On the possibility of cyclic recurrence of ice ages during the Neogene
Author investigates the possibility of cyclic recurrence of ice during the Neogene. Firstly, the main concepts regarding the reasons behind the emergence of ice ages are discussed and evaluated. Then author concentrates on the main triggers of ice
Basal ice samples were collected from ice exposures in a natural subglacial cavity beneath an outlet glacier of Øksfjordjøkelen. Sediment and cation concentrations were then determined. The results contribute new data from a glacier flowing over
mafic bedrock, and are utilized to investigate the potential for differentiating between firnification ice and ice formed at the bed, and to find if water movement directions can be determined.
Ice segregation and gas distribution in permafrost using tomodensitometric analysis
Canada ; Cold area ; Core sampling ; Ice ; Natural gas ; Permafrost ; Quebec ; Research technique
This paper presents the application of an innovative and non-destructive approach that makes use of a tomodensitometric scanner to image and characterize permafrost : ice lenses, soil layers, faults, sedimentary structures, gas bubbles. The shape
and spatial distributions of gaseous inclusions in the permafrost provide some clues on gas source and on the thermo-mechanics of ice segregation during permafrost aggradation.
The aim of the present paper is to describe the spatial and temporal diversification of ice characteristics concerning. The observations were carried out in Jamno, Bukowo, Gardno and Łebsco lakes. Characterized were the following features concerning
the ice phenomena : date of the appearance of the first ice, the maximum ice thickness, the frequency of their occurence, the trends, and some phenomena of ice covers deformation on. The observations mainly originate from the period of 1960/61 - 1999/2000
Effects of volumetric ice content and strain rate on shear strength under triaxial conditions for frozen soil samples
Creep ; Experimentation ; Ice ; Impact ; Periglacial features ; Permafrost ; Research technique ; Rock glacier ; Shear stress
A set of triaxial constant strain rate and constant stress tests was performed on artificially frozen soil samples to study the effect of the volumetric ice fraction, strain rate and also confining stress on the mobilized shear strength. In general
, the peak shear strength increased with decreasing volumetric ice content and increasing strain rate. The tests showed the dependency of the mechanical failure and deformation mode of frozen soils on the loading conditions. Such investigations
on artificially frozen soils samples may help in developing a better understanding of rock glacier and general permafrost dynamics at temperature close to the melting point of ice.
Alaska ; Cold area ; Cryoturbation ; Ground ice ; Ice wedge ; Periglacial features ; Permafrost ; Thermokarst
This paper describes the various cryostructures and other ice bodies that can be observed within the tunnel. The AA. expand the geocryological literature by suggesting that, during syngenetic permafrost growth, there could have been episodes
of localized thermokarst erosion that would have operated preferentially along ice wedges leading to the development of gullies and tunnels in the near-surface sediments. The local thaw unconformities that result are inferred by the recognition of thermokarst
-cave ice (poolice), and various soil and ice pseudomorphs. These may be regarded as further characteristics of syngenetic permafrost growth.
Mass balance and area changes of four High Arctic plateau ice caps, 1959-2002
Aerial photography ; Arctic Region ; Canada ; Climatic variation ; Cold area ; Ellesmere ; Glacier ; Glacier mass balance ; Glacier retreat ; Global Positioning System ; Ice sheet ; Northwest Territories
The AA. report the results of recent mass balance and GPS area measurements on 4 small stagnant plateau ice caps located on the Hazen Pateau of Ellesmere Island, Nunavut, Canada, from 1999-2002. They compared these measurements with topographic maps
and aerial photography from 1959 and with previously published data. The ice caps reached a Holocene maximum and were several times larger during the Little Ice Age (LIA) and their current recession reflects an adjustment to post-LIA climatic conditions.
The characteristics and formation of a High-Arctic proglacial icing
This paper describes the morphology and infers the process of formation, of a proglacial icing in Svalbard. The study glacier, Scott Turnerbreen, with an altitude range of 230-680 m a.s.l., is located in central Spitsbergen.
