Autumn pauses in Arctic-wide sea-ice expansion

Abstract In a typical year, Arctic sea-ice extent (SIE) exhibits uninterrupted growth in autumn (October–December), but on some rare occasions (13 times 1979–2023), that expansion has paused for at least 6 days. Eleven of 13 autumn pause events are characterized by net ice loss in the Barents and Kara Seas. The common driver of this loss is the passage of a series of anomalously strong extratropical cyclones into the East Greenland Sea, bringing strong southerly or southeasterly winds into the Barents and Kara Seas, pushing the ice edge polewards and inhibiting additional growth. Temporal clustering of cyclone tracks and the intensity of the southerly flow is often coincident with exceptional high pressure and blocking to the east (the Kara Sea or western Russia). In four cases, sea-ice loss in the Nordic seas is combined with similar atmospheric anomalies in the Pacific sector. Autumn expansion pauses are as common today as in the past because of two competing regime shifts that occurred in 2005: the average autumn SIE expansion rate is now faster, but that expansion rate is also more variable since thinner ice is more responsive to atmospheric anomalies.