Advanced

Dead-Ice Under Different Climate Conditions: Processes, Landforms, Sediments and Melt Rates in Iceland and Svalbard

Schomacker, Anders LU (2007) In LUNDQUA Thesis 59.
Abstract (Swedish)
Popular Abstract in Swedish

Recenta dödismiljöer framför Brúarjökull-glaciären på Island och Holmströmbreen på Svalbard har undersökts med speciellt fokus på landforms- och sedimentgenes samt kvantifiering av dödisavsmältningen. Fältmätningar, studier av tidsserier av flyg? och satellitbilder samt digitala terrängmodeller är dataunderlaget för kvantifieringen av dödisavsmältningen. Sedimentologiska och geomorfologiska data insamlades i fält och genom flygbildstolkning. Olika mått på dödisavsmältning (?backwasting?, ?downwasting?, utbredningen av issjöar, reträtten av glaciärfronter och uttunningen av glaciärer) jämförs med lokala temperaturserier, vilka går ända tillbaka till den tid instrumentmätningar började.

... (More)
Popular Abstract in Swedish

Recenta dödismiljöer framför Brúarjökull-glaciären på Island och Holmströmbreen på Svalbard har undersökts med speciellt fokus på landforms- och sedimentgenes samt kvantifiering av dödisavsmältningen. Fältmätningar, studier av tidsserier av flyg? och satellitbilder samt digitala terrängmodeller är dataunderlaget för kvantifieringen av dödisavsmältningen. Sedimentologiska och geomorfologiska data insamlades i fält och genom flygbildstolkning. Olika mått på dödisavsmältning (?backwasting?, ?downwasting?, utbredningen av issjöar, reträtten av glaciärfronter och uttunningen av glaciärer) jämförs med lokala temperaturserier, vilka går ända tillbaka till den tid instrumentmätningar började.



En geomorfologisk karta i skala 1:16 000 över Brúarjökull-området ritades med hjälp av digital flygbildstolkning och analys av terrängmodeller i hög upplösning. Kartan har använts som stöd för tolkningen av landformer och sediment och gav samtidig en överblick över glaciärsvämningslandskapet vid Brúarjökull, ett resultat av särskilt snabba glaciärframstötar.



En bildningsmodell för drumliner med kärnor av is togs fram med hjälp av data från undersökningarna vid Brúarjökull. Modellen indikerar att sådana drumliner disintegrerar till kulliga dödismoräner om kärnan smälter bort.



Tre fältsäsonger och analyser av multi-temporala terrängmodeller och flygbilder har avslöjat att flera dödisgenerationer existerar framför Brúarjökull. Smältningen av dessa dödiskroppar har kvantifierats och visar att smältningen under det nuvarande klimatet är så långsam att en komplett utsmältning är osannolik. Några av dödiskropparna ?återvinns? i nya landformer med iskärnor därför att deras totala utsmältningstid är längre än viloperioden i svämningscykeln. Sett över lång tid orsakar dödissmältningen vid Brúarjökull en sänkning av terrängytan med 0.10-0.18 m/år.



Framför Holmströmbreens stagnerade glaciärfront har ett stort dödisområde med iskärnemoräner, rullstensåsar och kames bildats sedan slutet av Lilla Istiden. Sett över lång tid fortskrider dödissmältningen med en sänkning av ytan på 0.9 m/år. Backwasting av isslänter och massrörelser av sediment exponerar hela tiden ny dödis och hindrar därvid ? till skillnad från vad som sker vid Brúarjökull ? att ett isolerande sedimenttäcke ackumuleras på isen. Det mest markanta resultatet av dödisavsmältningen är utvecklingen av en stor ändmorändämd issjö, där sediment från isslänterna runt sjön ackumuleras.



