Project

HiPerBorea: High Performance computing for quantifying climate change impacts on Boreal Areas (ANR funded project ANR-19-CE46-0003-01)

Goal: The objective of this project is to enable quantitative and predictive modeling of cold regions hydrosystems evolution under climate change. Arctic and sub-arctic areas, which are highly vulnerable to global warming, are largely covered by permafrost – soil that is year-round frozen at depth. Permafrost-affected areas, which represent 25% of emerged lands of the northern hemisphere, are prone to major biogeochemical and ecological transformations due to permafrost thaw, with strong associated feed-backs on greenhouse gas cycling (degradation of previously permanently frozen organic carbon pools). We will use advanced numerical modelling build on the permaFoam solver (the OpenFOAM solver for permafrost modelling, see Orgogozo et al., 2019) to help predict the impact of permafrost thaw on arctic thermo-hydrologic functioning. By doing so, we will provide mechanistic understanding of Arctic change, that is necessary to further understand carbon cycling and contaminant/nutrient transport, and to further assess risk and opportunity for sustainable urbanization, agriculture and general sustainable development of the (sub-)Arctic.

Orgogozo L., Prokushkin A.S., Pokrovsky O.S., Grenier C., Quintard M., Viers J., Audry S., 2019. Water and energy transfer modelling in a permafrost-dominated, forested catchment of Central Siberia: the key role of rooting depth. Permafrost and Periglacial Processes 30 : 75-89.
https://hal.archives-ouvertes.fr/hal-02014619

Methods: OpenFOAM, Massively Parallel Computation, INTERACT network of boreal stations for environmental monitoring

Date: 1 January 2020 - 31 December 2023

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Simon Cazaurang
added a research item
Due to its insulating and draining role, assessing ground vegetation cover properties is important for high-resolution hydrological modeling of permafrost regions. In this study, morphological and effective hydraulic properties of Western Siberian Lowland ground vegetation samples (lichens, Sphagnum mosses, peat) are numerically studied based on tomography scans. Porosity is estimated through a void voxels counting algorithm, showing the existence of representative elementary volumes (REVs) of porosity for most samples. Then, two methods are used to estimate hydraulic conductivity depending on the sample's homogeneity. For homogeneous samples, direct numerical simulations of a single-phase flow are performed, leading to a definition of hydraulic conductivity related to a REV, which is larger than those obtained for porosity. For heterogeneous samples, no adequate REV may be defined. To bypass this issue, a pore network representation is created from computerized scans. Morphological and hydraulic properties are then estimated through this simplified representation. Both methods converged on similar results for porosity. Some discrepancies are observed for a specific surface area. Hydraulic conductivity fluctuates by 2 orders of magnitude, depending on the method used. Porosity values are in line with previous values found in the literature, showing that arctic cryptogamic cover can be considered an open and well-connected porous medium (over 99 % of overall porosity is open porosity). Meanwhile, digitally estimated hydraulic conductivity is higher compared to previously obtained results based on field and laboratory experiments. However, the uncertainty is less than in experimental studies available in the literature. Therefore, biological and sampling artifacts are predominant over numerical biases. This could be related to compressibility effects occurring during field or laboratory measurements. These numerical methods lay a solid foundation for interpreting the homogeneity of any type of sample and processing some quantitative properties' assessment, either with image processing or with a pore network model. The main observed limitation is the input data quality (e.g., the tomographic scans' resolution) and its pre-processing scheme. Thus, some supplementary studies are compulsory for assessing syn-sampling and syn-measurement perturbations in experimentally estimated, effective hydraulic properties of such a biological porous medium.
