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Our ability to improve prognostic modeling of the Greenland Ice Sheet relies on understanding the long-term relationships between climate and mass flux (via iceberg calving) from marine-terminating tidewater glaciers (TWGs). Observations of recent TWG behavior are widely available, but long-term records of TWG advance are currently lacking. We present glacial geomorphological, sedimentological, archaeological, and modeling data to reconstruct the ~20 km advance of Kangiata Nunaata Sermia (KNS; the largest tidewater glacier in southwest Greenland) during the first half of the past millennium. The data show that KNS advanced ~15 km during the 12th and 13th centuries CE at a rate of ~115 m a−1, contemporaneous with regional climate cooling toward the Little Ice Age and comparable to rates of TWG retreat witnessed over the past ~200 years. Presence of Norse farmsteads proximal to KNS demonstrates their resilience to climate change, manifest as a rapidly advancing TWG in a cooling climate. The results place limits on the magnitude of ice-margin advance and demonstrate TWG sensitivity to climate cooling as well as warming. These data combined with our grounding-line stability analysis provide a long-term record that validates approaches to numerical modeling aiming to link calving to climate.

Nioghalvfjerdsbrae, or 79∘ N Glacier, is the largest marine-terminating glacier draining the Northeast Greenland Ice Stream (NEGIS). In recent years, its ∼ 70 km long fringing ice shelf (hereafter referred to as the 79∘ N ice shelf) has thinned, and a number of small calving events highlight its sensitivity to climate warming. With the continued retreat of the 79∘ N ice shelf and the potential for accelerated discharge from NEGIS, which drains 16 % of the Greenland Ice Sheet (GrIS), it has become increasingly important to understand the long-term history of the ice shelf in order to put the recent changes into perspective and to judge their long-term significance. Here, we reconstruct the Holocene dynamics of the 79∘ N ice shelf by combining radiocarbon dating of marine molluscs from isostatically uplifted glaciomarine sediments with a multi-proxy investigation of two sediment cores recovered from Blåsø, a large epishelf lake 2–13 km from the current grounding line of 79∘ N Glacier. Our reconstructions suggest that the ice shelf retreated between 8.5 and 4.4 ka cal BP, which is consistent with previous work charting grounding line and ice shelf retreat to the coast as well as open marine conditions in Nioghalvfjerdsbrae. Ice shelf retreat followed a period of enhanced atmospheric and ocean warming in the Early Holocene. Based on our detailed sedimentological, microfaunal, and biomarker evidence, the ice shelf reformed at Blåsø after 4.4 ka cal BP, reaching a thickness similar to present by 4.0 ka cal BP. Reformation of the ice shelf coincides with decreasing atmospheric temperatures, the increased dominance of Polar Water, a reduction in Atlantic Water, and (near-)perennial sea-ice cover on the adjacent continental shelf. Along with available climate archives, our data indicate that the 79∘ N ice shelf is susceptible to collapse at mean atmospheric and ocean temperatures ∼ 2 ∘C warmer than present, which could be achieved by the middle of this century under some emission scenarios. Finally, the presence of “marine” markers in the uppermost part of the Blåsø sediment cores could record modern ice shelf thinning, although the significance and precise timing of these changes requires further work.

The Northeast Greenland Ice Stream has recently seen significant change to its floating margins and has been identified as vulnerable to future climate warming. Inflow of warm Atlantic Intermediate Water (AIW) from the continental shelf has been observed in the vicinity of the Nioghalvfjerdsfjorden (79∘ N) Glacier calving front, but AIW penetration deep into the ice shelf cavity has not been observed directly. Here, we report temperature and salinity measurements from profiles in an epishelf lake, which provide the first direct evidence of AIW proximal to the grounding line of 79∘ N Glacier, over 50 km from the calving front. We also report evidence for partial un-grounding of the margin of 79∘ N Glacier taking place at the western end of the epishelf lake. Comparison of our measurements to those close to the calving front shows that AIW transits the cavity to reach the grounding line within a few months. The observations provide support for modelling studies that infer AIW-driven basal melt proximal to the grounding line and demonstrate that offshore oceanographic changes can be rapidly transmitted throughout the sub-ice-shelf cavity, with implications for near-future stability of the ice stream.

In this study, we compare equilibrium-line altitudes (ELAs) calculated using the area–altitude balance ratio (AABR) and the accumulation–area ratio (AAR) methods, with measured ELAs derived from direct field observations. We utilise a GIS toolbox to calculate the ELA for 64 extant glaciers by applying the AABR and AAR methods to DEMs and polygons of their geometry. The calculated ELAs (c-ELAs) are then compared to measured zero-net balance ELAs (znb-ELAs) obtained from mass-balance time series held by the WGMS for the same glaciers. The correlation between znb-ELAs and AABR (1.56)/AAR (0.58) c-ELAs is very strong, with an r2 = 0.99. The smallest median difference between znb-ELAs and c-ELAs (i.e. 65.5 m) is obtained when a globally representative AABR of 1.56 is used. When applied to palaeoglacier-climate applications, this difference translates to ~0.42°C, well within the uncertainty of palaeotemperature proxies used to determine mean summer temperature at the ELA. The more widely used mean AABR of 1.75 is shown to be statistically invalid due to the skewness of the dataset. On this basis, when calculating glacier ELAs, we recommend the use of a global AABR value of 1.56.

