Orals: Wed, 6 May, 10:45–15:45 | Room 1.34
The possibility of a continuous, kilometre-thick Arctic Ocean ice shelf in the geological past has long intrigued scientists. Yet, fundamental questions surrounding the architecture, timing, and oceanic and climatic consequences of such an ice shelf remain unresolved. A pan-Arctic glaciation model has been inferred primarily from glacial landforms identified on seafloor bathymetric highs and continental shelves, as well as from geochemical proxies found in marine sediment cores.
Subsequent chronological analyses of sediment cores from these eroded regions have suggested that this pan-Arctic Ocean ice shelf developed during Marine Isotope Stage (MIS) 6, approximately 140,000 to 160,000 years ago. In contrast, more recent evidence from the eastern Fram Strait suggests the persistence of marginal sea-ice conditions and recurrent phytoplankton spring blooms across several glacial-interglacial cycles over the last 750,000 years. Nevertheless, an exception appears to occur during MIS 16, a glacial interval between ~670,000 and 620,000 years ago that remains relatively understudied in the Arctic Ocean. During this period, biomarkers indicative of sea ice and primary productivity, and planktic foraminifera are either absent or occur in extremely low concentrations in sediment cores from both the Arctic-Atlantic Gateway and the Nordic Seas. Although the full spatial extent of glacial ice during MIS 16 remains uncertain, it is thought to have rivalled that of the Last Glacial Maximum (LGM) in terms of ice volume. In this study, we present new geomorphological evidence supported by sediment core chronologies for significant Greenland ice sheet expansion during the end of the Mid Pleistocene Transitoin (MPT). The discovery of record-deep ploughmarks, in combination with a grounding zone wedge (GZW) at approximately 800 meters water depth on the Morris Jesup Rise, northeast Greenland, suggests that the Greenland/Innuitian Ice Sheet grew sufficiently to form an ice shelf extending into the central Arctic Ocean – implying an "Antarctification" of Greenland during this extreme glacial phase.
How to cite: Knies, J., Patton, H., Giertzuch, P.-L., and De Schepper, S. and the i2B Arctic Ocean Expedition 2025 Science Party: New evidence for Greenland ice sheet expansion beyond its present shelf break during the Mid-Pleistocene Transition , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3417, https://doi.org/10.5194/egusphere-egu26-3417, 2026.
Many tens of ice rises exist at the marine margins of the Antarctic Ice Sheet. Isle-type ice rises in particular are those where an ice shelf is pinned to an underlying submarine bank. Recent and ongoing studies show that Ross Bank, on the middle continental shelf of central Ross Sea, was the former site of an important Ross Ice Shelf ice rise during the advance and retreat of the West Antarctic Ice Sheet (WAIS) in the last glacial cycle. Ross Bank is a broad and anomalously shallow water platform whose crest rises to 150 m water depth. Despite its importance as a buttressing site, little is known about how, when and why such submarine banks formed. Here, we use a grid of seismic data acquired during expedition NBP2301/2 to reconstruct how Ross Bank morphology evolved. Our seismic-based correlations and mapping show that Ross Bank overlies the western flank of the Central High, a large basement horst created during the rifting of Ross Sea. Seismic correlation to lithologic and chronologic control at IODP expedition 374 sites U1521 and U1522 indicates that thick grounding zone wedges were deposited at the site of Ross Bank during the early Miocene. Intermittent advance of erosive ice streams deeply eroded those wedges and produced approximately 400 meters of relief at Ross Bank prior to the middle Miocene. The complete absence of middle Miocene strata at Ross Bank suggests significant intervals of subglacial erosion associated with glacial stages of the Middle Miocene Shift. In the time since, relatively minor aggradation on the crest of Ross Bank occurred during parts of the late Miocene, Pliocene and Pleistocene. Our analyses make the case that a shallow submarine area existed at Ross Bank since the middle Miocene. The bank would have been the site of ice rises that influenced the advance and retreat of the WAIS in central Ross Sea over the past 14 Myr.
How to cite: Weber, W. and Bart, P.: The case for Ross Bank ice rises since the middle Miocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15366, https://doi.org/10.5194/egusphere-egu26-15366, 2026.
The East Antarctic Ice Sheet (EAIS) contribution for future global sea level rise and climate change is source of uncertainty, and it appears essential to reconstruct its past fluctuations. Previous works reveal geomorphic and chronological evidence that the ice sheet extended to the continental shelf break during LGM (Last Glacial Maximum; ~20 ka). However, still little is known about its response to the major climate and oceanic transitions following the LGM. In this study, we reconstruct (1) a chronology of ice-sheet fluctuations, (2) ice-sheet past erosion efficiency and (3) ice-sheet thinning during the late-Pleistocene to Holocene time-period, in Terre Adélie (East Antarctica). Newly obtained exposure ages for coupled 10Be-26Al support a scenario of glacial fluctuations at global, regional and local scales. Inland nunataks reveal some long-term exposure with apparent exposure ages ~150 ka, while coastal areas record a past ice-sheet thinning after ~20 ka. Ages measured on erratic boulders of Archipel Pointe Géologie record the final episode of a regional deglaciation around ~15 ka. Slightly inland, in Lacroix sector, erratic boulders record a more recent local ice-sheet oscillations around ~1.5 ka. In contrast, exposure ages obtained on glacially-polished bedrock are characterised by spatially-variable inheritance, suggesting that past ice sheet retreat history is characterised by variations in erosion efficiency. Finally, our results also suggest some potential previous geomorphological inheritance from the hot Pliocene phase.
How to cite: Rolland, Y., Péan, M., Valla, P., Duclaux, G., Braucher, R., Jomelli, V., Favier, V., Schimmelpfennig, I., Crosta, X., Etourneau, J., and Louis, M.: Reconstructing Plio-Quaternary fluctuations of the East Antarctic Ice Sheet in Terre Adélie inferred from cosmogenic nuclides (10Be-26Al) in glacially-polished bedrock, morainic boulders and nunataks , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10117, https://doi.org/10.5194/egusphere-egu26-10117, 2026.
Reconstructions of Antarctica's past ice-sheet evolution remain poorly constrained due to sparse, spatially discontinuous proxies, limiting accurate projections of its future sea-level contribution. Here we present a novel isochronally-constrained reconstruction of Dronning Maud Land (DML), East Antarctica spanning the last interglacial-glacial cycle (~130 kyr), integrating extensive radar-derived internal reflection horizons (IRHs) with PISM ice-sheet simulations.
IRHs preserve continuous records of past accumulation, flow, and basal conditions, providing unprecedented spatiotemporal constraints for model validation. Our ensemble simulations indicate that DML’s sea-level potential change between interglacial and glacial states is comparable to, and likely larger than, the contribution of all modern mountain glaciers, and show that variations in geothermal flux alone can substantially alter sea-level projections. These results provide physical modelling context of East Antarctica's ice history, reveal DML's role in Last Interglacial sea-level rise, and highlight persistent parameterization uncertainties limiting future projections.
