GM10.4 | Mountain and ice sheet glaciations: Glacial landforms and their paleoclimatic interpretation
EDI
Mountain and ice sheet glaciations: Glacial landforms and their paleoclimatic interpretation
Co-organized by CL1.2/CR4
Convener: Danni Pearce | Co-conveners: Rachel OienECSECS, Benjamin BoyesECSECS, Giovanni Monegato, Helen DulferECSECS, Jürgen Reitner, Stefan Winkler
Orals
| Tue, 16 Apr, 10:45–12:25 (CEST), 14:00–15:40 (CEST)
 
Room G1
Posters on site
| Attendance Mon, 15 Apr, 10:45–12:30 (CEST) | Display Mon, 15 Apr, 08:30–12:30
 
Hall X3
Orals |
Tue, 10:45
Mon, 10:45
Mountain and ice sheet glaciations provide an invaluable record for past and present climate change. However, varying geomorphological process-systems, specific glaciological conditions and topography can make regional, intra-hemispheric and global correlations challenging. This problem is further enhanced by ongoing specialisation within the scientific community. Despite such challenges glacier and ice sheet reconstructions remains a crucial paleo-environmental proxy.

The primary aim of this session is to evaluate the potential of mountain and ice sheet glaciation records and stimulate further research in this important field. Contributions on all relevant aspects are welcomed, for example: (a) glacial landforms and reconstruction of past glaciers and ice sheets, (b) dating techniques and geochronology compilations, (c) ice dynamics and paleoclimatic interpretations, or (d) impacts of ecosystems and human evolution/society. We would particularly like to invite contributions addressing regional and hemispheric connections, issues, and advances. The temporal scale of the session will encompass Early Pleistocene glaciations through to the Last Glacial Maximum, and Holocene/modern glaciers. In the past, this session has attracted contributions from a wide range of locations and a diversity in methodological approaches. It has become a platform for on-going collaborative research on mountain glaciations where people are given the opportunity to exchange ideas and expertise.

ECR keynote talks:

Block 1, Mountain glacier reconstruction
Lukas Rettig - A glacier-based reconstruction of the Last Glacial Maximum climate in the southern European Alps.

Block 2, Ice sheet reconstruction
Gwyneth Rivers - Using sediment facies & ground penetrating radar profiles to investigate the internal architecture and genesis of De Geer moraines.

Session assets

Orals: Tue, 16 Apr | Room G1

Chairpersons: Danni Pearce, Rachel Oien, Stefan Winkler
10:45–10:50
10:50–11:00
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EGU24-1010
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ECS
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Highlight
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On-site presentation
Lukas Rettig, Giovanni Monegato, Sarah Kamleitner, Matteo Spagnolo, Adriano Ribolini, Susan Ivy-Ochs, Brice R. Rea, Franco Gianotti, and Paolo Mozzi

Improved records of precipitation and temperature are crucial to understand the evolution of Alpine glaciers during the Last Glacial Maximum (LGM). Palaeoclimate models and proxy data have suggested an increased moisture supply to the southern face of the Alps during the LGM, following a south-ward shift of the North-Atlantic jet stream. Ground control for such models, however, has been lacking for many sectors of the Alps, and regional climatic gradients have therefore remained poorly constrained. Here, we present new insights into the LGM palaeoclimate in the southern Alps, using the Equilibrium Line Altitudes (ELAs) of marginal glaciers as proxy. Marginal glaciers include ice caps, cirque, and valley glaciers that throughout the LGM remained isolated from larger outlet lobes connected to the Alpine ice network. Several sites of marginal glaciation were investigated through a combination of geomorphological mapping, surface exposure dating (both 10Be and 36Cl dating), and numerical reconstructions of palaeoglacier geometries and ELAs.

The chronological data indicate that marginal glaciers across the southern Alps reached their maximum extent by ca. 24 ka and that an important readvance occurred at 19 ka, at the end of the LGM. Reconstructed palaeoglacier ELAs show considerable variations, from ca. 1100 m a.s.l. in the Julian and Carnic Prealps (SE-Alps) up to almost 2000 m a.s.l. in the Maritime Alps (SW-Alps). Minor differences between the sites can be attributed to topoclimatic factors (i.e., received solar radiation related to catchment aspect). Spatial trends in ELA, however, primarily reflect regional climatic gradients. More specifically, we recognised: (1) a N-S gradient related to increasing summer temperatures with lower latitudes, and (2) a strong E-W gradient driven by precipitation. For all sites, our data indicate little to no reduction in LGM precipitation compared to the present day, highlighting the importance of substantial precipitation for the build-up of marginal LGM glaciers in the southern Alps.

How to cite: Rettig, L., Monegato, G., Kamleitner, S., Spagnolo, M., Ribolini, A., Ivy-Ochs, S., Rea, B. R., Gianotti, F., and Mozzi, P.:   A glacier-based reconstruction of the Last Glacial Maximum climate in the southern European Alps    , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1010, https://doi.org/10.5194/egusphere-egu24-1010, 2024.

11:00–11:10
11:10–11:20
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EGU24-9498
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ECS
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On-site presentation
Gerit E.U. Griesmeier, Jürgen M. Reitner, Daniel P. Le Heron, Christopher Lüthgens, and Gustav Firla

Within the Alps, the erosive effects of glaciers during the Last Glacial Maximum (LGM) means that evidence for earlier glaciations is rare. At Gröbminger Mitterberg (GM), traces of the history prior to the LGM are conserved below a layer of basal till of the LGM. The GM itself is a flat-topped hill located in the Enns valley in Styria (Austria), rising to an elevation of ca. 200 m above the Enns valley floor. It is situated between Mesozoic carbonates in the north and crystalline basement units in the south. The GM comprises crystalline basement covered by fluvial and deltaic sediments, overlain by a subglacial till. Based on the distribution of the sediments, borehole data and geoelectric data, an ancient river channel across GM can be reconstructed. 
The lithological spectrum of the fluvial and deltaic sediments at GM shows that the distribution of material from the south and the north is around 70 : 30 % throughout the GM, which is the same as that of the modern Enns river. This suggests that all sediments at GM and the channel across it were greatly impacted by the Enns river. The Enns valley in the area of GM can now be reconstructed as follows:
Some time before the Riss Glaciation (MIS 6), the Enns river meandered in a valley, situated at an elevation ca. 100 m higher than the present-day river. Large alluvial fans flowing northward into the Enns valley forced the Enns river to flow across Mitterberg in a channel, which was probably already partly created during earlier glaciations. The first crystalline pebbles reached the north of GM. During the phase of ice decay of the Riss Glaciation, ice marginal lakes developed at the margin of GM, where deltaic sediments developed. After the Riss Glaciation, the Enns river found itself in a similar situation like today and the Enns valley aggraded until it reached the top of GM shortly before the last glaciation. Large alluvial fans further east dammed a lake, which covered GM and was quickly filled with sediments. This part of the chronology is also supported by optically stimulated luminescence data using single grains of potassium-rich feldspar. They will be presented at the conference. The braided Enns valley was not only much wider than today, but also transported crystalline pebbles to the northern part of GM. In the course of the LGM, most of the previously deposited sediments were preserved and covered by basal till. 
The evolution of the Enns valley emphasises the close coupling between climate, erosion and sedimentation processes. Today, the Enns river incises again and sediments at GM are going to be eroded, but parts remain in their position. These current changes have probably repeatedly occurred through time and we can never be sure, how much time is really preserved on GM. Nevertheless, the proposed reconstruction in the Enns valley can also give hints on the history of other alpine valleys and may be helpful for future models of alpine wide glaciation and greenhouse phases.

How to cite: Griesmeier, G. E. U., Reitner, J. M., Le Heron, D. P., Lüthgens, C., and Firla, G.: Reconstructing the Enns valley in the course of the ice ages based on findings on Gröbminger Mitterberg (Austria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9498, https://doi.org/10.5194/egusphere-egu24-9498, 2024.

11:20–11:30
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EGU24-16431
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On-site presentation
Daniela Pascal, Alfred Vespremeanu-Stroe, Regis Braucher, Razvan Popescu, Mihaela Enachescu, Alexandru Berbecariu, and Adrian Vasile

Past glaciations extent and chronology in the Romanian Carpathians have been disputed along most of the 20th century. Despite the recent studies presenting numerical age datings of the glacial deposits and erosion surfaces, the view on the latest glacial activity remained in debate due to results from Retezat Massif (one of the high and best studied massifs from Southern Carpathians), where authors found no evidences of Younger Dryas glaciers. In this context, we bring in the discussion new data from Retezat but even more from the Făgăraș Massif, which is the highest and largest massif from Southern Carpathians but less studied in relation to the Pleistocene glaciations with only a handful of numerical ages obtained so far. The new 10Be exposure ages collected from the highest morraines, fit the Younger Dryas - Early Holocene interval, in good agreement with European records, suggesting the glaciers reformation and advance during the Younger Dryas. It appears that some of the Younger Dryas glaciers survived in the first two millenia of the Early Holocene or reformed during Pre-Boreal Oscillation when cool and humid conditions have been present over Europe. Finally, we modeled the presence of Younger Dryas glaciers for the whole Făgăraș massif using the topographic and microclimatic characteristics of the glacial cirques which hosted new glaciers (proven by numerical ages) and found that ca 90 glaciers restricted to cirques formed during Younger Dryas in the Făgăraș massif. Samples were chemically processed at LN2C at CEREGE, France and at RoAMS Laboratory - IFIN HH, Romania. Targets of purified BeO were prepared for AMS measurements and measured at ASTER, the French National AMS Facility (CEREGE, Aix en Provence).