Nioghalvfjerdsbrae, or 79° N Glacier, is the largest marine-terminating glacier draining Northeast Greenland Ice Stream (NEGIS). In recent years, it’s ~70 km-long fringing ice shelf (hereafter referred to as 79° N ice shelf) has thinned, and a number of small calving events highlight its sensitivity to climate warming. With the continued retreat of 79° N ice shelf and the potential for accelerated discharge from NEGIS, which drains 16 % of the Greenland Ice Sheet (GrIS), it has become increasingly important to understand the long-term history of the ice shelf in order to put the recent changes into perspective and to judge their long-term significance. Here we reconstruct the Holocene dynamics of 79° N ice shelf by combining radiocarbon dating of marine mollusc from isostatically uplifted glacimarine sediments with a multi-proxy investigation of two sediment cores recovered from Blåsø, a large epishelf lake 2–13 km from the current grounding line of 79° N Glacier. Our reconstructions suggest that the ice shelf retreated between 8.5 and 4.4 cal. ka. BP, which is consistent with previous work charting grounding line and ice shelf retreat to the coast, and open marine conditions in Nioghalvfjerdsbrae. Ice shelf retreat followed a period of enhanced atmospheric and ocean warming in the Early Holocene. Based on our detailed sedimentological, microfaunal and biomarker evidence the ice shelf reformed at Blåsø after 4.4 cal. ka BP, reaching a thickness similar to present by 4.0 cal. ka BP. Reformation of the ice shelf coincides with decreasing atmospheric temperatures, increased dominance of Polar Water, a reduction in Atlantic Water and (near) perennial sea-ice cover on the adjacent continental shelf. Together with available climate archives our data indicate that 79° N ice shelf is susceptible to collapse when mean atmospheric and ocean temperatures are ~2 °C warmer than present, which could be achieved by the middle of this century under some climate model scenarios. Finally, the presence of ‘marine’ markers in the uppermost part of the Blåsø sediment cores could record modern ice shelf thinning, although the significance and precise timing of these changes requires further work.

Cirques are glacially eroded, bowl-shaped depressions, characterised by steep headwalls and flat or overdeepened floors. Given their association with past glaciers, cirques are sometimes used as proxies for palaeoclimate. However, cirques are shaped over multiple glacial cycles, and their usefulness as palaeoclimate indicators therefore remains open to question. In this paper, we map 3984 glacier-free cirques across the Scandinavian Peninsula and analyse variations in cirque floor altitude (CFA). We explore the relationships between CFAs and cirque aspect, latitude, longitude, and distance to the coast. We test the validity of using CFAs as indicators of palaeoclimate through comparison with the equilibrium-line altitudes (ELAs) of 513 modern cirque glaciers. Results indicate that both CFAs and modern cirque-glacier ELAs decrease with latitude and vary with aspect, being generally lowest on east-facing slopes. However, the clearest and strongest trend in both CFAs and modern cirque glacier ELAs is an increase in elevation with distance from the modern coast (i.e., distance ‘inland’). This likely indicates that similar climatic gradients, particularly an inland reduction in precipitation, acted to regulate former sites of glacier initiation (reflected by CFAs) and modern glacier ELAs. This would imply that CFAs are a useful proxy for palaeoclimate. However, we note that both CFAs and modern ELAs reflect the general topography of this region (with increasing elevations moving inland), and the glacial history of the area (indirectly linked to palaeoclimate) may have played a role in regulating where cirques have formed. For these reasons, we suggest that palaeoclimatic interpretations derived from CFAs should be treated with caution.

Sediments deposited by glacial meltwaters (for example, ice‐contact delta deposits) form permeable packages in the subsurface that can act as reservoirs for both water and hydrocarbons. They are also an important source of aggregate for the construction industry. As reservoirs they are challenging to characterize in terms of their structure, flow and storage properties due to their complex depositional history. In this study, ice‐contact deltas of Salpausselkä I and II end moraines in Southern Finland are studied using a combination of geomorphological mapping, sedimentological studies and near surface geophysical methods. Sedimentary logs from isolated outcrops were correlated to ground penetrating radar (GPR) profiles to unravel the internal structure and depositional history of these ice‐contact deltas. Subsequently, electrical resistivity tomography (ERT) and gravity data were analysed to estimate the depth to bedrock and to model porosity distribution within the sediments. Results of the study suggest that the delta deposits have a broad range of porosities (10 to 42%) with lowest values found in the bottomset beds. The most variable porosities are in the subaqueous ice‐contact–fan zone, and consistently high porosities occur in delta foreset/topset facies. Detailed sedimentary logging linked to the GPR data shows heterogeneities such as mud drapes on foresets and kettle holes which are below the resolution of ERT and gravity methods but significantly affect reservoir properties of the deltas. Moreover, oscillation of the ice‐margin may have introduced larger heterogeneities (for example, buried ice marginal ridges, or eskers) into the sedimentary sequence which are atypical for other Gilbert‐type deltas. Finally, subglacially sculpted, highly variable bedrock topography exerts a major control on sediment distribution within the delta making reservoir volume and quality less predictable. This work has implications for present‐day freshwater aquifers and low enthalpy geothermal energy in southern Finland and other deglaciated regions, as well as hydrocarbon exploration of analogous deposits in the subsurface from Pleistocene and pre‐Pleistocene glaciogenic sequences.

Multi-temporal inventories of glacierised regions provide an improved understanding of water resource availability. In this study, we present a Landsat-based multi-temporal inventory of glaciers in four Upper Indus sub-basins and three internal drainage basins in the Ladakh region for the years 1977, 1994, 2009 and 2019. The study records data on 2257 glaciers (of individual size >0.5 km2) covering an area of ∼7923±106 km2 which is equivalent to ∼30 % of the total glacier population and ∼89 % of the total glacierised area of the region. Glacier area ranged between 0.5±0.02 and 862±16 km2, while glacier length ranged between 0.4±0.02 and 73±0.54 km. Shayok Basin has the largest glacierised area and glacier population, while Tsokar has the least. Results show that the highest concentration of glaciers is found in the higher elevation zones, between 5000 and 6000 m a.s.l., with most of the glaciers facing towards the NW–NE quadrant. The error assessment shows that the uncertainty, based on the buffer-based approach, ranges between 2.6 % and 5.1 % for glacier area, and 1.5 % and 2.6 % for glacier length with a mean uncertainty of 3.2 % and 1.8 %, respectively. This multitemporal inventory is in good agreement with previous studies undertaken in parts of the Ladakh region. The new glacier database for the Ladakh region will be valuable for policy-making bodies, and future glaciological and hydrological studies. The data can be viewed and downloaded from PANGAEA, https://doi.org/10.1594/PANGAEA.940994 (Soheb et al., 2022).