How to cite: Višnjević, V., Bodart, J., Hermant, A., Spezia, E., Wirths, C., and Sutter, J.: Modelling the evolution of Dronning Maud Land, Antarctica across the last interglacial-glacial cycle – insights from isochrone modelling., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11727, https://doi.org/10.5194/egusphere-egu26-11727, 2026.
GLAC3 is the first history matching of every last glacial cycle ice sheet. It therefore includes North American, Greenlandic, Icelandic,
Eurasian, Tibetan, Patagonian, and Antarctic components. Instead of determining a non-robust "optimal" chronology, history matching aims
to "bound reality" with robust assessment of both proxy data and model (both parametric and structural) uncertainties. For the four major ice
sheets, this entails Bayesian artificial neural network emulation of the glaciological model predictions to enable adequate Markov Chain
Monte Carlo sampling of chronologies. The history matching is against a large set of geophysical (such as relative sea level and marine
limit), geological (cosmogenic exposure and C14 ages), and glaciological (such as present-day ice surface velocity) constraints.
Aside from being a product of history matching, GLAC3 has two additional unique features. Firstly, it is the only available
deglacial, let alone full glacial cycle, global set of chronologies from glaciological modelling, using the Glacial Systems Model
(GSM) with hybrid shallow ice and shallow shelf ice dynamic. This enables physical resolution of ice sheets, ice streams, ice shelves,
and grounding line migration. As such, GLAC3 is subject to glaciological constraints such as borehole temperature profiles that
non-glaciological reconstructions can't resolve. Secondly, the glaciologically modelling is self-consistently coupled with full
visco-elastic glacio-isostatic adjustment enabling joint history matching of ice history and regional earth viscosity.
The presentation will focus on the relative phasing of each ice sheet, rates of mass gain and loss, and rates of ice margin migration. This
will be compared against both far-field relative sea level records as well as the results of fully coupled ice and climate modelling of the
last glacial cycle with LCice (LOVECLIM + GSM).
How to cite: Tarasov, L., Dalton, A., Dyke, A., Geng, M., Goffin, A., Hughes, A., Lecavalier, B., Mangerud, J., Milne, G., Svendsen, J.-I., and Woodroffe, S.: GLAC3 rates and phasing: the first joint history matching of global last glacial cycle ice sheet evolution and regional earth rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15518, https://doi.org/10.5194/egusphere-egu26-15518, 2026.
Coupled climate-ice-sheet modelling provides critical insights into the mechanisms underlying ice-sheet-climate feedback. These processes have strong implications for past and future climate change events, yet modelling efforts remain constrained by uncertainties in key model parameters. To address this limitation, we rely on comparisons between model outputs and available records of past ice sheets. Historically, this involved matching simulated ice sheets to reconstructed extent and volume derived from a range of geomorphological and sea level change data. Although these metrics are useful to validate ice sheet geometry and volume, they only provide limited information on ice sheet dynamics. New methods, which compare the footprint of reconstructed and simulated palaeo-ice streams, offer promising ways to incorporate a dynamical dimension into model calibration (Ely et al., 2024, Journal of Quaternary Science).
In this project, we catalogue the distinct dynamical configurations observed in an ensemble of coupled climate-ice-sheet simulations of the Last Glacial Maximum (LGM, 21,000 years ago). This ensemble includes 124 equilibrium simulations generated using the coupled atmosphere-ice-sheet model FAMOUS-BISICLES, with variation applied to 12 model parameters representing ice dynamics, albedo and climate feedbacks (Patterson et al., 2025, EGUsphere). The ice sheet dynamics not only assess the model’s ability to replicate the LGM reconstructions of the Laurentide ice streams (Margold et al. 2018, Quaternary Science Reviews), but they also inform the sensitivity of the simulated ice sheets to climate forcing.
Plausible simulations of the North American ice sheets in terms of volume and extent can be obtained across various regions of the parameters space, resulting in significant discrepancies in potential ice streaming patterns. Surface Mass Balance (SMB) is the main factor behind these changes in dynamical configurations: simulations with low accumulation tend to produce less numerous and intense ice streams, whereas high accumulation is associated with more vigorous ice streaming. In addition, the parametrisation of the ice dynamics influences the location and consistency of the ice streams, as well as the ability of the ice sheet to respond to climate change events.
We find that simulations with relatively high SMB and ice dynamics parameters that enable fast-flowing and well-defined ice streams best match estimates of Last Glacial Maximum North American ice sheet extent, volume and ice stream location. Conversely, high friction coefficients and porous subglacial till, or low resolution of the ice sheet margins and the bedrock topography, result in ice stream patterns that are inconsistent with reconstructions and less responsive to climate forcing. This work demonstrates the relevance of comparison between reconstructions of past ice streams and model simulations to provide strong constraints on dynamical ice sheet models and ice sheet sensitivity to climate changes.
How to cite: Romé, Y., Gregoire, L., Gandy, N., Patterson, V., and Ely, J.: Using reconstructed ice streams to calibrate a coupled climate-ice-sheet model of the North American Ice Sheet Complex during the Last Glacial Maximum , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20495, https://doi.org/10.5194/egusphere-egu26-20495, 2026.
The nature of the subglacial environment is a key part of glacier dynamics. Studies from modern glaciers have revealed there is a continuum in subglacial fluvial behaviour associated with a soft-bed, from channelised to distributed. How is this continuum preserved within the sedimentary record and what is the relationship between fluvioglacial sediments and flutes? Classically eskers are associated with channelized drainage, whilst the sedimentary remains of ‘canals’, ‘subglacial meltwater corridors’ and murtoos may reflect the distributed system. Stratified lenses within till are common and have been given numerous interpretations, either reflecting preglacial sediments that have been incorporated into the till by deformation, or penecontemporaneous sedimentation with the till. We use data from instrumented modern glaciers and Quaternary sections to illustrate the nature and rate of subglacial behaviour associated with soft-bedded glaciers.
How to cite: Hart, J. and Martinez, K.: Soft-bed distributed subglacial sedimentology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9543, https://doi.org/10.5194/egusphere-egu26-9543, 2026.
Understanding temperature variability during the Holocene is critical for constraining baselines of natural climate variability. Temperate mountain glacier extent is limited most significantly by summer air temperature, thus geological records of past glacier length changes represent a useful proxy for this climatic variable. Iceland’s maritime glaciers with their high sensitivity to temperature and precipitation changes serve as robust indicators of climate variability in the North Atlantic region. Previous reconstructions of Iceland’s Holocene glacier and climate history have relied primarily on marine sediment cores, terrestrial geomorphological evidence, and glaciological modelling. These proxies highlight a correlation between glacier fluctuations and regional climate variability and suggest notable glacier retreats during early and mid-Holocene warm periods.
