GEOSCAN, résultats de la recherche


TitreChanging thermal state of permafrost in northern Canada
AuteurSmith, S; Duchesne, C; Ednie, M; Lewkowicz, A G
SourceArctic Change 2014, oral presentation abstracts; 2014 p. 171-172
Séries alt.Secteur des sciences de la Terre, Contribution externe 20150020
RéunionArctic Change 2014; Ottawa; CA; décembre 8-12, 2014
Mediaen ligne; numérique
ProvinceYukon; Territoires du Nord-Ouest; Nunavut; Québec; Territoires du Nord-Ouest; Yukon; Nunavut
SNRC15; 16; 25; 26; 27; 28; 29; 35; 36; 37; 38; 39; 45; 46; 47; 48; 49; 55; 56; 57; 58; 59; 65; 66; 67; 68; 69; 75; 76; 77; 78; 79; 85; 86; 87; 88; 89; 95; 96; 97; 98; 99; 105; 106; 107; 115; 116; 117; 120; 340; 560
Lat/Long OENS-180.0000 180.0000 90.0000 60.0000
Sujetspergélisol; congélation du sol; glace fossile; températures au sol; climat arctique; fluctuations climatiques; climat; analyses thermiques; temperature; Changement climatique; géologie de l'environnement; géologie des dépôts meubles/géomorphologie
ProgrammeSurveillance des variables climatiques, Géosciences de changements climatiques
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
Changes in permafrost temperature is an important indicator of the state of permafrost and of a changing climate. Permafrost temperatures have been measured in boreholes across northern Canada for three decades. The International Polar Year (IPY) provided the opportunity to enhance the permafrost monitoring network which now consists of over 150 boreholes representing the wide range of vegetation, geological and climate conditions found in the Canadian permafrost regions. A snapshot of the thermal state of permafrost was also developed during IPY (2007-09) which provided a baseline against which future change can be measured. Recent permafrost temperatures measured in 2013-14 have been compared to the IPY snapshot to evaluate the change in permafrost thermal state that has occurred since IPY. This change has also been examined in the context of the longer term record that exists for some monitoring sites.
Current ground temperatures, measured at or close to the maximum depth of season variation, at many sites are higher than those measured during IPY. However, the greatest change is found in colder permafrost especially in the eastern and High Arctic. For example at sites established during IPY in the Baffin region of Nunavut where permafrost is at temperatures between -5 and -15°C, current temperatures at 15 m depth are up to 1°C higher than that measured during IPY. Although the record for these sites is short this recent change in permafrost temperature is consistent with that observed in the longer record for Alert in the High Arctic which shows a general increase in permafrost temperature since 1980s with a greater rate of increase (about 1.5°C per decade at 15 m depth) since 2000. Air temperature records from Alert indicate that some of the highest air temperatures on record have occurred since 2000 with 2009-2012 being among the warmest years on record. This recent warming is likely responsible for the increase in permafrost temperatures observed over the past decade.
Change in permafrost temperatures since IPY has been smaller in northwestern Canada. For sites in the continuous permafrost zone of the northern Mackenzie region, increases in permafrost temperature generally less than 0.2°C have been observed. In warm permafrost in the discontinuous zone, of the Mackenzie Valley and southern Yukon, little or no change in permafrost temperature has been observed. The longer records available for sites in the Mackenzie Valley indicate a general warming of permafrost since the 1980s but temperatures have increased at a lower rate since 2000 partly due to lower air temperatuers following a peak in 1998. At sites where permafrost is at temperatures close to 0°C, energy is largely used to thaw the ground and degradation of warm permafrost has been observed since IPY.
In general, warming of permafrost is continuing across northern Canada. These changes in permafrost thermal state and degradation of warm permafrost have implications for ecosystems, infrastructure and communities. The ongoing data collection from the monitoring network provides essential information to plan and adapt to these changes.
Résumé(Résumé en langage clair et simple, non publié)
Les températures du pergélisol mesurées dans l'ensemble du Canada en 2013-2014 sont comparées aux données de base établies durant l'Année polaire internationale (API, 2007-2009). Depuis l'API, la température du pergélisol a augmenté sur plusieurs sites; le changement le plus important a eu lieu dans le pergélisol froid de l'Arctique de l'Est et du Haut-Arctique. Peu de changements, voire aucun, ont été observés dans le pergélisol chaud de la vallée du Mackenzie et le sud du Yukon, mais une dégradation du pergélisol a été observée. Ces résultats concordent avec les données à long terme sur la température du pergélisol recueillies au cours des 20 ou 30 dernières années et indiquent que le réchauffement du pergélisol se poursuit. Le réchauffement et le dégel du pergélisol se répercutent sur les écosystèmes et l'infrastructure dans le nord du Canada.