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Understanding the past and future evolution of the Antarctic Ice Sheet is challenged by the availability and quality of observed paleo-boundary conditions. Numerical ice-sheet models often rely on these paleo-boundary conditions to guide and evaluate their models' predictions of sea-level rise, with varying levels of confidence due to the sparsity of existing data across the ice sheet. A key data source for large-scale reconstruction of past ice-sheet processes are internal reflecting horizons (IRHs) detected by radio-echo sounding (RES). When IRHs are isochronal and dated at ice cores, they can be used to determine paleo-accumulation rates and patterns on large spatial scales. Using a spatially extensive IRH over the Pine Island Glacier (PIG), Thwaites Glacier (THW), and the Institute and Möller ice streams (IMIS, covering a total of 610 000 km 2 or 30 % of the West Antarctic Ice Sheet (WAIS)), and a local layer approximation model, we infer mid-Holocene accumulation rates over the slow-flowing parts of these catchments for the past ∼4700 years. By comparing our results with modern climate reanalysis models (1979–2019) and observational syntheses (1651–2010), we estimate that accumulation rates over the Amundsen–Weddell–Ross Divide were on average 18 % higher during the mid-Holocene than modern rates. However, no significant spatial changes in the accumulation pattern were observed. The higher mid-Holocene accumulation-rate estimates match previous paleo-accumulation estimates from ice-core records and targeted RES surveys over the ice divide, and they also coincide with periods of grounding-line readvance during the Holocene over the Weddell and Ross sea sectors. We find that our spatially extensive, mid-Holocene-to-present accumulation estimates are consistent with a sustained late-Holocene period of higher accumulation rates occurring over millennia reconstructed from the WAIS Divide ice core (WD14), thus indicating that this ice core is spatially representative of the wider West Antarctic region. We conclude that future regional and continental ice-sheet modelling studies should base their climatic forcings on time-varying accumulation rates from the WAIS Divide ice core through the Holocene to generate more realistic predictions of the West Antarctic Ice Sheet's past contribution to sea-level rise. [ABSTRACT FROM AUTHOR]

Over the past 50 years, the British Antarctic Survey (BAS) has been one of the major acquirers of aerogeophysical data over Antarctica, providing scientists with gravity, magnetic, and radar datasets that have been central to many studies of the past, present, and future evolution of the Antarctic Ice Sheet. Until recently, many of these datasets were not openly available, restricting further usage of the data for different glaciological and geophysical applications. Starting in 2020, scientists and data managers at BAS have worked on standardizing and releasing large swaths of aerogeophysical data acquired during the period 1994–2020, including a total of 64 datasets from 24 different surveys, amounting to ∼ 450 000 line-km (or 5.3 million km 2) of data across West Antarctica, East Antarctica, and the Antarctic Peninsula. Amongst these are the extensive surveys over the fast-changing Pine Island (BBAS 2004–2005) and Thwaites (ITGC 2018–2019 & 2019–2020) glacier catchments, and the first ever surveys of the Wilkes Subglacial Basin (WISE-ISODYN 2005–2006) and Gamburtsev Subglacial Mountains (AGAP 2007–2009). Considerable effort has been made to standardize these datasets to comply with the FAIR (findable, accessible, interoperable and re-usable) data principles, as well as to create the Polar Airborne Geophysics Data Portal (https://www.bas.ac.uk/project/nagdp/ , last access: 18 July 2022), which serves as a user-friendly interface to interact with and download the newly published data. This paper reviews how these datasets were acquired and processed, presents the methods used to standardize them, and introduces the new data portal and interactive tutorials that were created to improve the accessibility of the data. Lastly, we exemplify future potential uses of the aerogeophysical datasets by extracting information on the continuity of englacial layering from the fully published airborne radar data. We believe these newly released data will be a valuable asset to future glaciological and geophysical studies over Antarctica and will significantly extend the life cycle of the data. All datasets included in this data release are now fully accessible at https://data.bas.ac.uk (British Antarctic Survey, 2022). [ABSTRACT FROM AUTHOR]

Subglacial water plays an important role in ice sheet dynamics and stability. Subglacial lakes are often located at the onset of ice streams and have been hypothesised to enhance ice flow downstream by lubricating the ice–bed interface. The most recent subglacial-lake inventory of Antarctica mapped nearly 400 lakes, of which ∼ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial-water characterisation in West Antarctica. Using radio-echo sounding data, we analyse the ice–bed interface to detect subglacial lakes. We report 33 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ∼ 40 % increase in subglacial lakes in West Antarctica. Additionally, a new digital elevation model of basal topography of the Ellsworth Subglacial Highlands was built and used to create a hydropotential model to simulate the subglacial hydrological network. This allows us to characterise basal hydrology, determine subglacial water catchments and assess their connectivity. We show that the simulated subglacial hydrological catchments of the Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not correspond to their ice surface catchments. [ABSTRACT FROM AUTHOR]

