Abstract Understanding the coastal zone of the Antarctic Ice Sheet (AIS), where it interacts with the Southern Ocean and warmer air masses, is crucial for predicting Antarctica's influence on the global climate and sea level. This region has multiple tipping mechanisms that could trigger large, rapid, and potentially irreversible changes in the AIS, the Southern Ocean and their global connections in the coming centuries. The AIS remains the largest source of uncertainty in future sea‐level projections. Bed topography beneath the ice shelves and the coastal ice sheet is not yet well documented, and is a major source of this uncertainty. This review assesses current knowledge of the coastal zone and highlights methods to investigate it, including aerogeophysical surveys, ground‐ and ship‐based measurements, satellite observations, and computer modeling. An ensemble analysis of published bed topography data sets identifies significant data gaps and their regional distribution, framed in the context of current ice‐sheet behavior and potential instability. We propose scientific priorities and guidelines for future aerogeophysical surveys, advocating for a comprehensive, coordinated international effort to build a next‐generation data set of Antarctic bed properties. Such an initiative would significantly advance understanding of the role of coastal processes in ice‐sheet dynamics, reducing uncertainties in sea‐level rise projections and improving predictions of future ocean and climate changes.

Dark clayey ('old blue') tills occur at multiple locations throughout central Sweden. They have drawn scientific interest due to their over-consolidated state from ice sheet over-riding and high clay contents. These tills are overlain by younger glacial sediments and therefore predate the last deglaciation, but their absolute ages remain uncertain. T his study evaluates the residence time and chemical weathering of a dark clayey till at Forsmark, east-central Sweden, using meteoric 10Be and major oxide and trace element geochemistry, in the context of assessments of post closure safety of a planned repository for long-lived high-level spent nuclear fuel. The Forsmark landscape in the late Quaternary has periodically been a subglacial, subaquatic, or subaerial environment. Because 10Be has been supplied to sediments in each of these environments, we also measured meteoric 10Be in younger tills at Forsmark and tills from three sites above the highest postglacial shoreline, including dark clayey till at Bograngen. We then evaluated the 10Be inventory of the Forsmark dark clayey till in the context of two end-member till-deposition scenarios; early last ice sheet advance (MIS 2-3) or before MIS 3. The most likely scenario is that the residence period for the dark clayey till at Forsmark starts in early MIS 2late MIS 3. In this scenario, the advancing last ice sheet sourced fine-grained till components from sedimentary rocks and clay-rich sediments deposited in the Bothnian Sea during the MIS 3 interstadial. These sediments were then compacted as ice thickened to its Last Glacial Maximum configuration and subsequently overlain by a deglacial sandy-silty till. Dark clayey tills may not represent one specific date prior to the last deglaciation. Rather, they are a distinct sediment facies sourced from water-lain deposits, which accumulated during interstadial or interglacial conditions, and fine-grained sedimentary rocks, and were emplaced and compacted during ice sheet advances. All sediments studied at Forsmark and Bograngen display minimal chemical weathering. This conclusion is best elucidated from ACNK diagrams, where the sediment compositions approximate those of parent rocks, and is supported by a lack of indications of leaching or enrichment of elements contained in major oxides or of REE-Y along vertical sediment profiles. Minimal chemical weathering in these sediments is consistent with young ages (MIS 1 - late MIS 3) but is not in itself age diagnostic. Sediments at the remaining two sites from above the highest shoreline have the most 10Be and show slight illitization of plagioclase, which together provide evidence that these samples have a longer (pre-Holocene) history of subaerial exposure. Our interpretation that the dark clayey till at Forsmark dates from early in the last period of ice cover indicates active erosion of bedrock and sediments by the ice sheet. In the context of performing assessments of post-closure repository safety over future glacial cycles, the Forsmark dark clayey till is therefore an inappropriate analogue for soil development through multiple ice-free interglacial/interstadial periods and for the long-term evolution of groundwater buffering capacity, which is governed by bicarbonate generated through chemical weathering.