The concept of Quaternary average conditions has gained popularity over the past few decades, especially with studies of long-term landscape evolution. In this paper, we critically assess this concept by analyzing the marine isotope record (LR04 δ18O stack) relative to the Quaternary. This shows that the frequency and amplitude of climate glacial-interglacial cycles are not constant throughout the Quaternary, with a clear change during the Middle Pleistocene Transition (MPT), and that many minor oscillations exist within each cycle. For this reason, the identification of pre- and post-MPT most-frequent and, cumulatively, longest-lasting (rather than average) conditions is recommended. The most-frequent pre-MPT δ18O value of 3.725 ± 0.025‰ last occurred during 11.31–11.47 ka, while the most-frequent post-MPT δ18O value of 4.475 ± 0.025‰ last occurred during 14.81–15.04 ka. However, many other δ18O values were almost as frequent throughout the Quaternary and we present geomorphological reasons as to why it is unlikely that the present-day landscape reflects Quaternary average or, indeed, most-frequent conditions. Collectively, our results indicate that extreme caution should be taken when attempting to infer long-term landscape evolution processes (including the buzzsaw hypothesis) based on average Quaternary conditions.

The Department of Geography has been engaged with glaciological research from its early beginnings. The paper concentrates on the period from the appointment of Chalmers Clapperton in 1962 onwards,...

The Greenland Ice Sheet (GrIS) is known to have experienced widespread retreat over the last century. Information on outlet glacier dynamics, prior to this, are limited due to both a lack of observations and a paucity of mapped or mappable deglacial evidence which restricts our understanding of centennial to millennial timescale dynamics of the GrIS. Here we present glacial geomorphological mapping, for upper Godthåbsfjord, covering 5800 km2 at a scale of 1:92,000, using a combination of ASTER GDEM V2, a medium-resolution DEM (error

The Younger Dryas (YD) was a period of rapid climate cooling that occurred at the end of the last glaciation. Here, we present the first palaeoglacier-derived reconstruction of YD precipitation across Europe, determined from 122 reconstructed glaciers and proxy atmospheric temperatures. Positive precipitation anomalies (YD versus modern) are found along much of the western seaboard of Europe and across the Mediterranean. Negative precipitation anomalies occur over the Fennoscandian ice sheet, the North European Plain, and as far south as the Alps. This is consistent with a more southerly and zonal storm track, which is linked to a concomitant southern location of the Polar Frontal Jet Stream, generating cold air outbreaks and enhanced cyclogenesis, especially over the eastern Mediterranean. This atmospheric configuration resembles the modern Scandinavian (SCAND) circulation over Europe (a blocking high pressure over Scandinavia pushing storm tracks south and east), and by analogy, a seasonally varying palaeoprecipitation pattern is interpreted., Science Advances, 6 (50), ISSN:2375-2548

This work was supported by an EU-Interact TA grant (GLEESP), the ECONORS fast-track initiative from the Centre for Climate Dynamics (SKD) at the Bjerknes Centre for Climate Research and the Research Council of Norway through the Centre for Geobiology (CGB). We thank Torgeir Rothe and Craig Frew for helping retrieve the studied sediment cores, Jordan Donn Holl for helping carry out lab analyses and Tor Einar Moller for his thorough proof-reading. Finally, we acknowledge Stein-Erik Lauritzen and Sverre Aksnes for measuring 210Pb activity on dated sediment samples.

We map glacial cirques, and analyse spatial variability in their altitude and aspect to derive a long-term, time-integrated, perspective on climate patterns during former periods of mountain glaciation (likely spanning multiple Quaternary glaciations) in Britain and Ireland. The data reveal that, although air temperatures were important, exposure to moisture-bearing air masses was the key factor in regulating sites of former mountain glacier formation, and indicate that during such periods, moisture supply was largely controlled by North Atlantic westerlies, with notable inland precipitation gradients (precipitation decreasing inland), similar to present day. In places, trends in cirque altitude may also reflect regional differences in the extent of cirque deepening, controlled by the dimensions and dynamics of the glaciers that came to occupy them. Specifically, comparatively deep cirques in coastal locations may reflect the former presence of dynamic (fed by moisture from the North Atlantic), but comparatively small, glaciers (largely confined to their cirques). By contrast, decreasing cirque depth further inland, may reflect the former presence of larger and/or less dynamic ice masses, occupying comparatively continental climatic conditions.

This paper presents two high-resolution pollen records dating to ~AD 1000-1400 that reveal the impacts of Norse colonists on vegetation and landscape around a remote farmstead in the Western Settlement of Greenland. The study is centred upon a ‘centralised farm’ (ruin group V53d) in Austmannadalen, near the margin of the Greenland Ice Sheet (64º13’ N, 49º49’W). The climate is low arctic and considered marginal in terms of its suitability for the type of pastoral agriculture that the Norse settlers introduced. The data reveal that at a short distance (~500 m) from the farm buildings, the palynological ‘footprint’ for settlement becomes extremely indistinct, the only clear palaeoenvironmental evidence for a human presence being elevated levels of microscopic charcoal. This contrasts with the Eastern Settlement, where a strong palynological signature for Norse landnám is evident, from the local (individual farm) through to the regional (landscape) scale. The palynological data from Austmannadalen, and the Western Settlement more generally, imply that farming occurred at very low intensity. This aligns with ideas that promote the importance of hunting, and trade in valuable Arctic commodities (e.g. walrus ivory), ahead of a search for new pasture as the dominant motivation driving the Norse settlement of this region.

