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.

Complex interactions among the ocean, sea ice, and ice shelves in the Southern Ocean are critical for global climate, yet accurately simulating these processes remains challenging in climate models, such as those participating in the Coupled Model Intercomparison Project Phase 6, due to their coarse resolution and incomplete physical components. Therefore, the development of high-resolution circumpolar coupled ocean-sea ice-ice shelf models could improve our understanding of the evolution of the Southern Ocean. In this study, we use the c66m version of the Massachusetts Institute of Technology General Circulation Model, including a sea ice component and an ice shelf component, to configure the coupled Southern Ocean-Sea ice-Ice shelf Model (SOSIM v1.0). Adopting the Refined Topography dataset version 2 for the geometry of seafloor and ice draft, SOSIM features a horizontal resolution of similar to 5 km and 70 vertical layers. Forced by the European Centre for Medium-Range Weather Forecasts Reanalysis v5, a long-term integration of SOSIM is run forward from 1979 to 2022, with daily outputs for estimating the oceanic state, sea ice evolution, and basal mass balance of ice shelves. A comprehensive evaluation of the performance of SOSIM has been conducted against multiple observational and reanalysis datasets. Identified biases include an underestimated Antarctic Circumpolar Current transport, an overestimated Antarctic Slope Current, a warm drift in abyssal waters, an exaggerated seasonality of sea ice extent, and an underestimated total ice shelf mass loss. Despite these limitations, SOSIM still captures large-scale hydrographic structures, the annual variability of sea ice, and cross-slope exchanges over shelf seas. Furthermore, SOSIM is set to serve as the dynamical core for the next-generation Southern Ocean Ice Prediction System being developed in China.

Monitoring Antarctic surface melt using satellite-based Earth observation relies heavily on passive microwave data for their all-weather capability; however, their coarse spatial resolution limits the detection of fine-scale melt features. To address this limitation, we propose PMTB-VSRnet, a video super-resolution network with radiometric consistency guidance for Antarctic passive microwave data. In PMTB-VSRnet, neighboring frames are first aligned using Pyramid, Cascading and Deformable (PCD) alignment, while low-frequency Normalized Cross-Correlation (NCC)-guided fusion enhances radiometric feature consistency and suppresses unreliable observations. The aligned features are then propagated bidirectionally to exploit temporal information and reconstruct fine-scale brightness temperature structures. Finally, a radiometric high-frequency constraint is introduced to enhance reconstruction accuracy. Extensive experiments on AMSR2 multi-channel data show that PMTB-VSRnet outperforms all compared methods, improving PSNR over the average performance of the competing methods by 1.57, 2.30, 2.47, and 2.81 dB for the 36.5 H, 36.5 V, 18.7 H, and 18.7 V channels, respectively, under a 4 & times; super-resolution setting. Additional experiments across diverse Antarctic terrains, seasons, and continent-scale regions further demonstrate the robustness and scalability of the proposed framework. The source code is publicly available at https://github.com/jingli1999/PMTB-VSRnet.

Long-term in-situ glacier mass balance records on central Tibetan Plateau (TP) are pivotal for assessing climate change impacts, yet the drivers of extreme mass loss events remain poorly understood. Here, we examined Xiao Dongkemadi Glacier, which possesses the longest continuous mass balance record on central TP, to address this knowledge gap. We identified three extreme mass loss events (2005/2006: −917 mm w.e., 2009/2010: −1066 mm w.e., and 2021/2022: −881 mm w.e.), with magnitudes 3.3, 3.8, and 3.1 times the 1989−2022 average annual mass loss, respectively. Return period analysis indicated that these events were statistically rare, with the 2009/2010 mass loss representing an approximately 1-in-39.1-year event. These extreme events were closely associated with pronounced June−September heatwaves in 2006, 2010, and 2022, driven by anomalies in the surface energy balance characterized primarily by increased absorbed shortwave radiation. Interannual mass balance variability was significantly correlated with mid-latitude zonal winds (r = 0.4, p < 0.05). Further analysis revealed that extreme mass loss events were closely associated with anomalously weak and northward-shifted zonal winds (p < 0.05). This pattern was distinctly different from that in years of positive mass balance. Based on unique long-term measurements, this study provided detailed analysis of extreme mass loss events on central TP, advancing the mechanistic understanding of their drivers and offering critical insights into the future state and fate of glaciers and their implications for water resource management under climate change.

