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Auteurs :
Fort, Monique

Description :

International audience

Mountain environments are very sensitive to climate change, yet assessing the potential impacts of these changesis not easy because of the complexity and diversity of mountain systems. The Himalayan permafrost belt presentsthree main specificities: (1) it develops in a geodynamically active mountain, which means that the controllingfactors are not only temperature but also seismo-tectonic activity; (2) due to the steepness of the southern flankof the Greater Himalaya and potential large scale rock failures, permafrost evidence manifests itself best in theinner valleys and on the northern, arid side of the Himalayas (elevations >4000m); (3) the east-west strike ofthe mountain range creates large spatial discontinuity in the “cold” belt, mostly related to precipitation natureand availability. Only limited studies have been carried to date, and there is no permanent “field laboratory”, norcontinuous records but a few local studies. Based on preliminary observations in the Nepal Himalayas (mostlyin Mustang and Dolpo districts), and Indian Ladakh, we present the main features indicating the existence ofpermafrost (either continuous or discontinuous). Rock-glaciers are quite well represented, though their presencemay be interpreted as a combined result from both ground ice and large rock collapse. The precise altitudinalzonation of permafrost belt (specifying potential permafrost, probable permafrost, observed permafrost belts) stillrequires careful investigations in selected areas.Several questions arise when considering the evolution of permafrost in a context of climate change, with itsimpacts on the development of potential natural hazards that may affect the mountain population. Firstly, permafrostdegradation (ground ice melting) is a cause of mountain slope destabilization. When the steep catchmentsare developed in frost/water sensitive bedrock (shales and marls) and extend to high elevations (as observedin Mustang or Dolpo), it would supply more mass-wasting and debris-flow events and may directly threat theinfrastructures recently built to unlock these remote areas. Secondly, acceleration of permafrost degradation mightalso affect the steepest rock walls (as in Khumbu, Manang and Mustang Himals) and cause rock avalanches thatcould impact nearby settlements, as suggested by relicts of past events. Lastly, ground ice is a hidden source ofwater in areas without permanent glacial ice. In a context of global warming this non-renewable resource would bedepleted and no longer available for the population living in these areas, all the more as growing tourism activitiesare increasing the demand for water consumption that may conflicts with irrigated agricultural uses down valley.More in-situ observations and long-term monitoring studies should certainly be useful to understand climatetrends hence permafrost evolution and their consequences in order to help mountain populations of the cold, aridHimalayas to adjust to progressive changes in their environmental conditions and resources.



Mots-clés :
risque nature - permafrost - Ladakh - Népal - Himalayas - évolution climatique - changement climatique - [SDU] Sciences of the Universe [physics] - [SDU.STU] Sciences of the Universe [physics]/Earth Sciences - [SDU.STU.CL] Sciences of the Universe [physics]/Earth Sciences/Climatology

Editeur :
HAL CCSD

Langue :
en

Type de document :
info:eu-repo/semantics/conferenceObject, Conference papers

Source :
Geophysical Research Abstracts; EGU General Assembly 2015; https://hal.archives-ouvertes.fr/hal-01262187; EGU General Assembly 2015, Apr 2015, Vienne, Austria. Geophysical Research Abstracts, 17, p. 4733, Geophysical Research Abstracts

Date :
2015-04-12

Contributeurs :
Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG) ; Université Panthéon-Sorbonne (UP1) - Institut de Recherche pour le Développement (IRD) - École pratique des hautes études (EPHE) - Université Paris-Sorbonne (UP4) - AgroParisTech - Université Paris Diderot - Paris 7 (UPD7) - Centre National de la Recherche Scientifique (CNRS)

Identifiants :
hal-01262187
https://hal.archives-ouvertes.fr/hal-01262187

Couverture :

Vienne, Austria