A field perspective on modelling single ridge ice-wedge polygons
Climatic variation ; Cold area ; Ice wedge ; Model ; Numerical model ; Palaeo-environment ; Periglacial features ; Polar region
criticisms focus on : the implications of trough evolution for cracking behaviour; the extent to which epigenetic, low-centred polygons represent the population of ice-wedge networks; and the modelled initiation of polygons in drained thaw lakes.
Permafrost and Little Ice Age glacier relationships, Posets Massif, Central Pyrenees, Spain
Geophysics ; Glacier ; Ground survey ; Little ice age ; Mountain ; Periglacial features ; Permafrost ; Pyrénées ; Spain ; Stratigraphy
This paper contributes to the study of permafrost in the Pyrenees by reporting geoelectrical investigations and thermal measurements on the Little Ice Age (LIA) forefields of 2 glaciers. The aim was to assess the internal composition of sedimentary
bodies (debris rock glaciers and moraine deposits) located in this proglacial environment. Ground ice was propected using 2 DC (direct current) resistivity techniques. Results from the Posets and La Paul glaciers forefields are presented here
Effects of the Little Ice Age on avalanche boulder tongues in the French Alps (Massif des Ecrins)
Alpes du Sud ; Avalanche ; France ; Glacial features ; Hautes-Alpes ; Lichenometry ; Little ice age ; Palaeo-ecology ; Palaeo-environment
Lichens of the subspecies Rhizocarpon geographicum were measured on 25 avalanches boulder tongues in the Massif des Ecrins to elucidate the Little Ice Age history of avalanche activity. According to the results, the avalanche activity
was at a maximum before AD 1650 and between AD 1730 and 1830. The relatively good correspondence between avalanche boulder tongue and glacier behaviour in the Massif des Ecrins to climatic variation which occurred since the Little Ice Age confirms that avalanche
Re-dating the moraines at Skálafellsjökull and Heinabergsjökull using different lichenometric methods : implications for the timing of the Icelandic Little Ice Age maximum
Climatic variation ; Dating ; Geochronology ; Glacier ; Glacier fluctuation ; Iceland ; Lichenometry ; Little ice age ; Moraine ; Nineteenth Century
During 2003, 12 000 lichens were measured on 40 moraine fragments of both glaciers to provide surface age proxies. The results reveal that the choice of lichen dating curve has a significant impact on the estimated timing of Little Ice Age (LIA
) maxima. An early to mid-19th century LIA maximum at both glaciers, as determined in this study, accords well with other emerging evidence (Icelandic geochronology reconstructions, sea-ice and NAO records). This indicates that the often-cited late 19th
Relict shorelines and ice flow patterns of the northern Puget Lowland from lidar data and digital terrain modelling
on the uplift pattern in the northern Puget Lowland. The AA. provide height information from lidar data of sea level indicators along a transect oriented N-S, roughly parallel to the direction of ice movement. In addition, they present geomorphic information
that relates to the ice flow directions of these islands to provide information of the melting history of ice in this area.
The retreat of Tien Shan glaciers (Kyrgyzstan) since the Little Ice Age estimated from aerial photographs, lichenometric and historical data
Aerial photography ; Climatic variation ; Geomorphological map ; Glacier ; Glacier retreat ; Historical geography ; Kyrgyzstan ; Lichenometry ; Little ice age ; Map ; Moraine ; Tien Shan ; Years 1980-89
The retreat of 293 glaciers in the Tien Shan Mountains from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25 000, constructed during period 1956-1990. Two
indices of changes are used : the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s
Identification of mapped ice-margin positions in western New York from digital terrain-analysis and soil databases
This study identifies inconsistencies in ice extent in the Salamanca Re-entrant western New York as mapped using soil properties and surficial geology. The A. uses a raster-based approach to extract the soil pH, silt, and clay contents from digital
differences, suggesting that a GIS analysis of former ice margins is a productive preliminary step to their precise delineation.
Diatom assemblages and organic carbon records from 2 sediment cores located within an estuarian bay of the inner Kara Sea trace changes in Yenisei River runoff and postglacial depositional environments. Paleosalinity and sea-ice reconstructions
, and ice conditions in the seas of the Eurasian arctic shelf.