Ground-atmosphere modelling of mountain permafrost evolution: Strategies to combine RCM and subsurface simulations
Zusammenfassung der Projektergebnisse
Climate change as projected by contemporary General Circulation Models (GCMs) and Regional Climate Models (RCMs) will have a great impact on high latitude and high mountain permafrost. Within this project atmospheric data from regional climate simulations were used as forcing data for a complex 1‐dimensional subsurface model (CoupModel) to simulate the hydro‐thermal regime at various permafrost sites. The RCM forcing data (radiation, air temperature, precipitation, humidity, wind speed) were chosen from six different scenarios of the ENSEMBLES project data base and were altitude corrected and de‐biased to serve as input for the subsurface simulations. Statistical analysis of the modelled climate variables as well as of the output of the impact model has been conducted to gain insight into the sensitivity of the active layer to changes in climatic conditions. Calibration of the subsurface model was conducted using snow cover and subsurface temperature data from the PERMOS (Permafrost Monitoring Switzerland) network. The model was improved regarding mountain permafrost conditions, notably by adding heat sources/sinks in the active layer to represent a coarse blocky surface layer where applicable. Simulations were conducted for three mountain permafrost test sites of the SPCC‐Bündel project. The study showed the general applicability of the combined RCM‐permafrost model approach even though the sometimes large uncertainties within the whole model chain have to be considered prior to site‐specific interpretation. Furthermore, the 1D approach of the soil model only allows for the identification of major sensitivity differences between the two sites and cannot be used to predict detailed future permafrost conditions in a spatial context. Main findings from the project are: Snow cover duration is consistently shortened by around 50 to 80 days during the 21st century in all scenarios chosen and at all three sites. The corresponding impact on the ground thermal regime mainly consist of a warming as air temperatures increase as well and a significant cooling effect in autumn due to the absence of the snow cover could not be observed on the long term. A first phase of permafrost degradation is visible by increasing active layer depths and a warming of the underlying permafrost body. During a second phase the permafrost becomes inactive, with positive temperatures persisting in the thawed layer over the years. The simulated permafrost at the test site Schilthorn reacts more sensitive to the projected climate variations than the one at Murtèl rock glacier, which is due to the differences in the initial ice content at the two sites, as the massive ice core within rock glacier Murtèl absorbs large amounts of energy. The results are consistent with observations during 2000‐2012, where the active layer at Schilthorn showed a much higher sensitivity to comparatively warm years (= deepening) than at Murtèl. The relative importance of influencing factors on active layer thickness could be identified both within observational data as well as in the permafrost model. Most important factors in the simulations were the ice content at the onset of the melting period and the summer surface temperatures. Days with snow cover and date of melt out of the snow cover are additional factors especially at sites with a generally smaller snow cover thicknesses.
Projektbezogene Publikationen (Auswahl)
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(2009): Permafrost and climate in Europe: monitoring and modelling thermal, geomorphological and geotechnical responses. Earth Science Reviews 92 (3‐4), 117‐171
Harris, C., L. Arenson, H. Christiansen, B. Etzelmüller, R. Frauenfelder, S. Gruber, W. Haeberli, C. Hauck, M. Hoelzle, O. Humlum, K. Isaksen, A. Kääb, M. Kern‐Lütschg, M. Lehning, N. Matsuoka, J. Murton, J., Nötzli, M. Phillips, N. Ross, M. Seppälä, S. Springman, D. Vonder Mühll
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(2010): Meltwater infiltration into the frozen active layer at an alpine permafrost site. Permafrost and Periglacial Processes 21: 325–334
Scherler, M., Hauck, C., Hoelzle, M., Stähli, M. and Völksch, I.
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2010. Sub‐surface heterogeneities in the Murtèl‐Corvatsch rock glacier, Switzerland. Geo2010, 6th Canadian Permafrost Conference, Calgary, Canada, 1494–1500
Arenson L, Hauck C, Hilbich C, Seward L, Yamamoto Y, Springman S.
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2010: Influence of atmospheric forcing parameters on modelled mountain permafrost evolution. Meteorologische Zeitschrift, 19( 5), 491‐500
Engelhardt, M., Hauck, C. and Salzmann, N.
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(2011): A new model for estimating subsurface ice content based on combined electrical and seismic data sets. The Cryosphere, 5, 453–468
Hauck, C., Böttcher, M. and Maurer, H.
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(2012): Influence of surface and subsurface heterogeneity on observed borehole temperatures at a mountain permafrost site in the Upper Engadine, Swiss Alps. The Cryosphere, 6, 517‐531
Schneider, S., Hoelzle, M. and Hauck, C.
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(2012): The potential of new measurement and modelling techniques in alpine cryosphere and geomorphology research. Geographica Helvetica 1‐2/2012, 26‐37
Hauck, C., Collet, C., Delaloye, R., Hilbich, C., Hoelzle, M., Huss, M., Salzmann, N.
