Pub Date : 2021-10-02DOI: 10.1080/04353676.2021.2000816
J. Kalvoda, A. Emmer
ABSTRACT Mountain regions of the world face unprecedented climate-induced changes and associated sustainable development challenges. Retreating glaciers, degrading permafrost and rapid mass movements on the one hand and glacier-related disasters, on the other hand, are the sentinels of these phenomena. In this study, we focus our attention on the Makalu Barun region in the Nepal Himalaya, and characterize four main morphoclimatic zones, building on repeated field surveys and interpretation of remote sensing imagery. We distinguish four distinct zones: (i) extreme glacial zone; (ii) glacial zone; (iii) periglacial zone; and (iv) seasonally cold/warm humid zone. While extreme glacial zone is stagnant in its area, remaining three zones have been experiencing areal/location changes associated with changing climate, glacier extent and permafrost distribution. We describe dominant geomorphic processes and typical landforms of these zones in detail, highlighting the role of mass wasting processes and far-reaching process chains acting across distinct morphoclimatic zones. The study provides evidence of very dynamic landform evolution which indicates extreme geomorphological hazards in the Nepal Himalaya.
{"title":"Mass wasting and erosion in different morphoclimatic zones of the Makalu Barun region, Nepal Himalaya","authors":"J. Kalvoda, A. Emmer","doi":"10.1080/04353676.2021.2000816","DOIUrl":"https://doi.org/10.1080/04353676.2021.2000816","url":null,"abstract":"ABSTRACT Mountain regions of the world face unprecedented climate-induced changes and associated sustainable development challenges. Retreating glaciers, degrading permafrost and rapid mass movements on the one hand and glacier-related disasters, on the other hand, are the sentinels of these phenomena. In this study, we focus our attention on the Makalu Barun region in the Nepal Himalaya, and characterize four main morphoclimatic zones, building on repeated field surveys and interpretation of remote sensing imagery. We distinguish four distinct zones: (i) extreme glacial zone; (ii) glacial zone; (iii) periglacial zone; and (iv) seasonally cold/warm humid zone. While extreme glacial zone is stagnant in its area, remaining three zones have been experiencing areal/location changes associated with changing climate, glacier extent and permafrost distribution. We describe dominant geomorphic processes and typical landforms of these zones in detail, highlighting the role of mass wasting processes and far-reaching process chains acting across distinct morphoclimatic zones. The study provides evidence of very dynamic landform evolution which indicates extreme geomorphological hazards in the Nepal Himalaya.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"4 1","pages":"368 - 396"},"PeriodicalIF":1.5,"publicationDate":"2021-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89078547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-02DOI: 10.1080/04353676.2021.1986304
W. Whalley
ABSTRACT A valley floor rock glacier in Nautárdalur, eastern Tröllaskagi, northern Iceland, has been investigated since the 1970s. Adjacent valleys are also examined as mountain landsystems. The methodology identifies ‘landform elements’ (features evident on slopes) on transects that can be identified and mapped from Google Earth imagery. Transects can be compared to show similarities and differences between slopes and valleys and can be used to trace debris and ice/snow flow paths within landsystems. The paper confirms that a glacier ice core is present throughout the Nautárdalur rock glacier. Traces of glacier activity can be found in some neighbouring small valleys but where rock glaciers are not present. Previous field observations, when coupled to current Google Earth imagery, indicate glacier ice formation and deformation over the past 200 years. The quantities and timing of weathered debris from headwall cliffs were sufficient to partly cover small glaciers, thus forming rock glaciers in some, but not all, valleys. The landsystem and transect approach thus indicate glacier origins for the rock glaciers identified. No evidence for ‘permafrost creep’ in scree slopes that might produce valley-side rock glaciers has been found.