Source at https://doi.org/10.1016/j.margeo.2019.05.001. Marine-based ice streams are responsible for a significant proportion of the ice mass loss from the present-day Greenland Ice Sheet, East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) but the processes controlling their initiation, evolution and shutdown remain elusive, hindering our understanding of how existing ice masses will respond to predicted future warming. The exposed beds of palaeo-ice streams offer a unique opportunity to study subglacial processes, which are largely inaccessible in contemporary settings. We use high resolution multibeam swath bathymetry data from the Barents Sea to map the geomorphology of a palaeo-ice stream bed, located in Olgastretet (Olga Trough), approximately 75 km southeast of Kong Karls Land and 200 km east of central Svalbard. This reveals evidence for shut down of a marine-based ice stream, followed by a phase of passive retreat or lift-off of the ice stream facilitating preservation of crevasse-squeeze ridges (CSRs). Subsequently, active retreat of the ice margin was re-established and is marked by recessional moraine ridges located upstream of the CSRs. Previously, CSRs have been mainly associated with surging land-terminating ice margins, however our work adds to recent observations of CSRs on the beds of marine-based ice streams, implying that they may be more common than previously thought. It also indicates that marine-based ice streams may switch on- and off in a surge-like manner which has important implications for our understanding of ice stream life cycles and the modelling of ice sheets.

All marine communities in Greenland are experiencing rapid environmental change, and to understand the effects on those structured by seaweeds, baseline records are vital. The kelp and coralline algae habitats along Greenland&rsquo, s coastlines are rarely studied, and we fill this knowledge gap for the area around Nuuk, west Greenland. Using subtidal swath surveys, photo-quadrats, and grab samples, we characterised the diversity of floral and faunal assemblages in kelp forests and coralline algae beds. The most abundant herbivore assemblages and the most diverse communities occur in the interstitial habitats of rhodolith beds. In kelp forests, species diversity is higher in epi-benthic (photo-quadrat) and mid-water (swath) surveys. These habitats are not mutually exclusive, Agarum clathratum is prominent in coralline algal habitats, while crustose coralline algae cover the bedrock under kelp holdfasts. Overall, the suite of surveys used capture the diverse communities within kelp forests and coralline algae in Greenland and their differing role in the life history of the inhabitants. Furthermore, coralline algae beds are an important carbonate store, with CaCO3 concentrations ranging from 28.06 to 103.73 g&middot, m&minus, 3. Our research sets the baseline for continued investigations and monitoring of these important habitats and their supported fisheries.

Glacier reconstructions are widely used in palaeoclimatic studies and this paper presents a new semi-automated method for generating glacier reconstructions: GlaRe, is a toolbox coded in Python and operating in ArcGIS. This toolbox provides tools to generate the ice thickness from the bed topography along a palaeoglacier flowline applying the standard flow law for ice, and generates the 3D surface of the palaeoglacier using multiple interpolation methods. The toolbox performance has been evaluated using two extant glaciers, an icefield and a cirque/valley glacier from which the subglacial topography is known, using the basic reconstruction routine in GlaRe. Results in terms of ice surface, ice extent and equilibrium line altitude show excellent agreement that confirms the robustness of this procedure in the reconstruction of palaeoglaciers from glacial landforms such as frontal moraines. GlaRe is a tool for palaeoglacier 3D surface reconstruction from bed topography.GlaRe is coded in Python and runs in ArcGIS as a toolbox.The theory of perfect plasticity equilibrium glacier profile is considered.Interpolation methods for glacier 3D surface creation are described and discussed.GlaRe is tested with two extant glaciers, showing a small, acceptable error.

Glaciogenic sediments are present in many hydrocarbon-producing basins across the globe but their complex nature makes it difficult to characterise the reservoir-quality sedimentary units. Despite this, Ordovician glacial deposits in North Africa, and Carboniferous-Permian glaciogenic sequences in the Middle East, have been proven to host significant, economical, hydrocarbon accumulations. Additionally, discoveries have been made in the shallow (

The equilibrium-line altitudes (ELAs) of reconstructed palaeoglaciers have been widely used to assess palaeoclimatic conditions, yet this concept has rarely been tested using modern glaciers. To address this shortcoming, correlations between the ELAs of 513 modern cirque glaciers and present-day climatic and topographic variables across Scandinavia, as well as regional trends in ELA and climate, are analysed. ELAs are calculated using the Area-Altitude-Balance-Ratio method, with a ratio of 1.5 ± 0.4. Results indicate that glacier ELAs are strongly correlated with distance from the coast. This reflects the present-day precipitation pattern of the region (characterised by high precipitation near the sea) and demonstrates a climate dominated by a maritime-continental transition. Temperature explains differences in glacier ELA regional trends as well as ELA changes with latitude. Following standard meteorological convention, Scandinavia is divided into two macro-climate regions and analyses are run within the macro-regions as well as the complete dataset. The strength of correlations between ELA and precipitation increases when the study is divided into northern and southern macro-regions. These results test long held assumptions about relationships between climate and cirque glacier ELA, which is of particular relevance to palaeoclimatic studies based on the reconstruction of former cirque glaciers.