The prospect of alarming levels of future sea level rise in response to the melting of the Antarctic and Greenland ice sheets affirms an urgency to better understand the dynamics of these retreating ice sheets. The history and dynamics of the ephemeral ice sheets of the Northern Hemisphere, such as the Fennoscandian Ice Sheet, reconstructed from glacial geomorphology, can thus serve as a useful analogue. The recent release of a 1 m lidar-derived national elevation model reveals an unprecedented record of the glacial geomorphology in Sweden. This study aims to offer new insights and precision regarding ice retreat in the Torneträsk region of northwestern Sweden and the influence of ice-dammed lakes and faulting on the dynamics of the ice sheet margin during deglaciation. Using an inversion model, mapped glacial landforms are ordered in swarms representing spatially and temporally coherent ice sheet flow systems. Ice-dammed lake traces such as raised shorelines, perched deltas, spillways, and outlet channels are particularly useful for pinpointing precise locations of ice margins. A strong topographic control on retreat patterns is evident, from ice sheet disintegration into separate lobes in the mountains to orderly retreat in low-relief areas. Eight ice-dammed lake stages are outlined for the Torneträsk Basin, the lowest of which yields lake extents more extensive than previously identified. The three youngest stages released a total of 26 km3 of meltwater as glacial lake outburst floods (GLOFs) through Tornedalen, changing the valley morphology and depositing thick deltaic sequences in Ancylus Lake at its highest postglacial shoreline at around 10 ka cal BP. The Pärvie Fault, the longest-known glacially induced fault in Sweden, offsets the six oldest lake stages in the Torneträsk Basin. Cross-cutting relationships between glacial landforms and fault scarp segments are indicative of the Pärvie Fault rupturing multiple times during the last deglaciation. Precise dating of the two bracketing raised shorelines or the ages of the corresponding GLOF sediments would pinpoint the age of this rupture of the Pärvie Fault. Collectively, this study provides data for better understanding the history and dynamics of the Fennoscandian Ice Sheet during final retreat, such as interactions with ice-dammed lakes and reactivation of faults through glacially induced stress.

In this study, we evaluate the application of shallow (<2.5 m) cosmogenic depth profiles in bedrock to constrain long-term ice-burial and erosion histories. Using Markov Chain Monte Carlo inversion modelling on a series of synthetic scenarios, we demonstrate that cosmogenic Be-10 and Al-26 profiles provide more robust constraints on ice-burial duration and erosion histories than surface samples alone, particularly when erosion rates are low (<5-10 m Myr(-1)) and/or non-steady. We apply this method to new depth profiles of Be-10 and Al-26 measurements from two tors in the Parkajoki region in northeastern Sweden. Our results indicate erosion depths of similar to 2-10 m and ice burial for similar to 20-35% of the time since 500 ka. These estimates imply more erosion and less ice burial than previously inferred from the same tors. However, by re-assessing the extent of ice cover during the Weichselian from existing records, we show that some cosmogenic nuclide inheritance predates the penultimate glacial maximum (Late Saalian), implying limited glacial erosion in the Parkajoki region during the last glacial cycle.

Reconstructions of palaeoseismicity are useful for understanding and mitigating seismic hazard risks. We apply cosmogenic 36Cl exposure-age dating and measurements of rare-earth elements and yttrium (REE-Y) concentrations to the palaeoseismic history of the Sparta Fault, Greece. Bayesian-inference Markov chain Monte Carlo (MCMC) modelling of 36Cl concentrations along a 7.2 m long vertical profile on the Sparta Fault scarp at Anogia indicate an increase in the average slip rate of the scarp from 0.8-0.9 mm yr-1 6.5-7.7 kyr ago to 1.1-1.2 mm yr-1 up to the devastating 464 BCE earthquake. The average exhumation of the entire scarp up to the present day is 0.7-0.8 mm yr-1. Modelling does not indicate additional exhumation of the Sparta Fault after 464 BCE. The Sparta Fault scarp is composed of fault breccia, containing quartz and clay-lined pores, in addition to host-rock-derived clasts of calcite and microcrystalline calcite cement. The impurities control the distribution of REE-Y in the fault scarp surface and contribute spatial variation to 36Cl concentrations, which precludes the identification of individual earthquakes that have exhumed the Sparta Fault scarp from either of these data sets. REE-Y may illustrate processes that localize slip to a discrete fault plane in the Earth's near-surface, but their potential use in palaeoseismicity would benefit from further evaluation.

