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  • 1.
    Greenwood, Sarah L.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Clason, Caroline C.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Helanow, Christian
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography. Durham University, UK.
    Theoretical, contemporary observational and palaeo-perspectives on ice sheet hydrology: Processes and products2016In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 155, p. 1-27Article in journal (Refereed)
    Abstract [en]

    Meltwater drainage through ice sheets has recently been a key focus of glaciological research due to its influence on the dynamics of ice sheets in a warming climate. However, the processes, topologies and products of ice sheet hydrology are some of the least understood components of both past and modem ice sheets. This is to some extent a result of a disconnect between the fields of theoretical, contemporary observational and palaeo-glaciology that each approach ice sheet hydrology from a different perspective and with different research objectives. With an increasing realisation of the potential of using the past to inform on the future of contemporary ice sheets, bridging the gaps in the understanding of ice sheet hydrology has become paramount. Here, we review the current state of knowledge about ice sheet hydrology from the perspectives of theoretical, observational and palaeo-glaciology. We then explore and discuss some of the key questions in understanding and interpretation between these research fields, including: 1) disagreement between the palaeo-record, glaciological theory and contemporary observations in the operational extent of channelised subglacial drainage and the topology of drainage systems; 2) uncertainty over the magnitude and frequency of drainage events associated with geomorphic activity; and 3) contrasts in scale between the three fields of research, both in a spatial and temporal context The main concluding points are that modem observations, modelling experiments and inferences from the palaeo-record indicate that drainage topologies may comprise a multiplicity of forms in an amalgam of drainage modes occurring in different contexts and at different scales. Drainage under high pressure appears to dominate at ice sheet scale and might in some cases be considered efficient; the sustainability of a particular drainage mode is governed primarily by the stability of discharge. To gain better understanding of meltwater drainage under thick ice, determining what drainage topologies are reached under high pressure conditions is of primary importance. Our review attests that the interconnectivity between research sub-disciplines in progressing the field is essential, both in interpreting the palaeo-record and in developing physical understanding of glacial hydrological processes and systems.

  • 2.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The pattern of ice marginal retreat during the last deglaciation has, thus far, most frequently been reconstructed using absolute dating methods and landform record. In reconstructions using landform record, meltwater system has most often been neglected. This is predominantly a consequence of the smaller scale of meltwater features. However, digital data with high spatial resolution yields the potential source of information that allows for the future mapping of deglacial meltwater system, which in turn can be used in reconstructions of ice marginal retreat pattern at a regional or ice sheet sector scale. Before this potential can be realized, there is a need for rigorous testing of data sources and methodological developments. Available sets of satellite images and digital elevation models (DEMs) covering areas in Scotland, Sweden and Finland were tested in order to evaluate their relevance for mapping meltwater features. This study shows that high-resolution DEMs together with medium-resolution satellite imagery are suitable for the mapping meltwater landforms such as eskers and meltwater channels. To further test the possibility of mapping traces of glacial lakes from satellite imagery, a mapping campaign was launched in the region of central Transbaikalia, Russia. The study comprised a reconstruction of glacial lakes and aimed to compile a glacial geomorphological map of this poorly studied region. The most prominent glacial lake was dammed in the catchment of the River Vitim and covered an area of about 25 000 km2. The landform record indicates that the characteristics and style of glaciation in the area were neither spatially nor temporally uniform. Based on the knowledge from the methodological study and the geomorphological mapping in Transbaikalia, meltwater features have been mapped in central British Columbia and the southern Yukon Territory, Canada. These might provide material for a reconstruction of the ice retreat pattern of the Cordilleran Ice Sheet, which has been the main objective of this PhD project.

