Valley Glaciers Research Articles

Forecasting of suspended sediment concentration in the Pindari-Kafni glacier valley in Central Himalayan region considering the impact of precipitation: using soft computing approach

Forecasting of suspended sediment concentration in the Pindari-Kafni glacier valley in Central Himalayan region considering the impact of precipitation: using soft computing approach

New cosmogenic nuclide constraints on Late Glacial and Holocene glacier fluctuations in the sub-Antarctic Indian Ocean (Kerguelen Islands, 49°S)

Cosmogenic nuclide dating of glacial landforms on the Kerguelen Archipelago (49°S, 69°E) gives the opportunity to study multi-millennial glacier fluctuations within the sub-Antarctic sector of the Indian Ocean. We here dated such geomorphic features to provide time constraints over the last 17,000 years using in situ-produced 36Cl in three glacial valleys: Val Travers valley, Ampere Glacier valley and Arago Glacier valley. For the first time, a combination of in situ-produced 36Cl and 10Be dating and 26Al/10Be ratios analysis was performed in the quartz-bearing syenite boulders of the Arago Glacier site. In addition, a Bayesian approach was computed to obtain a better constraint on moraine dating. Glacial advances occurred during the Late Glacial at 16.0 ± 1.9 ka and at 12.9 ± 1.7 ka in Val Travers, and at 13.6 ± 1.8 ka in Arago Glacier valley, probably linked to the Heinrich Stadial 1 and/or Antarctic Cold Reversal events, respectively. This suggests that all glaciers at this latitude were broadly sensitive to the large-scale climatic signal of the Antarctic Cold Reversal. So far, no Early nor Mid-Holocene moraines have been found in the glacial valleys on Kerguelen, indicating that the glaciers had probably receded significantly during these periods. This is in agreement with previously determined 14C ages from peat bogs, which suggest extensive deglaciation during several millennia of the Holocene period. Samples from glacially-polished bedrock surfaces (ranging from ∼4.4 ka to ∼14 ka) at Ampere Glacier site also suggest that this valley was ice free for several millennia during the Holocene. Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ∼1 ka, ∼ 430 yr and ∼300 yr. A comparison of this new dataset with the available 10Be ages from other southern mid-latitude regions during the Holocene allows the identification of three different glacier evolution patterns. We suspect that variations of Kerguelen glaciers, which are located in the Southern Indian Ocean, were controlled by the combined effects of sea surface temperature related to the variations of the Antarctic Polar Front and fluctuations of precipitation related to long-term variations of the Southern Annular Mode.

Glacier Recession in the Altai Mountains after the LIA Maximum

The study aims to reconstruct the Altai glaciers at the maximum of the LIA, to estimate the reduction of the Altai glaciers from the LIA maximum to the present, and to analyze glacier reduction rates on the example of the Tavan Bogd mountain range. Research was based on remote sensing and field data. The recent glaciation in the southern part of the Altai is estimated (1256 glaciers with the total area of 559.15 ± 31.13 km2), the area of the glaciers of the whole Altai mountains is estimated at 1096.55 km2. In the southern part of Altai, 2276 glaciers with a total area of 1348.43 ± 56.16 km2 were reconstructed, and the first estimate of the LIA glacial area for the entire Altai mountain system was given (2288.04 km2). Since the LIA, the glaciers decrease by 59% in the southern part of Altai and by 47.9% for the whole Altai. The average increase in ELA in the southern part of Altai was 106 m. The larger increase of ELA in the relatively humid areas was probably caused by a decrease in precipitation. Glaciers in the Tavan Bogd glacial center degraded with higher rates after 1968 relative to the interval between 1850–1968. One of the intervals of fast glacier shrinkage in 2000–2010 was caused by a dry and warm interval between 1989 and 2004. However, the fast decrease in glaciers in 2000–2010 was mainly caused by the shrinkage or disappearance of the smaller glaciers, and large valley glaciers started a fast retreat after 2010. The study results present the first evaluation of the glacier recession of the entire Altai after the LIA maximum.

