Interannual variability of the meridional overturning circulation in the subpolar North Atlantic

Variability of the Atlantic Meridional Overturning Circulation (MOC) has drawn extensive attention due to the MOC’s impact on global heat and freshwater redistribution. The Overturning in the Subpolar North Atlantic Program (OSNAP) array, consisting of an OSNAP West section covering the Labrador Sea and an OSNAP East section covering the eastern subpolar basins (Irminger and Iceland Basins), has continuously observed the MOC and meridional heat and freshwater transports since 2014. The OSNAP observations have contributed substantially to the understanding of the mean state and sub-seasonal to seasonal variability of the subpolar MOC. In this study, we present the latest OSNAP observational results and investigate interannual variability of the subpolar MOC with respect to water mass transformation and formation in the Labrador Sea and eastern subpolar basins. We detail the differences between formation and transformation in each of these basins and discuss their relationships to overturning on monthly and interannual time scales. Finally, we explore the mechanism(s) responsible for these differences.