bluuebunny/crossref_metadata_2025_split huggingface dataset:
A statistical analysis of the spatial distribution of rock glaciers, Spanish Central Pyrenees
Authors: Chueca J. 
Published: February 2007

AbstractOne hundred and seventy rock glaciers have been identified by use of aerial photographs in the southern Central Pyrenees. Through the use of statistical techniques (quadrat analysis, Poisson distribution analysis and variance‐mean ratio test), differences in lithology and fracturing density are shown to be important controls over their distribution.
The fractal geometry of thermal and chemical time series from the active layer, Alaska
Authors: Outcalt Samuel I. , Hinkel Kenneth M. 
Published: February 2007

AbstractTwo data sets were used to examine the fractal geometry of constituent time series. Soil temperature and soil water ionic concentration observations were collected in August 1991 at proximal sites at the Caribou‐Poker Creeks Research Watershed near Fairbanks, Alaska. The second data set contains thermal records of the 1984 active layer freezeback from Toolik Lake. Following Fourier transformation, log (variance) was plotted as a function of log (wavelength) and three parameters were generated: the exponent (S) of the power law fit to the variance spectrum, the Hausdorff‐Besicovitch Dimension (Dhb) and the Coefficient of Determination (R2). This procedure measures both the degree of roughness of a time series (Dhb) and the degree to which the time series approaches a ‘pure’ fractal condition (R2 = 1.0). The Caribou‐Poker Creeks data set demonstrates that time series from different microenvironments can be discriminated in (R2, S) space. The thermal records from Toolik Lake show that, during formation of the isothermal ‘zero curtain’ layer, heat transfer is accomplished primarily by non‐conductive processes. The zero‐curtain effect is characterized by a ‘pink noise’ spectrum with strong cyclic elements, an increase in Dhb and a corresponding decrease in R2. The methods were applied here to a single probe, but confirm previous analyses employing apparent thermal diffusivity calculations and spectral comparisons requiring data from multiple levels.
Pleistocene periglacial structures and landforms in Western Czechoslovakia
Authors: Czudek Tadeáš 
Published: February 2007

AbstractThe paper describes periglacial structures and landforms developed under Pleistocene coldclimate conditions in western Czechoslovakia. The thickness of Upper Pleistocene permafrost in this territory may have been between 50 and 250 m. Climatically controlled valley asymmetry developed because of different cryogenic processes on opposite valley sides and lateral stream migration (mainly due to thermal erosion). In some cases cryopediment‐like foot‐slopes developed due to down‐wearing of river terraces and/or to the combined effect of down‐wearing and back‐wearing.
Climate warming and the carbon cycle in the permafrost zone of the former Soviet Union
Authors: Kolchugina Tatyana P. , Vinson Ted S. 
Published: February 2007

AbstractThe continuous permafrost zone of the former Soviet Union (FSU) occupies 5% of the land surface area of the earth and stores a significant amount of carbon. Climate warming could disrupt the balance between carbon (C) accumulation and decomposition processes within the permafrost zone. Increased temperatures may accelerate the rate of organic matter decomposition. At the same time, the productivity of vegetation may increase in response to warming. To assess the future carbon cycle within the permafrost zone under a climate‐warming scenario, it is necessary to quantify present carbon pools and fluxes. The present carbon cycle was assessed on the basis of an ecosystem/ecoregion approach. Under the present climate, the phytomass carbon pool was estimated at 17.0 Gt (109 t). The mortmass (coarse woody debris) carbon pool was estimated at 16.1 Gt. The soil carbon pool, including peat‐lands, was 139.4 Gt. The present rate of carbon turnover was 1.6 Gt/yr. Under a warming climate 0.46–0.72 Gt C/yr may be gradually released to the atmosphere, mainly due to the increase in mortmass and litter decomposition. The increased efflux may be concurrently balanced by carbon uptake by vegetation as a result of enhanced productivity and forest migration to the north. However, the possibility exists that a lag between increased carbon efflux and uptake by vegetation may occur. The equilibrium of the carbon cycle may be reestablished, but at a higher rate of carbon turnover. Climate warming may not influence the depth of the active layer in peatlands. The depth of the active layer in mineral soils was comparable with the depth of the organic layer. Consequently, degradation of permafrost may not have a substantial influence on future carbon emissions.
Données Nouvelles sur la Présence d'un Pergélisol en Aquitaine au cours des Dernières Glaciations
Authors: Texier J. P. , Bertran P. 
Published: February 2007