Virtual reality is a technological development that, among others, has revolutionized Earth sciences. Its advantages include an opportunity to examine places otherwise difficult or impossible to access and it may also become an important component of education, fostering a better understanding of processes and landforms, geohazard awareness, and an appreciation of geoheritage. This paper reports on the GeoVT project, which aims to create a platform to build and disseminate Virtual Field Trips (VFTs) focused on geomorphology, natural hazards associated with geomorphological processes, and geoheritage sites. To put the GeoVT project in context, an overview of applications of VR in geosciences is provided. This paper subsequently proceeds with a presentation of the project and the GeoVT Authoring application, which is an innovative platform designed to help teachers and students, followed by brief presentations of a number of VFTs developed within the project. They address themes such as fluvial landforms and valley development, coastal landforms, evidence of past glaciation, coastal erosion, wildfire effects, mud volcanoes, and landslides.

In situ cosmogenic 14C (in situ 14C) in quartz provides a recently developed tool to date exposure of bedrock surfaces of up to ∼ 25 000 years. From outcrops located in east-central Sweden, we tested the accuracy of in situ 14C dating against (i) a relative sea level (RSL) curve constructed from radiocarbon dating of organic material in isolation basins and (ii) the timing of local deglaciation constructed from a clay varve chronology complemented with traditional radiocarbon dating. Five samples of granitoid bedrock were taken along an elevation transect extending southwestwards from the coast of the Baltic Sea near Forsmark. Because these samples derive from bedrock outcrops positioned below the highest postglacial shoreline, they target the timing of progressive landscape emergence above sea level. In contrast, in situ 14C concentrations in an additional five samples taken from granitoid outcrops above the highest postglacial shoreline, located 100 km west of Forsmark, should reflect local deglaciation ages. The 10 in situ 14C measurements provide robust age constraints that, within uncertainties, compare favourably with the RSL curve and the local deglaciation chronology. These data demonstrate the utility of in situ 14C to accurately date ice sheet deglaciation, and durations of postglacial exposure, in regions where cosmogenic 10Be and 26Al routinely return complex exposure results.

The impact of late Cenozoic climate on the East Antarctic Ice Sheet is uncertain. Poorly constrained patterns of relative ice thinning and thickening impair the reconstruction of past ice-sheet dynamics and global sea-level budgets. Here we quantify long-term ice cover of mountains protruding the ice-sheet surface in western Dronning Maud Land, using cosmogenic Chlorine-36, Aluminium-26, Beryllium-10, and Neon-21 from bedrock in an inverse modeling approach. We find that near-coastal sites experienced ice burial up to 75–97% of time since 1 Ma, while interior sites only experienced brief periods of ice burial, generally <20% of time since 1 Ma. Based on these results, we suggest that the escarpment in Dronning Maud Land acts as a hinge-zone, where ice-dynamic changes driven by grounding-line migration are attenuated inland from the coastal portions of the East Antarctic Ice Sheet, and where precipitation-controlled ice-thickness variations on the polar plateau taper off towards the coast.

The aim of this study is to test the Holocene relative sea-level (RSL) curve (or shoreline displacement curve) for east central Sweden using 14C produced in situ in quartz-bearing bedrock (in-situ 14C). The original RSL curve is instead based on radiocarbon dating of organic material from isolation basins. Having an accurate RSL curve is crucial from at least two aspects. In Sweden’s safety assessments for a planned spent nuclear fuel repository and for the existing repository for low- and intermediate level waste, the RSL curve is used to constrain the emergence above sea level in landscape development models. Also, the RSL is used to constrain model estimates of rates and depths of glacial and subaerial erosion from cosmogenic 10Be and 26Al produced in situ in quartz in bedrock surfaces.Avoiding vein quartz and hydrothermally altered bedrock, five samples of granitoid bedrock were taken along an elevation transect extending southwards from Forsmark, the location of the planned spent nuclear fuel repository. Because all samples derive from bedrock outcrops positioned below the highest postglacial shoreline, they target the timing of progressive landscape emergence above sea level. To further assess the accuracy of in-situ 14C dating, we took an additional five samples from bedrock outcrops 100 km west of Forsmark, above the highest postglacial shoreline. The in-situ 14C concentrations in these samples should reflect local deglaciation ages.The ten new in-situ 14C measurements provide robust age constraints that compare favorably with the original RSL curve derived from radiocarbon dating of organic material in isolation basins and with the regional deglaciation chronology. Inferences of limited rates and depths of bedrock erosion over the past 1 Myr, inferred from 10Be and 26Al inheritance and which are critically dependent on the RSL curve, therefore glean strong support from these new in-situ 14C measurements.

