Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujolkull, Island OLE ... more Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujolkull, Island OLE HUMLUM ^r r\yyri Humlum, O.: Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujokull, J JJXJP Island, Dansk geol. Foren., Årsskrift for 1982, side 11-26, København, 6. juni 1983.
Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears... more Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. INSTAAR, University of Colorado is collaborating with JSTOR to digitize, preserve and extend access to
Two new concepts relating to rock glaciers are defined: the rock glacier appearance level (RAL) a... more Two new concepts relating to rock glaciers are defined: the rock glacier appearance level (RAL) and the rock glacier initiation line altitude (RILA). The RAL may be regarded as an analogy to the glaciological concept glaciation level (GL) and indicates a critical summit ...
I GeologiskNyt nr. 3 og 4 2008 har Hessbjerg, Henriksen og Hinsby samt Langen indlaeg som modsvar... more I GeologiskNyt nr. 3 og 4 2008 har Hessbjerg, Henriksen og Hinsby samt Langen indlaeg som modsvar til min artikel i GeologiskNyt nr. 2 2008. Det er glaedeligt, at min lille artikel har vakt opmaerksomhed, men det er samtidig lidt skuffende, at ingen af de tre modsvar berører hovedtemaet om forholdet mellem forventet og faktisk temperaturaendring. Modsvarenes grundighed giver imidlertid baggrund for en replik, der tydeliggør, hvori den grundlaeggende uenighed om klimamodellering består. Jeg tager her udgangspunkt i Hessbjergs fokus på CO 2 's betydning.
Monitoring and modelling snow avalanches in Svalbard Ole Humlum 1,3, Hanne H. Christiansen 1, Ulr... more Monitoring and modelling snow avalanches in Svalbard Ole Humlum 1,3, Hanne H. Christiansen 1, Ulrich Neumann 1, Markus Eckerstorfer 1, Anna Sjöblom 1, Knut Stalsberg 2 and Lena Rubensdotter 2. 1: The University Centre in Svalbard (UNIS). 2: Geological Survey of Norway (NGU) 3: University of Oslo Ground based transportation in Svalbard landscape all takes place across mountainous terrain affected by different geomorphological slope processes. Traffic in and around the Svalbard settlements is increasing, and at the same time global climate models project substantial increases in temperature and precipitation in northern high latitudes for coming century. Therefore improved knowledge on the effect of climatic changes on slope processes in such high arctic landscapes is becoming increasingly important. Motivated by this, the CRYOSLOPE Svalbard research project since 2007 has carried out field observations on snow avalanche frequency and associated meteorological conditions. Snow avalanches are important geomorphic agents of erosion and deposition, and have long been a source of natural disasters in many mid-latitude mountain areas. Avalanches as a natural hazard has thereby been familiar to inhabitants of the Alps and Scandinavia for centuries, while it is a more recent experience in high arctic Svalbard. In addition, overall climate, topography and especially high winter wind speeds makes it difficult to apply snow avalanche models (numerical or empirical) developed for use at lower latitudes, e.g. in central Europe. In the presentation we examplify results from the ongoing (since winter 2006-07) monitoring of snow avalanches in Svalbard along a 70 km long observational route in the mountains. In addition, we present observations on the geomorphological impact of avalanches, with special reference to the formation of rock glaciers. Finally, we also present some initial results from numerical attempts of snow avalanche risk modelling within the study area.
The debris-covered ice-margins of three largely cold-based glaciers in central Spitsbergen were i... more The debris-covered ice-margins of three largely cold-based glaciers in central Spitsbergen were investigated to reconstruct their formation and degradation. Clast shapes indicate dominant englacial and supraglacial transport with a smaller subglacial component. Emplacement of material is inferred to have been through meltout along flowlines due to the relatively uniform and continuous debris cover along the glacier margins; no evidence of thrusting has been found. Degradation of all three belts is rapid and involves debris flows at unstable places-e.g., the margins of meltwater channels. Resultant exposure of underlying ice initiates or accelerates melting, thereby leading to further debris flows. Hence, once degradation starts, a self-reinforcing cycle that removes material from the glacier commences. Landform preservation potential on millennial time scales in a high-arctic, continuous permafrost environment is thus limited. This work has implications for the interpretation of Pleistocene landform associations that use modern analogues from Svalbard. 1 The authors would like to thank Dr. Douglas I. Benn for his invaluable input and help in designing and organizing these separate projects. Discussions with him that ultimately improved the quality of the manuscript are greatly appreciated. Dr. Hanne H. Christiansen and the staff at UNIS, Longyearbyen are thanked for local support in Svalbard and numerous enthusiastic discussions. We are grateful to Dr. Arthur S. Dyke and an anonymous reviewer who provided helpful reviews that improved the readability of the manuscript.
