bluuebunny/crossref_metadata_2025_split huggingface dataset:
Caractéristiques de la Cinétique de Congélation de Sols Salins
Authors: Frolov A. D. , Seguin M.‐K. 
Published: February 2007

AbstractNous présentons l'analyse des résultats d'une étude expérimentale réalisée à l'aide des méthodes de spectroscopie diélectrique et de conversion électroacoustique. Ces expériences ont été effectuées sur des modèles de sable de quartz poreux saturé de solutions de concentration différente, à contenu ionique différent et gelé. Ces expériences ont permis d'établir les particularitées communes à la cinétique de congélation de sols salins. Il s'est avéré que la concentration limite des solutions saturantes dans les pores est d'environ 10−2 mole 1−1. Cette limite correspond à la concentration a partir de laquelle la cinétique de congélation de sols salins diffère substantiellement de celle de sols non‐salins. Pour des concentrations de solutions dans les pores qui sont >10−2 mole 1−1, le sable gelé conserve sa perméabilité (dans les pores et capillaires) jusqu'à des temperatures très basses. On démontre que lors du processus de congélation, le changement du contenu de la phase liquide s'effectue en měme temps que le degré de discrétisation (ségrégation et fractionation) volumique et la mobilité des ions augmentent. La modification d'un sol gelé fortement salin (>10−1 mole 1−1) en un sol gelé non‐salin s'effectue à des températures environ 10 K plus basses que les eutectiques pour le composé ionique d'une solution spécifique.
Origin of permafrost lake deposits in the Central Andes
Authors: Gorbunov A. P. 
Published: February 2007

AbstractPerennially frozen lacustrine deposits in the Bolivian Altiplano are discussed. They are situated between 21°38′S and 23°13′S at an elevation of 4117–4730 m ASL. It is hypothesized that these ice‐rich lacustrine deposits formed as the result of subaquatic freezing of sediments in the Late Pleistocene to Early Holocene. The permafrost bodies are represented today by flat‐topped ridges and mounds which are the remnants of the original lake plains destroyed by thermokarst processes.
Permafrost distribution and rock glaciers in the livigno area (Northern Italy)
Authors: Guglielmin M. , Lozej A. , Tellini C. 
Published: February 2007

AbstractGeophysical investigations were undertaken in the Livigno area (Sondrio, northern Italy) during 1991–92 at a number of sites where permafrost had been suggested through the application of other techniques, such as geomorphological studies, measurements of bottom temperature of winter snow cover (BTS), measurement of ground temperature in summertime (STG), and temperature of spring waters. Geoelectrical surveys confirm and characterize these permafrost occurrences. Furthermore, they indicate that, outside the rock glaciers, permafrost is also present in some gelifluction lobes. The permafrost bodies differ with regard to parameters such as resistivity, depth and thickness. Resistivity ranges from 18,000 to 560,000 ωm (ohm metres), depth varies between 8 and 21.1 m, and the active layer is 2 to 4.7 m thick in those bodies that can be considered active on the basis of morphological features.
Streamflow processes in an alpine permafrost catchment, tianshan, China
Authors: Woo Ming‐Ko , Yang Zhenniang , Xia Zhaojun , Yang Daqing 
Published: February 2007

AbstractThe Cirque Basin, Tianshan, China is characterized by steep slopes, coarse surficial deposits and a cold climate that maintains permafrost at shallow depths. These conditions exert strong influences on the streamflow processes. In late winter, freezing of the infiltrated meltwater from an uneven snow cover enables ground ice formation. This renders parts of the active layer impervious to seepage, and in the spring both surface and subsurface flows can occur to supply water to the stream. In summer, the coarse materials facilitate rapid infiltration and exfiltration. Where the channel slope is steep, as in the upper basin, infiltration results in a dry stream bed but deep percolation is prevented by a shallow frost table. Exfiltration prevails in the lower basin where the channel gradient is reduced, and streamflow increases rapidly within half a kilometre, from zero to its maximum values at the gauging station. Water balance analysis yields a high runoff ratio of 0.75 for this basin and this is comparable with other tundra areas. The streamflow processes observed in this basin should be applicable to other non‐polar alpine catchments.
Climate controls and high‐altitude permafrost, qinghai‐xizang (tibet) Plateau, China
Authors: Wang Baolai , French Hugh M. 
Published: February 2007