Ice shelves affect the stability of ice sheets by supporting the mass balance of ice upstream of the grounding line. Marine ice, formed from supercooled water freezing at the base of ice shelves, contributes to mass gain and affects ice dynamics. Direct measurements of marine ice thickness are rare due to the challenges of borehole drilling. Here we assume hydrostatic equilibrium to estimate marine ice distribution beneath the Amery Ice Shelf (AIS) using meteoric ice-thickness data obtained from radio-echo sounding collected during the Chinese National Antarctic Research Expedition between 2015 and 2019. This is the first mapping of marine ice beneath the AIS in nearly 20 years. Our new estimates of marine ice along two longitudinal bands beneath the northwest AIS are spatially consistent with earlier work but thicker. We also find a marine ice layer exceeding 30 m of thickness in the central ice shelf and patchy refreezing downstream of the grounding line. Thickness differences from prior results may indicate time-variation in basal melting and freezing patterns driven by polynya activity and coastal water intrusions masses under the ice shelf, highlighting that those changes in ice-ocean interaction are impacting ice-shelf stability.

Automated sea ice mapping is increasingly critical for global climate change research and Arctic shipping route planning. In this article, a dual-branch deep learning architecture with channel attention is proposed for multisource sea ice mapping, incorporating an adaptive multitask loss function weighting mechanism. The Ready-To-Train (RTT) AI4Arctic Sea Ice Challenge dataset is used to evaluate the performance of the proposed model. Experimental results demonstrate that compared with the current state-of-the-art model, the proposed model achieves a 1.03% improvement in the combined score. Specifically, the stage of development (SOD) F1 score increases by 1.33%, the floe size (FLOE) F1 score improves by 4.39%, whereas R-2 for sea ice concentration (SIC) decreases by 1.35%. Finally, ablation experiments are conducted to validate the effectiveness of the proposed model and the adaptive multitask loss function.

There is little known about dynamics of mélange inside large rifts in Antarctic ice shelves and its role in rift propagation and the weakening of shelf stability. This lack of knowledge hinders our capability for long-term forecasting of the Antarctic ice sheet contribution to global sea level rise. We propose an innovative multi-temporal DEM adjustment model (MDAM) that builds a multi-satellite DEM time series from meter-level resolution small DEMs across large Antarctic ice shelves by removing biases, as large as ~6 m in elevation, caused by tides, ice flow dynamics, and observation errors. Using 30 REMA and ZY-3 sub-DEMs, we establish a cross-shelf DEM time series from 2014 to 2021 for the Filchner-Ronne Ice Shelf, the second largest in Antarctica. This unified and integrated DEM series, with an unprecedented submeter elevation accuracy, reveals quantitative 3D structural and mélange features of a ~50 km long rift, including rift lips, flank surface, pre-mélange cavities, and mélange elevations. We report that while the mélange elevation decreased by 2.1 m from 2014 to 2021, the mélange within the rift experienced a rapid expansion of (7.93±0.03) × 109 km3, or 130%. This expansion is attributed to newly calved shelf ice from rift walls, associated rift widening, and other factors related to rift-mélange interactions. The developed MDAM system and the 3D mélange dynamics analysis methods can be applied for research on ice shelf instability and the future contribution of the Antarctic Ice Sheet to global sea level rise.