Dödissmältning under olika klimatförhållanden diskuteras i avhandlingen med fokus på smälthastigheter, sediment- och landformsgenes. Likadana processer pågår med nästan samma hastigheter i olika klimat. Fossila dödisavlagringer ger därför ganska lite information om miljön vid avlagringstilfället. Glacialdynamiskt sett indikerar dödisavlagringar stagnation av materialtäckta glaciärer. (Less)
Abstract
Modern dead-ice environments in the glacier forefields of Brúarjökull, Iceland and Holmströmbreen, Svalbard were investigated with focus on landform and sediment genesis, as well as quantification of melting. Field monitoring and studies of multi-temporal aerial photographs, satellite imagery, and Digital Elevation Models (DEMs) provided data for the melting quantification. Sedimentological and geomorphological data were achieved through field investigations and image analyses.



Different measures for dead-ice melting (backwasting, downwasting, ice-walled lake area, glacier retreat and thinning) are assessed in relation to local air temperature data going back to the beginning of the instrumental period.

... (More)
Modern dead-ice environments in the glacier forefields of Brúarjökull, Iceland and Holmströmbreen, Svalbard were investigated with focus on landform and sediment genesis, as well as quantification of melting. Field monitoring and studies of multi-temporal aerial photographs, satellite imagery, and Digital Elevation Models (DEMs) provided data for the melting quantification. Sedimentological and geomorphological data were achieved through field investigations and image analyses.



Different measures for dead-ice melting (backwasting, downwasting, ice-walled lake area, glacier retreat and thinning) are assessed in relation to local air temperature data going back to the beginning of the instrumental period.



A geomorphological map in scale 1:16 000 of the forefield of the surge-type glacier Brúarjökull was produced through digital aerial photograph interpretation and high-resolution DEM analyses. The map was used for the interpretation of landforms and sediments, and provided an overview of the surging glacier landsystem at Brúarjökull.



A conceptual model for the formation of transitional-state ice-cored landforms ? ice-cored drumlins ? was also constructed, based on the research in the Brúarjökull forefield. After a complete melting, the model proposes that such drumlins will disintegrate into patches of hummocky dead-ice moraine.



Three years of fieldwork combined with analyses of multi-temporal DEMs and aerial photographs revealed that multiple generations of ice-cored moraines are currently exposed to melting at Brúarjökull. Quantifying the melting progression suggests that in the current climate, a complete de-icing of ice-cored landforms is not likely to occur. Some dead-ice bodies are recycled into new ice-cored landforms, because the total melt-out time exceeds the duration of the quiescent period in the surge cycles. Long-term surface lowering due to dead-ice melting takes place with a rate of c. 0.10-0.18 m/yr.



At the stagnant snout of Holmströmbreen, an extensive dead-ice area with ice-cored moraines, eskers and kames has developed since the Little Ice Age glacial maximum. Backwasting of ice-cored slopes and mass-movement processes continuously expose new dead-ice and prevents the build-up of an insulating debris-cover. Currently dead-ice melting progresses with a long-term surface lowering rate of c. 0.9 m/yr. The most prominent impact of dead-ice melting is the development of an extensive ice-walled, moraine-dammed lake receiving sediment from the adjacent slopes.



