Limit Of Glaciation Research Articles

Trimline Trauma: The Wider Implications of a Paradigm Shift in Recognising and Interpreting Glacial Limits

ABSTRACTTrimlines mark the boundary between glacially eroded landscapes on low ground and landscapes dominated by evidence of periglacial weathering on higher summits. For many years the trimlines of Scandinavia, Britain and Ireland have been interpreted as marking the surface of the ice sheets at the maximum of the last glaciation, but recent cosmogenic exposure dating of erratics far above the trimlines in NW Scotland shows this to be false. The trimlines in that area must represent an englacial thermal boundary between warm (eroding) ice and cold (protecting) ice. It is now clear that even very experienced geomorphologists cannot necessarily tell the difference between terrain that has been recently glaciated and terrain that has not, because cold-based ice can leave virtually no trace. This calls into question not only the interpretation of high-level trimlines elsewhere, but also the mapping of the lateral limits of past glaciations, which are often based on similar or even weaker geomorphological and sedimentological evidence.

Landscapes at the Periphery of Glacierization – Retrospect and Prospect

This paper reviews the evolution of palaeoglaciological reconstructions in regions at the periphery of glacierization, where an improved understanding of the role of glacial thermal regime has helped refine the delimitation of ice sheet maxima. Also significant has been the recognition in numerical models that some areas, especially ice sheet marginal zones, are subject to short periods of ice occupancy and hence that glacial landsystem signatures can be extremely subtle. This is compounded wherever cold-based conditions dominate during early stages of ice sheet recession, giving rise to a landform imprint typical of peripheral regions and hence often misinterpreted as unglaciated or glaciated only by older glaciations. Subtle landform imprints include meltwater channels, thin glacigenic veneers or scattered erratics and modified tors. More substantial glacigenic landform-sediment assemblages (‘drift belts’) do not always represent ice sheet maxima but instead may record significant changes in thermal regime, possibly linked to periods of ice-marginal stabilization. Some upland areas that lie beyond the traditionally demarcated limits of glaciation (e.g. Dartmoor in SW England) may contain subtle evidence of satellite ice cap development which has been overlooked due to the strong periglacial landform signature.

The North American Cordillera—An Impediment to Growing the Continent-Wide Laurentide Ice Sheet

Abstract This study examines the evolution of a continental-scale ice sheet on a triangular representation of North America, with and without the influence of the Cordilleran region. Simulations are conducted using a comprehensive atmospheric general circulation model asynchronously coupled to a three-dimensional thermomechanical ice-sheet model. The atmospheric state is updated for every 2 × 106 km3 increase in ice volume, and the coupled model is integrated to steady state. In the first experiment a flat continent with no background topography is used. The ice sheet evolves fairly zonally symmetric, and the equilibrium state is continent-wide and has the highest point in the center of the continent. This equilibrium ice sheet forces an anticyclonic circulation that results in relatively warmer (cooler) summer surface temperatures in the northwest (southeast), owing to warm (cold) air advection and radiative heating due to reduced cloudiness. The second experiment includes a simplified representation of the Cordilleran region. The ice sheet’s equilibrium state is here structurally different from the flat continent case; the center of mass is strongly shifted to the east and the interior of the continent remains ice free—an outline broadly resembling the geologically determined ice margin in Marine Isotope Stage 4. The limited glaciation in the continental interior is the result of warm summer surface temperatures primarily due to stationary waves and radiative feedbacks.

The imprint of time on Canadian soil landscapes

The imprint of time on Canadian soil landscapes reflects the strong influence of repeated Quaternary glaciations, with most soils having formed on Late Pleistocene glacial sediments, and to a lesser extent, Holocene non-glacial sediments. Soil chronosequences in these youthful landscapes seldom span the full Holocene, and have been documented principally in areas of coastal isostatic uplift and shoreline evolution, as well as on recessional moraine sequences in the Cordillera. These chronosequences have placed quantitative constraints on rates of podzolization in environments ranging from coastal temperate rainforest to subarctic. Longer sequences, involving soils and relict paleosols on Pleistocene morainal and glaciofluvial surfaces in the central Yukon Territory, record more complex legacies of pedogenesis and landscape evolution, but with much coarser time control and many potentially confounding influences of climatic change and disturbance processes. Older weathered bedrock and regolith can make significant contributions to soil parent materials in several settings: (1) in favoured locations where local conditions protected these materials from glacial erosion in southern Canada, (2) beyond the maximum limits of glaciation, principally in northwestern Canada, and (3) in the Arctic, where cold-based, non-erosive ice allowed preservation of these materials. Closer collaborations between pedologists and other Quaternary scientists will be needed to ensure a more complete understanding of these complex pedogenic legacies in Canadian landscapes.