A mineralogical study of glacial flour from Three Sisters, Oregon: An analog for a cold and icy early Mars

Geomorphic and mineralogical data from the martian surface indicate liquid water was abundant on the martian surface and near subsurface ∼3.5 to 4 Gyr ago, but whether early Mars had a warm and wet climate or whether it was cold and icy with punctuated periods of warmth is still unknown. Mineral assemblages of sedimentary rocks on Mars help determine past aqueous conditions and sediment sources. Here, we report on the primary and secondary mineral and amorphous assemblage of glacial flour from Collier Glacier valley on the northern flank of North Sister in Oregon, U.S.A. to identify mineralogical characteristics of mafic sediments altered under cold, wet conditions. Collier glacial flour is dominated by primary igneous minerals (plagioclase is dominant, with lesser amounts of pyroxene and olivine) and comprises 10-40 wt.% X-ray amorphous materials. Crystalline secondary phases (e.g., phyllosilicates, zeolite) are not significant contributors to the authigenic alteration assemblage. High-resolution transmission electron microscopic observations of the <2 μm size fraction of the flour demonstrate that the X-ray amorphous materials are both primary (i.e., volcanic glass) and secondary in nature. The secondary X-ray amorphous materials are enriched in Si, Al, and Fe, and we observe incipient phyllosilicate formation associated with primary and secondary amorphous materials. Our results indicate chemical weathering on a cold and icy early Mars would have produced X-ray amorphous materials, but not crystalline secondary phases. We suggest that the abundant X-ray amorphous materials recognized from orbit and in situ on Mars could have formed under cold and periodically wet conditions similar to those on North Sister today. Furthermore, the lack of volumetrically significant phyllosilicate formation in Collier Glacier flour indicates phyllosilicates on Mars did not form in a cold and wet climate.

Glacial burst triggered by triangular wedge collapse: a study from Trisul Mountain near Ronti glacier valley

Himalayan mountain ranges separate the Tibetan plateau from the Indian subcontinent, where challenging topography, ongoing orogeny, and weather conditions are significant factors behind mass movements. The detachment of a composite rock-ice mass occurred on 7-Feb-2021 over the north-eastern slope of the Trisul mountain resulting in devastation along the Rishiganga-Dhauliganga valley, Uttarakhand. In this study, an attempt is made to understand the failure mechanism of the overhang wedge, where prolonged glacial mobility is seen as a possible factor behind the formation of such a structure. The temporal movement (2020–2021; annual & seasonal) of metamorphosed ice is assessed using sub-pixel offset tracking of Sentinel-1A-GRD data. Kinematic analysis checks failure susceptibility due to joint sets within the rockmass. Slope stability analysis is performed using probabilistic back analysis for three values of coefficient of variation (CoV), i.e., 10%, 15%, and 20% considering cohesion (c) and angle of internal friction (ϕ) as random variables. The detachment impact is quantified using rockfall simulation and parameters such as maximum bounce height, total kinetic energy, and translational velocity. Finally, probabilistic analysis of parameters is performed that may be useful in developing a mitigation system.

Determining microclimates, required weather stations, and suitable fruit tree species by using remote sensing techniques: A case study in an arid and subtropical region

