Widespread permafrost vulnerability and soil active layer increases over the high northern latitudes inferred from satellite remote sensing and process model assessments

Park, Hotaek; Kim, Youngwook; Kimball, J. S.

doi:10.1016/j.rse.2015.12.046

Cited by 105 publications

(74 citation statements)

References 52 publications

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“…Another study using spatially referenced soil profile data and environmental variables produced ALT estimates across Alaska ranging from 14 to 93 cm, with a spatial average of 46 cm (Mishra and Riley, 2014). A follow-on study estimated the mean ALT across Alaska to be between 42 and 49 cm with 95 % confidence (Mishra et al, 2016) main, which is larger than our model results and the previous study by Pastick et al (2015). Our model predicts relatively stable permafrost conditions in continuous permafrost areas during the study period, which is consistent with previous reports (Osterkamp, 2007;Jafarov et al, 2012;Nicolsky et al, 2017).…”

Section: Discussioncontrasting

confidence: 78%

“…A study using an empirical data fusion and modeling approach incorporating extensive field observations and spatial environmental datasets (Pastick et al, 2015) estimated that near-surface (< 100 cm) permafrost encompasses 38 % of mainland Alaska, with a mean ALT of 50 cm. Our model baseline simulations indicate a similar near-surface (< 100 cm) permafrost extent encompassing ∼ 40 % of the Alaska domain, with a mean ALT of 58 cm.…”

Section: Discussionmentioning

confidence: 99%

“…The OLT observations were used to define the depth of the model soil layers with 100 % SOC fraction; this simplifying assumption was made in the absence of more detailed SOC profile measurements and to facilitate the model parameterization process. There are ∼ 60 in situ CALM sites across the Alaska study domain, with 35 sites located in areas with permafrost probability (PP) ≥ 70 % estimated from an ancillary permafrost map (Pastick et al, 2015).…”

Section: In Situ Datamentioning

confidence: 99%

“…More recent attempts have also incorporated ground-based remote sensing, such as ground-penetrating radar (GPR) and electrical resistivity measurements, but only over limited local extents (Sjöberg et al, 2015;Jorgenson and Grosse, 2016). Several studies have used empirical models driven by in situ ground observations and other geospatial datasets to provide fine-scale (< 100 m resolution) estimates of active layer and near-surface permafrost conditions (Mishra and Riley, 2014;Pastick et al, 2015). However, the accuracy of these methods is limited by the ability of sparse ground measurements representing landscape heterogeneity, and the resulting empirical models provide only limited insight and mechanistic understanding of underlying processes affecting active layer conditions.…”

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confidence: 99%

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Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Kimball

Chen

et al. 2018

The Cryosphere

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Abstract. An important feature of the Arctic is large spatial heterogeneity in active layer conditions, which is generally poorly represented by global models and can lead to large uncertainties in predicting regional ecosystem responses and climate feedbacks. In this study, we developed a spatially integrated modeling and analysis framework combining field observations, local-scale ( ∼ 50 m resolution) active layer thickness (ALT) and soil moisture maps derived from low-frequency (L + P-band) airborne radar measurements, and global satellite environmental observations to investigate the ALT sensitivity to recent climate trends and landscape heterogeneity in Alaska. Modeled ALT results show good correspondence with in situ measurements in higherpermafrost-probability (PP ≥ 70 %) areas (n = 33; R = 0.60; mean bias = 1.58 cm; RMSE = 20.32 cm), but with larger uncertainty in sporadic and discontinuous permafrost areas. The model results also reveal widespread ALT deepening since 2001, with smaller ALT increases in northern Alaska (mean trend = 0.32 ± 1.18 cm yr −1 ) and much larger increases (> 3 cm yr −1 ) across interior and southern Alaska. The positive ALT trend coincides with regional warming and a longer snow-free season (R = 0.60 ± 0.32). A spatially integrated analysis of the radar retrievals and model sensitivity simulations demonstrated that uncertainty in the spatial and vertical distribution of soil organic carbon (SOC) was the largest factor affecting modeled ALT accuracy, while soil moisture played a secondary role. Potential improvements in characterizing SOC heterogeneity, including better spatial sampling of soil conditions and advances in remote sensing of SOC and soil moisture, will enable more accurate predictions of active layer conditions and refinement of the modeling framework across a larger domain.

