Observations on Icelandic Polygon Surfaces and Palsa Areas. Photo Interpretation and Field Studies

Friedman, J. D.; Johansson, C. E.; Oskarsson, N.; Svensson, Harald; Thorarinsson, S.; Williams, R. S.

doi:10.2307/520785

Cited by 39 publications

(11 citation statements)

References 4 publications

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“…This boundary probably relates to the permafrost table as water within the active layer would percolate down to and accumulate at that level [ Boulton et al ., ; Bennett , ; Schomacker and Kjær , ]. This can be supported by the presence of the palsas in the Þjórsárver peat bog just distal to the Múlar moraine, which indicate discontinuous permafrost in the area [ Friedman et al ., ]. As temperatures in Iceland were generally 1–2° lower during the LIA [ Guðmundsson , ; Kirkbride and Dugmore , ], the permafrost was likely somewhat thicker and more extensive when the Múlar moraine was formed.…”

Section: Discussionmentioning

confidence: 99%

Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge‐type glacier Múlajökull, Iceland

et al. 2015

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The internal architecture and structural evolution of the Arnarfellsmúlar terminal moraine at Múlajökull, a surge-type glacier in central Iceland, is described in order to demonstrate submarginal and proglacial glaciotectonic processes during glacier surging, as well as constraining the age of the maximum extent of the glacier. The moraine is 4-7 m high, 50-100 m wide, and composed of a highly deformed sequence of loess, peat, and tephra that is draped by till up to the crest. The internal architecture is dominated by steep, high-amplitude overturned folds and thrusts in the crest zone but open, low-amplitude folds on the distal slope. Section balancing suggests a basal detachment (décollement) depth of 1.4 m and a total horizontal shortening of around 59%. This implies that the glacier coupled to the foreland about 70 m up glacier from its terminal position to initiate the formation of the moraine. The structural evolution is polyphase in that the formation commenced with low-amplitude open folding of the foreland, followed by overfolding and piggyback thrusting. Radiocarbon dating and analysis of tephra layers, along with historical references, indicate that the most likely time of moraine formation was between A.D. 1717 and 1760, which suggests that Múlajökull had its Little Ice Age maximum and most extensive surge earlier than many other surge-type glaciers in Iceland.

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Section: Discussionmentioning

confidence: 99%

Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge‐type glacier Múlajökull, Iceland

et al. 2015

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“…Many of the rim‐ridges, which are up to 0.8 m high and 10–15 m in diameter, surround ponds or minor lakes. They have been interpreted as periglacial landforms and are thought to represent collapsed palsas (Todtmann 1955, 1960; Friedman et al 1971; French 1996; Ravn 2006; Benediktsson et al 2008; Kjær et al 2008). Evans et al (2007) map these features as being of paraglacial origin, though without providing data to substantiate that interpretation.…”

Section: Settingmentioning

confidence: 99%

Formation of submarginal and proglacial end moraines: implications of ice‐flow mechanism during the 1963–64 surge of Brúarjökull, Iceland

Benediktsson¹,

Inǵólfsson²,

Schomacker³

et al. 2009

Boreas

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The morphology, sedimentology and architecture of an end moraine formed by a ∼9 km surge of Brúarjökull in 1963–64 are described and related to ice‐marginal conditions at surge termination. Field observations and accurate mapping using digital elevation models and high‐resolution aerial photographs recorded at surge termination and after the surge show that commonly the surge end moraine was positioned underneath the glacier snout by the termination of the surge. Ground‐penetrating radar profiles and sedimentological data reveal 4–5 m thick deformed sediments consisting of a top layer of till overlying gravel and fine‐grained sediments, and structural geological investigations show that the end moraine is dominated by thrust sheets. A sequential model explaining the formation of submarginal end moraines is proposed. The hydraulic conductivity of the bed had a major influence on the subglacial drainage efficiency and associated porewater pressure at the end of the surge, thereby affecting the rates of subglacial deformation. High porewater pressure in the till decreased its shear strength and raised its strain rate, while low porewater pressure in the underlying gravel had the opposite effect, such that the gravel deformed more slowly than the till. The principal velocity component was therefore located within the till, allowing the glacier to override the gravel thrust sheets that constitute the end moraine. The model suggests that the processes responsible for the formation of submarginal end moraines are different from those operating during the formation of proglacial end moraines.

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“…[3] So far, only a few systematic studies concerning mountain permafrost in Iceland have been published. The literature is focused on sporadic permafrost connected to palsa formations [e.g., Friedman et al, 1971;Thórhallsdóttir, 1996] and geomorphological features indicating extensive periglacial activity [e.g., Friedman et al, 1971;Schunke, 1974;Thorarinsson, 1964;Van Vliet-Lanoë et al, 1998]. A range of borehole temperature measurements exist in Ice-land, most of which are related to geothermal energy extraction [e.g., Arnórsson, 1995a], but to our knowledge there is no record of mountain permafrost being determined from boreholes.…”

Section: Introductionmentioning

confidence: 99%

Thermal characteristics and impact of climate change on mountain permafrost in Iceland

et al. 2007

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[1] This study contains the first quantitative description of mountain permafrost in Iceland, obtained through analysis of four ground temperature time series from recently established shallow boreholes at high altitude ($900 m above sea level) in central and eastern Iceland. Permafrost is present at three of the four boreholes, where temperatures range from À2°to 0°C. During the data-logging period, 2004-2006, the thickness of the active layer at the individual sites varied between less than 2 m and more than 5 m, mainly owing to differences in near-surface ice content. The ground temperature profiles are nonlinear, with near-surface temperature perturbations considered to be related to a recent warming of the ground surface. At the one nonpermafrost site the insulating influence of winter snow cover is more pronounced. A one-dimensional heat-conduction model was calibrated using ground temperature measurements and driven by surface temperature time series. The model results reproduce the measured ground temperature pattern well. This simplified model, simulating the results of possible future climate scenarios, indicates that permafrost degradation will occur at these sites within decades, depending on climate scenarios chosen and subsurface ice content.

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Observations on Icelandic Polygon Surfaces and Palsa Areas. Photo Interpretation and Field Studies

Cited by 39 publications

References 4 publications

Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge‐type glacier Múlajökull, Iceland

Architecture and structural evolution of an early Little Ice Age terminal moraine at the surge‐type glacier Múlajökull, Iceland

Formation of submarginal and proglacial end moraines: implications of ice‐flow mechanism during the 1963–64 surge of Brúarjökull, Iceland

Thermal characteristics and impact of climate change on mountain permafrost in Iceland

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