Front calving is a primary mechanism through which Antarctic ice shelves discharge ice mass into the Southern Ocean. It is an important process that influences ice shelf stability and thus, impacts the Antarctic Ice sheet's contribution to global sea level rise. Mélange dynamics inside rifts is recognized to potentially influence the rift propagation and subsequent iceberg calving. However, large-scale, high-resolution three-dimensional (3D) observations are scarce, which leads to their inability to capture small scale rift dynamics. Ultimately, the lack of knowledge in 3D rift structural changes and mélange dynamics hinders our understanding of the role of mélange in ice shelf retreat and mechanisms underlying the weakening of ice shelf stability. We propose an innovative multi-temporal digital elevation model (DEM) adjustment model (MDAM) to build a multi-satellite DEM time series from meter-level resolution small DEMs. It removes biases across large Antarctic ice shelves, as large as ∼ 6 m in elevation, caused by tides, ice flow dynamics, and observation errors. Using 30 Reference Elevation Model of Antarctica (REMA) and ZY-3 sub-DEMs, we establish a cross-shelf DEM time series from 2014 to 2021 for the Filchner-Ronne Ice Shelf, the second largest ice shelf in Antarctica. This unified and integrated DEM series, with an unprecedented submeter elevation accuracy, reveals quantitative 3D structural and mélange features of two ∼ 50 km long rifts, including rift lips, flank surface, pre-mélange cavities, and mélange elevations. For the first time, we have observed that while the mélange elevation in the rifts decreased by 2.7 ± 0.6 m from 2014 to 2021, the mélange within the rifts experienced a rapid expansion of (10.31 ± 0.03) × 109 m3, or 139 %. This expansion is attributed to newly calved shelf ice from rift walls, associated rift widening, and other factors related to rift-mélange interactions. The developed MDAM system and the 3D mélange dynamics analysis methods can be applied for quantifying ice shelf instability and the future contribution of the Antarctic Ice Sheet to global sea level rise.

The Nioghalvfjerdsfjorden glacier (NG) and Zachariae Isstrøm (ZI) are major contributors to the mass balance of northeast Greenland, which drain 12% of the Greenland Ice Sheet. Accurate measurements of these two glaciers are crucial to the estimation of the mass balance in northeast Greenland. They also serve as an important parameter for reflecting climate change and predicting future sea level rise. In the past, early ice velocity data were scarce, primarily due to challenges in difficulties in image orthorectification caused by large distortions and low quality in historical remote sensing imagery. We proposed a systematic process for orthorectification of CORONA KH-4A imagery, which has proven to be both efficient and accurate in velocity mapping at a precision of 25m. By employing a hierarchical network densification approach based on ARGON KH-5 and CORONA KH-4A imagery, we have successfully reconstructed the ice flow velocity fields for NG and ZI from 1963 to 1967. Combining with other ice velocity products, we have obtained the ice velocity of NG and ZI spanning a period nearly 60 years. The results indicate that the average ice flow velocity near the grounding line has increased by 12.4% for NG and a substantial 81.4% for ZI from 1963 to 2020. While ZI is experiencing accelerated mass loss, the NG is still in a relatively stable state under the similar climate condition. The slight fluctuations in ice velocity for NG may be due to the unique topography and the hindering effect of ice rises, suggesting the climate change may have a comparatively less impact on it.

Understanding basal processes across ice-sheet grounding lines is crucial in accurately modeling ice-sheet dynamics and estimating global sea-level rise. The grounding line, which demarcates the specific boundary between a grounded ice sheet and a floating ice shelf, is notoriously challenging to locate precisely. Existing methods for determining grounding line location rely on indirect methods, such as tide-induced vertical ice-shelf motion (the point of flexure determining the grounding line) and ice-surface slope change (the sharp change in gradient toward being flat indicating the grounding line). In this study, we use ice-penetrating radar (IPR) data to extract grounding line information from the LambertAmery glacier system. By incorporating ice bed topography and the reflection amplitude differences between ice-water and ice-bedrock interfaces, we establish an automated method to extract grounding line positions from radar survey lines. From 53 radar survey lines, we identified 85 grounding points. The comparison with the positions from an existing satellite InSAR-based grounding line product shows an average difference of 0.69 +/- 0.70 km. Tidally-induced migration of grounding lines at different points of the tidal cycle, and advance/retreat of the grounding line with the evolution of the ice shelf, are the main reasons for the discrepancy between the radar-derived results and the existing grounding line products. In general, the results demonstrate the feasibility of IPR in confirming grounding line positions, and show great potential in constraining indirect satellite remote sensing or modeling evaluations at both regional and continental scales. Our work facilitates an ongoing effort of the Scientific Committee on Antarctic Research (SCAR)'s RINGS program to develop gapless coverage of bed topography in the coastal regions around Antarctica.