Here, we present cosmogenic chlorine-36 measurements from four outlet glaciers of the Vatnajöküll ice cap in Iceland that test and further constrain the occurrence of past glacier minima during the Holocene. Unlike the more commonly used method of cosmogenic surface exposure dating of moraines, which constrains the timing of past glacier advances, our application targets the remnant cosmogenic signals of prehistoric exposure events preserved in freshly exposed proglacial surfaces. Our data thus tests for the occurrence and constrains the duration of past glacier retreat events and, thereby, warmer times during the Holocene. Our results support the hypothesis that Icelandic glaciers were smaller than present for several millennia during the Holocene and when combined with existing datasets of Icelandic climate, our new results allow us to reconstruct both glacier advance and retreat through the Holocene.
How to cite: de Campo, A., Eaves, S., Norton, K., Wilcken, K., Fülöp, R.-H., Simon, K., Silvia, C., Lane, T., and Jackson, M.: Cosmogenic chlorine-36 constraints on Holocene glacier change in Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1360, https://doi.org/10.5194/egusphere-egu26-1360, 2026.
Reconstructing the precise timing and geometry of the British-Irish Ice Sheet (BIIS) is critical for understanding the sensitivity of the North Atlantic climate system to abrupt perturbations. We present preliminary results from a cosmogenic beryllium-10 (10Be) surface-exposure chronology of glacial deposits in the Gaddagh valley, situated on the northern flank of the McGillycuddy’s Reeks, southwest Ireland. Our geomorphological and chronological transect reveals a detailed history of deglaciation and ice-margin fluctuations since the Late Pleistocene.
Initial results indicate that high-elevation areas (300–350 m asl) adjacent to the main valley were ice-free by ~28 ka (n=2), suggesting an earlier onset of local thinning than previously modelled. The prominent "Hag’s Tooth Moraine”, the primary geomorphological feature in the valley, appears to represent a culmination during the Last Glacial Maximum (LGM). Following this peak, the deposition of a barely preserved subdued moraine impounded Loch Callee at ~19 ka (n=3), marking a significant phase of ice retreat at the onset of Termination 1. The final pulse of glacial activity is recorded 200 m higher in the catchment by a complex of five latero-frontal moraines. These landforms mark the former extent of a small cirque glacier, with the final abandonment of these positions occurring at ~12.7 ka (n=3).
Thus far, our findings implicate the following. First, the data do not support a complete ice cover over the McGillycuddy’s Reeks during the LGM as previously proposed; instead, we suggest that ice was topographically restricted to the main valleys, with the front of the Gaddah glacier not below 150 m asl. Second, our chronology indicates that terminal deglaciation occurred during a period traditionally associated with relatively cold climate conditions. This pattern of glacier recession during inferred year-round cold climate aligns with recent 10Be chronologies from Scotland (Bromley et al., 2018, 2023), central East Greenland (Kelly et al., 2025), southernmost Greenland (Carlson et al., 2021) and Norway (Putnam et al., 2023; Wittmeier et al., 2020), which demonstrate glacier shrinkage during the Younger Dryas. These results contribute to the ongoing discussion about glacier extension in the area and the evolving paradigm of North Atlantic climate dynamics, emphasizing the role of summer temperature as the primary driver of glacial mass balance during millennial-scale stadials.
How to cite: Rodriguez, P. and Bromley, G.: Lateglacial deglaciation of the McGillycuddy’s Reeks, SW Ireland through 10Be surface-exposure dating of glacial deposits in the Gaddah Valley: Implications for late glacial climate variability., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15730, https://doi.org/10.5194/egusphere-egu26-15730, 2026.
The west-central Keewatin region of northern Canada preserves a rich record of former ice sheets and their impact on the landscape. The diverse assemblage of glacial landforms in the region reflects spatial variations in glacial modification driven by changes in basal thermal regime, subglacial hydrology, and ice-flow dynamics, all of which are key to reconstructing the history and behaviour of palaeo-ice sheets. Resolving how these landforms relate to changes in basal regime and glacial modification requires integrated datasets such as geomorphological mapping and to provide the robust reconstructions needed for climate and ice-sheet models.
Our work aims to provide both a qualitative and quantitative assessment of glacial landscape modification in the west-central Keewatin region of the Northwest Territories and mainland Nunavut using two independent proxies: geomorphic mapping and cosmogenic nuclide concentrations. We used the ArcticDEM and Landsat 8 imagery to remotely map This new inventory of landforms, integrated with existing mapping, provides a qualitative assessment of glacial landsystems and landscape modification across the Keewatin region. As a quantitative proxy for glacial modification from the last glacial period(s), we collected 10 bedrock and 7 boulder samples for cosmogenic 10Be measurement along a north-south transect east of Dubawnt Lake, Nunavut. The sample transect was informed by glacial geomorphic mapping and was selected to test field-based predictions of the degree of landscape modification from the previous glaciation(s). The northern portion of the transect contains high concentrations of streamlined landforms associated with the onset zone of the Dubawnt Ice stream, inferred to be a region of high glacial modification. In contrast, the southern end of the transect contains lower concentrations of streamlined features, flow sets with contrasting orientations, and cross-cutting striations, suggesting a higher degree of landscape preservation during the last glaciation(s). Preliminary 10Be results broadly confirm our initial assessment of glacial modification along our transect, revealing slightly higher concentrations of 10Be in the south (less modification) and decreasing 10Be concentrations towards the north (more modification). Both bedrock and boulder samples follow this trend, however, our results show that in both low- and high-modification landsystems, some samples retain significant nuclide inheritance, including some boulders which suggests transport from a less modified landscape. Combining qualitative and quantitative approaches to evaluate glacial modification associated with specific landform assemblages informs our understanding of the basal thermal conditions of palaeo-ice sheets, the distribution of which informs our understanding of ice sheet evolution through space and time. Furthermore, the identification of streamlined features into palaeo-flow sets supports potential mineral exploration by helping to determine glacial transport directions and dispersal patterns. However, our results show the concentrations of cosmogenic nuclides vary within individual landsystems, suggesting that glacial modification varied through time and can be influenced by multiple factors (e.g., subglacial thermal conditions, topography, glacio-isostatic adjustment, lake development) that remain to be quantified.
How to cite: Crowell, C., Kelley, S., Brouard, E., Campbell, J., and Gosse, J.: Using digital mapping and cosmogenic 10Be to assess glacial landscape modification in west-central Keewatin, Arctic Canada , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-822, https://doi.org/10.5194/egusphere-egu26-822, 2026.