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Section: Discussioncontrasting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: In Situ Datamentioning

confidence: 99%

mentioning

confidence: 99%

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Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Kimball

Chen

et al. 2018

The Cryosphere

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“…Due to global climate warming, significant efforts have been devoted to permafrost research, such as permafrost variations on the hemispheric-scale permafrost temperature changes (Wu and Zhang, 2008;Guglielmin and Cannone, 2012;Streletskiy et al, 2014;Wu et al, 2015), permafrost degradation (Jorgenson et al, 2006;Ravanel et al, 2010;Sannel and Kuhry, 2011;Streletskiy et al, 2015a;Park et al, 2016), hydrological processes in permafrost regions Wang et al, 2009;Park et al, 2013;Streletskiy et al, 2015b;Ford and Frauenfeld, 2016), feedbacks to climate change (Schuur et al, 2008;Park et al, 2015;Abbott et al, 2016), and other aspects. The increasing thickness of the active layer has been indicated by many observations in permafrost regions at high latitudes and altitudes (Brown et al, 2000;Frauenfeld et al, 2004;Zhang et al, 2005;Fyodorov-Davydov et al, 2008;Wu et al, 2010;Zhao et al, 2010;Callaghan et al, 2011;Liu et al, 2014a, b;Stocker et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Response of seasonal soil freeze depth to climate change across China

et al. 2017

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Abstract. The response of seasonal soil freeze depth to climate change has repercussions for the surface energy and water balance, ecosystems, the carbon cycle, and soil nutrient exchange. Despite its importance, the response of soil freeze depth to climate change is largely unknown. This study employs the Stefan solution and observations from 845 meteorological stations to investigate the response of variations in soil freeze depth to climate change across China. Observations include daily air temperatures, daily soil temperatures at various depths, mean monthly gridded air temperatures, and the normalized difference vegetation index. Results show that soil freeze depth decreased significantly at a rate of −0.18 ± 0.03 cm yr −1 , resulting in a net decrease of 8.05 ± 1.5 cm over 1967-2012 across China. On the regional scale, soil freeze depth decreases varied between 0.0 and 0.4 cm yr −1 in most parts of China during 1950-2009. By investigating potential climatic and environmental driving factors of soil freeze depth variability, we find that mean annual air temperature and ground surface temperature, air thawing index, ground surface thawing index, and vegetation growth are all negatively associated with soil freeze depth. Changes in snow depth are not correlated with soil freeze depth. Air and ground surface freezing indices are positively correlated with soil freeze depth. Comparing these potential driving factors of soil freeze depth, we find that freezing index and vegetation growth are more strongly correlated with soil freeze depth, while snow depth is not significant. We conclude that air temperature increases are responsible for the decrease in seasonal freeze depth. These results are important for understanding the soil freeze-thaw dynamics and the impacts of soil freeze depth on ecosystem and hydrological process.

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Tracer model-based quantitative separation of precipitation and permafrost waters used for evapotranspiration in a boreal forest

Park¹,

Tanoue²,

Ichiyanagi³

et al. 2021

Preprint

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Arctic precipitation (PG) that occurs as rainfall (Pr) or snowfall (Ps) depending on the prevailing climatic conditions results in seasonally specific hydrological events. Climate change can affect the PG-and permafrost-originated water (Pi) regimes, resulting in change to ecohydrological processes. However, the relative influences of source waters (i.e., Pr, Ps, and Pi) on terrestrial hydrological processes have not yet been fully established. Here, we report the development and implementation of a numerical water tracer model designed to quantify changes in the storages and fluxes of the source waters and the hydrogen and oxygen isotopic tracers associated with hydrometeorological events. The presented tracer model was used to illustrate the spatiotemporal variability of the tracers in the surface-subsurface system of a deciduous needleleaf boreal forest, and to separate the contribution rates of the tracer waters to evapotranspiration (ET). Although Ps accounted for 14%-40% of ET and the subcomponents, the contribution rates to soil evaporation and transpiration were significant only during the spring season. The major source water for soil moisture was Pr, which accounted for 80.1% of ET and showed an increasing trend. Additionally, Pr also accounted for 85.7% of transpiration. Under the present conditions of warming permafrost, Pi demonstrated negligibly low impact on ET. The tracer model was shown capable of quantifying the contribution rates of tracer waters to ET, highlighting the advantages of the tracer model for similar quantitative separation regarding future climate change.

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Widespread permafrost vulnerability and soil active layer increases over the high northern latitudes inferred from satellite remote sensing and process model assessments

Cited by 105 publications

References 52 publications

Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska

Response of seasonal soil freeze depth to climate change across China

Tracer model-based quantitative separation of precipitation and permafrost waters used for evapotranspiration in a boreal forest

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