Based on a literature review and the results presented here, dead-ice melting in different climatic settings is discussed, with focus on melt rates and sediment-landform genesis. Because identical processes operate with similar rates in different climates, dead-ice deposits provide little information on the climate at the time of deposition. The glaciodynamic significance of dead-ice deposits is that of stagnation of debris-covered glaciers. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Dowdeswell, Julian, Scott Polar Research Institute, University of Cambridge
organization
publishing date
type
Thesis
publication status
published
subject
keywords
klimatologi, glacier, dead-ice, surge, ice-cored, Little Ice Age, fysisk geografi, Geologi, Geology, Svalbard, Iceland, Sedimentology, cartography, pedology, geomorphology, Sedimentologi, Physical geography, geomorfologi, marklära, kartografi, climatology
in
LUNDQUA Thesis
volume
59
pages
25 pages
publisher
Quaternary Sciences, Department of Geology, Lund University
defense location
Pangea Geocentrum II Lunds Universitet Geologiska Institutionen Sölvegatan 12 223 62 Lund
defense date
2007-10-12 13:15
external identifiers
  • scopus:57349129595
ISSN
0281-3033
ISBN
978-91-86746-92-6
language
English
LU publication?
yes
id
a12af9cf-4e8a-4a3f-9418-635c78b712c5 (old id 548888)
date added to LUP
2007-09-06 16:01:12
date last changed
2017-01-01 07:16:54
@phdthesis{a12af9cf-4e8a-4a3f-9418-635c78b712c5,
  abstract     = {Modern dead-ice environments in the glacier forefields of Brúarjökull, Iceland and Holmströmbreen, Svalbard were investigated with focus on landform and sediment genesis, as well as quantification of melting. Field monitoring and studies of multi-temporal aerial photographs, satellite imagery, and Digital Elevation Models (DEMs) provided data for the melting quantification. Sedimentological and geomorphological data were achieved through field investigations and image analyses.<br/><br>
<br/><br>
Different measures for dead-ice melting (backwasting, downwasting, ice-walled lake area, glacier retreat and thinning) are assessed in relation to local air temperature data going back to the beginning of the instrumental period.<br/><br>
<br/><br>
A geomorphological map in scale 1:16 000 of the forefield of the surge-type glacier Brúarjökull was produced through digital aerial photograph interpretation and high-resolution DEM analyses. The map was used for the interpretation of landforms and sediments, and provided an overview of the surging glacier landsystem at Brúarjökull.<br/><br>
<br/><br>
A conceptual model for the formation of transitional-state ice-cored landforms ? ice-cored drumlins ? was also constructed, based on the research in the Brúarjökull forefield. After a complete melting, the model proposes that such drumlins will disintegrate into patches of hummocky dead-ice moraine.<br/><br>
<br/><br>
Three years of fieldwork combined with analyses of multi-temporal DEMs and aerial photographs revealed that multiple generations of ice-cored moraines are currently exposed to melting at Brúarjökull. Quantifying the melting progression suggests that in the current climate, a complete de-icing of ice-cored landforms is not likely to occur. Some dead-ice bodies are recycled into new ice-cored landforms, because the total melt-out time exceeds the duration of the quiescent period in the surge cycles. Long-term surface lowering due to dead-ice melting takes place with a rate of c. 0.10-0.18 m/yr.<br/><br>
<br/><br>
At the stagnant snout of Holmströmbreen, an extensive dead-ice area with ice-cored moraines, eskers and kames has developed since the Little Ice Age glacial maximum. Backwasting of ice-cored slopes and mass-movement processes continuously expose new dead-ice and prevents the build-up of an insulating debris-cover. Currently dead-ice melting progresses with a long-term surface lowering rate of c. 0.9 m/yr. The most prominent impact of dead-ice melting is the development of an extensive ice-walled, moraine-dammed lake receiving sediment from the adjacent slopes.<br/><br>
<br/><br>
Based on a literature review and the results presented here, dead-ice melting in different climatic settings is discussed, with focus on melt rates and sediment-landform genesis. Because identical processes operate with similar rates in different climates, dead-ice deposits provide little information on the climate at the time of deposition. The glaciodynamic significance of dead-ice deposits is that of stagnation of debris-covered glaciers.},
  author       = {Schomacker, Anders},
  isbn         = {978-91-86746-92-6},
  issn         = {0281-3033},
  keyword      = {klimatologi,glacier,dead-ice,surge,ice-cored,Little Ice Age,fysisk geografi,Geologi,Geology,Svalbard,Iceland,Sedimentology,cartography,pedology,geomorphology,Sedimentologi,Physical geography,geomorfologi,marklära,kartografi,climatology},
  language     = {eng},
  pages        = {25},
  publisher    = {Quaternary Sciences, Department of Geology, Lund University},
  school       = {Lund University},
  series       = {LUNDQUA Thesis},
  title        = {Dead-Ice Under Different Climate Conditions: Processes, Landforms, Sediments and Melt Rates in Iceland and Svalbard},
  volume       = {59},
  year         = {2007},
}