The Quaternary of the River Trent: critical evidence for glaciation, river development and land uplift within and close to the limits of lowland glaciation in north Midland England

This Context Paper examines the findings of the Trent Valley Palaeolithic Project (TVPP) which have been published over the period 2010–2015 as a substantial book and a number of research and review papers. The findings of this project are significant for: (i) the glacial history of lowland England, with a case being made for a MIS 8 glaciation; (ii) understanding the history of the drainage of the region with identification of change from the pre-glacial Ancaster and Bytham rivers to the newly formed River Trent, which developed across the landscape glaciated during MIS 12 and (iii) presenting a case for the importance of ice-, water- and rock-loading and unloading upon the development of river systems over late Middle and Late Quaternary time. These three topics are placed in a wider context with respect to regional patterns of glacial and Quaternary history of Britain and northern Europe and some concepts underpinning the subjects.

LATE PLEISTOCENE LANDSCAPE CHANGES IN THE SAN-PABLO VALLEY (TEOTIUAKAN, MEXICO)

The landscape evolution of the San-Pablo river valley near the Serro-Gordo volcano during the end of the late glaciation is described. Stages in the development of landforms, soils, and catenae were distinguished. In the landscape evolution different rhythms and trends can be seen. Climatic changes - trend from warm OIS 3 to maximum of glaciation (LGM) and late glaciation (LGT) - OIS 2, and to new interglacial (Holocene) OIS 1 - played a leading role in the landscape formation. During this time aridization took place. At the limit of glaciation and interglacial time the tracers of disastrous water flow were found. It guttered down from the slopes of the Serro- Gordo to the San-Pablo river valley.

Improved Schmidt-hammer exposure ages for active and relict pronival ramparts in southern Norway, and their palaeoenvironmental implications

Eight pronival (protalus) ramparts from alpine southern Norway were dated using Schmidt-hammer exposure-age dating (SHD) based on local high-precision linear calibration equations. SHD ages were −1355±1240 to 815±1000years for three active ramparts and 8730±1050 to 14,635±1060years for five relict ramparts. Different parts of the same rampart yielded ages that were in generally good agreement. R-value frequency distributions enabled the identification single-age and mixed-age boulder populations, and the differentiation of active and relict rampart surfaces. The relict ramparts are located outside Younger Dryas glacier limits and probably formed over a period of ~6000years between deglaciation (following the Last Glacial Maximum of the late Weichselian, ~18,000years ago) and the end of the Younger Dryas (~11,700years ago). At that time, glacial debuttressing and permafrost degradation apparently enhanced the release of rock debris from rock faces to the ramparts. The active ramparts, which are located in areas deglaciated after the Younger Dryas, are relatively uncommon in the study area due to diminished paraglacial effects and limited debris supply associated with seasonally frozen ground during the Holocene. Thus, the legacy of glaciers, glacier–permafrost interaction, and the specific type of periglacial environment must all be considered when assessing the palaeoenvironmental and palaeoclimatic significance of pronival ramparts.