How to cite: Pascal, D., Vespremeanu-Stroe, A., Braucher, R., Popescu, R., Enachescu, M., Berbecariu, A., and Vasile, A.: New data from Făgăraș and Retezat Massifs set the timeframe of the last glacial activity in Southern Carpathins during Younger Dryas and Early Holocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16431, https://doi.org/10.5194/egusphere-egu24-16431, 2024.

11:30–11:40
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EGU24-2307
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On-site presentation
Alastair Curry, Olly Bartlett, and Jonathan Newitt

Understanding the extent, retreat dynamics and climate-glacier coupling of the Scottish Ice Sheet during the Last Glacial-Interglacial Transition (LGIT) is hampered by a highly fragmentary geomorphological record, and is dependent on a precise and accurate dating framework to constrain deglaciation. On land, readvance of the retreating ice margin is recorded in part of NW Scotland by moraines of the Wester Ross Readvance at ~15.4-15.8 ka, preceding the Lateglacial Interstade and the Loch Lomond Stade ~12.9-11.7 ka. While the number of dated landforms has increased in recent years, the LGIT chronology in NW Scotland is primarily based on a limited number of samples per site, using Terrestrial Cosmogenic Nuclide Dating (TCND) methods that can yield conflicting or uncertain results. This highlights the value of developing complementary dating methods.

Previous studies have questioned the reliability of the Schmidt hammer exposure dating (SHD) technique on lithologies other than granite. This research (i) evaluates the use of SHD on sandstone in the NW Scottish Highlands; (ii) develops a local, lithology-specific calibration curve; (iii) applies this to estimate the age of undated surfaces and tests existing interpretations of landscape change during the LGIT. Field results from a 1,500 km2 area of NW Scotland conclude that SHD can detect significant differences (p <0.001) between Torridonian sandstone surfaces of Wester Ross Readvance and Loch Lomond Stadial age. Based on 31 existing, re-calibrated 10Be ages, a calibration curve was generated (R2 = 0.58, p <0.001) for the period ~18-11 ka BP, and applied to 17 undated Torridonian sandstone surfaces. Our findings support the view that on selected lithologies and with rigorous adherence to careful field procedures, SHD can represent a valuable, cost-effective and reliable tool for obtaining large numerical dating samples for landforms in formerly glaciated terrain.

How to cite: Curry, A., Bartlett, O., and Newitt, J.: Schmidt hammer exposure dating (SHD) the Last Glacial-Interglacial Transition in Wester Ross, Scotland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2307, https://doi.org/10.5194/egusphere-egu24-2307, 2024.

11:40–11:50
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EGU24-11208
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On-site presentation
Audrey Margirier, Ann Rowan, Julien Brondex, Georgina E. King, Christoph Schmidt, David L. Egholm, Vivi K. Pedersen, C. Scott Watson, Remy Veness, Leif Anderson, and Benjamin Lehmann

 

Constraining the pathways and time scales of englacial sediment transport is of primary importance for both understanding the processes that move sediment through glacierised catchments and quantifying the response of mountain glaciers to climate change. However, sediment transport through glaciers is a more complex process than ice flow and difficult to observe; clasts can be transported englacially and at the ice margins, but also deposited into moraines before being re-entrained into englacial transport.

We developed a novel method taking a Lagrangian approach that combines luminescence rock surface burial dating of the time for englacial transport of individual rock debris with ice-dynamical glacier evolution modelling of glacial sediment transport to quantify rates of sediment transport through the Miage Glacier catchment in the Italian Alps. Luminescence rock surface burial dating allows determining the burial duration of rocks after they have been exposed to sunlight, but this method has not previously been applied to englacial clasts.

We obtained luminescence ages for seven samples embedded in the ice in the ablation zone of Miage Glacier, with burial ages ranging from 0.2 ± 0.1 ka to 5.0 ± 1.4 ka. Samples collected in the upper part of the ablation zone yield younger ages than samples collected near the terminus. The younger luminescence ages (0.2 ± 0.1 ka and 0.3 ± 0.1 ka) are consistent with expected burial duration based on the present-day glacier velocity. In contrast, older luminescence ages obtained for samples located in the lower part of the ablation zone (1.2 ± 0.1 ka to 5.0 ± 1.4 ka) show that these samples record a longer and more complex burial history, suggesting that these samples were either stored in the headwall area or within moraines for several thousand years before being entrained in the ice. In the Miage catchment, debris could have been stored in a moraine at the junction between the Bionnassay Glacier and the Dome Glacier before being entrained in the Miage glacier. We compare the burial ages of the englacial clasts with simulations of glacial sediment transport using a Lagrangian particle tracking scheme in the glacier model iSOSIA. The model results illustrate the range of englacial and subglacial sediment flow paths through the Miage Glacier and simulate similar durations of englacial transport to those obtained for our luminescence samples.

How to cite: Margirier, A., Rowan, A., Brondex, J., King, G. E., Schmidt, C., Egholm, D. L., Pedersen, V. K., Watson, C. S., Veness, R., Anderson, L., and Lehmann, B.: Tracking sediment transport through the Miage Glacier, Italy, combining a Lagrangian approach with luminescence burial dating of englacial clasts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11208, https://doi.org/10.5194/egusphere-egu24-11208, 2024.

11:50–12:00
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EGU24-11358
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ECS
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On-site presentation
Bennet Schuster, Sebastian Schaller, Lukas Gegg, Marius W. Buechi, Flavio S. Anselmetti, and Frank Preusser

Overdeepened basins are shaped and filled by the interplay of erosion and deposition during one or more glacial-interglacial cycles. Understanding and correlating the sedimentary infill of overdeepened systems is a key to understanding glacial dynamics in terms of the timing, extent, and character of Quaternary glaciations. Therefore, numerous overdeepened structures in the northern Alpine foreland have been explored by research drilling in recent years, resulting in a large collection of sediment cores of excellent quality, providing a unique opportunity to gain insight into these structures. Exploration of these basins shows that a depositional sequence in the sedimentary record of a glacial overdeepening typically begins with the subglacial deposition of coarse-grained units (diamicts and gravels), reflecting complex ice-bed-interactions during the transition from erosion to deposition. The identification and interpretation of these potential ice-contact sediments is crucial for understanding the glacial sedimentary sequences.

In this study, we use X-ray computed tomography (CT) scanning to identify and quantify sedimentological features and systematically characterise a wide range of potential ice-contact sediments from different levels within the sedimentary record of several overdeepened basins in the northern Alpine foreland. CT scanning provides a powerful tool for the detailed analysis of sedimentary drill cores, particularly in these glacial sediments, where such examinations have never been carried out on a large scale. This study aims to establish a CT analysis workflow and a database of characteristics of ice-contact sediments. This will contribute to the controversial discussion of the relevant processes that form ice-contact sediments and improve our ability to identify ice-contact sediments and their genesis in overdeepened basins.

How to cite: Schuster, B., Schaller, S., Gegg, L., Buechi, M. W., Anselmetti, F. S., and Preusser, F.: Quantitative CT scan analysis: an innovative tool for interpreting ice-contact sediments from overdeepened basins of the northern Alpine foreland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11358, https://doi.org/10.5194/egusphere-egu24-11358, 2024.

12:00–12:10
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EGU24-21507
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ECS
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Highlight
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On-site presentation
The glacier-climate history of Cordillera Paraiacaca and Cordillera Huaytapallana, Central Peruvian Andes, From the Late Pleistocene to Holocene.
(withdrawn)
Lucy Ashpitel, Matteo Spagnolo, Brice Rea, Jose Úbeda, David Fink, Ronald Concha, Krista Simon, Pool Vasquez, Steve Kotevski, Anshuman Bhardwaj, Donal Mullan, and Rachel Oien
12:10–12:25
Lunch break
Chairpersons: Benjamin Boyes, Helen Dulfer
14:00–14:10
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EGU24-574
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ECS
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On-site presentation
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Gwyneth Rivers, Robert Storrar, Joni Mäkinen, Antti Ojala, Naomi Holmes, and Camilla Holmroos

De Geer moraines (DGMs) have the potential to generate very high-resolution spatial and temporal ice margin reconstructions (~annual in contrast to 100-500 years, the current state-of-the-art). Existing studies suggest that DGMs likely form annually in a sub-aqueous, ice-marginal environment whereby basal sediments are advected and deposited at the grounding-line during seasonal advances. However, there have also been suggestions of a crevasse-fill origin that challenges this temporal regularity. Whilst the spatiotemporal properties of DGMs are disputed, the balance of evidence suggests an ice-marginal depositional environment with annual/seasonal regularities. Understanding the processes related to DGM formation is therefore critical, as it underpins the ability to use DGM to delineate ice-marginal retreat at unprecedented (potentially annual) resolutions.

A recent large-scale 3D morphometry study of DGMs and Crevasse-Squeeze Ridges (CSRs) was undertaken to constrain landform metrics and explore their formation processes. The results revealed statistically significant differences across all morphometrics between the sampled DGMs and CSRs. DGMs were found to be lower-relief, narrower, slightly more asymmetrical, and more sinuous than the studied CSRs. The morphometrics of DGMs support an ice marginal depositional environment. Furthermore, tendencies for cross-sectional asymmetry suggest a unidirectional push movement involved during formation. These inferences, however, must be supported with geophysical and/or sedimentological investigations.

Here we present the results of a field study using sedimentological and geophysical (Ground Penetrating Radar) techniques to investigate the internal architecture of DGMs in southwest Finland. Sedimentological data was acquired from two excavated exposures and 55 GPR profiles were obtained from four different locations across SW Finland. Radar facies were identified and corroborated with the lithofacies units as observed in the ca. 30 m long trench excavations. Typically, these facies comprise of stacked thrusted planes of laminated clay and diamicton on proximal slopes, sheared diamicton on surfaces indicative of proglacial pushing/overriding, and gravity-driven flow deposits on distal slopes. At places, glaciotectonic structures such as dipping, faults and folds were also identified.

