Journal articles on the topic 'Glacial ice flow'
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Shangguan, Donghui, Da Li, Yongjian Ding, Jun Liu, Muhammad Naveed Anjum, Yaojun Li, and Wanqin Guo. "Determining the Events in a Glacial Disaster Chain at Badswat Glacier in the Karakoram Range Using Remote Sensing." Remote Sensing 13, no. 6 (March 18, 2021): 1165. http://dx.doi.org/10.3390/rs13061165.
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The Karakoram mountain range is prone to natural disasters such as glacial surging and glacial lake outburst flood (GLOF) events. In this study, we aimed to document and reconstruct the sequence of events caused by glacial debris flows that dammed the Immit River in the Hindu Kush Karakoram Range on 17 July 2018. We used satellite remote sensing and field data to conduct the analyses. The order of the events in the disaster chain were determined as follows: glacial meltwater from the G2 glacier (ID: G074052E36491N) transported ice and debris that dammed the meltwater at the snout of the G1 glacier (ID: G074103E36480N), then the debris flow dammed the Immit River and caused Lake Badswat to expand. We surveyed the extent of these events using remote sensing imagery. We analyzed the glaciers’ responses to this event chain and found that the glacial debris flow induced G1 to exhibit accelerating ice flow in parts of the region from 25 July 2018 to 4 August 2018. According to the records from reanalysis data and data from the automatic weather station located 75 km from Lake Badswat, the occurrence of this disaster chain was related to high temperatures recorded after 15 July 2018. The chains of events caused by glacially related disasters makes such hazards more complex and dangerous. Therefore, this study is useful not only for understanding the formation of glacial disaster chains, but also for framing mitigation plans to reduce the risks for vulnerable downstream/upstream residents.
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Sharpe, David R. "Late Glacial landforms of Wollaston Peninsula, Victoria Island, Northwest Territories: product of ice-marginal retreat, surge, and mass stagnation." Canadian Journal of Earth Sciences 25, no. 2 (February 1, 1988): 262–79. http://dx.doi.org/10.1139/e88-029.
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An analysis of glacial landforms on a regional scale leads to an interpretation of the dynamics of Late Wisconsinan glaciation on Wollaston Peninsula, Victoria Island, Northwest Territories. The glacial record is dominated by four adjacent belts of landforms: (I) ground moraine (till plains and ice-marginal drainage features), (II) hummocky moraine, (III) lateral and shear moraine, and (IV) streamlined landforms. The landform belts are considered as representing four distinct glacial ice conditions or regimes: (1) ice-margin retreat during extending flow of thin, active ice; (2) marginal ice stagnation following compressional flow; (3) a surging ice margin producing massive shear moraines; and (4) large-scale flooding and mass ice stagnation following a surge. These landform belts were arranged in zones by topographically controlled glacial dynamics, the latter two defining a former ice stream.Glaciological inferences can be extended by examining the sediments and processes that produced each landform set. Ground-moraine sediments were produced mainly subglacially from melt out or lodgment of glacial debris. Hummocky moraine resulted from debris flow and meltwater deposition controlled by ice, from resedimentation by sediment gravity flow, and from slump. Compressional shearing stacked thick deposits of drift prior to resedimentation. Simple lateral or end moraines may comprise interbedded sediment gravity flows deposited at static ice margins. Deformed lateral moraines resulted from intense marginal compressive flow that sheared and stacked thick, coarse sediment ridges or plates. This lateral shearing may be attributed to streaming or large ice surges. Drumlin exposures showed undeformed, interbedded, stratified sediments that appear to have accumulated in a subglacial cavity; there is no deformation related to high subglacial stress. Subglacial meltwater floods may have followed glacier surge. The greatly extended and thinner ice mass produced by the surge melted in place as clean (debris-free) ice.
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Ershkov, Sergey, and Dmytro Leshchenko. "Revisiting Glacier Dynamics for Stationary Approximation of Plane-Parallel Creeping Flow." Mathematical Modelling of Engineering Problems 8, no. 5 (October 31, 2021): 721–26. http://dx.doi.org/10.18280/mmep.080506.
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We have presented in this analytical research the revisiting of approach for mathematical modeling the Glacier dynamics in terms of viscous-plastic theory of 2-dimensional movements within (x, y)-plane in cartesian coordinates. The stationary creeping approximation for the plane-parallel flow of slowly moving glacial ice on absolutely flat surface without any inclination has been considered. Even in such simple formulation, equations of motion that governs by the dynamics of viscous-plastic flow of glacial ice is hard to be solved analytically. We have succeeded in obtaining analytical expression for the components of velocity in Ox-direction of motion for slowly moving glacial ice (Ox-axis coincides to the initial main direction of slowly moving glacial ice). Restrictions on the form of flow stem from the continuity equation as well as from the special condition for non-Newtonian (viscous-plastic) flow have been used insofar.
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Barnett, Peter J., and Paul F. Karrow. "Ice-marginal sedimentation and processes of diamicton deposition in large proglacial lakes, Lake Erie, Ontario, Canada." Canadian Journal of Earth Sciences 55, no. 7 (July 2018): 846–62. http://dx.doi.org/10.1139/cjes-2017-0006.
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Detailed studies of coastal cliff exposures through two end moraines form the basis for a model of ice-marginal sedimentation in large ice-contact glacier-fed lakes. The input to the ice-marginal environment directly from the glacier included subglacial till and subaquatic flow tills. The subaquatic flow till (thinly bedded diamicton) was deposited in an apron (up to 1 km wide) along the ice margin. An upward gradient of pore-water pressure immediately beyond the ice margin, causing heaving and dilation of the sediments, initiated debris flows of glacially derived debris (subaquatic flow tills). Most of the stratified sediments in the ice-marginal zone entered the lake by way of a large proglacial stream. Sedimentation was dominated by quasi- or near-continuous density underflows that resulted in the deposition of a sequence of thick rhythmites. The glacier in the Lake Erie basin most likely behaved like an ice stream, with its movement controlled predominantly by a deforming bed of glacial debris, separating the glacier sole from underlying predeposited sediments. The deforming bed is preserved as a massive diamicton layer, interpreted here as subglacially deposited till.
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Seguinot, Julien, Susan Ivy-Ochs, Guillaume Jouvet, Matthias Huss, Martin Funk, and Frank Preusser. "Modelling last glacial cycle ice dynamics in the Alps." Cryosphere 12, no. 10 (October 10, 2018): 3265–85. http://dx.doi.org/10.5194/tc-12-3265-2018.
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Abstract. The European Alps, the cradle of pioneering glacial studies, are one of the regions where geological markers of past glaciations are most abundant and well-studied. Such conditions make the region ideal for testing numerical glacier models based on simplified ice flow physics against field-based reconstructions and vice versa. Here, we use the Parallel Ice Sheet Model (PISM) to model the entire last glacial cycle (120–0 ka) in the Alps, using horizontal resolutions of 2 and 1 km. Climate forcing is derived using two sources: present-day climate data from WorldClim and the ERA-Interim reanalysis; time-dependent temperature offsets from multiple palaeo-climate proxies. Among the latter, only the European Project for Ice Coring in Antarctica (EPICA) ice core record yields glaciation during marine oxygen isotope stages 4 (69–62 ka) and 2 (34–18 ka). This is spatially and temporally consistent with the geological reconstructions, while the other records used result in excessive early glacial cycle ice cover and a late Last Glacial Maximum. Despite the low variability of this Antarctic-based climate forcing, our simulation depicts a highly dynamic ice sheet, showing that Alpine glaciers may have advanced many times over the foreland during the last glacial cycle. Ice flow patterns during peak glaciation are largely governed by subglacial topography but include occasional transfluences through the mountain passes. Modelled maximum ice surface is on average 861 m higher than observed trimline elevations in the upper Rhône Valley, yet our simulation predicts little erosion at high elevation due to cold-based ice. Finally, despite the uniform climate forcing, differencesin glacier catchment hypsometry produce a time-transgressive Last Glacial Maximum advance, with some glaciers reaching their modelled maximum extent as early as 27 ka and others as late as 21 ka.
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Parent, Michel, Serge J. Paradis, and Éric Boisvert. "Ice-flow patterns and glacial transport in the eastern Hudson Bay region: implications for the late Quaternary dynamics of the Laurentide Ice Sheet." Canadian Journal of Earth Sciences 32, no. 12 (December 1, 1995): 2057–70. http://dx.doi.org/10.1139/e95-159.