{"title":"The glacier–rock glacier mountain landsystem: an example from North Iceland","authors":"W. Whalley","doi":"10.1080/04353676.2021.1986304","DOIUrl":"https://doi.org/10.1080/04353676.2021.1986304","url":null,"abstract":"ABSTRACT A valley floor rock glacier in Nautárdalur, eastern Tröllaskagi, northern Iceland, has been investigated since the 1970s. Adjacent valleys are also examined as mountain landsystems. The methodology identifies ‘landform elements’ (features evident on slopes) on transects that can be identified and mapped from Google Earth imagery. Transects can be compared to show similarities and differences between slopes and valleys and can be used to trace debris and ice/snow flow paths within landsystems. The paper confirms that a glacier ice core is present throughout the Nautárdalur rock glacier. Traces of glacier activity can be found in some neighbouring small valleys but where rock glaciers are not present. Previous field observations, when coupled to current Google Earth imagery, indicate glacier ice formation and deformation over the past 200 years. The quantities and timing of weathered debris from headwall cliffs were sufficient to partly cover small glaciers, thus forming rock glaciers in some, but not all, valleys. The landsystem and transect approach thus indicate glacier origins for the rock glaciers identified. No evidence for ‘permafrost creep’ in scree slopes that might produce valley-side rock glaciers has been found.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"37 1","pages":"346 - 367"},"PeriodicalIF":1.5,"publicationDate":"2021-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89914621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-06DOI: 10.1080/04353676.2021.1969130
R. Barthel, Moa Stangefelt, M. Giese, Michelle Nygren, Kristina Seftigen, Deliang Chen
ABSTRACT Recently, groundwater in Sweden has attracted media attention due to supply shortages caused by dry periods and low groundwater levels. About half of Swedish drinking water stems from groundwater. The small Swedish aquifers are highly dependent on frequent and sufficient recharge. Groundwater recharge forms the link between meteorological and groundwater drought and thus the main link between climate change and sustainable water supply. This study evaluated whether the current knowledge on groundwater recharge and groundwater drought is sufficient to mitigate the impacts of climate change. A review of international literature on groundwater recharge in regions with conditions similar to Sweden was performed. National literature was compared and links to international studies evaluated. A survey among Swedish groundwater experts complemented the study. Findings are that research on groundwater recharge has been scarce in Sweden over the last decades and Swedish experts seem to not have taken much notice of international literature. It is concluded that Sweden is not well prepared to predict the impact of climate change on groundwater resources, as the most crucial process linking climate to groundwater is not well understood. The study has a strong focus on Sweden, however, the results are also relevant for countries with similar geology and climate. One main conclusion is that groundwater recharge studies often remain unique, and thus hardly transferable and comparable. Two or more independent studies are rarely applied in parallel, verification based on direct groundwater observations is not common. This raises concerns about the reliability of climate change impact predictions on groundwater.
{"title":"Current understanding of groundwater recharge and groundwater drought in Sweden compared to countries with similar geology and climate","authors":"R. Barthel, Moa Stangefelt, M. Giese, Michelle Nygren, Kristina Seftigen, Deliang Chen","doi":"10.1080/04353676.2021.1969130","DOIUrl":"https://doi.org/10.1080/04353676.2021.1969130","url":null,"abstract":"ABSTRACT Recently, groundwater in Sweden has attracted media attention due to supply shortages caused by dry periods and low groundwater levels. About half of Swedish drinking water stems from groundwater. The small Swedish aquifers are highly dependent on frequent and sufficient recharge. Groundwater recharge forms the link between meteorological and groundwater drought and thus the main link between climate change and sustainable water supply. This study evaluated whether the current knowledge on groundwater recharge and groundwater drought is sufficient to mitigate the impacts of climate change. A review of international literature on groundwater recharge in regions with conditions similar to Sweden was performed. National literature was compared and links to international studies evaluated. A survey among Swedish groundwater experts complemented the study. Findings are that research on groundwater recharge has been scarce in Sweden over the last decades and Swedish experts seem to not have taken much notice of international literature. It is concluded that Sweden is not well prepared to predict the impact of climate change on groundwater resources, as the most crucial process linking climate to groundwater is not well understood. The study has a strong focus on Sweden, however, the results are also relevant for countries with similar geology and climate. One main conclusion is that groundwater recharge studies often remain unique, and thus hardly transferable and comparable. Two or more independent studies are rarely applied in parallel, verification based on direct groundwater observations is not common. This raises concerns about the reliability of climate change impact predictions on groundwater.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"42 2 1","pages":"323 - 345"},"PeriodicalIF":1.5,"publicationDate":"2021-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81164266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-31DOI: 10.1080/04353676.2021.1933958
