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Abstract. In the coming decades increasing amounts of freshwater are predicted to enter the subpolar North Atlantic from Greenland and the Arctic. If this additional freshwater reaches the regions where deep convection occurs, it could potentially dampen ventilation and the formation of deep waters. In this study, we use a surface drifter dataset spanning the period 1990–2023 to investigate the pathways followed by waters originating from Davis Strait and Hudson Strait on the Labrador shelf and into the interior subpolar North Atlantic. Recent drifter deployments in the region allow for an improved understanding of the circulation on the Labrador shelf, in particular its northern part, where prior data were sparse. We show that waters originating from Davis Strait and Hudson Strait remain on the shelf as they flow downstream until they reach the Newfoundland shelf. This confirms that very little exchange takes place between the Labrador shelf and the interior Labrador Sea. Decomposing the Labrador shelf into five regions, we further describe typical pathways for these waters and show that extensive exchanges take place between the coastal and shelf-break branches of the Labrador Current. Our results suggest that if an increasing amount of freshwater reaches the Labrador shelf, it would not directly affect the Labrador Sea convection region; instead, it would lead to the formation of a salinity anomaly off the Grand Banks, which could then circulate around the subpolar North Atlantic. 

Abstract A mooring array has been maintained across the West Greenland shelf and slope since 2014 as part of the Overturning in the Subpolar North Atlantic Program (OSNAP). Here, we use the first 8 years of data to investigate the interannual variability of the two overflow water components of the deep western boundary current (DWBC): the Denmark Strait Overflow Water (DSOW) and the Northeast Atlantic Deep Water (NEADW). While the velocity structure has remained similar throughout the record, both water masses have freshened considerably, especially the NEADW salinity core. Using revised density criteria to define these two components, their transports decreased significantly between 2014 and 2022: from 6.2 to 3.8 Sv (1 Sv ≡ 10⁶m³s⁻¹) (−0.33 Sv yr⁻¹) for the DSOW and from 5.4 to 4.1 Sv (−0.19 Sv yr⁻¹) for the NEADW. Since the overflows across the Denmark Strait and the Faroe Bank Channel have remained steady over this period, this points to decreased entrainment downstream of the sills as a possible mechanism for the observed transport reduction south of Greenland. Using shipboard and mooring data from the two sills, and a hydrographic database for the surrounding region, we predict the downstream transport of the two DWBC components via the framework of a streamtube model. The predicted transport explains 94% of the observed DSOW trend and 63% of the observed NEADW trend. This implies that further entrainment of the NEADW must occur during its long pathlength, which would also help explain the fresher-than-predicted NEADW salinity observed at the OSNAP array. 

Abstract. The strength of the Atlantic meridional overturning circulation(AMOC) at 26∘ N has now been continuously measured by the RAPIDarray over the period April 2004–September 2018. This record provides uniqueinsight into the variability of the large-scale ocean circulation,previously only measured by sporadic snapshots of basin-wide transport fromhydrographic sections. The continuous measurements have unveiled strikingvariability on timescales of days to a decade, driven largely bywind forcing, contrasting with previous expectations about a slowly varyingbuoyancy-forced large-scale ocean circulation. However, these measurementswere primarily observed during a warm state of the Atlantic multidecadalvariability (AMV) which has been steadily declining since a peak in2008–2010. In 2013–2015, a period of strong buoyancy forcing by theatmosphere drove intense water-mass transformation in the subpolar NorthAtlantic and provides a unique opportunity to investigate the response ofthe large-scale ocean circulation to buoyancy forcing. Modelling studiessuggest that the AMOC in the subtropics responds to such events with anincrease in overturning transport, after a lag of 3–9 years. At45∘ N, observations suggest that the AMOC may already beincreasing. Examining 26∘ N, we find that the AMOC is no longerweakening, though the recent transport is not above the long-term mean.Extending the record backwards in time at 26∘ N with oceanreanalysis from GloSea5, the transport fluctuations at 26∘ N areconsistent with a 0- to 2-year lag from those at 45∘ N, albeit withlower magnitude. Given the short span of time and anticipated delays in thesignal from the subpolar to subtropical gyres, it is not yet possible todetermine whether the subtropical AMOC strength is recovering nor how theAMOC at 26∘ N responds to intense buoyancy forcing.