Mass loss from the Antarctic and Greenland Ice Sheets could lead to a rise in global mean sea level of 0.25 m by 2100 and several metres by 2300 if greenhouse gas emissions remain unmitigated. Uncertainties in these estimates are strongly related to ocean-driven ice melt, which can lead to grounding line retreat, thinning and acceleration of the fast-flowing regions of both Antarctica and Greenland. The processes of ocean-driven ice melt on large spatial and temporal scales are imperfectly known, and measurements are sparse, impacting the accuracy of ice sheet and ocean model projection studies. The Joint Commission on Ice-Ocean Interactions (JCIOI) hosted the first community workshop in October 2022 with the aims to: (1) identify critical knowledge gaps surrounding processes that govern ocean-driven melt of ice sheets across a range of spatio-temporal scales; and (2) identify options to address the knowledge gaps through observing, parameterising, and modelling ice-ocean interactions, and their impacts on ice mass loss and ocean dynamics. Community discussions from the workshop highlighted the need for concurrent and sustained measurements of ice, ocean and atmosphere properties at the ice sheet-ocean interface, and making best use of existing observations to improve models, capture observed changes, better understand physical mechanisms and improve future projections. Building on the workshop outputs, we propose to develop a framework for ice-ocean observations that details the essential measurements that need to be collected, and the temporal and spatial scales on which to measure. This framework will require widespread community engagement on key scientific questions, agreement and coordination, including protocols for data collection, processing, and sharing.

East Antarctic Ice Sheet (EAIS) has an overall balanced or slightly positive mass balance. However, Wilkes Land and Totten Glacier (TG) in EAIS have been losing ice mass significantly since 1989. There is a lack of knowledge of long-term mass balance in the region which hinders the estimation of its contribution to global sea level rise. We reconstruct ice flow velocity fields of 1963–1989 in TG from the first-generation satellite images of ARGON and Landsat-1&4, and build a five decade-long record of ice dynamics. Based on these velocity maps, we show that this acceleration trend in TG has occurred since the 1960s. Combined with recently published velocity maps, we find a persistent long-term ice discharge rate of 68 ± 1 Gt/y and an acceleration of 0.17 ± 0.02 Gt/y2 from 1963 to 2018, making TG the greatest contributor to global sea level rise in EA. We attribute the long-term acceleration near grounding line from 1963 to 2018 to basal melting likely induced by warm modified Circumpolar Deep Water. The speed up in shelf front during 1973–1989 was caused by a large calving front retreat. As the current trend continues, intensified monitoring in the TG region is recommended in the next decades.

We are in a period of rapidly accelerating change across the Antarctic continent and Southern Ocean, with land ice loss leading to sea level rise and multiple other climate impacts. The ice-ocean interactions that dominate the current ice loss signal are a key underdeveloped area of knowledge. The paucity of direct and continuous observations leads to high uncertainty in the glaciological, oceanographic and atmospheric fields required to constrain ice-ocean interactions, and there is a lack of standardised protocols for reconciling observations across different platforms and technologies and modelled outputs. Funding to support observational campaigns is under increasing pressure, including for long-term, internationally coordinated monitoring plans for the Antarctic continent and Southern Ocean. In this Practice Bridge article, we outline research priorities highlighted by the international ice-ocean community and propose the development of a Framework for UnderStanding Ice-Ocean iNteractions (FUSION), using a combined observational-modelling approach, to address these issues. Finally, we propose an implementation plan for putting FUSION into practice by focusing first on an essential variable in ice-ocean interactions: ocean-driven ice shelf melt.