To efficiently manage agricultural lands and increase their productivity, the number of meteorological stations needs to be determined, based on the climatic diversity. Darab region in southeastern Iran, which is a hub of agricultural and horticultural production, has only one synoptic station despite its diverse climatic conditions. So, the study's purpose is to determine microclimates, the number of meteorological stations necessary, and the types of plants suitable for cultivation based on landforms, altitudes, and temperatures. The temperature zoning maps were prepared by the IDW method (meteorological stations near the study area) and MODIS satellite image for every month for an average of 15 years (2004–2019). In order to determine the relationship between temperature classes and topographic features, the digital elevation model and topographic position index (TPI) were used, respectively. For each microclimate in the study area, different types of tropical, subtropical, and temperate tree cultivars were determined. According to the results, there are six microclimates in the study area. Correlation results between topography, rainfall and temperature indicate that there is a strong link (R2 = 0.91) between these variables. From these values, 6 classes with 6 microclimates can be determined for the study area, which indicates that 6 meteorological stations are needed. In order to increase productivity, one of the major innovations of this study focused on the relationship between the type of landforms in the region and the type of vegetation. The results showed that canyons, shallow valleys, plains small, open slopes, upper slopes, hills in valleys, and mid-slope ridges are suitable for growing tropical plants; canyons, u-shaped valleys, hills in valleys, and mid-slope ridges are suitable for cultivation of subtropical plants; and upland drainages, canyons, upper slopes, mid-slope ridges, and mountain tops are suitable for cultivation of temperate plants.

Surface Characteristics, Elevation Change, and Velocity of High-Arctic Valley Glacier from Repeated High-Resolution UAV Photogrammetry

Unmanned Aerial Vehicles (UAVs) are being increasingly used in glaciology demonstrating their potential for the generation of high-resolution digital elevation models (DEMs) that can be further used for the evaluation of glacial processes in detail. Such investigations are especially important for the evaluation of surface changes of small valley glaciers, which are not well-represented in lower-resolution satellite-derived products. In this study, we performed two UAV surveys at the end of the ablation season in 2019 and 2021 on Waldemarbreen, a High-Arctic glacier in NW Svalbard. We derived the mean annual glacier surface velocity of 5.3 m. The estimated mean glacier surface elevation change from 2019 to 2021 was −1.46 m a−1 which corresponds to the geodetic mass balance (MB) of −1.33 m w.e. a−1. The glaciological MB for the same period was −1.61 m w.e. a−1. Our survey includes all Waldemarbreen and demonstrates the efficiency of high-resolution DEMs produced from UAV photogrammetry for the reconstruction of changes in glacier surface elevation and velocity. We suggest that glaciological and geodetic MB methods should be used complementary to each other.

Dulung Proglacial Lake, Suru Sub-Basin, Western Himalaya: Evolution, Controls and Impacts on Glacier Stability

Proglacial lakes are continually developing and expanding across the Himalayan glaciered terrain in response to climate change. These lakes are known to destabilize the glaciers by enhancing their frontal ablation, causing higher than average glacier area and mass losses. Thus, to comprehend the dynamics of proglacial lakes and their influence on the overall glacier health, we study the lake-terminating Dulung Glacier located in the Suru sub-basin, Ladakh, western Himalaya and compare it with the adjacent land-terminating Chilung Glacier. The pronounced melting of the Dulung Glacier, supported by glacier topography (surface gradient between accumulation and ablation zone) and valley morphology (wider near the snout and narrower downwards), seems to be the prime reason for the formation, accommodation and sustenance of the proglacial lake. The expansion in proglacial lake (.008 km2a−1) during 1977–2018 is accompanied by an enhanced degeneration of the Dulung Glacier (mass balance: −.47 ± .06 m w.e.a−1, shrinkage rate: .3 ± .001% a−1; retreat rate: 32 ± .7 ma−1, surface ice velocity reduction: 16%), which has accelerated post-1993. In comparison, land-terminating Chilung Glacier shows lower degeneration rates (mass balance: −.28 ± .02 m w.e.a−1; shrinkage rate: .2 ± .001% a−1; retreat rate: 17 ± 0.7 ma−1, surface ice velocity reduction: 8%) during 1971–2018. This suggests a substantial impact of the proglacial lake in enhancing the Dulung Glacier’s sensitivity towards climate change compared to the Chilung Glacier. If the current rate of lake expansion continues, it would further enhance the Dulung Glaciers’ degeneration rates, thus impacting its stability.

