Surface temperatures and their influence on the permafrost thermal regime in high-Arctic rock walls on Svalbard

Aga, Juditha; Etzelmüller, Bernd; Schuler, Thomas; Magnin, Florence; Boike, Julia; Langer, Moritz; Westermann, Sebastian

doi:10.5194/tc-15-2491-2021

Cited by 14 publications

(25 citation statements)

References 60 publications

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“…We use a onedimensional model column with a domain depth of 100 m (e.g. Westermann et al, 2016;Schmidt et al, 2021) and grid cell sizes increasing with depth (Fig. 2).…”

Section: The Cryogrid Community Modelmentioning

confidence: 99%

“…The CryoGrid community model (Westermann et al, 2022) is a simulation toolbox that can calculate ground temperatures and water/ice contents in permafrost environments. It largely builds on the well-established CryoGrid 3 model (Westermann et al, 2016), which has been used in, for example, peat plateaus and palsas (Martin et al, 2021), ice-wedge polygons (Nitzbon et al, 2019) and boreal forests (Stuenzi et al, 2021), and has a broad range of applications, including the representation of lateral drainage regimes (Martin et al, 2019), steep rock walls (Schmidt et al, 2021) and massive ice bodies. In the following, the CryoGrid community model is referred to as "CryoGrid" for simplicity.…”

Section: Introductionmentioning

confidence: 99%

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Simulating the effect of subsurface drainage on the thermal regime and ground ice in blocky terrain in Norway

Renette

Aalstad²,

Aga³

et al. 2023

Earth Surf. Dynam.

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Abstract. Ground temperatures in coarse, blocky deposits such as mountain blockfields and rock glaciers have long been observed to be lower in comparison with other (sub)surface material. One of the reasons for this negative temperature anomaly is the lower soil moisture content in blocky terrain, which decreases the duration of the zero curtain in autumn. Here we used the CryoGrid community model to simulate the effect of drainage on the ground thermal regime and ground ice in blocky terrain permafrost at two sites in Norway. The model set-up is based on a one-dimensional model domain and features a surface energy balance, heat conduction and advection, as well as a bucket water scheme with adjustable lateral drainage. We used three idealized subsurface stratigraphies, blocks only, blocks with sediment and sediment only, which can be either drained (i.e. with strong lateral subsurface drainage) or undrained (i.e. without drainage), resulting in six scenarios. The main difference between the three stratigraphies is their ability to retain water against drainage: while the blocks only stratigraphy can only hold small amounts of water, much more water is retained within the sediment phase of the two other stratigraphies, which critically modifies the freeze–thaw behaviour. The simulation results show markedly lower ground temperatures in the blocks only, drained scenario compared to other scenarios, with a negative thermal anomaly of up to 2.2 ∘C. For this scenario, the model can in particular simulate the time evolution of ground ice, with build-up during and after snowmelt and spring and gradual lowering of the ice table in the course of the summer season. The thermal anomaly increases with larger amounts of snowfall, showing that well-drained blocky deposits are less sensitive to insulation by snow than other soils. We simulate stable permafrost conditions at the location of a rock glacier in northern Norway with a mean annual ground surface temperature of 2.0–2.5 ∘C in the blocks only, drained simulations. Finally, transient simulations since 1951 at the rock glacier site (starting with permafrost conditions for all stratigraphies) showed a complete loss of perennial ground ice in the upper 5 m of the ground in the blocks with sediment, drained run; a 1.6 m lowering of the ground ice table in the sediment only, drained run; and only 0.1 m lowering in the blocks only, drained run. The interplay between the subsurface water–ice balance and ground freezing/thawing driven by heat conduction can at least partly explain the occurrence of permafrost in coarse blocky terrain below the elevational limit of permafrost in non-blocky sediments. It is thus important to consider the subsurface water–ice balance in blocky terrain in future efforts in permafrost distribution mapping in mountainous areas. Furthermore, an accurate prediction of the evolution of the ground ice table in a future climate can have implications for slope stability, as well as water resources in arid environments.

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“…We use a onedimensional model column with a domain depth of 100 m (e.g. Westermann et al, 2016;Schmidt et al, 2021) and grid cell sizes increasing with depth (Fig. 2).…”

Section: The Cryogrid Community Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulating the effect of subsurface drainage on the thermal regime and ground ice in blocky terrain in Norway

Renette

Aalstad²,

Aga³

et al. 2023

Earth Surf. Dynam.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Its modular structure makes it suitable for a wide range of terrestrial cryosphere settings and is mainly applied in permafrost environments (Westermann et al, 2022). Previous studies successfully used former CryoGrid models to simulate processes in steep rock walls and mountainous regions (Magnin et al, 2017;Myhra et al, 2017;Schmidt et al, 2021;Legay et al, 2021). We used the CryoGrid community model (version 1.0) toolbox (Westermann et al, 2022) to simulate the 1D ground thermal regime and ice/water balance, and estimate the availability of surface water and its potential for infiltration in rock fractures.…”

Section: Model Setupmentioning

confidence: 99%

Estimating surface water availability in high mountain rock slopes using a numerical energy balance model