Laurent Orgogozo
added a research item
Permafrost, i.e., soil that is year-round frozen in depth, is covering a quarter of the northern hemisphere lands, and most of it is located in Asia (Siberia, Himalaya). It currently experiences fast changes due to climate change at global scale and technogenic perturbations at local scale, and the assessment and anticipation of these changes are of primary importance for many environmental and engineering applications in cold regions[1],[2]. To these ends, permafrost modeling is required. It implies the numerical simulation of coupled heat and water transfers in variably saturated porous media experiencing freeze/thaw of the pore water. The strong couplings and non-linearities involved in the physics at stake make such simulations highly challenging, especially from a computational point of view, and thus the use of High Performance Computing is needed. This communication aims to illustrate these challenges by considering applications of a recently developed OpenFOAM® solver for cryohydrogeology, permaFoam[3],[4]. Developing permaFoam in the OpenFOAM framework allows to benefit from up to date, continuously maintained parallel computing capabilities[5],[6],[7]. Currently permaFoam is developed and used in the framework of HiPerBorea[8], a research project dealing with the assessment of climate change impacts on permafrost on boreal continental surfaces. It focuses on the numerical simulation of heat and water fluxes within four boreal catchments under long term environmental monitoring[9], and which spans a large longitudinal gradient in Eurasia, from Scandinavia to Eastern Siberia. Using permaFoam, HiPerBorea aims to produce simulations of responses of the permafrost of these watersheds for various scenarios of climate change until 2100. Such simulations imply the use of large computational resources, and are performed on tier-0 supercomputers[10]. Thanks to its good parallel performances, permaFoam allows using efficiently such HPC facilities. For the on-going academic year the HiPerBorea project has been granted 7 millions of CPU hours on the supercomputer IRENE of the TGCC.In order to illustrate the capabilities of permaFoam, two examples of applications to permafrost modeling in Siberian watersheds are presented. Kulingdakan watershed is a permafrost-dominated, forest covered watershed of Central Siberia for which the effect of evapotranspiration of active layer dynamics has been previously numerically studied[3]. The Syrdakh study site is a flood plain in an alas dominated area close to Yakutsk, Eastern Siberia, on which hydrological monitoring and studies have been on-going for nearly 10 years[11]. Both of these sites are currently under investigation in the framework of the HiPerBorea project. First simulation results are presented, and the challenges encountered on the way to century time scale permafrost modeling in these sites are discussed, in terms of model conditioning, computational load to be handled and pre- and post-processing practices. Keyword: heat transfer, water transfer, porous media, high performance computing, permafrost, climate change, Siberia. REFERENCES [1] H. Park, A.N. Fedorov, P. Konstantinov, T. Hiyama. Front. Earth Sci. 9, 704447 (2021). [2] J. Hjort, D. Streletskiy, G. Doré, Q. Wu, K. Bjella, M. Luoto. Nature Reviews Earth & Environment, 3, pp. 24–38 (2022) [3] L. Orgogozo, A.S. Prokushkin, O.S. Pokrovsky, C. Grenier, M. Quintard, J. Viers, S. Audry. Permafrost and Periglacial Processes, 30, pp. 75-89 (2019). [4] L. Orgogozo, T. Xavier, H. Oulbani, C. Grenier. submitted to Computer Physics Communications (under review). [5] L. Orgogozo, N. Renon, C. Soulaine, F. Hénon, S.K. Tomer, D. Labat, O.S. Pokrovsky, M. Sekhar, R. Ababou, M. Quintard. Computer Physics Communications, 185, pp. 3358-3371 (2014). [6] L. Orgogozo. Computer Physics Communications, 270, 108182 (2022). [7] M. Garcia-Gasulla, F. Banchelli, K. Peiro, G. Ramirez-Gargallo, G. Houzeaux, I. Ben Hassan Saïdi, C. Tenaud, I. Spisso, F. Mantovani. International Journal of Computational Fluid Dynamics, 34 (7-8), pp. 508-528, (2020) [8] hiperborea.omp.eu [9] eu-interact.org [10] genci.fr/en/our-computers [11] Hatté, C., Séjourné, A., Grenier, C., Marlin C., Pohl, E., Noret, A. Gauthier, C., Gandois, L., Costard, F., Ciais, P., Ottlé, C., Saintenoy A., Fedorov, A., Konstantinov, K. European Conference On Permafrost (2018).
Laurent Orgogozo
added 3 research items
Program Title: permaFoam CPC Library link to program files: https://doi .org /10 .17632 /swp88cvpwb .1 Developer’s repository link: https://develop .openfoam .com /Community /hydrology/ Licensing provisions: GPLv3 Programming language: C++ Nature of problem: This software solves the coupled equations that govern water flow and heat transfer in variably saturated and variably frozen porous media, for transient problems in Three-dimensional, heterogeneous domains. The equation for water flow is Richards equation, which is a very popular model for water transfer in variably saturated porous media (e.g.: soils), and the equation for heat transfer is a Fourier equation including advection and the freeze/thaw of the pore water. The solver is designed to take advantage of the massively parallel computing performance of OpenFOAM ® . The goal is to be able to model natural hydrosystems of cold regions on large temporal and spatial scales. Solution method: For each equation a mixed implicit (FVM for Finite Volume Method in the object oriented OpenFOAM framework) and explicit (FVC for Finite Volume Calculus in the object oriented OpenFOAM ® framework) discretization with backward time scheme is embedded in an iterative linearization procedure (Picard algorithm). The coupling between the two equations is performed through an operator splitting approach. The implementation has been carried out with a concern for robustness and parallel efficiency. Additional comments including restrictions and unusual features: This version of permaFoam has been tested with OpenFOAM_v1912, v2106, v2112 and v2206, thus everything might not work with other (especially older) versions of OpenFOAM ® . When using permaFoam, one should be careful to use fine enough spatial and temporal discretisations where and when steep fronts (freeze/thaw fronts, imbibition/drainage fronts) occur, otherwise numerical stability problems might arise.