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Recent field surveys in the eastern Hudson Bay region have led to the discovery of regional ice-flow sequences that require a significant reassessment of the late Quaternary dynamics of the Laurentide Ice Sheet. Two regional ice-flow phases can be recognized from till compositional data and from crosscutting relationships observed on striated bedrock surfaces: the oldest is directed toward the northwest and north-northwest, while the youngest is directed toward the west and includes a late-glacial deflection toward the southwest. The wide regional distribution of striae formed during the early northwestward glacial movement together with the recognition of palimpsest glacial dispersal trains associated with this phase suggest that it was a long-lived, time-transgressive regional event. The ensuing glacial movement is a regionally dominant westward ice-flow phase during which several large glacial dispersal trains were formed downglacier from distinctive bedrock sources. The largest of these trains extends westward over a distance of 120 km from Lac à l'Eau Claire to Hudson Bay. Regional glacial transport data as well as glacial and deglacial landforms indicate that this was a long-lived glacial phase, likely lasting throughout the Late Wisconsinan glacial maximum and until déglaciation about 8000 BP. The erosional and depositional record of the northwestward ice-flow event is quite comparable to that of the ensuing glacial phase, and it is thus thought to represent the Early Wisconsinan glacial maximum. In view of the large regional extent of the northwestward ice-flow phase, it must postdate the early buildup of the ice sheet. Along the southeastern Hudson Bay coast, the Late Wisconsinan westward glacial movement was followed by a southwestward deflection that was likely caused by glacial streaming prior to 8000 BP in James Bay, in response to calving and surging into Glacial Lake Ojibway.
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Headley, R. M., and T. A. Ehlers. "Ice flow models and glacial erosion over multiple glacial–interglacial cycles." Earth Surface Dynamics 3, no. 1 (March 2, 2015): 153–70. http://dx.doi.org/10.5194/esurf-3-153-2015.
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Abstract. Mountain topography is constructed through a variety of interacting processes. Over glaciological timescales, even simple representations of glacial-flow physics can reproduce many of the distinctive features formed through glacial erosion. However, detailed comparisons at orogen time and length scales hold potential for quantifying the influence of glacial physics in landscape evolution models. We present a comparison using two different numerical models for glacial flow over single and multiple glaciations, within a modified version of the ICE-Cascade landscape evolution model. This model calculates not only glaciological processes but also hillslope and fluvial erosion and sediment transport, isostasy, and temporally and spatially variable orographic precipitation. We compare the predicted erosion patterns using a modified SIA as well as a nested, 3-D Stokes flow model calculated using COMSOL Multiphysics. Both glacial-flow models predict different patterns in time-averaged erosion rates. However, these results are sensitive to the climate and the ice temperature. For warmer climates with more sliding, the higher-order model yields erosion rates that vary spatially and by almost an order of magnitude from those of the SIA model. As the erosion influences the basal topography and the ice deformation affects the ice thickness and extent, the higher-order glacial model can lead to variations in total ice-covered area that are greater than 30% those of the SIA model, again with larger differences for temperate ice. Over multiple glaciations and long timescales, these results suggest that higher-order glacial physics should be considered, particularly in temperate, mountainous settings.
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Headley, R. M., and T. A. Ehlers. "Ice flow models and glacial erosion over multiple glacial–interglacial cycles." Earth Surface Dynamics Discussions 2, no. 1 (June 4, 2014): 389–428. http://dx.doi.org/10.5194/esurfd-2-389-2014.
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Abstract. Mountain topography is constructed through a variety of interacting processes. Over glaciological time scales, even simple representations of glacial-flow physics can reproduce many of the distinctive features formed through glacial erosion. However, detailed comparisons at orogen time and length scales hold potential for quantifying the influence of glacial physics in landscape evolution models. We present a comparison using two different numerical models for glacial flow over single and multiple glaciations, within a modified version of the ICE-Cascade landscape evolution model. This model calculates not only glaciological processes but also hillslope and fluvial erosion and sediment transport, isostasy, and temporally and spatially variable orographic precipitation. We compare the predicted erosion patterns using a modified SIA as well as a nested, 3-D Stokes-flow model calculated using COMSOL Multiphysics. Both glacial-flow models predict different patterns in time-averaged erosion rates. However, these results are sensitive to the climate and the ice temperature. For warmer climates with more sliding, the higher-order model has a larger impact on the erosion rate, with variations of almost an order of magnitude. As the erosion influences the basal topography and the ice deformation affects the ice thickness and extent, the higher-order glacial model can lead to variations in total ice-covered that are greater than 30%, again with larger differences for temperate ice. Over multiple glaciations and long-time scales, these results suggest that consideration of higher-order glacial physics may be necessary, particularly in temperate, mountainous settings.
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Sugden, David E. "James Croll (1821–1890): ice, ice ages and the Antarctic connection." Antarctic Science 26, no. 6 (November 13, 2014): 604–13. http://dx.doi.org/10.1017/s095410201400008x.
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AbstractThe thrust of this paper is that James Croll should be more generously lauded for his remarkable contribution to the study of ice ages, glacier flow and the nature of the Antarctic ice sheet. Croll was the first to calculate the link between fluctuations of the Earth’s orbit and glacial/interglacial cycles, and to identify the crucial role of positive feedback processes necessary to transform minor insolation changes into major climatic changes. He studied the mechanisms of glacier flow and explained flow over horizontal land surfaces at a continental scale, including the excavation of rock basins. Croll relied on a quantitatively based deductive approach. One of his most remarkable achievements was his study of the thickness, thermal regime and dynamics of the Antarctic ice sheet (1879). This contains important insights, which are relevant today, and yet the paper was published before anyone had landed on the continent!
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Punkari, Mikko. "Function of the ice streams in the Scandinavian ice sheet: analyses of glacial geological data from southwestern Finland." Transactions of the Royal Society of Edinburgh: Earth Sciences 85, no. 4 (1994): 283–302. http://dx.doi.org/10.1017/s0263593300002054.
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AbstractMapping of striae trends, macro-scale erosion forms, drumlins, morainic ridges, eskers, till fabric and boulder fans has facilitated reconstruction of glacial dynamics in terms of ice streams, marginal ice lobes and interlobate zones. Data were recorded in a computerised geographical information system (GIS).Data on oriented glaciogenic elements are compared with the evolving patterns of glacial flow. The oldest flow occurred at a distance of several hundred kilometres inside the ice margin, while the later flows were dependent on the dynamics of the ice streams and fan-shaped ice lobes. A model is developed for the zonation of subglacial processes such as erosion, deposition and till deformation beneath the ice sheet. Most of the glacial forms, as well as lower till, were generated in a zone of basal melting and fast ice flow which existed some hundred kilometres from the receding margin and was associated with the formation of ice streams. These results are consistent with recent reconstructions of basal hydrology using mathematical models.Ice streams were important for deglaciation dynamics. In the course of deglaciation, decreased shear stress on the water-saturated substratum resulted in ice-bed uncoupling which lowered the profile and accelerated flow in the ice streams. This did not happen in interstream areas as reflected by the glacial geomorphology typical of inactive ice.
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Huggel, Christian, Wilfried Haeberli, Andreas Kääb, Daniel Bieri, and Shaun Richardson. "An assessment procedure for glacial hazards in the Swiss Alps." Canadian Geotechnical Journal 41, no. 6 (December 1, 2004): 1068–83. http://dx.doi.org/10.1139/t04-053.
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Glacial hazards such as ice avalanches, glacial lake outburst floods, and debris flows have caused severe damage in populated mountain regions such as the Swiss Alps. Assessment of such hazards must consider basic glaciological, geomorphological, and hydraulic principles together with experience gained from previous events. An approach is presented here to assess the maximum event magnitude and probability of occurrence of glacial hazards. Analysis of magnitude is based on empirical relationships derived from published case histories from the Swiss Alps and other mountain regions. Probability of occurrence is difficult to estimate because of rapid changes in the nature of glacial systems, the low frequency of events, and the high complexity of the involved processes. Here, the probability is specified in qualitative and systematic terms based on indicators such as dam type, geometry, and freeboard height (for glacial lakes) and tendency of avalanche repetition, precursor events, and increased water supply to the glacier bed (for ice avalanche events). The assessment procedures are applied to a recent lake outburst with subsequent debris flow and to an ice avalanche in the Swiss Alps. The results yield reasonable event maxima that were not exceeded by actual events. The methods provide first-order assessments and may be applied in dynamic mountain environments where population and infrastructure growth require continuous evaluation of hazards.Key words: glacial hazards, lake outburst, debris flow, ice avalanche, hazard assessment procedure, probability of occurrence.
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Haldorsen, Sylvi, Michael Heim, Barrie Dale, Jon Y. Landvik, Martine van der Ploeg, Anton Leijnse, Otto Salvigsen, Jon Ove Hagen, and David Banks. "Sensitivity to long-term climate change of subpermafrost groundwater systems in Svalbard." Quaternary Research 73, no. 2 (March 2010): 393–402. http://dx.doi.org/10.1016/j.yqres.2009.11.002.