Ben-Asher

Magnin

Westermann

et al. 2022

Preprint

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Abstract. Water takes part in most physical processes that shape the mountainous periglacial landscapes and initiation of mass wasting. An observed increase in rockfall activity in several mountainous regions was previously linked to permafrost degradation in high mountains, and water that infiltrates into rock fractures is one of the likely drivers of these processes. However, there is very little knowledge on the quantity and timing of water availability for infiltration in steep rock slopes. This knowledge gap originates from the complex meteorological, hydrological and thermal processes that control snowmelt, and also the challenging access and data acquisition in the extreme alpine environments. Here we use field measurement and numerical modeling to simulate the energy balance and hydrological fluxes in a steep high elevation permafrost affected rock slope at Aiguille du Midi (3842 m a.s.l), in the Mont-Blanc massif. Our results provide new information about water balance at the surface of steep rock slopes. Model results suggest that only ~25 % of the snowfall accumulates in our study site, the remaining ~75 % are redistributed by wind and gravity. Snow accumulation depth is inversely correlated with surface slopes between 40° to 70°. Snowmelt occurs between spring and late summer and most of it does not reach the rock surface due to the formation of an impermeable ice layer at the base of the snowpack. The annual effective snowmelt, that is available for infiltration, is highly variable and ranges over a factor of six with values between 0.05–0.28 m in the years 1959–2021. The onset of the effective snowmelt occurs between May and August, and ends before October. It precedes the first rainfall by one month on average. Sublimation is the main process of snowpack mass loss in our study site. Model simulations at varying elevations show that effective snowmelt is the main source of water for infiltration above 3600 m a.s.l.; below, direct rainfall is the dominant source. The change from snowmelt-dominated to rainfall-dominated water availability is nonlinear and characterized by a rapid increase in water availability for infiltration. We suggest that this elevation of water availability transition is highly sensitive to climate change, if snowmelt-dominated permafrost-affected slopes experience an abrupt increase in water input that can initiate rock slope failure.

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“…Measurements show ground temperatures of -3.0 to -2.6 °C in a depth of 9 m between 2009 and 2016 (GTN-P, 2018) and thus relatively warm permafrost. We use the same model forcing asSchmidt et al (2021) for the presented long-term runs in that study. Between 1980 and 2019, the model forcing is derived from ERA-Interim reanalysis, while the future forcing is based on CMIP5 projections (RCP 8.5) of CCSM4 using an anomaly approach.…”

mentioning

confidence: 99%

“…Between 1980 and 2019, the model forcing is derived from ERA-Interim reanalysis, while the future forcing is based on CMIP5 projections (RCP 8.5) of CCSM4 using an anomaly approach. For a detailed description of the forcing data set seeSchmidt et al (2021). Validation performed byWestermann et al (2022) shows that CryoGrid can capture the ground temperatures at the Bayelva site well.https://doi.org/10.5194/egusphere-2023-41 Preprint.…”

mentioning

confidence: 99%

Simulating ice segregation and thaw consolidation in permafrost environments with the CryoGrid community model

Aga

Boike

Langer

et al. 2023

Preprint

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Abstract. The ground ice content in cold environments influences the permafrost thermal regime and the thaw trajectories in a warming climate, especially for very ice-rich soils. Despite their importance, the amount and distribution of ground ice are often unknown due to lacking field observations. Hence, modelling the thawing of ice-rich permafrost soils and associated thermokarst is challenging as ground ice content has to be prescribed in the model set-up. In this study, we present a model scheme, which is capable of forming segregated ice during a model spin-up together with associated ground heave. It provides the option to add a constant sedimentation rate throughout the simulation. Besides ice segregation, it can represent thaw consolidation processes and ground subsidence under a warming climate. The computation is based on soil mechanical processes, soil hydrology by Richards equation and soil freezing characteristics. The code is implemented in the CryoGrid community model (version 1.0), a modular land surface model for simulations of the ground thermal regime. The simulation of ice segregation and thaw consolidation with the new model scheme allows us to analyze the evolution of ground ice content in both space and time. To do so, we use climate data from two contrasting permafrost sites to run the simulations. Several influencing factors are identified, which control the formation and thaw of segregated ice. (i) Model results show that high temperature gradients in the soil as well as moist conditions support the formation of segregated ice. (ii) We find that ice segregation increases in fine-grained soils and that especially organic-rich sediments enhance the process. (iii) Applying external loads suppresses ice segregation and speeds up thaw consolidation. (iv) Sedimentation leads to a rise of the ground surface and the formation of an ice-enriched layer whose thickness increases with sedimentation time. We conclude that the new model scheme is a step forward to improve the description of ground ice distributions in permafrost models and can contribute towards the understanding of ice segregation and thaw consolidation in permafrost environments under changing climatic conditions.

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Surface temperatures and their influence on the permafrost thermal regime in high-Arctic rock walls on Svalbard

Cited by 14 publications

References 60 publications

Simulating the effect of subsurface drainage on the thermal regime and ground ice in blocky terrain in Norway

Simulating the effect of subsurface drainage on the thermal regime and ground ice in blocky terrain in Norway

Estimating surface water availability in high mountain rock slopes using a numerical energy balance model

Simulating ice segregation and thaw consolidation in permafrost environments with the CryoGrid community model

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