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Air circulation and energy fluxes in the coarse debris layer of high Alpine permafrost sites

Applicant Hauck Christian
Number 169499
Funding scheme Project funding (Div. I-III)
Research institution Unité de Géographie Département des Géosciences Université de Fribourg
Institution of higher education University of Fribourg - FR
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.04.2017 - 31.03.2021
Approved amount 254'524.00
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All Disciplines (3)

Discipline
Hydrology, Limnology, Glaciology
Geomorphology
Geophysics

Keywords (8)

convection; rock glacier; coarse blocky layer; air circulation; modelling; talus slope; mountain permafrost; energy balance

Lay Summary (German)

Lead
Luftzirkulation und Energieflüsse in grobblockigem Permafrost im Hochgebirge
Lay summary
Permafrost im Hochgebirge ist zur Zeit grossen Veränderungen ausgesetzt – der beobachtete und prognostizierte Klimawandel führt zu einer Erwärmung des Untergrundes und zu potentiellen Hanginstabilitäten. Unter den typischen Untergrundmaterialien (Fels, feinkörnig, grobblockiger Schutt) hat insbesondere das grobblockige Material eine spezielle Funktion, da es aufgrund des hohen Luftgehaltes hohe thermische Isolationseigenschaften besitzt und den Permafrost gegen ansteigende Temperaturen schützt. Zusätzlich kann ein konvektiver Wärmetransport entstehen, der warme Luft aus dem Untergrund nach oben und kalte Luft in den Untergrund hinein transportiert. Beide Effekte zusammen lassen Permafrostvorkommen auch auf niedriger Meereshöhe (z.B. in Blockhalden in Mittelgebirgen) entstehen und erzeugen kältere Mikroklimate in grobblockigem Material.

Obwohl das Phänomen seit langem bekannt ist gibt es bisher keine umfassende numerische Modellierung der beteiligten Prozesse. Feldstudien beschränken sich meist auf die Analyse der (einfach zu messenden) Oberflächentemperatur oder der Untergrundtemperatur in Bohrlöchern. Für eine Projektion des Einflusses der Klimaänderung ist aber die komplette 2-d Betrachtung der Temperaturverteilung und Luftzirkulation im Untergrund notwendig. Im vorliegenden Projekt soll nun unter Zuhilfenahme numerischer Methoden aus den Ingenieurswissenschaften der Kühlungseffekt dieser konvektiven Prozesse quantifizieren werden.

Die Projektziele sind wie folgt:

1) Anpassung und Weiterentwicklung eines bestehenden numerischen finite-Elemente Modells zur Simulation konvektiver Prozesse in grobblockigem Material

2) Quantifizierung des Kühlungseffekts im Vergleich zu den anderen Komponenten der Energiebilanz; auch im Hinblick auf zukünftige Klimaänderungen

3) Validierung mit Messdaten von alpinen Blockhalden und Blockgletschern des Schweizer Permafrostbeobachtungsnetzwerks PERMOS

Direct link to Lay Summary Last update: 13.10.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
Air Convection in the Active Layer of Rock Glaciers
Wicky Jonas, Hauck Christian (2020), Air Convection in the Active Layer of Rock Glaciers, in Frontiers in Earth Science, 8, 335.
Modeling Convective Heat Transfer in the Porous Active Layer of an Alpine Rock Glacier
Wicky Jonas, Hauck Christian (2018), Modeling Convective Heat Transfer in the Porous Active Layer of an Alpine Rock Glacier, in Proceedings of the 2018 COMSOL Conference in Lausanne, LausanneCOMSOL Conference, Lausanne.
Numerical modelling of convective heat transport by air flow in permafrost talus slopes
Wicky Jonas, Hauck Christian (2017), Numerical modelling of convective heat transport by air flow in permafrost talus slopes, in The Cryosphere, 1311-1325.

