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Foreland evolution of Blåisen, Norway, over the course of an ablation season

Hamilton-Foyn, Alexander LU (2020) In Dissertations in Geology at Lund University GEOR02 20192
Department of Geology
Abstract
This study presents a detailed investigation into the evolution of sedimentary landforms over an ablation season at Blåisen, an outlet of the Hardangerjøkulen Icecap, Norway. The two visits to Blåisen, one each side of the ablation season, allowed the preservation and evolution of the landforms to be studied. Much research is conducted studying glacial landforms, which are key in our understanding of past and future ice behaviour. This is important in researching the past, present and future response of the cryosphere to climate forcing, and the impact of such changes. A smaller portion of glacial geomorphological studies are now conducted using predominantly fieldwork with even fewer making repeated visits to sites in short succession.... (More)
This study presents a detailed investigation into the evolution of sedimentary landforms over an ablation season at Blåisen, an outlet of the Hardangerjøkulen Icecap, Norway. The two visits to Blåisen, one each side of the ablation season, allowed the preservation and evolution of the landforms to be studied. Much research is conducted studying glacial landforms, which are key in our understanding of past and future ice behaviour. This is important in researching the past, present and future response of the cryosphere to climate forcing, and the impact of such changes. A smaller portion of glacial geomorphological studies are now conducted using predominantly fieldwork with even fewer making repeated visits to sites in short succession. Many now use remote sensing which, while being a powerful tool to understand ice behaviour, means that smaller scale features (both in the temporal and spatial sense) may be missed. An awareness of what may be missing when studying forelands that are a few years to many millennia old is important to gaining a more holistic understanding of the ice behaviour and the processes occurring. This study focuses on the younger landforms in the immediate vicinity of the ice margin. GPS mapping, field observations and Structure from Motion Photogrammetry was used over two visits to Blåisen in June and September to identify four such landform types: snowbank squeeze moraines, flutes, minor moraines and an ice-cored wedged shaped ridge system (called a sediment wedge in this study after its characteristic shape).
The foreland of Blåisen was characterised by a number of areas where a reverse bedrock was present (bedrock that slopes in the opposite direction to ice flow); this had the effect of inhibiting drainage leading to saturated sediments around the ice margin. These sediments are easily deformable, so play an important role in the formation of the Snowbank Squeeze Moraines, Flutes, Minor Moraines in particular. The processes of formation are explored using the geomorphological and sedimentological evidence to devise genesis and evolution models for each landform type. The model for the formation of the sediment wedge presents freeze-on as a prominent mechanism, facilitating the transport of debris in a band from the base of the glacier to the margin where, due to differential melting, the underlying ice is isolated from the rest of the glacier. Snowbank Squeeze Moraines were observed as ridges of sediment protruding out of the snow in June formed by the deformation of sediments between the ice margin and the winter snowbank lying over the margin. The ‘squeeze’ form of snowbank moraines has not been widely documented in part due to their poor preservation, illustrated by the lack of remaining evidence for them in September. Few flutes were recorded aside from those mapped in September, indicating that either in past seasons, conditions had not been favourable for formation, or that preservation was poor. The latter is supported by the lack of remaining evidence of the snowbank squeeze ridges in September. The poor preservation of these landforms highlights how they may be missed in other studies and the need for further research in this area. (Less)
Abstract (Swedish)
Denna studie presenterar en detaljerad undersökning av utvecklingen av sedimentära landformer under en ablationssäsong vid Blåisen, en del av Hardangerjøkulen, Norge. Två besök vid Blåisen, i början och i slutet av ablationssäsongen, gjorde det möjligt att studera hur landformerna bevaras och utvecklas. Det pågår mycket forskning om glaciala landformer som är en nyckel till förståelse av hur tidigare och framtida isar fungerar. Detta är en viktig del inom forskningen om hur kryosfären har reagerat, reagerar och kommer att reagera på klimatförändringar och vilka effekter de ger. En mindre andel av de glacialmorfologiska studierna är nu övervägande baserade på fältarbete, och inom ännu färre görs upprepade besök på samma plats med korta... (More)
Denna studie presenterar en detaljerad undersökning av utvecklingen av sedimentära landformer under en ablationssäsong vid Blåisen, en del av Hardangerjøkulen, Norge. Två besök vid Blåisen, i början och i slutet av ablationssäsongen, gjorde det möjligt att studera hur landformerna bevaras och utvecklas. Det pågår mycket forskning om glaciala landformer som är en nyckel till förståelse av hur tidigare och framtida isar fungerar. Detta är en viktig del inom forskningen om hur kryosfären har reagerat, reagerar och kommer att reagera på klimatförändringar och vilka effekter de ger. En mindre andel av de glacialmorfologiska studierna är nu övervägande baserade på fältarbete, och inom ännu färre görs upprepade besök på samma plats med korta tidsintervall. Flertalet forskare använder nu fjärranalys som, även om det är ett kraftfullt verktyg för att förstå isdynamik, innebär att företeelser i mindre skala (både i tidsmässig och rumslig mening) kan missas. För att få en helhetsförståelse för isdynamiken och de processer som äger rum är det viktigt med en medvetenhet om vad som, beroende på metod, kan undgå upptäckt när man studerar glaciala förland som är några år till tusentals år gamla. Denna studie fokuserar på yngre landformer i omedelbar närhet av isfronten. GPS-kartläggning, fältobservationer och Structure-from-motion- fotogrammetri användes under två fältbesök vid Blåisen i juni och september 2019 för att identifiera fyra sådana landformstyper: snödrivepressade moräner (Snowbank Squeeze Moraines), moränsträngar, mindre moräner och ett system av kilformade ryggar med iskärnor (kallat sedimentkil i denna studie efter dess karakteristiska form).