Glacier inventory of the Subansiri River Basin in the Brahmaputra catchment using Landsat satellite data: A case study of the Daisaphu Glacier changes

Monitoring of glaciers of the Subansiri River Basin, regardless of geopolitical distribution, is pivotal, as the Subansiri River is one of the most important tributaries of the Brahmaputra River. However, the existing inventories in Eastern Himalayas mostly covered the Indian side, while most of the glacier regions are located in Tibet. For the first time, we constructed a complete, validated glacier and lake inventory using Landsat satellite data. We report 390 glaciers, where 191 are hanging glaciers, 59 ice aprons, 52 cirques, 40 niches, 37 valley glaciers, 9 icecaps and 2 outlet glaciers. The snow‐covered region occupies 0.96% of the total basin area. The study also reports that there are 52 glacial lakes, covering a cumulative area of 3.358 km2. Furthermore, the 37 valley glaciers cover an area of ~144 km2, with lengths ranging between 1.3 and 15.3 km, and a total ice reserve of ~11.95 km3. The largest glacier of the basin is the Daisaphu Glacier, which has an ice reserve of ~2.70 km3. We calculated the retreat of the Daisaphu Glacier to be 16 ma−1 between 1989 and 2014. However, the retreat has been seen to be enhanced, up to 21 ma−1 after 2009. We also estimated the recession rate of 27 other valley glaciers, apart from the Daisaphu Glacier. The recession rate of the glaciers ranges between 2 and 51 ma−1, where 30% of glaciers have retreated at a rate of &lt;10 ma−1, 55% of glaciers have retreated at a rate of &gt;10 ma−1 and 15% of glaciers show no frontal changes since 1985. The pro‐glacial moraine‐dammed lake of the Daisaphu glacier shows growth of 0.471 km2 in area, and an increase of 0.0833 km3 in water volume between 1978 and 2014. This inventory should help in the assessment of future water scenarios and climate change, as it will impact a large community downstream which is dependent on the glaciers which lie across two countries.

Changes in the Surface Elevation of the Laohugou Glacier No. 12 in Western Qilian Mountains

As the largest valley glacier in the Qilian Mountains, the Laohugou glacier No. 12 (LHG12) has shrunk significantly since 1957. In this study, two topographic maps and a WorldView-2 satellite stereopair image data were used to assess the volume and cumulative mass balance of LHG12 located at the western Qilian Mountains during 1957–2015. During the study period, the LHG12 exhibited changes in two processes: slightly ablation and stability in a brief period during 1957–1989 and strong melting and accelerated ablation during 1989–2015. During 1957–2015, the volume of LHG12 decreased by 0.38 km3, the average thickness decreased by 17.23 m, the cumulative mass balance (MB) was −14.69 ± 3.00 m w. e., and ablation was found glacier-wide. By comparing the previous MB simulation and digital elevation model (DEM) differencing results, it was found that the MB simulation results underestimated the strong melting trend of LHG12 since the 1990s. Temperature rose, especially in autumn and winter, and could cause the ice temperature of LHG12 to increase, and LHG12 may become more sensitive to climate change.

Root tensile strength of terrace hedgerow plants in the karst trough valleys of SW China: Relation with root morphology and fiber content

Root tensile strength is commonly affected by root morphology and fiber content, which combinedly affect the effectiveness of terrace hedgerow on controlling soil erosion in sloping farmland. However, the relationships between these root characteristics are still elusive. This study aimed to compare the root tensile strength, root morphologies, and root fiber contents, and quantify their differences among different plant species. Complete root systems of three terrace hedgerow plant species, i.e., O. bodinieri, V. villosa, and D. lablab L. were sampled for detecting root morphologies and fiber contents at different slope positions on a representative hillslope in karst trough valley. Single root specimens were collected to measure root tensile properties for these three plant species. Results showed that most root morphological parameters were the highest in O. bodinieri, followed by D. lablab L. Three plant species presented the same dominant diameter class as < 1.0 mm, and root volumes as < 1.50 cm3. Cellulose with contents closing to 50% was the main fiber type, and increased significantly linearly with the increasing root diameter in both O. bodinieri and V. villosa. The highest tensile strength and Young's modulus were found in D. lablab L., while the best ultimate tensile force and ultimate elongation were displayed in O. bodinieri. Root diameter showed negative power relationships with tensile strength and Young's modulus, a positive power relationship with ultimate tensile force, and a positive linear relationship with ultimate elongation. Our results will deepen the understanding of the terrace hedgerow functions for controlling soil erosion worldwide.

