Matthew R. Siegfried

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.

Pingos are large mounds with cores formed of intrusive ice that form in periglacial landscapes. These ice structures can form in regions of discontinuous permafrost, commonly as hydraulic or open‐system pingos, or in locations of continuous permafrost, commonly as hydrostatic or closed‐system pingos. Using C‐band Interferometric Synthetic Aperture Radar (InSAR) data from the Sentinel‐1 constellation acquired between 2017 and 2025 over the Alaskan North Slope, we quantified interannual surface deformation trends over several hydrostatic pingos. Eight of the 11 pingos analyzed experienced cumulative uplift ranging from 1.49 to 11.35 cm over an 8‐year period, two experienced cumulative subsidence ranging from 0.57 to 2.46 cm, and two experienced no statistically significant surface‐height change. All of the cumulatively uplifting pingos exhibited surface‐height time series proportional to a square‐root dependence with time, which is physically consistent with an aggradational process via Stefan's equation. Ground penetrating radar profiles acquired over select pingos revealed subsurface reflector structures consistent with massive ice cores, reinforcing the hypothesis that the observed surface uplift is driven by intrusive ice formation mediated by elevated hydrostatic pressure due to permafrost aggradation. These results demonstrate that InSAR methods can resolve subtle geodetic signals associated with pingo topographic change, such as from pingo growth due to permafrost aggradation. InSAR observations can thus yield process‐scale insights into the dynamic evolution of pingos and associated periglacial landforms.

The NASA/CNES Surface Water and Ocean Topography (SWOT) swath‐mapping radar altimetry satellite mission, launched in December 2022, provides repeat‐track coverage to about ±78.2° latitude every 21 days, sampling many of Antarctica's most dynamic ice shelves that play key roles in constraining mass loss from the grounded ice sheet. Understanding how ice‐shelf extent and thickness respond to forcings requires three‐dimensional mapping of ice structure at the short time and space scales of major mass change processes including basal and surface mass balances, and crevasse growth. We demonstrate that repeated SWOT high‐rate acquisitions can accurately monitor changes in ice‐shelf surface heights, revealing key processes including responses to ocean tides and atmospheric forcing, ice flexure along grounding zones, and crevasse deepening, that affect stresses impacting ice loss. Despite limitations in acquisition and processing, some of which are being addressed, the SWOT mission provides exciting new opportunities for studying ice‐shelf dynamics.

The Foundation-Patuxent-Academy system (FPAS) is a major Antarctic ice stream system, draining both East and West Antarctica, with a global sea level potential of ∼3 m. We provide a holistic catchment-scale overview of the FPAS reviewing its glaciological and hydrological systems, its glacial history, and its modelled response to past and future climate change. FPAS may be vulnerable to future change because of: (i) a deep (∼2.4 km below sea level) low-gradient retrograde bed that encourages grounding-zone retreat; (ii) a low-gradient ice surface and high tidal range, which are likely to promote flotation of grounded ice and seawater intrusion; (iii) an active and dynamic subglacial hydrological system; (iv) complex ice-meltwater-ocean interactions at the grounding zone; (v) potential for substantive expansion of the across-flow length – and cross sectional area – of the grounding zone; and (vi) susceptibility to ice flow-switching and water piracy (e.g. via the adjacent Support Force Glacier). Despite such potential vulnerabilities, existing numerical model simulations of FPAS grounding-zone retreat produce a wide and divergent range of past and future scenarios. Uncertainties in the future response of the FPAS to a warming climate result from poor constraints on its topography and hydrology, processes of ice-ocean interaction, interlinkages with the surrounding ice sheet and ice shelf, and a shortage of FPAS-specific modelling experiments. This review outlines and evaluates these critical gaps in our knowledge of the FPAS and develops a strategy to address them. This strategy would provide: (i) the first robust and comprehensive evaluation of the FPAS's vulnerability to current and near-future climate forcing; and (ii) improved constraints on projections of the future contribution of the Antarctic Ice Sheet to sea-level rise.

Proprietary development solutions are often perceived as being delivered more quickly and easily than open methods, fueling the misconception that they inherently produce better overall outcomes. However, we argue that open development practices can lead to both efficient and maximally impactful outcomes. One successful strategy for accelerating open approaches in the geosciences is co‐creation, a model that emphasizes shared ownership between developers and users. This approach creates a collaborative flywheel dynamic—pioneered in the geosciences by the Pangeo project—that encourages teamwork, standardizes access to shared infrastructure, and facilitates iterations of stakeholder feedback and development to accelerate solution finding.