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Deep subpermafrost aquifers are highly climate-dependent, with the permafrost as an aquitard preventing groundwater recharge and discharge. A study from the high-arctic island of Spitsbergen, Svalbard, shows that during a glacial to interglacial phase, both the permafrost and the glacier regime will respond to climatic changes, and a glacier-fed groundwater flow system will vary accordingly. A full glaciation results in the melting of permafrost, and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers. These groundwater flow systems will mainly be localized to fjords and valleys and form low-lying terrestrial springs when the relative sea level drops during deglaciation due to glacio-isostatic rise. During an interglaciation, permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation. An already frozen spring system cannot reopen before the permafrost melts. Only groundwater springs related to permanently warm-based glacial ice will persist into the next glaciation. During a new glaciation, flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm-based ice causing permafrost thawing.
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Cohen, Denis, Fabien Gillet-Chaulet, Wilfried Haeberli, Horst Machguth, and Urs H. Fischer. "Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum." Cryosphere 12, no. 8 (August 7, 2018): 2515–44. http://dx.doi.org/10.5194/tc-12-2515-2018.
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Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km2. As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled three-dimensional, transient Stokes flow and heat transport model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (TJuly∼0∘C at the glacier terminus) and dry (∼10 % to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a−1 in the lobes and 50 to 250 m a−1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were >80 % in lobes and ∼60 % in valleys. Basal shear stress was very low in the lobes (0.03–0.1 MPa) and much higher in Alpine valleys (>0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several watts per square meter but on average 0.03 to 0.2 W m−2. Basal friction acted as a heat source at the bed of about 0.02 W m−2, 4 to 6 times less than the geothermal heat flow which is locally high (up to 0.12 W m−2). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice, which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice–climate interactions.
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Boulton, G. S., and K. E. Dobbie. "Consolidation of sediments by glaciers: relations between sediment geotechnics, soft-bed glacier dynamics and subglacial ground-water flow." Journal of Glaciology 39, no. 131 (1993): 26–44. http://dx.doi.org/10.1017/s0022143000015690.
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AbstractA theory of subglacial consolidation is developed which shows how the meltwater flux beneath a glacier leaves a consolidation signature from which many important glacier-dynamic properties can be inferred. Conditions under which water is discharged through channels or in a thin film at the ice—bed interface or by ground-water flow are discussed, and it is concluded that glaciers flowing over aquifers of high transmissibility can induce deep circulation patterns quite different from non-glacial circulation. Examples of glacial pre-consolidation profiles in sediments from The Netherlands and England are used to illustrate how basal melting rates, subglacial ground-water flow patterns, ice overburden, basal shear stress, ice-surface profile and the amount of sediment removed by erosion can be inferred.
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Boulton, G. S., and K. E. Dobbie. "Consolidation of sediments by glaciers: relations between sediment geotechnics, soft-bed glacier dynamics and subglacial ground-water flow." Journal of Glaciology 39, no. 131 (1993): 26–44. http://dx.doi.org/10.3189/s0022143000015690.
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AbstractA theory of subglacial consolidation is developed which shows how the meltwater flux beneath a glacier leaves a consolidation signature from which many important glacier-dynamic properties can be inferred. Conditions under which water is discharged through channels or in a thin film at the ice—bed interface or by ground-water flow are discussed, and it is concluded that glaciers flowing over aquifers of high transmissibility can induce deep circulation patterns quite different from non-glacial circulation. Examples of glacial pre-consolidation profiles in sediments from The Netherlands and England are used to illustrate how basal melting rates, subglacial ground-water flow patterns, ice overburden, basal shear stress, ice-surface profile and the amount of sediment removed by erosion can be inferred.
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Bell, Trevor, Robert J. Rogerson, and Flemming Mengel. "Reconstructed ice-flow patterns and ice limits using drift pebble lithology, outer Nachvak Fiord, northern Labrador." Canadian Journal of Earth Sciences 26, no. 3 (March 1, 1989): 577–90. http://dx.doi.org/10.1139/e89-049.
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The geology of outer Nachvak Fiord provides an opportunity to differentiate lithologies originating in the Churchill Structural Province (central and inner fiord) from those in the sedimentary Ramah Group and the Nain Structural Province (outer fiord). As a result, the distribution of glacial erratics from the central and inner fiord depicts the former presence of regional Laurentide ice in the outer fiord, whereas the distribution of glacial deposits characterized by locally derived lithologies delimits the area of local glacier expansion.Based upon these criteria, the suggestion is made that regional ice at some time covered the deeply weathered mountain summits (900 m asl) in outer Nachvak Fiord. A later advance, confined to the fiord and valleys, deposited the highest moraines and till (180–115 m asl) recorded in the area. On the basis of geomorphic relationships, this advance is considered a discrete glacial event, separate from a later glaciation that was responsible for moraines and sediments at lower elevations (130–80 m asl). Two hypotheses are presented to explain the character of glacial features and sediments in the lower valleys.Hypothesis I requires that regional ice advanced through the study area and floated as ice shelves in the outer fiord and adjacent distributary valley. Sea level at this time was approximately 70 m higher than at present. Radiocarbon dates and amino-acid ratios from the shells in associated marine and glaciomarine sediments suggest a Middle Wisconsinan age for this event. During the Late Wisconsinan, regional Laurentide ice was restricted to the inner fiord while the sea (29–40 m above present) occupied the outer fiord area. The expansion of local cirque glaciers in upland areas may have occurred during both regional glaciations.In hypothesis II, the Middle Wisconsinan was characterized by extensive local glacier activity, depositing predominantly local material in the lower valleys, south of the fiord. Related fossiliferous sediments (same as above) provide the dating framework for this event. Late Wisconsinan regional ice advanced to the outer fiord and entered the distributary valley south of the fiord. Till deposited during this event is distinguished from the earlier local glaciation by the predominance of regional lithologies. Both Middle and Late Wisconsinan glaciations resulted in the formation of ice-shelf moraines at similar elevations. This implies similar relative sea-level responses to loading of the crust during both events, and consequently it is suggested that regional Laurentide ice had also advanced during the Middle Wisconsinan.Neither hypothesis conforms to a recently proposed Late Wisconsinan ice model for northern Labrador that requires extensive regional ice coverage in the outer fiord and on the Labrador Shelf.
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Ross, Martin, Michel Parent, Beatriz Benjumea, and James Hunter. "The late Quaternary stratigraphic record northwest of Montréal: regional ice-sheet dynamics, ice-stream activity, and early deglacial events." Canadian Journal of Earth Sciences 43, no. 4 (April 1, 2006): 461–85. http://dx.doi.org/10.1139/e05-118.
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The Quaternary sediments of previously unstudied buried valleys and sections near Montréal are analyzed and other sites are revisited to further develop the stratigraphic framework of the St. Lawrence Lowland and to establish regional glacial and deglacial models. The southwest-trending buried valleys were investigated by stratigraphic drilling and high-resolution seismic profiling. The Quaternary succession consists, from base to top, of proximal glaciolacustrine sediments, two superposed till sheets (Argenteuil and Oka tills) of inferred Late Wisconsinan age, and Champlain Sea sediments. The glacial sediments of this sequence record an ice advance toward south (Argenteuil Till) followed by an abrupt ice-flow shift toward the southwest (Oka Till). Compositional and geomorphic data indicate that Oka Till is ubiquitous and is associated with a regional set of glacial landforms. The analysis of a regional digital elevation model in combination with published ice-flow indicators shows convergent flow patterns from the OttawaMontréalAdirondack regions toward the Lake Ontario basin. Landforms produced by the inferred ice stream are locally crosscut by southward-trending ice-flow features. Hence southward flow in the upper St. Lawrence Valley seemingly took place in two distinct contexts: (1) during full glacial conditions, as ice margins stood at or near the late glacial maximum limits, and (2) during late deglaciation, as a post-ice stream reequilibration mechanism. Early deglacial events in the study area were also characterized by subglacial meltwater channelling and erosion along the valleys, subaquatic outwash deposition in glacial Lake Candona, and rapid infill of the valleys during the early stages of the ensuing Champlain Sea.
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Huai, Baojuan, Minghu Ding, Songtao Ai, Weijun Sun, Yetang Wang, and Jiajia Gao. "Glacial Debris Flow Blockage Event (2018) in the Sedongpu Basin of the Yarlung Zangbo River, China: Occurrence Factors and Its Implications." Land 11, no. 8 (August 2, 2022): 1217. http://dx.doi.org/10.3390/land11081217.