Cover

Front cover: Gold cobblestone lichen (Pleopsidium chlorophanum), a vibrant crustose species thriving in a calcareous glacial valley in western Norway. Photo credit: N. H. Phinney. For more information see “Trait- based response of lichens to large- scale patterns of climate and forest availability in Norway” Nathan H. Phinney et al., (DOI: 10.1111/jbi.14297.

10Be chronology of deglaciation and ice-dammed lake regression in the vicinity of the Mylodon Cave (Cerro Benítez, Patagonia, Chile)

Located 51.5°S in the vicinity of the Southern Patagonian Ice Field, Cerro Benítez and the glacial valley of Lago Sofía host several caves and rock shelters that were occupied by megafauna and humans during the Late Pleistocene, including the Mylodon Cave and two of the oldest archaeological sites in Patagonia. During the last glaciation, Cerro Benítez was alternately covered by the Patagonian Ice Sheet and surrounded by an ice-dammed lake which restricted the access to the caves and rock shelters located under its uppermost level, 155 m a.s.l. This study aims to provide a detailed chronology of the deglaciation and lake regression in Cerro Benítez. The glacial fluctuations and the variations of lake level were reconstructed from multi-scale, remote-sensing data and field geomorphological mapping. In addition, we calculated the surface exposure age of 11 erratic blocks located above and on the lacustrine erosional platform using terrestrial cosmogenic 10Be in order to date ice downwasting and lake regression, respectively. Dates of ice downwasting and lake regression events were modelled from prior surface exposure ages using Bayesian statistics. The results suggest that the Patagonian Ice Sheet locally thinned by at least 300 m during MIS 3 in the aftermath of a major glacial advance. Following deglaciation, the ice-dammed lake experienced a slow local regression (ca. 2.5 mm. a−1) until 16.9 ka B2k, interpreted as the result of lake basin tilting due to differential post-glacial isostatic rebound. This initial phase of lake regression was followed by a faster regression caused by the reversal of the lake drainage between 16.9 and 15.4 ka B2k. We assess the chronological model by comparison with uplift and lakeshore erosion rates from the literature and eventually discuss the implications for megafaunal colonisation of the area.

Blue-ice moraines formation in the Heritage Range, West Antarctica: Implications for ice sheet history and climate reconstruction

Blue ice is found in areas of Antarctica where katabatic winds, focussed by steep surface slopes or by topography around nunataks, cause enhanced surface ablation. This process draws up deeper, older ice to the ice sheet surface, often bringing with it englacial sediment. Prevailing theories for dynamically stable moraine surfaces in East Antarctica suggest that: (i) it is this material, once concentrated, that forms blue-ice moraines (BIM), (ii) that the moraine formation can be dated using cosmogenic isotope approaches, and that, (iii) since we expect an increase in exposure age moving away from the ice margin towards bedrock, dating across the moraine can be used to constrain ice-sheet history. To test this lateral accretion model for BIM formation we visited Patriot, Marble and Independence Hills in the southern Heritage Range, West Antarctica. Detailed field surveys of surface form, sediment and moraine dynamics were combined with geophysical surveys of the englacial structure of the moraines and cosmogenic nuclide analysis of surface clasts. Results suggest sediment is supplied mainly by basal entrainment, supplemented by debris-covered valley glaciers transferring material onto the ice sheet surface, direct deposition from rock-fall and slope processes from nunataks. We find that once sediment coalesces in BIM, significant reworking occurs through differential ablation, slope and periglacial processes. We bring these processes together in a conceptual model, concluding that many BIM in West Antarctica are dynamic and, whilst they persist through glacial cycles, they do not always neatly record ice sheet retreat patterns since linear distance from the ice margin does not always relate to increased clast exposure age. Understanding the dynamic processes involved in moraine formation is critical to the effective interpretation of the typically large scatter of cosmogenic nuclide exposure ages, opening a deep window into the million-year history of the West Antarctic Ice Sheet.