  • 3.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Glaciers and ice sheets covered extensive areas in the Northern Hemisphere during the last glacial period. Subsequently to the Last Glacial Maximum (LGM), they retreated rapidly and, except for Greenland and some other ice caps and glaciers, they vanished after the last glacial termination. This thesis examines the dynamics of deglacial environments by analysing the glacial geomorphological record with focus on the landforms created by glacial meltwater. The aims are (i) to evaluate the data available for mapping glacial meltwater features at the regional scale, and (ii) to demonstrate the potential of such features for regional ice retreat reconstructions in high-relief landscapes. Meltwater landforms such as ice-marginal meltwater channels, eskers, deltas and fossil glacial lake shorelines are used to infer former ice surface slope directions and successive positions of retreating ice margins.

    Evaluated high-resolution satellite imagery and digital elevation models reveal their potential to replace aerial photographs as the primary data for mapping glacial meltwater landforms. Following a methods study, reconstructions of the deglacial dynamics are carried out for central Transbaikalia, Siberia, Russia, and for the Cordilleran Ice Sheet (CIS) in central British Columbia, Canada, using regional geomorphological mapping surveys.

    Mapped glacial landforms in central Transbaikalia show evidence of a significant glaciation that possibly extended beyond the high mountain areas. Large glacial lakes were formed as advancing glaciers blocked rivers, and of these, Glacial Lake Vitim was the most prominent.

    Deglacial dynamics of the CIS reveals that the ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern ice margin retreated towards the ice divide in late glacial time.

    This thesis demonstrates the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwater landform record.

  • 4.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansen, John D.
    Codilean, Alexandru T.
    Preusser, Frank
    Gurinov, Artem L.
    Fujioka, Toshiyuki
    Fink, David
    Repeated megafloods from glacial Lake Vitim, Siberia, to the Arctic Ocean over the past 60,000 years2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 187, p. 41-61Article in journal (Refereed)
    Abstract [en]

    Cataclysmic outburst floods transformed landscapes and caused abrupt climate change during the last deglaciation. Whether such events have also characterized previous deglaciations is not known. Arctic marine cores hint at megafloods prior to Oxygen Isotope Stage (OIS) 2, but the overprint of successive glaciations means that geomorphological traces of ancient floods remain scarce in Eurasia and North America. Here we present the first well-constrained terrestrial megaflood record to be linked with Arctic archives. Based on cosmogenic-nuclide exposure dating and optically stimulated luminescence dating applied to glacial-lake sediments, a 300-m deep bedrock spillway, and giant eddy-bars > 200-m high, we reconstruct a history of cataclysmic outburst floods from glacial Lake Vitim, Siberia, to the Arctic Ocean over the past 60,000-years. Three megafloods have reflected the rhythm of Eurasian glaciations, leaving traces that stretch more than 3500 km to the Lena Delta. The first flood was coincident with deglaciation from OIS-4 and the largest meltwater spike in Arctic marine-cores within the past 100,000 years (isotope-event 3.31 at 55.5 ka). The second flood marked the lead up to the local Last Glacial Maximum, and the third flood occurred during the last deglaciation. This final 3000 km(3) megaflood stands as one of the largest freshwater floods ever documented, with peak discharge of 4.0-6.5 million m(3)s(-1), mean flow depths of 120-150 m, and average flow velocities up to 21 ms(-1)

  • 5.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansen, John D.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gurinov, Artem L.
    Codilean, Alexandru T.
    Fink, David
    Preusser, Frank
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Reznichenko, Natalya V.
    Mifsud, Charles
    Extensive glaciation in Transbaikalia, Siberia, at the Last Glacial Maximum2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 132, p. 161-174Article in journal (Refereed)
    Abstract [en]

    Successively smaller glacial extents have been proposed for continental Eurasia during the stadials of the last glacial period leading up to the Last Glacial Maximum (LGM). At the same time the large mountainous region east of Lake Baikal, Transbaikalia, has remained unexplored in terms of glacial chronology despite clear geomorphological evidence of substantial past glaciations. We have applied cosmogenic Be-10 exposure dating and optically stimulated luminescence to establish the first quantitative glacial chronology for this region. Based on eighteen exposure ages from five moraine complexes, we propose that large mountain ice fields existed in the Kodar and Udokan mountains during Oxygen Isotope Stage 2, commensurate with the global LGM. These ice fields fed valley glaciers (>100 km in length) reaching down to the Chara Depression between the Kodar and Udokan mountains and to the valley of the Vitim River northwest of the Kodar Mountains. Two of the investigated moraines date to the Late Glacial, but indications of incomplete exposure among some of the sampled boulders obscure the specific details of the post-LGM glacial history. In addition to the LGM ice fields in the highest mountains of Transbaikalia, we report geomorphological evidence of a much more extensive, ice-cap type glaciation at a time that is yet to be firmly resolved.