Contrasting population‐level responses to Pleistocene climatic oscillations in an alpine bat revealed by complete mitochondrial genomes and evolutionary history inference

AbstractAimWe used an integrative approach to reconstruct the evolutionary history of the alpine long‐eared bat, Plecotus macrobullaris, to test whether the variable effects of Pleistocene climatic oscillations across geographical regions led to contrasting population‐level demographic histories within a single species.LocationThe Western Palaearctic.MethodsWe sequenced the complete mitochondrial genomes of 57 individuals from across the distribution of the species. The analysis integrated ecological niche modelling (ENM), approximate Bayesian computation (ABC), measures of genetic diversity and Bayesian phylogenetic methods.ResultsWe identified two deep lineages: a western lineage, restricted to the Pyrenees and the Alps, and an eastern lineage, which expanded across the mountain ranges east of the Dinarides (Croatia). ENM projections of past conditions predicted that climatic suitability was reduced during cold stages in the areas inhabited by the western lineage, while the opposite trend was observed in the mountains inhabited by the eastern lineage. The palaeodemographic scenario that best fitted our data is consistent with the western lineage population size having shrunk repeatedly because of the extensive glaciation events that occurred in the Alps and Pyrenees during the Pleistocene. In contrast, the eastern lineage maintained a constant population size as is consistent with more limited glaciation in the mountains of south‐eastern Europe and the Middle East.Main conclusionsThis study shows that the demographic response of populations to Pleistocene climatic oscillations depended on their geographical location, offering an example of population‐level variations in the effects and long‐term consequences of climate change.

Avalanche feeding of the Djankuat Glacier

In order to evaluate the contribution of snow avalanches, coming from outside the glacier limits, into the seasonal accumulation, an original algorithm is proposed for glaciers with ongoing terrestrial mass balance programme. It was tested on the Djankuat Glacier, Caucasus. A case study was realized for 1998/99 balance year when accumulation value was the closest to its long-term mean over the 46-year-long monitoring period. Snow avalanche feeding turned out to be only 2.8 per cent of total accumulation that is about an order of magnitude smaller than assumed hitherto.

Modern changes of the high-mountain landscapes and glaciation in Southern Siberia (Russia) by the example of the Eastern Sayan mountains

The period of observations of glaciation of the Munku-Sardyk mountain massif in Siberia is one of the longest, i.e. 155 years. However, the data obtained are scattered and not systematic. The paper presents an integrated analysis of the materials collected since the first description by the explorer of Siberian mountains G.I. Radde Istoriy (1896) and extended by Peretolchin (1908) and Komarov (1953), as well as by glaciologists Maksimov (1965), Arefiev and Mukhametov (1996). The authors considered the current state of the glaciers and interaction of natural geosystems of the massif taking into account the nival-glacial processes. Since the beginning of the current millennium, regular observations have been conducted on the Munku-Sardyk massif by the V.B. Sochava Institute of Geography SB RAS, Limnological Institute SB RAS, and East-Siberian State Academy of Education. The studies revealed the leading landscape-forming factors and examined the landscape structure of the surroundings of the contemporary nival-glacial geosystems with due regard for the manifestations of altitudinal zonation. A medium-scale landscape-typological mapping was carried out. Presented are the quantitative parameters of the dynamics of the nival-glacial geosystems obtained on the basis of modern remote sensing instruments, GPS measurements and surface laser scanning using GIS analysis. The stump and stem of larch detected in the valley of the Bugovek River 300 m above the contemporary upper forest limit and 1330 m up the valley show that most likely there was no glaciation during the Atlantic period (7000–7300 years ago). The modern glacier complex has formed only during the last 4000–5000 years. The trend of shrinkage of glaciers since the end of the Little Ice Age can be traced, especially in recent years. The length and area of the open part of the glaciers have decreased by half (from 0.68 to 0.34 km2). The presence of small forms of glaciation on the southernmost limit of the Siberian glaciation 1500 m below the theoretical (climate) boundary suggests that this area can be considered a unique key site to identify trends in development of the mountain and nival-glacial geosystems, and provides an opportunity to built reconstructive and predictive models of development of mountain landscapes under the conditions of ever-increasing anthropogenic influence.

