Antarctic sea ice plays a crucial role in the global climate system, influencing ocean-atmosphere interactions, ocean circulation, ice-sheet stability, surface mass balance, and ecosystems. Since 2016, after a period of slight long-term increase (1979-2014), Antarctic sea ice has exhibited frequent record lows, drawing significant attention. The February 2023 minimum of 1.79 million km², 6.8% lower than the 2022 minimum and 30% lower than the 1981–2010 climatology, marked a new record low. Understanding the mechanisms behind these extremes requires examining atmospheric, oceanic, and sea ice processes across various scales. Previous studies on record low sea ice events, such as 2016-2017, identified several drivers, including anomalous atmospheric meridional heat advection, a deepened ASL, Southern Annular Mode (SAM) variability, and subsurface ocean warming. These anomalies have been linked to remote drivers like ENSO, IOD, stratospheric circulation anomalies, and decadal SST variability. The 2022 and 2023 minima occurred during a positive SAM but were also influenced by anomalously warm subsurface ocean conditions. The lagged impact of a deepened ASL on summer sea ice through enhanced sea ice export and ice-albedo feedback has been suggested as an important factor. This study investigates the year-round (March 2022–February 2023) evolution leading to the 2023 record low using satellite observations, reanalyses, and the Pan-Antarctic Regional Ocean-sea ice coupled model (PAROC) to understand the interplay between atmospheric, oceanic, and sea ice processes.

Prior research on Antarctic sea ice minima, particularly the 2016-2017 event, highlighted various contributing factors. These included anomalous atmospheric heat advection linked to positive SAM patterns, a deepened Amundsen Sea Low (ASL), record-negative SAM values, and subsurface ocean warming. Remote influences such as ENSO, IOD, stratospheric circulation anomalies, and tropical SST variability were also implicated. Studies on subsequent minima, like those in 2022 and 2023, emphasized the roles of positive SAM and warm subsurface ocean conditions. The delayed effect of an intensified ASL on summer sea ice via enhanced sea ice export and ice-albedo feedback has been proposed as a crucial mechanism. However, the precise interplay of these factors, especially the specific conditions leading to the 2023 anomaly, remained unclear, necessitating further investigation into the controlling processes.

This study employed a comprehensive approach combining multiple datasets and modeling techniques to unravel the factors behind the 2023 record low Antarctic sea ice extent. The methodology encompassed: 1. **Observations:** Daily 25 km gridded sea ice concentration (SIC) products from the National Snow and Ice Data Center (NSIDC) were utilized, covering the period from 1979 to 2023. Daily NSIDC ice extent data provided consistent sea ice extent information since 1979. 2. **Reanalyses:** Monthly mean sea level pressure (SLP), 2-meter air temperature, 10-meter wind, 1000-hPa air temperature and wind, and surface heat fluxes were obtained from ERA5 reanalysis for 1979–2023. Temperature advection at 1000 hPa was calculated. 3. **Modeling:** A Pan-Antarctic Regional Ocean-sea ice coupled model (PAROC), based on the NEMO3.6 ocean model coupled with the LIM3.6 sea ice model, was used. PAROC covers the Southern Ocean south of 30°S with a horizontal resolution close to 1/4° and 75 vertical levels. The model was driven by ERA5 atmospheric reanalysis and forced by ORAS5 ocean reanalysis at the boundaries. Model performance was evaluated against observations before analyzing sea ice volume (SIV) and thickness (SIT) budgets. The sea ice volume flux was calculated using modeled SIC, SIT, and sea ice velocity.

The analysis revealed several key characteristics of the 2022-2023 Antarctic sea ice annual cycle: 1. **Consistently Low SIE:** Below-average SIE prevailed throughout the entire year, starting as early as February 2022, indicating the importance of prior conditions. 2. **Rapid Sea Ice Retreat:** Unusually high sea ice retreat rates were observed in December 2022, accelerating sea ice loss towards the summer minimum. 3. **Circumpolar Anomalies:** Nearly circumpolar negative sea ice concentration (SIC) anomalies were present in February 2023, with particularly significant negative anomalies in the Amundsen, Bellingshausen, and Ross Seas. 4. **Amundsen-Ross Sea Dynamics:** The study focused on the Amundsen-Ross Sea region due to its substantial contribution to the overall SIE reduction. A deepened ASL resulted in strong southerly winds that transported sea ice northward along the coast, creating large open water areas. This enhanced solar radiation absorption, triggering positive ice-albedo feedback and accelerating melting. Model simulations showed that extreme transport-induced melt dominated SIT changes from October to late November 2022. Later, surface melt became significant, accompanied by negative SIC anomalies. Oceanic-related melt dominated towards the end of December. 5. **Ice-Albedo Feedback:** Increased absorption of solar radiation in the Amundsen-Ross Sea, attributable to a less reflective surface (lower albedo) due to open water, fueled the positive ice-albedo feedback, leading to accelerated melting. 6. **ASL Influence:** The persistent ASL played a crucial role, driving the transport of sea ice and the subsequent ice-albedo feedback. However, the relationship between ASL and sea ice response appears non-stationary, with the impact varying depending on regional and seasonal factors.

The findings demonstrate the synergistic effects of atmospheric, oceanic, and sea ice processes in driving the record low 2023 Antarctic sea ice extent. The interplay between the deepened ASL, resulting southerly winds, and the subsequent ice transport and ice-albedo feedback in the Amundsen-Ross Sea was pivotal. The study highlights the importance of considering pre-existing conditions and the complex feedback mechanisms involved in Antarctic sea ice variability. The non-stationary relationship between ASL and sea ice response underscores the need for further research into the changing dynamics of the coupled system. The results contribute to a better understanding of the mechanisms driving recent record low sea ice events and highlight potential implications for future Antarctic sea ice changes.

The 2023 Antarctic sea ice minimum was a culmination of year-round low SIE, exceptionally rapid sea ice retreat in December 2022, and widespread negative SIC anomalies. The study reveals the crucial role of the Amundsen Sea Low and associated winds in transporting sea ice and initiating positive ice-albedo feedback, leading to accelerated melting. Future research should focus on improving the understanding of the non-stationary nature of the relationship between ASL variability and sea ice responses, refining the representation of coupled ocean-atmosphere-sea ice processes in models, and enhancing the accuracy of SIT observations to better constrain model simulations.

While the study used a comprehensive approach, some limitations exist. The model, while well-evaluated, may have inherent biases. The analysis relies on reanalysis data, which have uncertainties. Furthermore, the complex interplay of various processes makes isolating individual contributions challenging. More accurate SIT observations are needed to further refine model evaluations and enhance understanding of the dynamics involved.