robinbz

Zweigel, Robin Benjamin. A physically based approach to simulate sub-grid snow depth and ground surface temperature distribution. Master thesis, University of Oslo, 2020

• Zweigel, Robin Benjamin; Dashtseren, Avirmed; Temuujin, Khurelbaatar; Sharkhuu, Anarmaa; Webster, Clare & Lee, Hanna [Show all 7 contributors for this article] (2024). Impact of livestock activity on near-surface ground temperatures in central Mongolian grasslands. Biogeosciences. ISSN 1726-4170. 21(22), p. 5059–5077. doi: 10.5194/bg-21-5059-2024. Full text in Research Archive Show summary

  Grazing by livestock can alter the surface conditions at grassland sites, impacting the transfer of energy between the atmosphere and ground and consequentially ground temperatures. In this study, we investigate surface cover in summer and winter and measure ground surface temperatures over 14 months at sites in central Mongolia that feature different grazing intensities (intensely and ungrazed) and topographic aspects (north- and south-facing). Overall, intense grazing leads to a substantially reduced vegetation cover, altered snow conditions, and lack of surface litter accumulation. Comparing intensely grazed and ungrazed plots shows large seasonal differences in ground surface temperatures, with grazed plots being up to +5.1 °C warmer in summer and −5.4 °C colder in winter at a south-facing site. We also find that the effect of grazing intensity depends on topographic aspect, with smaller seasonal differences of +1.4 °C and −2.5 °C found between grazed and ungrazed plots at a north-facing site. This relates to the lower available solar radiation at north-facing sites, which reduces the differences in vegetation cover between open and fenced plots. For both aspects, the seasonal differences largely offset each other, with both a small net cooling and warming depending on effects in spring and autumn. Our study suggests that livestock management could be used to modify the annual ground temperature dynamics, possibly even influencing local permafrost dynamics.

• Zweigel, Robin Benjamin; Dashtseren, Avirmed; Temuujin, Khurelbaatar; Aalstad, Kristoffer; Webster, Clare & Stuenzi, Simone M. [Show all 9 contributors for this article] (2024). Simulating the Thermal Regime and Surface Energy Balance of a Permafrost-Underlain Forest in Mongolia. Journal of Geophysical Research (JGR): Earth Surface. ISSN 2169-9003. 129(6). doi: 10.1029/2023JF007609. Full text in Research Archive Show summary

  Forests overlap with large parts of the northern hemisphere permafrost area, and representing canopy processes is therefore crucial for simulating thermal and hydrological conditions in these regions. Forests impact permafrost through the modulation of radiative fluxes and exchange of turbulent fluxes, precipitation interception and regulation of transpiration. Forests also feature distinct soil layers of litter and organic matter, which play central roles for the infiltration and evaporation of water, while also providing thermal insulation for deeper ground layers. In this study, we present a new module within the CryoGrid community model to simulate forest ecosystems and their impact on the surface water and energy balance. The module includes a big-leaf vegetation scheme with adaptations for canopy heat storage and transpiration. Furthermore, we account for the effect of surface litter layers on water and energy transfer. We show that the model is capable of simulating radiation, snow cover and ground temperatures below a deciduous needleleaf forest on a north-facing slope in the Khentii Mountains in Central Mongolia. A sensitivity analysis of topographic aspect and ecosystem configuration confirms the important role of the litter layers for the energy and water balance of the ground. Furthermore, it suggests that the presence of permafrost is primarily linked to topographic aspect rather than the presence of forest at this site. The presented model scheme can be used to study the development of the ground thermal regime in forests, including the state of permafrost, under different climate, ecosystem, and land use scenarios.

• Renette, Cas; Aalstad, Kristoffer; Aga, Juditha; Zweigel, Robin Benjamin; Etzelmüller, Bernd & Lilleøren, Karianne Staalesen [Show all 8 contributors for this article] (2023). Simulating the effect of subsurface drainage on the thermal regime and ground ice in blocky terrain in Norway. Earth Surface Dynamics. ISSN 2196-6311. 11(1), p. 33–50. doi: 10.5194/esurf-11-33-2023. Full text in Research Archive Show summary

  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.

