with maximum thaw depth. By definition, the active layer is the layer above permafrost that freezes and thaws annually. This study, conducted in peatlands of subarctic Canada, in the zone of thawing discontinuous permafrost, demonstrates that the entire thickness of ground atop permafrost does not always refreeze over winter. In these instances, a talik exists between the permafrost and active layer, and ALT must therefore be measured by the depth of refreeze at the end of winter. As talik thickness increases at the expense of the underlying permafrost, ALT is shown to simultaneously decrease. This suggests that the active layer has a maximum thickness that is controlled by the amount of energy lost from the ground to the atmosphere during winter. The taliks documented in this study are relatively thin (<2 m) and exist on forested peat plateaus. The presence of taliks greatly affects the stability of the underlying permafrost. Vertical permafrost thaw was found to be significantly greater in areas with taliks (0.07 m year−1) than without (0.01 m year−1). Furthermore, the spatial distribution of areas with taliks increased between 2011 and 2015 from 20% to 48%, a phenomenon likely caused by an anomalously large ground heat flux input in 2012. Rapid talik development and accelerated permafrost thaw indicates that permafrost loss may exhibit a nonlinear response to warming temperatures. Documentation of refreeze depths and talik development is needed across the circumpolar north.

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Influences and interactions of inundation, peat, and snow on active layer thickness

Cited by 61 publications

References 65 publications

Effects of bryophyte and lichen cover on permafrost soil temperature at large scale

Effects of bryophyte and lichen cover on permafrost soil temperature at large scale

Soil Physical, Hydraulic, and Thermal Properties in Interior Alaska, USA: Implications for Hydrologic Response to Thawing Permafrost Conditions

The Influence of Shallow Taliks on Permafrost Thaw and Active Layer Dynamics in Subarctic Canada

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