Numerical modelling of permafrost spring discharge and open-system pingo formation induced by basal permafrost aggradation

Abstract. In the high Arctic valley of Adventdalen, Svalbard, sub-permafrost groundwater feeds several pingo springs distributed along the valley axis. The driving mechanism for groundwater discharge and associated pingo formation is enigmatic because wet-based glaciers in the adjacent highlands and the presence of continuous permafrost seem to preclude recharge of the sub-permafrost groundwater system by either a sub-glacial source or a precipitation surplus. Since the pingo springs enable methane that has accumulated underneath the permafrost to escape directly to the atmosphere, our limited understanding of the groundwater system brings significant uncertainty to the understanding of how methane emissions will respond to changing climate. We address this problem with a new conceptual model for open-system pingo formation wherein pingo growth is sustained by sub-permafrost pressure effects during millennial scale basal permafrost aggradation. We test the viability of this mechanism for generating groundwater flow with decoupled heat (1D-transient) and groundwater (2D-steady-state) transport modelling experiments. Our results show that the pingos in lower Adventdalen easily conform to this conceptual model. Simulations suggest that the generally low-permeability hydrogeological units cause groundwater residence times that exceed the duration of the Holocene. The likelihood of such pre-Holocene groundwater ages is also supported by the hydrogeochemistry of the pingo springs, which demonstrate a sea-wards freshening of groundwater, potentially supplied by paleo-subglacial melting during the Weichselian. Such waters form a sub-permafrost fresh water wedge that progressively thins inland, where the duration of permafrost aggradation is longest. The mixing ratio of the underlying marine waters therefore increases in this direction because less unfrozen freshwater is available for mixing. Although this unusual hydraulic system is most likely governed by permafrost aggradation, the potential for additional pressurization is also explored. We conclude that methane production and methane clathrate formation may also affect hydraulic the pressure in sub-permafrost aquifers, but additional research is needed to fully establish their influence.

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Numerical modelling of permafrost spring discharge and open-system pingo formation induced by basal permafrost aggradation

The Cryosphere ◽

10.5194/tc-14-4627-2020 ◽

2020 ◽

Vol 14 (12) ◽

pp. 4627-4651

Author(s):

Mikkel Toft Hornum ◽

Andrew Jonathan Hodson ◽

Søren Jessen ◽

Victor Bense ◽

Kim Senger

Keyword(s):

Conceptual Model ◽

Open System ◽

Pressure Effects ◽

The Arctic ◽

Spring Discharge ◽

Driving Mechanism ◽

Hydraulic Pressure ◽

Transport Modelling ◽

Groundwater System ◽

Millennial Scale

Abstract. In the high Arctic valley of Adventdalen, Svalbard, sub-permafrost groundwater feeds several pingo springs distributed along the valley axis. The driving mechanism for groundwater discharge and associated pingo formation is enigmatic because wet-based glaciers are not present in the adjacent highlands and the presence of continuous permafrost seems to preclude recharge of the sub-permafrost groundwater system by either a subglacial source or a precipitation surplus. Since the pingo springs enable methane that has accumulated underneath the permafrost to escape directly to the atmosphere, our limited understanding of the groundwater system brings significant uncertainty to predictions of how methane emissions will respond to changing climate. We address this problem with a new conceptual model for open-system pingo formation wherein pingo growth is sustained by sub-permafrost pressure effects, as related to the expansion of water upon freezing, during millennial-scale basal permafrost aggradation. We test the viability of this mechanism for generating groundwater flow with decoupled heat (one-dimensional transient) and groundwater (three-dimensional steady state) transport modelling experiments. Our results suggest that the conceptual model represents a feasible mechanism for the formation of open-system pingos in lower Adventdalen and elsewhere. We also explore the potential for additional pressurisation and find that methane production and methane clathrate formation and dissolution deserve particular attention on account of their likely effects upon the hydraulic pressure. Our model simulations also suggest that the generally low-permeability hydrogeological units cause groundwater residence times to exceed the duration of the Holocene. The likelihood of such pre-Holocene groundwater ages is supported by the geochemistry of the pingo springs which demonstrates an unexpected seaward freshening of groundwater potentially caused by a palaeo-subglacial meltwater “wedge” from the Weichselian. Whereas permafrost thickness (and age) progressively increases inland, accordingly, the sub-permafrost meltwater wedge thins, and less unfrozen freshwater is available for mixing. Our observations imply that millennial-scale permafrost aggradation deserves more attention as a possible driver of sustained flow of sub-permafrost groundwater and methane to the surface because, although the hydrological system in Adventdalen at first appears unusual, it is likely that similar systems have developed in other uplifted valleys throughout the Arctic.