AbstractLes formes cryergiques identifiées en Aquitaine montrent que cette région de France a vraisemblablement été affectée par le développement d'un pergélisol. Celui‐ci se serait manifesté au cours de deux épisodes climatiques distincts: l'un daterait de la partie supérieure du dernier Pléniglaciaire (Dryas ancien); l'autre, plus hypothétique, se situerait dans la deuxième moitié de l'avant dernier Glaciaire. Le type de ces pergélisols ne peut être défini avec une totale certitude. Par rapport à l'actuel, la baisse de température moyenne annuelle de l'air peut être estimée entre 13 et 19°C.
Description and origin of some talus‐foot debris accumulations, Aghla Mountains, Co. Donegal, Ireland
Authors: Wilson Peter 
Published: February 2007

AbstractThe morphology and site characteristics of talus‐foot debris accumulations in the Aghla Mountains, Ireland, suggest that these landforms are fossil protalus ramparts and talus‐derived rock glaciers. The ramparts are linear or arcuate ridges or benches located within 45 m of the talus foot. The rock glaciers comprise several transverse ridges and depressions, interpreted as flow structures, and extend further from the talus foot than the ramparts. At least one rock glacier developed from a rampart. The ramparts indicate the former existence of perennia snowbeds and the rock glaciers are considered to result from the deformation and creep of interstitial ice (permafrost). There is no clear evidence of large scale‐slope failures or glacier ice having influenced debris accumulation. The landforms are probably of Nahanagan Stadial age (c. 11‐10 ka BP) and testify to the susceptibility of well‐jointed quartzite cliffs and talus to significant modification under the severe climatic regime of the stadial.
A low‐angle slushflow in the Kirgiz Range, Kirgizstan
Authors: Elder K. , Kattelmann R. 
Published: February 2007

AbstractA rare observation of a slushflow that released on a low‐angle slope was made on 16 May 1992 in the West Karakol Valley, southern Kirgiz Range, Kirgizstan. The slushflow released on a short slope of 6° and travelled a distance of 140 m over a slope with a mean angle of 3° with a mean channel width of about 4 m. Total volume of snow and slush transported by the slide was more than 200 m3 with an estimated mass of 200,000 kg. Estimated velocity of the flow was 5 ms−1. Meteorological conditions preceding the event included heavy cloud cover and clear skies with warm temperatures. Rain fell for about six hours during the day before the event. Mixed rain and snow precipitation continued through the preceding night accompanied by steady high winds. The day of the release was warm with overcast skies and light rain. The snowpack was generally saturated to the surface at the time of the release, and water was flowing over the snow surface in the path of the slushflow.
Notes on open‐system pingo ice, Adventdalen, Spitsbergen
Authors: Yoshikawa Kenji 
Published: February 2007

AbstractAnalysis of open‐system pingo ice in Adventdalen, Spitsbergen, reveals its growth process. Ice and water sampled from edge to centre and from top to bottom of open‐system pingos are analysed. The results suggest that, after the underground water supply stopped, pingo ice extended downward. This downward extension seems to lower the level of underground water. The growth of open‐system pingo ice is supported by injecting and/or segregating ice originated from underground water. Sea level and climate changes probably influence the underground water level. This is especially the case for pingos formed on the coastal plain.
Gravimetrical investigation of ice‐rich permafrost within the rock glacier Murtèl‐Corvatsch (upper Engadin, swiss alps)
Authors: Vonder Mühll Daniel S. , Klingelé Emile E. 
Published: February 2007

