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  • International Glaciological Society  (4)
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  • International Glaciological Society  (4)
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  • 1
    Online Resource
    Online Resource
    A groove-ploughing theory for the production of mega-scale glacial lineations, and implications for ice-stream mechanics
    International Glaciological Society ; 2003
    In:  Journal of Glaciology Vol. 49, No. 165 ( 2003), p. 240-256
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 49, No. 165 ( 2003), p. 240-256
    Abstract: Mega-scale glacial lineations (MSGLs) are longitudinally aligned corrugations (ridge–groove structures 6–100 km long) in sediment produced subglacially. They are indicators of fast flow and a common signature of ice-stream beds. We develop a qualitative theory that accounts for their formation, and use numerical modelling, and observations of ice-stream beds to provide supporting evidence. Ice in contact with a rough (scale of 10–10 3 m) bedrock surface will mimic the form of the bed. Because of flow acceleration and convergence in ice-stream onset zones, the ice-base roughness elements experience transverse strain, transforming them from irregular bumps into longitudinally aligned keels of ice protruding downwards. Where such keels slide across a soft sedimentary bed, they plough through the sediments, carving elongate grooves, and deforming material up into intervening ridges. This explains MSGLs and has important implications for ice-stream mechanics. Groove ploughing provides the means to acquire new lubricating sediment and to transport large volumes of it downstream. Keels may provide basal drag in the force budget of ice streams, thereby playing a role in flow regulation and stability. We speculate that groove ploughing permits significant ice-stream widening, thus facilitating high-magnitude ice discharge.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/172756503781830719
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2003
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Geomorphological criteria for identifying Pleistocene ice streams
    International Glaciological Society ; 1999
    In:  Annals of Glaciology Vol. 28 ( 1999), p. 67-74
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 28 ( 1999), p. 67-74
    Abstract: Ice streams are critical regulatory mechanisms in contemporary ice sheets. It has been inferred that they also had a significant effect on the dynamics of former ice sheets. Subsequently, many people have invoked their widespread occurrence from a variety of formerly glaciated areas. Hypothesised locations, however, have often outweighed meaningful evidence. This paper addresses the problem, using the characteristics of contemporary ice streams as a basis for their identification from former ice-sheet beds. A convergence of knowledge gained from contemporary ice-stream research, coupled with theories of glacial geomorphology, allows several geomorphological criteria to be identified as suggestive signatures of ice-stream activity. It is envisaged that the geomorphological criteria developed here will introduce a more objective approach to the study of former ice streams. The criteria are used to construct conceptual land-system models of the beds of former ice streams, and it is hoped such models can provide an observational template upon which hypotheses of former ice streams can be better based.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/172756499781821625
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 1999
    detail.hit.zdb_id: 2122400-6
    SSG: 14
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  • 3
    Online Resource
    Online Resource
    Late-20th-century changes in glacier extent in the Caucasus Mountains, Russia/Georgia
    International Glaciological Society ; 2006
    In:  Journal of Glaciology Vol. 52, No. 176 ( 2006), p. 99-109
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 52, No. 176 ( 2006), p. 99-109
    Abstract: Glaciers occupy an area of ~1600km 2 in the Caucasus Mountains. There is widespread evidence of retreat since the Little Ice Age, but an up-to-date regional assessment of glacier change is lacking. In this paper, satellite imagery (Landsat Thematic Mapper and Enhanced Thematic Mapper Plus) is used to obtain the terminus position of 113 glaciers in the central Caucasus in 1985 and 2000, using a manual delineation process based on a false-colour composite (bands 5, 4, 3). Measurements reveal that 94% of the glaciers have retreated, 4% exhibited no overall change and 2% advanced. The mean retreat rate equates to ~8ma –1 , and maximum retreat rates approach ~38 m a –1 . The largest ( 〉 10 km 2 ) glaciers retreated twice as much (~12ma –1 ) as the smallest ( 〈 1 km 2 ) glaciers (~6ma –1 ), and glaciers at lower elevations generally retreated greater distances. Supraglacial debris cover has increased in association with glacier retreat, and the surface area of bare ice has reduced by ~10% between 1985 and 2000. Results are compared to declassified Corona imagery from the 1960s and 1970s and detailed field measurements and mass-balance data for Djankuat glacier, central Caucasus. It is concluded that the decrease in glacier area appears to be primarily driven by increasing temperatures since the 1970s and especially since the mid-1990s. Continued retreat could lead to considerable changes in glacier runoff, with implications for regional water resources.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/172756506781828827
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2006
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Identification and characteristics of surge-type glaciers on Novaya Zemlya, Russian Arctic
    International Glaciological Society ; 2009
    In:  Journal of Glaciology Vol. 55, No. 194 ( 2009), p. 960-972
    Details
    In: Journal of Glaciology, International Glaciological Society, Vol. 55, No. 194 ( 2009), p. 960-972
    Abstract: We present a comprehensive new inventory of surge-type glaciers on the Novaya Zemlya archipelago, using high-resolution (up to 4 m) satellite imagery from 1976/77 (Hexagon), 1989 (Landsat TM), 2001 (Landsat ETM+) and 2006 (ASTER). A total of 692 glaciers and their forelands were observed for glaciological and geomorphological criteria indicative of glacier surging (e.g. looped moraines, heavy surface crevassing, surface potholes, thrust-block moraines, concertina eskers). This enabled the identification of 32 potential surge-type glaciers (compared with four previously identified) representing 4.6% of the total but 18% by glacier area. We assess the characteristics of surge-type glaciers. Surge-type glaciers are statistically different from non-surge-type glaciers in terms of their area, length, surface slope, minimum elevation, mid-range elevation and terminus type. They are typically long (median length 18.5 km), large (median area 106.8 km 2 ) outlet glaciers, with relatively low overall surface slopes (median slope 1.7°) and tend to terminate in water (marine or lacustrine). They are predominantly directed towards and located in the more maritime western region of the Russian Arctic, and we suggest that surge occurrence might be related to large and complex catchment areas that receive increased delivery of precipitation from the Barents Sea.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.3189/002214309790794940
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2009
    detail.hit.zdb_id: 2140541-4
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
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