The results may be used to complement the existing morphometry study, constraining the main processes involved in DGM formation and validating the use of DGMs as ice marginal indicators. This can ultimately be used as a foundation to explore the climatic significance of DGM ridges, thus meriting further work to constrain the spatial and temporal properties of DGMs during deglaciation.

How to cite: Rivers, G., Storrar, R., Mäkinen, J., Ojala, A., Holmes, N., and Holmroos, C.: Using sediment facies & ground penetrating radar profiles to investigate the internal architecture and genesis of De Geer moraines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-574, https://doi.org/10.5194/egusphere-egu24-574, 2024.

14:10–14:20
14:20–14:30
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EGU24-6044
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Highlight
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On-site presentation
Chris Clark, Jeremy Ely, Anna Hughes, Rosie Archer, Ben Boyes, Frances Butcher, Nico Dewald, Chris Diemont, Helen Dulfer, and Sarah Bradley

The field of palaeo-glaciology has evolved from inquisitiveness about glaciated landscapes - how they came into being - into the wider role of improving glaciological understanding and more recently, into testing or improving the fidelity of ice sheet modelling approaches. Such endeavors are crucial for improving forecasts of today’s diminishing polar ice sheets and for predicting sea-level rise. The PalGlac project (2018 to 2024) is using glacial landform mapping and analysis to advance our understanding of ice sheets, and in this talk, we will focus on the demise of the Scandinavian Ice Sheet and how landform data is used to either test or calibrate (nudge) ice sheet modelling simulations.

Glacial landforms such as drumlins, moraines, meltwater channels and eskers record spatially extensive components of ice sheet activity, namely 1) ice flow geometry and thermal regime, 2) the pattern of ice-marginal recession, and 3) the subglacial flow of meltwater that likely modulated the first two. High-resolution (metres) digital elevation models (DEMs) are revolutionising the mapping and understanding of glacial landforms (Johnson et al. 2015). They permit detailed investigation across areas so large as to have been unimaginable decades ago. We here report on a multi-person mapping investigation of glacial landforms across the land areas of Fennoscandia, northern Europe, and parts of Russia, and which have yielded over 350,000  individual features recording ice flow (250,000), ice margins (70,000), and meltwater routing (30,000). All data, held in a GIS, are used to build a first-order reconstruction of the pattern of ice flow changes and ice margin retreat. Much of these data reveal a useful confirmation and replication of prior studies, which we now know with improved robustness, and with many new aspects being revealed, notably in ice divide positions.

Our ultimate aim is to build a simulation of whole ice sheet growth and decay incorporating changes in ice thickness and flow geometry and tracking successive ice-marginal positions. This is being achieved using the mapped landform data along with chronological data (Hughes et al. 2016), glacio-isostatic constraints and other constraints from the literature and comparing them with ice sheet modelling simulations using PISM (Winkelmann et al. 2011). We focus on using identified empirical changes in ice flow geometry (from the landforms) to choose between dozens of alternate ensemble ice sheet model simulations. The challenge is to build a three-dimensional simulation of ice sheet evolution that is physically well-founded that satisfies most of the flow geometry changes, and fits within empirically defined ice marginal positions.

 

References

Johnson, M.D., Fredin, O., Ojala, A.E.K., Peterson, G., 2015: Unraveling Scandinavian geomorphology: the LiDAR revolution. GFF 137, 245-251.

Hughes, A.L.C., Gyllencreutz, R., Lohne, Ø.S., Mangerud, J., Svendsen, J.I., 2016: The last Eurasian ice sheets--a chronological database and time-slice reconstruction, DATED-1. Boreas 45, 1–45.

Winkelmann, R., Martin, M.A., Haseloff, M., Albrecht, T., Bueler, E., Khroulev, C., Levermann, A., 2011: The Potsdam parallel ice sheet model (PISM-PIK)--Part 1: Model description. The Cryosphere 5, 715–726.

How to cite: Clark, C., Ely, J., Hughes, A., Archer, R., Boyes, B., Butcher, F., Dewald, N., Diemont, C., Dulfer, H., and Bradley, S.: A landform-driven simulation of deglaciation of the Scandinavian Ice Sheet and the PalGlac project’s progress on data-modelling integration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6044, https://doi.org/10.5194/egusphere-egu24-6044, 2024.

14:30–14:40
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EGU24-15554
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ECS
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On-site presentation
Kaleb Wagner, Lotta Ylä-Mella, Martin Margold, Mads Faurschou Knudsen, Freek Busschers, Marcel Bakker, Birte Lindahl Eriksen, Jesper Olsen, Jane Lund Andersen, and John Jansen

In Northwest Europe, the earliest presence of the Fennoscandian Ice Sheet (FIS) is registered in the Dutch-German border region, where fluvio-deltaic sediments of the ancient Eridanos river system contain weathered Nordic erratics within the so-called “Hattem Beds” (Upper Pieze Fm. [f.k.a. Lower member of the Enschede Fm.]). The Eridanos operated from the Early Miocene, integrating drainage across the east Fennoscandian Shield and Baltic Platform, until its headwaters were overridden by the FIS for the first time. The Hattem Beds, conventionally attributed to the Dutch Menapian Stage (~MIS 34; 1.1 Ma), mark the onset of glacial erosion within the Baltic Basin and termination of the Eridanos system.

Here we provide new sediment burial ages for this key stratum by exploiting the cosmogenic 10Be-26Al pair in quartz. We measure nuclide concentrations in archived drill-core samples obtained from the type locality at the Wapenveld quarry near Molenweg (NL), including those of the overlying Urk and underlying Lower Pieze Fms. (f.k.a. Harderwijk Fm).

Results with our Particle Pathway Inversion of Nuclide Inventories (P-PINI) burial dating model suggest a significantly older age for the Upper Pieze Fm. than has been previously inferred, underscoring glacial incision of the Baltic Basin and collapse of the Eridanos river system beginning in the Early Pleistocene (~2 Ma). This initial advance of the FIS into the Baltic Basin tracks the overall intensification of Northern Hemisphere glaciation indicated by marine records and alludes to the expansion of European ice masses prior to the Middle Pleistocene Transition (MPT; ~1.2–0.8 Ma). These findings add to a growing sense of mismatch between large empirically-derived pre-MPT ice sheet extents and low coeval glacial-interglacial ice volumes implicit in the global δ18O record.

How to cite: Wagner, K., Ylä-Mella, L., Margold, M., Faurschou Knudsen, M., Busschers, F., Bakker, M., Lindahl Eriksen, B., Olsen, J., Lund Andersen, J., and Jansen, J.: Early Pleistocene onset of glacial incision in the Baltic Basin revealed by 10Be-26Al burial dating of the Hattem Beds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15554, https://doi.org/10.5194/egusphere-egu24-15554, 2024.

14:40–14:50
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EGU24-13494
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ECS
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On-site presentation
Raphael Gromig, Brent Ward, Jeff Bond, Rene Barendregt, and Tibor Dunai

Yukon Territory has been repeatedly affected by the northern Cordilleran Ice Sheet during the last 2.6 million years, which has significantly affected the landscape. Yukon is unique in Canada in that it has three broad mappable chrono-geomorphic regions representing regionally coherent advances of the northern Cordilleran Ice Sheet and, unlike all other parts of Canada, a large unglaciated area. The oldest surface is a composite of several glaciations that are so old individual limits cannot be resolved. The oldest of these glaciations has occurred 2.6 million years ago and is believed to be responsible for shifting the route of the Yukon River.

Geological evidence suggests that the Yukon River, which now flows in northern/western direction into the Bering Sea, was initially flowing south into southwest Yukon and west into the Tanana River basin. Reversal of the Yukon River is believed to be a consequence of the onset of Northern Cordillera glaciations at the beginning of the Quaternary period. Glaciation of the St. Elias Mountains blocked the passage of the paleo-Yukon River and formed a glacially dammed lake. This lake covered an extensive area in central Yukon and then catastrophically drained after overtopping a threshold north of Dawson City. This formed the present route of the Yukon River flowing to the Bering Sea. The presence and timing of the formation of Glacial Lake Yukon has been subject of debate for several decades. However, this hypothesis was widely accepted despite the absence of physical evidence for the glacial lake.

The first physical evidence of Glacial Lake Yukon was discovered in 2022 when a succession of lake sediments was exposed in a placer mining operation in the Bonanza Creek Valley (tributary of the Klondike River) at the Lovett Hill site. The sampled section comprises more than 8 m of clays, silts and sands. This section is underlain by the Pliocene ‘White Channel gravel’, and the Quaternary Klondike outwash, with the latter representing first evidence of Quaternary glaciation in the Yukon. The lake sediment succession is overtopped by an erosive gravel unit, which likely marks the drainage of the lake.

In order to refine the regional glacial stratigraphy, we utilize a multidisciplinary approach to provide chronological control on the formation of Glacial Lake Yukon. This allows us to test the hypothesis that the reversal of the Yukon River and the formation of Glacial Lake Yukon are associated with the first large Cordilleran Ice Sheet. We combine paleomagnetic measurements and cosmogenic 26Al–10Be isochron dating. In addition, we test the utility of cosmogenic krypton on zircon grains in this setting. Initial paleomagnetic data indicate the lake sequence is reversely magnetized; this combined with a previous burial age of ca. 2.6 Ma for the initiation of Klondike outwash deposition, suggests deposition of the lake sediments during the Matuyama Chron (0.78 to 2.6 Ma). Cosmogenic nuclide data will further refine this age.

How to cite: Gromig, R., Ward, B., Bond, J., Barendregt, R., and Dunai, T.: First evidence and dating of Glacial Lake Yukon using paleomagnetic dating and cosmogenic nuclides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13494, https://doi.org/10.5194/egusphere-egu24-13494, 2024.