Circumpolar ocean stability on Mars 3 Gy ago

What was the nature of the Late Hesperian climate, warm and wet or cold and dry? Formulated this way the question leads to an apparent paradox since both options seem implausible. A warm and wet climate would have produced extensive fluvial erosion but few valley networks have been observed at the age of the Late Hesperian. A too cold climate would have kept any northern ocean frozen most of the time. A moderate cold climate would have transferred the water from the ocean to the land in the form of snow and ice. But this would prevent tsunami formation, for which there is some evidence. Here, we provide insights from numerical climate simulations in agreement with surface geological features to demonstrate that the Martian climate could have been both cold and wet. Using an advanced general circulation model (GCM), we demonstrate that an ocean can be stable, even if the Martian mean surface temperature is lower than 0°C. Rainfall is moderate near the shorelines and in the ocean. The southern plateau is mostly covered by ice with a mean temperature below 0°C and a glacier return flow back to the ocean. This climate is achieved with a 1-bar CO2-dominated atmosphere with 10% H2 Under this scenario of 3 Ga, the geologic evidence of a shoreline and tsunami deposits along the ocean/land dichotomy are compatible with ice sheets and glacial valleys in the southern highlands.

Subglacial lakes and their changing role in a warming climate

Subglacial lakes are repositories of ancient climate conditions, provide habitats for life and modulate ice flow, basal hydrology, biogeochemical fluxes and geomorphic activity. In this Review, we construct the first global inventory of subglacial lakes (773 in total), which includes 675 from Antarctica (59 newly identified), 64 from Greenland, 2 beneath the Devon Ice Cap, 6 beneath Iceland’s ice caps and 26 from valley glaciers. This inventory is used to evaluate subglacial lake environments, dynamics and their wider impact on ice flow and sediment transport. The behaviour of these lakes is conditioned by their subglacial setting and the hydrological, dynamic and mass balance regime of the overlying ice mass. Regions where climate warming causes ice surface steepening are predicted to have fewer and smaller lakes, but increased activity with higher discharge drainages of shorter duration. Coupling to surface melt and rainfall inputs will modulate fill–drain cycles and seasonally enhance oxic processes. Higher discharges cause large, transient ice flow accelerations but might result in overall net slowdown owing to the development of efficient subglacial drainage. Subglacial lake research requires new drilling technologies and the integration of geophysics, satellite monitoring and numerical modelling to provide insight into the wider role of subglacial lakes in the changing Earth system. Subglacial lakes modify glacial conditions and flow. This Review provides a first global inventory of subglacial lakes, as well as outlining their settings, impacts and potential changes with climate warming.