H. Bernsteiner, J. Götz, B. Salcher, Andreas Lang
ABSTRACT During the last glacial maximum (LGM), large parts of the European Alps were occupied by an extensive interconnected system of valley glaciers. At lower elevations on the eastern fringe of the Alps, only a patchy pattern of isolated glaciers developed. Erosion by many of these smaller glaciers was however sufficient to excavate subglacial basins (‘overdeepening’) large enough to act as sedimentary archives of deglaciation processes. To constrain the deglaciation history and the post-LGM evolution of an isolated glacial system, we analyzed the geomorphology and the sedimentary record of a local overdeepening at the northern fringe of the Northern Calcareous Alps. We focus on the heavily silted lake system Taferlklaussee (TKS) (Höllengebirge massif, Austria) confined by a succession of terminal moraines and a steep headwall. Field techniques (mapping, Direct Current Resistivity, and core drilling), lab techniques (lithostratigraphic analyses and radiocarbon dating) and Geographic Information System (GIS) analyses are employed to document dynamics of erosion and sedimentation after deglaciation. We discuss drivers and controls of paraglacial landscape evolution. The almost complete postglacial (lake) record indicates abundant sediment input during the lateglacial and early Holocene, but strongly reduced dynamics since the Mid-Holocene. Sediment storage volumes range between 3.83 Mm³ and 5.75 Mm³ and lithology-specific mechanical denudation rates range between 0.8 mm/a and 1.7 mm/a depending on the scenario used. The study provides a well-constrained reference for the depositional dynamics of isolated LGM glacier systems of the Eastern Alps. It highlights the potential of using related sedimentary records to constrain the local variability in postglacial landscape evolution.
在末次盛冰期(last glacial maximum, LGM)，欧洲阿尔卑斯山脉的大部分地区被一个广泛的相互连接的山谷冰川系统所占据。在阿尔卑斯山东部边缘海拔较低的地方，只有零星的孤立冰川形成。然而，许多这些较小冰川的侵蚀足以挖掘出足够大的冰下盆地(“过深”)，作为冰川消融过程的沉积档案。为了限定一个孤立的冰川系统的脱冰史和lgm后的演化，我们分析了北钙质阿尔卑斯北缘一个局部过深的地貌和沉积记录。我们关注的是严重淤积的湖泊系统Taferlklaussee (TKS) (Höllengebirge山体，奥地利)，它被一连串的终端冰碛和陡峭的源头墙所限制。野外技术(测绘、直流电阻率和岩心钻探)、实验室技术(岩石地层分析和放射性碳测年)和地理信息系统(GIS)分析被用于记录冰川消融后侵蚀和沉积的动力学。我们讨论了副冰川景观演化的驱动因素和控制因素。几乎完整的冰后(湖)记录表明，冰川期和全新世早期有大量的沉积输入，但自全新世中期以来，动态变化明显减少。沉积物储存量在3.83 Mm³至5.75 Mm³之间，根据不同的场景，特定岩性的机械剥蚀速率在0.8 Mm /a至1.7 Mm /a之间。该研究为东阿尔卑斯孤立LGM冰川系统的沉积动力学提供了良好的约束参考。它强调了利用相关沉积记录来限制冰川后景观演变的局部变异性的潜力。
{"title":"From deglaciation to postglacial filling: post-LGM evolution of an isolated glacier system at the northern fringe of the Eastern Alps (Austria)","authors":"H. Bernsteiner, J. Götz, B. Salcher, Andreas Lang","doi":"10.1080/04353676.2021.1933958","DOIUrl":"https://doi.org/10.1080/04353676.2021.1933958","url":null,"abstract":"ABSTRACT During the last glacial maximum (LGM), large parts of the European Alps were occupied by an extensive interconnected system of valley glaciers. At lower elevations on the eastern fringe of the Alps, only a patchy pattern of isolated glaciers developed. Erosion by many of these smaller glaciers was however sufficient to excavate subglacial basins (‘overdeepening’) large enough to act as sedimentary archives of deglaciation processes. To constrain the deglaciation history and the post-LGM evolution of an isolated glacial system, we analyzed the geomorphology and the sedimentary record of a local overdeepening at the northern fringe of the Northern Calcareous Alps. We focus on the heavily silted lake system Taferlklaussee (TKS) (Höllengebirge massif, Austria) confined by a succession of terminal moraines and a steep headwall. Field techniques (mapping, Direct Current Resistivity, and core drilling), lab techniques (lithostratigraphic analyses and radiocarbon dating) and Geographic Information System (GIS) analyses are employed to document dynamics of erosion and sedimentation after deglaciation. We discuss drivers and controls of paraglacial landscape evolution. The almost complete postglacial (lake) record indicates abundant sediment input during the lateglacial and early Holocene, but strongly reduced dynamics since the Mid-Holocene. Sediment storage volumes range between 3.83 Mm³ and 5.75 Mm³ and lithology-specific mechanical denudation rates range between 0.8 mm/a and 1.7 mm/a depending on the scenario used. The study provides a well-constrained reference for the depositional dynamics of isolated LGM glacier systems of the Eastern Alps. It highlights the potential of using related sedimentary records to constrain the local variability in postglacial landscape evolution.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"101 1","pages":"305 - 322"},"PeriodicalIF":1.5,"publicationDate":"2021-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84643182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/04353676.2021.1955539