AbstractThe high altitude‐induced permafrost of the Tibet Plateau reflects a geothermal regime characterized by a strong diurnal pattern, high solar radiation inputs at the surface, and a high geothermal gradient. As a result, the permafrost is relatively [warm] and sensitive to thermal disturbance. Typical permafrost‐related processes, such as ice segregation and thermal contraction cracking, are not widespread, and patterned ground phenomena (circles and nets) are restricted to sites of locally high moisture and variable grain size. Ice‐rich sediments on north‐facing slopes occur mainly as silty colluviums derived from local argillaceous bedrock. Mean annual ground temperatures are usually warmer than −3.5°C. Temperatures at 20 m depth have increased by an average of 0.2 to 0.3°C during the past 15 years. If one assumes continued warming, permafrost is likely to become relict within the next 200 years, and an increase in degradation (i.e. thermokarst processes) is to be expected.
Current changes of climate and permafrost in the arctic and sub‐arctic of Russia
Authors: Pavlov A. V. 
Published: February 2007

AbstractIn northern Russia, from the time meteorological measurements began in the early nineteenth century to the end of that century, the air temperature was characterized by a general decrease (approximately 1°C). It then rose up to the 1950s (by 0.6°C). A subsequent slight fall in temperature lasted until the mid 1970s. Since then a further rise has been observed (0.6–0.9°C). Temperatures in the upper horizons of permafrost over the last 10–20 years are in good agreement with recent global warming trends. For the European north‐east during the period 1970–90 a rise in temperature at a depth of 3 m amounted to 0.6–0.7°C on average. However, this rise is related not necessarily to a rise in air temperature, but more likely to an increase in snow cover.
Thufur in the mohlesi valley, lesotho, Southern Africa
Authors: Grab S. W. 
Published: February 2007

AbstractAlthough a considerable amount of periglacial work has concentrated on thufur found in polar and subpolar regions, information pertaining to those in other areas, especially the alpine regions of Africa, is extremely limited. Field observations and measurements provide empirical information on their external and internal morphology in an alpine region of Lesotho, southern Africa. Animal activity, wind action, the effects of surface water and/or ice, and the influence of needle ice are factors which cause thufa breakup. Some thufur in the Mohlesi valley are inactive while others are periodically active under present climatic conditions.
Ice‐wedge rejuvenation, fosheim peninsula, ellesmere Island, Canada
Authors: Lewkowicz Antoni G. 
Published: February 2007

AbstractIce wedges with multiple growth stages and complex wedge systems are described for six sites on the Fosheim Peninsula. Recent rates of lateral wedge growth, inferred from tritium concentrations within the ice, are 2–5 mm a−1. One factor responsible for ice wedge rejuvenation in this area is colluviation on low‐angled slope segments by slopewash, solifluction and active‐layer detachment processes or by mudflow within retrogressive thaw slumps. The most complex section examined was at the base of a long slope where colluvial deposits overlay peat. Epigenetic and syngenetic wedges of at least two and possibly three different ages were present as a result of sedimentation rates estimated to be 4–25 mm a−1.The second factor producing wedge rejuvenation is variability in summer climate, and this is responsible for the development of the uppermost growth stages at all actively cracking sites. The deepest thaws in the past 45 years were hind‐cast for 1960 and 1962 so that more than 25 years of aggradation had taken place by the time of fieldwork. More generally, it can be shown that there is a significant probability that secondary wedges will be present during any period without regional climatic change. For the Eureka summer climate, the probability is 0.2 that a secondary wedge at least 5 cm high and 10 years old will be observed at any randomly exposed section. Thus field observation of widespread secondary growth stages is not necessarily an indication of recent climatic change but may be due to normal climatic variability.
Ice‐wedge casts and relict polygonal patterned ground in North‐East Iowa, USA
Authors: Walters James C. 
Published: February 2007