Fjord landscapes along the margins of past and present ice sheets testify to the significant long-term erosive power of large outlet glaciers. Yet, our understanding of the rates and processes of subglacial erosion and sediment transport beneath ice sheets remains incomplete. Quantifying these processes is crucial for reconstructing past ice dynamics, estimating sediment fluxes to the ocean, and understanding long-term landscape evolution.
Greenland’s narrow, steep-sided fjords act as natural sediment traps, preserving erosion products delivered by large outlet glaciers during deglaciation. These fjord sediments constitute a valuable constraint on past erosion rates and glacial sediment fluxes when combined with ice catchment areas and retreat histories in a source-to-sink framework. However, most Greenlandic fjords remain unmapped in terms of sediment thickness because sediment cores rarely penetrate deeply and seismic data acquisition is sparse. In contrast, accurate bathymetric data are increasingly available for many fjords. We use a geomorphological approach to estimate sediment infill volumes based on fjord cross-sectional profiles, where deviations from the expected U-shape and the slope of the sidewalls are used to infer sediment thickness.
We quantify fjord infill volumes for several fjords and use these to estimate average catchment-wide erosion rates. The timing of deposition (starting when the ice retreated into the fjord) is constrained by available deglaciation models. To further explore the temporal and spatial variability of subglacial erosion, we employ a coupled ice-flow and erosion model (iSOSIA), driven by paleoclimate forcing, to simulate erosion beneath marine-terminating outlet glaciers during the last deglaciation (~21–0 ka BP). Modeled sediment outputs are compared with our estimates of sediment volumes and accumulation rates from sediment cores to calibrate the model erosion parameters.
Our results indicate that average deglacial erosion rates are largely independent of catchment size but vary significantly through time and space within ice-sheet catchments. Rates can exceed 10 mm yr⁻¹ for topographically steered, fast-flowing outlet glaciers, while much lower rates (<0.1 mm yr⁻¹) occur in slower-flowing interior regions with slow-moving ice. Quantifying and linking offshore sediment volumes with numerical modeling provides an opportunity to constrain subglacial erosion rates, sediment transport and ice-sheet reconstructions. This work demonstrates the value of integrating glaciological modeling with marine sediment archives to refine erosion estimates and improve predictions of future sediment fluxes under continued ice-sheet retreat.
How to cite: Damsgård, J., Brand, C., Jungdal-Olesen, G., and Pedersen, V.: Constraining subglacial erosion in Greenland using estimates of fjord sediment volumes and ice-flow modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16822, https://doi.org/10.5194/egusphere-egu26-16822, 2026.
Glacially derived, marine sediments preserve a record of the timing, extent, and dynamics of shelf glaciation. In addition, these deposits can provide constraints on glacial erosion rates and offer insights into landscape evolution. However, in Greenland, the total offshore volume of glacially derived sediments remains poorly constrained due to an uneven distribution of offshore seismic surveys and a lack of dating constraints. To address this, we present a first quantification of Quaternary glacial sediment thicknesses around Greenland, combining interpretations of available marine seismic data with age constraints where scientific boreholes are available and a neural network approach. We train the neural network using the seismic-derived thicknesses, along with several parameters related to glacial and geomorphological features. This approach allows us to predict Quaternary sediment thicknesses in regions with sparse data coverage, thereby constraining the total volumes of deposition. Our estimates reveal regional variations in glacial deposition volumes and sediment thicknesses around Greenland. On the southern and parts of the northern Greenlandic continental slope, Quaternary sediments are thin, whereas in west and east Greenland, larger sediment deposits have led to a greater shelf progradation throughout the Quaternary. These patterns demonstrate a diverse influence of (paleo-)climatic, oceanographic, and orographic processes on glacial dynamics and the source-to-sink sediment transport. Finally, we compare our estimates of Quaternary offshore deposition with estimates of onshore glacial erosion inferred from paleo-topographic reconstructions and erosion potentials of the present ice sheet, based on ice sliding velocities. This provides insights into the temporal and spatial variability of erosion around Greenland, advancing our understanding of the long-term landscape evolution in glaciated regions.
How to cite: Brand, C., Elger, J., Andresen, K. J., Hansen, T. M., Poulsen, V. S., Pérez, L. F., Fox, M., Böttner, C., Knutz, P., Damsgård, J. F., and Pedersen, V. K.: From source to sink: Quantifying Quaternary erosion from offshore deposits associated with the Greenland Ice Sheet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12234, https://doi.org/10.5194/egusphere-egu26-12234, 2026.
The onset and potentially time-transgressive latitudinal development of Northern Hemisphere glaciations during the Plio-Quaternary represents a key component of global late Cenozoic climate dynamics. The timing of the earliest Alpine glaciations has been debated since the pioneering work of A. Penck and E. Brückner at the beginning of the 20th century. Over the past three decades, cosmogenic nuclide burial dating has provided absolute ages on glacial and fluvioglacial sedimentary deposits in the Alpine forelands, progressively refining the chronology of early glaciations as methodological advances have emerged and as the number of analyzed samples has increased. Recent syntheses from the northern Alpine foreland (Deckenschotter) and the Ivrea amphitheater indicate that piedmont glacier lobes developed between 1.2 and 0.8 Ma, suggesting that the first extensive Alpine-wide glaciations occurred during the Mid-Pleistocene Transition. However, reconstructions based solely on surface deposits are strongly affected by preservation biases, as repeated glaciations may have eroded older sedimentary archives. As a result, Early Pleistocene surface records may have been largely removed by subsequent, more extensive glaciations.
Karst systems provide an alternative archive for early glaciations. During glacial periods, glaciers in contact with karst conduits inject detrital material (allochthonous or autochthonous) into subsurface voids, where sediments can be preserved for several million years. These buried deposits can be dated using in situ cosmogenic nuclides such as 26Al–10Be in quartz. Prior to this study, very few geochronological and sedimentological data existed for such ancient glacio-karst deposits (i.e. Early Pleistocene). New 26Al–10Be burial ages obtained from 20 detrital endokarst sediment samples (sands and pebbles) in the western to central Alps (Vercors, Chartreuse, Haut-Giffre and Bernese Alps), together with a synthesis of existing dating in the central Alps, allow the first spatio-temporal reconstruction of glacial sediment injections into the Alpine karst. Consistent with surface records, the burial ages reveal major glacial sediment injections into the karst around 0.8 Ma, at the end of the Mid-Pleistocene Transition. However, the data also point to a much earlier phase of widespread injections around 2 Ma. These early injections occurred both in high-elevation (>2500 m) headwater karst systems and in peripheral karst networks bordering the major Alpine valleys along the mountain front, demonstrating that widespread early glaciations affected the entire Alpine chain around 2 Ma. Because Alpine valleys were less deeply incised during the Early Pleistocene, glacier geometries differed significantly from those of Middle and Late Pleistocene glaciations, with thinner and potentially less extensive ice bodies. These earliest Alpine glaciations are contemporaneous with major advances of the Eurasian and North American ice sheets, consistent with extensive Northern Hemisphere glaciations at that time, predating the intensification of glaciations initiated at the Mid-Pleistocene Transition. Ultimately, this study highlights the potential of mountain karst systems as long-term archives for reconstructing Quaternary climate transitions.