ГЕОДИНАМІКА

The aim of the research is to analyze the factors of development, distribution and landscape differentiation of geological and geomorphological processes in the subalpine and alpine highlands of Chornohora, as well as to determine the influence of geological structure and morphometric features on the intensity of their development. The methodological basis of the study is a combination of methods of field research and geoinformation analysis using GIS, which allowed to identify the main centers of the highlands of Chornohora of rockfalls, screes, landslides and linear erosion. On the basis of the landscape approach the spatial differentiation of geological and geomorphological processes in high altitude terrains and landscape structures is analyzed and their complex analysis is carried out, and with the help of geoinformation and statistical data processing on location and number of cells the intensity of negative processes is calculated. The main result of the study is a map of the distribution of negative geological and geomorphological processes (rockfalls, screes, landslides and linear erosion) in the landscape complexes of the subalpine and alpine highlands of Chornohora, as well as a map of a key area near Smotrych Mountain, which expresses landscape processes at the level of landscape striyas and tracts. As a result of the research the structure and specifics of development of geological-geomorphological processes in geocomplexes of different origin and with different morphological and morphometric parameters are analyzed. The influence of geological structure on the development of processes is manifested in the dominance of massive sandstones and sandstone flysch, which contributed to the development of large and steep landforms with inherent intense rockfalls, screes and linear erosion. The analysis of the intensity of the manifestation of these processes testifies to their greatest development in the geocomplexes of ancient-glacial-exarational genesis – corries, cirques, glacial troughs, nival niches, etc. The development, nature and intensity of the manifestation of negative geological and geomorphological processes in landscape complexes of nival erosion and denudation genesis differ significantly. The peculiarity of the differentiation of processes here is their clear dependence on the composition and peculiarities of the occurrence of bedrock stratum, relief morphometry and so on. An important result of the study is the above-mentioned map of the highlands in the vicinity of Smotrych Mountain, which expresses the previously little-studied landslides to the narrow bands of argillites and argillite flysch. Originality. The relationship between the diversity and distribution of negative geological and geomorphological processes with the genesis of landscape complexes of the Chornohora highlands, their structure, structural-lithological and morphometric features is determined. Landscape differentiation and intensity of rockfalls, screes, landslides and linear erosion in the highlands of the studied massif are analyzed and described. Practical significance. The results of the study contribute to the further study of the dynamics and properties of highlands landscape complexes of Chornohora, as well as provide an opportunity to predict the peculiarities of the geological situation and optimize the nature management system, in particular - organizational features of recreational and tourist activities.

Tying policy to system: Does the Ross Sea region marine reserve protect transport pathways connecting the life history of Antarctic toothfish?

A central objective of the Ross Sea region Marine Protected Area (MPA) is to protect areas important to the life cycle of Antarctic toothfish (Dissostichus mawsoni), a top fish predator and by far the region’s most important commercial species. Juvenile toothfish predominate in deep basins along the inner continental shelf, whereas adults are found mostly along the continental slope and spawning areas on the Pacific-Antarctic Ridge. The inner basins connect to the continental slope via glacial troughs and predictable transport along each trough results in exchange with the Antarctic Slope Current as it flows westward. From the slope, two transport pathways, an eastern one from Iselin Bank and a western one that turns cyclonically along the flank of the Southeast Indian Ridge, connect northward to the Pacific-Antarctic Ridge, where the northern arm of the Ross Gyre and the Antarctic Circumpolar Current flow eastward. Using a circulation model to compare transport pathways connecting toothfish life history areas, we consider which inshore basins are likely most important in contributing to adult spawning aggregations; how transport pathways from each may be expected to influence distributions along the continental slope and Pacific-Antarctic Ridge; and how zonal transport pathways may promote export to areas downstream of the marine reserve. Although the MPA protects some critical life history pathways for toothfish, others remain vulnerable to commercial fishing, and we argue that those in adjacent areas along the Iselin Bank, Pacific-Antarctic Ridge and the Amundsen Sea might usefully be protected, discussing the range of policy instruments available. We also recommend consideration of transport pathways in deliberations for a proposed network of Southern Ocean MPAs, introducing a system-based tool using chemical tracers in otoliths that can test for toothfish movement between areas connected along the Antarctic Slope Current and Antarctic Circumpolar Current.

