Areal Distribution of the Various Combinations of Quaternary Climates

On reconnaît maintenant que les paléoclimats ont laissé leur trace dans le sol, sur la végétation et les paysages de diverses régions du monde. De nombreuses méthodes d'analyse, discutées et discutables, permettent de découvrir quels étaient les climats du Tertiaire et du Quaternaire, leur forme, leur influence et leur extension et ainsi de connaître l'évolution et les changements des paysages

Climatic Relationships of Permafrost Zones in Areas of Low Winter Snow-Cover

In areas with under 50 cm snow cover in winter, the permafrost zones show diagnostic long term freezing indices and thawing indices. The warmer boundary of the zone of continuous permafrost traverses the mean annual air temperature (MAAT). The boundary between discontinuous and sporadic permafrost lies just on the cold side of 0° C MAAT. The sporadic permafrost zone includes the zone of ice caves and the regions with patches of ice beneath ponds and peatbogs, extending to 5° C MAAT at a thawing index of 4000 degree days per year. The relationship is applicable to Norway, Iceland, Spitzbergen, Canada and the People's Republic of Mongolia. There are some marked variations in lapse rate from one environment to another, the most marked of which occurs above tree line where the lapse rate increases markedly in winter, though not in summer. This produces a change in MAAT of 2.5° C on Plateau Mountain. The changes also occur at some points in non-permafrost areas and it appears likely that they are due to spatial and seasonal changes in albedo. Whatever the cause, the variations in lapse rate indicate that calculations of past world climate change based on data from one area may be misleading

Cold Air Drainage West of Fort Nelson, British Columbia

In the early mornings of 7, 22 and 23 January 1982, intense cold air drainage was observed in the valleys on the eastern slopes of the Rocky Mountains west of Fort Nelson, British Columbia. Temperature differences of 31 degrees C were noted, the coldest temperature recorded being -71 degrees C (a new North American record), though even colder temperatures probably occurred at other sites. These were produced by an intense cold arctic high-pressure cell which gave regionally still air and clear skies and permitted marked local cooling during the nights. Similar conditions should be expected elsewhere along the slopes of the Rocky Mountains in northern B.C. and southern Yukon Territory

Dynamics and Origin of Saline Soils on the Slims River Delta, Kluane National Park, Yukon Territory

The saline soils of the Slims River Delta have developed on land formed in the last 100 years in an area of otherwise continuous permafrost. Deep seasonal frost on the delta prevents downward leaching of salts when the snow melts. Instead the salts accumulate at the surface as the ground dries, while additional salts are added from springs at the base of the surrounding mountains. Late summer rains can leach the soils if they are sufficiently heavy, producing a three- to fourfold variation in salinity from year to year. The efflorescences are dominated by the hexahydrate of magnesium sulfate, and the high sulfate content is probably the reason that soils in depressions with the morphology of solonetzic soils remain reasonably friable. The distribution of the characteristic halophytic plant associations found on these soils appears to be controlled more by soil moisture content than by the actual salinity level.

Climatic Zonality of Periglacial Landforms in Mountain Areas

The alpine periglacial areas of the world can be divided into three distinctive landscape types dominated by one of the following: active rock glaciers, active block streams, or gelifluction landforms. These also correspond to distinct climates, the active rock glaciers occurring under cold, humid conditions; the active block streams in cold, dry climates; and gelifluction-dominated landforms occurring in warmer areas. These have distinct ranges of mean annual temperature and precipitation, which can be used in interpreting climatic changes based on distribution of fossil landforms.Key words: alpine permafrost, block streams, rock glaciers, gelifluctionOn peut diviser les régions périglaciaires alpines du globe en trois types de paysages distincts, dominés par un des éléments suivants: glaciers rocheux actifs, coulées de pierres actives ou reliefs de gélifluxion. Ces éléments correspondent aussi à des climats distincts, les glaciers rocheux existant dans des conditions de froid et d'humidité; les coulées de pierres actives sous des climats froids et secs; et les reliefs de gélifluxion dans des régions plus tempérées. Ces paysages ont des gammes différentes de moyennes annuelles de températures et de précipitations, qui peuvent servir à interpréter les changements climatiques fondés sur la distribution des reliefs fossiles.Mots clés : pergélisol alpin, coulées de pierre, glaciers rocheux, gélifluxio