14:50–15:00
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EGU24-4704
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ECS
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On-site presentation
Alexander Sodeman and Tracy Brennand

Subglacial hydrology has been shown to significantly influence ice sheet dynamics in both Greenland and Antarctica.  Though direct observation and study of the subglacial hydrological network is limited by the presence of thick overlying ice, insights into subglacial hydraulics can be gained by studying landforms derived from meltwater in deglaciated landscapes.  Murtoos and meltwater corridors are examples of meltwater derived landforms, the former being triangular-shaped hills flanked by shallow troughs, and the latter being broad, shallow landforms with clear erosional boundaries and distinct internal morphologies.  While meltwater corridors have been previously identified in British Columbia, this study represents the first identification and study of murtoos associated with the Cordilleran Ice Sheet.  We identified a large network of murtoos and meltwater corridors in south-central British Columbia and studied both the morphology and internal composition of both landform groups using high resolution elevation data and near surface geophysical surveys. Electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys on different murtoos reveal a homogeneous internal composition of sandy diamicton, while the troughs lateral to murtoos contain sorted sediment.  We interpret the murtoos as subglacial meltwater erosional remnants, their morphology determined by meltwater erosion of the lateral troughs.  The meltwater corridors studied contain two distinct morpho-stratigraphic relationships: channelized reaches exhibiting shallow intersecting and/or parallel troughs floored by sandy diamicton, the residuals resembling glacial curvilineations; and flat bed reaches with narrow eskers composed of fine sand and gravel.  We interpret the channelized and flat bed reaches as being formed by subglacial meltwater erosion and deposition, respectively, with the switch in process and form being determined by bed topography.  Together, these landforms suggest extremely wet-bed conditions during deglaciation of the Cordilleran Ice Sheet, with widespread subglacial meltwater erosion and deposition.  These observations provide insight into the likely conditions beneath portions of the Greenland and/or Antarctic ice sheets where widespread meltwater production has been reported, such as the western land terminating portion of the Greenland Ice Sheet.

How to cite: Sodeman, A. and Brennand, T.: Morphology and Composition of Murtoos and Meltwater Corridors Associated with the Cordilleran Ice Sheet in South-Central British Columbia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4704, https://doi.org/10.5194/egusphere-egu24-4704, 2024.

15:00–15:10
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EGU24-14426
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Highlight
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On-site presentation
Martin Margold, Benjamin J. Stoker, Helen E. Dulfer, Chris R. Stokes, Victoria H. Brown, Christopher D. Clark, Colm Ó Cofaigh, David J.A. Evans, Duane Froese, and Sophie L. Norris

The northwestern sector of the Laurentide Ice Sheet drained ice from the Cordilleran-Laurentide ice saddle and the Keewatin ice dome towards the ice margin on the arctic continental shelf during its late local Last Glacial Maximum. The glacial geomorphological and geological record of the region documents several massive palaeo-ice streams. However, the deglacial dynamics of this sector has not yet been reconstructed in detail and questions remain about the nature of deglaciation in this region: Did ice streams operate far up-ice or were they limited to a rather narrow ice-margin zone? Was ice stagnation widespread?

We reconstruct the deglaciation of the northwestern sector of the Laurentide Ice Sheet by glacial geomorphological inversion methods, based on our recent regional-scale mapping of the glacial geomorphological record. We find that the ice stream network evolved from large, marine-terminating ice streams to shorter, terrestrial ice streams. The ice drainage network experienced a reorganisation following the disappearance of the Cordilleran-Laurentide ice saddle, which previously feed ice in a northerly direction along the modern-day Mackenzie River, to more westerly ice flow sourced from the Keewatin ice dome. Deglaciation was dominated by dynamic ice retreat but we also find traces of localized ice stagnation in areas of higher ground fringing the major fast ice flow corridors. The ice flow pattern changed markedly once the ice front stepped back onto the Canadian Shield, where ice streaming largely ceased. This empirical reconstruction, fitted to the latest version of ice margin chronology, can serve as validation for numerical modelling efforts and provides information on broad-scale ice sheet dynamics during the last deglaciation. 

How to cite: Margold, M., Stoker, B. J., Dulfer, H. E., Stokes, C. R., Brown, V. H., Clark, C. D., Ó Cofaigh, C., Evans, D. J. A., Froese, D., and Norris, S. L.: Reconstructing the deglacial dynamics of the northwestern Laurentide Ice Sheet , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14426, https://doi.org/10.5194/egusphere-egu24-14426, 2024.

15:10–15:20
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EGU24-7690
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ECS
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On-site presentation
Katharina Streuff, Nina-Marie Lešić, Gerhard Kuhn, Miriam Römer, Sabine Kasten, and Gerhard Bohrmann

In an effort to elucidate an important part of the Quaternary evolution of sub-Antarctic South Georgia, hydroacoustic data from its southern continental shelf are presented. The island with its surrounding shelf is of key interest for climate reconstructions, because it is located within the core belt of the Southern Westerlies and between the main fronts of the Antarctic Circumpolar Current in the Southern Ocean. This makes it particularly susceptible to changes in climate conditions on a local, regional, but also Southern Hemisphere-wide scale.

The data provide new insights into the glacial evolution of the King Haakon Trough, one of several cross-shelf trough systems around the island. Numerous landforms, identified from high-resolution bathymetry data, document phases of ice advance and retreat. They are interpreted to be related to the confluence of two major trunk glaciers fed by an extended, possibly warm-based, South Georgia Ice Cap. Linear bedforms become progressively elongated towards the shelf and imply accelerated ice flow and/or softer sediment substrate towards the shelf edge. In contrast, recessional moraines and large morainal banks not only evidence shelf-wide ice extent during a peak glaciation, but also attest to staggered retreat, at least during the initial phase of deglaciation. The establishment of a complex bottom-current system around the onset of the last deglaciation is implied by the presence of moats and contourite drifts, which are mainly recorded in sub-bottom profiler data from the trough system. These data also show an acoustically semi-transparent facies of variable thickness present on the mid- and outer shelf as basal trough fill, which, on the basis of its acoustic appearance and the presence of several strong internal reflectors, is interpreted as a sequence of stacked glacial tills. These are similar to stacked tills previously documented from the Antarctic Peninsula and probably document a minimum of three extensive ice advances around South Georgia. Because the tills in the King Haakon Trough occur over a distance of ~26 km across the shelf, it is postulated that they derive from a minimum of three separate glaciations, rather than from re-advances within one glaciation period. Accordingly, the new findings from the combined bathymetry and sub-bottom profiler data show that the marine-geological archives around South Georgia offer unique potential to constrain how ice masses in the Southern Ocean responded to Quaternary climate change.

How to cite: Streuff, K., Lešić, N.-M., Kuhn, G., Römer, M., Kasten, S., and Bohrmann, G.: Glacial history of the King Haakon Trough System, sub-Antarctic South Georgia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7690, https://doi.org/10.5194/egusphere-egu24-7690, 2024.

15:20–15:30
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EGU24-12152
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ECS
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On-site presentation
Shannon Klotsko, Rob Hatfield, Brendan Reilly, Alan Mix, Anne Jennings, Erin Gregory, Joe Stoner, Maureen Walczak, Jonas Donnenfield, Cara Fritz, Alice Hough, Robert Kelleher, Lindsay Monito, Paloma Olarte, Megan Siragusa, Katherine Stelling, and Tobias Vonahme

In summer 2023, the Baffin Bay Deglacial Experiment (BADEX) completed a 33-day cruise focused on the west Greenland margin; the overarching goal of this project is to investigate the evolving ocean and ice conditions along the west Greenland ice sheet from the last glacial maximum through the deglaciation. The cruise collected seafloor and sub-seafloor data, as well as water and plankton samples, with the aim of establishing 1) the timing and extent of warm Atlantic water incursion along the north-western Greenland margin; 2) the phasing of the initial ice margin retreat relative to oceanic and atmospheric changes; 3) the role of local or regional ice shelves in buttressing trough-bound outlet glaciers; and 4) the influence of regional geology, geomorphology, and ice dynamics on ice-margin retreat. Here, we present results from the ~600 km of new multibeam sonar data collected on the slope just north of the Melville Bugt trough mouth fan (TMF). The margin in this area curves landward, forming a crescent-shaped, submarine amphitheater that contains a range of bathymetric features, which vary in form with water depth and their proximity to the TMF. This includes a series of contour-following ridges that occur in depths from ~1000 to ~450 meters below modern water level. These ridges are more prominent farther away from the TMF but are more numerous closer to the trough. They are interpreted to be of glaciogenic origin, potentially formed by an ice shelf, fed by the trough, that flowed to the north and grounded on the slope. These ridges and other bathymetric features, extending up to 2000 meters water depth will be discussed. These results add to our understanding of the ice margin configuration in northern Baffin Bay during and after the last glacial period.  

How to cite: Klotsko, S., Hatfield, R., Reilly, B., Mix, A., Jennings, A., Gregory, E., Stoner, J., Walczak, M., Donnenfield, J., Fritz, C., Hough, A., Kelleher, R., Monito, L., Olarte, P., Siragusa, M., Stelling, K., and Vonahme, T.: Geomorphic evidence for along-margin ice flow from Melville Bugt slope, west Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12152, https://doi.org/10.5194/egusphere-egu24-12152, 2024.

