Laurie Padman

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 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.

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.

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.

Antarctica is a vital component of Earth’s climate system, influencing global sea level, ocean circulation, and planetary albedo. Major knowledge gaps in critical processes—spanning the atmosphere, ocean, ice sheets, underlying beds, ice shelves, and sea ice—create uncertainties in future projections, hindering climate adaptation and risk assessments of ice intervention strategies. Antarctica’s ice sheet could contribute 28 centimeters to sea level by 2100, and potentially more if we surpass warming thresholds that trigger instabilities and rapid retreat. We review recent advances in understanding the changing stability of the ice sheet margins and identify key processes that require further research. Progress requires high-resolution satellite data, targeted field campaigns, improved modeling, and refined theory. Increased investment and interdisciplinary collaboration are essential to uncovering Antarctica’s hidden processes and reducing uncertainties in future projections.

A holistic review is given of the Southern Ocean dynamic system, in the context of the crucial role it plays in the global climate and the profound changes it is experiencing. The review focuses on connections between different components of the Southern Ocean dynamic system, drawing together contemporary perspectives from different research communities, with the objective of closing loops in our understanding of the complex network of feedbacks in the overall system. The review is targeted at researchers in Southern Ocean physical science with the ambition of broadening their knowledge beyond their specific field, and aims at facilitating better‐informed interdisciplinary collaborations. For the purposes of this review, the Southern Ocean dynamic system is divided into four main components: large‐scale circulation; cryosphere; turbulence; and gravity waves. Overviews are given of the key dynamical phenomena for each component, before describing the linkages between the components. The reviews are complemented by an overview of observed Southern Ocean trends and future climate projections. Priority research areas are identified to close remaining loops in our understanding of the Southern Ocean system.