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A finite element analysis of tunnel response to permafrost thaw
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2020
D. Vo, L. Chung, J.S. Cho, Y. Salem
Looking deeper into the characteristics of permafrost, when the pores of soil are saturated by unfrozen water the soil has a set volume. If the soil freezes the water expands and an extra volume of excess ice is present in the frozen soil. The National Snow & Ice Data Center (NSIDC) defines excess ice as “the volume of ice in the ground which exceeds the total pore volume that the ground would have under natural unfrozen conditions.” The process of excess ice thaw is called thermokarst. Thermokarst is problematic in that soil strength is reduced due to thawing of cementitious ice, and reductions in soil volume due to loss of excess ice. (Murton, 2009). As mentioned before, the process of thermokarst is expedited as arctic annual mean temperatures rise at a rate twice as fast as the rest of the planet.
A finite element analysis of tunnel response to permafrost thaw
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2019
D. Vo, L. Chung, J.S. Cho, Y. Salem
Looking deeper into the characteristics of permafrost, when the pores of soil are saturated by unfrozen water the soil has a set volume. If the soil freezes the water expands and an extra volume of excess ice is present in the frozen soil. The National Snow & Ice Data Center (NSIDC) defines excess ice as “the volume of ice in the ground which exceeds the total pore volume that the ground would have under natural unfrozen conditions.” The process of excess ice thaw is called thermokarst. Thermokarst is problematic in that soil strength is reduced due to thawing of cementitious ice, and reductions in soil volume due to loss of excess ice. (Murton, 2009). As mentioned before, the process of thermokarst is expedited as arctic annual mean temperatures rise at a rate twice as fast as the rest of the planet.
Morphogenetic landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
When the ground contains excess ice, thawing leads to subsidence which results in thermokarst. Perhaps the most common form is the thaw lake (Figure 18.30). These are circular or oval in shape, generally less than 1–2 km across and 3–4 m deep. Thaw lakes originate when an ice lens is exposed to the air and melts, often as a result of some chance factor, such as slumping of surface materials or stream migration. The lake quickly assumes an approximately circular form as it melts and undercuts the adjacent ice-rich permafrost. There is a cycle whereby the vegetation growth around the lake eventually protects the underlying ice from melting and the lake begins to be infilled and revegetates once more. Eventually the dried-out lake may be marked by the site of a pingo, as shown in Figure 18.28.
Limnology and diatom ecology of shallow lakes in a rapidly thawing discontinuous permafrost peatland
Published in Inland Waters, 2023
Kristen A. Coleman, Grace N. Hoskin, Laura Chasmer, Joshua R. Thienpont, William L. Quinton, Jennifer B. Korosi
Discontinuous permafrost landscapes are highly sensitive to even modest warming of air temperatures (Kettles and Tarnocai 1999, Spence et al. 2020). Models project that 40% of the world's permafrost could be lost by 2100 (SOCR 2021), with sporadic discontinuous permafrost regions potentially permafrost-free by mid-century (Chasmer and Hopkinson 2017). Permafrost thaw can manifest in different ways: it can change the thickness of the seasonally thawed (active) layer, generate a layer of talik separating the underlying permafrost from the overlying active layer, and produce thermokarst terrain (Zhang et al. 1999, 2005, Frey and McClelland 2009). While changes in active layer thickness occur slowly (press disturbance), thermokarst development from the thawing of ice-rich permafrost manifests as a rapid (or pulse) disturbance (Vonk et al. 2015). In southern permafrost peatlands, wetland thermokarst processes typically predominate, resulting in the conversion of forests to wetlands (Quinton et al. 2019).
The limnological response of Arctic deltaic lakes to alterations in flood regime
Published in Inland Waters, 2022
Ryan W. Scott, Sapna Sharma, Xiaowa Wang, Roberto Quinlan
The Mackenzie system is the largest Arctic drainage in North America, with a watershed area of 1.8 × 106 km2 that encompasses a large portion of northwestern Canada (Rosenberg and Barton 1986). The north-flowing Mackenzie River mainstem terminates at Point Separation, where the river divides into anastomosing channels that run through the Mackenzie Delta into the Beaufort Sea. Marine discharge from the delta is rich in nutrients, suspended sediment, and dissolved organic and inorganic compounds (Holmes et al. 2002, Emmerton et al. 2008, Graydon et al. 2009, Tank et al. 2016). Spring flooding with concurrent ice breakup is the major annual hydrological event in the Mackenzie Delta, typically commencing in mid-May and ending in early June (Marsh and Hey 1989). Nearly half of the discharge during this period is temporarily stored in the floodplain, where it mixes with lake water before ∼80% of this stored water is exported eventually to the Beaufort Sea as the flood recedes (Emmerton et al. 2007). The remaining water is stored on the delta floodplain in the form of ∼45 000 mainly small shallow lakes (Emmerton et al. 2007). These basins are formed by thermokarst processes in which standing water on top of permafrost increases the active layer depth, which leads to thaw subsidence of ice-rich permafrost and the formation of depressions that deepen into lake basins (Hill et al. 2001). The progressive deepening of lake basins from thermokarst activity combined with estimates of maximum ice cover thickness (0.6–1.2 m, depending on snow cover) suggest that the vast majority of the lakes are of sufficient depth to retain unfrozen water through the winter (Emmerton et al. 2007).
Integrating MODIS LST and Sentinel-1 InSAR to monitor frozen soil deformation in the Qumalai-Zhiduo area, Qinghai-Tibet Plateau
Published in International Journal of Digital Earth, 2023
Wenyan Yu, Mi Jiang, Xiao Cheng
P3, located along the Qinghai-Tibet highway, is characterized by many small thermokarst lakes, indicating that the underground is ice-rich and degraded. As shown in Figure 7(c), the area begins to freeze in early October and begins to melt in mid-March every year. The linear subsidence rate is approximately 0.6 cm/yr, and the seasonal deformation amplitude is about 2.9 cm, indicating the potential for strong thawing subsidence and frost heave, which may expose the highway. Besides, the RMSE shows that the results based on MODIS LST may performance better in areas far from the weather station.