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In this paper, the glacial debris flow blockage event, on 17 October 2018, in the Sedongpu basin of the Yarlung Zangbo River is taken as an example to analyse the occurrence and development of glacier hazards in this region. Multi-sources including remote sensing products, DEM, earthquake records and meteorological data were used to analyse the characteristics and mechanism of glacier hazards. The Elmer/Ice dynamic model was chosen to simulate the glacial surface velocity. It was found that topography and climate background determine that the hazard happens periodically. Based on the meteorological records of the Linzhi station, the warming rate was greater than 0.40 °C/10a during the period 1960–2017. The short-term heavy rainfall with daily values of 9.3 mm before the blockage event was also regarded as a factor. Both heavy rain and earthquake were triggering factors of the ice avalanche that led to the glacial debris flow. The glacier surface velocity of the Dongpu glacier simulated by Elmer/Ice model can reach 19 cm/d. This study has extensive applicability significance in glacier hazard mitigation under a changing climate.
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Levy, Joseph S., Caleb I. Fassett, John W. Holt, Reid Parsons, Will Cipolli, Timothy A. Goudge, Michelle Tebolt, et al. "Surface boulder banding indicates Martian debris-covered glaciers formed over multiple glaciations." Proceedings of the National Academy of Sciences 118, no. 4 (January 19, 2021): e2015971118. http://dx.doi.org/10.1073/pnas.2015971118.
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Glacial landforms, including lobate debris aprons, are a global water ice reservoir on Mars preserving ice from past periods when high orbital obliquity permitted nonpolar ice accumulation. Numerous studies have noted morphological similarities between lobate debris aprons and terrestrial debris-covered glaciers, an interpretation supported by radar observations. On Earth and Mars, these landforms consist of a core of flowing ice covered by a rocky lag. Terrestrial debris-covered glaciers advance in response to climate forcing driven by obliquity-paced changes to ice mass balance. However, on Mars, it is not known whether glacial landforms emplaced over the past 300 to 800 formed during a single, long deposition event or during multiple glaciations. Here, we show that boulders atop 45 lobate debris aprons exhibit no evidence of monotonic comminution but are clustered into bands that become more numerous with increasing latitude, debris apron length, and pole-facing flow orientation. Boulder bands are prominent at glacier headwalls, consistent with debris accumulation during the current Martian interglacial. Terrestrial glacier boulder bands occur near flow discontinuities caused by obliquity-driven hiatuses in ice accumulation, forming internal debris layers. By analogy, we suggest that Martian lobate debris aprons experienced multiple cycles of ice deposition, followed by ice destabilization in the accumulation zone, leading to boulder-dominated lenses and subsequent ice deposition and continued flow. Correlation between latitude and boulder clustering suggests that ice mass-balance works across global scales on Mars. Lobate debris aprons may preserve ice spanning multiple glacial/interglacial cycles, extending Mars climate records back hundreds of millions of years.
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Haemmig, Christoph, Matthias Huss, Hansrudolf Keusen, Josef Hess, Urs Wegmüller, Zhigang Ao, and Wubuli Kulubayi. "Hazard assessment of glacial lake outburst floods from Kyagar glacier, Karakoram mountains, China." Annals of Glaciology 55, no. 66 (2014): 34–44. http://dx.doi.org/10.3189/2014aog66a001.
Full textAbstract:
AbstractKyagar glacier is located in the Chinese Karakoram mountains. The glacier tongue entirely blocks the riverbed in the upper Shaksgam valley and impounds a glacial lake, which was the source of several violent and disastrous glacial lake outburst floods (GLOFs). A GLOF early warning system was implemented between 2011 and 2013. We present an integrative analysis of the hazard potential of Kyagar lake, taking into account the ice flow dynamics of Kyagar glacier as well as the recent surface mass-balance response to climate change. Comparison of two high-resolution digital elevation models (DEMs) for the ice dam shows surface lowering rates of >5ma– 1 between 2002 and 2011, leading to a significant reduction in the maximum potential lake volume. However, two DEMs covering the entire glacier for the period 2000–10 indicate mass gains in its central part, and flow speed measurements show an acceleration in this region. This pattern of local ice-thickness changes combined with varying ice flow velocities is typical for surge-type glaciers. The velocity of the glacier surface and of the ice dam between 2011 and 2012 are analyzed at high temporal and spatial resolution, based on feature tracking of synthetic aperture radar (SAR) images.
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Wintges, Theodor. "Studies On Crescentic Fractures and Crescentic Gouges with the Help of Close-range Photogrammetry." Journal of Glaciology 31, no. 109 (1985): 340–49. http://dx.doi.org/10.1017/s0022143000006687.
Full textAbstract:
Abstract Studies on cresceatic fractures and crescentic gouges were carried out in the central part of the Alpine piedmont glaciation and the Quaternary Alpine mountain ice sheet. The test sites were situated in the pro-glacial area of the Hornkees south Berliner Hütte (Oberer Zemmgrund, Zillertal, Tyrol, Austria). This is also the area of the former confluence with another glacier which flowed at about 90° to Hornkees during the late-glacial period. It was therefore possible to make a comparison between different older glacier systems, different flow directions, and different ice thicknesses. About 12 000 minor features were measured by close-range photogrammetry; the result was 240 pairs of stereophotographs which were interpreted on first-order equipment. The single forms were registered point by point by coordinates. It was therefore possible to obtain three-dimensionally registered forms. One important result was that the late-glacial and the post-glacial glaciers of the Zemmgrund produced minor features with a large variation in size. A further result was the definition of possible glacier-flow directions by interpretation of the different directions of crescentic fractures and crescentic gouges. By this means it was possible to obtain several working reconstructions of the late- and post-glacial stream lines of the merged glaciers.
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Wintges, Theodor. "Studies On Crescentic Fractures and Crescentic Gouges with the Help of Close-range Photogrammetry." Journal of Glaciology 31, no. 109 (1985): 340–49. http://dx.doi.org/10.3189/s0022143000006687.
Full textAbstract:
AbstractStudies on cresceatic fractures and crescentic gouges were carried out in the central part of the Alpine piedmont glaciation and the Quaternary Alpine mountain ice sheet. The test sites were situated in the pro-glacial area of the Hornkees south Berliner Hütte (Oberer Zemmgrund, Zillertal, Tyrol, Austria). This is also the area of the former confluence with another glacier which flowed at about 90° to Hornkees during the late-glacial period. It was therefore possible to make a comparison between different older glacier systems, different flow directions, and different ice thicknesses. About 12 000 minor features were measured by close-range photogrammetry; the result was 240 pairs of stereophotographs which were interpreted on first-order equipment. The single forms were registered point by point by coordinates. It was therefore possible to obtain three-dimensionally registered forms. One important result was that the late-glacial and the post-glacial glaciers of the Zemmgrund produced minor features with a large variation in size. A further result was the definition of possible glacier-flow directions by interpretation of the different directions of crescentic fractures and crescentic gouges. By this means it was possible to obtain several working reconstructions of the late- and post-glacial stream lines of the merged glaciers.
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Veillette, Jean J. "Ice-Flow Chronology and Palimpsest, Long-Distance Dispersal of Indicator Clasts, North of the St. Lawrence River Valley, Quebec." Glacial History 58, no. 2-3 (July 18, 2006): 187–216. http://dx.doi.org/10.7202/013138ar.
Full textAbstract:
Abstract An ice flow model, based on the distribution of distinctive Proterozoic erratics from the Lake Mistassini and Monts Otish sedimentary basins, and on the mapping of relict striations in a 230 000 km2 area located predominantly in Grenville Province, Québec, is presented to reconstruct the evolution of a large part of the Labrador Sector of the Laurentide Ice Sheet during the Wisconsinan. The results, were added to those of similar surveys carried out in the Abitibi region, and further north. Striated surfaces and indicator clasts from an early northwestward flow, overprinted by those from a widespread southeastward flow, and lastly by those from deglaciation flows toward the southwest, south, and southeast, revealed a complex sequence of events. The northwestward flow originated from a NE‑SW, early Wisconsinan, ice divide located in the Québec highlands, south of Lake Mistassini, that migrated to a position north of the lake, at the Last Glacial Maximum, to give rise to the widespread, southeastward ice flow, that left traces over a large part of Grenville Province. Deglaciation triggered a clockwise shift in ice-flow south of Lake Mistassini, and a counterclockwise shift, north of it. Inception of the northwestward flowing glacier probably results from the coalescence of ice caps formed at the highest elevations along a narrow fringe, north of and parallel to the St. Lawrence River Valley, and expansion toward the northwest suggests a similarity with the windward growth model of ice sheet expansion. The ice flow model has implications for mineral exploration methods based on the sampling of glacial sediments.
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ZHANG, GUOQING, TOBIAS BOLCH, SIMON ALLEN, ANDREAS LINSBAUER, WENFENG CHEN, and WEICAI WANG. "Glacial lake evolution and glacier–lake interactions in the Poiqu River basin, central Himalaya, 1964–2017." Journal of Glaciology 65, no. 251 (April 1, 2019): 347–65. http://dx.doi.org/10.1017/jog.2019.13.