Much renewed research interest in Arctic regions stems from the increasing concentration of atmos... more Much renewed research interest in Arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas. Glacier and permafrost changes are among a number of proxies used for monitoring past and present Arctic climate change. Here we present observations on frozen in situ soil and vegetation, found below cold-based glacier Longyearbreen (78813?N), 2 km upstream from the present glacier terminus. Dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c. 1100 years. The meteorological setting of non-surging Longyearbreen suggests this example of late-Holocene glacier growth represents a widespread phenomenon in Svalbard and in adjoining Arctic regions. In addition, we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods, and we present evidence for microbes having survived more than 1100 years in a subglacial, permafrozen state.
Reflections on modern cold-climate landforms and their relation to climate Ole Humlum, University... more Reflections on modern cold-climate landforms and their relation to climate Ole Humlum, University of Oslo, Department of Geosciences The identification of fossil cold-climate landforms is important from a palaeoclimatic point of view. Attempts at reconstructing past cold-climate environments are based mostly on the utilization of certain fossil periglacial and glacial landforms and sedimentary structures, such as ice and sand wedge casts, thermal cracks, fragipan horizons, the systematic occurrence of cryoturbation or solifluction, evidence of strong ice segregation in sediments, fossil rock glaciers, moraines, tills and glacial valleys. Many attempts of palaeoenvironmental reconstruction are based on biological evidence, which tend to reflect summer conditions, rather than winter conditions. In this respect the use of cold-climate landform in palaeoenvironmental reconstructions is potentially important, as many of such landforms often depend on the presence of ice, which tend to reflect winter conditions rather than summer conditions. A number of difficulties, however, immediately arise. As an example, climatic changes resulting in the areal disappearance of ice-rich permafrost beyond the margins of Quaternary ice sheets and glaciers tend to blur or confuse the evidence of previously distinct periglacial and glacial features. Traces of their morphology and relict surface and subsurface structures may, however, still be detected in certain regions. Such fossil forms, especially when dated, can then be used as important indicators of a past climate in the region considered. While geomorphological features such as glacial striae and U-shaped valleys often are good evidence for the former existence of warm-based glaciers, there are few reliable indicators of cold-based glaciers and past frost action in a periglacial environment. For periglacial environments, attention in the past often concentrated upon the identification of relict features of assumed frost-action significance, like asymmetric valleys, ice wedge casts and blockfields. Unfortunately, some of the features assumed to be the result of frost-action also occur under non-periglacial conditions. In general terms, the rates and processes of many geomorphological processes depend on meteorology, climate, hydrology, geology and topography. Using landforms produced by such processes thus requires knowledge on quantitative relationships between the rate of geomorphological process and these variables. Recent progress in geomorphological field methodology has now added to the knowledge on timing and environmental conditions at which many periglacial and glacial landforms develop. Laboratory simulations have also provided insight into the mechanisms involved in some key periglacial processes. Such recent advances now enable us to link certain geomorphological process rates with their controlling environmental factors, eventually permitting the construction of a physically based predictive model of landform development as well as improved palaeoenvironmental reconstructions. There are, however, still a number of important, but unsolved, problems which hinder detailed palaeoenvironmental reconstructions based on cold-climate landforms. Some of these relate to modern meteorological conditions. As an example, many periglacial processes are controlled by ground temperatures and the amount of available moisture. There is, however, no simple relation between air temperature and ground temperature, as the latter is highly influenced by snow cover timing and -thickness. The snow cover development in its turn depends on the amount of solid precipitation, but not exclusively. Redistribution by wind is also of major importance, so ground temperature conditions are usually the result of complex relations between air temperature, precipitation and wind. In the case of attempts of palaeoenvironmental reconstructions based on the presence of a certain relict cold-climate landform, a number of possible combinations of these variables exist. Another partly unsolved problem relates to the magnitude of past temperature lapse rates. Usually, past temperature conditions are calculated on the basis of modern lapse rates and present snowlines in alpine regions. This sort of analysis tend to masks the considerably variability of modern lapse rates which occur in modern cold-climate mountain regions. Moreover, there is no guarantee that lapse rates were similar during past climatic periods to those observed today. During periods of colder climate, strong temperature inversions were probably more common than they are today, both in high-relief areas and in lowlands.
Geografiska Annaler Series a Physical Geography, Apr 1, 1997
... the pic-ture. April 1993. Page 4. OLE HUMLUM Geografiska Annaler · 79 A (1997) · 1–2 4 Many l... more ... the pic-ture. April 1993. Page 4. OLE HUMLUM Geografiska Annaler · 79 A (1997) · 1–2 4 Many localities ... glaciers, have also been proposed for the Skäralid ridges (Rapp et al. 1986; Nyberg 1988; Jonasson et al. in press). On the ...
Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujolkull, Island OLE ... more Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujolkull, Island OLE HUMLUM ^r r\yyri Humlum, O.: Dannelsen af en disloceret randmoraene ved en avancerende isrand, Hofdabrekkujokull, J JJXJP Island, Dansk geol. Foren., Årsskrift for 1982, side 11-26, København, 6. juni 1983.
Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears... more Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. INSTAAR, University of Colorado is collaborating with JSTOR to digitize, preserve and extend access to
Two new concepts relating to rock glaciers are defined: the rock glacier appearance level (RAL) a... more Two new concepts relating to rock glaciers are defined: the rock glacier appearance level (RAL) and the rock glacier initiation line altitude (RILA). The RAL may be regarded as an analogy to the glaciological concept glaciation level (GL) and indicates a critical summit ...
I GeologiskNyt nr. 3 og 4 2008 har Hessbjerg, Henriksen og Hinsby samt Langen indlaeg som modsvar... more I GeologiskNyt nr. 3 og 4 2008 har Hessbjerg, Henriksen og Hinsby samt Langen indlaeg som modsvar til min artikel i GeologiskNyt nr. 2 2008. Det er glaedeligt, at min lille artikel har vakt opmaerksomhed, men det er samtidig lidt skuffende, at ingen af de tre modsvar berører hovedtemaet om forholdet mellem forventet og faktisk temperaturaendring. Modsvarenes grundighed giver imidlertid baggrund for en replik, der tydeliggør, hvori den grundlaeggende uenighed om klimamodellering består. Jeg tager her udgangspunkt i Hessbjergs fokus på CO 2 's betydning.
Monitoring and modelling snow avalanches in Svalbard Ole Humlum 1,3, Hanne H. Christiansen 1, Ulr... more Monitoring and modelling snow avalanches in Svalbard Ole Humlum 1,3, Hanne H. Christiansen 1, Ulrich Neumann 1, Markus Eckerstorfer 1, Anna Sjöblom 1, Knut Stalsberg 2 and Lena Rubensdotter 2. 1: The University Centre in Svalbard (UNIS). 2: Geological Survey of Norway (NGU) 3: University of Oslo Ground based transportation in Svalbard landscape all takes place across mountainous terrain affected by different geomorphological slope processes. Traffic in and around the Svalbard settlements is increasing, and at the same time global climate models project substantial increases in temperature and precipitation in northern high latitudes for coming century. Therefore improved knowledge on the effect of climatic changes on slope processes in such high arctic landscapes is becoming increasingly important. Motivated by this, the CRYOSLOPE Svalbard research project since 2007 has carried out field observations on snow avalanche frequency and associated meteorological conditions. Snow avalanches are important geomorphic agents of erosion and deposition, and have long been a source of natural disasters in many mid-latitude mountain areas. Avalanches as a natural hazard has thereby been familiar to inhabitants of the Alps and Scandinavia for centuries, while it is a more recent experience in high arctic Svalbard. In addition, overall climate, topography and especially high winter wind speeds makes it difficult to apply snow avalanche models (numerical or empirical) developed for use at lower latitudes, e.g. in central Europe. In the presentation we examplify results from the ongoing (since winter 2006-07) monitoring of snow avalanches in Svalbard along a 70 km long observational route in the mountains. In addition, we present observations on the geomorphological impact of avalanches, with special reference to the formation of rock glaciers. Finally, we also present some initial results from numerical attempts of snow avalanche risk modelling within the study area.
The debris-covered ice-margins of three largely cold-based glaciers in central Spitsbergen were i... more The debris-covered ice-margins of three largely cold-based glaciers in central Spitsbergen were investigated to reconstruct their formation and degradation. Clast shapes indicate dominant englacial and supraglacial transport with a smaller subglacial component. Emplacement of material is inferred to have been through meltout along flowlines due to the relatively uniform and continuous debris cover along the glacier margins; no evidence of thrusting has been found. Degradation of all three belts is rapid and involves debris flows at unstable places-e.g., the margins of meltwater channels. Resultant exposure of underlying ice initiates or accelerates melting, thereby leading to further debris flows. Hence, once degradation starts, a self-reinforcing cycle that removes material from the glacier commences. Landform preservation potential on millennial time scales in a high-arctic, continuous permafrost environment is thus limited. This work has implications for the interpretation of Pleistocene landform associations that use modern analogues from Svalbard. 1 The authors would like to thank Dr. Douglas I. Benn for his invaluable input and help in designing and organizing these separate projects. Discussions with him that ultimately improved the quality of the manuscript are greatly appreciated. Dr. Hanne H. Christiansen and the staff at UNIS, Longyearbyen are thanked for local support in Svalbard and numerous enthusiastic discussions. We are grateful to Dr. Arthur S. Dyke and an anonymous reviewer who provided helpful reviews that improved the readability of the manuscript.