• Westermann, Sebastian; Ingeman-Nielsen, Thomas; Scheer, Johanna; Aalstad, Kristoffer; Aga, Juditha & Chaudhary, Nitin [Show all 24 contributors for this article] (2023). The CryoGrid community model (version 1.0) - a multi-physics toolbox for climate-driven simulations in the terrestrial cryosphere. Geoscientific Model Development. ISSN 1991-959X. 16(9), p. 2607–2647. doi: 10.5194/gmd-16-2607-2023. Full text in Research Archive Show summary

  The CryoGrid community model is a flexible toolbox for simulating the ground thermal regime and the ice–water balance for permafrost and glaciers, extending a well-established suite of permafrost models (CryoGrid 1, 2, and 3). The CryoGrid community model can accommodate a wide variety of application scenarios, which is achieved by fully modular structures through object-oriented programming. Different model components, characterized by their process representations and parameterizations, are realized as classes (i.e., objects) in CryoGrid. Standardized communication protocols between these classes ensure that they can be stacked vertically. For example, the CryoGrid community model features several classes with different complexity for the seasonal snow cover, which can be flexibly combined with a range of classes representing subsurface materials, each with their own set of process representations (e.g., soil with and without water balance, glacier ice). We present the CryoGrid architecture as well as the model physics and defining equations for the different model classes, focusing on one-dimensional model configurations which can also interact with external heat and water reservoirs. We illustrate the wide variety of simulation capabilities for a site on Svalbard, with point-scale permafrost simulations using, e.g., different soil freezing characteristics, drainage regimes, and snow representations, as well as simulations for glacier mass balance and a shallow water body. The CryoGrid community model is not intended as a static model framework but aims to provide developers with a flexible platform for efficient model development. In this study, we document both basic and advanced model functionalities to provide a baseline for the future development of novel cryosphere models.

• Zweigel, Robin Benjamin; Westermann, Sebastian; Nitzbon, Jan; Langer, M; Boike, Julia & Etzelmüller, Bernd [Show all 7 contributors for this article] (2021). Simulating Snow Redistribution and its Effect on Ground Surface Temperature at a High‐Arctic Site on Svalbard. Journal of Geophysical Research (JGR): Earth Surface. ISSN 2169-9003. 126(3). doi: 10.1029/2020JF005673. Full text in Research Archive Show summary

  In high-latitude and mountain regions, local processes such as redistribution by wind, snow metamorphism, and percolation of water produce a complex spatial distribution of snow depths and snow densities. With its strong control on the ground thermal regime, this snow distribution has pronounced effects on ground temperatures at small spatial scales which are typically not resolved by land surface models (LSMs). This limits our ability to simulate the local impacts of climate change on, for example, vegetation and permafrost. Here, we present a tiling approach combining the CryoGrid permafrost model with snow microphysics parametrizations from the CROCUS snow scheme to account for subgrid lateral exchange of snow and water in a process-based way. We demonstrate that a simple setup with three coupled tiles, each representing a different snow accumulation class with a specific topographic setting, can reproduce the observed spread of winter-time ground surface temperatures (GST) and end-of-season snow distribution for a high-Arctic site on Svalbard. For the 3-year study period, the three-tile simulations showed substantial improvement compared to traditional single-tile simulations which naturally cannot account for subgrid variability. Among others, the representation of the warmest and coldest 5% of the observed GST distribution was improved by 1–2°C, while still capturing the average of the distribution. The simulations also reveal positive mean annual GSTs at the locations receiving the greatest snow cover. This could be an indication for the onset of localized permafrost degradation which would be obscured in single-tile simulations.

