The periglacial environment of the high summits of the Chic-Chocs Mountains (Gautier Davesne)

November 10, 2016 in post

On the summits of the Chic-Chocs Mountains (North of Appalachians Range, Gaspé Peninsula) exceeding 1100 to 1200 m a.s.l., a typical periglacial environment is present. Above this elevation, only various alpine tundra species as lichens, herbs and mosses can grow on the blocky materials which characterize the ground surface (fig. 1). At Mont Jacques-Cartier (1273 m a.s.l.), the block fields, or felsenmeers, mantle a large part of the summit where the slope angle is lower than 21° (fig. 1). Over the flat surface, the blocky materials are reworked by the periglacial processes producing sorted polygons in patches where an abundant matrix of fine-grained material exists (fig. 1). On the margins of the plateau, the sorted polygons tend to stretch as the slope angle exceeds 3 to 4° to form block streams (fig. 1). Gelifluxion lobes are observable on the slopes of Mont Jacques-Cartier and Mont Albert as a result of the freeze-thaw cycle and the abundance of snowmelt water in spring (e.g. snowbed on the SE slope of Mont Jacques-Cartier). Finally, the highest summits of the Chic-Chocs Mountains present marginal contemporary permafrost bodies due to favourable azonal topoclimate conditions.

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Figure 1: Periglacial landforms observed over the Mont Jacques-Cartier plateau : A) blockstreams ; B)block fields or felsenmeers ; C) Sorted polygons.

More information in the following papiers:

Gray, J.T., Godin, E., Masse, J., and Fortier, D. (2009) Trois décennies d’observation des fluctuations du régime thermique du pergélisol dans le parc national de la Gaspésie, Le Naturaliste Canadien, 133, 69-77.

Davesne, G., Fortier, D., Dominé, F., Gray, J. (2016) Wind driven snow conditions control the occurrence of contemporary marginal mountain permafrost in the Chic-Chocs Mountains, south-eastern Canada – a case study from Mont Jacques-Cartier. The Cryosphere Discussion, doi: 10.5194/tc-2016-211.

Gray, J.T., Davesne, G., Godin, E. and Fortier, D. (2016) The Thermal Regime of Mountain Permafrost at the Summit of Mont Jacques-Cartier in the Gaspé Peninsula, Québec, Canada: A 37 Year Record of Fluctuations showing an Overall Warming Trend, Permafrost and Periglacial Processes. doi: 10.1002/ppp.1903.

 

 

Mont Jacques-Cartier, a remarquable site for mountain permafrost evolution monitoring in eastern america (Gautier Davesne)

October 20, 2016 in focus-en, post

First studies dealing with the mountain permafrost in the Chic-Chocs Mountains has been undertaken at the end of the 1970’s by Gray and Brown, who highlighted the similarities between the periglacial environments of the Chic-Chocs Mountains and of the arctic regions. Based on this observation, Gray and Brown hypothesised that marginal permafrost bodies may be present on the highest plateaus of the range, especially on Mont Jacques-Cartier and Mont Albert. To validate this hypothesis, an instrumentation program was developed in September 1977 (fig. 1) on Mont Jacques-Cartier consisting of drilling a 29 m deep borehole at the summit and installing 23 thermistors on it to measure the ground temperature at various depths (Gray et Brown, 1979). With a 36-year long record of the geothermal regime (1979-2014) furnished by the thermistors cable, Mont Jacques-Cartier is one of the longest permafrost-monitoring sites in North America. This marginal permafrost body, the southernmost in Canada, is very close to the melting point and thus highly sensitive to minor climate fluctuations. Furthermore, the thermal regime of the ground responds quickly to the climate changes due to the high thermal conductivity of the rock in which it is present (Gray et al., 2009; 2016). The long-term ground temperature time series extracted from the borehole are thus very interesting to understand the responses of the permafrost to the climate changes and the consequences of permafrost degradation on the alpine geosystem of the Chic-Chocs Mountains.

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Drilling the borehole on Mont Jacques-Cartier summit in September 1977 (Photo: James Gray)

Gray, J.T. et Brown, R. J. E. (1979). Permafrost existence and distribution in the Chic-Chocs Mountains, Gaspésie, Québec. Géographie physique du Quaternaire33(3-4), 299-316.

Gray, J.T., Godin, E., Masse, J. et Fortier, D. (2009). Trois décennies d’observation des fluctuations du régime thermique du pergélisol dans le parc national de la Gaspésie. Le Naturaliste Canadien133(3), 69-77.

Gray, J., Davesne, G., Fortier, D., and Godin, E. (2016) The Thermal Regime of Mountain Permafrost at the Summit of Mont Jacques-Cartier in the Gaspé Peninsula, Québec, Canada: A 37 Year Record of Fluctuations showing an Overall Warming Trend. Permafrost and Periglacial  Processes, doi: 10.1002/ppp.1903