How to cite: Mai Yung Sen, V., Valla, P., Jaillet, S., Robert, X., Rolland, Y., Borreguero, M., Carcaillet, J., Pons-Branchu, E., Crouzet, C., and Bruguier, O.: Early Alpine glaciations at ca. 2 Ma revealed by 26Al–10Be burial dating of endokarst sediments in the western–central European Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-461, https://doi.org/10.5194/egusphere-egu26-461, 2026.
Reconstructions of Northern Hemisphere ice sheets throughout the Quaternary are central to interpreting past variations in sea level, ocean-atmospheric circulation, and climate. Yet, terrestrial records of the earliest glaciations are fragmentary and anchored principally to relative chronostratigraphic frameworks, limiting direct comparison with more continuous marine archives. Here, we present new dating and sedimentary provenance constraints, motivating reassessment of the early history of the Eurasian Ice Sheet (EIS) and its role within the evolving Pleistocene climate system.
Cosmogenic 26Al-10Be burial dating of key glacigenic deposits from northwest and central Europe reveals that extensive EIS advances occurred repeatedly during the Early Pleistocene, beginning as early as ~2.35 million years ago (Ma), and substantially predating the traditionally inferred onset of lowland glaciation during marine isotope stages (MIS) 16–12 (~0.65–0.45 Ma). Detrital zircon U-Pb fingerprinting of these deposits indicates that successive EIS advances transported sediment from the Fennoscandian Shield into the North Sea Basin and the North European Plain, implying that ice flow pathways through the Baltic Depression were established already in the Early Pleistocene and the Baltic (Eridanos) River System had terminated by at least ~1.5 Ma.
Our revised chronologies highlight that the most extensive EIS configurations formed prior to the Middle Pleistocene Transition, and within the context of apparent low-amplitude glacial cycles of the ‘41-kyr world.’ When integrated with independent geochronologic evidence from North America, these findings (within uncertainties) point to broadly synchronous Early–Middle Pleistocene expansions of the major Northern Hemisphere ice sheets. Such early attainment of continental-scale ice sheets may help to reconcile available terrestrial evidence with emerging reconstructions of significant glacial sea-level lowstands prior to the dominance of ~100-thousand year glacial cycles.
More generally, this synthesis calls for re-examination of long-standing European Quaternary stratigraphic frameworks and suggests that Eurasian glaciation may have played an important role in reorganizing continental drainage, modulating freshwater delivery to the North Atlantic, and influencing ocean-atmospheric circulation throughout the Early–Middle Pleistocene.
How to cite: Wagner, K., Ylä-Mella, L., Margold, M., Faurschou Knudsen, M., and D. Jansen, J.: Two million years of the Eurasian Ice Sheet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14737, https://doi.org/10.5194/egusphere-egu26-14737, 2026.
For over 100 years, from school textbook to research, glacially sculpted landforms called drumlins have been considered asymmetrical, tear-drop shaped. Recent work has securely demonstrated that, in the absence of bedrock, this asymmetry is measurable but tiny – non-existent to visual inspection. High-resolution DEMs and a novel application of statistics to flow-sets demonstrate that a well-studied a Swedish site exhibits a transition from asymmetrical bedrock-cored drumlins to symmetrical till-cored ones within just a few 10s of m of till. We believe that this is the first direct observational constraint upon the thickness of till required to effectively decouple flowing ice from rough bedrock topography. Understanding where till lubrication has the potential to speed up ice flow has large implications for modelling current ice sheets and Antarctic deglaciation, so we are hoping for ideas of how to best assess this last part.
How to cite: Hillier, J. K., Smith, M., Dowling, T., Spagnolo, M., Maclachlan, J., and Martin, C.: Symmetrical till-cored drumlins highlight where past ice sheets flowed faster, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2751, https://doi.org/10.5194/egusphere-egu26-2751, 2026.
During the Late Palaeozoic Ice Age (LPIA; ~360–260 Ma), southern Africa formed part of Gondwana and experienced repeated episodes of continental glaciation. These glacial events left an extensive sedimentological and geomorphological record. In several regions, modern topography partially reflects this inherited glacial relief, providing rare insights into pre-Quaternary ice-sheet dynamics, basal processes, and ice–substrate interactions. Despite their scientific importance, many LPIA glacial pavements in southern Africa remain poorly documented and understudied. Numerous key outcrops are increasingly threatened by natural erosion, flooding, agricultural practices, and industrial development. In addition, access is often restricted because many pavements occur on private farmland or in remote areas, limiting systematic field investigation. To date, most known glacial pavements have not been digitally mapped or analysed at high spatial resolution.
Here we apply integrated aerial and close-range photogrammetry, combined with detailed sedimentological analysis, to document seven representative Late Palaeozoic glacial outcrops in the Northern Cape Region in South Africa. High-resolution digital outcrop models are complemented by field-based sedimentological observations. Together, these approaches provide a robust framework for interpreting glacial dynamics and depositional environments. The resulting digital and sedimentological datasets form a reproducible archive that supports quantitative analysis, virtual access, and long-term preservation of vulnerable geological heritage sites. Our results demonstrate the potential of combining digital documentation with in-depth sedimentological analysis to advance the study of ancient glacial landscapes and to preserve critical pre-Quaternary cryospheric records for future research.
How to cite: Wohlschlägl, R., Mejías Osorio, P., Busfield, M., Haberer, P., Smith, A., and Le Heron, D.: Chasing pavements: New insights from Late Palaeozoic glacial outcrops in South Africa, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4936, https://doi.org/10.5194/egusphere-egu26-4936, 2026.
The Quaternary glacial history of Siberia is uncertain, with several competing reconstructions existing in the published literature. This uncertainty is driven by seemingly incomplete and inconsistent records of glacial geomorphology and a patchy record of chronometric data. To address this, we have compiled previously published glacial geomorphological maps and chronometric data to establish what empirical data for former glaciations exist across Siberia. We also use these data to test the currently published glacial reconstructions to determine which, if any, reconstruction can be best underpinned by current empirical evidence. In turn, we will attempt to reconcile the competing reconstructions into coherent glaciation scenarios for the Quaternary stadials or highlight where palaeo-glaciological research is needed.