  • 6.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Evaluation of data sources for mapping glacial meltwater features2012In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 33, no 8, p. 2355-2377Article in journal (Refereed)
    Abstract [en]

    The meltwater system of disintegrating ice sheets provides an important source of information for the reconstruction of ice-retreat patterns during deglaciation. Recent method development in glacial geomorphology, using satellite imagery and digital elevation models (DEMs) for glacial landform mapping, has predominantly been focused on the identification of lineation and other large-scale accumulation features. Landforms created by meltwater have often been neglected in these efforts. Meltwater features such as channels, deltas and fossil shorelines were traditionally mapped using stereo interpretation of aerial photographs. However, during the transition into the digital era, driven by a wish to cover large areas more economically, meltwater features were lost in most mapping surveys. We have evaluated different sets of satellite images and DEMs for their suitability to map glacial meltwater features (lateral meltwater channels, eskers, deltas, ice-dammed lake drainage channels and fossil shorelines) in comparison with the traditional mapping from aerial photographs. Several sets of satellite images and DEMs were employed to map the landform record of three reference areas, located in northwestern Scotland, northeastern Finland and western Sweden. The employed satellite imagery consisted of Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Satellite Pour l’Observation de la Terre (SPOT) 5 and Indian Remote Sensing (IRS)1C, and the DEMs used were from NEXTMap Britain, Panorama, National elevation data set of Sweden and National Land Survey of Finland. ASTER images yielded better results than the panchromatic band of Landsat 7 ETM+ in all three regions, despite the same spatial resolution of the data. In agreement with previous studies, this study shows that DEMs display accumulation features such as eskers suitably well. Satellite images are shown to be insufficiently detailed for the interpretation of smaller features such as meltwater channels. Hence, satellite imagery and DEMs of intermediate resolution contain meltwater system information only at a general level that allows for the identification of landforms of medium to large sizes. It is therefore pertinent that data with an appropriate spatial and spectral resolution are accessed to fulfil the need of a particular mapping effort. Stereointerpretation of aerial photographs continues to be an advisable method for local meltwater system reconstructions; alternatively, it can be replaced by mapping fromhigh-resolution DEMs such as NEXTMap Britain. For regional to sub-continental reconstructions, the use of ASTER satellite imagery is recommended, because it provides both spectral and spatial resolutions suitable for the identification of meltwater features on a medium to large scale.

  • 7.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glacial geomorphology and glacial lakes of central Transbaikalia, Siberia, Russia2011In: Journal of Maps, ISSN 1744-5647, p. 18-30Article in journal (Refereed)
    Abstract [en]

    A glacial geomorphological map is presented covering the poorly investigated mountainous region ofcentral Transbaikalia, Russia. Interpretation of geomorphology is achieved using remotely sensed data (SRTM digital elevation model, Landsat 7 ETM+ satellite imagery and Google Maps). Glacially modified terrain is mapped together with moraines, glacial lineations and meltwater channels, in order to provide an estimate of the area affected by glaciation. The glacial landform record varies across the mapped region implying that the character of glaciation was not uniform in the area. Several moraine generations occur in the main valleys and at some places glaciers blocked the drainage routes, which resulted in the formation of glacial lakes. The largest, Glacial Lake Vitim, was dammed by a glacier lobe blocking the Vitim valley in the Kodar Range. A distinct fossil shoreline of Glacial Lake Vitim occurs along a substantial part of the former shore at a level of 840 m a.s.l. A col through which the lake drained to the River Nercha occurs at an elevation consistent with the shoreline level of 840 m a.s.l. The existence of another glacial lake in the Chara basin is inferred from mapped delta surfaces and a probable blockage of the Chara River by advancing valley glaciers. The rich and diverse geomorphology and the sedimentary record of glacial lakes represent a potential for more detailed studies of the glacial and climate history of this remote region.