The retreating Pine Island Glacier (PIG), West Antarctica, presently contributes ~5-10% of global sea-level rise. PIG's retreat rate has increased in recent decades with associated thinning migrating upstream into tributaries feeding the main glacier trunk. To project future change requires modelling that includes robust parameterisation of basal traction, the resistance to ice flow at the bed. However, most ice-sheet models estimate basal traction from satellite-derived surface velocity, without a priori knowledge of the key processes from which it is derived, namely friction at the ice-bed interface and form drag, and the resistance to ice flow that arises as ice deforms to negotiate bed topography. Here, we present highresolution maps, acquired using ice-penetrating radar, of the bed topography across parts of PIG. Contrary to lower-resolution data currently used for ice-sheet models, these data show a contrasting topography across the ice-bed interface. We show that these diverse subglacial landscapes have an impact on ice flow, and present a challenge for modelling ice-sheet evolution and projecting global sea-level rise from ice-sheet loss. [ABSTRACT FROM AUTHOR]

Bathymetric charts are essential for modeling oceanic processes, yet, in remote areas, direct measurements of seafloor depth are often scarce. It is possible to augment sparse depth soundings with dense satellite-derived gravity data to provide additional bathymetric detail in regions devoid of sounding data. We demonstrate this method by using marine gravity derived from the European Remote Sensing (ERS-1) satellite altimeter, combined with depth soundings, to form a bathymetric prediction of the Amundsen Sea, West Antarctica. We estimate the root mean square error of depth estimates at unsurveyed locations in our solution to be ∼120 m. We use a Monte Carlo method to assess the value of gravity as a bathymetric predictor in sparsely surveyed regions by comparing our solution to predictions formed from depth soundings alone. When less than ∼11% of 10-km grid cells contain depth soundings, inclusion of gravity data improves the depth accuracy of the solution by up to 17%, as compared to a minimum curvature surface interpolation of the depth soundings alone. When depth data are sparse, our gravity-derived prediction reveals additional short-wavelength bathymetric features, such as troughs on the continental shelf, which are not resolved by interpolations of the depth soundings alone. [ABSTRACT FROM AUTHOR]

The article focuses on the determination of basal conditions for Pine Island and Thwaites Glaciers in West Antarctica. Study shows strong basal melting in upstream areas where the ice flow is fast and the basal shear stress is large. It was found out that both glaciers have mixed bed conditions with extensive areas of bedrock and weak till. The ice-stream model reveals a strong sensitivity to the assumed bed model. The results offers compatibility with limited observational constraints and theoretical work indicating an upper bound on maximum basal shear stress.

It is now almost 30 years since John Mercer () first presented the idea that climate change could eventually cause a rapid deglaciation, or “collapse,” of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 m and causing untold economic and social impacts. This idea, apparently simple and scientifically plausible, created a vision of the future, sufficiently alarming that it became a paradigm for a generation of researchers and provided an icon for the green movement. Through the 1990s, however, a lack of observational evidence for ongoing retreat in WAIS and improved understanding of the complex dynamics of ice streams meant that estimates of likelihood of collapse seemed to be diminishing. In the last few years, however, satellite studies over the relatively inaccessible Amundsen Sea sector of West Antarctica have shown clear evidence of ice sheet retreat showing all the features that might have been predicted for emergent collapse. These studies are re-invigorating the paradigm, albeit in a modified form, and debate about the future stability of WAIS. Since much of WAIS appears to be unchanging, it may, no longer be reasonable to suggest there is an imminent threat of a 5-m rise in sea level resulting from complete collapse of the West Antarctic ice sheet, but there is strong evidence that the Amundsen Sea embayment is changing rapidly. This area alone, contains the potential to raise sea level by around ~1.5 m, but more importantly it seems likely that it could, alter rapidly enough, to make a significant addition to the rate of sea-level rise over coming two centuries. Furthermore, a plausible connection between contemporary climate change and the fate of the ice sheet appears to be developing. The return of the paradigm presents a dilemma for policy-makers, and establishes a renewed set of priorities for the glaciological community. In particular, we must establish whether the hypothesized instability in WAIS is real, or simply an oversimplification resulting from inadequate understanding of the feedbacks that allow ice sheets to achieve equilibrium: and whether there is any likelihood that contemporary climate change could initiate collapse. [ABSTRACT FROM AUTHOR]