Clustering of Large Bedrock Landslides and Recurrent Slope Failure: Implications for Land Seismic Hazard Assessment of the Tien Shan - Djungaria Region

Spatial distribution of bedrock landslides in the Tien Shan - Djungaria mountain system is analyzed based on an inventory including more than 700 features, most of which are prehistoric and exceed 10 6 m 3 in volume. They often concentrate within limited areas several tens of kilometres in size, forming clusters divided by areas without or with very rare same-size slope failures. Two main types of landslide clusters are exemplified by case studies from the Chinese and Kazakh parts of this mountain system: those that have one giant feature surrounded by numerous much smaller landslides and those that include several more or less same-size features. Though no data about ages of slope failures that formed these clusters are available, in some cases simultaneity of their formation can be assumed with reasonable confidence. Besides, evidence of recurrent slope failure within these areas is presented. Considering arid climate of the region and limited glaciation, large earthquakes are the most likely trigger of such spatially and temporally localized slope failures, though additional studies are necessary to prove this assumption. In any case landslide and, likely, seismic hazard of such zones seem to be higher than that of the surrounding rockslide-free areas.

Glacial geomorphology of the Altai and Western Sayan Mountains, Central Asia

In this article, we present a map of the glacial geomorphology of the Altai and Western Sayan Mountains, covering an area of almost 600,000 km2. Although numerous studies provide evidence for restricted Pleistocene glaciations in this area, others have hypothesized the past existence of an extensive ice sheet. To provide a framework for accurate glacial reconstructions of the Altai and Western Sayan Mountains, we present a map at a scale of 1:1,000,000 based on a mapping from 30 m resolution ASTER DEM and 15 m/30 m resolution Landsat ETM+ satellite imagery. Four landform classes have been mapped: marginal moraines, glacial lineations, hummocky terrain, and glacial valleys. Our mapping reveals an abundance of glacial erosional and depositional landforms. The distribution of these glacial landforms indicates that the Altai and Western Sayan Mountains have experienced predominantly alpine-style glaciations, with some small ice caps centred on the higher mountain peaks. Large marginal moraine complexes mark glacial advances in intermontane basins. By tracing the outer limits of present-day glaciers, glacial valleys, and moraines, we estimate that the past glacier coverage have totalled to 65,000 km2 (10.9% of the mapped area), whereas present-day glacier coverage totals only 1300 km2 (0.2% of the mapped area). This demonstrates the usefulness of remote sensing techniques for mapping the glacial geomorphology in remote mountain areas and for quantifying the past glacier dimensions. The glacial geomorphological map presented here will be used for further detailed reconstructions of the paleoglaciology and paleoclimate of the region.

Limits of Midlandian glaciation in south‐eastern Ireland

The Southern Irish End Moraine (SEEM) was, for many years, an accepted feature of the geomorphological assemblage of Ireland. This is despite the lack of mapping of the 'End Moraine' over large areas. This paper presents evidence from county Kilkenny, an area that the SEEM cuts across from east to west. It attempts to trace this feature on the landscape through mapping using both field observations and a detailed digital elevation model. Where possible, it also looks at the sedimentology of the feature Charlesworth (1928) originally described. Following detailed mapping, no evidence for this feature on the landscape is found. Evidence for the reinterpretation of some of the features that formed part of the original 'SEEM' is also presented.

Variations of soil profile characteristics due to varying time spans since ice retreat in the inner Nordfjord, western Norway

Abstract. In the Erdalen and Bødalen drainage basins located in the inner Nordfjord in western Norway the soils were formed after deglaciation. The climate in the uppermost valley areas is sub-arctic oceanic, and the lithology consists of Precambrian granitic orthogneisses on which Leptosols and Regosols are the most common soils. The Little Ice Age glacier advance affected parts of the valleys with the maximum glacier extent around AD 1750. In this study five sites on moraine and colluvium materials were selected to examine main soil properties, grain size distribution, soil organic carbon and pH to assess if soil profile characteristics and patterns of fallout radionuclides (FRNs) and environmental radionuclides (ERNs) are affected by different stages of ice retreat. The Leptosols on the moraines are shallow, poorly developed and vegetated with moss and small birches. The two selected profiles show different radionuclide activities and grain size distribution. The sampled soils on the colluviums outside the LIA glacier limit became ice-free during the Preboral. The Regosols present better-developed profiles, thicker organic horizons and are fully covered by grasses. Activity of 137Cs and 210Pbex concentrate at the topsoil and decrease sharply with depth. The grain size distribution of these soils also reflects the difference in geomorphic processes that have affected the colluvium sites. Significantly lower mass activities of FRNs were found in soils on the moraines than on colluviums. Variations of ERN activities in the valleys were related to characteristics of soil mineralogical composition. These results indicate differences in soil development that are consistent with the age of ice retreat. In addition, the pattern distribution of 137Cs and 210Pbex activities differs in the soils related to the LIA glacier limits in the drainage basins.