The occurrence of Supraglacial Lakes (SGLs) may influence the signals acquired with microwave radiometers, which may result in a degree of uncertainty when employing microwave radiometer data for the detection of surface melt. Accurate monitoring of surface melting requires a reasonable assessment of this uncertainty. However, there is a scarcity of research in this field. Therefore, in this study, we computed surface melt in the vicinity of Automatic Weather Stations (AWSs) by employing Defense Meteorological Satellite Program (DMSP) Ka-band data and Soil Moisture and Ocean Salinity (SMOS) satellite L-band data and extracted SGL pixels by utilizing Sentinel-2 data. A comparison between surface melt results derived from AWS air temperature estimates and those obtained with remote sensing inversion in the two different bands was conducted for sites below the mean snowline elevation during the summers of 2016 to 2020. Compared with sites with no SGLs, the commission error (CO) of DMSP morning and evening data at sites where these water bodies were present increased by 36% and 30%, respectively, and the number of days with CO increased by 12 and 3 days, respectively. The omission error (OM) of SMOS morning and evening data increased by 33% and 32%, respectively, and the number of days with OM increased by 17 and 21 days, respectively. Identifying the source of error is a prerequisite for the improvement of surface melt algorithms, for which this study provides a basis.

The Pine Island Glacier (PIG) is becoming increasingly unstable as a result of global warming, with profound implications for Antarctic mass loss and sea level rise. To study the mass balance of the Antarctic Ice Sheet, accurate ice flow velocity data are essential. However, ice flow velocity products for this glacier are mainly available after the 1990s. We proposed an ice flow velocity estimating method that includes image pre-processing, image orthorectification and hierarchical matching based on Landsat and KH-9 Hexagon images. In this study, a map of the ice flow velocity of the PIG from 1973 to 1975 is generated using these images, allowing the time span of the PIG ice flow to be extended to the 1970s. The results show that the ice flow velocity has increased and in an accelerated state since the 1970s. The results offer a perspective for the study of PIG dynamics and provide a basis for estimating changes in the mass balance.

The firn temperature is a crucial parameter for understanding firn densification processes of the Antarctic Ice Sheet (AIS). Simulations with firn densification models (FDM) can be conceptualized as a function that relies on forcing data, comprising temperature and surface mass balance, together with tuning parameters determined based on measured depth-density profiles from different locations. The simulated firn temperature is obtained in the firn densification models by solving the one-dimensional heat conduction equation. Microwave satellite data on brightness temperature at different frequencies can also provide remote sensing monitoring of firn temperature variations across the AIS (i.e., the L-band up to 1500 meters). The firn temperature can be estimated by the microwave emission model and the regression method, but these two methods need more observations of temperature profiles for correction and validation. Therefore, we compiled a dataset with temperature profiles and temperature observations with depth around 10 meters. In this work, two methods were used to simulate/retrieve firn temperature across the Antarctic ice sheet. One method estimated the temperature profiles by solving the one-dimensional heat conduction equation driven by reanalyses and regional climate models, which are used in the simulation of FDMs. The other one established a relationship between the multi-frequency brightness temperature data from microwave remote sensing satellites and the firn temperature.

罗斯冰架、菲尔希纳-龙尼冰架和埃默里冰架是南极的三大冰架,对南极冰盖有着重要的支撑作用.然而,目前三大冰架稳定性的研究多集中在一种或几种因素,缺少多参数的综合评估.为实现南极三大冰架不稳定性和长时序变化趋势系统的分析,本文综合统计、分析了三大冰架的关键参数变化,包括三大冰架的表面高程、底部融化、表面融水、关键裂缝、缝合区、前缘线、接地线、冰流速以及物质平衡变化.此外,本文选取了南极已经崩塌的拉森B冰架、处在快速变化且已发生结构性变化的松岛冰架和处于加速状态的托滕冰架作为参考冰架,将三大冰架与参考冰架对应的关键参数进行对比分析,最终确定南极三大冰架的变化状态和稳定性趋势.研究结果表明,三大冰架的多项关键参数与参考冰架相比均变化较小,有50%的参数小于加速变化状态的托滕冰架,有88%的参数小于快速变化状态的松岛冰架,有100%的参数小于崩塌状态的拉森B冰架;并且对未小于托滕冰架的参数具体分析后,发现其符合三大冰架稳定状态的情况.因此,目前三大冰架处于稳定的自然变化状态,短期内不会发生剧烈的结构性变化.但在全球气候变暖的情形下,该变化趋势存在较大的不确定性,需长期进行追踪观测从而评估其对全球海平面上升的影响.