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As the climate warms, the grounded ice sheet and floating ice shelves surrounding Antarctica are melting and releasing additional freshwater into the Southern Ocean. Nonetheless, almost all existing coupled climate models have fixed ice sheets and lack the physics required to represent the dominant sources of Antarctic melt. These missing ice dynamics represent a key uncertainty that is typically unaccounted for in current global climate change projections. Previous modelling studies that have imposed additional Antarctic meltwater have demonstrated regional impacts on Southern Ocean stratification, circulation, and sea ice, as well as remote changes in atmospheric circulation, tropical precipitation, and global temperature. However, these previous studies have used widely varying rates of freshwater forcing, have been conducted using different climate models and configurations, and have reached differing conclusions on the magnitude of meltwater–climate feedbacks. The Southern Ocean Freshwater Input from Antarctica (SOFIA) initiative brings together a team of scientists to quantify the climate system response to Antarctic meltwater input along with key aspects of the uncertainty. In this paper, we summarize the state of knowledge on meltwater discharge from the Antarctic ice sheet and ice shelves to the Southern Ocean and explain the scientific objectives of our initiative. We propose a series of coupled and ocean–sea ice model experiments, including idealized meltwater experiments, historical experiments with observationally consistent meltwater input, and future scenarios driven by meltwater inputs derived from stand-alone ice sheet models. Through coordinating a multi-model ensemble of simulations using a common experimental design, open data archiving, and facilitating scientific collaboration, SOFIA aims to move the community toward better constraining our understanding of the climate system response to Antarctic melt. [ABSTRACT FROM AUTHOR]

Few ice cores from the Amundsen Sea and Bellingshausen Sea sectors of the West Antarctic Ice Sheet (WAIS) extend back in time further than a few hundred years. The WAIS is believed to be susceptible to collapse as a result of anthropogenic climate change and may have at least partially collapsed during the Last Interglacial (LIG) period. Understanding the stability of the WAIS during warm periods such as the LIG and Holocene is important. As part of the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project, the British Antarctic Survey's (BAS) Rapid Access Isotope Drill (RAID) was deployed in 2020 on Sherman Island in the Abbot Ice Shelf, West Antarctica. We drilled a 323 m deep borehole, with discrete samples of ice chippings collected that cover the entire depth range of the drilled ice. The samples were analysed for stable water isotope composition and major ion content at BAS from 2020–2022. Using annual layer counting of chemical records, volcanic horizon identification and ice modelling, an age scale for the record of 1724 discrete samples is presented. The Sherman Island ice record extends back to greater than 1240 years, providing the oldest, continuous ice-derived palaeoclimate records in the coastal Amundsen and Bellingshausen Sea sectors to date. We demonstrate the potential for recovery of a complete Holocene climate record from Sherman Island in the future and confidence in the ability of RAID samples to contain sufficiently resolved records for meaningful climatic interpretation. [ABSTRACT FROM AUTHOR]

Nonlinear trends (i.e. quadratic trends, usually defined as accelerations) in Antarctic ice mass loss due primarily to the complex climate warming forcing regimes have induced large uncertainty to future sea level projection. Here, we quantify the nonlinear and spatially varying mass losses in the Antarctic ice sheet during the last two decades using the satellite gravimetry data collected by Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. We use a regional inversion methodology to generate the mass change time-series over Antarctica. Our findings reveal that seven regions have evidenced significant nonlinear mass change. These regions are all concentrated along the coast of Antarctica and show spatially heterogeneous mass balance nonlinear trend patterns. Among them, the Amundsen Sea Embayment (ASE) and the Dronning Maud Land (DML) are found to be particularly sensitive to short-term climate variability. The GRACE-inferred nonlinear mass balance signal can be confirmed by independent Global Positioning System (GPS) observations, and the difference between the nonlinear vertical deformation trends estimated by GRACE and GPS, especially in ASE, is likely due to the imperfect correction of the glacial isostatic adjustment (GIA) effect. For Antarctic ice sheet as a whole, GRACE satellite gravimetry indicates an ice mass loss of −101.3 ± 18.0 Gt yr−1, with an accelerated loss of −6.4 ± 1.3 Gt yr−2 during 2002–2021. [ABSTRACT FROM AUTHOR]

Several large‐scale components of the climate system may undergo a rapid transition as critical conditions are exceeded. These tipping elements are also dynamically coupled, allowing for a global domino effect under global warming. Here we focus on such cascading events involving the Greenland Ice Sheet (GIS), the West Antarctica Ice Sheet (WAIS) and the Atlantic Meridional Overturning Circulation (AMOC). Using a conceptual model, we study the combined tipping behavior due to three dominant feedbacks: the marine ice sheet instability for the WAIS, the height‐surface mass balance feedback for the GIS and the salt‐advection feedback for the AMOC. We show that, in a realistic parameter range of the model, a tipping of the WAIS can inhibit cascading events by preserving the AMOC stability. Plain Language Summary: In the climate system, the interaction of specific components known as tipping elements are thought to be able to induce a global domino effect, or cascading tipping. In this study, we present a conceptual model containing the most strongly interacting components, namely the Atlantic Meridional Overturning Circulation (AMOC), the Greenland Ice Sheet and the West Antarctica Ice Sheet. We find that the stability of this system as a whole is strongly modified when interactions are included. Especially, while a Greenland Ice Sheet collapse destabilizes the AMOC, the model shows that a collapse of the West Antarctica Ice Sheet might prevent a global cascading event by stabilizing the AMOC. Key Points: A conceptual model of interacting Atlantic Meridional Overturning Circulation (AMOC), Greenland Ice Sheet and West Antarctica Ice Sheet (WAIS) is presentedInteractions between these tipping elements strongly modifies the stability of the whole systemA collapse of the WAIS can prevent tipping of the AMOC [ABSTRACT FROM AUTHOR]