Full textAbstract:
ABSTRACTDespite previous studies, glacier–lake interactions and future lake development in the Poiqu River basin, central Himalaya, are still not well understood. We mapped glacial lakes, glaciers, their frontal positions and ice flow from optical remote sensing data, and calculated glacier surface elevation change from digital terrain models. During 1964–2017, the total glacial-lake area increased by ~110%. Glaciers retreated with an average rate of ~1.4 km2 a−1 between 1975 and 2015. Based on rapid area expansion (>150%), and information from previous studies, eight lakes were considered to be potentially dangerous glacial lakes. Corresponding lake-terminating glaciers showed an overall retreat of 6.0 ± 1.4 to 26.6 ± 1.1 m a−1 and accompanying lake expansion. The regional mean glacier elevation change was −0.39 ± 0.13 m a−1 while the glaciers associated with the eight potentially dangerous lakes lowered by −0.71 ± 0.05 m a−1 from 1974 to 2017. The mean ice flow speed of these glaciers was ~10 m a−1 from 2013 to 2017; about double the mean for the entire study area. Analysis of these data along with climate observations suggests that ice melting and calving processes play the dominant role in driving lake enlargement. Modelling of future lake development shows where new lakes might emerge and existing lakes could expand with projected glacial recession.
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Daigneault, Robert-André, and Michel A. Bouchard. "Les écoulements et le transport glaciaires dans la partie septentrionale du Nunavik (Québec)." Canadian Journal of Earth Sciences 41, no. 8 (August 1, 2004): 919–38. http://dx.doi.org/10.1139/e04-048.
Full textAbstract:
In northern Nunavik, orientation of ice-flow features and dispersal patterns of lithologic indicators suggest three major regional ice-flow phases. The oldest ice-flow phase is related to the buildup of an outflow centre, the Ungava centre, over the high plateaux located north of the Povungnituk Hills. During that event, probably of Early Wisconsinan age, ice flows towards the south and southeast carried Cape Smith Belt rock fragments over a maximum distance of 65 km. The second phase is characterized by ice flow mainly towards the north from an outflow ice centre located south of the studied area (Payne centre). The most recent ice-flow phase is related to the presence of the northern extension of the New-Quebec ice divide. From that northwest-trending ice divide extending between Ivujivik and Lake Nantais, ice was flowing outward on the peninsula. The orientation of most of the ice-flow features and dispersal patterns is associated with that last ice flow. North of the Cape Smith Belt, glacial transport was at least 70 km. In Hudson Strait, ice-flow and glacial transport data support the existence of an eastward flowing ice stream.
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Flett, Verity, Louise Maurice, Andrew Finlayson, Andrew R. Black, Alan M. MacDonald, Jez Everest, and Martin P. Kirkbride. "Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland." Hydrology Research 48, no. 6 (February 17, 2017): 1666–81. http://dx.doi.org/10.2166/nh.2017.205.
Full textAbstract:
Abstract Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s−1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s−1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s−1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers.
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McMartin, Isabelle, and Penny J. Henderson. "Evidence from Keewatin (Central Nunavut) for Paleo-Ice Divide Migration*." Glacial History 58, no. 2-3 (July 18, 2006): 163–86. http://dx.doi.org/10.7202/013137ar.
Full textAbstract:
Abstract Ice directional indicators were compiled from extensive field mapping and air-photo interpretation in the Keewatin region of central Nunavut. The profusion of multi-faceted bedrock outcrops, intersecting striations, superimposed streamlined landforms, and stacked till units, particularly beneath the former Keewatin Ice Divide, is interpreted to be the result of the migration of the main ice divide in the region, by as much as 500 km between ice-flow phases, possibly through much of the Wisconsinan glaciation. This palimpsest glacial landscape reflects protection under an ice divide because of low-velocity basal sliding, and changes in flow velocity as a result of shifting ice flow centres. Relative ages of regional ice-flow sets were used to reconstruct multiple phases of paleo-ice flows, stemming from ice centres external to the region prior to or at LGM, and from a local ice divide throughout deglaciation. This work refutes previous interpretations of the age and stability of the Keewatin Ice Divide, and has implications for interpreting glacial dispersal trains and for mineral exploration in Keewatin.
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Baker, R. W. "The Role of Debris-Rich Ice in Flow Near the Margins of Glaciers (Abstract)." Annals of Glaciology 8 (1986): 201. http://dx.doi.org/10.1017/s026030550000152x.
Full textAbstract:
The margins of many ice sheets and ice caps are marked by the presence of alternating layers of debris-laden and clean ice. The role of this ice in flow and sediment transport near the margins of glaciers has been the subject of considerable controversy between glacial geologists and glaciologists for over three decades. Glacial geologists (Goldthwait, 1951, 1960, 1971, 1975; Bishop, 1957; Souchez, 1967, Boulton, 1970, 1972; Hambrey, 1976) commonly refer to the debris-bearing ice bands as “thrust planes” or “shear planes”, apparently seeing them as reverse faults which transport rock debris from the glacier bed to the surface in a “conveyor-belt-like” manner (Goldthwait, 1975, p. 192). As supporting evidence for the shear-plane mechanism, glacial geologists have offered only qualitative observations and none seem to have actually observed it in action. Glaciologists on the other hand, particularly Weertman (1961), Hooke (1968; 1973), and Hooke and Hudleston (1978), have objected to this concept on physical grounds and have presented convincing arguments for doubting that it is mechanically sound. In spite of the controversy surrounding it, the shear-plane mechanism has gained wide acceptance among geologists and physical geographers and has been perpetuated in recent years through a number of popular introductory geology and physical geography textbooks (e.g. Embleton and King, 1975; Judson, Deffeyes, and Hargraves, 1976; Leet, Judson, and Kauffman, 1978; Press and Siever, 1982; Hamblin; 1982).
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Whillans, I. M., and C. J. Van Der Veen. "New and improved determinations of velocity of Ice Streams B and C, West Antarctica." Journal of Glaciology 39, no. 133 (1993): 483–590. http://dx.doi.org/10.1017/s0022143000016373.
Full textAbstract:
Abstract Measurements of velocity have been made on and next to Ice Streams Β and C, West Antarctica. The results are more precise than previous work and constitute a 93% increase in the number of values. These velocities are used to describe the confluence of flow into the ice streams and the development of fast ice-stream flow. The onset of fast-streaming flow occurs in many separate tributaries that coalesce down-glacier into the major ice streams. For those inter-stream ridges that have been studied, the flow is consistent with steady state. Along Ice Stream B, gradients in longitudinal stress offer little resistance to the ice flow. The transition from basal-drag control to ice-shelf flow is achieved through reduced drag at the glacier base and increased resistance associated with lateral drag. Velocities in the trunk of Ice Stream C are nearly zero but those at the up-glacial head are similar to those at the head of Ice Stream B.
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Whillans, I. M., and C. J. Van Der Veen. "New and improved determinations of velocity of Ice Streams B and C, West Antarctica." Journal of Glaciology 39, no. 133 (1993): 483–590. http://dx.doi.org/10.3189/s0022143000016373.
Full textAbstract:
AbstractMeasurements of velocity have been made on and next to Ice Streams Β and C, West Antarctica. The results are more precise than previous work and constitute a 93% increase in the number of values. These velocities are used to describe the confluence of flow into the ice streams and the development of fast ice-stream flow. The onset of fast-streaming flow occurs in many separate tributaries that coalesce down-glacier into the major ice streams. For those inter-stream ridges that have been studied, the flow is consistent with steady state. Along Ice Stream B, gradients in longitudinal stress offer little resistance to the ice flow. The transition from basal-drag control to ice-shelf flow is achieved through reduced drag at the glacier base and increased resistance associated with lateral drag. Velocities in the trunk of Ice Stream C are nearly zero but those at the up-glacial head are similar to those at the head of Ice Stream B.
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Glasser, N. F., S. J. A. Jennings, M. J. Hambrey, and B. Hubbard. "Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?" Earth Surface Dynamics Discussions 2, no. 2 (July 31, 2014): 911–33. http://dx.doi.org/10.5194/esurfd-2-911-2014.
Full textAbstract:
Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.
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Sterckx, Arnaud, Jean-Michel Lemieux, and Rein Vaikmäe. "Representing Glaciations and Subglacial Processes in Hydrogeological Models: A Numerical Investigation." Geofluids 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/4598902.