Permafrost Distribution, Zonation and Stability along the Eastern Ranges of the Cordillera of North America

Considerable quantities of new data have become available recently regarding the nature and distribution of permafrost along the eastern ranges of the Cordillera. These are used to produce an elevation view of permafrost in the ranges north of the 35°N parallel. In the south, there is a zone of sporadic permafrost up to 1,000 m in vertical extent overlain by continuous permafrost. The zone of discontinuous permafrost (30-80 percent of the surface with permafrost) is only about 70 m in vertical extent. North of 54°N this changes, with discontinuous permafrost encroaching on the sporadic permafrost zone. The apparent permafrost boundaries differ from those of Brown (1967), Péwé (1983a) and Cheng Guodong (1983). Their work was based on considerably less data, and it is clear that the terrain factors of mean winter snow depth, local moisture and ground water conditions, the distribution of the different air masses and cold air drainage have considerable effect locally, causing undulations and abrupt changes in the lower limit of the permafrost boundaries to about 56°N. Farther north, the climatic factors become dominant. The lower boundaries are different for a different latitude in North America and China. Subdivision of the alpine permafrost into stable, metastable and unstable classes is useful in indicating the instability of alpine permafrost (Cheng Guodong, 1983) and shows that most of the permafrost found in mainland Canada and Alaska is unstable or metastable.Key words: permafrost distribution, permafrost thermal stability, eastern Cordillera of North America, alpine permafrost, permafrost zonationMots clés: distributions du pergélisol, stabilité thermale du pergélisol, cordillère est de l'Amérique du Nord, pergélisol alpin, zonage du pergéliso

Altitude Trends in Permafrost Active Layer Thickness, Kluane Lake, Y.T.

On the northwest-facing slopes of Outpost Mountain, Kluane Lake, the permafrost active layer shows an anomalous relationship with altitude, being thinner (typically 40 cm) between 823 and 910 m altitude than above or below this belt. Maximum thicknesses (about 90 cm) are encountered in the shrub tundra at 1310 m elevation. These thicknesses do not correlate with soil types or suprapermafrost drainage, but they do correlate well with the thickness of the organic mat (Of layer) where this exceeds 2.5 cm thickness. The mat apparently acts as a natural insulator.Key words: Of thickness, active layer thickness, alpine permafrost, altitudinal variations, alpine and subalpine vegetation Sur les pentes nord-ouest de la montagne Outpost au lac Kluane, la couche active du pergélisol montre une anomalie avec l'altitude, étant plus mince (40 cm en général) entre 823 et 910 m d'altitude, qu'au-dessus ou en dessous de ce niveau. Les épaisseurs maximales (90 cm environ) se trouvent dans les arbustes de la toundra à une altitude de 1310 m. Ces épaisseurs ne présentent pas de corrélation avec les types de sol ou le drainage du suprapergélisol, mais elles en présentent une très nette avec l'épaisseur du tapis de matériau organique (la couche Of) là où il dépasse 2,5 cm d'épaisseur. Ce tapis semble agir comme un isolant naturel. Mots clés : épaisseur Of, épaisseur de la couche active, pergélisol alpin, variations avec l'altitude, végétation alpine et subalpin

An Occurrence of the Hawkweed-Leaved Saxifrage, Saxifraga hieraciifolia, in Southern British Columbia, and its Palaeobotanical Implications

The Hawkweed-Leaved Saxifrage (Saxifraga hieraciifolia), normally found in the alpine tundra in the Arctic, has been collected at 445 m in parkland near Chase, British Columbia. The closest previously recorded occurrence was on the tundra of the Liard Plateau, northern British Columbia. The new occurrence indicates that this species had migrated at least as far south as northern Washington State before the Late Wisconsin glaciation. The latter eliminated the species in British Columbia, but a small population survived south of the glaciers and then, after deglaciation, it migrated north into southern British Columbia, but along the lower limit of the main Boreal Forest instead of above treeline

New Records of Cyperaceae and Juncaceae from the Yukon Territory

Two new species of Cyperaceae are reported, viz., Carex hoodii, and Eleocharis elliptica. Also, range extensions for eight species of Carex, Eriophorum, and Juncus are listed