Performance, applicability, and optimization of a new slope cooling and protection structure for road embankment over warm permafrost

2020 ◽  
Vol 162 ◽  
pp. 120388
Author(s):  
Minghao Liu ◽  
Fujun Niu ◽  
Jing Luo ◽  
Guoan Yin ◽  
Liang Zhang
Keyword(s):  
Warm Permafrost

Equilibrium Spin-up of Cold and Warm Permafrost Models

2021 ◽  
Author(s):  
Cameron Ross ◽  
Ryley Beddoe ◽  
Greg Siemens
Keyword(s):  
Climate Change ◽  
Temperature Response ◽  
Ground Temperature ◽  
Future Climate Change ◽  
Climate Projections ◽  
Multiple Model ◽  
Climate Data ◽  
Ground Temperatures ◽  
C Cycle ◽  
Warm Permafrost

<p>Initialization (spin-up) of a numerical ground temperature model is a critical but often neglected step for solving heat transfer problems in permafrost. Improper initialization can lead to significant underlying model drift in subsequent transient simulations, distorting the effects on ground temperature from future climate change or applied infrastructure.  In a typical spin-up simulation, a year or more of climate data are applied at the surface and cycled repeatedly until ground temperatures are declared to be at equilibrium with the imposed boundary conditions, and independent of the starting conditions.</p><p>Spin-up equilibrium is often simply declared after a specified number of spin-up cycles. In few studies, equilibrium is visually confirmed by plotting ground temperatures vs spin-up cycles until temperatures stabilize; or is declared when a certain inter-cycle-temperature-change threshold is met simultaneously at all depths, such as ∆T ≤ 0.01<sup>o</sup>C per cycle. In this study, we investigate the effectiveness of these methods for determining an equilibrium state in a variety of permafrost models, including shallow and deep (10 – 200 m), high and low saturation soils (S = 100 and S = 20), and cold and warm permafrost (MAGT = ~-10 <sup>o</sup>C and >-1 <sup>o</sup>C). The efficacy of equilibrium criteria 0.01<sup>o</sup>C/cycle and 0.0001<sup>o</sup>C/cycle are compared. Both methods are shown to prematurely indicate equilibrium in multiple model scenarios.  Results show that no single criterion can programmatically detect equilibrium in all tested models, and in some scenarios can result in up to 10<sup>o</sup>C temperature error or 80% less permafrost than at true equilibrium.  A combination of equilibrium criteria and visual confirmation plots is recommended for evaluating and declaring equilibrium in a spin-up simulation.</p><p>Long-duration spin-up is particularly important for deep (10+ m) ground models where thermal inertia of underlying permafrost slows the ground temperature response to surface forcing, often requiring hundreds or even thousands of spin-up cycles to establish equilibrium. Subsequent transient analyses also show that use of a properly initialized 100 m permafrost model can reduce the effect of climate change on mean annual ground temperature of cold permafrost by more than 1 <sup>o</sup>C and 3 <sup>o</sup>C under RCP2.6 and RCP8.5 climate projections, respectively, when compared to an identical 25 m model. These results have important implications for scientists, engineers and policy makers that rely on model projections of long-term permafrost conditions.</p>

The Deformation Properties of Warm Permafrost

2008 ◽  
pp. 473-473-14 ◽  
Author(s):  
DH Shields ◽  
L Domaschuk ◽  
C-S Man ◽  
RM Kenyon
Keyword(s):  
Deformation Properties ◽  
Warm Permafrost

scholarly journals Ground subsidence and heave over permafrost: hourly time series reveal interannual, seasonal and shorter-term movement caused by freezing, thawing and water movement

2020 ◽  
Vol 14 (4) ◽  
pp. 1437-1447 ◽  
Author(s):  
Stephan Gruber
Keyword(s):  
Water Movement ◽  
Ground Surface ◽  
Ground Subsidence ◽  
Late Winter ◽  
Remotely Sensed Data ◽  
Freezing And Thawing ◽  
Frozen Ground ◽  
Process Understanding ◽  
Winter Peak ◽  
Warm Permafrost

Abstract. Heave and subsidence of the ground surface can offer insight into processes of heat and mass transfer in freezing and thawing soils. Additionally, subsidence is an important metric for monitoring and understanding the transformation of permafrost landscapes under climate change. Corresponding ground observations, however, are sparse and episodic. A simple tilt-arm apparatus with logging inclinometer has been developed to measure heave and subsidence of the ground surface with hourly resolution and millimeter accuracy. This contribution reports data from the first two winters and the first full summer, measured at three sites with contrasting organic and frost-susceptible soils in warm permafrost. The patterns of surface movement differ significantly between sites and from a prediction based on the Stefan equation and observed ground temperature. The data are rich in features of heave and subsidence that are several days to several weeks long and that may help elucidate processes in the ground. For example, late-winter heave followed by thawing and subsidence, as reported in earlier literature and hypothesized to be caused by infiltration and refreezing of water into permeable frozen ground, has been detected. An early-winter peak in heave, followed by brief subsidence, is discernible in a previous publication but so far has not been interpreted. An effect of precipitation on changes in surface elevation can be inferred with confidence. These results highlight the potential of ground-based observation of subsidence and heave as an enabler of progress in process understanding, modeling and interpretation of remotely sensed data.