Permafrost, i.e., soil that is year-round frozen in depth, is covering a quarter of the continents of the northern hemisphere. It currently experiences fast changes due to climate change at global scale and technogenic perturbations at local scale, and the assessment and anticipation of these changes are of primary importance for many environmental and engineering applications in cold regions. To these ends, permafrost modeling is required, while the strong couplings and non-linearities involved in the physics at stake make it highly challenging, especially from a computational point of view. In this work we present a new solver for permafrost hydrology developed in the framework of OpenFOAM®, allowing to benefit from its advanced high-performance computing capabilities. The solver is tested for realistic, field-based cases, and its parallel performances are characterized up to ∼16 000 cores on IRENE supercomputer (TGCC, CEA). Program summary Program Title: permaFoam CPC Library link to program files: https://doi.org/10.17632/swp88cvpwb.1 Developer's repository link: https://develop.openfoam.com/Community/hydrology/ Licensing provisions: GPLv3 Programming language: C++ Nature of problem: This software solves the coupled equations that govern water flow and heat transfer in variably saturated and variably frozen porous media, for transient problems in Three-dimensional, heterogeneous domains. The equation for water flow is Richards equation, which is a very popular model for water transfer in variably saturated porous media (e.g.: soils), and the equation for heat transfer is a Fourier equation including advection and the freeze/thaw of the pore water. The solver is designed to take advantage of the massively parallel computing performance of OpenFOAM®. The goal is to be able to model natural hydrosystems of cold regions on large temporal and spatial scales. Solution method: For each equation a mixed implicit (FVM for Finite Volume Method in the object oriented OpenFOAM framework) and explicit (FVC for Finite Volume Calculus in the object oriented OpenFOAM® framework) discretization with backward time scheme is embedded in an iterative linearization procedure (Picard algorithm). The coupling between the two equations is performed through an operator splitting approach. The implementation has been carried out with a concern for robustness and parallel efficiency. Additional comments including restrictions and unusual features: This version of permaFoam has been tested with OpenFOAM_v1912, v2106, v2112 and v2206, thus everything might not work with other (especially older) versions of OpenFOAM®. When using permaFoam, one should be careful to use fine enough spatial and temporal discretisations where and when steep fronts (freeze/thaw fronts, imbibition/drainage fronts) occur, otherwise numerical stability problems might arise.
Permafrost, i.e., soil that is year-round frozen in depth, is covering a quarter of the continents of the northern hemisphere. It currently experiences fast changes due to climate change at global scale and technogenic perturbations at local scale, and the assessment and anticipation of these changes are of primary importance for many environmental and engineering applications in cold regions. To these ends, permafrost modelling is required, while the strong couplings and non-linearities involved in the physics at stake make it highly challenging, especially from a computational point of view. In this work we present a new solver for permafrost hydrology developed in the framework of OpenFOAM ® , allowing to benefit from its advanced high-performance computing capabilities. The solver is tested for realistic, field-based cases, and its parallel performances are characterized up to ∼ 16 000 cores on IRENE supercomputer (TGCC, CEA).
Simon Cazaurang
added a research item
Boreal regions dynamics are strongly driven by perennially frozen soil (permafrost) physical properties. Sphagnum moss, lichen, and peat are widely present in these regions, forming a complex biological patchwork covering millions of km². In such regions, energy and mass transfers mainly occur via evapotranspiration, involving both vegetation hydraulic and thermal properties. The latest IPCC reports show that arctic regions are highly vulnerable to climate change. Therefore, a thorough study of arctic vegetation cover’s thermo-hydraulic properties are needed to create a numerical model of this biological boundary layer. In this work, arctic vegetation cover is pictured as a complex fibrous porous media. Based on this assumption, some methods used for porous media properties’ assessment (upscaling, representative elementary volume and homogenization) are developed hereafter. To this end, 12 dried samples extracted from Khanymey Research Station (Western Siberian Lowlands) are studied in conjunction with their X-ray tomographical reconstructions. These samples consist of eight Sphagnum moss samples, two lichen samples and two peat samples. First, a Representative Elementary Volume study associated with Direct Numerical Simulations is carried out to quantify porosity and hydraulic conductivity. For non-homogeneous samples, numerical simulations are made on generated pore net- work models. Then, thermal diffusivity and thermal conductivity are assessed using two techniques: signal and image processing results based on a modified Guarded Hot-Plate Method and direct numerical simulations associated with a pore network modeling. Results validate the assumption to consider this vegetation cover as a porous media. Some Representative Elementary Volumes are found for most samples concerning porosity and for homogeneous samples for hydraulic conductivity. For thermal properties, ongoing studies confirm strong insulation capabilities, joining previous conclusions made in the literature. Further work will be devoted to quantify the coupling between water content and state inside these peculiar biological porous media with their hydraulic and thermal properties.
