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Glacier and ice sheet retreat exposes freshly deglaciated terrain which often contains small-scale fragile geomorphological features which could provide insight into subglacial or submarginal processes. Subaerial exposure results in potentially rapid landscape modification or even disappearance of the minor-relief landforms as wind, weather, water and vegetation impact on the newly exposed surface. Ongoing retreat of many ice masses means there is a growing opportunity to obtain high resolution geospatial data from glacier forelands to aid in the understanding of recent subglacial and submarginal processes. Here we used an unmanned aerial vehicle to capture close-range aerial photography of the foreland of Isfallsglaciären, a small polythermal glacier situated in Swedish Lapland. An orthophoto and a digital elevation model with ~2 cm horizontal resolution were created from this photography using structure from motion software. These geospatial data was used to create a geomorphological map of the foreland, documenting moraines, fans, channels and flutes. The unprecedented resolution of the data enabled us to derive morphological metrics (length, width and relief) of the smallest flutes, which is not possible with other data products normally used for glacial landform metrics mapping. The map and flute metrics compare well with previous studies, highlighting the potential of this technique for rapidly documenting glacier foreland geomorphology at an unprecedented scale and resolution. The vast majority of flutes were found to have an associated stoss-side boulder, with the remainder having a likely explanation for boulder absence (burial or erosion). Furthermore, the size of this boulder was found to strongly correlate with the width and relief of the lee-side flute. This is consistent with the lee-side cavity infill model of flute formation. Whether this model is applicable to all flutes, or multiple mechanisms are required, awaits further study. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Longitudinal surface structures (LSSs) are flow parallel curvilineations visible on satellite imagery which are commonly observed on ice shelves, ice streams and glaciers. Their distribution and genesis has the ability to inform us about ice sheet history and glacial processes. Multiple hypotheses have been proposed for their formation. Here, we present continental-scale mapping of these features across the entire Antarctic ice sheet. The accompanying map details 42,311 polylines representing LSSs identified on satellite imagery (Landsat, RADARSAT and MODIS). The subtlety of these features provides many challenges for their identification and mapping. This work will provide the basis for future research on the morphology and formative conditions of these features in order to shed light on their genesis. [ABSTRACT FROM PUBLISHER]

Improved understanding of the dynamics, extent and palaeogeography of retreating ice sheets can be accomplished by combining ice sheet modelling with the wealth of evidence they leave behind. Large volumes of constraining data exist and numerical models which can simulate entire glaciations are readily available. However, attempts to directly compare and connect empirically-based reconstructions with model-based simulations have been surprisingly rare, perhaps due to the complexity of combining the two fields and the abundance of approaches that could be taken. Here, we focus on a new method of directing ice sheet model simulations to match empirically reconstructed ice extents through time. Empirical evidence recording the behaviour of the last British-Irish Ice Sheet has been enhanced by the BRITICE-CHRONO consortium of researchers. This has been a six-year project to constrain the timing of retreat by a systematic dating programme focused on the marine-to-terrestrial transition. From two research cruises (18,000 km of geophysical data and 377 vibro- and piston cores), along with numerous investigations of stratigraphic sections on land we collected samples for dating from 914 sites from which 639 new geochronometric ages have been derived (336 radiocarbon, 156 luminescence and 157 cosmogenic). Organised into eight key transects from the shelf break to tens of kilometers onshore the pattern and pace of retreat has been compiled into an ice sheet wide reconstruction of ice extent at one thousand year times steps. We then used numerical models either forced or nudged to comply with these ice extents to yield simulations of ice sheet change thereby incorporating ice sheet physics, grounding lines, ice shelves, ice streams, and glacio isostatic adjustment and sea level. This empirically-constrained model simulation of the last British-Irish Ice Sheet will be presented. [ABSTRACT FROM AUTHOR]

Mapping of glacial landforms has long been a cornerstone of glacial geomorphology, but it was not until the advent of remote sensing and GIS that widespread detailed mapping could be achieved. Using the examples of subglacial bedforms and the BRITICE project, I highlight how large databases of glacial geomorphological mapping can be used to: i) understand landform genesis; ii) reconstruct palaeo-ice sheets; and iii) validate ice sheet models. Arguably, glacial geomorphology has never been more useful. However, there is still room for improvement. Automated mapping techniques remain in their infancy. Yet, detailed remote sensing data at continental scales is becoming available, the scale of which is a daunting challenge for lone-manual mapping. Could machine learning hold an answer? Furthermore, completed work is often disparately stored and non-standardised. This leads to duplication of research and limits the utility of the collected datasets for future researchers. Here, I call upon the glacial geomorphological community to launch an open-access database of glacial geomorphological mapping on a global scale. [ABSTRACT FROM AUTHOR]

