Despite several studies (Coutterand, 2010 and references theirin) over the past decades, the chronology of glaciers advance and expansion at the Last Glacial Maximum (LGM) and subsequent retreat during the Lateglacial period in the northern French Alps remains poorly constraint, as data are still too scarce and sometimes contradictory. In this area, the interactions between major glaciers, such as the Rhône and Arve glaciers in the north and Isère glacier in the south, represent major challenges for reconstructing post-LGM glacial dynamics. Here, we present a new framework for understanding Lateglacial glacial dynamics in the Arve Valley, integrating 18 new ¹⁰Be exposure ages from glacially-transported boulders, with revised geomorphological mapping based on LiDAR-derived DEMs.

Our results indicate that the deglaciation of the Arve Valley initiated with a phase of glacial thinning around 17.6 ka BP. The Arve glacier subsequently thinned progressively but persisted in the downstream sector of the valley until the end of a readvance phase at 15.9 ka BP. Then, the glacier retreated by over 30 km within 300 years, before withdrawing toward the Mont-Blanc massif ahead of the Younger Dryas readvance.

These findings are integrated with previous studies (Wirsig et al., 2016; Roattino et al., 2022; Serra et al., 2022) conducted in the Northwestern Alps, including the Lyon piedmont lobe and the Mont-Blanc massif area, to propose a regionally consistent deglaciation scenario. To further refine our understanding, we confront ¹⁰Be exposure ages with numerical simulations using the Instructed Glacier Model (IGM, Leger et al., 2025). A dual approach enables a critically assessment of both methods: calibration of exposure ages corrections (e.g., erosion rates, snow shielding) using a model run, and inversely, using calculated exposure ages to constrain the resulting model. This will enable us to analyse possible deglaciation rates and spatial patterns in the Northwestern Alps, as well as the influence of key parameters such as geography, topography, and climate.

Coutterand, S. 2010: Etude géomorphologique des flux glaciaires dans les Alpes nord-occidentales au Pléistocène récent : du maximum de la dernière glaciation aux premières étapes de la déglaciation. PhD thesis. Université Savoie Mont-Blanc.

Leger, T. P. M., Jouvet, G., Kamleitner, S., Mey, J., Herman, F., Finley, B. D., Ivy-Ochs, S., Vieli, A., Henz, A. & Nussbaumer, S. U. 2025: A data-consistent model of the last glaciation in the Alps achieved with physics-driven AI. Nature Communications 16, 848. https://doi.org/10.1038/s41467-025-56168-3.

Roattino, T., Crouzet, C., Vassallo, R., Buoncristiani, J.-F., Carcaillet, J., Gribenski, N. & Valla, P. G. 2022: Paleogeographical reconstruction of the western French Alps foreland during the last glacial maximum using cosmogenic exposure dating. Quaternary Research 111, 68–83. https://doi.org/10.1017/qua.2022.25.

Serra, E., Valla, P. G., Gribenski, N., Carcaillet, J. & Deline, P. 2022: Post-LGM glacial and geomorphic evolution of the Dora Baltea valley (western Italian Alps). Quaternary Science Reviews 282, 107446. https://doi.org/10.1016/j.quascirev.2022.107446.

Wirsig, C., Zasadni, J., Christl, M., Akçar, N. & Ivy-Ochs, S. 2016: Dating the onset of LGM ice surface lowering in the High Alps. Quaternary Science Reviews 143, 37–50. https://doi.org/10.1016/j.quascirev.2016.05.001.

How to cite: Portal, Q., Crouzet, C., Buoncristiani, J.-F., Leger, T., Jouvet, G., and Carcaillet, J.: Lateglacial glaciers dynamics in the Mont Blanc foreland (Northern French Alps): new chronological and geomorphological constraints, with model-data coupling in the Arve Valley, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5367, https://doi.org/10.5194/egusphere-egu26-5367, 2026.

Mountain glaciers represent sensitive recorders of climate variability across a wide range of temporal and spatial scales. While their Lateglacial and Holocene dynamics are comparatively well constrained, glacier extent and behaviour prior to the Last Glacial Maximum (LGM) remain poorly documented in many mountain regions. In the Eastern Alps, the timing and magnitude of glacier advances during Marine Isotope Stage (MIS) 4 and MIS 3 are still debated, despite numerical glacier models predicting repeated pre-LGM advances into the Alpine foreland. This knowledge gap largely reflects (i) the scarcity of suitable terrestrial archives capable of recording such advances, (ii) the fact that organic material for radiocarbon dating is generally rare or absent in glacial settings and (iii) geomorphological evidence such as moraines is commonly eroded, reworked, or overprinted by subsequent glacier advances.