Simon Cazaurang
added a research item
Sphagnum moss, lichen and peat are widely present in arctic regions, covering millions of km² in permafrost-dominated regions. This multi-component low vegetation strata plays a key role in surfaces fluxes in these areas, as they are the most widespread interface between the atmosphere and the geosphere. Therefore, characterizing their transfer properties such as hydraulic and thermal conductivities is crucial for climate change impacts forecasting in arctic regions. In this work, 12 samples were collected in a discontinuous permafrost arctic area (Khanymey Research Station, Russian Federation) and dried to ensure their conservation. Collected samples have been digitally reconstructed by X-ray scanning. After having assessed morphological and hydraulic properties using numerical analysis of the obtained 3D digital tomographies (Cazaurang et al., submitted), we aim here at developing and using both experimental and numerical methodologies to characterize thermal properties of these samples of Sphagnum, lichen and peat. This new study consist in comparisons of numerically and experimentally estimated thermal properties for contributing to the existing knowledge on Sphagnum, lichen and peat transfer properties. Experiments consist of a steady-state thermal conductivity estimation using a hot plate source on real arctic vegetation cover samples. For this purpose, samples are placed in a confined thermal atmosphere and a constant heat flux is applied at sample base. Thermal conductivity is then retrieved with the resolution of Fourier’s heat conduction law. Similarly, numerical computations are conducted on the same digital reconstructions than those used for hydraulic properties' determination. Simulations consist of a numerical reproduction of previously described experiments, allowing to strengthen the analysis of the experimental data. Additionally, the definition of representative elementary volumes of the studied samples is also undertaken using the numerical results. Compiling these assessments of transfer properties will represent essential information to simulate the dynamics of the permafrost underneath the arctic bryophytic layers with a devoted catchment-scale permafrost models. For instance, in the framework of the HiPerBorea project (hiperborea.omp.eu), this approach will be used to forecast the impacts of climate warming on boreal permafrost-dominated catchments.
Laurent Orgogozo
added a research item
PermaFoam is the OpenFOAM solver for permafrost dynamics simulation. It has first been published in 2019 (Orgogozo et al., PPP 2019), and a new version is in revision for publication (Orgogozo et al., in revision). The new features of permaFoam are presented, with new parallele performances assessments and examples of applications.
Laurent Orgogozo
added a research item
Le pergélisol couvre de vastes surfaces des régions polaires, et a des conséquences majeures sur les hydrosystèmes, les écosystèmes et les activités humaines. Le réchauffement climatique, si intense aux hautes latitudes, conduit à une réduction de son extension et à un épaississement de sa couche active. Anticiper ces impacts est donc un enjeu crucial pour comprendre la réponse des milieux polaires aux changements globaux, en lien notamment avec l’amplification arctique. L’approche de modélisation mécaniste, élément clé pour cette anticipation, ce heurte aux difficultés numériques posées par les couplages et les non-linéarités des problèmes physiques associés, conduisant à des temps de calculs très importants. Le projet ANR HiPerBorea présenté ici vise à surmonter ces difficultés par l'usage du calcul à hautes performances.
Laurent Orgogozo
added a research item
RichardsFoam3 is an updated version of the OpenFOAM solver RichardsFoam, previously presented in ”An open source massively parallel solver for Richards equation: Mechanistic modelling of water fluxes at the watershed scale” by L. Orgogozo et al (2014, Computer Physics Communications 185 : 3358-3371. DOI: 10.1016/j.cpc.2014.08.004), and in the new version announcement ”RichardsFOAM2: a new version of RichardsFOAM devoted to the modelling of the vadose zone” by L. Orgogozo (2015, Computer Physics Communications 196 : 619-620. DOI: 10.1016/j.cpc.2015.07.009). This new version includes improvements of memory handling and of on-the-fly control of computations, a better integration in the OpenFOAM framework, simplifications of the coding of some expressions, as well as new advanced boundary conditions. All together these developments allow to enhanced the ease of application of the code to continental surfaces hydrogeology modeling, its computational performances and its readability. The description of the elements contained in this release may be found in the readMe file. Please note that you may also find RichardsFoam3 on the hydrology page of the develop.openfoam.com interface: https://develop.openfoam.com/Community/hydrology/
Simon Cazaurang
added a research item
Western Siberia lowlands vegetation cover consists of a complex patchwork of bryophytes (mosses s.l.), lichens (symbiotic association of heterotrophic Fungus and autotrophic Algae) and underlying peat (Volkova et al., 2018). This vegetation cover is the main interface between permafrost driven soil dynamics and the atmosphere. The energetic transfers between the active layer and the atmosphere are mainly occurring by evapotranspiration (Hinzman & Kane,1992 ; Launiainen et al., 2015 ; Park et al., 2018). Between 2008 and 2016, arctic regions’ mean annual temperatures increased by 0.4 (± 0.25) °C, which represents the strongest mean annual temperature raise observed during this period on Earth (Biskaborn et al., 2019). Permafrost thaw poses a threat on global climate for the next hundred years because of the potential release of greenhouse gases, speeding up the global climate change as a feedback (Meredith et al., 2020). Understanding the role of arctic vegetation in thermal dynamics of the active layers requires the quantification of its thermo-hydrological properties, which is hence a key to generate an accurate long term model for a strong global climate change, as it has already been showed for Earth System Models (Stepanenko et al., 2020). Because of its intensive use as a manure and fuel for energy production, peat properties are well known. For instance, an exhaustive reviewing work has been recently conducted on peat pore morphology and interactions with permafrost (McCarter et al., 2020). However, living Sphagnum mosses’ properties only got few attention to date. Besides, there are no studies on lichen macroscopic scale thermo-hydrological properties to the knowledge of the authors. This preliminary study aims at making a quantitative analysis of the bryophytic cover as a complex porous medium. Porosity retrieval methods and morphological analyses are developed using an efficient, reproducible and fully digital workflow in order to obtain the effective hydraulic properties of this media.