AbstractA gravimetrical study was carried out in the area of the Murtèl‐Corvatsch rock glacier in order to check the applicability of this method in alpine permafrost. The residual anomaly observed after removal of the linear regional trend is up to −1.5 mgal. Cores of borehole 2/1987 through this rock glacier showed a very high ice content in the uppermost 30 m. Borehole geophysical measurements furnished the density distribution with depth at the drill site showing values of less than 1000 kg m−3. According to the core stratigraphy and the density log at the drill site four layers were distinguished: an active layer to 3 m depth; massive ice (3–20 m); an ice‐silt‐sand layer (20–30 m); and a layer with ice‐saturated blocks (30–50 m). The extension of the four distinguished layers is modelled in three dimensions for the entire rock glacier according to the gravity data. The bedrock underneath the creeping permafrost is bowl‐shaped.
Rheological models of active rock glaciers: Evaluation, critique and a possible test
Authors: Whalley W. Brian , Azizi Fethi 
Published: February 2007

AbstractRheological properties of ice and ice/rock‐fragment mixtures relating to rock glaciers are examined. The basic criteria for flow (neglecting sliding components) are discussed with reference to published work. Even if the internal composition of a rock glacier is very variable, ranging from pure ice to an ice/rock mixture, then similar surface velocities are likely to be measured and accounted for by at least two rheological models. Under some circumstances, even when there is ice in excess of the rock debris voids ratio, flow of the frozen material may not be possible. Uncertainty in the ice/debris composition in rock glaciers allows a wide variety of temperature, density, shear strength and creep properties to account for measured velocities. Ice lenses (segregation ice) must interconnect within a surrounding mass of stronger material for substantial deformation to occur. It is suggested that a glacier ice origin can account for the measured surface flow velocities of rock glaciers as long as the ice body is thin, generally <50m. It is usually considered that low flow velocities of rock glaciers are distinctive; however, previous conditions may have shown much greater surface velocities than at present. A test for the origin of rock glaciers is given based upon flow mechanical properties. If a rock glacier had its origin as a glacier then past velocities would have been higher than at present; if as a permafrost body, then there should not have been a major decrease. Evidence is presented to show that the latter may be the case in some instances.
Periglacial landforms at Giant'S Castle, Natal Drakensberg, South Africa
Authors: Boelhouwers Jan C. 
Published: February 2007

AbstractActive and inactive periglacial landforms are described for a small, south‐facing mountain catchment at Giant's Castle, 3140–3300 m A.S.L. Natal Drakensberg, South Africa. Micro‐patterned ground is found at the water divide and indicates marginal present‐day frost activity with soil frost penetration to a depth of 0.1–0.2 m. Downslope, thin stone‐banked sheets migrate over larger, inactive, stone‐banked lobe complexes. Block fields, suggested to be of a gelifluction origin, occupy the central part of the valley and gelifluction sheets cover the lower valley slopes. All are inactive. The range of inactive periglacial slope deposits suggests the presence of severe seasonal frost in the past.
Evidence for a cyclic variation of permafrost temperatures in northern alaska
Authors: Osterkamp T. E. , Zhang T. , Romanovsky V. E. 
Published: February 2007

AbstractObservations of permafrost temperatures in shallow drill holes in northern Alaska near the Beaufort Sea coast show that these temperatures have cycled during the decade from 1983 to 1993. The two sites nearest the coast indicate a period of about 10 years and an amplitude at the permafrost surface of about 2°C. The two sites farthest from the coast have similar periods but reduced amplitudes of about 0.6°C. Changes in air temperatures, snowfall, length of sea ice season, solar effects, and other factors could, in principle, produce the observed temperature changes. Barrow air temperatures have a periodicity of 10.1 years but currently lead the sunspot cycle. Snowfall also shows evidence for a periodicity near 10 years. Near Prudhoe Bay, the length of the sea ice season increased about one week from 1979 to 1986 which could have caused a decrease in coastal air temperatures. The sunspot cycle (10–11 year period) leads temperatures at the 30 m depth by two to three years which is about the expected lead. During the descending part of the last solar cycle, satellite measurements of the solar total irradiance showed a decrease of about 3W m−2, which is about four times the calculated mean energy flux at the permafrost table (0.6 to 0.7 W m−2) required to produce the observed temperature changes.
Glaciological constraints on protalus rampart development
Authors: Ballantyne Colin K. , Benn Douglas I. 
Published: February 2007