NASA’s ICESat-2 mission was launched in 2018, carrying a photon-counting laser altimeter, with a primary objective of measuring height changes across Earth’s surface. ICESat-2 has provided measurements of ice surface height between 88º N and S, repeated four times per year, with high vertical accuracy and along-track spatial resolution. Its accuracy and coverage has enabled near-complete recovery of height changes across the ice sheets, capturing subtle changes in the interior, and rapid changes along the dynamic margins with steep slopes and the floating peripheral ice shelves. The ICESat-2 Science Team has developed a suite of algorithms that produce along-track and gridded land ice height products at various levels of processing, all freely available at the National Snow and Ice Data Center. Here, we describe three higher-level land-ice data products derived from ATL06 and their underlying algorithms: along-track height change (ATL11), digital elevation model (ATL14) and gridded surface height change (ATL15). We demonstrate the suitability of each data product for studying different ice sheet regions. We then show height changes for Greenland and Antarctica from ATL15 during the first 6 years of the ICESat-2 mission (October 2018–December 2024), illustrating how ICESat-2 measurements can distinguish the multi-year trends from seasonal fluctuations.

Monitoring glacier dynamics is essential for understanding climate change impacts, safeguarding water resources, and protecting communities from related hazard. Distributed acoustic sensing (DAS) provides a unique opportunity to observe these dynamic environments with high spatial and temporal resolution. However, creating comprehensive seismic event catalogs from DAS data requires the development of efficient, automated tools. In this study, we analyzed 17.6 TB of DAS data collected over 31 d from a 9 km fiber-optic cable deployed on Rhonegletscher, Switzerland. The cable recorded strain-rate data along 2225 channels, spanning both snow-covered and bare-ice regions. We developed a robust preprocessing pipeline to address challenges posed by noise, coupling inconsistencies, and large data volumes. Our feature extraction is based on covariance matrix analysis, which allowed us to characterize wavefield properties using the first eigenvalue, coherency function, and eigenvalue variance. We compared unsupervised and supervised approaches, evaluating their relative effectiveness in detecting cryoseismic events across noisy DAS datasets. Although unsupervised methods provided valuable insights into inherent data patterns, their performance was hindered by dataset imbalance and noise. In contrast, supervised methods trained on manually labeled data demonstrated higher classification accuracy and reliability, with random forest emerging as the top performer, achieving 81% cross-validation accuracy, 93% test accuracy using a random split, and 73% test accuracy when evaluated with a grouped split to avoid data leakage. By combining cloud and parallel computing, we develop a scalable framework that streamlines DAS data analysis and supports future operational monitoring and research on glacier dynamics. The resulting comprehensive catalog, comprising thousands of detected and classified cryoseismic events, provides a valuable resource for scientists, fostering advancements in cryosphere monitoring and hazard assessment within the context of a changing climate.

This study revisited 158 documented active subglacial lakes across Antarctica, applying a height‐change anomaly delineation algorithm to CryoSat‐2 and ICESat‐2 satellite altimetry data to assemble a 14.75‐year (2010.5–2025.25) time series of active subglacial lake dynamics. We generated time‐evolving lake outlines at quarter‐year intervals that revealed spatiotemporal variability, including lake expansions and migrations. Evolving outlines enabled improved estimates of subglacial water volume change. We found that the previous method of using stationary outlines underestimated cumulative volume change between 4.8–7.4 (65–100 of the volume change estimated using evolving outlines) compared to evolving outlines when integrated across Antarctica. Evolving lake outlines also enabled the generation of a novel time series of subglacial lakebed active area, which we leveraged to estimate time‐varying dissolved inorganic carbon production.

Whillans Ice Plain (WIP), a region of West Antarctica flowing into the southern Ross Sea, lurches forward 0.2–0.6 m over 30–60 min once or twice per diurnal ocean tidal cycle. Combining 11 years (2008–2019) of 30 s or better resolution Global Navigation Satellite System (GNSS) data from past field campaigns is necessary to provide insight into WIP dynamics by connecting individual slip events to decadal velocity trends. We processed GNSS data from 48 stations and used a linear least squares residual thresholding algorithm to automatically detect 5150 slip events during the 11‐year observational period. Event frequency decreased over the 11‐year record, due to an increased prevalence of one‐slip diurnal ocean tidal cycles over two‐slip cycles. Slip‐event frequency varies at fortnightly, monthly, and semiannual ocean tidal periods, but does not explain the overall decrease in events. Combining the full complexity of the regional barotropic tides with secular changes over decadal timescales is necessary to interpret observed ice‐stream dynamics.