In Greenland, free‐living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in Godthåbsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured in situ during summers of 2015 and 2016, and annual patterns of productivity in L. glaciale were monitored in lab‐based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold‐room measurements indicate that both L. glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 ± 0.17 or 0.002 ± 0.023 μmol CaCO3 · g−1 · h−1 and ‐0.007 ± 0.003 or ‐0.004 ± 0.001 mg O2 · L−1 · h−1 in each species respectively. Mesocosm experiments indicate L. glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Further, metabolic processes in L. glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 ± 1.73 mg · d−1 of biomass through summer. These results indicate high freshwater input to the Godthåbsfjord region may drive the low abundance of L. glaciale, and could decrease species distribution as climate change increases fresh water input to the Arctic marine system via enhanced ice sheet runoff and glacier calving.

Geometries of Early Pleistocene [2.58 to 0.78 million years (Ma) ago] ice sheets in northwest Europe are poorly constrained but are required to improve our understanding of past ocean-atmosphere-cryosphere coupling. Ice sheets are believed to have changed in their response to orbital forcing, becoming, from about 1.2 Ma ago, volumetrically larger and longer-lived. We present a multiproxy data set for the North Sea, extending to over a kilometer below the present-day seafloor, which demonstrates spatially extensive glaciation of the basin from the earliest Pleistocene. Ice sheets repeatedly entered the North Sea, south of 60°N, in water depths of up to ~250 m from 2.53 Ma ago and subsequently grounded in the center of the basin, in deeper water, from 1.87 Ma ago. Despite lower global ice volumes, these ice sheets were near comparable in spatial extent to those of the Middle and Late Pleistocene but possibly thinner and moving over slippery (low basal resistance) beds.

The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.

This paper investigates the controls on the formation of subglacially eroded bedrock bedforms beneath the topographically confined region upstream of the Uummannaq Ice Stream (UIS). During the last glacial cycle, palaeoglaciological conditions are believed to have been similar for all sites in the study, characterised by thick, fast-flowing ice moving over a rigid bedrock bed. Classic bedrock bedforms indicative of glacially eroded terrain were mapped, including p-forms, roches moutonnees, and whalebacks. Bedform long axes and plucked face orientations display close correlation (parallel and perpendicular) to palaeo-ice flow directions inferred from striae measurements. Across all sites, elongation ratios (length to width) varied by an order of magnitude between 0.8:1 and 8.4:1. Bedform properties (length, height, width, and long axis orientation) from four subsample areas, form morphometrically distinct populations, despite their close proximity and hypothesised similarity in palaeoglaciological conditions. Variations in lithology and geological structures (e.g., joint frequency; joint dip; joint orientation; bedding plane thickness; and bedding plane dip) provide lines of geological weakness, which focus the glacial erosion, in turn controlling bedform geometries. Determining the relationship (s) between bedding plane dip relative to palaeo-ice flow and bedform shape, relative length, amplitude, and wavelength has important ramifications for understanding subglacial bed roughness, cavity formation, and likely erosion style (quarrying and/or abrasion) at the ice-bed interface. This paper demonstrates a direct link between bedrock bedform geometries and geological structure and emphasises the need to understand bedrock bedform characteristics when reconstructing palaeoglaciological conditions.

Regional scale studies of glacial cirque metrics provide key insights on the (palaeo) environment related to the formation of these erosional landforms. The growing availability of high resolution terrain models means that more glacial cirques can be identified and mapped in the future. However, the extraction of their metrics still largely relies on time consuming manual techniques or the combination of, more or less obsolete, GIS tools. In this paper, a newly coded toolbox is provided for the automated, and comparatively quick, extraction of 16 key glacial cirque metrics; including length, width, circularity, planar and 3D area, elevation, slope, aspect, plan closure and hypsometry. The set of tools, named ACME (Automated Cirque Metric Extraction), is coded in Python, runs in one of the most commonly used GIS packages (ArcGIS) and has a user friendly interface. A polygon layer of mapped cirques is required for all metrics, while a Digital Terrain Model and a point layer of cirque threshold midpoints are needed to run some of the tools. Results from ACME are comparable to those from other techniques and can be obtained rapidly, allowing large cirque datasets to be analysed and potentially important regional trends highlighted.

Several different methodologies have previously been employed in the tracking of glacier terminus change, though a systematic comparison of these has not been undertaken. The frequent application of single methods to multiple glaciers over large geographical areas such as Greenland, raises the question of whether individual methodologies are robust. In this study we evaluate three existing methodologies that have been widely used to track terminus change (the centre-line, bow and box methods) against a full range of idealized glaciological scenarios and six examples of real glaciers. We also evaluate two new methodologies that aim to reduce measurement error compared with the existing methodologies. The first is a modification to the box method that can account for termini retreating through fjords that change orientation (termed the curvilinear box method), while the second determines the average terminus position relative to the glacier centre line using an inverse distance weighting extrapolation (termed the extrapolated centre-line method). No single method tested achieved complete accuracy for all scenarios, though the extrapolated centre-line method was able to successfully account for variable fjord orientation, width and terminus geometry with the least error.

This paper presents the first assessment of the Uummannaq ice stream system (UISS) in West Greenland. The UISS drained ~6% of the Greenland ice sheet (GrIS) at the Last Glacial Maximum (LGM). The onset of the UISS is a function of a convergent network of fjords which feed a geologically controlled trough system running offshore to the shelf break. Mapping, cosmogenic radiogenic nuclide (CRN) dating, and model output reveal that glacially scoured surfaces up to 1266 m above sea level (asl) in fjord-head areas were produced by warm-based ice moving offshore during the LGM, with the elevation of warm-based ice dropping westwards to ~700 m asl as the ice stream trunk zone developed. Marginal plateaux with allochthonous blockfields suggest that warm-based ice produced till and erratics up to ~1200 m asl, but CRN ages and weathering pits suggest this was pre-LGM, with only cold-based ice operating during the LGM. Deglaciation began on the outer shelf at ~14.8 cal. kyrs B.P., with Ubekendt Ejland becoming ice free at ~12.4 ka. The UISS then collapsed with over 100 km of retreat by ~11.4 ka–10.8 cal. kyrs B.P., a rapid and complex response to bathymetric deepening, trough widening, and sea-level rise coinciding with rapidly increasing air temperatures and solar radiation, but which occurred prior to ocean warming at ~8.4 cal. kyrs B.P. Local fjord constriction temporarily stabilized the unzipped UISS margins at the start of the Holocene before ice retreat inland of the current margin at ~8.7 ka.