  • 8.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Towards method development in mapping meltwater features from remotely sensed and digital elevation data2008In: 28th Nordic Geological Winter Meeting: Abstract Volume, 2008Conference paper (Other academic)
    Abstract [en]

    The use of satellite data has revolutionized glacial geomorphological mapping. However, the focus has often been on mapping features such as glacial lineations and ribbed moraines, leaving the meltwater system largely unexplored. Hence, we are currently in the need to perform a methods development necessary for a full transformation from air-photo based approaches in meltwater landform mapping to a fully integrated use of satellite imagery and DTM’s in a GIS environment. We will target the method development objective by exploration of a range of diverse data with different spatial and spectral resolutions. The meltwater system is known to play a vital role in paleoglaciology in reconstructing ice marginal retreat patterns in areas previously covered by cold-based ice for basically three reasons: (1) During cold-based deglaciation, meltwater features are the only landforms formed and used for reconstructions of ice marginal retreat. (2) Meltwater features play a fundamental role in the separation of young imprints from older ice-flow events preserved in the landform record. (3) The spatial and temporal distribution of meltwater is known to have had a profound role on its environment and it is therefore important topic of study. Methods developed as part of this project will be used to perform paleoglaciological reconstructions of the deglacial environment in Glen Roy, Scotland and in northern Sweden. These areas are chosen because of their stunning landforms examples and the, at least on the local scale, particularly well-known glacial history.

  • 9.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glacial meltwater landforms of central British Columbia2011In: Journal of Maps, ISSN 1744-5647, p. 486-506Article in journal (Refereed)
    Abstract [en]

    The Cordilleran Ice Sheet (CIS), which grew and melted repeatedly across the mountain ranges of westernmost Canada during the late Cenozoic, has imprinted its legacy in the form of glacial landforms, such as meltwater landforms. However, despite their abundance, a coherent effort to map meltwater landforms has been lacking. Here, we present a first regional geomorphological map of glacial meltwater landforms of central British Columbia. Series of well-developed meltwater channels occur at higher elevations on the Interior Plateau, in marginal ranges east of the Coast Mountains, in the Skeena and Omineca mountains, and, in much lower abundances, in the Rocky Mountains. Single-ridged eskers, that in direction are consistent with the regional ice flow direction from glacial lineations, occur in elevated areas of the Interior Plateau. Multiple-ridged larger eskers and esker complexes are, on the other hand, confined to the main topographic lows. The geographical distribution of meltwater landforms is a new reliable dataset for use in palaeoglaciological reconstructions and inference of late glacial ice sheet dynamics in central British Columbia.

  • 10.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Late-glacial ice dynamics of the Cordilleran Ice Sheet in northern British Columbia and southern Yukon Territory: retreat pattern of the Liard Lobe reconstructed from the glacial landform recordManuscript (preprint) (Other academic)
    Abstract [en]

    The Liard Lobe formed a part of the northeastern sector of the Cordilleran Ice Sheet and drained ice from accumulation areas in the Selwyn, Pelly, Cassiar and Skeena mountains. This study reconstructs the ice retreat pattern of the Liard Lobe during the last deglaciation from the glacial landform record that is comprised of glacial lineations and landforms of the meltwater system such as eskers, meltwater channels, perched deltas and outwash fans. The spatial distribution of these landforms defines the successive configurations of the ice sheet during the deglaciation. The Liard Lobe retreated to the west and southwest across the Hyland Highland from its local Last Glacial Maximum position in the southeastern Mackenzie Mountains where it coalesced with the Laurentide Ice Sheet. The retreat across the Liard Lowland and a subsequent splitting of the thus far uniform ice surface into several ice lobes is evidenced by large esker complexes that stretch across the Liard Lowland cutting across the contemporary drainage network. Ice margin positions from the late stage of deglaciation are reconstructed locally at the foot of the Cassiar Mountains and farther up-valley in an eastern facing valley of the Cassiar Mountains. The presented landform record indicates that the deglaciation of the Liard Lobe was accomplished mainly by active ice retreat and that ice stagnation did not play a significant role in the deglaciation of this region.