Laurent Orgogozo
added a research item
Boreal peatlands are one of the most important stocks of active carbon on continental surfaces (Helbig et al., 2020). The Western Siberia Lowlands are the largest boreal peatlands on earth, with about 2 milllions of km2, and almost half of this vast area is constituted of frozen peats highly sensitive to climate warming (Pokrovsky et al., 2018). Besides, technogenic warming is also locally encountered there in places where for instance major energetic supply infrastructures are located (e.g.: Moskalenko 2009). Due to the intimate coupling that it provokes between water and heat fluxes, the presence of permafrost has strong impacts on biogeochemical fluxes and geomechanical processes (McKenzie et al., 2021). The warming induced frozen peatlands thaw has thus important consequences both at local scale (landscape dynamics, terrain stability) and at global scale (hydro-biogeochemical cycles, including C-cycle). The physics at stake in water and heat fluxes in such environments are highly coupled and non-linear, with complex interplays with the surface properties at small scales, for instance microtopography (Bobrik et al., 2015) and vegetation cover (Park et al., 2018). Thus, mechanistic modeling approaches are key tools for studying quantitatively the thermo-hydrological dynamics of permafrost affected boreal peatlands, and for predicting their responses to climate change. However the huge computational power that these approaches require is an obstacle toward their application. In this work we discuss the potential application of the High-Performance Computing (HPC) tool for permafrost modeling “permaFoam” (Orgogozo et al., 2019a) to the context of Western Siberia Peatlands, especially in the framework of the HiPerBorea project (hiperborea.omp.eu).
Laurent Orgogozo
added a research item
Permafrost is year round frozen soil, which covers 25% of the land of the northern hemisphere. The presence of permafrost affects tremendously both the natural processes (e.g.: water cycle) and the human activities (e.g.: building) in the affected areas. Its dynamics is governed by strongly coupled heat and mass (mainly water) transport, with couplings related for instance to advective transport of heat by water fluxes or to the strong impacts of phase changes on the hydrodynamic properties of soils. Moreover, these physical phenomena are affected by numerous non-linearities. Although challenging, the numerical simulation of coupled heat and mass transport in permafrost is needed both for environmental science and for cold regions engineering. The modeling of active (unfrozen) layer processes or the evaluation of climate-induced or technogenic permafrost thaw are classical applications of such numerical simulations. One of the major difficulties that limits the applicability of this kind of modeling is the huge computational resources that may be needed due to the strong non-linearities and couplings of the considered physical phenomena. This problem is especially critical for large scale 3D applications such as experimental watershed modeling. For this kind of studies the use of High Performance Computing (HPC) softwares and facilities is required. Here we present the first 3D thermo-hydrological simulation of a permafrost affected catchment performed with the massively parallel solver permaFoam, the OpenFOAM® solver for permafrost modeling. The conservation equations solved by permaFoam govern the 3D transient transport of water and heat in variably saturated porous media, taking into account freeze/thaw cycle of the pore water and water uptake in the root layer associated to evapotranspiration (Orgogozo et al., 2019). This solver has been implemented in the open source, generalist Computational Fluid Dynamics (CFD) tool box OpenFOAM®, so that it can benefit from the good parallel performances of this well-known HPC software. First a brief introduction of the permaFoam solver will be done, describing the implementation choices, the associated underlying assumptions and the adopted validation strategy. Then a case study dedicated to the characterization of the multi-decadal evolution under climate change of the thermo-hydrological state of a 40 km2 experimental catchment of Central Siberia will be presented. The related computations have been performed on regional (Olympe, ~13 000 cores, CALMIP) and national (Occigen, ~80 000 cores, CINES) supercomputers, and we will make a focus on the associated numerical challenges, such as scalability issues and I/O’s handling. Finally, the perspectives associated to these numerical developments will be discussed.
Laurent Orgogozo
added an update
A 2 years post-doc position is opening (to be started in january 2021) in Toulouse for making High Performance Computing simulations of permafrost evolution under climate change in several northern experimental watersheds. Please find more details below or in the attached file.
Location: GET laboratory (www.get.omp.eu) in Toulouse, France.
Lab. Affiliated to the Observatory Midi-Pyrénées (http://www.omp.eu).
Contract duration: Fixed-term period of 24 months with possibility of an extension, to be started in january 2021.
Salary: 2100 euros/month to 3150 euros/month (all taxes paid, including medical insurance) depending on the number of years after PhD defense, according to the national CNRS directives.
Contact: Laurent Orgogozo, University of Toulouse – Paul Sabatier Toulouse III (laurent.orgogozo@get.omp.eu).
Keywords: numerical simulation, Computational Fluid Dynamics (CFD), OpenFOAM®, High Performance Computing (HPC), supercomputers, massively parallel computing, heat transfer in porous media, flow in porous media, freeze/thaw processes, cryohydrogeology, cryohydrology, permafrost modeling, boreal areas, climate change impacts.