Full textAbstract:
The specific impact of glacial processes on groundwater flow and solute transport under ice-sheets was determined by means of numerical simulations. Groundwater flow and the transport of δ18O, TDS, and groundwater age were simulated in a generic sedimentary basin during a single glacial event followed by a postglacial period. Results show that simulating subglacial recharge with a fixed flux boundary condition is relevant only for small fluxes, which could be the case under partially wet-based ice-sheets. Glacial loading decreases overpressures, which appear only in thick and low hydraulic diffusivity layers. If subglacial recharge is low, glacial loading can lead to underpressures after the retreat of the ice-sheet. Isostasy reduces considerably the infiltration of meltwater and the groundwater flow rates. Below permafrost, groundwater flow is reduced under the ice-sheet but is enhanced beyond the ice-sheet front. Accounting for salinity-dependent density reduces the infiltration of meltwater at depth. This study shows that each glacial process is potentially relevant in models of subglacial groundwater flow and solute transport. It provides a good basis for building and interpreting such models in the future.
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Gravenor, C. P. "Glacial tectonic and flow structures in glaciogenic deposits: a cautionary note." Bulletin of the Geological Society of Denmark 34 (May 31, 1985): 3–11. http://dx.doi.org/10.37570/bgsd-1985-34-01.
Full textAbstract:
Large scale displacement and deformation of bedrock and associated glacial deposits can be produced by both glacial tectonics and debris flows. Large scale deformation of glacial deposits not associated with displacement of underlying strata can be produced by both glacial tectonics and ice-contact processes. Smaller scale structures such as boudins, stringers of sand and silt and laminated diamictons can be produced by both glacial tectonics and flow processes. Examples of both large and small scale structures produced by flow are presented to emphasize the need for adequate criteria to determine the origin of these structures.
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Wilson, L., and J. W. Head. "Heat transfer in volcano–ice interactions on Earth." Annals of Glaciology 45 (2007): 83–86. http://dx.doi.org/10.3189/172756407782282507.
Full textAbstract:
AbstractThe very high temperature contrast between magma/ lava and water ice commonly leads to the assumption that significant melting will take place immediately upon magma/ lava ice contact, yet observations of active flows show little evidence of voluminous melting upon contact. We use analytical thermal models to reassess the efficiency with which heat can be transferred from magma to ice in three situations: lava flows erupted on top of glacial ice, sill intrusions beneath glacial ice evolving into subglacial lava flows and dyke intrusions into the interiors of glaciers. We find that the maximum ratios of thickness of ice that can be melted to the thickness of magmatic heat source are likely to be ∽2–5 for subaerial lava flows encroaching onto glaciers, ∽6–7 for subglacial lava flows and ∽10 for dykes intruded into glacial ice. Rates of ice melt production are not linear functions of time and flow thickness, however, and this may account for the observations of minimal immediate water release from beneath advancing lava flows. Field observations during future eruptions should be directed at measuring the temperature of released water.
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Dąbski, Maciej, Anna Zmarz, Mirosław Rodzewicz, Małgorzata Korczak-Abshire, Izabela Karsznia, Katarzyna Lach, Grzegorz Rachlewicz, and Katarzyna Chwedorzewska. "Mapping Glacier Forelands Based on UAV BVLOS Operation in Antarctica." Remote Sensing 12, no. 4 (February 14, 2020): 630. http://dx.doi.org/10.3390/rs12040630.
Full textAbstract:
The aim of this article is to show geomorphological mapping of remote Antarctic locations using images taken by a fixed-wing unmanned aerial vehicle (UAV) during the Beyond Visual Line of Sight (BVLOS) operations. We mapped landform assemblages developed in forelands of Ecology Glacier (EGF), Sphinx Glacier (SGF) and Baranowski Glacier (BGF) in Antarctic Specially Protected Area No. 128 (ASPA 128) on King George Island (South Shetland Islands) and inferred about glacial dynamics. The orthophoto and digital elevation model allowed for geomorphological mapping of glacial forelands, including (i) glacial depositional landforms, (ii) fluvial and fluvioglacial landforms, (iii) littoral and lacustrine landforms, (iv) bodies of water, and (v) other. The largest area is occupied by ground moraine and glacial lagoons on EGF and BGF. The most profound features of EGF are the large latero-frontal moraine ridges from Little Ice Age and the first half of the 20th century. Large areas of ground moraine, frequently fluted and marked with large recessional moraine ridges, dominate on SGF. A significant percentage of bedrock outcrops and end moraine complexes characterize BGF. The landform assemblages are typical for discontinuous fast ice flow of tidewater glaciers over a deformable bed. It is inferred that ice flow velocity decreased as a result of recession from the sea coast, resulting in a significant decrease in the length of ice cliffs and decrease in calving rate. Image acquisition during the fixed-wing UAV BVLOS operation proved to be a very robust technique in harsh polar conditions of King George Island.
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Alvarez-Solas, J., A. Robinson, and C. Ritz. "Brief Communication: Can recent ice discharges following the Larsen-B ice-shelf collapse be used to infer the driving mechanisms of millennial-scale variations of the Laurentide ice sheet?" Cryosphere Discussions 5, no. 6 (November 11, 2011): 3113–27. http://dx.doi.org/10.5194/tcd-5-3113-2011.
Full textAbstract:
Abstract. The effects of an ice-shelf collapse on inland glacier dynamics have recently been widely studied, especially since the breakup of Antarctic Peninsula's Larsen-B ice shelf in 2002. Several studies have documented acceleration of the ice streams that were flowing into the former ice shelf. The mechanism responsible for such a speed-up lies with the removal of the ice-shelf backforce. Independently, it is also well documented that during the last glacial period, the Northern Hemisphere ice sheets experienced large discharges into the ocean, likely reflecting ice flow acceleration episodes on the millennial time scale. The classic interpretation of the latter is based on the existence of an internal thermo-mechanical feedback with the potential to generate oscillatory behavior in the ice sheets. Here we would like to widen the debate by considering that Larsen-B-like glacial analog episodes could have contributed significantly to the registered millennial-scale variablity.
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Bhatia, Maya P., Sarah B. Das, Elizabeth B. Kujawinski, Paul Henderson, Andrea Burke, and Matthew A. Charette. "Seasonal evolution of water contributions to discharge from a Greenland outlet glacier: insight from a new isotope-mixing model." Journal of Glaciology 57, no. 205 (2011): 929–41. http://dx.doi.org/10.3189/002214311798043861.
Full textAbstract:
AbstractThe Greenland ice sheet (GrIS) subglacial hydrological system may undergo a seasonal evolution, with significant geophysical and biogeochemical implications. We present results from a new isotope-mixing model to quantify the relative contributions of surface snow, glacial ice and delayed flow to the bulk meltwater discharge from a small (∼5 km2) land-terminating GrIS outlet glacier during melt onset (May) and at peak melt (July). We use radioactive (222Rn) and stable isotopes (18O, deuterium) to differentiate the water source contributions. Atmospherically derived 7Be further constrains meltwater transit time from the glacier surface to the ice margin. We show that (1) 222Rn is a promising tracer for glacial waters stored at the bed and (2) a quantitative chemical mixing model can be constructed by combining 222Rn and the stable water isotopes. Applying this model to the bulk subglacial outflow from our study area, we find a constant delayed-flow (stored) component from melt onset through peak melt. This component is diluted first by snowmelt and then by increasing glacial ice melt as the season progresses. Results from this pilot study are consistent with the hypothesis that subglacial drainage beneath land-terminating sections of the GrIS undergoes a seasonal evolution from a distributed to a channelized system.
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Lindstrom, D. R. "Formation of the West Antarctic Ice Sheet." Annals of Glaciology 11 (1988): 71–76. http://dx.doi.org/10.3189/s0260305500006352.
Full textAbstract:
A numerical ice-shelf model is employed to observe the inception of the West Antarctic ice sheet (WAIS) from a thin (20 m thick) floating ice cover under the following conditions: (i) a lower sea-level than at present, due to ice-sheet formation in the Northern Hemisphere, (ii) surface and basal temperature and accumulation rates approximately equal to those of present Antarctic ice shelves, and (iii) ice flow from East Antarctica into West Antarctica is neglected. The model determines the flow and thickness of floating ice and assumes that grounded ice is stagnant. Under these constraints, all regions except the Ross Sea, the Filchner region (east of Berkner Island), and up-stream of Thwaites Glacier ground within 4000 years. Ice readily grounds in the Ronne region (west of Berkner Island), forcing ice from Ellsworth Land to flow east toward the Filchner region. It is suggested that grounding over the Ross Sea, the Filchner region, and up-stream of Thwaites Glacier occurs only after grounded-ice flow is established. Grounded-ice flow is also a prerequisite of bed erosion and sediment deposition, which leave historical records of the actual ice-sheet formation. It is suggested that erosion and sediment deposition is minimal over the Ronne region and considerable along the path from Ellsworth Land to the Filchner region, because more ice flows toward the Filchner region than the Ronne region. It is probably difficult for ice to ground over the Ross region, so this region should have a high proportion of glacial marine sediments.