Late Quaternary paraglacial sedimentation in the Macgillycuddy's Reeks, southwest Ireland

Talus slopes in the Curraghmore cirque basin in the Macgillycuddy's Reeks have developed since the end of the Glenavy Stadial (Last Glacial Maximum; MIS 2). The site lay outside Younger Dryas glacier limits and, as a result, thick rockfall and debris flow accumulations form a significant landform assemblage draping lower hillslopes. Rockwall retreat rates since icesheet deglaciation average 0.08mm per year, and 0.2mm per year up to the beginning of the Holocene.

Fluvial evolution of the Rhine during the last interglacial-glacial cycle in the southern North Sea basin: A review and look forward

This paper presents the current state of knowledge on the evolution and depositional history of the River Rhine in the southern part of the North Sea basin during the upper Middle and Late Pleistocene, and its response to climate change, sea-level oscillation and glacio-isostasy. The study focuses on the development of the Eemian interglacial lower-delta in the central Netherlands and its relation to records of climate and sea-level rise, and uses the Saalian and Weichselian pre- and postdating periods to place its development in context.The Rhine fluvial system fills the gradually subsiding North Sea basin, but its development has strongly been affected by the Saalian glaciation and its remaining topography. Ice-pushed ridges originating off the limit of maximum glaciation basically divided the central Netherlands into two sedimentary depocentres: a central depocentre within the former ice-limit, and a southern depocentre south of it.The sedimentary record of the central depocentre, including an incised-valley fill, shows a 20–40 m thick stacked sequence consisting of three units. The incised-valley fill consists of a Late Saalian to early Eemian age lower fluvial unit and a Weichselian age upper fluvial unit, both composed of coarse-grained channel deposits. Sandwiched in-between is a 5–15 m thick record composed of fine-grained fluvial and estuarine (tidal) floodbasin and shallow-marine deposits. It is of Eemian interglacial and Early Weichselian age, and comprises transgressive and highstand deposits that show the drowning of a fluvial system. Inland parts transformed from fluvial to deltaic and estuarine environments, and the most downstream parts transformed to a shallow-marine embayment. Preservation of these units occurred, despite considerable sea-level fall and climate-controlled erosion taking place in the last-glacial. Preservation potential was increased by the fact that the Rhine system avulsed away to the southern depocentre, halfway the Weichselian Pleniglacial. Consequently, the infill of the southern depocentre is of an entire different nature, and last-interglacial transgressive or highstand units are hardly preserved.Because of glaciation and resulting depocentre configuration, the Netherlands in NW Europe thus offers a very good opportunity to study the transgressive interglacial lower-deltaic records and falling-stage preservation thereof – both key elements for understanding sedimentary development over full 100-ky glacial-interglacial cycles of climate and base-level change.

Linking two centuries of tree growth and glacier dynamics with climate changes in Kamchatka

Glaciers around the world retreated as the climate warmed substantially. For the majority of alpine and arctic areas, however, the lack of meteorological data over a long period makes it difficult to build long-term climate and glacial fluctuation relationships, emphasizing the importance of natural proxy archives. Here we use the 230-year record of stem radial growth of birch trees (Betula ermanii) from the treeline forests above the receding glaciers in eastern maritime Kamchatka to analyse temporal variations of climate as well as glacial advance and retreat. Glaciers in Kamchatka Peninsula represent the southern limit of glaciation in far eastern Eurasia, which makes them prone to global warming. Using instrumental climate data (1930-1996) from local meteorological stations, we find that the July temperature had most prominent positive impact on birch growth. On the contrary, smaller ring increments are associated with the positive summer and net annual ice mass balance of Koryto Glacier. The prevailing trend of higher summer temperatures and lower snowfall over the past 70 years has enhanced tree growth while causing the glacier's surface to lower by about 35 m and its front to retreat by about 490 m. Assuming these same relationships between climate, tree growth, and glacier mass balance also existed in the past, we use tree rings as a proxy record of climatically induced temporary halts in the glacier's retreat over the past two centuries, which in total was over 1,000 m. Both direct observations and tree ring proxies indicate several

