In Austral summer 2016/2017, the sea ice extent (SIE) in the Weddell Sea dropped to a near‐record value in the satellite era (1.88 × 106 km2), a large negative seasonal anomaly that persisted in an unprecedented fashion for the following three summers. Various atmospheric and oceanic factors played a part in the change. Ice loss started in September 2016 when the northern Weddell Sea experienced westerly winds of record strength, advecting multiyear sea ice from the region. In late 2016, a polynya over Maud Rise contributed to low SIE over the eastern Weddell Sea. With extensive areas of open water early in the summer, upper ocean temperatures increased by ~0.5°C, with the anomalies persisting in subsequent years. The reappearance of the Maud Rise polynya in 2017, high ocean temperatures, and storms of record depth kept the summer SIE low.

Antarctic sea ice extent (SIE) has displayed a complex pattern of change over the period for which we have reliable data from passive microwave satellite instruments starting in the late 1970s. Until the mid-1990s there was no significant trend in the annual mean total Antarctic SIE or the extent at the annual minimum (Figure 1a). However, this was followed by an upward trend in both measures, which was accompanied by an increase in the inter-annual variability (Fogt et al., 2022, Figure 1). The overall increase in SIE between the mid-1990s and 2014 masked large regional variations, such as the increase in the Ross Sea and decrease in the Amundsen-Bellingshausen Seas (ABS) (Turner et al., 2015), which was consistent with a deepening of the Amundsen Sea Low (ASL) (Raphael et al., 2015). A number of studies have examined the sea ice increase and suggested it was linked to a range of high latitude and tropical forcing factors (

Satellite observations have shown that the largest and most prolonged Maud Rise open‐ocean polynya since the 1970s appeared on 14 September 2017 (~9.3 × 103 km2) within the seasonal sea‐ice cover which expanded maximum on 1 December 2017 (~298.1 × 103 km2) and existed for 79 days. Record negative anomalies of sea‐ice concentration were observed in and around the polynya. The occurrence of the polynya was associated with a large cyclonic eddy and negative wind stress curl that facilitated melting of sea‐ice. Concurrently, a region of positive sea level pressure anomalies extended over the entire northern Weddell Sea accompanied by record low negative anomalies (deep depressions) over the southwest Weddell Sea and the Maud Rise. The atmospheric circulation anomalies advected moist‐warm air from the midlatitudes, resulted a record atmospheric warming (~11.5 °C) in the Maud Rise that favored this rare event as one of the largest open‐ocean polynyas.