Ice streams regulate most ice mass loss in Antarctica. Determining ice stream response to warmer conditions during the Pliocene could provide insights into their future behaviour, but this is hindered by a poor representation of subglacial topography in ice-sheet models. We address this limitation using a high-resolution model for Dronning Maud Land (East Antarctica). We show that contrary to dynamic thinning of the region’s ice streams following ice-shelf collapse, the largest ice stream, Jutulstraumen, thickens by 700 m despite lying on a retrograde bed slope. We attribute this counterintuitive thickening to a shallower Pliocene subglacial topography and inherent high lateral stresses at its flux gate. These conditions constrict ice drainage and, combined with increased snowfall, allow ice accumulation upstream. Similar stress balances and increased precipitation projections occur across 27% of present-day East Antarctica, and understanding how lateral stresses regulate ice-stream discharge is necessary for accurately assessing Antarctica’s future sea-level rise contribution.

A series of near-planar subhorizontal bedrock surfaces is developed in Precambrian gneissic granite basement in SW Sweden.These surfaces are located within 0.1 -10 km of the 150 m-high Halleberg and Hunneberg table mountains, which are comprised of marine sedimentary units capped by a dolerite sill.The near-planar bedrock surfaces have traditionally been interpreted as exhumed remnants of a regional Subcambrian unconformity.We evaluate an alternative hypothesis that these spectacular surfaces are attributable to formation and erosional exploitation of subhorizontal sheeting joints by the late Quaternary Fennoscandian Ice Sheet.We use a combination of landscape analyses in a GIS, field measurements of bedrock jointing, laboratory analyses of basement chemical weathering, ground penetrating radar imaging of subsurface jointing, erosion rates from cosmogenic nuclides, and numerical ice sheet modelling.This diverse dataset supports the following interpretations: (1) marine erosion of weathered rock during the Cambrian transgression was likely important to the formation of the regional SCU; (2) the spectacular flatness of the surfaces studied is attributable to Quaternary glacial erosion, with sheeting joints providing a first-order structural control; (3) subhorizontal hydrofracturing of bedrock in the near-surface (perhaps up to hundreds of meters depth) occurred in either a marine proglacial or a subglacial/ice marginal setting.This hydrofracturing was promoted by episodic drainage of supra-glacial meltwater ponds along crevasses and fractures in the ice that are directly connected to the ice sheet bed, and by ice sheet deformation around the steep sides of the table mountains.Basal meltwater could temporarily decouple the ice sheet margin from its bed and generate subglacial (and/or proglacial) water pressures in the bedrock that are sufficient to generate subhorizontal fractures hundreds of meters long.Glacial ice subsequently exploited these subhorizontal planes of weaknesses to erode blocks (with volumes potentially exceeding 125 m 3 , based on observations elsewhere in southern Sweden), leaving remnant near-planar bedrock surfaces.