Blåisens förland kännetecknades av ett antal områden där berggrunden lutade mot glaciären (berggrund som lutar i motsatt riktning mot isflödet); detta hindrade dräneringen vilket ledde till att sedimenten vid iskanten blev vattenmättade. Dessa sediment är lättdeformerade och spelar en viktig roll i bildandet av snödrivepressade moräner, moränsträngar och särskilt de mindre moränerna. Bildningsprocesserna utforskas med hjälp av geomorfologiska och sedimentologiska observationer för att utforma bildnings- och utvecklingsmodeller för varje landformstyp. Bildningsmodellen för sedimentkilen tar upp tillfrysning som en framträdande mekanism, och som underlättar materialtransport från glaciärens bas till kanten där den underliggande isen isoleras från resten av glaciären genom olikformig avsmältning. De snödrivepressade moränerna observerades som ryggar av sediment som stack ut ur snön i juni och var bildade genom deformation av sediment mellan iskanten och den driva av vintersnö som låg över iskanten. Den "pressade" formen hos snödrivemoränerna har inte kunnat dokumenteras i detalj, delvis på grund av deras dåliga bevarande, vilket illustreras av att det inte fanns kvar några spår av dem i september. Få moränsträngar observerades förutom de som kartlades i september. Det visar att antingen hade förhållandena inte varit gynnsamma för bildandet av moränsträngar under tidigare säsonger eller så var bevarandegraden dålig. Det sistnämnda stöds av bristen på kvarvarande bevis för snödrivemoränryggarna i september. Den dåliga bevarandegraden hos dessa landformer belyser hur de kan missas i andra studier och visar på behovet av ytterligare forskning inom detta område. (Less)
Popular Abstract
This study presents a detailed investigation into the evolution of sedimentary landforms over an ablation (melt) season at Blåisen, an outlet glacier of the Hardangerjøkulen Icecap in Norway. The two visits to Blåisen in 2019, one each side of the ablation season, allowed the formation, preservation, and evolution of the landforms to be studied.
Much research is conducted studying glacial landforms, which are key in our understanding of past and future ice behaviour. This is important in researching the past, present and future response of the cryosphere to climate forcing, and the impact of such changes. Increasingly, fewer glacial landform studies are conducted focusing on fieldwork, with even fewer making repeated visits to sites to... (More)
This study presents a detailed investigation into the evolution of sedimentary landforms over an ablation (melt) season at Blåisen, an outlet glacier of the Hardangerjøkulen Icecap in Norway. The two visits to Blåisen in 2019, one each side of the ablation season, allowed the formation, preservation, and evolution of the landforms to be studied.
Much research is conducted studying glacial landforms, which are key in our understanding of past and future ice behaviour. This is important in researching the past, present and future response of the cryosphere to climate forcing, and the impact of such changes. Increasingly, fewer glacial landform studies are conducted focusing on fieldwork, with even fewer making repeated visits to sites to study the changes. Many studies now favour remote sensing which, while being a powerful tool to understand ice behaviour, means that smaller, more subtle features may be missed. An awareness of what may be missing when studying forelands is important in gaining a better overall understanding of the ice behaviour and the processes occurring.
This study focuses on the younger landforms close to the ice margin. The ice margin retreated up to 30-40 m over the summer of 2019, exposing a number of landforms that had been covered by ice and snow in June. GPS mapping, field observations and Structure from Motion Photogrammetry (a 3D modelling technique) was used over the two visits to Blåisen in June and September. Four main landform types were recorded: snowbank squeeze moraines, flutes, minor moraines, and an ice-cored wedged shaped ridge system (called a sediment wedge in this study after its characteristic shape).