This study examines successions of ice-dammed glaciolacustrine sediments preserved in Alpine tributary valleys as alternative terrestrial archives for reconstructing pre-LGM glacier dynamics in the Eastern Alps. Ice-dammed lakes form when advancing trunk glaciers block the outlet of smaller tributary glaciers, creating temporary sediment traps that enable glaciolacustrine deposition. These ice-contact sediments record glacier advances and can survive multiple glacial cycles.

We focus on glaciolacustrine successions as ice-margin indicators and present a research approach that combines detailed sedimentological investigations with luminescence geochronology. The sedimentary architecture and stratigraphic relationships of ice-dammed sediments and associated delta complexes provide spatial constraints on an interconnected system of valley glaciers, including minimum ice-surface elevations and relative glacier extent. Chronological control is obtained using optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) dating of fine-grained quartz and feldspar (4–11 μm), respectively. Methodological challenges related to partial signal resetting are addressed using adapted bleaching-plateau tests [1], increasing confidence in the luminescence-based age constraints.

Our initial results from inneralpine sites indicate glacier advances which potentially reached into the Eastern Alpine foreland during MIS 4 and eventually MIS 3c, implying that glacier extent prior to the LGM was potentially more dynamic and spatially extensive than previously assumed. These results are consistent with numerical glacier model predictions [2].

From a methodological point of view, we conclude that (i) precise dating of ice-dammed lacustrine sediments enables reconstruction of the spatiotemporal dynamics of the associated ice-stream network, and (ii) luminescence-based lacustrine dating might complement geomorphological and cosmogenic-nuclide methods focused on lateral and frontal moraines used to delineate former ice margins.

References

1. Reimann, Tony; Notenboom, Paul D.; De Schipper, Matthieu A.; Wallinga, Jakob (2015): Testing for sufficient signal resetting during sediment transport using a polymineral multiple-signal luminescence approach. In: Quaternary Geochronology 25, S. 26–36. DOI: 10.1016/j.quageo.2014.09.002.

2. Jouvet, Guillaume; Cohen, Denis; Russo, Emmanuele; Buzan, Jonathan; Raible, Christoph C.; Haeberli, Wilfried et al. (2023): Coupled climate-glacier modelling of the last glaciation in the Alps. In: J. Glaciol. 69 (278), S. 1956–1970. DOI: 10.1017/jog.2023.74.

How to cite: Spitaler, B., Gruber, A., Reitner, J. M., and Meyer, M. C.: Are ice-contact lacustrine sediments in the Eastern Alps capable of constraining pre-LGM ice-stream network dynamics? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20278, https://doi.org/10.5194/egusphere-egu26-20278, 2026.

Reconstructions of glacier Equilibrium Line Altitudes (ELAs) from geomorphological evidence are often the only source of quantitative palaeoclimatic information in mountainous regions. The ELA is the average altitude of zero net mass balance and divides a glacier into an accumulation and an ablation area. While primarily controlled by summer temperature and winter precipitation, the position of the ELA is also frequently modulated by local topoclimatic factors, such as shading, supraglacial debris cover, avalanching or wind-driven snow redistribution. As a result, there can be substantial differences of several 100 meters between ELAs of neighbouring glaciers within the same climatic region. If such topoclimatic controls are not accounted for, this can introduce notable biases into ELA-based palaeoclimate reconstructions.

To better constrain the effect of topoclimatic control on glacier ELAs at the regional to global scale, we present the results of a comprehensive data analysis based on the Randolph Glacier Inventory (RGI), version 7.0. We compare glacier-specific ELAs calculated through the Accumulation Area Ratio and Area-Altitude Balance Ratio methods to a variety of topographic parameters, such as the amount of received solar radiation, the curvature of the ice surface and the topographic openness of the terrain. We show that there is a strong correlation between local ELA differences and some of these parameters and use a machine-learning tool to predict this ELA offset using only a digital elevation model and a glacier outline as input. This tool can be used to assess the topographic bias related to any calculated ELA and has the potential to lead to more reliable palaeoclimate reconstructions in a variety of settings.