F. Miesen, S. Dahl, L. Schrott
ABSTRACT Glacier-permafrost interactions are investigated to understand glacial-hydrological influence along a partly glacierised valley on the NE flank of the Snøhetta massif, Dovrefjell, southern Norway. Of particular interest is how processes are controlled by a hydrological connection between landforms. Field mapping identified an ice-marginal landsystem comprising a polythermal glacier, a proglacial lake, an ice-cored moraine complex and a river-lake with perennial frost mounds. A clear interaction between glacial and periglacial processes was observed in transitional landforms, most prominently in the ice-cored moraine which constitutes a permafrost environment that is directly reworked by glaciofluvial processes. The role of this interaction in controlling seasonal, partial drainage of the proglacial lake was assessed using remote sensing-based observations of lake surface size evolution and seasonal surface subsidence. Results suggest a two-fold threshold for lake drainage: Depending on the dynamics of glacial discharge and active layer depth, the ice-cored moraine may either act as a barrier or a pathway to meltwater exiting the glacier. This demonstrates the importance of meltwater dynamics in controlling landform evolution in a glacial-periglacial landscape. To further assess the importance of surface and subsurface hydrology in linking glacial and periglacial domains, water stable oxygen isotope ratios across the study area were studied to map the flow of meltwater from glacier to permafrost. Results include a model of the surface and subsurface hydrology in the catchment and promote a conceptual understanding of water as a thermal, hydraulic and mechanical agent of transient glacier-permafrost interaction operating at heterogeneous timescales.
{"title":"Evidence of glacier-permafrost interactions associated with hydro-geomorphological processes and landforms at Snøhetta, Dovrefjell, Norway","authors":"F. Miesen, S. Dahl, L. Schrott","doi":"10.1080/04353676.2021.1955539","DOIUrl":"https://doi.org/10.1080/04353676.2021.1955539","url":null,"abstract":"ABSTRACT Glacier-permafrost interactions are investigated to understand glacial-hydrological influence along a partly glacierised valley on the NE flank of the Snøhetta massif, Dovrefjell, southern Norway. Of particular interest is how processes are controlled by a hydrological connection between landforms. Field mapping identified an ice-marginal landsystem comprising a polythermal glacier, a proglacial lake, an ice-cored moraine complex and a river-lake with perennial frost mounds. A clear interaction between glacial and periglacial processes was observed in transitional landforms, most prominently in the ice-cored moraine which constitutes a permafrost environment that is directly reworked by glaciofluvial processes. The role of this interaction in controlling seasonal, partial drainage of the proglacial lake was assessed using remote sensing-based observations of lake surface size evolution and seasonal surface subsidence. Results suggest a two-fold threshold for lake drainage: Depending on the dynamics of glacial discharge and active layer depth, the ice-cored moraine may either act as a barrier or a pathway to meltwater exiting the glacier. This demonstrates the importance of meltwater dynamics in controlling landform evolution in a glacial-periglacial landscape. To further assess the importance of surface and subsurface hydrology in linking glacial and periglacial domains, water stable oxygen isotope ratios across the study area were studied to map the flow of meltwater from glacier to permafrost. Results include a model of the surface and subsurface hydrology in the catchment and promote a conceptual understanding of water as a thermal, hydraulic and mechanical agent of transient glacier-permafrost interaction operating at heterogeneous timescales.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"22 1","pages":"273 - 302"},"PeriodicalIF":1.5,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89640144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1080/04353676.2021.1932482
F. Imaizumi, R. Sidle