Here, we present version-1 of the SIBERICE database, a compilation of all previously published glacial geomorphology, chronometric data, and glacial reconstructions published up to 1 January 2026. The SIBERICE database is a Geographic Information System (GIS) database that make data readily accessible, including information published in often overlooked Russian-language journal articles.
How to cite: Boyes, B., Barr, I., Oien, R., Szuman, I., Winsborrow, M., and Margold, M.: SIBERICE v1: a database of Quaternary glacial reconstructions, glacial geomorphology, and chronometric data in Siberia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9053, https://doi.org/10.5194/egusphere-egu26-9053, 2026.
Glacial forefields host abundant information regarding the sedimentary processes associated with glacier dynamics. Transport pathways and sediment deposition can be characterized by investigating the landforms and sediments found in these areas. One such area is the Vernagtferner forefield in the Austrian Alps, which contrasts with other surrounding glaciers due to the presence of a large surface covered by flutes. These flutes can reach up to 250 m in length and have been continuously exposed over the past decades as the glacier recedes, but have not been researched recently. Since this glacier has been regularly studied (with records from as early as 1601) and it has been linked to surging episodes in the past, there are plenty of questions to be answered related to its current behavior. Here we present the results of sedimentological observations, as well as geomorphological mapping and statistics based on fieldwork, historical, and uncrewed aerial vehicle imagery. We highlight aspects of the glacial forefield and the contrast between what can be seen in 2023-2024 and snapshots from the past 50 years. In a changing climate, understanding how rapid glacial recession affects the deposition of sediments and the parameters that govern them will be useful in deciphering glacial dynamics and contrasting them with the paleorecord.
How to cite: Mejías Osorio, P., Wohlschlägl, R., Karbacher, S., Vandyk, T., Davies, B. J., Grasemann, B., and Le Heron, D. P.: Vernagtferner flute field findings, Austrian Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10565, https://doi.org/10.5194/egusphere-egu26-10565, 2026.
In Arctic Canada and Northeast Greenland, previous studies have found several high-elevation occurrences of marine and/or fluvial sediments of Pliocene-early Pleistocene age. In Arctic Canada, the deposits include the marine strata of the Hvitland beds on Ellesmere Island (up to ~130 m a.s.l.; Fyles et al., 1998), the marine deposits on Meighen Island (up to ~100 m a.s.l.; Fyles et al., 1991), as well as several sites with fluvial deposits, including the unconsolidated braided river deposits found on Banks Island (up to ~130 m a.s.l.; e.g., Fyles et al., 1994), Prince Patrick Island (up to ~200 m a.s.l.; Fyles, 1990), and on the high terraces of Ellesmere Island (up to ~600 m a.s.l.; Fyles, 1989) – all assumed to have be deposited prior to the carving of the deep fjord systems seen in the regions today. In Northeast Greenland, the sediment deposits include the marine Kap København (up to ~230 m; Funder et al., 1984) and Lodin Elv Formations (up to 62 m a.s.l.; Feyling-Hansen et al., 1983), assumed to have been deposited ca. 2-2.5 Ma. Previous work has studied these deposits in detail to constrain their fauna and age, their stratigraphic relationships, as well as their implications for past climates in the Arctic. However, particularly the current high elevation of the marine deposits can also put time constraints on surface uplift in these regions (e.g., Pedersen et al., 2019). Here we explore these constraints in the context of erosion driven flexural isostatic uplift associated with glacial erosion and fjord formation, allowing us to constrain the incision of the fjord systems in time, with the potential to also constrain the timing and rates of glacial erosion.
Feyling-Hanssen, R.W., Funder, S., Petersen, K.S., 1983, The Lodin Elv Formation: A Plio-Pleistocene occurrence in Greenland. Bulletin of the Geological Society of Denmark 31, 81-106.
Funder, S., Bennike, O., Mogensen, G.S., Noe-Nygaard, B., Pedersen, S.A.S., Petersen, K.S., 1984. The Kap København Formation, a late Cainozoic sedimentary sequence in North Greenland. Grønlands Geologiske Undersøgelse, 120, 9–18.
Fyles, J.G., 1989: High terrace sediments probably of Neogene age, west-central Ellesmere Island, Northwest Territories; in Current Research, Part D; Geological Survey of Canada, Paper 89-1 D, p. 101-104.
Fyles, J.G., 1990. Beaufort Formation (Late Tertiary) as seen from Prince Patrick Island, Arctic Canada. Arctic 43, 393-403.
Fyles, J.G., Marincovich, L., Jr., Matthews, J.V., Jr., Barendregt, R., 1991. Unique mollusc find in the Beaufort Formation (Pliocene) on Meighen Island, Arctic Canada; in Current Research, Part B; Geological Survey of Canada, Paper 91-1 B, 105-112.
Fyles, J.G., Hills, L.V., Matthews, J.V., Barendregt, R., Baker, J., Irving, E., Jetté, H., 1994. Ballast Brook and Beaufort Formations (late Tertiary) on Northern Banks Island, Arctic Canada. Quaternary International 22–23, 141-171.
Pedersen, V.K., Larsen, N.K., Egholm, D.L., 2019. The timing of fjord formation and early glaciations in North and Northeast Greenland. Geology 47, 682–686.
How to cite: Pedersen, V. K., Brand, C., Krog Larsen, N., and Folmer Damsgård, J.: Constraining fjord formation and isostatic uplift in Arctic Canada and Northeast Greenland using Pliocene-early Pleistocene sediment deposits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6359, https://doi.org/10.5194/egusphere-egu26-6359, 2026.
Throughout the Quaternary, cyclical variations in global ice volume are recorded by benthic marine δ18O fluctuations. This signal is dominated by the waxing and waning of Northern Hemisphere ice sheets, particularly the Laurentide Ice Sheet (LIS) in North America, which builds periodically into the largest of all ice sheets on Earth. At such times, the LIS advanced southward into the American Midwest where glacial deposits emplaced prior to Marine Isotope Stage (MIS) 6 are known from just a handful of securely-dated sites. Consequently, current understandings of LIS extent and volume through time are incomplete and poorly constrained.
Here, we focus on tills bearing putative pre-MIS 6 depositional ages along the southern and southwestern margins of the LIS. We combine single-grain sedimentary provenance analyses with cosmogenic 10Be-26Al burial dating in an aim to better resolve till chronology and provenance, using P-PINI and CosmoChron numerical models to calculate burial ages.
Building on existing magneto-, tephro-, and lithostratigraphic correlations, our new burial ages will significantly improve knowledge of the timing and extent of the LIS and its sediment source areas feeding different ice sheet sectors along the southern and southwestern margins. Our findings will improve reconstructions of LIS configurations through time, and yield new insights into Early–Middle Pleistocene global ice volume variability linked directly to the terrestrial record.