Scientific context:
This researcher position is associated with the HiPerBorea project funded by the French National Research Agency (ANR). HiPerBorea aims at enabling quantitative and predictive modeling of cold regions hydrosystems evolution under climate change. Arctic and sub-arctic areas, which are highly vulnerable to global warming, are largely covered by permafrost – soil that is year-round frozen at depth. Permafrost-affected areas, which represent 25% of emerged lands of the northern hemisphere, currently experience fast and important changes of both hydrological and thermal processes in response to climate change. In this project, advanced numerical modeling will be used to help predict the impact of permafrost thaw on thermo-hydrological status of the arctic regions. By doing so, HiPerBorea will provide mechanistic understanding of Arctic change, that is necessary to further understand carbon cycle and contaminant/nutrient transport, and to further assess risk and opportunity for sustainable urbanization, agriculture and general sustainable development of the (sub-)Arctic. Specifically, HiPerBorea will focus on producing quantitative estimates of climate change impacts on the thermo-hydrological status of permafrost in four experimental watersheds under long-term environmental monitoring (e.g.: stations of the INTERACT network). Studying the behaviors of these four watersheds which cover a large longitudinal gradient from Scandinavia to Eastern Siberia, we expect to get key information on the response of boreal areas to climate change.
The chosen strategy to reach this goal is numerical modeling based on computational fluid dynamics methods applied to cryohydrogeology and cryohydrology. The physical processes to be simulated are hydrogeological/hydrological transfers and thermal transfers with seasonal freeze/thaw cycles on boreal continental surfaces, which are described by strongly coupled and non-linear partial differential equations. Due to the large time scales (up to the century) and space scales (up to several tens of km²) to be dealt with, large computational loads will be encountered and the use of high performance computing will be required. In HiPerBorea the permaFoam solver for cryohydrogeology (Orgogozo et al., 2019) will serve as a basis for the development of a new open source cryohydrological simulator that will allow to perform the considered numerical modelings. The permaFoam solver has been developed in the framework of the well-known OpenFOAM®* computational fluid dynamics open source tool box, mainly in order to benefit from its good capabilities for massively parallel computation (e.g.: Orgogozo et al., 2014). The use of a new permaFoam based cryohydrological simulator on modern supercomputers such as the tier-2 supercomputer Olympe** of CALMIP or the tier-1 supercomputer Occigen*** of the CINES (and even tier-0 European supercomputing infrastructure if needed) will allow to perform the simulations of thermal and hydrological responses of the considered experimental catchments to various scenarios of climate change. These simulations will be unprecedented in terms of scales and resolutions in the field of cryo-hydrogeology and will be made using cutting edge modeling techniques. It is expected that they will give key novel insights on the on-going arctic changes, such as enveloppes for active layer thickness evolutions or for water fluxes evolutions within each considered watershed.
Job description: For each four studied watershed, the hired researcher will run the simulations of thermal and hydrological responses to climate change according to the various CMIP 5 scenarios using the HPC permafrost simulator developed in the HiPerBorea project (already operational flavor: permaFoam, Orgogozo et al., 2019 ; to be extended and developed during the HiPerBorea project by the other partners of the project). He/she will do the conditioning of the modelings (e.g.: building meshes representing Digital Elevation Models, boundary conditions that take into account meteorological forcings and land cover) on the basis of the field data and the satellite data existing for each watershed, using the advanced pre-processing tools of the OpenFOAM® environment (e.g.: snappyHexMesh, swak4foam). Once he/she will have performed the simulations on regional to European supercomputers, he/she will interpret the obtained results to quantitatively assess the potential impacts of climate change on boreal permafrost through watershed-wise analyses and comparative analyses between the considered watersheds. He/she will present the acquired knowledge in international scientific conferences and publish them in peer-reviewed, open access journals with high impact factors.
Required education, experience and skills: The hired researcher must be familiar with computational fluid dynamics methods, and should have expertise in at least one of the additional field listed below:
- transport in porous media ;
- high performance computing ;
- permafrost modeling.
An experience with the use of OpenFOAM would be highly appreciated, although not mandatory. Team-working state of mind and excellent scientific communication skills are also expected.
How to apply: Applicants should submit a complete application package by email to Laurent Orgogozo (laurent.orgogozo@get.omp.eu). It should include (1) a curriculum vitae including most important recent publications, (2) a statement of motivation and (3) names, addresses, phone numbers, and email addresses of at least two references. The application should be preferably submitted before the 1st of October 2020.
Bibliography:
Orgogozo L., Prokushkin A.S., Pokrovsky O.S., Grenier C., Quintard M., Viers J., Audry S., 2019. Water and energy transfer modeling in a permafrost-dominated, forested catchment of Central Siberia: the key role of rooting depth. Permafrost and Periglacial Processes 30 : 75-89.