How to cite: Rettig, L., Huss, M., and Kneib, M.: Quantifying topoclimatic control on glacier Equilibrium Line Altitudes at the regional and global scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12599, https://doi.org/10.5194/egusphere-egu26-12599, 2026.

Numerical palaeoglacier modelling is being applied to mountain glacier systems worldwide to investigate past ice dynamics, climatic controls, and glacier–climate interactions.  At present, there is no overview or consensus framework for evaluating the performance of these models, nor agreed standards for determining whether simulated glacier distribution and geometry are plausibly reconstructed through time.

To assess how palaeoglacier models in mountains are being validated and evaluated, we conducted a systematic review of 94 coupled mass-balance–ice-dynamics palaeoglacier models worldwide. For each study, we recorded validation approaches (visual, quantitative, and/or statistical), the glaciological attributes evaluated (extent, area, ice thickness, mass balance, ice flow, glacier distribution), the validation datasets used (direct geomorphological evidence versus previous model outputs), and the spatial structure of validation (point-, line-, polygon-, or grid-based). We also synthesised validation workflows to document the datasets, metrics, and decision criteria employed.

Our results show that the methodological design used to validate model outputs vary considerably between studies. We found that 80% of reviewed studies incorporate visual evaluation of model outputs to some extent, and 43% rely exclusively on subjective visual interpretation. A further 4% of studies do not perform any form of model validation or evaluation. Most studies validate glacier length (89%), whereas 48% of cases validate only one individual model output. Geomorphic reconstructions are used as validation datasets in only 27% of studies, indicating that most validation workflows rely on mapped glacial landforms. Because glacier length and glacial landforms dominate validation strategies, point- and line-based features constitute the majority of spatial validation data, with polygon- or grid-based approaches remaining comparatively rare.

We observe that the interpretation of model performance often remains subjective and reliant on the judgement of a limited number of research authors, which hinders reproducibility and intercomparison across studies. This reliance on subjective visual interpretation reflects persistent challenges in palaeoglacier model validation that are not being solved by existing tools and workflows designed to measure model-data fit. Our review indicates that uneven geomorphic evidence coverage, positional uncertainty between mapped landforms and simulated ice margins, resolution mismatches between geomorphic data and model outputs, chronological dating uncertainties, parameter uncertainty, and ‘equifinality’ (i.e., where multiple parameter combinations can yield similarly plausible glacier geometries) within glacier models collectively hinder robust quantitative validation.

Therefore, we propose a probabilistic, equifinality-aware validation framework that integrates geomorphically based reconstructions, multiple model outputs (e.g., ice extent, ice thickness), temporal steps (e.g., LGM and present-day), and performance metrics (e.g., overestimation, underestimation). Our approach evaluates ice cover as a probability field derived from an ensemble of acceptable simulations, explicitly acknowledging parameter non-uniqueness of equifinal modelling outputs. This approach identifies spatial patterns of robust agreement and persistent uncertainty, avoids subjective selection of a best-fit simulation, and enables domain-wide validation that captures spatial and temporal heterogeneity in glacier behaviour, thereby providing a more transparent and reproducible basis for evaluating palaeoglacier model–data fit.

How to cite: Lima, A. C., Barndon, S., Chandler, D. M., Yingkui, L., and Flantua, S. G. A.: Validation Practices in Mountain Palaeoglacier Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19769, https://doi.org/10.5194/egusphere-egu26-19769, 2026.