ABSTRACT Forest harvesting and subsequent forest regeneration represent widespread changes in land cover in mountain regions. Although impacts of forest harvesting on landslide initiation has been widely reported, the effects of forest harvesting on the occurrence of debris flows remains unclear. We propose that forest harvesting will differentially affect the susceptibility of debris flows amongst catchments with different terrain characteristics. This hypothesis was assessed in the Sanko catchment, Japan, where comprehensive forest harvest records date back to 1913. The frequency of debris flows directly originating from landslides occurred in similar timeframes as the occurrence of landslides. Landslides that reached channels and continued downstream as debris flows were more prevalent in steep channel reaches with small hillslope-channel junction angles. In addition to the increase in the frequency of landslides, especially within 10 years after forest harvesting, debris flows caused by mass movement of channel deposits in steep reaches increased during this period. These relationships between the occurrence of debris flows and channel topography indicate a high susceptibility of debris flow occurrence after forest harvesting in first and zero-order mountain streams. Sediment previously routed into channel networks by landslides is likely a more important factor for in-channel debris flow initiation in the lower channel reaches, while instability of areas proximate to riparian zones, including stream banks and geomorphic hollows, possibly accelerate occurrence of debris flows in upper channel reaches. Consequently, catchment topography should be considered in evaluating debris flow risk after forest harvesting.
{"title":"Effects of terrain on the occurrence of debris flows after forest harvesting","authors":"F. Imaizumi, R. Sidle","doi":"10.1080/04353676.2021.1932482","DOIUrl":"https://doi.org/10.1080/04353676.2021.1932482","url":null,"abstract":"ABSTRACT Forest harvesting and subsequent forest regeneration represent widespread changes in land cover in mountain regions. Although impacts of forest harvesting on landslide initiation has been widely reported, the effects of forest harvesting on the occurrence of debris flows remains unclear. We propose that forest harvesting will differentially affect the susceptibility of debris flows amongst catchments with different terrain characteristics. This hypothesis was assessed in the Sanko catchment, Japan, where comprehensive forest harvest records date back to 1913. The frequency of debris flows directly originating from landslides occurred in similar timeframes as the occurrence of landslides. Landslides that reached channels and continued downstream as debris flows were more prevalent in steep channel reaches with small hillslope-channel junction angles. In addition to the increase in the frequency of landslides, especially within 10 years after forest harvesting, debris flows caused by mass movement of channel deposits in steep reaches increased during this period. These relationships between the occurrence of debris flows and channel topography indicate a high susceptibility of debris flow occurrence after forest harvesting in first and zero-order mountain streams. Sediment previously routed into channel networks by landslides is likely a more important factor for in-channel debris flow initiation in the lower channel reaches, while instability of areas proximate to riparian zones, including stream banks and geomorphic hollows, possibly accelerate occurrence of debris flows in upper channel reaches. Consequently, catchment topography should be considered in evaluating debris flow risk after forest harvesting.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"5 1","pages":"259 - 272"},"PeriodicalIF":1.5,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83662081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1080/04353676.2021.1926241
R. Sokołowski, A. Molodkov, A. Hrynowiecka, B. Woronko, P. Zieliński
ABSTRACT This study provides a new stratigraphic and palaeogeographic scheme for the time span between Marine Isotope Stages (MISs) 8 and 6. Based on detailed sedimentological and palynological studies, the roles of the Scandinavian Ice Sheet (SIS) advances and changing climate in the evolution of sedimentary environments is considered. At the Reda site, northern Poland, vertically stacked, 25 m thick glacigenic and fluvial successions were distinguished and divided into four depositional complexes. Two glacigenic units (R1 and R 2), representing two SIS advances in study area, are separated by two fluvial units (R2 and R3). The first SIS advance recorded at the Reda site took place at the end of MIS 8. Proglacial fluvial systems transported material along the ice margin towards the NW (R1 complex). Migration of the forebulge during deglaciation led to incision and opened the outflow towards the SW. During the younger part of MIS 7, the older fluvial unit (R2 complex) was deposited in a sand-bed braided fluvial system in boreal climate conditions. Local erosion and change in the sedimentation style into a meandering one under periglacial conditions took place (R3 complex). The progressive cooling of the climate towards the end of MIS 6 resulted in another SIS transgression and deposition of coarse-grained sediments (R4 complex) in the ice-marginal zone during deglaciation. SIS played a key role in the formation of R1 and R4 complexes. Glacial processes managed the reshaping the landscape through the erosion of older sediments and in the formation of accommodation space. Glacioisostatic movement controlled accommodation space, accumulation-erosion ratio, size of catchment and morphology of the valley.