  • 11.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Clague, John
    Simon Fraser University, Department of Earth Sciences.
    Late-glacial retreat pattern of the Cordilleran Ice Sheet in central British Columbia reconstructed from glacial meltwater landformsArticle in journal (Refereed)
    Abstract [en]

    The Cordilleran Ice Sheet (CIS) covered much of the mountainous northwestern part of North America during Pleistocene glaciations. In contrast to other ephemeral Pleistocene ice sheets, the pattern and timing of growth and decay of the CIS are poorly understood. Here, we present a reconstruction of the pattern of late-glacial ice sheet retreat in central British Columbia based on a palaeoglaciological interpretation of ice-marginal meltwater channels, eskers, and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of high-elevation ice-marginal meltwater channels (1600-2400 m a.s.l.) occurs across central British Columbia. They indicate the presence of ice domes over the Skeena Mountains and the central Coast Mountains early during deglaciation. Ice sourced in the Coast Mountains remained dominant over the southern and east-central parts of the Interior Plateau during late-glacial time. Our reconstruction shows a successive westward retreat of the ice margin away from the western foot of the Rocky Mountains, accompanied by the formation and rapid evolution of a glacial lake in the upper Fraser River basin. Final stages of deglaciation were characterized by the frontal retreat of ice lobes through the valleys of the Skeena and Omineca mountains and by the formation of large esker systems in the most prominent topographic lows of the Interior Plateau. We conclude that the CIS underwent a large-scale reconfiguration early during deglaciation and subsequently diminished by thinning and complex frontal retreat towards the Coast Mountains.

  • 12.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Clague, John J.
    Retreat pattern of the Cordilleran Ice Sheet in central British Columbia at the end of the last glaciation reconstructed from glacial meltwater landforms2013In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 42, no 4, p. 830-847Article in journal (Refereed)
    Abstract [en]

    The Cordilleran Ice Sheet (CIS) covered much of the mountainous northwestern part of North America at least several times during the Pleistocene. The pattern and timing of its growth and decay are, however, poorly understood. Here, we present a reconstruction of the pattern of ice-sheet retreat in central British Columbia at the end of the last glaciation based on a palaeoglaciological interpretation of ice-marginal meltwater channels, eskers and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of high-elevation (1600-2400m a.s.l.), ice-marginal meltwater channels is evident across central British Columbia. These landforms indicate the presence of ice domes over the Skeena Mountains and the central Coast Mountains early during deglaciation. Ice sourced in the Coast Mountains remained dominant over the southern and east-central parts of the Interior Plateau during deglaciation. Our reconstruction shows a successive westward retreat of the ice margin from the western foot of the Rocky Mountains, accompanied by the formation and rapid evolution of a glacial lake in the upper Fraser River basin. The final stage of deglaciation is characterized by the frontal retreat of ice lobes through the valleys of the Skeena and Omineca Mountains and by the formation of large esker systems in the most prominent topographic lows of the Interior Plateau. We conclude that the CIS underwent a large-scale reconfiguration early during deglaciation and was subsequently diminished by thinning and complex frontal retreat towards the Coast Mountains.