scholarly journals Detecting the permafrost carbon feedback: Talik formation and increased cold-season respiration as precursors to sink-to-source transitions

2017 ◽  
Author(s):  
Nicholas C. Parazoo ◽  
Charles D. Koven ◽  
David M. Lawrence ◽  
Vladimir Romanovsky ◽  
Charles E. Miller
Keyword(s):  
Cold Season ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Borehole Data ◽  
Deep Soil ◽  
Organic C ◽  
Soil C ◽  
Community Land Model ◽  
Warm Permafrost

Abstract. Thaw and release of permafrost carbon (C) due to climate change is likely to offset increased vegetation C uptake in Northern High Latitude (NHL) terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a sub-surface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM) version 4.5, a permafrost and biogeochemistry model, in comparison to long term deep borehole data along North American and Siberian transects, to investigate thaw driven C sources in NHL (> 55° N) from 2000–2300. Widespread talik at depth IS projected across most of the NHL permafrost region (14 million km2) by 2300, correlated to increased cold season warming, earlier spring thaw, and growing active layers. Talik formation peaks in the 2050s in warm permafrost regions in the sub-Arctic. Comparison to borehole data suggests talik formation may even occur sooner. Accelerated decomposition of deep soil C following talik onset shifts the surface balance of photosynthetic uptake and litter respiration into long-term C sources across 3.2 million km2 of permafrost. Talik driven sources occur predominantly in warm permafrost, but sink-to-source transition dates are delayed by decades to centuries due to high ecosystem productivity. In contrast, most of the cold permafrost region in the northern Arctic (3 million km2) shifts to a net source by the end of the 21st century in the absence of talik due to the high decomposition rates of shallow, young C in organic rich soils coupled with low productivity. Our results provide important clues signaling imminent talik onset and C source transition including: (1) late cold season (Jan–Feb) soil warming at depth (~ 2 m), (2) increasing cold season emissions (Nov–Apr), (3) enhanced respiration of deep, old C in warm permafrost and young, shallow C in organic rich cold permafrost soils. Our results suggest a mosaic of processes that govern carbon source-to-sink transitions at high latitudes, and emphasize the urgency of monitoring soil thermal profiles, organic C age and content, cold season CO2 emissions, and atmospheric 14CO2 as key indicators of the permafrost C feedback.

scholarly journals Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai–Tibet Plateau

2018 ◽  
Vol 12 (2) ◽  
pp. 595-608 ◽  
Author(s):  
Youhua Ran ◽  
Xin Li ◽  
Guodong Cheng
Keyword(s):  
Thermal Degradation ◽  
Thermal Condition ◽  
Tibet Plateau ◽  
Half Century ◽  
The Past ◽  
Past Half Century ◽  
Warm Permafrost ◽  
Thawing Permafrost ◽  
The 1960S ◽  
Past Half

Abstract. Air temperature increases thermally degrade permafrost, which has widespread impacts on engineering design, resource development, and environmental protection in cold regions. This study evaluates the potential thermal degradation of permafrost over the Qinghai–Tibet Plateau (QTP) from the 1960s to the 2000s using estimated decadal mean annual air temperatures (MAATs) by integrating remote-sensing-based estimates of mean annual land surface temperatures (MASTs), leaf area index (LAI) and fractional snow cover values, and decadal mean MAAT date from 152 weather stations with a geographically weighted regression (GWR). The results reflect a continuous rise of approximately 0.04 ∘C a−1 in the decadal mean MAAT values over the past half century. A thermal-condition classification matrix is used to convert modelled MAATs to permafrost thermal type. Results show that the climate warming has led to a thermal degradation of permafrost in the past half century. The total area of thermally degraded permafrost is approximately 153.76×104 km2, which corresponds to 88 % of the permafrost area in the 1960s. The thermal condition of 75.2 % of the very cold permafrost, 89.6 % of the cold permafrost, 90.3 % of the cool permafrost, 92.3 % of the warm permafrost, and 32.8 % of the very warm permafrost has been degraded to lower levels of thermal condition. Approximately 49.4 % of the very warm permafrost and 96 % of the likely thawing permafrost has degraded to seasonally frozen ground. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88, 97, 155, 185, 161, and 250 m, respectively. The degradation mainly occurred from the 1960s to the 1970s and from the 1990s to the 2000s. This degradation may lead to increased risks to infrastructure, reductions in ecosystem resilience, increased flood risks, and positive climate feedback effects. It therefore affects the well-being of millions of people and sustainable development at the Third Pole.

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