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. After more than a decade of shallow convection, deep convection returned tothe Irminger Sea in 2008 and occurred several times since then to reachexceptional convection depths (> 1500 m) in 2015 and 2016.Additionally, deep mixed layers deeper than 1600 m were also reportedsoutheast of Cape Farewell in 2015. In this context, we used Argo data toshow that deep convection occurred southeast of Cape Farewell (SECF) in 2016and persisted during two additional years in 2017 and 2018 with a maximumconvection depth deeper than 1300 m. In this article, we investigate therespective roles of air–sea buoyancy flux and preconditioning of the watercolumn (ocean interior buoyancy content) to explain this 4-year persistenceof deep convection SECF. We analyzed the respective contributions of theheat and freshwater components. Contrary to the very negative air–seabuoyancy flux that was observed during winter 2015, the buoyancy fluxes overthe SECF region during the winters of 2016, 2017 and 2018 were close to theclimatological average. We estimated the preconditioning of the water columnas the buoyancy that needs to be removed ( B ) from the end-of-summer watercolumn to homogenize it down to a given depth. B was lower for the winters of 2016–2018 than for the 2008–2015 winter mean, especially due to a vanishingstratification from 600 down to ∼1300  m. This means thatless air–sea buoyancy loss was necessary to reach a given convection depththan in the mean, and once convection reached 600 m little additionalbuoyancy loss was needed to homogenize the water column down to 1300 m. Weshow that the decrease in B was due to the combined effects of the localcooling of the intermediate water (200–800 m) and the advection of anegative S anomaly in the 1200–1400 m layer. This favorablepreconditioning permitted the very deep convection observed in 2016–2018despite the atmospheric forcing being close to the climatological average.

Why did deep convection persist over four consecutive winters (2015–2018) southeast of Cape Farewell?