气候变化领域集成服务门户(CCPortal): New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco)

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DOI	10.5194/tc-11-1691-2017
	New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco)
	Vieira G.; Mora C.; Faleh A.
发表日期	2017
ISSN	19940416
卷号	11 期号:4
英文摘要	Relict and present-day periglacial features have been reported in the literature for the upper reaches of the High Atlas mountains, which is the highest range in North Africa (Djebel Toubkal - 4167 m a.s.l.). A lobate feature in the Irhzer Ikhibi south at 3800 m a.s.l. has been previously interpreted as an active rock glacier, but no measurements of ground or air temperatures are known to exist for the area. In order to assess the possible presence of permafrost, we analyse data from June 2015 to June 2016 from two air temperature measurement sites at 2370 and 3210 m a.s.l. and from four ground surface temperature (GST) sites at 3220, 3815, 3980 and 4160 m a.s.l. to characterize conditions along an altitudinal gradient along the Oued Ihghyghaye valley to the summit of the Djebel Toubkal. GSTs were collected at 1 h intervals, and the presence of snow cover at the monitoring sites was validated using Landsat 8 and Sentinel-2 imagery. Two field visits allowed for logger installation and collection and for assessing the geomorphological features in the area. The results show that snow plays a major role on the thermal regime of the shallow ground, inducing important spatial variability. The lowest site at 3220 m had a thermal regime characterized by frequent freeze-thaw cycles during the cold season but with few days of snow. When snow settled, the ground surface remained isothermal at 0 °C , indicating the absence of permafrost. The highest sites at 3980 and 4160 m a.s.l. showed very frequent freeze-thaw cycles and a small influence of the snow cover on GST, reflecting the lack of snow accumulation due to the wind-exposed settings on a ridge and on the summit plateau. The site located at 3815 m in the Irhzer Ikhibi south valley had a cold, stable thermal regime with GST varying from -4.5 to -6 °C from December to March, under a continuous snow cover. The site's location in a concave setting favours wind-driven snow accumulation and lower incoming solar radiation due to the shading effect of a ridge, inducing the conservation of a thick snow pack. The stable and low GSTs are interpreted as a strong indicator of the probable presence of permafrost at this site, which is an interpretation supported by the presence of lobate and arcuate features in the talus deposits. We present first results and further observations using geophysics, and borehole measurements are foreseen. This is the first time that probable permafrost has been reported from temperature observations in the mountains of North Africa. © 2017 Author(s).
学科领域	altitude; freeze-thaw cycle; geomorphology; Landsat; monitoring; periglacial landform; permafrost; rock glacier; satellite imagery; Sentinel; site investigation; snow accumulation; snow cover; solar radiation; spatial variation; valley; High Atlas; Jebel Toubkal; Marrakech-Safi; Morocco
语种	英语
scopus关键词	altitude; freeze-thaw cycle; geomorphology; Landsat; monitoring; periglacial landform; permafrost; rock glacier; satellite imagery; Sentinel; site investigation; snow accumulation; snow cover; solar radiation; spatial variation; valley; High Atlas; Jebel Toubkal; Marrakech-Safi; Morocco
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119368
作者单位	Centre for Geographical Studies, IGOT, Universidade de Lisboa, Portugal; Université Sidi Mohamed Ben Abdellah, Fès, Morocco
推荐引用方式 GB/T 7714	Vieira G.,Mora C.,Faleh A.. New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco)[J],2017,11(4).
APA	Vieira G.,Mora C.,&Faleh A..(2017).New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco).Cryosphere,11(4).
MLA	Vieira G.,et al."New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco)".Cryosphere 11.4(2017).