15:30–15:40

Posters on site: Mon, 15 Apr, 10:45–12:30 | Hall X3

Display time: Mon, 15 Apr 08:30–Mon, 15 Apr 12:30
Chairpersons: Danni Pearce, Giovanni Monegato, Jürgen Reitner
X3.15
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EGU24-3491
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ECS
Arunabh Bhattacharyya, Marek Ewertowski, Jakub Małecki, and Gisela Domej

The response of glacial masses to climate change is well documented. However, the impact of landslides on glacier dynamics and stability requires greater research. Landslides in glacierized mountains can be caused by climate change (e.g. permafrost thawing), intense precipitation, paraglacial response of slopes or earthquakes and can, in turn, limit ablation, increase meltwater production and alter glacier velocities. Besides, landslides can be hazardous to life and infrastructure. Permafrost degradation, de-buttressing of slopes, extreme precipitation and freezing and thawing cycles make mountain glaciers susceptible to instability and cascading hazards. Our project thus focuses on identifying the research gaps associated with landslide-glacier dynamics and related hazards. The two components of our project are 1) Remote sensing and GIS and 2) Modelling. Different spatial scales (landform, catchment, global) will be considered for our research.

This presentation aims to outline PhD project and discuss proposed approaches with the glaciological, geomorphological, and remote sensing community. A literature review aimed at generating an inventory of landslide-affected glaciers globally is the first step. This will be complemented by detailed analyses and quantification of landslide-induced changes in glaciers’ behaviour by selecting benchmark case studies across different glacial systems representing different environmental conditions. Acquiring UAV data (0.05-0.10 m), high resolution (0.3-1.0 m) (Pleiades, WorldView, etc.), and medium resolution (10-50 m) satellite imagery (Landsat, Sentinel, Aster) will be essential for the quantification of changes in glaciers velocity and mass balance. We also plan field visits to benchmark glaciers to ground-truth remote sensing data and collect information about sedimentological and geomorphological characteristics of landslide deposits.

This research was funded by the National Science Centre, Poland, project number 2021/42/E/ST10/00186

How to cite: Bhattacharyya, A., Ewertowski, M., Małecki, J., and Domej, G.: Quantification of landslide-induced changes in glacier dynamics – project outline, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3491, https://doi.org/10.5194/egusphere-egu24-3491, 2024.

X3.16
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EGU24-3632
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ECS
Ethan Lee and Rachel Oien

This study presents the first palaeoglacial assessment of the mountainous terrain in the western region of the Putorana Nature Reserve, Russian Federation. This exploration, the first of its kind in this region, focuses on approximately 200 cirques, utilising cirque floor altitudes as a proxy for Equilibrium Line Altitudes (ELAs) as a pivotal palaeoclimate indicator. The primary objective is to gain unprecedented insights into the last glacial advancement in the area and to contribute to our understanding of the palaeoclimate during the potential Last Glacial Maximum (LGM) in Russia.

Employing the Ohmura equation, this research aims to construct a comprehensive palaeo climate profile, with ELAs estimated from cirque floor altitudes. These cirques are systematically mapped using the 10 m Arctic DEM and reconstructed using the GlaRe tool. Additionally, the physical parameters of the cirques will be rigorously evaluated using the newly developed ACME2.0 tool. By concentrating on the last glacial advancement, this study seeks to provide valuable information about the palaeoclimatic conditions and glacial dynamics within the Western Putorana Nature Reserve. This offers the first insights into the understanding of the mountain glacial history of the region.

How to cite: Lee, E. and Oien, R.: Insights from Cirque Floor Altitudes in the Western Putorana Nature Reserve, Russian Federation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3632, https://doi.org/10.5194/egusphere-egu24-3632, 2024.

X3.17
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EGU24-4566
Jürgen M. Reitner and John Menzies

Knowledge of subglacial conditions is of great relevance in understanding glacier dynamics. A combination of micro- and macrosedimentological analysis of diamictons and deformation structures can form the basis for the reconstruction of past subglacial conditions. We present the results of such a study on subglacial tills, within an Alpine environment, at Einödgraben in the Kitzbühel Alps (Tyrol/Austria). The Late Pleistocene succession there (MIS 5d-MIS 2) shows great diversity in facies from wood-bearing alluvial to glaciolacustrine to subglacial deposits. Two glaciogenic diamictons (tills) within the sequence were analysed at the microscale and are correlated to the Last Glacial Maximum (LGM; Würmian Pleniglacial) and the early Lateglacial phase of ice decay. The first deformation phase of pre-LGM deposits occurred most likely in a subglacial setting close to the advancing glacier margin and resulted in diapir-like glaciotectonic macro-structures, which are unique for an inneralpine area. Subglacial erosion over these structures occurred and later pre-LGM emplaced deposits underwent deformation and partial homogenisation immediately beneath the glacier base leading to diamictons, indicative of subglacial deformable bed conditions. The tills of the LGM and the Würmian Lateglacial show a range of microfacies and deformation structures evidence of close and rapid changes in till rheology and stress field dynamic in the subglacial environment. Our study demonstrates the need for a reinvestigation of deposits occurring in the proximity of past active ice interfaces. The paleoglaciological evidence assembled from the detailed and spatially close research on the microsedimentology of till at Einödgraben reflects our increasing comprehension and understanding of till microsedimentology in Alpine environments. An awareness is also shown of the need for much further research on the glacial depositional mechanics in mountainous terrains that are different from those in the immense lowland plains of the extensive paleo-ice sheets of North America and Northern Europe.

How to cite: Reitner, J. M. and Menzies, J.: Till formation and subglacial deformation in a stratigraphic complex Late Pleistocene sequence (Einödgraben / Aurach, Kitzbühel Alps, Austria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4566, https://doi.org/10.5194/egusphere-egu24-4566, 2024.

X3.18
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EGU24-6551
Colm O'Cofaigh, Dave Roberts, S. Louise Callard, Jerry Lloyd, Georgia Ware, Katharina Streuff, Stewart Jamieson, Boris Dorschel, and Torsten Kanzow

Marine geophysical data combined with radiocarbon dated sediment cores provide a record of the advance and retreat of the ancestral Northeast Greenland Ice Stream (NEGIS) across the continental shelf offshore of NE Greenland during the last glaciation. Today, NEGIS is the largest ice stream to drain the Greenland Ice Sheet (GrIS), holding a sea-level equivalent of 1.1-1.4 m. However, the longer-term history of the ice stream, especially on the adjoining outer continental shelf has, to date, been poorly constrained. Streamlined subglacial landforms record grounded ice flow in the outer shelf section in cross shelf bathymetric troughs, with mega-scale glacial lineations recording former streaming flow towards the shelf edge. Flow transverse landforms in the form of downlow-tapering, sediment wedges occur at the shelf edge and on the outer-mid shelf of the bathymetric troughs. These landforms differ in their morphology from the classic ‘ramp-step’ form of typical grounding wedges but are similarly interpreted as a form of grounding-zone wedge in which sediment prograded and thinned away from the grounding-zone. The wedges record a shelf-edge terminating, grounded ancestral NEGIS, as well as the subsequent episodic retreat of the ice stream inshore during deglaciation. Beyond the shelf edge, glacigenic debris flows imaged on acoustic stratigraphic profiles and recovered in sediment cores document sediment delivery onto the slope; such deposits are typical of submarine slopes offshore of shelf-edge terminating palaeo-ice streams. On the outer shelf subglacial tills and grounding-zone proximal sediments overlain by deglacial stratified glacimarine sediments record ice stream advance and retreat in the troughs. Radiocarbon dates from glacimarine sediments in these cores indicate early deglaciation from the shelf edge but with relatively slow rates of subsequent ice-stream retreat across the outer shelf.

How to cite: O'Cofaigh, C., Roberts, D., Callard, S. L., Lloyd, J., Ware, G., Streuff, K., Jamieson, S., Dorschel, B., and Kanzow, T.: Geomorphological and sedimentological records of Greenland Ice Sheet advance and retreat on the continental shelf offshore of NE Greenland during the last glaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6551, https://doi.org/10.5194/egusphere-egu24-6551, 2024.

X3.19
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EGU24-9282
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ECS
Sarah Kamleitner, Tancrède P. M. Leger, Susan Ivy-Ochs, Samuel U. Nussbaumer, Andreas Vieli, and Guillaume Jouvet

Latest advances in numerical modelling using machine learning sped-up glacier models by several orders of magnitude, thus facilitating glacier evolution models to run at high resolutions (hundreds of metres) over timescales of several tens of millennia and over mountain range scales. The RECONCILE project seeks to use the Instructed Glacier Model (IGM) to simulate the maximum state and deglaciation of the last glaciation of the European Alps and to test model output against the geological record. A robust framework against which to test Alps-wide and transient paleoglacier model simulations is however missing. Despite the long history of Quaternary research in the Alps and abundant publications on the topic, the integration of field evidence for model validation has thus far largely been restricted to the Last Glacial Maximum (LGM) ice extent. Inspired by work on the (former) British, Fennoscandian, Patagonian and Greenland ice sheets, we aim to build a comprehensive and standardized dataset on paleoglacier variations for the European Alps. Coupling geo(morpho)logical data and geochronological markers, the AlpIce database will act as an empirical basis for future quantitative model-data comparisons. Published empirical evidence that restrains the build-up, culmination, and disintegration of the Alpine LGM glaciers as well as subsequent Alpine Lateglacial and Holocene glacier advances are considered. Relevant surface exposure and radiocarbon datings are currently gathered and fed into the database. Data reliability assessments and paleoglaciological context classifications are undertaken concurrently. The database structure also allows the inclusion of additional chronological methods (e.g. luminescence dating, dendrochronology, archeological and historical sources) into AlpIce. Where applicable, the chronological constraints will be linked to related geo(morpho)logical features (e.g. former ice margins, trimlines) using GIS software. AlpIce is designed as an open-access resource hoping to prove useful for both empirical and modelling communities and beyond the scope of model validation.

How to cite: Kamleitner, S., Leger, T. P. M., Ivy-Ochs, S., Nussbaumer, S. U., Vieli, A., and Jouvet, G.: AlpIce - Towards an Alps-wide database of empirical geo(morpho)logical and geochronological data constraining Last Glacial Maximum to Holocene glacier fluctuations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9282, https://doi.org/10.5194/egusphere-egu24-9282, 2024.