As John Shaw has repeatedly challenged our interpretations of the glacial geomorphology of western Canada, there are now numerous examples in the literature of our responses to his charges of misrepresentation and/or under-utilization of his work (Benn and Evans, 2006; Evans et al., 2006a, 2008; Evans, 2010; O Cofaigh et al., 2010a). We continue to defend our position by highlighting the fact that we have, at all stages of our research, adhered to the principle of adopting the interpretation that requires the least assumptions.

Ice streams drain large portions of ice sheets and play a fundamental role in governing their response to atmospheric and oceanic forcing, with implications for sea-level change. The mechanisms that generate ice stream flow remain elusive. Basal sliding and/or bed deformation have been hypothesized, but ice stream beds are largely inaccessible. Here we present a comprehensive, multi-scale study of the internal structure of mega-scale glacial lineations (MSGLs) formed at the bed of a palaeo ice stream. Analyses were undertaken at macro- and microscales, using multiple techniques including X-ray tomography, thin sections and ground penetrating radar (GPR) acquisitions. Results reveal homogeneity in stratigraphy, kinematics, granulometry and petrography. The consistency of the physical and geological properties demonstrates a continuously accreting, shallow-deforming, bed and invariant basal conditions. This implies that ice stream basal motion on soft sediment beds during MSGL formation is accommodated by plastic deformation, facilitated by continuous sediment supply and an inefficient drainage system., Ice streams are fundamental to ice sheet dynamics, but the mechanisms controlling their flow remain elusive. Here, the authors perform macro- and microscale analyses of mega-scale glacial lineations, which indicate a continuously accreting, shallow-deforming bed during ice stream flow.

A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-ice stream of the late Wisconsinan southwest Laurentide Ice Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to ice stream shutdown. Ridge orientations are predominantly orientated WNW–ESE, with a subordinate WSW–ENE alignment, both indicative of ice fracture development transverse to former ice stream flow, as indicated by NNE–SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the ice stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of ice streaming, immediately prior to ice stream shutdown. This linear zone of ice fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final active flow unit and the slower moving ice on either side is likely recorded by the up-ice bending of the CSR limbs. The resulting CSR corridor, here related to an individual ice stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at active temperate glacier lobes.

The Uummannaq region is a mosaic of glacial landsystems, consistent with hypothesised landscape distribution resulting from variations in subglacial thermal regime. The region is dominated by selective linear erosion which has spatially and altitudinally partitioned the landscape. Low altitude areas are dominated by glacial scour, with higher elevations are dominated by plateaux or mountain valley and cirque glaciers. The appearance and nature of each landscape type varies locally with altitude and latitude, as a function of bedrock geology and average glacial conditions. Selective linear erosion has been a primary control on landscape distribution throughout Uummannaq, leading to plateau formation and the growth of a coalescent fjord system in the Uummannaq region. This has allowed the development of the Uummannaq ice stream’s (UIS) onset zone during glacial periods. Fjord development has been enhanced by a down-stream change in geology to less-resistant lithologies, increasing erosional efficiency and allowing a single glacial channel to develop, encouraging glacier convergence and the initiation of ice streaming. The landscape has been affected by several periods of regional uplift from 33 Ma to present, and has been subject to subsequent fluvial and glacial erosion. Uplift has removed surfaces from the impact of widespread warm-based glaciation, leaving them as relict landsurfaces. The result of this is a regional altitude-dependant continuum of glacial modification, with extreme differences in erosion between high and low elevation surfaces. This study indicates that processes of long-term uplift, glacial erosion/protection, and spatial variability in erosion intensity have produced a highly partitioned landscape.

Please click here to download the map associated with this article. A1:30,000 scale map of the snout and proglacial landscape of the surging Icelandic glacier Tungnaarjokull, based upon aerial photography from 1995, immediately after a surge, allows an assessment of the spatial variability in landform-sediment imprints of catastrophic glacier advance across upland bedrock ridges. The ice-margin parallel alignment of the bedrock ridges locally strongly directs proglacial meltwater drainage and initiates strong compression in the ice during surging, resulting in the development of prominent ice-cored hummocky moraine composed of glacifluvial sediment. Diagnostic surge landforms elsewhere on the foreland include thrust block and push moraines, overridden ice-cored thrust block moraines, crevasse squeeze ridges, long flutings, hummocky moraine and ice-cored, pitted outwash.

Results are presented from eight scaled centrifuge modelling experiments designed to investigate mass movement processes on thawing ice-rich slopes. Four pairs of simple planar slope models were constructed, one in each pair being of sufficient gradient to promote slope failure during soil thaw and the second having a gradient below the threshold for instability. Four frost susceptible soils were used, three were normally consolidated and had different clay contents (2%, 12% and 20%) and the fourth comprised the 20% clay soil, but was over consolidated prior to model testing. Modelling protocols included freezing from the surface downwards under an open hydraulic system, and thawing from the surface downwards under an enhanced gravitational field within the geotechnical centrifuge, thereby utilising scaling laws to simulate correct prototype self weight stresses during thaw. Slopes below the stability threshold gradient were subjected to between 2 and 4 cycles of freezing and thawing, simulating annual cycles. Those above the stability threshold were subjected to only one cycle, since they failed during the first thaw phase. Thermal conditions, pore water pressures, surface movements, and profiles of displacement are reported. Measured pore pressures are used in slope stability analyses based on a simple planar infinite slope model. Profiles of solifluction shear strain and mechanisms of slope failure are both shown to be sensitive to small changes in soil properties, particularly clay content and stress history. In all cases, pore pressures rose rapidly immediately following thaw, remained below the threshold for failure in low gradient models, but exceeding the threshold to trigger landslides on steeper slopes. Upward seepage of melt water away from the thaw front contributed to loss of shear strength. Mechanisms of slope failure differed between test soils, ranging from mudflow in non-cohesive silt to active layer detachment sliding in over consolidated silt–clay. During solifluction, shear strain was greatest at the surface in non-cohesive silt and decreased rapidly with depth, but in test soils containing clay, the zone of maximum shear strain was located lower in the displacement profiles.