  • 13.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lateglacial ice dynamics of the Cordilleran Ice Sheet in northern British Columbia and southern Yukon Territory: retreat pattern of the Liard Lobe reconstructed from the glacial landform record2013In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 28, no 2, p. 180-188Article in journal (Refereed)
    Abstract [en]

    The Liard Lobe formed a part of the north-eastern sector of the Cordilleran Ice Sheet and drained ice from accumulation areas in the Selwyn, Pelly, Cassiar and Skeena mountains. This study reconstructs the ice retreat pattern of the Liard Lobe during the last deglaciation from the glacial landform record that comprises glacial lineations and landforms of the meltwater system such as eskers, meltwater channels, perched deltas and outwash fans. The spatial distribution of these landforms defines the successive configurations of the ice sheet during the deglaciation. The Liard Lobe retreated to the west and south-west across the Hyland Highland from its local Last Glacial Maximum position in the south-eastern Mackenzie Mountains where it coalesced with the Laurentide Ice Sheet. Retreat across the Liard Lowland is evidenced by large esker complexes that stretch across the Liard Lowland cutting across the contemporary drainage network. Ice margin positions from the late stage of deglaciation are reconstructed locally at the foot of the Cassiar Mountains and further up-valley in an eastern-facing valley of the Cassiar Mountains. The presented landform record indicates that the deglaciation of the Liard Lobe was accomplished mainly by active ice retreat and that ice stagnation played a minor role in the deglaciation of this region.

  • 14.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Krister
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stroeven, Arjen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansen, John
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glacial Lake Vitim, a 3000 km³ outburst flood from Siberia to the Arctic Ocean2011In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 76, no 3, p. 393-396Article in journal (Refereed)
    Abstract [en]

    A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500 km2 and held a volume of ~3000 km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~13 cal ka BP inferred from Arctic Ocean sediments.

  • 15.
    Margold, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Treml, Vaclav
    Petr, Libor
    Nyplova, Petra
    Snowpatch hollows and pronival ramparts in the krkonoše mountains, Czech Republic: distribution, morphology and chronology of formation2011In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 93A, no 2, p. 137-150Article in journal (Refereed)
    Abstract [en]

    Two types of landforms attributed to the geomorphological effects of long-lasting snow accumulations, snowpatch hollows and pronival ramparts, were studied in the Krkonose Mountains, Czech Republic. Factors influencing the distribution and morphology of snowpatch hollows were examined using statistical analysis of field-measured and DEM-modelled snowpatch hollow characteristics. Snowpatch hollows were classified into two groups. The first group comprises hollows developed mainly in erosional incisions from streams on low-relief summit planation surfaces. The hollows of this group are relatively small and display signs of recent activity, with development during the Holocene. The second group consists of larger snowpatch hollows developed in debris-covered slopes of the highest summits, closely related to the cryoplanation terraces occurring in the area. The hollows of this group are suggested to have developed in the periglacial environment of the glacial periods. The age and degree of activity of pronival ramparts, occurring only at two sites in the study area, were determined using several methods (Schmidt hammer, lichenometry, pollen analysis, and radiocarbon dating). The appearance of these pronival ramparts differs between the two sites as a result of the different geological setting. Both the ramparts in the Harrachova jama cirque, consisting of coarse granite debris, and the rampart in the Upska jama cirque, developed of mica-schist clasts, have been active during the late Holocene and are considered to be active even today.

  • 16. Menounos, B.
    et al.
    Goehring, B. M.
    Osborn, G.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ward, B.
    Bond, J.
    Clarke, G. K. C.
    Clague, J. J.
    Lakeman, T.
    Koch, J.
    Caffee, M. W.
    Gosse, J.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Seguinot, Julien
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Heyman, Jakob
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Gothenburg, Sweden.
    Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination2017In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, no 6364, p. 781-784Article in journal (Refereed)
    Abstract [en]

    The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bolling-Allerod warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bolling-Allerod and Younger Dryas.