{"title":"The role of an ice-sheet, glacioisostatic movements and climate in the transformation of Middle Pleistocene depositional systems: a case study from the Reda site, northern Poland","authors":"R. Sokołowski, A. Molodkov, A. Hrynowiecka, B. Woronko, P. Zieliński","doi":"10.1080/04353676.2021.1926241","DOIUrl":"https://doi.org/10.1080/04353676.2021.1926241","url":null,"abstract":"ABSTRACT This study provides a new stratigraphic and palaeogeographic scheme for the time span between Marine Isotope Stages (MISs) 8 and 6. Based on detailed sedimentological and palynological studies, the roles of the Scandinavian Ice Sheet (SIS) advances and changing climate in the evolution of sedimentary environments is considered. At the Reda site, northern Poland, vertically stacked, 25 m thick glacigenic and fluvial successions were distinguished and divided into four depositional complexes. Two glacigenic units (R1 and R 2), representing two SIS advances in study area, are separated by two fluvial units (R2 and R3). The first SIS advance recorded at the Reda site took place at the end of MIS 8. Proglacial fluvial systems transported material along the ice margin towards the NW (R1 complex). Migration of the forebulge during deglaciation led to incision and opened the outflow towards the SW. During the younger part of MIS 7, the older fluvial unit (R2 complex) was deposited in a sand-bed braided fluvial system in boreal climate conditions. Local erosion and change in the sedimentation style into a meandering one under periglacial conditions took place (R3 complex). The progressive cooling of the climate towards the end of MIS 6 resulted in another SIS transgression and deposition of coarse-grained sediments (R4 complex) in the ice-marginal zone during deglaciation. SIS played a key role in the formation of R1 and R4 complexes. Glacial processes managed the reshaping the landscape through the erosion of older sediments and in the formation of accommodation space. Glacioisostatic movement controlled accommodation space, accumulation-erosion ratio, size of catchment and morphology of the valley.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"27 1","pages":"223 - 258"},"PeriodicalIF":1.5,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83277378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-11DOI: 10.1080/04353676.2020.1856625
S. Grab, J. Knight, L. Mol, T. Botha, C. Carbutt, S. Woodborne
ABSTRACT Here, we aim to establish possible morphogenetic associations between periglacial phenomena (sorted circles and turf-/stone-banked lobes) by examining (a) rock surface weathering rinds by thin section microscopy and SEM-EDX analysis, and (b) alpine shrub growth patterns of Helichrysum trilineatum supported by AMS 14C age determination. The study area is the Mafadi–Njesuthi summit zone, one of the highest alpine regions of southern Africa. Rock weathering results indicate that clasts in large sorted circle centres experience high chemical weathering rates on both exposed (upper) and non-exposed (lower) surfaces, whereas clasts in lobes and very large apparently ‘relict’ sorted circles have been inactive for a prolonged period of time, based on strongly contrasting weathering rates on both exposed and non-exposed clast surfaces. Large sorted circles originating from a previous (possibly Last Glacial Maximum or late-glacial) colder period are still marginally or episodically active, thus restricting plant succession on these landforms. Even where very large sorted circles and turf-/stone-banked lobes are inactive, their legacy continues, as expressed in today’s surface morphology, and still influence ground abiotic conditions through the generation of microrelief and microclimate which in turn have impacts on ecosystem patterns including the distribution of H. trilineatum. Such shrub growth patterns are influenced by microscale site morphology, associated abiotic controls, and ongoing seasonal cryogenic activity. Both active and inactive periglacial landforms on highest summits of the Drakensberg represent microscale environments with distinct fine-scale abiotic and geomorphic settings, which in turn are manifested through differences in plant ecology and rock surface weathering, respectively.