Please click here to download the map associated with this article. A 1:30,000 scale map poster of the snout and proglacial landscape of the surging Icelandic glacier Bruarjokull, provides a spatial and temporal assessment of the geomorphic impacts of surging in glaciated terrains. Based upon aerial photography from 1998, 1999 and 2000, the map identifies the major landforms that are regarded as diagnostic of glacier surging when viewed in a landsystem framework; specifically, thrust block and push moraines, overridden thrust block moraines, zig-zag eskers, crevasse squeeze ridges, long utings, hummocky moraine and ice-cored, pitted outwash. This landscape imprint, when identi_ed in ancient glaciated terrains, can therefore be used as indicative of surge activity in palaeoglaciological reconstructions.

A toolbox for the automated calculation of glacier equilibrium-line altitudes (ELAs) using the Accumulation Area Ratio, Area-Altitude Balance Ratio, Area-Altitude and Kurowski methods is presented. These are the most commonly-used methods of ELA calculation in palaeo-glacier reconstructions. The toolbox has been coded in Python and runs in ArcGIS requiring only the reconstructed surface of the palaeo-glacier (a DEM) as input. Through fast and automatic calculation this toolbox simplifies the process of ELA determination and can successfully work both for a single glacier and for large datasets of multiple glaciers. We describe Equilibrium Line Altitude calculation methods for palaeoglaciers.We examine suitability of each method for different glacier types.We present a toolbox for automatic ELA calculation on AAR and AABR methods.Toolbox is coded in Python and runs in ArcGIS.Toolbox use and operation are described.

Many tidewater glaciers in Greenland are known to have undergone significant retreat during the last century following their Little Ice Age maxima. Where it is possible to reconstruct glacier change over this period, they provide excellent records for comparison to climate records, as well as calibration/validation for numerical models. These glacier change records therefore allow for tests of numerical models that seek to simulate tidewater glacier behaviour over multi-decadal to centennial timescales. Here we present a detailed record of behaviour from Kangiata Nunaata Sermia (KNS), SW Greenland, between 1859 and 2012, and compare it against available oceanographic and atmospheric temperature data between 1871 and 2012. We also use these records to evaluate the ability of a well-established one-dimensional flow-band model to replicate behaviour for the observation period. The record of terminus change demonstrates that KNS has advanced/retreated in phase with atmosphere and ocean climate anomalies averaged over multi-annual to decadal timescales. Results from an ensemble of model runs demonstrate that observed dynamics can be replicated. Model runs that provide a reasonable match to observations always require a significant atmospheric forcing component, but do not necessarily require an oceanic forcing component. Although the importance of oceanic forcing cannot be discounted, these results demonstrate that changes in atmospheric forcing are likely to be a primary driver of the terminus fluctuations of KNS from 1859 to 2012. We propose that the detail and length of the record presented makes KNS an ideal site for model validation exercises investigating links between climate, calving rates, and tidewater glacier dynamics.

Ground-penetrating radar (GPR) is becoming a commonly applied technique in geomorphology. However, its use in the study of subglacial bedforms has yet to be fully explored and exploited. This paper presents the results of a GPR feasibility study conducted on a drumlinized terrain in Cumbria, UK, where five drumlins were investigated using multiple radar antenna frequencies. The site was selected for the presence of nearby bedrock outcrops, suggesting a shallow drumlinized diamict–bedrock contact and a permeable lithology. Despite the clayey sediment and unfavourable weather conditions, a considerable penetration depth of ~12 m was achieved when using a 50 MHz antenna, with a separation of 1 m, trace spacing of 1 m and 128-fold vertical stack. Results indicate that the drumlinized diamict is in direct erosional contact with the bedrock. While the internal drumlin geometry is generally chaotic on the stoss side, evidence of layering dipping downflow at an angle greater than the drumlin surface profile was found on the lee side. The inter-drumlin areas comprise ~4 m of infill sediment that masks part of the original drumlin profile. Overall, this study indicates that GPR can be deployed successfully in the study of glacial bedform sedimentary architecture.

Five sites located on a bathymetric transect of the distal Demerara Rise were studied by ODP Leg 207. Albian sediments of essentially terrigenous nature (clay, siltstone, sandstone) are the oldest drilled stratigraphic levels and form apparently the top of the synrift sequence. They are overlain by Cenomanian to Santonian finely laminated black shales, rich in organic matter of marine origin, which accumulated on a thermally subsiding ramp. Early Campanian hiatuses are thought to be the result of final disjunction of Demerara Rise (South America) from Africa and the onset of deep water communication between the two Atlantic basins (south and central). The overlying Uppermost Cretaceous–Oligocene chalk includes rich and diversified calcareous plankton assemblages, as well as two radiolarian-rich intervals (Late Campanian and Middle Eocene). A complex erosional surface developed during the Late Oligocene–Early Miocene. Sedimentation was impeded since then on the intermediate and deep sites of Demerara Rise, possibly due to the action of deep submarine currents.