Glacial processes and landforms

AbstractFrom 1965 to 2000 glacial geomorphology became increasingly specialized and developed significantly due to technological improvements, particularly in remote sensing, surveying and field-based glaciological process studies. The better understanding of basal thermal regimes in ice sheets and glaciers led to the development of concepts such as spatial and temporal migration of ice divides in dynamic ice sheets that could overprint subglacial landform assemblages, debris entrainment processes related to polythermal glacier systems, and glacier and ice sheet beds composed of cold and warm based mosaics. Process observations at the ice–bed interface led to the discovery of the third glacier flow mechanism, substrate deformation, which provided the impetus to reconstruct the genesis of subglacial bedforms such as drumlins and to evaluate the origins and potential flow law for till. Numerical evaluations of glacial erosion led to a better understanding of abrasion and quarrying as well as the erection of genetic models and erosion rates for larger-scale features such as U-shaped valleys and cirques. Linkages were made between debris transport pathways and moraine construction in supraglacial environments, with the role of glacier structure being linked to specific landforms, such as medial, lateral, hummocky and ice-cored moraines as well as rock glaciers. Our appreciation of the erosional and depositional impacts of glacifluvial systems was enhanced significantly with the advent of process observations on the hydrology of modern glaciers as well as the final vindication of J.H. Bretz and his proposed jökulhlaup origins of the Channelled Scablands and the Missoula Floods. In addition to the increasing numbers of studies at modern glacier snouts, the embracing of sedimentology by glacial geomorphologists was to result in significant developments in understanding the process-form regimes of subglacial, marginal and proglacial landforms, particularly the recognition of landform continua and hybrids. Advances resulting from this included the recognition of different modes of moraine and glacitectonic thrust mass development, lithofacies models of the varied glacifluvial depositional environments, and the initial expansion of work on the sediments and depocentres of glacimarine settings, the latter being the result of glacial research taking to submersibles and ice-strengthened ships for the first time. A similarly new frontier was the expansion of research on the increasingly higher resolution images returning from Mars, where extraterrestrial glaciations were recognized based on comparisons with Earth analogues. Holistic appreciations of glaciation signatures using landform assemblages were developed, initially as process-form models and later as glacial landsystems, providing an ever-expanding set of templates for reconstructing palaeoglaciology in the wide variety of topographic and environmental settings, which also acknowledge spatial and temporal change in glacier and ice sheet systems.

Early Holocene cold snaps and their expression in the moraine record of the eastern European Alps

Abstract. Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier–climate system over the past millennia is particularly relevant first because the amplitude and frequency of natural climate variability during the Holocene provides the climatic context against which modern, human-induced climate change must be assessed. Second, the transition from the last glacial to the current interglacial promises important insights into the climate system during warming, which is of particular interest with respect to ongoing climate change. Evidence of stable ice margin positions that record cooling during the past 12 kyr are preserved in two glaciated valleys of the Silvretta Massif in the eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped and dated moraines in these catchments including historical ridges using beryllium-10 surface exposure dating (10Be SED) techniques and correlate resulting moraine formation intervals with climate proxy records to evaluate the spatial and temporal scale of these cold phases. The new geochronologies indicate the formation of moraines during the early Holocene (EH), ca. 11.0 ± 0.7 ka (n = 19). Boulder ages along historical moraines (n = 6) suggest at least two glacier advances during the Little Ice Age (LIA; ca. 1250–1850 CE) around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred around 500 CE. The Jamtal and Laraintal moraine chronologies provide evidence that millennial-scale EH warming was superimposed by centennial-scale cooling. The timing of EH moraine formation coincides with brief temperature drops identified in local and regional paleoproxy records, most prominently with the Preboreal Oscillation (PBO) and is consistent with moraine deposition in other catchments in the European Alps and in the Arctic region. This consistency points to cooling beyond the local scale and therefore a regional or even hemispheric climate driver. Freshwater input sourced from the Laurentide Ice Sheet (LIS), which changed circulation patterns in the North Atlantic, is a plausible explanation for EH cooling and moraine formation in the Nordic region and in Europe.