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Methane Clathrate Formation is Catalyzed and Kinetically Inhibited by the Same Molecule: Two Facets of Methanol

The Journal of Physical Chemistry B ◽

10.1021/acs.jpcb.1c01274 ◽

2021 ◽

Author(s):

Zhaoqian Su ◽

Saman Alavi ◽

John A. Ripmeester ◽

Gedaliah Wolosh ◽

Cristiano L. Dias

Keyword(s):

Clathrate Formation ◽

Methane Clathrate

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Enhanced Characterization of the Krania–Elassona Structure and Functioning Allogenic Karst Aquifer in Central Greece

Geosciences ◽

10.3390/geosciences9010015 ◽

2018 ◽

Vol 9 (1) ◽

pp. 15 ◽

Cited By ~ 3

Author(s):

Antonios Manakos ◽

Maria Ntona ◽

Nerantzis Kazakis ◽

Konstantinos Chalikakis

Keyword(s):

Conceptual Model ◽

Moving Average ◽

Karst Aquifer ◽

Groundwater Vulnerability ◽

Spring Water ◽

Geological Mapping ◽

Spring Discharge ◽

Water Type ◽

Central Greece

The present study highlights the importance of geological, hydrogeological, and hydrogeochemical characterization of a karst aquifer in building a conceptual model of the system. The karst system of Krania–Elassona in central Greece was chosen for this application. Hydrogeological research included geological mapping and hydrogeological analysis. Additionally, hydrochemical analysis of water samples was performed in boreholes, rivers, and the system’s main spring. The Krania–Elassona aquifer consists of three horizons of marbles and is characterized by mature karstification. The karst aquifer is characterized by allogenic recharge mainly from the River Deskatis that accounts for up to 92% of the total flow. Groundwater and spring water are generally characterized as good quality and are suitable for irrigation and domestic use. The water type of the spring water is classified as Mg-HCO3. The application of a SARIMA (Seasonal Autoregressive Integrated Moving Average Model) model verified the conceptual model and successfully simulated spring discharge for a two-year period. The results of this study highlight the importance of basic hydrogeological research and the initial conceptualization of karst systems in reliably assessing groundwater vulnerability and modeling.

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Kinetics of methane clathrate formation and dissociation under Mars relevant conditions

Icarus ◽

10.1016/j.icarus.2011.12.019 ◽

2012 ◽

Vol 218 (1) ◽

pp. 513-524 ◽

Cited By ~ 30

Author(s):

S.R. Gainey ◽

M.E. Elwood Madden

Keyword(s):

Clathrate Formation ◽

Methane Clathrate ◽

Kinetics Of

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Sensitivity analysis of conceptual model calibration to initialisation bias. Application to karst spring discharge models

Advances in Water Resources ◽

10.1016/j.advwatres.2012.03.020 ◽

2012 ◽

Vol 42 ◽

pp. 1-16 ◽

Cited By ~ 11

Author(s):

N. Mazzilli ◽

V. Guinot ◽

H. Jourde

Keyword(s):

Sensitivity Analysis ◽

Conceptual Model ◽

Model Calibration ◽

Spring Discharge ◽

Karst Spring

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Reaction rate constant of methane clathrate formation

Fuel ◽

10.1016/j.fuel.2009.06.019 ◽

2010 ◽

Vol 89 (2) ◽

pp. 294-301 ◽

Cited By ~ 27

Author(s):

Sebastien Bergeron ◽

Juan G. Beltrán ◽

Phillip Servio

Keyword(s):

Rate Constant ◽

Reaction Rate ◽

Reaction Rate Constant ◽

Clathrate Formation ◽

Methane Clathrate

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Unraveling nucleation pathway in methane clathrate formation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2011755117 ◽

2020 ◽

Vol 117 (40) ◽

pp. 24701-24708

Author(s):

Liwen Li ◽

Jie Zhong ◽

Youguo Yan ◽

Jun Zhang ◽

Jiafang Xu ◽

...

Keyword(s):

Large Scale ◽

Md Simulations ◽

Hydration Layer ◽

Clathrate Formation ◽

The Earth ◽

Hydration Layers ◽

Methane Clathrate ◽

Water Ring ◽

Growth Pathway ◽

Nucleation Growth

Methane clathrates are widespread on the ocean floor of the Earth. A better understanding of methane clathrate formation has important implications for natural-gas exploitation, storage, and transportation. A key step toward understanding clathrate formation is hydrate nucleation, which has been suggested to involve multiple evolution pathways. Herein, a unique nucleation/growth pathway for methane clathrate formation has been identified by analyzing the trajectories of large-scale molecular dynamics (MD) simulations. In particular, ternary water-ring aggregations (TWRAs) have been identified as fundamental structures for characterizing the nucleation pathway. Based on this nucleation pathway, the critical nucleus size and nucleation timescale can be quantitatively determined. Specifically, a methane hydration layer compression/shedding process is observed to be the critical step in (and driving) the nucleation/growth pathway, which is manifested through overlapping/compression of the surrounding hydration layers of the methane molecules, followed by detachment (shedding) of the hydration layer. As such, an effective way to control methane hydrate nucleation is to alter the hydration layer compression/shedding process during the course of nucleation.