Collaboration

Group / person Country
Types of collaboration
Geotest AG Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
- Industry/business/other use-inspired collaboration
COMSOL Switzerland (Europe)
- Research Infrastructure
- Industry/business/other use-inspired collaboration
University of Fribourg/Freiburg (Prof. R. Delaloye) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Swiss Permafrost Monitoring Network PERMOS Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Department of Geosciences, University of Fribourg (Prof. M. Hoelzle) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
University of Zurich (Prof. A. Vieli) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Department of Geosciences, University of Oslo (Dr. S. Westermann/Prof. B. Etzelmüller) Norway (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Swiss Geoscience Meeting SGM 2020 Poster The thermal behaviour of a low elevation cold talus slope: Insights through numerical modeling 06.11.2020 Zürich, Switzerland Hauck Christian; Wicky Jonas;
Swiss Geoscience Meeting SGM 2019 Poster Thermal effects of natural air convection in the active layer of rock glaciers 22.11.2019 Freiburg, Switzerland Hauck Christian; Wicky Jonas;
COMSOL Geoscience Day 2019 Talk given at a conference Numerical Modeling of Convective Heat Transfer in Porous Permafrost in the Swiss Alps 27.05.2019 Fribourg, Switzerland Wicky Jonas; Hauck Christian;
European Geosciences Union General Assembly EGU 2019 Talk given at a conference Air Convection Within the Active Layer of an Alpine Rock Glacier: A Numerical Modelling Approach 07.04.2019 Wien, Austria Hauck Christian; Wicky Jonas;
Swiss Geoscience Meeting SGM 2018 Talk given at a conference Assessing the influence of convection in the active layer of a rock glacier on ground temperatures 01.12.2018 Bern, Switzerland Wicky Jonas; Hauck Christian;
COMSOL Conference 2018 Poster Modeling Convective Heat Transfer in the Porous Active Layer of an Alpine Rock Glacier 22.10.2018 Lausanne, Switzerland Wicky Jonas; Hauck Christian;
European Conference on Permafrost EUCOP 2018 Poster Convective Heat Transfer in Coarse Permafrost Substrate - A Numerical Model Study in the Swiss Alps 23.06.2018 Chamonix, France Wicky Jonas; Hauck Christian;
POLAR 2018 Talk given at a conference Modelling Convective Heat Transfer in Alpine Permafrost 15.06.2018 Davos, Switzerland Wicky Jonas; Hauck Christian;
Swiss Geoscience Meeting SGM 2017 Poster Influence of slope angle on the convective heat transfer in porous permafrost substrate 18.11.2017 Davos, Switzerland Hauck Christian; Wicky Jonas;


Self-organised

Title Date Place
COMSOL Geoscience Day 2019 27.05.2019 Fribourg, Switzerland

Associated projects

Number Title Start Funding scheme
178823 Improved ice quantification at alpine permafrost sites based on electrical and electromagnetic measurements of spectral induced polarization 01.08.2018 Project funding (Div. I-III)

Abstract

Mountain permafrost is currently undergoing substantial changes due to climate change as a whole and especially due to the observed and projected air temperature increase. Among the typical mountain permafrost substrates, i.e. rock, fine sediments and coarse blocky surfaces, the latter play an important role because of their high insulating characteristics for the subsurface underneath due to the low thermal conductivity of the air voids between the blocks. In addition, air convection with upward transport of warmer air from the permafrost body and downward transport of cold air from the surface can take place within the coarse blocky layer, both, vertically (in flat terrain) as well as in form of a 2-dimensional slope circulation. These two effects lead to (a) low altitude permafrost occurrences in form of undercooled scree/talus slopes (e.g. Kneisel et al. 2000, Delaloye and Lambiel 2005), (b) persisting permafrost occurrences at the lower limit of permafrost (in form of rock glaciers, ice-cored moraines and talus slopes) and (c) much colder surface and subsurface temperatures for surfaces with coarse blocky surface layers (e.g. Schneider et al. 2012, Gubler et al. 2011). Whereas the energy balance for the coarse blocky surface layer of rock glaciers (and debris covered glaciers) has been addressed in several field and modelling studies (e.g. Hanson and Hoelzle 2004, Scherler et al. 2014, Reid and Brock 2010), the effect of 1D or 2D air convection has not been treated in detail. Moreover, the internal air circulation in talus slopes driven by the gradient between outside (air) and internal (talus) temperature has mainly been analysed by field studies, but not been quantified with respect to the other terms in the energy balance. Transient numerical simulations of permafrost mostly neglect the influence of convective heat transfer in air on the thermal regime this process (or parameterize it with an apparent thermal conductivity (Gruber and Hoelzle 2008) or with an artificial heat sink (Scherler et al. 2013, 2014). In contrast, in civil engineering many studies were carried out to investigate the thermal behavior of blocky layers and to improve their passive cooling capacity (e.g. Goering and Kumar, 1996). In the proposed project we will use and adapt the modelling concepts from civil engineering to model heat transfer in air flow in talus slopes and rock glaciers, and quantify the cooling effect in comparison with the other terms of the energy balance determined by existing energy balance approaches (e.g. Scherler et al. 2014).Specifically, the project aims to:1)Adapt an existing engineering software that has already been tested for permafrost applications (e.g. Arenson et al. 2006, Wicky, 2015), for real field cases in the Swiss Alps2)Quantify the amount of cooling due to convective air circulation within the coarse blocky surface layer (in addition to enhanced thermal insulation, and in comparison to all other parts of the energy balance)3)Validate the simulation results by ground surface temperature and borehole temperature data at two well-studied and well-equipped field sites, talus slope Lapires and rockglacier Murtèl.
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