How to cite: Bertels, R., Wagner, K., Ylä-Mella, L., Stoker, B. J., Jansen, J. D., and Margold, M.: Constraining Early and Middle Pleistocene Laurentide Ice Sheet advances with 10Be-26Al burial dating, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11797, https://doi.org/10.5194/egusphere-egu26-11797, 2026.
The existence of glacial cycles in the Alps was proposed as early as the first half of the 19th century following the observation of numerous direct traces left by glaciers in lower parts of alpine valleys. However, the influence of glacial-interglacial cycles on sediment transfer from the internal source zone to the peripheral mountain range is only now being re-investigated in the context of the recent “Source to sink” approach.
The study, part of the DYMODU project (2023–2026), a collaboration between the CNRS and the RGF focuses on new geological, geomorphological and geochronological investigations undergone in the Laragne-Montéglin depression and along the Middle Durance (western Alps, France). The DYMODU project aims at deciphering the role of glacial-interglacial cycles in both the landscape organization of alpine valleys and the evolution of routing systems during the Quaternary. The sediment pile shows a characteristic sedimentary motif repeated four times, indicating a succession of four aggradation-incision cycles. The sedimentary motif records a period of aggradation during which a several tens of metres thick conglomerate fills one or more palaeo-valleys, affecting the underlying units. This conglomerate is topped by glaciogenic deposits (ground till, morainic vallum), then incised by one or more palaeo-valleys affecting the entire sedimentary series, often down to the underlying sediments before the onset of the aggradation phase of the next cycle begins, and fills these palaeo-valleys.
To confirm the integration of these cycles into the Quaternary evolution of the area, preliminary dating was carried out on various sedimentary morphostructures using Optically Stimulated Luminescence dating (OSL), Electron Spin Resonance dating (ESR) and Cosmogenic Nuclides (CN).
In this contribution, we will present the sedimentary pattern of a typical sequence. We will attempt to deconvolute the signals of the general Alpine uplift, the lithospheric flexure due to glaciation, and the glacio-isostatic rebound during deglaciation. This will enable us to discuss the interdependencies between climate and tectonics for valley glacier systems and the forcings that influenced sediment routing during the Upper Pleistocene in the Alps.
How to cite: Dervis, V., Nutz, A., Rizza, M., Braucher, R., Dietrich, P., and Tissoux, H.: Glacial-interglacial cycles in the Western Alps (Middle Durance Valley, France): sedimentary evolution and responses of continental surfaces, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12949, https://doi.org/10.5194/egusphere-egu26-12949, 2026.
In this study, we integrate marine geophysical datasets and analyses of four marine sediment cores to reconstruct the deglaciation and paleoenvironmental development of the Ardencaple Fjord and the adjacent cross-shelf trough in Northeast Greenland. Although recent studies have presented isochron-based reconstructions of the circum-Greenland ice margin since the last deglaciation, crucial knowledge gaps regarding the timing and dynamics of ice retreat still exist, particularly in offshore Northeast Greenland, where former glaciated trough systems hosted fast-flowing ice.
Our preliminary results indicate fast retreat dynamics of the ice based on observations of glacial lineation morphologies on the seabed, while sedimentological data enable spatiotemporal reconstructions of grounding line positions and floating ice margins. A preliminary chronological framework constraining the ice retreat across the core sites is based on radiocarbon dates, supplemented by paleomagnetic secular variation records. Our reconstruction further allows us to assess benthic ecosystem responses to deglaciation, contributing to the current evaluation of benthic foraminifera as a proxy for identifying stages of deglaciation in marine sediments around Greenland.
How to cite: Ramsgaard Stoltenberg, M., Kristensen, K., Böttner, C., López-Quirós, A., Davies, J., Girard, J., Detlef, H., St‐Onge, G., Pearce, C., and Seidenkrantz, M.-S.: Deglaciation of the Ardencaple Fjord and adjacent shelf environment, Northeast Greenland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14137, https://doi.org/10.5194/egusphere-egu26-14137, 2026.
Marine geophysical data and sediment cores were collected from the continental shelf and slope offshore of SE Greenland during cruise SD041 of the UK research vessel the RRS Sir David Attenborough in 2024. The cruise collected a range of geological, geophysical, oceanographic and biological data. The cruise was part of the ‘Kang-Glac’ project, the aim of which is to investigate the response of the Greenland Ice Sheet to ocean warming during the last 11,700 years. Marine geophysical data and radiocarbon-dated sediment cores provide a clear record of an extensive Greenland Ice Sheet which expanded and retreated across the continental shelf offshore of SE Greenland during, and following, the last glacial maximum. An ancestral Kangerlussuaq Glacier flowed along Kangerlussuaq Trough, a cross shelf bathymetric trough which extends from the mouth of Kangerlussuaq Fiord to the edge of the continental shelf, where it terminates in a trough-mouth fan. Streamlined subglacial bedforms record convergent ice flow into the trough. Sediment cores from along the trough recovered subglacial tills recording a grounded ice sheet. The tills are overlain by a range of deglacial, glacimarine facies recording ice sheet retreat by melting and iceberg calving. A suite of new radiocarbon dates were obtained on foraminifera and shells from the deglacial facies in a transect of cores extending from the trough-mouth fan to the inner shelf. The dates constrain the timing of initial retreat from the outer shelf and allow the position of the grounding-line to be tracked during retreat. The new radiocarbon dates significantly improve the offshore temporal constraints on the post-LGM deglaciation for this sector of the Greenland Ice Sheet and, allied with core sedimentology and foraminferal assemblage data, allow assessment of the role of ocean warming in driving retreat of the ancestral Kangerlussuaq Glacier.
How to cite: O'Cofaigh, C., Hunt, M., Lloyd, J., Hogan, K., Snowman Andresen, C., Larter, R., and Roberts, D.: Deglaciation of the ancestral Kangerlussuaq Glacier from the continental shelf offshore of SE Greenland following the LGM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14254, https://doi.org/10.5194/egusphere-egu26-14254, 2026.
Accurate reconstructions of past ice sheet dynamics are essential for constraining ice sheet sensitivity to climate forcing and projecting future sea-level rise in a warming climate. The British-Irish Ice Sheet (BIIS) during the Last Glacial Maximum presents a critical test case, and yet, reconstructions of its southern margin across Ireland differ fundamentally in both extent and timing.
Earlier geomorphic mapping-based models proposed an ice-free corridor across southern Ireland during the last glacial period. In contrast, more recent offshore and near-shore sediment-based reconstructions propose a maximum BIIS extent covering the entire island and extending to the continental shelf edge, requiring an ice sheet thick enough to override most Irish mountain ranges. This interpretation conflicts with evidence for localized mountain glaciation in the same time period in areas like the Wicklows Mountains, which would have been impossible under a thick ice sheet. The scarcity of reliable terrestrial geochronological control points (e.g., cosmogenic exposure ages, OSL, 14C) in southern Ireland significantly contributes to these uncertainties, thus limiting the accuracy of reconstructions of BIIS expansion and retreat.