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A system dynamic approach for simulation of a knowledge transfer model of heterogeneous senders in mega project innovation

Engineering Construction & Architectural Management ◽

10.1108/ecam-01-2020-0077 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Huimin Liu ◽

Yanru Yu ◽

Yuxing Sun ◽

Xue Yan

Keyword(s):

Knowledge Transfer ◽

Conceptual Model ◽

Knowledge Creation ◽

Academic Research ◽

Transfer Model ◽

Driving Mechanism ◽

Qualitative Model ◽

Knowledge Stock ◽

Content Type ◽

Factors Affecting

PurposeThe owners of mega projects typically assemble multiple academic research units and enterprises to form an innovation alliance, which carries out knowledge transfer and knowledge creation targeting technical challenges in the process of engineering construction. Due to high technical and management complexity of mega projects, factors affecting knowledge transfer among innovation subjects are complex and diverse. This study proposes a mixed system dynamics (SD) method to build and simulate the process of knowledge transfer in mega projects innovation and analyzes the driving mechanism that enhances knowledge stock of enterprises and engineering innovation results.Design/methodology/approachFirst, this paper proposes a conceptual model for knowledge transfer in mega projects by adopting event analysis of the data gained from investigations and interviews. Then, a qualitative model of knowledge transfer that considers mutual influences of the owner, academic research unit and enterprises is developed. Based on that, mathematical relationship among variables of the qualitative model is determined and a quantitative model of knowledge transfer that considers heterogeneity of knowledge sender is built. Finally, simulation is achieved using Vensim software.FindingsThe factors affecting knowledge stock of enterprises are analyzed from three aspects: (1) the individual motives and capability of academic research units and enterprises; (2) the gap between academic research units and enterprises; (3) the heterogeneity of academic research units. The results show that the willingness and capability of knowledge reception by enterprises, specific knowledge transfer context such as relational distance and organization distance between academic research units and enterprises and academic research units with high knowledge stock have key influences on the knowledge stock of enterprises.Research limitations/implicationsFactors affecting knowledge transfer within the alliance of innovation in mega projects and their correlations are highly complicated and difficult to determine. Despite massive investigations and interviews on many long-span bridges in China in this study, it is barely possible to directly obtain accurate data for all variables in the model. Limitations of historical data result in limitations on applications of the proposed model.Practical implicationsBy building the mega projects knowledge transfer model and conducting simulation analysis, this paper has generated practical values for the owners of mega projects on fostering, organizing, coordinating and managing of innovations. Especially, this study provides specific strategies and suggestions on selection of innovation subjects, motivation and guaranteed efficiency of knowledge transfer and knowledge creation of academic research units and enterprises.Originality/valueThis study proposes a conceptual model for factors affecting knowledge transfer that applies to innovations in mega project context, which fills the gap in the research of knowledge management in mega project innovations. Additionally, combining with the method of SD, the unique role of owner in knowledge transfer of mega projects and the differences among various knowledge senders and their influences on knowledge stocks of enterprises are thoroughly considered, and the research method of modeling and simulation of knowledge transfer mechanism is supplemented and extended.

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Design of Open System of Loop Heat Pipe Experimental Rig for Phase Change Driving Force and Visual Experiment Study

Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems ◽

10.1115/mnhmt2016-6727 ◽

2016 ◽

Author(s):

Kai Zhu

Keyword(s):

Phase Change ◽

Heat Pipe ◽

Open System ◽

Stable Condition ◽

Point Of View ◽

Experimental Point ◽

Driving Mechanism ◽

Loop Heat Pipe ◽

Whole Process ◽

Experimental Rig

The open system of visual loop heat pipe experimental rig driven by phase change of the refrigerant is established, which is used to research the effect of parameters of the volume, supplementary of refrigerant, properties of wick, height of evaporation cavity and heating power on the performance of this system quantitatively, also the heat transfer characteristics of refrigerant flow in the evaporator visually is studied. We observed and researched the whole process of system from the start up to the stable condition in the evaporator, the changes of refrigerant which is from boiling to the gas-liquid separation. From the experimental point of view, it provides a basis for the establishment of the closed system and for the creation of new mathematical model of the driving mechanism.

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