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Lindstrom, D. R. "Formation of the West Antarctic Ice Sheet." Annals of Glaciology 11 (1988): 71–76. http://dx.doi.org/10.1017/s0260305500006352.
Full textAbstract:
A numerical ice-shelf model is employed to observe the inception of the West Antarctic ice sheet (WAIS) from a thin (20 m thick) floating ice cover under the following conditions: (i) a lower sea-level than at present, due to ice-sheet formation in the Northern Hemisphere, (ii) surface and basal temperature and accumulation rates approximately equal to those of present Antarctic ice shelves, and (iii) ice flow from East Antarctica into West Antarctica is neglected. The model determines the flow and thickness of floating ice and assumes that grounded ice is stagnant. Under these constraints, all regions except the Ross Sea, the Filchner region (east of Berkner Island), and up-stream of Thwaites Glacier ground within 4000 years. Ice readily grounds in the Ronne region (west of Berkner Island), forcing ice from Ellsworth Land to flow east toward the Filchner region. It is suggested that grounding over the Ross Sea, the Filchner region, and up-stream of Thwaites Glacier occurs only after grounded-ice flow is established. Grounded-ice flow is also a prerequisite of bed erosion and sediment deposition, which leave historical records of the actual ice-sheet formation. It is suggested that erosion and sediment deposition is minimal over the Ronne region and considerable along the path from Ellsworth Land to the Filchner region, because more ice flows toward the Filchner region than the Ronne region. It is probably difficult for ice to ground over the Ross region, so this region should have a high proportion of glacial marine sediments.
40
Alvarez-Solas, J., A. Robinson, and C. Ritz. "Brief communication "Can recent ice discharges following the Larsen-B ice-shelf collapse be used to infer the driving mechanisms of millennial-scale variations of the Laurentide ice sheet?"." Cryosphere 6, no. 3 (June 27, 2012): 687–93. http://dx.doi.org/10.5194/tc-6-687-2012.
Full textAbstract:
Abstract. The effects of an ice-shelf collapse on inland glacier dynamics have recently been widely studied, especially since the breakup of the Antarctic Peninsula's Larsen-B ice shelf in 2002. Several studies have documented acceleration of the ice streams that were flowing into the former ice shelf. The mechanism responsible for such a speed-up lies with the removal of the ice-shelf backforce. Independently, it is also well documented that during the last glacial period, the Northern Hemisphere ice sheets experienced large discharges into the ocean, likely reflecting ice flow acceleration episodes on the millennial time scale. The classic interpretation of the latter is based on the existence of an internal thermo-mechanical feedback with the potential to generate oscillatory behavior in the ice sheets. Here we would like to widen the debate by considering that Larsen-B-like glacial analog episodes could have contributed significantly to the registered millennial-scale variablity.
41
Holschuh, Nicholas, Knut Christianson, Howard Conway, Robert W. Jacobel, and Brian C. Welch. "Persistent tracers of historic ice flow in glacial stratigraphy near Kamb Ice Stream, West Antarctica." Cryosphere 12, no. 9 (September 4, 2018): 2821–29. http://dx.doi.org/10.5194/tc-12-2821-2018.
Full textAbstract:
Abstract. Variations in properties controlling ice flow (e.g., topography, accumulation rate, basal friction) are recorded by structures in glacial stratigraphy. When anomalies that disturb the stratigraphy are fixed in space, the structures they produce advect away from the source and can be used to trace flow pathways and reconstruct ice-flow patterns of the past. Here we provide an example of one of these persistent tracers: a prominent unconformity in the glacial layering that originates at Mt. Resnik, part of a subglacial volcanic complex near Kamb Ice Stream in central West Antarctica. The unconformity records a change in the regional thinning behavior seemingly coincident (∼3440±117 a) with stabilization of grounding-line retreat in the Ross Sea Embayment. We argue that this feature records both the flow and thinning history far upstream of the Ross Sea grounding line, indicating a limited influence of observed ice-stream stagnation cycles on large-scale ice-sheet routing over the last ∼ 5700 years.
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Dawes, P. R. "Glacial erratics on the Arctic Ocean margin of North Greenland: implications for an extensive ice-shelf." Bulletin of the Geological Society of Denmark 35 (October 29, 1986): 59–69. http://dx.doi.org/10.37570/bgsd-1986-35-07.
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Glacial erratics of high-grade metamorphic and plutonic rocks occur on the northern coast of Peary Land on the edge of the Arctic Ocean. Crystalline terrain is not exposed in Peary Land; sample sites are 250 km distant from the present-day Inland Ice which covers the nearest potential source - the Greenland shield. The dominant till clasts are locally derived from a northern ice-cap that coalesced during the late Wiscon- sinian glacial maximum with the Inland Ice at about 82°30'N. Recent Quaternary mapping by the Geological Survey of Greenland failed to locate crystalline erratics in northernmost Peary Land; consequently prominence is given to early observations. The present paper describes a collection of erratics made in 1969. Conveyance mechanisms, viz. ice-cap regime (glacier or ice-shelf) contra drifting ice (icebergs or sea ice) are discussed and possible transportation paths are summarised. Based on rock type and mineralogy, the Greenland shield is the most likely source of the erratics and derivation from an expansion of the Inland Ice around eastern Peary Land the most logical glacial model. However, such a provenance contravenes with the presently available on-shore data which indicate an eastwards Weichselian ice flow along the coast. Instead of invoking a rather complicated glacial history for Peary Land, involving different land ice regimes, an alternative glacial model based on an extensive Greenland - Ellesmere Island ice-shelf is outlined.
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Li, Jia, Yunyang Gu, Lixin Wu, Lei Guo, Haodong Xu, and Zelang Miao. "Changes in Glaciers and Glacial Lakes in the Bosula Mountain Range, Southeast Tibet, over the past Two Decades." Remote Sensing 14, no. 15 (August 6, 2022): 3792. http://dx.doi.org/10.3390/rs14153792.
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Glaciers and glacial lakes in the Bosula Mountain Range need special attention, because their instability may cause disastrous consequences to the downstream settlements and the Sichuan-Tibet Road. The latter is a pivotal traffic line in the Southeast Tibetan Plateau. In order to investigate the state of glaciers and glacial lakes in the Bosula Mountain Range, we estimated the changes in glacier/glacial lake boundaries, glacier surface elevation, and glacier flow velocity between 2000 and 2021 based on multisource remote sensing data. Our results showed that, from the period 2000–2013 to the period 2013–2021, the average shrinking rate of glacier area increased from 0.99 km2/a to 1.74 km2/a, and the average expanding rate of glacial lake area increased from 0.04 km2/a to 0.06 km2/a. From the period 1990–2011 to the period 2015–2019, the average thinning rate of glaciers increased from 0.83 m/a to 1.58 m/a. These results indicate the Bosula Mountain Range is one of the fastest melting glacierized regions in the High Mountain Asia, and the factors that account for this may include quick temperature rise, abundant summer rainfall, and thin debris cover. In spite of strong ice melting, the observed changes in glacier boundaries, surface elevation, and flow velocity show no sign of surge activity, and the frequency of glacier lake outburst has not increased since 1989. Currently, three proglacial lakes that expanded quickly during 2000–2021 are now prominent hazards. They are directly threatened by accidental ice calving and ice avalanche, and their outburst could cause considerable damage to the downstream settlements and the Sichuan-Tibet Road.
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Webb, Nathan D., David A. Grimley, Andrew C. Phillips, and Bruce W. Fouke. "Origin of glacial ridges (OIS 6) in the Kaskaskia Sublobe, southwestern Illinois, USA." Quaternary Research 78, no. 2 (July 20, 2012): 341–52. http://dx.doi.org/10.1016/j.yqres.2012.06.005.
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AbstractThe origin of Illinois Episode (OIS 6) glacial ridges (formerly: ‘Ridged Drift’) in the Kaskaskia Basin of southwestern Illinois is controversial despite a century of research. Two studied ridges, containing mostly fluvial sand (OSL ages: ~ 150 ± 19 ka), with associated debris flows and high-angle reverse faults, are interpreted as ice-walled channels. A third studied ridge, containing mostly fine-grained till, is arcuate and morainal. The spatial arrangement of various ridge types can be explained by a glacial sublobe in the Kaskaskia Basin, with mainly fine-grained ridges along the sublobe margins and coarse-grained glaciofluvial ridges in a paleodrainage network within the sublobe interior. Illinois Episode till fabric and striation data demonstrate southwesterly ice flow that may diverge near the sublobe terminus. The sublobe likely formed as glacial ice thinned and receded from its maximum extent. The Kaskaskia Basin contains some of the best-preserved Illinois Episode constructional glacial landforms in the North American midcontinent. Such distinctive features probably result from ice flow and sedimentation into this former lowland, in addition to minimal postglacial erosion. Other similar OIS 6 glacial landforms may exist in association with previously unrecognized sublobes in the midcontinent, where paleo-lowlands might also have focused glacial sedimentation.