Grenier C., Anbergen H., Bense V., Chanzy Q., Coon E., Collier N., Costard F., Ferry M., Frampton A., Frederick J., Gonçalvès J., Holmén J., Jost A., Kokh S., Kurylyk B., McKenzie J., Molson J., Mouche E., Orgogozo L., Pannetier R., Rivière A., Roux N., Rühaak W., Scheidegger J., Selroos J.-O., Therrien R., Vidstrand P., Voss C., 2018. Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases. Adv. Water Resour., 114, 196-218.
Orgogozo L., 2015. RichardsFOAM2: a new version of RichardsFOAM devoted to the modeling of the vadose zone. Computer Physics Communications 196 : 619-620. DOI: 10.1016/j.cpc.2015.07.009
Orgogozo L., Renon N., Soulaine C., Hénon F., Tomer S.K., Labat D., Pokrovsky O.S., Sekhar M., Ababou R., Quintard M., 2014. An open source massively parallel solver for Richards equation: Mechanistic modeling of water fluxes at the watershed scale. Computer Physics Communications 185 : 3358-3371. DOI: 10.1016/j.cpc.2014.08.004
 
Laurent Orgogozo
added 2 research items
Le permafrost (pergélisol) est un type de sol spécifique des régions froides, qui est gelé toute l'année en profondeur. La dynamique du permafrost (e.g.: cycle saisonniers de gel/dégel près de la surface, extension/retrait latéral sous changement climatique) a des impacts importants aussi bien sur les processus naturels que sur les activités humaines dans ces régions (e.g.: Walvoord and Kurylyk, 2016). Les phénomènes physiques impliqués sont des transferts d'eau et d'énergie en milieux poreux variablement saturés avec gel/dégel de l'eau porale, qui sont fortement couplés et non-linéaires. Par conséquent, la modélisation numérique 3D de ces processus à grande échelle (e.g.: échelle du bassin versant expérimental) nécessite une très grande puissance de calcul. Aussi la raison principale qui nous a conduit à développer un solveur dédié à la dynamique thermo-hydrologique des permafrost dans le cadre du logiciel open source de mécanique des fluides numériques OpenFOAM est qu'OpenFOAM permet d'utiliser de manière efficaces les supercalculateurs parallèles d'aujourd'hui. Notre solveur, le solveur permaFoam, a été validé dans le cadre du benchmark international Interfrost (Grenier et al., 2018), et a été appliqué avec succès à la modélisation 2D de la dynamique des couches actives (couches de surface saisonnièrement dégelées) d'un bassin versant experimental de Sibérie Centrale (Orgogozo et al., 2019). Afin de caractériser les performances parallèles de permaFoam, nous avons réalisé des expériences de scalabilité forte avec OpenFOAM-v1806 sur le superclculateur Olympe (méso-centre CALMIP, ~13 000 coeurs, installé dans la deuxième moitié de l'année 2018) avec des efficacités parallèles super-linéaires jusqu'à 1800 coeurs. Nous avons également réalisé des expériences similaires avec OpenFOAM-v5 sur le supercalculateur Occigen (CINES, ~80 000 coeurs) avec des efficacité parallèles d'environ 90% à 4000 coeurs. Les perspectives à court terme de ce travail résident dans l'application de permaFoam pour réaliser des simulations 3D d'évolution du permafrost sous changement climatique sur une echelle de temps centennale, pour des stations scientifiques de suivi environmental des régions boréales du réseau INTERACT (eu-interact.org). Des développements numériques supplémentaires sont également prévus afin d'enrichir la physique considérée (e.g.: inclure le transfert de soluté), et ainsi élargir le champ d'applications protentiel de permaFOAM.
Permafrost is a peculiar soil type of cold areas that is year-round frozen in-depth. Permafrost dynamics (e.g.: seasonal freeze/thaw cycles close to the surface, extension/retreat under climate changes) as strong impacts on both natural processes and engineering activities in cold regions (e.g.: Walvoord and Kurylyk, 2016). The involved physics are water and heat transfers in variably saturated porous media with freeze/thaw of the poral water, which are strongly coupled and non-linear. Thus, in order to perform real scale 3D modeling of such processes, huge computational power may be needed. That is the main reason why we choose to develop a dedicated solver for permafrost thermo-hydrological dynamics in the framework of OpenFOAM. Our solver, the so-called permaFoam solver, has been validated in the framework of the Interfrost international benchmark (Grenier et al., 2018), and has been successfully applied to the 2D simulation of active layers (seasonaly thawed layer of permafrost close to the surface) of an experimental watershed of Central Siberia (Orgogozo et al., 2019). In order to assess the parallel capabilities of the permaFoam solver, we performed strong scaling experiments up to 4000 cores with OpenFOAM 5.0 on Occigen supercomputer (CINES supercomputing center, ~80 000 cores) and up to 1800 cores with OpenFOAM-v1806 on Olympe supercomputer (CALMIP supercomputing center, ~13 000 cores, installed in the second half of 2018). The short term perspectives associated to this work is the application of the permaFoam solver to 3D, century time scales simulations of permafrost dominated experimental watersheds of the Interact network (eu-interact.org) in order to study the potential thermo-hydrological impacts of climate changes. Further codes developments are also scheduled in order to enrich the considered physics (e.g.: include solute transport), and by doing so to broaden the field of applications of permaFoam. References: Grenier C, Anbergen H, Bense V, et al. Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases. Advances in Water Resources. 2018;114:196-218. DOI: 10.1016/j.advwatres.2018.02.001 Orgogozo L, Prokushkin AS, Pokrovsky OS, et al. Water and energy transfer modeling in a permafrost-dominated, forested catchment of Central Siberia: the key role of rooting depth for evapotranspiration fluxes. Permafrost and Periglacial Processes. 2019;30(2):75-89. DOI: 10.1002/ppp.1995 https://hal.archives-ouvertes.fr/hal-02014619 Walvoord MA and Kurylyk BL. Hydrologic impacts of thawing permafrost – a review. Vadose Zone J. 2016;15(6). DOI: 10.2136/vzj2016.01.0010