Abstract Ice streams regulate most ice mass loss in Antarctica. Determining their response to Pliocene warmth could provide insights into their future behaviour, but is hindered by poor representation of subglacial topography in ice-sheet models. We address this limitation using a high-resolution regional model for Dronning Maud Land (East Antarctica). We show that the region’s largest ice stream, Jutulstraumen, thickens by 700 m under warm late-Pliocene conditions despite ice-shelf collapse and a retrograde bed slope, while nearby ice streams thin. While it is known that unstable retreat on a retrograde slope can be slowed under certain conditions, this finding illustrates that an ice stream can thicken and gain mass. We attribute thickening to high lateral stresses at its flux gate, which constrict ice drainage. Similar stress balances occur today in 27% of East Antarctica, and understanding how lateral stresses regulate ice-stream discharge is necessary for accurately assessing Antarctica’s sea-level rise contribution.

Ice can sculpt extraordinary landscapes, yet the efficacy of, and controls governing, glacial erosion on geological timescales remain poorly understood and contended, particularly across Polar continental shields. Here, we assimilate geophysical data with modelling of the Eurasian Ice Sheet — the third largest Quaternary ice mass that spanned 49°N to 82°N — to decipher its erosional footprint during the entire last ~100 ka glacial cycle. Our results demonstrate extreme spatial and temporal heterogeneity in subglacial erosion, with rates ranging from 0 to 5 mm a −1 and a net volume equating to ~130,000 km 3 of bedrock excavated to depths of ~190 m. A hierarchy of environmental controls ostensibly underpins this complex signature: lithology, topography and climate, though it is basal thermodynamics that ultimately regulates erosion, which can be variously protective, pervasive, or, highly selective. Our analysis highlights the remarkable yet fickle nature of glacial erosion — critically modulated by transient ice-sheet dynamics — with its capacity to impart a profound but piecemeal geological legacy across mid- and high latitudes.

The East Antarctic Ice Sheet stores a vast amount of freshwater, which makes it the single largest potential contributor to future sea-level rise. However, the lack of well-constrained geological records of past ice sheet changes impedes model validation, hampers mass balance estimates, and inhibits examination of ice loss mechanisms. Here we identify rapid ice-sheet thinning in coastal Dronning Maud Land from Early to Middle Holocene (9000–5000 years ago) using a deglacial chronology based on in situ cosmogenic nuclide surface exposure dates from central Dronning Maud Land, in concert with numerical simulations of regional and continental ice-sheet evolution. Regional sea-level changes reproduced from our refined ice-load history show a highstand at 9000–8000 years ago. We propose that sea-level rise and a concomitant influx of warmer Circumpolar Deep Water triggered ice shelf breakup via the marine ice sheet instability mechanism, which led to rapid thinning of upstream coastal ice sheet sectors.

The advance of the Cordilleran Ice Sheet (CIS) towards its Last Glacial Maximum (LGM) configuration and its subsequent retreat remain poorly understood. We use the glacial landform record to determine ice dynamics for the central sector of the CIS in northern British Columbia, Canada, beneath the LGM ice divide. We classify seventy ice-flow indicator flowsets based on morphology, elevation, orientation and cross-cutting relationships into one of three stages, whereby stage 1 is oldest and stage 3 youngest. Combined with ice-contact geomorphology, our reconstruction highlights complex changes in ice flow over time as a result of ice divide migrations through the LGM and deglacial phases. The orientation and distribution of landforms indicates active post-LGM ice retreat westward through the Cassiar and Omineca mountains. We map the regional distribution of independent mountain glaciers, ice caps, and ice fields that regrew during a cooling event in the Late Glacial and show that some of these readvance glaciers were subsequently overrun by advancing outlet glaciers of the CIS. We use the cross-cutting relationship between readvance glaciers and CIS outlet glaciers and available chronological data to reconstruct the eastern CIS margin during the Late Glacial for the first time.

The Quaternary is characterized by long periods of glacier and ice sheet growth (glaciations) interspersed with short periods of glacier retreat and ice sheet decay (interglaciations). Glaciers form preferentially in high‐altitude and high‐latitude locations owing to low mean annual temperatures. Most of the world's high mountain ranges have therefore hosted glaciers during the Quaternary and have characteristic and often spectacular glacial erosional landforms. Glaciers continue to be critical infrastructural elements as a reliable source of fresh water for many downstream communities.