Much renewed research interest in Arctic regions stems from the increasing concentration of atmos... more Much renewed research interest in Arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas. Glacier and permafrost changes are among a number of proxies used for monitoring past and present Arctic climate change. Here we present observations on frozen in situ soil and vegetation, found below cold-based glacier Longyearbreen (78813?N), 2 km upstream from the present glacier terminus. Dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c. 1100 years. The meteorological setting of non-surging Longyearbreen suggests this example of late-Holocene glacier growth represents a widespread phenomenon in Svalbard and in adjoining Arctic regions. In addition, we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods, and we present evidence for microbes having survived more than 1100 years in a subglacial, permafrozen state.
Reflections on modern cold-climate landforms and their relation to climate Ole Humlum, University... more Reflections on modern cold-climate landforms and their relation to climate Ole Humlum, University of Oslo, Department of Geosciences The identification of fossil cold-climate landforms is important from a palaeoclimatic point of view. Attempts at reconstructing past cold-climate environments are based mostly on the utilization of certain fossil periglacial and glacial landforms and sedimentary structures, such as ice and sand wedge casts, thermal cracks, fragipan horizons, the systematic occurrence of cryoturbation or solifluction, evidence of strong ice segregation in sediments, fossil rock glaciers, moraines, tills and glacial valleys. Many attempts of palaeoenvironmental reconstruction are based on biological evidence, which tend to reflect summer conditions, rather than winter conditions. In this respect the use of cold-climate landform in palaeoenvironmental reconstructions is potentially important, as many of such landforms often depend on the presence of ice, which tend to reflect winter conditions rather than summer conditions. A number of difficulties, however, immediately arise. As an example, climatic changes resulting in the areal disappearance of ice-rich permafrost beyond the margins of Quaternary ice sheets and glaciers tend to blur or confuse the evidence of previously distinct periglacial and glacial features. Traces of their morphology and relict surface and subsurface structures may, however, still be detected in certain regions. Such fossil forms, especially when dated, can then be used as important indicators of a past climate in the region considered. While geomorphological features such as glacial striae and U-shaped valleys often are good evidence for the former existence of warm-based glaciers, there are few reliable indicators of cold-based glaciers and past frost action in a periglacial environment. For periglacial environments, attention in the past often concentrated upon the identification of relict features of assumed frost-action significance, like asymmetric valleys, ice wedge casts and blockfields. Unfortunately, some of the features assumed to be the result of frost-action also occur under non-periglacial conditions. In general terms, the rates and processes of many geomorphological processes depend on meteorology, climate, hydrology, geology and topography. Using landforms produced by such processes thus requires knowledge on quantitative relationships between the rate of geomorphological process and these variables. Recent progress in geomorphological field methodology has now added to the knowledge on timing and environmental conditions at which many periglacial and glacial landforms develop. Laboratory simulations have also provided insight into the mechanisms involved in some key periglacial processes. Such recent advances now enable us to link certain geomorphological process rates with their controlling environmental factors, eventually permitting the construction of a physically based predictive model of landform development as well as improved palaeoenvironmental reconstructions. There are, however, still a number of important, but unsolved, problems which hinder detailed palaeoenvironmental reconstructions based on cold-climate landforms. Some of these relate to modern meteorological conditions. As an example, many periglacial processes are controlled by ground temperatures and the amount of available moisture. There is, however, no simple relation between air temperature and ground temperature, as the latter is highly influenced by snow cover timing and -thickness. The snow cover development in its turn depends on the amount of solid precipitation, but not exclusively. Redistribution by wind is also of major importance, so ground temperature conditions are usually the result of complex relations between air temperature, precipitation and wind. In the case of attempts of palaeoenvironmental reconstructions based on the presence of a certain relict cold-climate landform, a number of possible combinations of these variables exist. Another partly unsolved problem relates to the magnitude of past temperature lapse rates. Usually, past temperature conditions are calculated on the basis of modern lapse rates and present snowlines in alpine regions. This sort of analysis tend to masks the considerably variability of modern lapse rates which occur in modern cold-climate mountain regions. Moreover, there is no guarantee that lapse rates were similar during past climatic periods to those observed today. During periods of colder climate, strong temperature inversions were probably more common than they are today, both in high-relief areas and in lowlands.
Geografiska Annaler Series a Physical Geography, Apr 1, 1997
... the pic-ture. April 1993. Page 4. OLE HUMLUM Geografiska Annaler · 79 A (1997) · 1–2 4 Many l... more ... the pic-ture. April 1993. Page 4. OLE HUMLUM Geografiska Annaler · 79 A (1997) · 1–2 4 Many localities ... glaciers, have also been proposed for the Skäralid ridges (Rapp et al. 1986; Nyberg 1988; Jonasson et al. in press). On the ...
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