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• Zweigel, Robin Benjamin; Westermann, Sebastian; Lee, Hanna & Webster, Clare (2025). Ecosystem disturbances and their impact on ground temperatures – examples from central Mongolia. Full text in Research Archive
• Zweigel, Robin Benjamin; Dashtseren, Avirmed; Temuujin, Khurelbaatar; Sharkhuu, Anarmaa; Webster, Clare & Lee, Hanna [Show all 7 contributors for this article] (2025). Disturbance by livestock impacts ground temperatures in marginal permafrost areas in Central Mongolia. doi: 10.5194/egusphere-egu25-17283. Full text in Research Archive Show summary

  In the Central Mongolian mountains, the presence of permafrost is intimately linked to local topography and ecosystem setting. Permafrost in these areas is generally found on north-facing slopes, and it is an important element of the hydrological regime, contributing to water availability and downstream ecosystem function. Currently, these linked systems are under increased pressure from both intensified land use and climate warming. This includes disturbances from herd animals, who modify the surface energy balance at grassland sites by changing vegetation structure in summer and snow cover in winter. However, the effect of livestock grazing and trampling on the ground thermal regime in these marginal permafrost areas is largely unknown. In this study, we investigate how semi-nomadic pastoralism impacts surface cover and associated ground temperatures at grassland sites in Central Mongolia. We survey vegetation and snow cover in summer and winter and monitor ground surface temperatures (GSTs) over 14 months at plots featuring different grazing intensities (intensely and ungrazed), as well as topographic aspects (north- and south-facing). We find that plots subject to intense grazing feature lower vegetation density and height, reduced snow cover and an absence of surface litter layers. Overall, intensely grazed plots display an intensified annual cycle of GSTs compared to ungrazed plots, with GSTs at a south-facing site up to +5.1°C warmer in summer and up to -5.4°C colder in winter. We further find the impact of grazing on GST to depend on topographic aspect, and at a north-facing site we observe lower seasonal differences in GST of +1.4°C and -2.5°C between grazed and ungrazed plots. At our study sites the seasonal differences in GST largely cancel each other out, with the net effect depending on spring and autumn conditions. These results suggest that surface conditions at grassland sites can be managed by regulating the disturbances caused by livestock, which in turn can modify the ground thermal dynamics. For example, a cooling of ground temperatures can possibly be achieved through shielding areas from grazing during the growing season while allowing or even promoting grazing and trampling in the snow season. Such livestock management could potentially offset current and future surface warming in marginal permafrost areas, contributing to sustained local water availability and ecosystem function.

• Webster, Clare; Girod, Luc; Treichler, Desiree Silvana; Zweigel, Robin Benjamin & Westermann, Sebastian (2025). Measuring boreal forest and snow cover with UAV-lidar. Full text in Research Archive
• Zweigel, Robin Benjamin; Lee, Hanna; Debolskiy, Matvey & Westermann, Sebastian (2023). Simulating forest cover and terrain effects on ground hydrothermal regime in Mongolia and Siberia. Full text in Research Archive
• Zweigel, Robin Benjamin; Westermann, Sebastian; Lee, Hanna & Debolskiy, Matvey (2023). Simulating forest impact on ground thermal regime using the CryoGrid Community model – examples from Terelj, Mongolia. Full text in Research Archive
• Zweigel, Robin Benjamin (2026). Ecosystem controls on ground temperatures in Mongolia. Field observations and numerical modelling. Universitetet i Oslo. Full text in Research Archive Show summary

  In Mongolia’s forest-steppe, with an average height of 1500 meters above sea level, permafrost and forests exist close to their climatic limits, and changes in vegetation cover – such as livestock grazing by and forest loss - are putting fragile ecosystems under additional pressure. This doctoral work by Robin B. Zweigel show that when forests die back or grasslands are heavily grazed, the loss of vegetation and changes in snow cover impacts how heat and water moves between the air and the ground, ultimately altering ground temperatures and local water cycle. To improve the understanding of these relationships, the thesis incorporated vegetation and terrain effects into a permafrost model, which showed that north-facing slopes are more resilient to permafrost loss, but that removing vegetation or organic layers increases ground temperatures in summer and leads to a deepening of the active layer. The findings in this doctoral work highlight how land use and ecosystem changes directly affect ground thermal conditions and ultimately permafrost stability. It also provides new tools that can help design sustainable land management that protects both ecosystems and traditional livelihoods in Mongolia and similar cold regions.

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