{"title":"Periglacial landforms in the high Drakensberg, Southern Africa: morphogenetic associations with rock weathering rinds and shrub growth patterns","authors":"S. Grab, J. Knight, L. Mol, T. Botha, C. Carbutt, S. Woodborne","doi":"10.1080/04353676.2020.1856625","DOIUrl":"https://doi.org/10.1080/04353676.2020.1856625","url":null,"abstract":"ABSTRACT Here, we aim to establish possible morphogenetic associations between periglacial phenomena (sorted circles and turf-/stone-banked lobes) by examining (a) rock surface weathering rinds by thin section microscopy and SEM-EDX analysis, and (b) alpine shrub growth patterns of Helichrysum trilineatum supported by AMS 14C age determination. The study area is the Mafadi–Njesuthi summit zone, one of the highest alpine regions of southern Africa. Rock weathering results indicate that clasts in large sorted circle centres experience high chemical weathering rates on both exposed (upper) and non-exposed (lower) surfaces, whereas clasts in lobes and very large apparently ‘relict’ sorted circles have been inactive for a prolonged period of time, based on strongly contrasting weathering rates on both exposed and non-exposed clast surfaces. Large sorted circles originating from a previous (possibly Last Glacial Maximum or late-glacial) colder period are still marginally or episodically active, thus restricting plant succession on these landforms. Even where very large sorted circles and turf-/stone-banked lobes are inactive, their legacy continues, as expressed in today’s surface morphology, and still influence ground abiotic conditions through the generation of microrelief and microclimate which in turn have impacts on ecosystem patterns including the distribution of H. trilineatum. Such shrub growth patterns are influenced by microscale site morphology, associated abiotic controls, and ongoing seasonal cryogenic activity. Both active and inactive periglacial landforms on highest summits of the Drakensberg represent microscale environments with distinct fine-scale abiotic and geomorphic settings, which in turn are manifested through differences in plant ecology and rock surface weathering, respectively.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"15 3 1","pages":"199 - 222"},"PeriodicalIF":1.5,"publicationDate":"2021-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85041908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1080/04353676.2021.1888202
S. Harrison, Darren B. Jones, K. Anderson, S. Shannon, R. Betts
ABSTRACT In the Himalaya, climate change threatens mountain water resources as glaciers melt and changes in runoff and water availability are likely to have considerable negative impacts on ecological and human systems. While much has been written on the effect of climate change on glaciers in the Himalaya and its impact on sustainability, almost nothing has been published on rock glaciers in the region and their role in maintaining water supplies as the climate warms. Rock glaciers are important components of the Himalayan hydrological system because they are present in almost all regions of the Himalaya and are climatically more resilient than other glacier types owing to an insulating layer of debris cover. Research from other mountain regions shows that they contain potentially important water stores, although in the Himalaya, there is almost no information on their number, spatial distribution and response to future climate change. The extent to which this contributes to higher resilience of the Himalayan cryosphere as a whole is still an open question. This paper argues that research into Himalayan rock glaciers that reveals their hydrological significance is critical for underpinning climate change adaptation strategies and to ensure that this highly populated region is in a strong position to meet sustainable development goals.