X3.20
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EGU24-10169
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ECS
Anna Grau Galofre and Axel Noblet

The glacial hydrology and stability to sliding episodes of the Greenland Ice Sheet (GIS) are closely linked to the subglacial drainage capacity of its bed, which depends on its structure and connectivity. The central-western portion of the GIS, specifically in the region around Kangerlussuaq, is characterized by subglacial drainage systems consisting on meltwater-filled cavities on a hard bed (Harper et al., 2017), which may become interconnected following episodes of increased discharge. Episodes of connectivity following high pressure subglacial meltwater events may lead to enhanced sliding followed by channelization, and emplacement of subglacial floods (Harper et al., 2017).

We present preliminary field and remote sensing observations describing the morphology, topology, organization, and other field characteristics of recently exposed elements of the glacial hydrology system, which were emplaced by the western margin of the GIS. Our field site is located by the Europlanet Transnational Access TA1 Facility 4: Greenland-Kangerlussaq, which offers a unique opportunity to study the subglacial drainage patterns in this region (Carrivick et al., 2016). Few regions in the world offer the opportunity to study recently emplaced, well exposed subglacial morphologies at the level of accessibility of this site. Field data includes in situ-imagery, observations of glacial sliding directions, description of sedimentary deposits, morphology, scale and characteristics of subglacial cavities, and nature of the connection passages. Data acquired in the field is complimented with remote sensing data from the ArcticDEM and Maxar imagery.

We conclude with a discussion of the implications of our observations for the geometry and volumetric capabilities of currently active subglacial hydrology pathways under the western portion of the GIS, including addressing the possible modes of meltwater drainage from the observed morphologies and subglacial geological reconstructions (e.g., White et al., 2016), as well as a comparison of the morphology and geometry of observed interconnected subglacial cavities to morphologically and topologically similar systems located at the east of Hellas Basin on Mars. 

How to cite: Grau Galofre, A. and Noblet, A.: Field observations of interlinked subglacial cavities in Kangerlussuaq - Greenland ice sheet western margin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10169, https://doi.org/10.5194/egusphere-egu24-10169, 2024.

X3.21
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EGU24-11008
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ECS
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Rosie Archer, Jeremy Ely, Timothy Heaton, Frances Butcher, Anna Hughes, and Chris Clark

Past ice flow direction can be inferred through mapping of subglacial lineations (e.g. drumlins and mega-scale glacial lineations). A numerical ice sheet model can also be used to reconstruct possible ice flow directions according to ice physics. These two methods are rarely integrated to see if the model can explain the observational data. Previous model-data comparison workflows made a large step forward. However, they lack statistical rigour and certain capabilities, such as comparing an ensemble of model simulations. To overcome these challenges, we created the Likelihood of Accordant Lineations Analysis (LALA) tool.  LALA is a tool to compare numerical model ice sheet simulations to observational data of past flow direction. LALA was created to take a step forward in improving model-data comparisons; making comparisons statistically rigorous and adding the ability to directly grade multiple simulations against each other, a feature that was missing from previous tools. For this poster, we show an example of the tool in action and use LALA to compare model simulations of the British-Irish ice sheet and observations of flow direction from subglacial lineations taken from the BRITICE-CHRONO project. We present the best and the worst fitting simulations according to LALA. We also dissect the score produced to give an indication of the flow directions which are most (and least) regularly matched by the numerical modelling. These results highlight opportunities for model development and the potential to reevaluate observations.

How to cite: Archer, R., Ely, J., Heaton, T., Butcher, F., Hughes, A., and Clark, C.: Application of a new statistically rigorous comparison tool of observed and modelled flow directions of the last British-Irish ice sheet over time, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11008, https://doi.org/10.5194/egusphere-egu24-11008, 2024.

X3.22
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EGU24-11858
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ECS
Rachel Oien and Bartosz Kurjanski

This study employs Arctic DEM data and GIS tools, ACME 2.0 (Li et al., 2024), and GlaRe (Pellietero et al., 2016), to systematically investigate cirques in the western islands off central Greenland. The primary objective is to reconstruct past Equilibrium Line Altitude (ELA) variations at the end of the Younger Dryas period and derive insights into palaeoclimate conditions in this region.

By leveraging high-resolution Arctic DEM datasets and advanced GIS methodologies, we analyse cirque morphologies and elevations to reconstruct ELAs, a key indicator of glacial development and climate conditions. The Younger Dryas, a well-documented, abrupt and relatively short climatic event, represents a critical period for understanding past climate dynamics and their impact on glacial landscapes on a timescale relevant to the contemporary human population.

Our approach combines the semi-automated extraction of cirque parameters from the Arctic DEM with GIS-based modelling to reconstruct palaeo-ELA variations. Through spatial and temporal analysis, we aim to discern patterns of glacial response to climatic shifts between 13-9.5ka (Leger et al., 2024), shedding light on the sensitivity of Arctic cirques to rapid environmental changes.

Preliminary results indicate distinct patterns in cirque morphology and ELAs consistent with variations in the ELA during the Younger Dryas. These findings contribute to a more comprehensive understanding of the regional impact of past climatic events on the Greenlandic glacial landscape. This research enhances our knowledge of the Younger Dryas climate dynamics in the western islands off Greenland, providing valuable insights into the region's palaeoclimate history and contributing to broader discussions on Arctic environmental change.

How to cite: Oien, R. and Kurjanski, B.: Geomorphological Analysis of Cirques in the Western Islands of Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11858, https://doi.org/10.5194/egusphere-egu24-11858, 2024.

X3.23
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EGU24-11985
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ECS
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Highlight
Léa Rodari, Audrey Margirier, Georgina King, Ann Rowan, Christoph Schmidt, and Guillaume Jouvet

Significant mass loss and increased rock debris cover have been observed across many mountain glaciers due to climate change. However, the dynamics of sediment transport through alpine glaciers are not fully understood and should be investigated to better constrain the future evolution of mountain glaciers under a changing climate. Englacial sediment transport is difficult to observe and to that end, we quantify the englacial transport time of debris within a glacier using a novel method combining luminescence rock surface burial dating and ice-flow modelling. Our study focuses on Mer de Glace, Mont Blanc Massif, French Alps, where supraglacial debris has expanded over the past 20 years.

We collected near-surface rock debris (4–22 cm in diameter) of granite from the ablation area of Mer de Glace that we expect to have experienced different englacial transport durations. Under subdued red light, we cored the samples perpendicular to their surfaces and sliced the cores into ~1 mm discs for luminescence dating. We first evaluated whether the luminescence signals had been well bleached prior to deposition by measuring the evolution of luminescence signals with depth throughout the core (i.e. measurement of the bleaching plateau). We used a protocol comprising infra-red stimulation at 50 °C and 225 °C, followed by blue stimulation at 125 °C to explore the signals of different minerals with different luminescence properties. Of the 29 samples investigated, 20 were well bleached, exhibiting a clear plateau in luminescence signals with depth (following the approach of Rades et al., 2018). We are currently using a single-aliquot regenerative dose protocol to date the rock surfaces of these samples to obtain englacial transport durations. In the next step, we will contrast the englacial transport durations measured using luminescence with those predicted using the ice-flow model IGM (Jouvet et al., 2022), allowing us to better understand the dynamics of mountain glaciers over centennial to millennial time scales.

 

References

Jouvet, G., Cordonnier, G., Kim, B., Lüthi, M., Vieli, A., & Aschwanden, A. (2022). Deep learning speeds up ice flow modelling by several orders of magnitude. Journal of Glaciology68(270), 651-664.

Rades, E. F., Sohbati, R., Lüthgens, C., Jain, M., & Murray, A. S. (2018). First luminescence-depth profiles from boulders from moraine deposits: Insights into glaciation chronology and transport dynamics in Malta valley, Austria. Radiation Measurements120, 281-289.

How to cite: Rodari, L., Margirier, A., King, G., Rowan, A., Schmidt, C., and Jouvet, G.: Luminescence rock surface dating of englacial transported debris from Mer de Glace glacier, French Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11985, https://doi.org/10.5194/egusphere-egu24-11985, 2024.

X3.24
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EGU24-12758
Zsófia Ruszkiczay-Rüdiger, Zoltán Kern, Balázs Madarász, Petru Urdea, Régis Braucher, Mihály Molnár, Botond Búró, and Aster Team

The presence of cosmogenic radionuclide concentrations inherited from previous exposure(s) of glacially transported boulders and moulded bedrock surfaces may hinder the determination of the surface exposure age (SED) of the last phase of (de)glaciation.

A previous study revealed that glacial landforms of the cirque area in the southern side of the Retezat Mountains (Southern Carpathians, Romania) hold significant amount inherited 10Be (t1/2=1.4 My), which was used for a tentative estimation of the amount of glacial erosion, assuming that the lowest 10Be concentration was representative of the true age of deglaciation (Ruszkiczay-Rüdiger et al., 2021, Geomorphology 384, 107719).

In this study, a western valley, the Zlătuia-Dobrunu valley of the Retezat Mts was sampled for 10Be SED. The novel data are in agreement with the previous datasets suggesting that the most extended glaciers belonged to the Last Glacial Maximum. However, the old apparent exposure durations based on 10Be analysis of samples from the cirque area provided firm evidence for the presence of excessive abundances of cosmogenic 10Be in this valley as well.

The use of the short-lived in situ produced 14C (t1/2= 5.7 ky) provides an independent age constraint for the timing of the last deglaciation, because all 14C inventories that might be inherited from a previous exposure would have already been decayed. As a consequence, the 14C concentrations are not biased by inheritance, thus i) enable the age determination of the landforms belonging to the last phases of deglaciation and ii) the 14C exposure ages compared to the 10Be data will allow an assessment of the inherited amount of 10Be and thus a more precise determination of the amount of glacial erosion.