Long-term records from meteorological stations on the Antarctic Peninsula show strong rising trends in the annual duration of melting conditions. In each case, the trend is statistically significant and represents a major increase in the potential for melting; for example, between 1950 and 2000 the record from Faraday/Vernadsky Station showed a 74% increase in the number of positive degree-days (PDDs). A simple parameterization of the likely effects of the warming on the rate of snow melt suggests an increase across the Antarctic Peninsula ice sheet from 28 ± 12 Gt a-1 in 1950, to 54 ± 26 Gt a-1 by 2000. Given a similar rate of warming over the next 50 years this may reach 100 ± 46 Gt a-1. The majority of this increased meltwater does not drain into the sea but is refrozen in the ice sheet, and it is difficult to predict the fraction of ablation that will become runoff; however, a calculation based on an established criterion for runoff indicates that the contribution from the Antarctic Peninsula, as a direct and immediate response to climate warming is significant, equivalent to (0.008-0.055) mm a-1 of global sea level rise. Given future warming this could easily treble in the coming 50 years. This contribution due to increased runoff could be augmented by any dynamic imbalance in the glaciers draining the ice sheet. This finding appears to contradict the conclusions of previous assessments, including the Intergovernmental Panel on Climate Change, which considered the contribution of runoff from Antarctica to sea level rise would be insignificant. [ABSTRACT FROM AUTHOR]

Discusses the likelihood of West Antarctic Ice Sheet collapse. Definition of risk estimation in environmental issues; Review of related studies; Approaches to hazard identification; Approaches to risk estimation.

Presents ground-penetrating radar data from Antarctica, which show arches and troughs in isochronous ice layers to a depth of 100 meters. Demonstration that the origin of the features can be determined by their growth with depth; Features that result from local anomalies in accumulation rate, which can be correlated with the ice surface slope.

The article reflects on the six priorities for the southern polar research convened by the Scientific Committee on Antarctic Research (SCAR) in April 2014. Topics discussed include defining the role of interactions between the atmosphere, ocean and ice in controlling the rate of climate change, impact of changes on ocean's ability to absorb heat and carbon dioxide and mitigation of human activities for the effective Antarctic regulation. Also discusses evolution and survival of Antarctic life.

Presents information on a study which calculated a quantity known as the balance velocity in the drainage of the Antarctic Ice Sheet. Methodology of the study; Results and discussion on the study; Conclusions.

The article focuses on the characteristics and the properties of marine ice sheets, and their impact on sea-level rise. These glaciers are composed of a single and largely homogeneous material, which their viscous flow is controlled by the Navier-Stokes equation. It is specifying the stress boundary conditions on its bases and its seaward margin, which the difficulty arises. Meanwhile, the uncertainty over the future of ice sheets may continue to exist as the major unsettled in projections of sea-level rise. In relation, a report from Intergovernmental Panel on Climate Change has highlighted the urgent need to reduce uncertainty over the future of ice sheets in Greenland and Antarctica.

Ice loss from the marine-based, potentially unstable West Antarctic Ice Sheet (WAIS) contributes to current sea-level rise and may raise sea level by ≤3.3 m or even ≤5 m in the future. Over the past few decades, glaciers draining the WAIS into the Amundsen Sea Embayment (ASE) have shown accelerated ice flow, rapid thinning, and fast retreat of the grounding line (GL). However, the long-term context of this ice loss is poorly constrained, limiting our ability to accurately predict future WAIS behavior. Here we present a new chronology for WAIS retreat from the inner continental shelf of the eastern ASE, based on radiocarbon dates from three marine sediment cores. The ages document a retreat of the GL to within ∼100 km of its modern position before ca. 10,000 calibrated (cal.) yr B.P. This early deglaciation is consistent with ages for GL retreat from the western ASE. Our new data demonstrate that, in contrast to the Ross Sea, WAIS retreat from the ASE shelf was largely complete by the start of the Holocene. Our results further suggest either slow GL retreat from the inner ASE shelf throughout the Holocene, or that any episodes of fast GL retreat must have been short-lived. Thus, today's rapid retreat may be exceptional during the Holocene and may originate in recent changes in regional climate, ocean circulation, or ice-sheet dynamics. [ABSTRACT FROM AUTHOR]

Marine and rift sediments exert a fundamental control on ice stream flow in the West Antarctic Ice Sheet, and hence on its mass balance and stability. In contrast, most ice streams in the much larger East Antarctic Ice Sheet are thought to be relatively stable features resting on till, perhaps underlain by crystalline rock. Any geological controls on East Antarctic Ice Sheet enhanced flow remain largely unknown. We present aerogeophysical evidence indicating that a region of enhanced ice flow in the interior of the East Antarctic Ice Sheet is underlain by subglacial sediments ∼3 km thick and that these are influencing the flow regime of the overlying ice. We show that subglacial sediments are important in modulating ice dynamics, not just for the West Antarctic Ice Sheet, but also for its much larger neighbor, and suggest that the sedimentary basin identified here may contain information on the Neogene glacial history of this part of the East Antarctic Ice Sheet. [ABSTRACT FROM AUTHOR]