AbstractSediment‐filled wedges and associated polygonal patterned ground occur in pre‐Illinoian sediments in north‐east Iowa. A total of 183 vertical to near‐vertical wedge‐shaped bodies of sand have been observed at 12 sites in Black Hawk County, Iowa, and 80 of them were examined in detail. The wedges average 105cm in width at their tops and about 190cm in depth. Infilling material is mostly sand, with pockets of silt, silty sand, and gravelly sand. Slump and subsidence features were also noted in some wedges. Loamy sediment about 1 m thick, with a stone line at its base, overlies the sediment‐filled wedges and usually descends slightly into their upper parts.Based on their characteristics, these sediment‐filled wedges are interpreted as ice‐wedge casts. Supportive palaeoenvironmental studies in Iowa and adjacent states indicate that tundra conditions probably existed in places between 21,000 and 16,500 years BP, the coldest part of late Wisconsinan time. Mean annual air temperatures at this time may have been at least 14°C colder than at present. The degradation of permafrost and formation of ice‐wedge casts must have occurred near the end of this episode of cold climate, which also promoted extreme erosion of the landscape in north‐east Iowa. Aeolian and slopewash deposits later buried the erosion surface and the ice‐wedge casts.
Permafrost in china: Past and present
Authors: Guoqing Qiu , Guodong Cheng 
Published: February 2007

AbstractPermafrost regions occupy some 2,150,000 km2 or 22.4% of the territory of China. The distribution characteristics are closely related to variations in climatic conditions. The permafrost area has changed since the Late Pleistocene. In north‐eastern China, the southern limit of permafrost extended to latitude 41‐42.N during the coldest stage of the Last Glaciation; in the Holocene Megathermal the southern limit retreated northwards. But the ice‐wedges and permafrost that formed in the Late Pleistocene are still present in the northern part of Mt Da‐Hingganling. The finding of inactive ice‐wedges at Yitulihe indicates a colder climate and an enlargement of permafrost during the Late Holocene. With these climate changes, the lower limit of high‐altitude permafrost in the alpine and plateau regions of western China moved up 800‐1000 m, but most of the high mountains and plateaux still remain periglacial.
Suprapermafrost groundwater seepage in gravelly terrain, resolute, NWT, Canada
Authors: Woo Ming‐Ko , Xia Zhaojun 
Published: February 2007

AbstractGravel terrain in the polar desert region of Arctic Canada supports many features such as saturated zones, wetlands, ponds and streams, all of which are associated with local seepage of suprapermafrost groundwater. Gravels have high specific yield and large hydraulic conductivity to facilitate water flow, but a shallow frost table prevents deep percolation so that, given adequate water supply from snowmelt or rainfall, seepage will occur where the topographic surface intersects the water table. Such seepage can be seen on concave slopes to produce local saturated zones. Where seepage is focused, wetlands, ponds and small streams are maintained. Water balance computation for a wetland and a pond shows that seepage from their upslope gravel zones is a major water source. Continual seepage alters the soil, vegetation and moisture characteristics of the site, and the resulting thermal and hydrological feedbacks perpetuate the various features discussed.
Mountain permafrost and slope instability in the Italian Alps: The Val Pola Landslide
Authors: Dramis F. , Govi M. , Guglielmin M. , Mortara G. 
Published: February 2007

AbstractIn July 1987 a landslide affected the Val Pola (Central Alps, Italy) causing several casualities and severe damage. The main conditioning and triggering factors for the huge debris avalanche are described and possible mechanisms are suggested. Present‐day high‐mountain periglacial conditions (such as rock glaciers) present in the area highlight the probable role played by the presence of mountain permafrost in triggering the slope instability.
Quelques Coupes Caractéristiques dans les Dépǒts de Versant d'Aquitaine Septentrionale: Fades et Interprétation Dynamique
Authors: Ozouf J.‐C. , Texier J.‐P. , Bertran P. , Coutard J.‐P. 
Published: February 2007

AbstractLes auteurs présentent et discutent quelques coupes caractéristiques des dépǒts de versant d'Aquitaine septentrionale. A l'ouest de la région, dans les Charentes, s'observent principalement des grèzes litèes liées au fonctionnement de nappes coulées de solifluxion. Plus à l'est, en Périgord, ce type de dépǒt est très rare. En revanche, les faciés y sont beaucoup plus diversifiés et réultent de processus variés: coulées de solifluxion à front pierreux, coulées de solifluxion ‘en blocs’ ou sous pelouse, éboulis gravitaires, coulées sèches, flots de débris, flots de boue. Ces différences s'expliquent principalement par une plus grande diversité des roches mères et un relief plus vigoureux en Périgord.
The Lorraine Grèzes Litées Deposits
Authors: Deshaies M. , Ghanini S. , Harmand D. , Weisrock A. 
Published: February 2007