Natural hazards versus climate change and their potential impacts in the dry, northern Himalayas: focus on the upper Kali Gandaki (Mustang District, Nepal)

In the Himalayas, the consequences of climate change are a fairly debated issue, mainly questioning the availability of water resources to the lowland population. North of the monsoon Himalayas, a semi-arid, continental climate prevails and settlements rely economically mostly on irrigated crops, high altitude rangelands, trade and tourism. The upper Kali Gandaki (Mustang) is situated in this area, with sharp contrasts between valley bottoms (\3,000 m) and high, glaciated peaks (up to[8,000 m). The impacts of climate change may appear in different ways. Gullying is common, and might increase with greater climate variability. Increased ground instabilities (earthflows and occasional debris flows) affecting extensive shale/marly substrates are also expected, linked to changes in snow cover and seasonality. Similarly, the combination of higher snowfall and rapid melting may favour the occurrence of flash floods. The possibility of glacial outburst floods is less probable because of the present limited glaciation. Eventually, permafrost melting may induce rock avalanches down the steepest cliffs and might impact the adjacent valley floors. Collectively, these hazards will affect irrigation canals and fields, new infrastructures and the associated growing settlements. Water availability in the near future is more difficult to predict; however, any change in the amount and nature of precipitation may affect groundwater reserves, hence spring discharge and runoff, with consequences for agricultural products. Eventually, the overall potential increase in natural hazards may jeopardize the development of small markets and the good connection of these upper valleys to the main urban centres of Nepal, a country with a very low economic and social capacity to adjust.

Rock Glacier Inventory of the Valles Calchaquíes Region (~ 25°S), Salta, Argentina, Derived from ALOS Data

ABSTRACTRock glaciers near the Andean mountains of central and northwestern Argentina provide an important supply of water for agriculture, but data on their number, size, geographic distribution and altitudinal range are poorly known. Here, we provide the first detailed rock glacier inventory of the Valles Calchaquíes region of Salta, Argentina, based on 2.5 m x 2.5 m resolution Advanced Land Observing Satellite PRISM (Panchromatic Remote‐sensing Instruments for Stereo Mapping) satellite images. Rock glacier outlines were manually digitised and a total of 488 were identified, which cover a total area of c. 59 km2. The lower limits of intact and fossil rock glaciers are at c. 4300 m asl and 4100 m asl, respectively. Because rock glaciers are protected by law in Argentina, the inventory provides an important basis for political decision‐making about water resources and for further periglacial and environmental studies in this region. Copyright © 2014 John Wiley & Sons, Ltd.

Where does a glacier end? GPR measurements to identify the limits between valley slopes and actual glacier body. Application to the Austre Lovénbreen, Spitsbergen

Glacier limits are usually mapped according to a spatial discrimination based on color of remote sensing images or aerial photography. What appears like ice (white or light colored areas) at the end of the ablation period (end of summer) corresponds to the glacier, while what appears as rock (dark areas) is identified as the slope. This kind of visual discretization seems to be insufficient in the case of small arctic glaciers.Indeed, the slopes have been described as very unstable parts of glacial basins. Debris are generated by the inclination of the slopes, and reach the glacier surface. Thus, the visible limit does not correspond to the ice extension: a significant amount of ice is potentially covered by rock debris, enlarging the actual glacier surface with respect to the observed area. Hence, we apply Ground Penetrating Radar (GPR) measurements for mapping, beyond the central parts of the glacier, the steep slopes of the Austre Lovénbreen (Spitsbergen, 79° N). The aim is to assess the discrepancy between the limits extracted from remote sensing methods – aerial photography, satellite images and derived digital elevation models – and the GPR data which exhibit significant ice thickness at locations considered outside the glacier itself.The ice is observed to extend typically from 25 to 30m, and up to 100m, under the slopes. These measurements allow for a new determination of the rock/ice interface location following criteria beyond the visual and morphological characteristics seen from the surface, as obtained by remote sensing techniques or in-situ observations.