This project aims to resolve these contradictions by providing robust chronological control on the position of the BIIS margin in the south of Ireland. We conducted sampling campaigns in three critical locations: the Wicklow Mountains, the Comeragh Mountains, and the Kerry Peninsula. Our sampling strategy targeted boulders at multiple elevations and aspects to capture both the timing and geometry of ice cover. We present preliminary 10Be surface-exposure ages from erratic boulders in the Comeragh Mountains (maximum elevation 792 m), sampled on transects from the northern, eastern, southern, and western slopes.
These chronological constraints will refine deglaciation scenarios for the BIIS southern margin, in turn improving our understanding of regional landscape evolution, and provide empirical data for testing ice sheet models under past climate conditions similar to future warming scenarios.
How to cite: Mariotti, A., Dulfer, H., Jackson, M., and Kelley, S. E.: Dynamics of the British-Irish Ice Sheet in the South of Ireland., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18150, https://doi.org/10.5194/egusphere-egu26-18150, 2026.
Whilst our understanding of the past ice-sheet extent of the Amundsen Sea sector at the Last Glacial Maximum (LGM) is relatively well known, the subsequent retreat (and potential re-advance) of Pine Island and Thwaites glaciers during the Holocene is contrastingly less understood. Some studies conducted across its neighbouring catchments, such as the Weddell and Ross Sea sectors, indicate that the grounding line may have retreated beyond its current position, and then subsequently re-advanced primarily due to isostatic rebound and stabilisation around pinning points. Over the Amundsen Sea sector, contrasting evidence suggests that non-linear changes in inland ice-sheet cover may have occurred, but little evidence exists for large changes affecting the continuous and gradual retreat of the grounding line from the LGM to its current position today. Here, we employ the three-dimensional PISM ice-sheet model to reconstruct the evolution of this sector since the LGM. We first explore the full parameter space using a Latin Hypercube Sampling method, and further constrain our best sets of simulations using extensive and newly available isochronal surfaces imaged by radars and dated at several snapshots throughout the last ~20 thousand years. We show that isochrones are essential for assessing the transient evolution of paleo simulations, particularly in off-divide areas of the ice sheet, and discuss how different geothermal heat-flux and SMB datasets impact the transient evolution of this sensitive sector.
How to cite: Bodart, J. A., Sutter, J. C. R., Young, D. A., Blankenship, D. D., Višnjević, V., Hermant, A., and Spezia, E.: Holocene evolution of the Amundsen Sea sector from three-dimensional modelling constrained by extensive ice-penetrating radar isochrones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20734, https://doi.org/10.5194/egusphere-egu26-20734, 2026.
The British-Irish Ice Sheet (BIIS) is one of the best-constrained paleo-ice sheets in the world, with detailed geomorphological and geochronological data constraining margins and retreat patterns. Despite this, the thickness of this former ice sheet remains uncertain. High elevation locations offer potential for constraining former ice sheet thickness; however, a lack of glacial erosion due to cold-based ice cover of mountain summits limits the use of single isotope cosmogenic exposure dating, as inherited nuclides commonly yield ages older than the last glaciation from mountain top landscapes. As such, landscapes that experienced cold-based ice cover and those at relatively high elevations are underrepresented in glacial reconstructions, both for the BIIS and globally, thus negatively affecting their ability to serve as training datasets for numerical models used to reconstruct paleo-ice masses. Here, we use paired 10Be/14C extracted from bedrock and boulder samples in high-elevation locations across Scotland and Ireland. Our multi-nuclide approach uses one long-lived nuclide, 10Be, and one short-lived nuclide, 14C, allowing for an examination of two questions: 1) What is the vertical pattern of deglaciation across the BIIS? 2) Did mountaintops exist as nunataks during the last glaciation? To address these questions, we collected samples from one site in Scotland (Cairngorm Mountains) and four Irish mountains (Dublin, Wicklow, and Mourne Mountains, as well as Mt. Brandon in Dingle) for paired 10Be and 14C analysis, yielding 22 new pairs of exposure ages. At four of our study sites, 10Be results yield exposure ages preceding the LGM, indicative of a lack of erosion during the last glaciation or prolonged exposure. Our 14C results show concentrations at or near secular equilibrium at three of those sites, indicating either exposure during the last glaciation or a period of glaciation too short for inherited 14C to decay. These results provide insight into ice-mass thinning and the spatial pattern of glacial erosion, allowing for a more holistic view of cryospheric change in the region in response to a changing climate.
How to cite: Kelley, S. E., Crowell, C., Lifton, N., and Pendleton, S.: IN SITU COSMOGENIC 10Be AND 14C: A WINDOW INTO PAST ICE SHEET THICKNESS IN SCOTLAND AND IRELAND, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20850, https://doi.org/10.5194/egusphere-egu26-20850, 2026.
Understanding the processes at glacier beds is crucial as they regulate ice flow, basal sediment dynamics, and meltwater routing, which collectively control glacier stability and response to climate change. Flute fields are a vital archive of subglacial processes, widespread in both terrestrial and marine glacial environments, whereby sediments are fashioned subglacially into lineations at different scales. The assemblages are highly variable in both environments, yet models to explain this are outstanding, and aspects of preservational bias are rarely entertained. Integrating observations from modern Alpine forefields (Austria) with exceptionally preserved Late Ordovician and Late Paleozoic examples in Africa and Arabia, we interrogate terrestrial and glaciomarine flute fields. Flutes, megaflutes, and diamictons occur in both settings, but architecture is strongly context-dependent. Terrestrial flutes degrade rapidly under surface meltwater and rainfall, whereas marine flute fields are commonly preserved beneath fine-grained shales, recording stacked lobate sediments with superimposed mega-scale glacial lineations, metre-scale flutes, and centimetre-scale soft-sediment striae. Oversteepened subaqueous flutes collapse laterally, forming fan-shaped deposits, and lateral margins exhibit scalloped surfaces that record focused subglacial meltwater discharge. We propose a conceptual model in which metre- and centimetre-scale lobes act as miniature grounding zone wedges, forming through simultaneous deposition and shearing beneath tidewater glaciers. This framework reveals how subglacial processes are recorded in preserved landforms and demonstrates that integrating modern and ancient records is essential to understanding glacier–bed interactions.
How to cite: Le Heron, D., Busfield, M., Mejías Osorio, P., Smith, B., Tofaif, S., and Wohlschlägl, R.: The formation of flute fields in glacial environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12657, https://doi.org/10.5194/egusphere-egu26-12657, 2026.