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Huh, Kyung, Michel Baraër, Bryan Mark, and Yushin Ahn. "Evaluating Glacier Volume Changes since the Little Ice Age Maximum and Consequences for Stream Flow by Integrating Models of Glacier Flow and Hydrology in the Cordillera Blanca, Peruvian Andes." Water 10, no. 12 (November 26, 2018): 1732. http://dx.doi.org/10.3390/w10121732.
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Evaluating the historical contribution of the volume loss of ice to stream flow based on reconstructed volume changes through the Little Ice Age (LIA) can be directly related to the understanding of glacier-hydrology in the current epoch of rapid glacier loss that has disquieting implications for a water resource in the Cordillera Blanca in the Peruvian Andes. However, the accurate prediction of the future glacial meltwater availability for the developing regional Andean society needs more extensive quantitative estimation from long-term glacial meltwater of reconstructed glacial volume. Modeling the LIA paleoglaciers through the mid-19th century (with the most extensive recent period of mountain glacier expansion having occurred around 1850 AD) in different catchments of the Cordillera Blanca allows us to reconstruct glacier volume and its change from likely combinations of climatic control variables and time. We computed the rate and magnitude of centennial-scale glacier volume changes for glacier surfaces between the LIA and the modern era, as defined by 2011 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model Version 2 (GDEM V2) and 2008 Light Detection and Range (LiDAR) data. The model simulation showed good agreement with the observed geomorphic data and the volume and surface area (V-S) scaling remained within the 25% error range in the reconstructed simulation. Also, we employed a recently demonstrated approach (Baraër, M. et al.) to calculate meltwater contribution to glacierized catchment runoff. The results revealed multiple peaks of both mean annual and dry season discharge that have never been shown in previous research on the same mountain range.
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Knight, Jasper. "Glacial sedimentary evidence supporting stick-slip basal ice flow." Quaternary Science Reviews 21, no. 8-9 (April 2002): 975–83. http://dx.doi.org/10.1016/s0277-3791(01)00050-6.
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Marshall, Shawn J., Lev Tarasov, Garry K. C. Clarke, and W. Richard Peltier. "Glaciological reconstruction of the Laurentide Ice Sheet: physical processes and modelling challenges." Canadian Journal of Earth Sciences 37, no. 5 (May 1, 2000): 769–93. http://dx.doi.org/10.1139/e99-113.
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Current understanding of Pleistocene ice-sheet history is based on collective inferences from three separate avenues of study: (1) the geologic and paleoceanographic records, (2) the isostatic record, and (3) the behaviour of contemporary glaciers and ice sheets. The geologic record provides good constraint on the areal extent of former ice sheets, while isostatic deflection patterns provide important information about late-glacial ice-sheet thickness. The picture emerging from geologic and isostatic deductions is suggestive of a thin and mobile Laurentide Ice Sheet relative to present-day Greenland and Antarctica. We model Laurentide Ice Sheet evolution through a glacial cycle to explore the glaciological mechanisms that are required to replicate the geologic and isostatic evidence. A number of glaciological processes important to the ice-sheet evolution are not fully understood, including marine-based ice dynamics, iceberg calving, rheologic properties of ice, and basal flow dynamics. We present a spectrum of glacial cycle simulations with different treatments of poorly constrained physical processes. We conclude that glaciological model reconstructions can only be reconciled with the late-glacial geologic record of a thin, low-sloping Laurentide Ice Sheet by invoking (1) extremely deformable ice, (2) widespread basal flow, or (3) paleoclimate-ice-sheet fluctuations which give last glacial maximum ice sheets that are far from equilibrium.
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Kleman, Johan, Clas Hättestrand, Ingmar Borgström, and Arjen Stroeven. "Fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model." Journal of Glaciology 43, no. 144 (1997): 283–99. http://dx.doi.org/10.3189/s0022143000003233.
Full textAbstract:
AbstractThe evolution of ice-sheet configuration and flow pattern in Fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model, i.e. a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets. The model uses mapped flow traces and deglacial melt-water landforms, as well as relative chronologies derived from cross-cutting striae and till lineations, as input data. Flow-trace systems were classified into four types: (i) time-transgressive wet-bed deglacial fans, (ii) time-transgressive frozen-bed deglacial fans, (iii) surge fans, and (iv) synchronous non-deglacial (event) fans. Using relative chronologies and aggregation of fans into glaciologically plausible patterns, a series of ice-sheet Configurations at different time slices was erected. A chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume. Geological evidence exists for several discrete ice-sheet configurations centred over the Scandinavian mountain range during the early Weichselian. The build-up of the main Weichselian Fennoscandian ice sheet started at approximately 70 Ka, and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern Norway. This configuration had a flow pattern which is poorly reproduced by current numerical models of the Fennoscandian ice sheet. At the Last Glacial Maximum the main ice divide was located overthe Gulf of Bothnia. A major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the Scandinavian mountain chain. Widespread areas of preserved pre-late-Weichselian landscapes indicate that the ice sheet had a frozen-bed core area, which was only partly diminished in size by inward-transgressive wet-bed zones during the decay phase.
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Kleman, Johan, Clas Hättestrand, Ingmar Borgström, and Arjen Stroeven. "Fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model." Journal of Glaciology 43, no. 144 (1997): 283–99. http://dx.doi.org/10.1017/s0022143000003233.
Full textAbstract:
AbstractThe evolution of ice-sheet configuration and flow pattern in Fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model, i.e. a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets. The model uses mapped flow traces and deglacial melt-water landforms, as well as relative chronologies derived from cross-cutting striae and till lineations, as input data. Flow-trace systems were classified into four types: (i) time-transgressive wet-bed deglacial fans, (ii) time-transgressive frozen-bed deglacial fans, (iii) surge fans, and (iv) synchronous non-deglacial (event) fans. Using relative chronologies and aggregation of fans into glaciologically plausible patterns, a series of ice-sheet Configurations at different time slices was erected. A chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume. Geological evidence exists for several discrete ice-sheet configurations centred over the Scandinavian mountain range during the early Weichselian. The build-up of the main Weichselian Fennoscandian ice sheet started at approximately 70 Ka, and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern Norway. This configuration had a flow pattern which is poorly reproduced by current numerical models of the Fennoscandian ice sheet. At the Last Glacial Maximum the main ice divide was located overthe Gulf of Bothnia. A major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the Scandinavian mountain chain. Widespread areas of preserved pre-late-Weichselian landscapes indicate that the ice sheet had a frozen-bed core area, which was only partly diminished in size by inward-transgressive wet-bed zones during the decay phase.
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Kellogg, Thomas B., Terry Hughes, and Davida E. Kellogg. "Late Pleistocene interactions of East and West Antarctic Ice-flow Regimes: evidence from the McMurdo Ice Shelf." Journal of Glaciology 42, no. 142 (1996): 486–500. http://dx.doi.org/10.3189/s0022143000003476.
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AbstractWe present new interpretations of deglaciation in McMurdo Sound and the western Ross Sea, with observationally based reconstructions of interactions between East and West Antarctic ice at the last glacial maximum (LGM), 16000, 12000, 8000 and 4000 BP. At the LGM, East Antarctic ice from Mulock Glacier split; one branch turned westward south of Ross Island but the other branch rounded Ross Island before flowing southwest into McMurdo Sound. This flow regime, constrained by an ice saddle north of Ross Island, is consistent with the reconstruction of Stuiver and others (1981a). After the LGM, grounding-line retreat was most rapid in areas with greatest water depth, especially along the Victoria Land coast. By 12000 BP, the ice-now regime in McMurdo Sound changed to through-flowing Mulock Glacier ice, with lesser contributions from Koettlitz, Blue and Ferrar Glaciers, because the former ice saddle north of Ross Island was replaced by a dome. The modern flew regime was established ∼4000 BP. Ice derived from high elevations on the Polar Plateau but now stranded on the McMurdo Ice Shelf, and the pattern of the Transantarctic Mountains erratics support our reconstructions of Mulock Glacier ice rounding Minna Bluff but with all ice from Skelton Glacier ablating south of the bluff. They are inconsistent with Drewry’s (1979) LGM reconstruction that includes Skelton Glacier ice in the McMurdo-Sound through-flow. Drewry’s (1979) model closely approximates our results for 12000-4000 BP. Ice-sheet modeling holds promise for determining whether deglaciation proceeded by grounding-line retreat of an ice sheet that was largely stagnant, because it never approached equilibrium flowline profiles after the Ross Ice Shelf grounded, or of a dynamic ice sheet with flowline profiles kept low by active ice streams that extended northward from present-day outlet glaciers after the Ross Ice Shelf grounded.