Laurent Orgogozo
added an update
This PhD project aims to develop relevant and efficient modeling of exchanges of energy and matter through boreal continental surfaces for the simulations of cryohydrological and cryohydrogeological dynamics at the experimental watershed scale planned in the HiPerBorea project. In particular, the thermo-hydrological transfers within the bryophytic layers (mosses, lichens) and within the snowpack will be carefully investigated, given their strong impacts on active layer dynamics of permafrost affected areas. This PhD will be located in Toulouse, in the South of France, at the Fluid Mechanics Institute of Toulouse laboratory (IMFT). It may start in January 2020, and at the latest in October 2020. Please refer to the PhD subject in attachment for more details.
 
Laurent Orgogozo
added a research item
PermaFoam, the OpenFOAM® solver for permafrost modeling, has recently been used to characterize the thermo-hydrological dynamics of the Kulingdakan catchment, an experimental watershed in Central Siberia that is monitored since more than a decade (Orgogozo et al., 2019). Following this study of water and energy fluxes in a permafrost-dominated, forested area in current climatic conditions, numerical assessments of the impact of various scenarios of climate change are scheduled in the framework of the HiPerBorea project (funded by the ANR for 2020-2023), for this watershed and for other arctic watersheds, most of them in Siberia. The objective of HiPerBorea is to enable quantitative and predictive modeling of cold regions hydrosystems evolution under climate change. Arctic and sub-arctic areas, which are highly vulnerable to global warming, are largely covered by permafrost. Permafrost-affected areas, which represent 25% of emerged lands of the northern hemisphere, mostly in Siberia, are prone to major biogeochemical and ecological transformations due to permafrost thaw, with strong associated feed-backs on greenhouse gas cycling (degradation of previously permanently frozen organic carbon pools – e.g. Zimov et al., 2006). Currently, fast and important changes of both hydrological (Walvoord and Kurylyk, 2016) and thermal (Loranty et al., 2018) states of the northern continental surfaces are observed in response to permafrost thaw. We hypothesize that these hydrological and thermal impacts will amplify over the next decades. We will use advanced numerical modelling build on permaFoam to address the issue and help predict the impact of permafrost thaw on arctic thermo-hydrologic functioning. By doing so, we will provide mechanistic understanding of Arctic change, that is necessary to further understand carbon cycling and contaminant/nutrient transport, and to further assess risk and opportunity for sustainable urbanization, agriculture and general sustainable development of the (sub-)Arctic. On the road to reach this goal, severe computational difficulties will be encountered due to the long computation times required by the numerical resolutions of the highly coupled and non linear equations at stake. In this presentation we will discuss these numerical challenges and illustrate our strategy to overcome them by showing several preliminary scaling studies performed both on regional (Olympe, @CALMIP) and national (Occigen, @CINES) supercomputers.
Laurent Orgogozo
added 6 project references
Laurent Orgogozo
added a project goal
The objective of this project is to enable quantitative and predictive modeling of cold regions hydrosystems evolution under climate change. Arctic and sub-arctic areas, which are highly vulnerable to global warming, are largely covered by permafrost – soil that is year-round frozen at depth. Permafrost-affected areas, which represent 25% of emerged lands of the northern hemisphere, are prone to major biogeochemical and ecological transformations due to permafrost thaw, with strong associated feed-backs on greenhouse gas cycling (degradation of previously permanently frozen organic carbon pools). We will use advanced numerical modelling build on the permaFoam solver (the OpenFOAM solver for permafrost modelling, see Orgogozo et al., 2019) to help predict the impact of permafrost thaw on arctic thermo-hydrologic functioning. By doing so, we will provide mechanistic understanding of Arctic change, that is necessary to further understand carbon cycling and contaminant/nutrient transport, and to further assess risk and opportunity for sustainable urbanization, agriculture and general sustainable development of the (sub-)Arctic.
Orgogozo L., Prokushkin A.S., Pokrovsky O.S., Grenier C., Quintard M., Viers J., Audry S., 2019. Water and energy transfer modelling in a permafrost-dominated, forested catchment of Central Siberia: the key role of rooting depth. Permafrost and Periglacial Processes 30 : 75-89.