The sensitivity of alpine glaciation to climatic warming is underscored by global reductions in ice mass over the last century and accelerated losses observed in recent decades. Given the dependence of local populations, infrastructure, and ecosystems on reliable snowpack and meltwater supply, the forecasted demise of many mountain glaciers critically motivates investigations into the dynamics underlying glacial retreat and advance under past boundary conditions. However, the timing and extent of glacial limits are progressively less well constrained through geologic time, particularly in mountain regions, due to the inevitable loss of geomorphic indicators through subsequent glacial advance and erosion. Secondary mineral deposits in some alpine caves offer a unique solution to glacial reconstructions, because warm-based ice cover allows the cave system to remain unfrozen with active speleothem growth. Importantly, the loss of soil cover and presence of glacial ice induces an abrupt switch from a carbonic-acid to a sulfuric-acid dominated system in caves hosted by impure carbonate rocks, which can be detected through geochemical analysis of radiometrically dated speleothems. While this category of ‘subglacial speleothems’ has long been described, only recently has a thorough multiproxy approach been developed and tested, which can robustly identify the timing and dynamics of glaciation over alpine cave sites. In addition to key changes in the stable-isotope composition of carbon (δ¹³C) and oxygen (δ¹⁸O), the dominance of sulfuric-acid dissolution leads to an increase in speleothem sulfate, often by more than an order of magnitude, which may be accompanied by a decrease in the δ³⁴S of sulfate due to enhanced sulfide oxidation. Glacial weathering processes are captured by certain trace elements in speleothem calcite, whereas the redox evolution of infiltrating waters (reflecting the hydrological balance of surface and subglacial meltwaters) is reflected in the oxygen-isotope composition of speleothem sulfate. Finally, U-series dating (U-Th and U-Pb) allows for accurate geochronological constraints, sometimes with per mil precision, throughout the Quaternary and beyond. Herein, we present case studies from the European Alps and Western Caucasus that successfully document the advance and retreat of warm-based glaciers without reference to surficial deposits and landforms. We further discuss uncertainties associated with the site-specific behavior of geochemical proxies that may limit their application to some glacial reconstructions.

How to cite: Baker, J., Honiat, A., Wynn, P., Moseley, G., Mertz, R., and Spötl, C.: A multiproxy speleothem-based approach to reconstructing alpine glaciation beyond the limits of geomorphological evidence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14454, https://doi.org/10.5194/egusphere-egu26-14454, 2026.

New ¹⁰Be exposure ages from the Arenig mountains, North Wales have been obtained to complement ³⁶Cl ages and help constrain the timing of deglaciation in NE Wales. The last phase of cirque glaciation is dated to the Younger Dryas and this is consistent with previous assumptions of deglaciation in Wales. In South Wales, in the Brecon Beacons, the last cirque glaciers were higher than those in the north, which is consistent with increasing cirque altitude with lower latitude. Radiocarbon dating from bogs inside of moraines in these cirques also supports a Younger Dryas age for the last phase of glaciation. However, further south in the South Wales Valleys, the last former cirque glaciers were at some of the lowest altitudes in Wales. The glaciers occupied cirques that are lower than in the nearby Brecon Beacons and these cirques represent an anomalous population of low-lying cirques compared with the rest of Wales. Reasons for this are either because 1) wetter conditions existed the South Wales Valleys than the rest of Wales leading to lower cirque glaciation during the Younger or 2) the last cirque glaciers were present and formed moraines prior to the Younger Dryas, possibly when the Welsh Ice cap covered Wales north of the Brecon Beacon watershed divide. Ongoing work will apply ¹⁰Be exposure dating from moraine boulders and ¹⁴C dating from bogs inside of moraines in the cirques of the Brecon Beacons and South Wales Valleys to test these hypotheses further. 

How to cite: Hughes, P., Thomas, O., Darvill, C., Ryan, P., and Fink, D.: Examining the nature and timing of deglaciation in Britain: new evidence from the Arenigs, Brecon Beacons and South Wales Valleys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13791, https://doi.org/10.5194/egusphere-egu26-13791, 2026.

Numerical models simulating potential future climate schemes are tested against different proxy-based reconstruction of paleoclimate and must be finely tuned. In the north Atlantic region, records indicate that the Last Glacial Termination was interrupted by rapid, high-amplitude reversals (Heinrich Stadial 1, Younger Dryas) during which temperatures got back to nearly ice-age cold conditions.
These events are thought to be year-round cooling periods and could be close analogues for future climate change in the north Atlantic region. Terrestrial glacial deposits give a high resolution vantage on abrupt shifts but remain poorly investigated. Previous studies based on surface exposure dating on glacial landforms show that glaciers retreats occurred within HS1 and YD, contradicting the prevailing models. Thus mapping palaeo-mountain glaciers former extend, dating their retreat and reconstructing their successive palaeo-equilibrium lines altitude allow to determine whether this pattern is a consensus for the northern hemisphere palaeo-glaciers. This approach also provides information on the timing and magnitude of past climate change. This study is based on the west coast of Ireland directly impacted by westerlies, located downwind of the North Atlantic Ocean and which contains key sites where palaeo-mountain glaciers let the footprints of their passage. Here, we present the first results  from the Geologic Perspectives on Abrupt Climate Change (GeoPAC²) project: Strengthening Ireland’s capacity for projecting future change. The new beryllium-10-dated glacier records reveals phase of ice retreat occurring within HS1. It questions the rising seasonality hypothesis which suggests an increase of summer temperatures during melting season. The results of this work will provide useful quantitative data for investigate North Atlantic climate variability and improve both climate and glaciological models.