The foreland of Blåisen had several interesting areas where the bedrock sloped back towards the glacier. This had the effect of preventing meltwater from draining, leading to saturated sediments around the ice margin. These sediments were easily deformable, so played an important role in the formation of the snowbank squeeze moraines, flutes, minor moraines.
The mechanisms of formation are explored using the field evidence to create theoretical models for how the landforms formed and evolved over the melt season. The model for the formation of the sediment wedge presents freezing-on of sediment to the ice as an important mechanism. This allowed the transport of debris in a band from the base of the glacier to the margin, where it covered the underlying ice, cutting it off from the main glacier and forming an ice-cored wedge.
Snowbank Squeeze Moraines were observed as ridges of sediment protruding out of the snow in June. They formed by the deformation (squeezing) of sediments between the ice margin and the winter snowbank lying over the margin. The ‘squeeze’ type of snowbank moraines have not been widely studied in part due to their poor longer-term preservation beyond a few months. This was illustrated by the lack of remaining evidence for them in September. Few flutes were recorded aside from those mapped in September. This indicates that either in past seasons, conditions had not been favourable for formation, or that preservation was poor. The latter theory is supported by the lack of remaining evidence of the snowbank squeeze ridges in September. The poor preservation of these landforms highlights how they may be missed in other studies and the need for further research in this area. (Less)
Please use this url to cite or link to this publication:
author
Hamilton-Foyn, Alexander LU
supervisor
organization
course
GEOR02 20192
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Geomorphological Mapping, Structure from Motion, Glacial Landforms, Ice-Marginal Landforms, Landform Preservation, Hardangerjøkulen, Norway
publication/series
Dissertations in Geology at Lund University
report number
585
language
English
id
9013731
date added to LUP
2020-06-08 13:07:04
date last changed
2020-06-08 13:07:04
@misc{9013731,
  abstract     = {{This study presents a detailed investigation into the evolution of sedimentary landforms over an ablation season at Blåisen, an outlet of the Hardangerjøkulen Icecap, Norway. The two visits to Blåisen, one each side of the ablation season, allowed the preservation and evolution of the landforms to be studied. Much research is conducted studying glacial landforms, which are key in our understanding of past and future ice behaviour. This is important in researching the past, present and future response of the cryosphere to climate forcing, and the impact of such changes. A smaller portion of glacial geomorphological studies are now conducted using predominantly fieldwork with even fewer making repeated visits to sites in short succession. Many now use remote sensing which, while being a powerful tool to understand ice behaviour, means that smaller scale features (both in the temporal and spatial sense) may be missed. An awareness of what may be missing when studying forelands that are a few years to many millennia old is important to gaining a more holistic understanding of the ice behaviour and the processes occurring. This study focuses on the younger landforms in the immediate vicinity of the ice margin. GPS mapping, field observations and Structure from Motion Photogrammetry was used over two visits to Blåisen in June and September to identify four such landform types: snowbank squeeze moraines, flutes, minor moraines and an ice-cored wedged shaped ridge system (called a sediment wedge in this study after its characteristic shape).
The foreland of Blåisen was characterised by a number of areas where a reverse bedrock was present (bedrock that slopes in the opposite direction to ice flow); this had the effect of inhibiting drainage leading to saturated sediments around the ice margin. These sediments are easily deformable, so play an important role in the formation of the Snowbank Squeeze Moraines, Flutes, Minor Moraines in particular. The processes of formation are explored using the geomorphological and sedimentological evidence to devise genesis and evolution models for each landform type. The model for the formation of the sediment wedge presents freeze-on as a prominent mechanism, facilitating the transport of debris in a band from the base of the glacier to the margin where, due to differential melting, the underlying ice is isolated from the rest of the glacier. Snowbank Squeeze Moraines were observed as ridges of sediment protruding out of the snow in June formed by the deformation of sediments between the ice margin and the winter snowbank lying over the margin. The ‘squeeze’ form of snowbank moraines has not been widely documented in part due to their poor preservation, illustrated by the lack of remaining evidence for them in September. Few flutes were recorded aside from those mapped in September, indicating that either in past seasons, conditions had not been favourable for formation, or that preservation was poor. The latter is supported by the lack of remaining evidence of the snowbank squeeze ridges in September. The poor preservation of these landforms highlights how they may be missed in other studies and the need for further research in this area.}},
  author       = {{Hamilton-Foyn, Alexander}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Foreland evolution of Blåisen, Norway, over the course of an ablation season}},
  year         = {{2020}},
}