AbstractDes dépǒts stratifiés de grèzes litées sont décrits dans des sites voisins de Tilly‐sur‐Meuse et Domrémy‐la‐Pucelle. Les matériaux proviennent du substratum local. Il y a un déficit de fines dans ces formations et le ruissellement est considéré comme le processus de dépǒt le plus probable.
Le litage des Éboulis Stratifiés Cryonivaux en Gaspésie (Québec, Canada): Rǒle de la Sédimentation Nivéo‐Éolienne et des Transits Supranivaux
Authors: Hétu Bernard 
Published: February 2007

AbstractDes cõnes d'éboulis stratifiés cryonivaux évoluent actuellement, sous climat tempéré froid, dans des enclaves de l'étage forestier gaspésien (Québec, Canada). Un suivi des processus a permis d'identifier les étapes de la stratogenèse. Les principaux aspects examinés sont: (a) le rǒle respectif des processus impliqués dans la stratogenèse, en particulier les processus de remaniement syn/épigénétiques; (b) la caractérisation de la signature sédimentaire propre à chacun des processus. Elle permet leur identification en coupe. Seule la partie inférieure des cǒnes d'éboulis est clairement stratifiée. Les coupes alternent quatre types de lits: (1) des couches de fines plaquettes d'argilite (de la taille des grèzes) qui se déplacent par saltation à la surface du manteau nival lors des blizzards; (2) des couches de sables moyens à grossiers dérivant des manteaux nivéo‐éoliens associés aux vents d'intensité modérée; (3) des couches openwork constituées de grosses plaquettes imbriquées résultant de glissements supranivaux; (4) des couches diamictiques qui correspondent à des laves boueuses supranivales. Il n'y a aucune périodicité saisonnière stricte dans la mise en place des lits. Comme la plupart des transferts de débris se font sur la neige, la majorité des caractéristiques de faciès observées dans les coupes sont acquises lors de la fonte des neiges, auxquelles s'ajoutent les effets de la reptation, du splash et des percolations de saison chaude. Que ces éboulis stratifiés évoluent actuellement dans une région tempérée forestière montrent que des conditions périglaciaires rigoureuses ne sont pas nécessaires à leur développement.
Recent climatic trend and thermal response of permafrost in Salluit, Northern Quebec, Canada
Authors: Wang Baolai , Allard Michel 
Published: February 2007

AbstractNot all places may in fact warm under global change scenarios. This paper presents an example of climatic cooling from northern Quebec, Canada. Ground temperature measurements along the southern shore of Hudson Strait, northern Quebec indicate a cooling trend over the last seven years (1987‐93). Long‐term air temperature records show that this area has actually experienced continuous cooling for more than 40 years. Related studies suggest that the cooling is likely to continue due to freshening of subpolar water in the North Atlantic and Labrador Sea area. A one‐dimensional geothermal model was used to simulate the effect of continued cooling on permafrost thermal regime in Salluit, northern Quebec. The results show that, if the climatic trend continues for the next 50 years, the thickness of the active layer would decrease by 30cm (from 2.3 to 2.0 m) in gneiss and by 20cm (from 1.3 to 1.1 m) in till. Permafrost temperature at 20 m depth would decrease by 0.65 °C. Under the cooling scenario, rate of permafrost creep and slope activities would be reduced. Ice‐wedge regrowth would continue, and the buried ice wedges may even become reactivated. The results also indicate that regional snow precipitation data cannot be used directly in predicting ground thermal regimes.
The chronology of upper pleistocene stratified slope‐waste deposits in central Italy
Authors: Coltorti M. , Dramis F. 
Published: February 2007