How to cite: Roignot, A. and Bromley, G.: Palaeo-glaciers archives in western Ireland as a vantage on abrupt shifts of the Last Glacial Termination , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18404, https://doi.org/10.5194/egusphere-egu26-18404, 2026.

The Ural Mountains form a major physiographic boundary between the East European Plain and West Siberia, both repeatedly glaciated during the Pleistocene by the Barents–Kara ice sheet. Although the present-day topography reflects significant glacial modification, the extent, chronology, and interaction of mountain glaciers with the Barents–Kara ice sheet remain poorly constrained. Correlation of glacial and interglacial deposits across the range is hindered by incomplete sedimentary records, contrasting palaeoclimatic conditions, and limited chronological control, which collectively obscure regional glacial reconstructions.  This study presents an extensive mapping exercise of hundreds of moraines in the northern Urals. These landforms are then used to reconstruct palaeoglacier equilibrium line altitudes (ELAs) to assess glacier distribution and synchroneity of moraine formation. ELA trends along the Urals are analysed to evaluate whether, and where, montane ice caps developed during the last major glaciation. Furthermore, palaeo-ELA data are used to link former ice margins to dated moraines in the Polar Urals, providing new insights into the spatial and temporal dynamics of montane glaciations south of the Arctic Circle. The findings indicate that  the E-W asymmetry in the hypsometry of the Urals exerted  the primary control on the development of the piedmont glaciers on the lowlands. Furthermore, Glacier reconstructions combined with geomorphological evidence favour the existence of extensive montane ice caps over the Urals with moisture sourced from extensive ice dammed lakes  locates on both sides of the mountain range.

How to cite: Kurjanski, B., Spagnolo, M., Bushueva, I., Barr, I., Rea, B., Solomina, O., and Kutuzov, S.: Palaeoglaciations in the Polar and Subpolar Ural Mountains., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21654, https://doi.org/10.5194/egusphere-egu26-21654, 2026.

Andean landscapes contain key paleoclimate records of the Southern Hemisphere. However, many mountain regions in the Andes remain scarcely investigated in detail. In this study, we present an analysis of the Nevados de Chillán Volcanic Complex (NCVC), in Southern Chile (37ºS), aiming at unveiling the potential of this landscape to register past climatic conditions. This site is within a region of Temperate-Mediterranean climate transition (TMT; 35.5°–39.5°S), which comprises most of the Southern Volcanic zone (SVZ) of the Andes, that host the most active volcanoes of the cordillera, almost all of them are ice-capped. These volcanoes witnessed the multiple expansions and retreats of the Patagonian Ice Sheet (PIS) during Pleistocene glaciations and of smaller mountain glaciers during the Holocene, reflecting local climatic variations. Our findings show the NCVC preserves a recent and diverse glacial record, as identified with a detailed geomorphological mapping (1:20.000). The elevation and preservation of glacial deposits and scoured bedrock point to multiple glacial advances after the Last Glacial Maximum. Current analysis of ages obtained with ³⁶Cl dating of andesitic boulders atop moraines support field observations and geomorphological interpretations, with different episodes from Early-Middle Holocene until the last centuries. The oldest measurements in could represent late glacial advances, which also occurred in central Andes and Patagonia. Ages from frontal moraines are coeval with the Little Ice Age, consistent with results of recent studies in adjacent volcanic areas. From lateral moraines dispersed age results suggest persistent glacial activity since the last millennia until 200 years ago. The younger ages are supported by historical accounts from 19^th century that document glacial extent comparable with the location of sampled boulders.  Overall, these results should be interpreted in light of uncertainties related to geomorphological mapping and especially with chronological constraints.  Despite these limitations, the integrated approach adopted here provides a useful framework to identify regional-scale patterns of glacier fluctuations and to assess their sensitivity to climatic variability during the Late Pleistocene–Holocene.

How to cite: Navas, S., Fernández, A., Jaque, E., Owen, L., Figueiredo, P., and Stansell, N.: Glacial record and 36Cl cosmogenic dating in the Nevados de Chillán Volcanic Complex, Northern Patagonia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16061, https://doi.org/10.5194/egusphere-egu26-16061, 2026.