AbstractThe growth of protalus ramparts is self‐limiting, as progressive thickening of a firn field will increase basal shear stress, encouraging creep of ice and basal sliding, and thus cause the transformation of stationary firn into a small glacier with consequent destruction or modification of the rampart. Modelling of the threshold conditions under which significant movement of the firn field begins indicates that the maximum distance between the rampart crest and the talus foot upslope cannot exceed c. 30–70 m, the limiting value being dependent on the gradient of the firn field. This finding implies that ridges or ramps of debris lying at greater distances from the talus foot cannot be [true] protalus ramparts formed by debris descending an essentially stationary firn field, and hence that many landforms previously described as protalus ramparts have been misinterpreted. Modelling of the limiting conditions for gravitational transport of debris suggests that clasts may continue to reach the front of a steep incipient glacier even after ice movement has been initiated, at least until the toe of the ice reaches a position 85–125 m from the talus foot. This implies the possible existence of [protalus moraines] whose form is influenced by moving ice, yet which continue to receive a supply of debris by direct gravitational transport across the ice surface.
Protalus ramparts and related features along the niagara escarpment, niagara peninsula, ontario
Authors: Tinkler K. J. , Pengelly J. W. 
Published: February 2007

AbstractTalus foot ridges interpreted as protalus ramparts have been identified along 17 out of 42 km of the Niagara Escarpment within the Niagara Peninsula. They are distinguished from various types of slope form (rotational slumps, debris slides, quarries, dumps, moraines, raised shorelines and bedrock ledges) by their regular linear nature and their restriction to slopes facing between north‐east and north‐west. Morphologies range from a simple terrace with a flat top and a steep rocky outer slope, to compound ridges with closed depressions between. Maximum widths from rampart crest to main talus foot average 25 metres. Ramparts are characteristically extremely bouldery and include angular blocks of Thorold and Grimsby Sandstones weathered from the Escarpment slope, Ironde‐quoit Limestone and Lockport Dolomite blocks with metre dimensions transported to the outer slopes of the ramparts from the upper edge of the Escarpment, and clay from the weathering of Escarpment shales and from Wisconsinan diamictons. Associated firn field dimensions probably fluctuated dramatically in size during the year, and the palaeoclimatic implication is that there existed substantial late‐lying to perennial firn fields following local deglaciation at 12.5 ka BP. Independent confirmation of an early postglacial tundra climate is provided by the basal portions of pollen stratigraphies obtained nearby. The latest period when the firn fields might have existed is during the Younger Dryas chronozone (11 ka to 10.0 ka BP) when regional climatic cooling may have allowed the re‐establishment of a tundra‐like climate, especially in areas with severe microclimates.
Changes in hydrogeologic regimes in permafrost regions due to climatic change
Authors: Michel Frederick A. , Van Everdingen Robert O. 
Published: February 2007

AbstractThe general and specific effects of predicted climate change on groundwater systems in permafrost regions are summarized. Besides a general decrease in the thickness and areal distribution of permafrost, a large unfrozen near‐surface aquifer with perennial groundwater flow might develop. Recharge and discharge would become more active and increased groundwater discharge would affect the baseflow of many rivers and the chemistry of their waters.
Identification of heat‐transfer processes during soil cooling, freezing, and thaw in central alaska
Authors: Hinkel Kenneth M. , Outcalt Samuel I. 
Published: February 2007

AbstractHourly time series of temperature and a surrogate measure of the soil water ionic (solute) concentration were obtained in the upper 50 cm of soil from two adjacent sites in central Alaska from August 1991 to May 1992. One site is located in a ground water seepage zone and is characterized by seasonal freezing of the upper soil. The other site is located over a body of permafrost. The time series, used simultaneously, display a unique signature diagnostic of the operative conductive and non‐conductive heat‐transfer process. During soil cooling in autumn, internal distillation (concurrent evaporation, vertical transport, and condensation of water vapour in soil column) moderates heat transfer in the active layer. A [zero curtain] develops in winter and persists for three months; maintenance of this isothermal layer is associated with water advection and internal distillation within the unfrozen zone. Conductive heat transfer is not possible in the isothermal layer during this period but dominates during late winter following soil freezing and closure of the zero curtain. Warming of the active layer in spring occurs nearly instantaneously and results from infiltration of snow cover meltwater and downward vapour migration. In contrast, water saturation of pore space at the seepage site inhibits vertical migration of vapour and water.
Sublimation as a geomorphic process: A review
Authors: Law Jane , Van Dijk Deanna 
Published: February 2007

