Antarctic sea ice extent has shown increased variability since 2014. Although this variability has been attributed to a combination of oceanic and atmospheric forcings, considerable uncertainties remain. In coastal Antarctica, an important source of sea ice variability is the formation of polynyas and outbreaks of landfast sea ice, which are both influenced by complex atmospheric processes. While these processes can strongly impact regional sea ice variability, the links between large-scale atmospheric dynamics and regional sea ice extent remain incompletely understood. To address this gap, we investigate the sea ice extent in the McMurdo Sound during 2013–2024 using sea ice concentration data from the Japanese JAXA's GCOM-W1 satellite. More specifically, the study first introduces a pragmatic approach to identify polynya opening and fast ice breakout events from the satellite data (the sum of them referred to as “breakout events”) and then investigates local atmospheric flow anomalies and large-scale dynamical processes that influenced the interannual variability of breakout events. The results show that (i) the total number of breakout events varies between 3 and 8 per winter period (April to August), with mainly polynya openings until 2018 and mainly fast ice breakout events in the later years; (ii) in agreement with previous studies, breakout events are associated with strong southerly winds (typically >10 ms<sup>-1</sup>) (iii) breakout events are further associated with warm anomalies of about 8 K at Marble Point; (iv) breakout events are related to the formation of the Ross Ice Shelf airstream, which is a barrier wind regime extending over more than 500 km along the Transantarctic Mountains; (v) breakout events (and the Ross Ice Shelf airstream) occur in response to enhanced large-scale sea level pressure gradients induced by (intense) cyclones in the Ross Sea; and (vi) the winter-mean frequency of Ross Sea cyclones correlates highly with the number of breakout events per winter. Together, our results reveal how large-scale atmospheric dynamics, particularly the frequency and intensity of Ross Sea cyclones, drive the formation and frequency of sea ice outbreak events and thus interannual sea ice variability in McMurdo Sound.<span> </span>