In this study the new 10Be and 14C SED ages will be presented together with the mapped glacial landforms, reconstructed paleoglaciers and their Equilibrium Line Altitudes.

Funding: NKFIH FK124807, INSU/CNRS, ANR - “EQUIPEX Investissement d’Avenir”, IRD and CEA, the PNRR-III-C9-2022 - I8, no. 760055/23.05.2023, CF 253/29.11.2022. and Horizon 2020 grant 871149 ”EUROPLANET”.

How to cite: Ruszkiczay-Rüdiger, Z., Kern, Z., Madarász, B., Urdea, P., Braucher, R., Molnár, M., Búró, B., and Team, A.: New surface exposure age data using cosmogenic radionuclides 10Be and 14C to constrain the age of the last deglaciation in the Retezat Mts, Southern Carpathians, Romania, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12758, https://doi.org/10.5194/egusphere-egu24-12758, 2024.

X3.25
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EGU24-13860
Levan Tielidze, Shaun Eaves, Kevin Norton, Andrew Mackintosh, and Alan Hidy

I present the first dataset of Late Quaternary glacial maximum extent and deglaciation along with quantitative paleoclimate reconstructions from the Ahuriri River valley, Southern Alps, New Zealand. The new constraints based on geomorphological mapping and sixty-six cosmogenic 10Be surface exposure ages offer the opportunity to test hypotheses about the climate system, to better understand the processes that drove ice retreat and readvance during the Last Glacial Maximum and the subsequent glacial termination.

Reconstructions of past glacier geometries indicate that the local ELA was depressed by ~880 m and climate was 5±1 °C colder than present (1981–2010) at 19.8±0.3 ka, while ELA was depressed by ~770 m and climate was 4.4±0.9 °C colder at 16.7±0.3 ka. Subsequent estimations suggest ELA elevations at 14.5±0.3 ka, 13.6±0.3 ka, and 12.6±0.2 ka were ≤700 m, ≤630 m, and ~360 m lower than today. This equates to air temperatures of ≤3.9 °C, ≤3.5 °C, and 2.3±0.7 °C colder than today, assuming no changes in past precipitation.

The small amount of warming estimated in this study between 19.8±0.3 and 16.7±0.3 ka differs somewhat from glacial reconstructions in other major valleys in the Southern Alps, specifically from Rakaia River valley. Robust constraints of glacier changes in the Ahuriri valley between 14.5±0.3 and 12.6±0.2 ka confirm that an early glacier readvance occurred in New Zealand at this time, which has been previously recognised with only limited evidence. The reconstructed ELA suggests that the coldest part of the Late Glacial reversal occurred at 14.5±0.3 ka. 

How to cite: Tielidze, L., Eaves, S., Norton, K., Mackintosh, A., and Hidy, A.: Late Quaternary glacier-climate reconstruction in the Ahuriri River valley, Southern Alps of New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13860, https://doi.org/10.5194/egusphere-egu24-13860, 2024.

X3.26
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EGU24-15483
Giovanni Monegato, Lukas Rettig, Sandro Rossato, Sarah Kamleitner, Susan Ivy-Ochs, Alessia Modesti, Francesco Gosio, Mirko Demozzi, Matteo Rinaldo, Enrico Marcato, Tommaso Trentini, Silvana Martin, and Paolo Mozzi

During the Last Glacial Maximum the Valsugana sector in the south-eastern European Alps was characterized by an extensive glacier network that included the large valley glacier belonging to the Adige glacier, through the transfluence in the Fersina area, and major tributaries from the Calamento and Cavè valleys. The glacier surface reached up to 1400 m a.s.l. in the western sector of the study area with a downstream gentle slope to the east. At Borgo Valsugana, the trunk glacier merged with several tributaries and flowed also towards the Tesino plateau to the east, where it merged with the tributary valley glacier. In the Tesino area, the glaciers flowed mainly to the south towards the major trunk glacier. This flowed downstream until Primolano, where the narrow reach of Canal del Brenta dammed its flow. The gorge promoted the bulging of the glacier front and its split into two lobes: the first to the south formed the lateral moraines of Enego and Col del Gallo ending with a seracs cascade; the second lobe to the east merged with the Cismon-Piave glacier. This latter was a major ice-field originated in the central Dolomites and reached its western frontal position above the Corlo gorge (Rossato et al., 2018).

 In this articulate network several nunataks remained ice-free; here, lateral moraines with erratic boulders mark the elevation of the trimline. At Mt. Lefre, three boulders were dated to the LGM with exposure dating method (10Be). These are the first exposure ages for an LGM glacier in the south-eastern Alps and can be compared to radiocarbon chronologies from other glaciated valleys

In the study area also independent glaciers (Mt. Agaro, Mt. Coppolo, Mt. Cavallara) developed. In the Prealps the large Altopiano dei Sette Comuni plateau glacier had a calculated Equilibrium Line Altitude (ELA) of 1680 m a.s.l. (Rettig et al., 2023), while the Monte Grappa ice cap had a calculated ELA of 1450 m a.s.l. (Baratto et al., 2003; Rettig et al., 2023). The ELA estimates allow insights into the climatic conditions under which the LGM glaciers in the Valsugana evolved.

 

References

Baratto A., Ferrarese F., Meneghel M., Sauro U. 2003. La ricostruzione della glaciazione Wurmiana nel Gruppo del Monte Grappa (Prealpi Venete). In: Biancotti, A., Motta, M. (Eds.), Risposta dei processi geomorfologici alle variazioni ambientali. Brigati G., Genova, pp. 67–77.

Rettig L., Monegato G., Spagnolo M., Hajdas I., Mozzi P. 2023. The Equilibrium Line Altitude of isolated glaciers during the Last Glacial Maximum – New insights from the geomorphological record of the Monte Cavallo Group (south-eastern European Alps). CATENA, 107187.

Rossato S., Carraro A., Monegato G., Mozzi P., Tateo F. 2018. Glacial dynamics in pre-Alpine narrow valleys during the Last Glacial Maximum inferred by lowland fluvial records (northeast Italy). Earth Surface Dynamics, 6, 809-828.

How to cite: Monegato, G., Rettig, L., Rossato, S., Kamleitner, S., Ivy-Ochs, S., Modesti, A., Gosio, F., Demozzi, M., Rinaldo, M., Marcato, E., Trentini, T., Martin, S., and Mozzi, P.: The valley glacier network of the Valsugana (south-eastern Alps) during the LGM: Chronology and Equilibrium Line Altitudes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15483, https://doi.org/10.5194/egusphere-egu24-15483, 2024.

X3.27
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EGU24-16440
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ECS
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Highlight
Benjamin Boyes, Helen Dulfer, Nico Dewald, Frances Butcher, Chris Clark, Jeremy Ely, and Anna Hughes

Palaeo-ice sheets leave behind a landform record that we can decipher to understand glaciological processes and the responses of ice sheets to warming climates. Reconstructions of past ice sheet behaviour can inform numerical ice sheet models and are important for understanding ongoing glacio-isostatic uplift. The Scandinavian Ice Sheet, which was the largest component of the Eurasian Ice Sheet Complex during the last glaciation, glaciated Fennoscandia and northern Europe. Since the 19th Century, there has been considerable research into the deglaciation pattern of Scandinavian Ice Sheet during the last Glacial-Interglacial Transition. However, many reconstructions of retreat have been conducted at local-regional scales, which can be difficult to reconcile across ice sheet-scales, and ice-sheet scale reconstructions based on consistent approaches to mapping and data sources are rare. These inconsistencies lead to difficulties in creating ice-sheet wide reconstructions of deglaciation.

Using the glacial inversion approach, we combine our independently mapped ice marginal landforms, subglacial meltwater routes, and subglacial bedforms to produce a consistent ice sheet-scale assessment of deglaciation patterns across Norway, Sweden, and Finland. Here we present our latest version of the deglaciation pattern for the last Scandinavian Ice Sheet. This reconstruction has many similarities to previous efforts but adds significant detail. For example, in addition to overall retreat patterns, we capture instances of ice margin readvance. We also reconstruct a complex retreat pattern with the ice sheet breaking into small ice masses located within and adjacent to the Scandinavian Mountains.

How to cite: Boyes, B., Dulfer, H., Dewald, N., Butcher, F., Clark, C., Ely, J., and Hughes, A.: Deglaciation pattern of the last Scandinavian Ice Sheet across Fennoscandia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16440, https://doi.org/10.5194/egusphere-egu24-16440, 2024.

X3.28
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EGU24-16566
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ECS
Johannes Pomper, Clare Bamford, Frank Preusser, Ulrike Wielandt-Schuster, and Lukas Gegg

Overdeepenings are glacially shaped basins, incised into the bedrock deeper than the fluvial base level by subglacial erosion. Their sedimentary fillings are important archives for understanding glacial and postglacial history and the glacial impact on environmental transformation. Investigation of overdeepened features and their sedimentary contents is essential for understanding the processes and drivers of subglacial erosion, the timing and sequence of past glaciations, and accordingly their cumulated impact on landscape and topography.

This study is centred around an already acquired high quality drill core plus a correlating outcrop on the highest summit of Upper Swabia (The Hoechsten) in the North of the Lake Constance area (southwestern Germany). We investigate an overdeepening in an exceptional stratigraphic position: The sediment succession at Hoechsten is one of only a few examples of glacial basin fills that are correlated with the Early Pleistocene, and a key profile for this otherwise merely poorly constrained period. Situated in an elevated position, it is considered a component of an old highland-ramp topography that has since been largely reshaped over the course of repeated glaciations (Ellwanger et al. 2011).