AbstractIce and snow sublimation is a naturally occurring process in which the solid ice changes state to become a vapour without passing through the usual liquid stage. The sublimation of blowing snow can be critical in areas which rely on melting snow as an important source of moisture. In blowing snow, the sublimation process is influenced by air temperature, relative humidity, wind speed, net radiation and particle surface area. When pore ice sublimation occurs in an ice/sediment mixture, the process is complicated by the presence of the particles of sediment. The sublimation of frozen moisture from sediments has implications for dust production, for human safety in permafrost tunnels, and for the aeolian movement of sediments in cold environments. A limited number of studies have considered sublimation from frozen sediments and a very few of these have been done under field conditions. The variables of air temperature, relative humidity, sediment moisture content and wind speed influence the amount and rate of pore ice sublimation, but there is some disagreement as to the relative importance of these variables.
Snow depth controls palsa growth
Authors: Seppälä Matti 
Published: February 2007

AbstractWhen a young palsa has risen sufficiently above a mire (bog) and has developed steep sides, drifting snow collects against these sides and inhibits freezing of adjacent ground. Measurement of the temperature regime on the top surface, and at the foot, of the northern edge of a 2.6 m high palsa in Utsjoki, Finland supports this hypothesis. The minimum temperature recorded in the winter of 1992–93 on the uncovered palsa summit was −23.4°C. After snowfall, the temperature stayed at +0.1°C at the foot of the palsa for over six months, until 20 June 1993. At the edge of the palsa, thick snow cover prevents the establishment of permafrost.
Systématique du Remplissage en Eau des Fentes de Gel: Les Résultats d'une Étude Oxygène‐18 et Deutérium
Authors: Lauriol B. , Duchesne C. , Clark I. D. 
Published: February 2007

AbstractUne douzaine de coins de glace le long de la rivière Porcupine (Yukon) ont été échantillonnés pour identifier leur période de croissance et pour déterminer l'origine de l'eau qui les a formés. Les datations au radiocarbone des sédiments qui les contiennent limitent leur période de croissance aux 4 derniers millénaires. Les isotopes stables montrent une homogénéité entre les centres et les bordures des coins, indiquant une stabilité climatique durant cette période. Le δ18O/δ2H est enrichi par rapport aux précipitations hivernales et se situe au‐dessous de la ligne des eaux météoriques ce qui laisse penser que les fentes de gel sont remplies durant les derniers moments de la fonte.
Ventifacts as palaeo‐wind indicators in southern Scandinavia
Authors: Schlyter Peter 
Published: February 2007

AbstractSystematic transect and grid surveys of ventifact presence/absence were made in order to assess palaeo‐ventifact abundance/distribution through Denmark and southern Sweden. The transects reveal a continuous ventifact distribution from western Denmark to south‐central Sweden giving evidence for the existence of significant palaeo‐wind action in extensive areas previously thought lacking in such evidence. Based on ice recession dates and vegetation development, ventifact formation is interpreted as having occurred mainly contemporaneously with the receeding Weichselian ice‐sheet. A grid survey in Scania, southern Sweden, demonstrates a continuous ventifact distribution irrespective of surface materials and topography. The ventifact occurrence outside areas with sandy soils indicates that suspended particles were effective abrading agents. Stable ventifacts confirm previous observations of easterly wind abrasion in Scania and exhibit an extremely small directional variability within, and between, sites. Ventifacts in southern Scandinavia are probably more indicative of transitory paraglacial conditions than periglacial conditions as such.
Ice‐wedge formation in northern Asia during the Holocene
Authors: Vasil'chuk Yurij K. , Vasil'chuk Alla C. 
Published: February 2007

AbstractThe cryostratigraphy of Holocene ice wedges is described from Western Siberia, Yakutia and the Trans‐Baikal region. 14C dating and oxygen isotope determinations suggest that some of these wedges grew syngenetically during the Holocene climatic optimum. Inferred mean winter and mean January air temperatures for this period are presented.