Basal ice samples were collected from ice exposures in a natural subglacial cavity beneath an outlet glacier of Oksfjordjokelen, North Norway. Sediment and cation (Ca 2+ , Mg 2+ , Na + , K + ) concentrations were then determined, and indicate stacking of basal ice units producing a repeat pattern of 'clean firnification ice' overlying sediment-rich ice. All measured cations show correlation with sediment concentration indicating weathering reactions to be the dominant contributor of cations. Regressions of specific sediment surface area per unit volume with cation concentration are performed and used to predict cation concentrations. These predicted values provide an indication of cation relocation within the basal ice sequence. The results suggest limited melting and refreezing resulting in the relocation of predominantly monovalent cations downward through the profile. Exchange of cations into solution during the melting of sediment-rich ice samples has previously been suggested as a source of error in such investigations. Analyses of sediment-free regelation ice spicules formed at the bed show cation concentrations above firnification ice levels and comparable, in many instances, to the basal ice samples.

Tidewater glaciers in Greenland experienced widespread retreat during the last century. Information on their behaviour prior to this is often poorly constrained due to lack of observations, while determining the drivers prior to instrumental records is also problematic. Here we present a record of the dynamics of Kangiata Nunaata Sermia (KNS), southwest Greenland, from its Little Ice Age maximum (LIAmax) to 1859 – the period before continuous air temperature observations began at Nuuk in 1866. Using glacial geomorphology, historical accounts, photographs and GIS analyses, we provide evidence KNS was at its LIAmax by 1761, had retreated by ~5 km by 1808 and a further 7 km by 1859. This predates retreat at Jakobshavn Isbræ by 43–113 years, demonstrating the asynchroneity of tidewater glacier terminus response following the LIA. We use a one-dimensional flowband model to determine the relative sensitivity of KNS to atmospheric and oceanic climate forcing. Results demonstrate that terminus forcing rather than surface mass balance drove the retreat. Modelled glacier sensitivity to submarine melt rates is also insufficient to explain the retreat observed. However, moderate increases in crevasse water depth, driving an increase in calving, are capable of causing terminus retreat of the observed magnitude and timing.

The Quaternary glacial history of the Tweedsmuir Hills, Central Southern Uplands, Scotland, has received little attention since the 1980s, with earlier studies focussing on single lines of geomorphic evidence in isolated valleys. This study presents the first systematic glacial geomorphological assessment of the region, covering approximately 300 km2 with the map designed to be presented at A0. Mapping from remotely sensed imagery and field investigation reveal a large number of moraines and meltwater channels, both within valleys and occasionally extending to the plateau, alongside a range of peri- and para-glacial features, including solifluction lobes, alluvial fans, debris cones, river terraces and rock slope failures. Aspects of the mapped geomorphology are consistent with plateau icefield landsystems mapped elsewhere in Britain and this will hopefully form the basis for palaeoglaciological reconstructions which will improve our understanding of the extent and dynamics of former ice masses in the region.

A detailed study of a proglacial bedrock site and a subglacial cavity of an outlet of Øksfjordjøkelen, Norway, is presented together with observations from the foreland of Konowbreen, Spitsbergen. Striation directions and subglacial observations indicate that local ice-flow paths were highly variable, deviating at angles of approximately 90° from the main ice-flow direction. Stepped bedrock topography appears conducive to the production of highly variable ice-flow paths, because the high bed roughness creates a locally variable stress regime within the ice, including low-pressure, lee-side areas into which ice can flow. If ice flow is sustained along a specific path and the ice contains debris, then abrasion should produce an erosional bedform. Models are proposed whereby locally variable ice-flow patterns could produce erosional bedforms, which would be described as p-forms, purely through mechanical abrasion.

Here we compare scaled centrifuge modelling of gelifluction processes with earlier full-scale physical modelling experiments. The objective is to assess the validity of the centrifuge technique for cryogenic slope-process investigations. Centrifuge modelling allows correct self-weight stresses to be generated within a small-scale physical model by placing it in an elevated gravitational field. This paper describes an experiment in which a scaled frozen-slope model was thawed in a gravitational field equivalent to ten gravities. After four cycles of thawing, during which soil temperatures, pore pressures, thaw settlement and downslope soil displacements were continuously monitored, a series of marker columns were excavated to reveal profiles of soil movement. Comparison of these data with those from an earlier full-scale laboratory simulation experiment indicates that thaw-related gelifluction was successfully reproduced during centrifuge modelling. It is concluded that rates of soil shear strain during gelifluction were not time-dependent? since soil displacements in the centrifuge tests were of a similar magnitude to or greater than those observed in the much longer-duration full-scale simulation. This suggests that no transition occurred in soil behaviour from a frictional plastic to a true viscous fluid during the period of high moisture contents immediately following thaw.

Plateau icefields occur commonly in glacierized areas and not uncommonly in glaciated mountains. We report on a glacierized area of plateaux and valleys centred round the highest peak Jiehkkevárri (1833 m) in the maritime Lyngen Alps, North Norway. Some valley glaciers are fed by steep, narrow plateau glacier outlets and/or ice avalanching from the plateaux over precipitous cliffs. Plateaux must therefore be considered as “contributing areas”, if they supply ice to valley systems below. Equilibrium line altitudes (ELAs) are calculated for the valley glaciers during the Little Ice Age (LIA), accounting for both input and no input of ice from plateaux above. The results show that ELAs may be at significantly higher altitudes when plateau/x are contributing ice mass. The response of plateau glaciers to climate amelioration since the end of the LIA is somewhat different to that of valley glaciers, which appear to be retreating markedly. These findings have significant implications for the interpretation of moraine systems, glacier dynamics, the construction and reconstruction of present and former ELAs, and palaeoclimates in glacierized and glaciated mountain plateau areas.