Besides sedimentological analysis we apply standard geotechnical methods to reconstruct the deglaciation and potential phases of readvancement. Geotechnical data has proven valuable for the identification of a glacial sediment component, of previous mechanical loading by ice, or of the modification of a deposit by non-glacial processes. Furthermore, we compare micromorphological structures on the basis of microscale computed tomography analysis with results of a previously conducted thin-section study (Menzies & Ellwanger 2011). In the future, these analyses will be complemented by a multi-method dating approach (integrating e.g. luminescence and paleomagnetic properties and cosmogenic nuclides).

References:
Ellwanger, D., Wielandt-Schuster, U., Franz, M., & Simon, T. (2011). The Quaternary of the southwest German Alpine Foreland (Bodensee-Oberschwaben, Baden-Wuerttemberg, southwest Germany). E&G Quaternary Science Journal, 60(2/3), 306-328, DOI 10.3285/eg.60.2-3.07
Menzies, J. & Ellwanger, D. (2011). Insights into subglacial processes inferred from the micromorphological analyses of complex diamicton stratigraphy near Illmensee-Lichtenegg, Hoechsten, Germany. Boreas, 40(2), 271-288, DOI 10.1111/j.1502-3885.2010.00194.x

How to cite: Pomper, J., Bamford, C., Preusser, F., Wielandt-Schuster, U., and Gegg, L.: Early stage Quaternary overdeepening in Upper Swabia - Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16566, https://doi.org/10.5194/egusphere-egu24-16566, 2024.

X3.29
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EGU24-17599
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ECS
Andrés Castillo-Llarena, Franco Retamal-Ramirez, Jorge Bernales, Martin Jacques-Coper, Matthias Prange, and Irina Rogozhina

During the Marine Isotope Stages (MIS) 2-3, the Patagonian ice sheet (PIS) stretched along the southern Andes from 55°S to 38°S. Based on Glacial geomorphological and geochronological evidence, its western margin reached the Pacific Ocean, while its easternmost sectors were characterised by terrestrial lobes that fed large paleo-glacial lakes. Previous studies suggest that the maximum extension of PIS was reached towards the end of the MIS 3. However, uncertainty remains regarding the glacial and climate evolution that led to its maximum extension in asynchrony with the Northern Hemisphere ice masses and Antarctica.

We present an ensemble of transient numerical simulations of the PIS that were carried out through the MIS 3 and MIS 2, aiming to determine the range of climate conditions that match the field-derived ice sheet geometries and climate history of the Patagonian ice sheet prior the global LGM, which corresponds to the timing of the local glacial maximum and its subsequent deglaciation. Furthermore, we bracketed the spread in possible ice volumes and sea level contributions originating from uncertainties in the internal parameters and external forcings. The model ensemble is built using the ice sheet model SICOPOLIS forced by phases 3 and 4 of the Paleoclimate Modeling Intercomparison Project (PMIP). The transient simulations are based on a glacial index method by using a combination of Patagonian offshore records and Antarctic cores. Our results indicate that the regional climate conditions required to reproduce a realistic growth and demise of the PIS through the Late Quaternary are not captured by coarse-resolution global climate models, implying the need of climate models with high spatial resolution and a well-constrained ice mask, which could reproduce the necessary cooling to promote the adequate growth. Our results also suggest that the MIS3 should have witnessed colder conditions than those modeled at the LGM by global climate models to realistically simulate the evolution of the PIS in agreement with geological archives.

How to cite: Castillo-Llarena, A., Retamal-Ramirez, F., Bernales, J., Jacques-Coper, M., Prange, M., and Rogozhina, I.: Unravelling the Patagonian Local Last Glacial Maximum and its Deglaciation History from a Modelling Perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17599, https://doi.org/10.5194/egusphere-egu24-17599, 2024.

X3.30
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EGU24-19781
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ECS
Shantamoy Guha, Pierre Valla, Lotta Yla-Mella, Mads Faurschou Knudsen, Franco Gianotti, Giovanni Monegato, Elena Serra, Konstanze Stübner, Johannes Lachner, Georg Rugel, and John D. Jansen

Pleistocene Glaciations and their effects on Alpine topography have drawn scientific attention since well before the days of Penck and Brückner (1909), although this indomitable pair left a strong legacy to build upon. The onset of large-scale glaciations in the Alps relative to the growth of the other great Northern Hemisphere ice sheets remains a first-order question in the Quaternary sciences. Previous chronologies from the southern Alpine Foreland based on magnetostratigraphy (Muttoni et al. 2003) and from the northern Alpine Foreland based on 10Be-26Al burial dating (Knudsen et al. 2020) converge around 1.0–0.9 Ma, during the Middle Pleistocene Transition (~1.2–0.8 Ma).

Extensive moraine complexes in the southern Alpine Foreland, such as those at Ivrea, offer a valuable opportunity to determine when glaciers advanced beyond the Alpine rangefront for the first time. The Ivrea Morainic Amphitheatre comprises interbedded glacial tills at the outlet of the Aosta Valley in NW Italy (Gianotti et al. 2015). The oldest tills have been attributed by previous workers to a stage before the Matuyama-Brunhes magnetic polarity reversal (~ 0.8 Ma).

We apply 10Be-26Al burial dating to the oldest glacigenic deposits at Ivrea, utilizing the Monte Carlo-based inversion model, P-PINI (Particle-Pathway Inversion of Nuclide Inventories). Our preliminary results indicate that the first major glacial advance occurred ~ 1.3–1.1 Ma. We combine these analyses with detrital thermochronology measurements on pebbles collected from preglacial sediments at Ivrea. These pebbles indicate provenance from the Austroalpine Massifs and an absence of the External Massifs (Mont Blanc granites)-in contrast to the present-day Aosta Valley sediments, which show the cooling signature of the Mont Blanc granites. 

We reflect on the coincident timing of the exhumation of the External Massifs and the earliest large-scale Alpine glaciations at the onset of the Middle Pleistocene Transition.

How to cite: Guha, S., Valla, P., Yla-Mella, L., Knudsen, M. F., Gianotti, F., Monegato, G., Serra, E., Stübner, K., Lachner, J., Rugel, G., and Jansen, J. D.: The first glaciers at Ivrea, southern Alpine Foreland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19781, https://doi.org/10.5194/egusphere-egu24-19781, 2024.

X3.31
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EGU24-20311
Tamás Telbisz, Márton Krasznai, Emil Gachev, Alexander Gikov, and Zsófia Ruszkiczay-Rüdiger

Cirque valleys are typical landforms of formerly glaciated high mountains, which also play an important role in paleoclimate reconstruction. In Bulgaria, the Rila (highest peak, Musala 2925 m) and Pirin (highest peak, Vihren 2915 m) mountains were the only terrains, where significant glacial cover developed during the Pleistocene glaciations, although some minor glacial landforms also exist elsewhere in Bulgaria. During the glacial periods, valleys of the Rila and Pirin Mts were re-shaped by glacial erosion and currently are characterized by glacial cirques and U-shaped valleys reaching lengths of 22 km (in Rila) and 13.5 km (in Pirin).

In these two mountain ranges, a comprehensive, quantitative geomorphometric analysis of glacial cirques valleys has not yet been carried out, thus we try to fill this gap with the present work. Primarily, digital terrain models and GIS tools were used to delineate the cirques. Based on the delineations, the main morphometric parameters of the cirques (elevation, relative depth, width, length, area, aspect, slope conditions, etc.) were calculated and a careful statistical analysis of these parameters was performed. Both the topographic orientation and the lithological structure of the two neighbouring mountains are different, that gives us an opportunity for a comparison of topo-climatic and lithological factors of cirque development. For instance, based on elevation, size and orientation of the cirques, the possible correlations with the paleoclimate factors, like exposure or moisture transport directions can be examined. Finally, our results were compared with available cirque valley morphometric data of other high mountains rising on the Balkan Peninsula.

How to cite: Telbisz, T., Krasznai, M., Gachev, E., Gikov, A., and Ruszkiczay-Rüdiger, Z.: Glacial cirque morphometry of Rila and Pirin Mountains (Bulgaria), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20311, https://doi.org/10.5194/egusphere-egu24-20311, 2024.

X3.32
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EGU24-21174
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ECS
Yanmin Yang
  • Reconstructing the extent and timing of palaeoglaciers and their associated climate is of great importance for understanding the responses of glaciers to climate change. Glacial landforms are well-preserved in Zheduo Shan, one of the high mountain ranges on the eastern Tibetan Plateau (TP). However, few studies have constrained glacial chronologies and estimated palaeoclimate in this area. We investigated the glacial advance during the Last Glacial Maximum (LGM) in Zheduo Shan using 10Be surface exposure dating. We then reconstructed the extent and thickness of LGM glaciers based on geomorphological mapping and a flowline-based glacial modelPalaeoIce. Eleven 10Be exposure ages confirmed a major LGM glacial advance between 20.0 ± 3.2 ka and 19.3 ± 2.8 ka. The reconstructed LGM glaciers in this mountain range covered an area of 499.16 km2 with an average ice thickness of 54.4 m and a total ice volume of 52.82 km3. The regional average equilibrium-line altitude (ELA) was estimated as 4524 ± 140 m, 535 ± 140 m lower than the present value. Based on the empirical relationship between precipitation and temperature (P-T model) at the ELAs on the TP, the temperature and precipitation were estimated as 3.10–5.27 ◦C and 10–16% lower during the LGM than the present values, respectively. These results suggest that the LGM glacial advance was more sensitive to temperature than precipitation in Zheduo Shan.

How to cite: Yang, Y.: Reconstruction of palaeoglaciers and palaeoclimate in Zheduo Shan, Eastern Tibetan Plateau, during the Last Glacial Maximum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21174, https://doi.org/10.5194/egusphere-egu24-21174, 2024.