  • 17. Norris, Sophie L.
    et al.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Alberta, Canada.
    Froese, Duane G.
    Glacial landforms of northwest Saskatchewan2017In: Journal of Maps, ISSN 1744-5647, E-ISSN 1744-5647, Vol. 13, no 2, p. 600-607Article in journal (Refereed)
    Abstract [en]

    A comprehensive map of glacial landforms is presented for the area of northwest Saskatchewan, Canada. Remote sensing of 1-arc (similar to 30 m resolution) Shuttle Radar Topography Mission digital elevation models over an area of approximately 15,000 km(2) were used as the primary data source for landform identification. A total of 16,856 landforms were identified pertaining to Quaternary glacial and postglacial activity. Ten landform types were mapped: ice flow parallel lineations (flutings, drumlins, mega-scale glacial lineations, and crag-and-tail ridges), moraines (major and minor), ice-thrust ridges, crevasse-fill ridges, meltwater landforms (major and minor meltwater channels and eskers), palaeo-shorelines and dunes. Collectively, these landforms constitute a glacial and postglacial landform record, which exhibits a more complex pattern than previously recognised, with evidence of multiple cross cutting ice flow directions. This geomorphological mapping of the regional landform record provides the prerequisite for future reconstructions of the glacial dynamics and chronology of northwest Saskatchewan.

  • 18.
    Seguinot, Julien
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. ETH Zürich, Switzerland; GFZ German Research Centre for Geosciences, Germany.
    Rogozhina, Irina
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Numerical simulations of the Cordilleran ice sheet through the last glacial cycle2016In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 10, no 2, p. 639-664Article in journal (Refereed)
    Abstract [en]

    After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2-56.9 ka) and 2 (23.2-16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka).

  • 19. Stokes, Chris R.
    et al.
    Tarasov, Lev
    Blomdin, Robin
    Stockholm University, Faculty of Science, Department of Physical Geography. Purdue University, USA.
    Cronin, Thomas M.
    Fisher, Timothy G.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Heyman, Jakob
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hindmarsh, Richard C. A.
    Hughes, Anna L. C.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Livingstone, Stephen J.
    Margold, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography. Durham University, UK.
    Murton, Julian B.
    Noormets, Riko
    Peltier, W. Richard
    Peteet, Dorothy M.
    Piper, David J. W.
    Preusser, Frank
    Renssen, Hans
    Roberts, David H.
    Roche, Didier M.
    Saint-Ange, Francky
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Teller, James T.
    On the reconstruction of palaeo-ice sheets: Recent advances and future challenges2015In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 125, p. 15-49Article, review/survey (Refereed)
    Abstract [en]

    Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding mechanisms of global climate change and associated sea-level fluctuations in the past, present and future. The significance of palaeo-ice sheets is further underlined by the broad range of disciplines concerned with reconstructing their behaviour, many of which have undergone a rapid expansion since the 1980s. In particular, there has been a major increase in the size and qualitative diversity of empirical data used to reconstruct and date ice sheets, and major improvements in our ability to simulate their dynamics in numerical ice sheet models. These developments have made it increasingly necessary to forge interdisciplinary links between sub-disciplines and to link numerical modelling with observations and dating of proxy records. The aim of this paper is to evaluate recent developments in the methods used to reconstruct ice sheets and outline some key challenges that remain, with an emphasis on how future work might integrate terrestrial and marine evidence together with numerical modelling. Our focus is on pan-ice sheet reconstructions of the last deglaciation, but regional case studies are used to illustrate methodological achievements, challenges and opportunities. Whilst various disciplines have made important progress in our understanding of ice-sheet dynamics, it is clear that data-model integration remains under-used, and that uncertainties remain poorly quantified in both empirically-based and numerical ice-Sheet reconstructions. The representation of past climate will continue to be the largest source of uncertainty for numerical modelling. As such, palaeo-observations are critical to constrain and validate modelling. State-of-the-art numerical models will continue to improve both in model resolution and in the breadth of inclusion of relevant processes, thereby enabling more accurate and more direct comparison with the increasing range of palaeo-observations. Thus, the capability is developing to use all relevant palaeo-records to more strongly constrain deglacial (and to a lesser extent pre-LGM) ice sheet evolution. In working towards that goal, the accurate representation of uncertainties is required for both constraint data and model outputs. Close cooperation between modelling and data-gathering communities is essential to ensure this capability is realised and continues to progress.

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