{"title":"Is ice in the Himalayas more resilient to climate change than we thought?","authors":"S. Harrison, Darren B. Jones, K. Anderson, S. Shannon, R. Betts","doi":"10.1080/04353676.2021.1888202","DOIUrl":"https://doi.org/10.1080/04353676.2021.1888202","url":null,"abstract":"ABSTRACT In the Himalaya, climate change threatens mountain water resources as glaciers melt and changes in runoff and water availability are likely to have considerable negative impacts on ecological and human systems. While much has been written on the effect of climate change on glaciers in the Himalaya and its impact on sustainability, almost nothing has been published on rock glaciers in the region and their role in maintaining water supplies as the climate warms. Rock glaciers are important components of the Himalayan hydrological system because they are present in almost all regions of the Himalaya and are climatically more resilient than other glacier types owing to an insulating layer of debris cover. Research from other mountain regions shows that they contain potentially important water stores, although in the Himalaya, there is almost no information on their number, spatial distribution and response to future climate change. The extent to which this contributes to higher resilience of the Himalayan cryosphere as a whole is still an open question. This paper argues that research into Himalayan rock glaciers that reveals their hydrological significance is critical for underpinning climate change adaptation strategies and to ensure that this highly populated region is in a strong position to meet sustainable development goals.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"27 1","pages":"1 - 7"},"PeriodicalIF":1.5,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83466051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1080/04353676.2020.1864947
Bettina Knoflach, Hannah Tussetschläger, R. Sailer, G. Meissl, J. Stötter
ABSTRACT Rockfalls are a major aspect concerning morphodynamics in high mountain areas and represent a serious hazard for people and infrastructure. Recently, an increase of rockfall activity has been observed which is probably related to the destabilization of rock slopes through climate-related changes of the mountain cryosphere. This study investigates the rockfall distribution during a 4-year monitoring period by systematic observation with bi-temporal Airborne Laser Scanning DTMs in an area of 610.7 km² in the Ötztal Alps/Tyrol, Austria. The analyses of the 93 detected rockfall events indicate that rockfall activity is highest in proglacial areas. Further 83.9% of all rockfall source areas were mapped in bedrock where the modelled mean annual ground temperature (MAGT) indicates perennial frozen conditions. The results demonstrate the importance of thermal effects on the destabilization of rock faces and show that the triggering of rockfalls is closely related to changes in the glacier and permafrost regime. 18 low-magnitude rockfalls with volumes between 69 ± 3 m³ and 8420 ± 89 m³ are examined in detail. On the base of the analysis of these events energy line angles of 28.7° for the Fahrböschung and 19.9° for the minimum shadow angle can be derived and significantly longer runout distances on glaciated rockfall paths are observed.
{"title":"High mountain rockfall dynamics: rockfall activity and runout assessment under the aspect of a changing cryosphere","authors":"Bettina Knoflach, Hannah Tussetschläger, R. Sailer, G. Meissl, J. Stötter","doi":"10.1080/04353676.2020.1864947","DOIUrl":"https://doi.org/10.1080/04353676.2020.1864947","url":null,"abstract":"ABSTRACT Rockfalls are a major aspect concerning morphodynamics in high mountain areas and represent a serious hazard for people and infrastructure. Recently, an increase of rockfall activity has been observed which is probably related to the destabilization of rock slopes through climate-related changes of the mountain cryosphere. This study investigates the rockfall distribution during a 4-year monitoring period by systematic observation with bi-temporal Airborne Laser Scanning DTMs in an area of 610.7 km² in the Ötztal Alps/Tyrol, Austria. The analyses of the 93 detected rockfall events indicate that rockfall activity is highest in proglacial areas. Further 83.9% of all rockfall source areas were mapped in bedrock where the modelled mean annual ground temperature (MAGT) indicates perennial frozen conditions. The results demonstrate the importance of thermal effects on the destabilization of rock faces and show that the triggering of rockfalls is closely related to changes in the glacier and permafrost regime. 18 low-magnitude rockfalls with volumes between 69 ± 3 m³ and 8420 ± 89 m³ are examined in detail. On the base of the analysis of these events energy line angles of 28.7° for the Fahrböschung and 19.9° for the minimum shadow angle can be derived and significantly longer runout distances on glaciated rockfall paths are observed.","PeriodicalId":55112,"journal":{"name":"Geografiska Annaler Series A-Physical Geography","volume":"1 1","pages":"83 - 102"},"PeriodicalIF":1.5,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77076372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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