AbstractStratified slope‐waste deposits are widespread in central Italy, even at elevations close to the present coastline. They are evidence of the cold climatic conditions which affected the area during the cold stages of the Upper Pleistocene. Their occurrence was strongly influenced by bedrock lithology (they are common on slopes composed of micritic and marly limestone). Detailed morphostratigraphic analysis and 14C dating of alluvial and inter‐fingered slope‐waste deposits in a mountain area of the Umbria‐Marche Apennine (Upper Esino River basin) allows an outline of the chronological sequence of debris depositional phases during the Late Pleistocene. A few dates were also obtained from the Ponte di Crispiero sequence (in the contiguous Potenza River basin), which may be considered as a type section for the Late Pleistocene of Central Italy, Adriatic side. The stratified slope‐waste deposits were deposited after 50,000 to 60,000 years BP, in the Stadials of the Middle and Upper Pleniglacial. During the Interstadials, most of the slopes of the basin were colonized by steppe vegetation and the production of stratified debris was probaby restricted to the highest elevations. Increased rates of debris deposition occurred during the Upper Pleniglacial.
Microbial life in permafrost: A historical review
Authors: Gilichinsky D. , Wagener S. 
Published: February 2007

AbstractThis paper reviews the literature on cold‐adapted micro‐organisms which might exist in ice and permafrost. Properly identified, microbial markers in the cryolithozone could be used in palaeoenvironmental reconstructions, in distinguishing between epigenetic and syngenetic depositional sequences, and in the recognition of secondary thaw unconformities. Cryobiological problems include (1) whether the bacteria are dead, dormant or in the active state, and (2) what factors determine the preservation of cell structures. A possible consequence of permafrost thawing, based upon predicted global warming scenarios, is that there may be an increase in microbial activity and an increase in active layer thickness.
A note on rock glaciers in the Albanian Alps
Authors: Palmentola G. , Baboci K. , Gruda G. J. , Zito G. 
Published: February 2007

AbstractIn the Albanian Alps, above 1700 m a.s.1., sixteen inactive rock glaciers have been identified, all colonized by herbaceous vegetation. Assuming a −2°C isotherm for the activity of rock glaciers, and after calculating the atmospheric lapse rate, it is estimated that thermal conditions must have been 6.4°C lower than the present mean annual temperature. Because rock glaciers occupied surfaces covered by ice during the periglacial Würm period, they cannot be older than 14,000‐17,000 years; so they are probably referable to the Dryas. Such a temperature drop took place probably during the Dryas.
Gelifluction in the alpine periglacial environment of the Tianshan Mountains, China
Authors: Gengnian Liu , Heigang Xiong , Zhijiu Cui 
Published: February 2007

AbstractGelifluction in the periglacial zone of the Tianshan Mountains occurs at 2500‐3600 m above sea level on north‐facing slopes. Abundant groundwater, fine grained sediments and slopes 10°‐30° favour gelifluction. Most gelifluction forms are lobate, a few are tongue‐shaped. The mean surface rate of movement is 11.14cm/a; the front advancing rate is 1.86cm/a. The moving rate in the middle part is greater than at the sides of gelifluction lobes, the mean rates being 3.1 cm/a and 0.86cm/a, respectively.
Permafrost microbiology
Authors: Gilichinsky D. A. , Wagener S. , Vishnevetskaya T. A. 
Published: February 2007

AbstractNumerous and various ecological and morphological groups of viable micro‐organisms survive under permafrost conditions. They are the only known living organisms preserved over a geologically significant time. Their preservation within permafrost is of interest from both biological and geocryological points of view and forms the basis for a number of investigations in different scientific fields. The latter are performed not only upon morphological but also upon functional characteristics of viable cells. This approach is relevant to questions concerning the protective properties of unfrozen water and may provide new ways of solving major problems of historical geocryology. Of special interest is the interaction of both biological and geological knowledge to better understand the spatial and temporal limits of the biosphere.
The geochemical paradox of ice‐complex sediments in north Siberia
Authors: Konishchev V. N. , Plakht I. R. 
Published: February 2007

AbstractIcy silty deposits in northern Siberia, here termed ‘ice‐complex sediments’ (ICS), have a higher salinization than other continental deposits of Neogene‐Pleistocene age. Data for salinity (%) and the ratio of Ca ion content to Cl ion content for samples from the Yana‐Indigirskaya and Kolymskaya lowlands indicate that the salinization of Pleistocene permafrost is lowest, that icy silts have salinities between 0.1% and 1.0%, and that recent floodplain, coastal and alas deposits have salinities greater than 1%. These differences are thought to reflect the phase change in gas‐liquid inclusions in crystals and rocks when they break and their contents (solutions) are released during freezing. This process is termed cryocryptogenesis. It is concluded that ICS deposits were formed under less humid and colder conditions than exist today in northern Yakutia, but more humid than central Yakutia.