Surface meltwater is widespread across the Antarctic Ice Sheet. While much recent research has focused on understanding the impact meltwater has on ice shelves, where its presence can act as a catalyst for rapid ice shelf break up, the effect of meltwater on grounded ice dynamics in Antarctica remains unknown. Using high-resolution ice velocity data derived from Sentinel 1 imagery we identify previously unobserved large (up to 100% greater than the annual mean), sudden, and synchronous accelerations in ice flow at 5 glaciers across the Antarctic Peninsula, which occur during modelled periods of surface melt. Coincident optical satellite imagery demonstrates that although much of the surface meltwater refreezes, some water appears to access the bed through crevasses and surface lake drainage. Several characteristics of the ice accelerations are consistent with the enhancement of basal motion by surface-derived meltwater reaching the ice bed. Firstly, speed-up events are often followed by short-lived reductions in ice velocity to pre-event values, and secondly, their relative magnitude is greater in regions of observed surface melt, immediately downstream of surface lake drainage events and after prolonged periods of no-or-little melt. Our data suggest that following arrival at the ice bed, meltwater is efficiently evacuated, limiting the duration of speed-up events to less than 6 days (the temporal resolution of our data). Although Antarctic Peninsula speed-up events are currently short-lived, we anticipate that predicted longer and more intense melt-seasons may lead to a shift in ice-dynamics in the region. [ABSTRACT FROM AUTHOR]

This contribution documents the process of assessing the quality of data within a compilation of legacy geochronological data relating to the last British-Irish Ice Sheet, a task undertaken as part of a larger community-based project (BRITICE-CHRONO) that aims to improve understanding of the ice sheet's deglacial evolution. As accurate reconstructions depend on the quality of the available data, some form of assessment is needed of the reliability and suitability of each given age(s) in our dataset. We outline the background considerations that informed the quality assurance procedures devised given our specific research question. We describe criteria that have been used to make an objective assessment of the likelihood that an age is influenced by the technique specific sources of geological uncertainty. When these criteria were applied to an existing database of all geochronological data relating to the last British-Irish Ice Sheet they resulted in a significant reduction in data considered suitable for synthesis. The assessed data set was used to test a Bayesian approach to age modelling ice stream retreat and we outline our procedure that allows us to minimise the influence of potentially erroneous data and maximise the accuracy of the resultant age models. [ABSTRACT FROM AUTHOR]

Globally, glaciers and icefields contribute significantly to sea level rise. Here we show that ice loss from Juneau Icefield, a plateau icefield in Alaska, accelerated after 2005 AD. Rates of area shrinkage were 5 times faster from 2015-2019 than from 1979-1990. Glacier volume loss remained fairly consistent (0.65-1.01 km 3 a -1 ) from 1770-1979 AD, rising to 3.08-3.72 km 3 a -1 from 1979-2010, and then doubling after 2010 AD, reaching 5.91 ± 0.80 km 3 a -1 (2010-2020). Thinning has become pervasive across the icefield plateau since 2005, accompanied by glacier recession and fragmentation. Rising equilibrium line altitudes and increasing ablation across the plateau has driven a series of hypsometrically controlled melt-accelerating feedbacks and resulted in the observed acceleration in mass loss. As glacier thinning on the plateau continues, a mass balance-elevation feedback is likely to inhibit future glacier regrowth, potentially pushing glaciers beyond a dynamic tipping point., (© 2024. The Author(s).)

The Antarctic continent reached its current polar location ~83 Ma and became shrouded by ice sheets ~34 Ma, coincident with dramatic global cooling at the Eocene-Oligocene boundary. However, it is not known whether the first Antarctic glaciers formed immediately prior to this or were present significantly earlier. Here we show that mountain glaciers were likely present in the Transantarctic Mountains during the Late Palaeocene (~60-56 Ma) and middle Eocene (~48-40 Ma). Temperate (warm-based) glaciers were prevalent during the Late Eocene (~40-34 Ma) and, in reduced numbers, during the Oligocene (~34-23 Ma), before larger, likely cold-based, ice masses (including ice sheets) dominated. Some temperate mountain glaciers were present during the Miocene Climatic Optimum (~15 Ma), before a widespread switch to cold-based glaciation. Our findings highlight the longevity of glaciation in Antarctica and suggest that glaciers were present even during the Early-Cenozoic greenhouse world., (© 2022. The Author(s).)