ABSTRACT
Continuous satellite observations of Antarctic sea-ice from 1979 onward reveal a very dynamic seasonal sea-ice cover with high variability on daily-to-decadal timescales. Superimposed on this high variability was a small slow increase in monthly Antarctic sea-ice extent over the period 1979–2015. This increase in circumpolar averaged sea-ice extent consisted of either large but regionally contrasting sea-ice changes (at magnitudes equivalent to Arctic sea-ice changes) or regions showing very little change. In contrast, the last decade has been extraordinary, first punctuated by sequential record-high monthly values during 2012 to mid-2015, then suddenly record-low values in late 2016, with anomalously low to record-low monthly values persisting thus far through 2024. Here, we identify and discuss several outstanding issues, including atmospheric versus oceanic drivers, the influence of wind and waves, warming versus freshening, the role of sea-ice in mediating climate feedbacks, and the successes and challenges in modeling and predicting Antarctic sea-ice change. We conclude with a summary of outstanding questions and identify future directions.