The Marine Isotope Substage 11c (MIS11c) interglacial (425 – 395 thousand years before present) is a useful analogue to climate conditions that can be expected in the near future, and can provide insights on the natural response of the Antarctic ice sheets to a moderate, yet long lasting warming period. However, its response to the warming of MIS11c and consequent contribution to global sea level rise still remains unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice-sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three ice core and one sedimentary proxy records of ice volume. We identify a tipping point beyond which oceanic warming becomes the dominant forcing of ice-sheet retreat, and where collapse of the West Antarctic Ice Sheet is attained when a threshold of 0.4 oC oceanic warming relative to Pre-Industrial levels is sustained for at least 4 thousand years. Conversely, its eastern counterpart remains relatively stable, as it is mostly grounded above sea level. Our results suggest a total sea level contribution from the East and West Antarctic ice sheets of 4.0 – 8.2 m during MIS11c. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea-level reconstructions, this range is reduced to 6.7 – 8.2 m, and mostly reflects uncertainties regarding the initial configuration of the East Antarctic Ice Sheet.

Studying the response of the Antarctic ice sheets during periods when climate conditions were similar to the present can provide important insights into current observed changes and help identify natural drivers of ice sheet retreat. In this context, the marine isotope substage 11c (MIS11c) interglacial offers a suitable scenario, given that during its later portion orbital parameters were close to our current interglacial. Ice core data indicate that warmer-than-present temperatures lasted for longer than during other interglacials. However, the response of the Antarctic ice sheets and their contribution to sea level rise remain unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three glaciological and one sedimentary proxy records of ice volume. Our results indicate that the East and West Antarctic ice sheets contributed 4.0–8.2 m to the MIS11c sea level rise. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea level reconstructions, the range is reduced to 6.7–8.2 m independently of the choices of external sea level forcing and millennial-scale climate variability. Within this latter range, the main source of uncertainty arises from the sensitivity of the East Antarctic Ice Sheet to a choice of initial ice sheet configuration. We found that the warmer regional climate signal captured by Antarctic ice cores during peak MIS11c is crucial to reproduce the contribution expected from Antarctica during the recorded global sea level highstand. This climate signal translates to a modest threshold of 0.4 ∘C oceanic warming at intermediate depths, which leads to a collapse of the West Antarctic Ice Sheet if sustained for at least 4000 years.

Numerical models predict that discharge from the polar ice sheets will become the largest contributor to sea-level rise over the coming centuries. However, the predicted amount of ice discharge and associated thinning depends on how well ice sheet models reproduce glaciological processes, such as ice flow in regions of large topographic relief, where ice flows around bedrock summits (i.e. nunataks) and through outlet glaciers. The ability of ice sheet models to capture long-term ice loss is best tested by comparing model simulations against geological data. A benchmark for such models is ice surface elevation change, which has been constrained empirically at nunataks and along margins of outlet glaciers using cosmogenic exposure dating. However, the usefulness of this approach in quantifying ice sheet thinning relies on how well such records represent changes in regional ice surface elevation. Here we examine how ice surface elevations respond to the presence of strong topographic relief that acts as an obstacle by modelling ice flow around and between idealised nunataks during periods of imposed ice sheet thinning. We find that, for realistic Antarctic conditions, a single nunatak can exert an impact on ice thickness over 20 km away from its summit, with its most prominent effect being a local increase (decrease) of the ice surface elevation of hundreds of metres upstream (downstream) of the obstacle. A direct consequence of this differential surface response for cosmogenic exposure dating is a delay in the time of bedrock exposure upstream relative to downstream of a nunatak summit. A nunatak elongated transversely to ice flow is able to increase ice retention and therefore impose steeper ice surface gradients, while efficient ice drainage through outlet glaciers produces gentler gradients. Such differences, however, are not typically captured by continent-wide ice sheet models due to their coarse grid resolutions. Their inability to capture site-specific surface elevation changes appears to be a key reason for the observed mismatches between the timing of ice-free conditions from cosmogenic exposure dating and model simulations. We conclude that a model grid refinement over complex topography and information about sample position relative to ice flow near the nunatak are necessary to improve data–model comparisons of ice surface elevation and therefore the ability of models to simulate ice discharge in regions of large topographic relief.