Contradictory Pathways between Labrador Sea Water Advection and Property Propagation

Past observational studies have shown a strong relationship between Labrador Sea Water (LSW) property variability and property anomalies in the western subtropical gyre, with the former leading the latter by around 10 years. This time scale stands in contradiction to recent studies that have revealed a much longer advective time scale for LSW to enter the subtropical gyre. Using simulated floats from an ocean general circulation model, we show that LSW is not directly exported to the subtropical gyre, but rather recirculates within the subpolar gyre before it crosses the inter-gyre boundaries, primarily through interior pathways. The average age of LSW upon entering the subtropical basin is 22 (± 10) years. Once in the subtropical basin, LSW is advected from the central and eastern regions to the western region, where it joins the Deep Western Boundary Current with an average age of 30 (± 8) years. This spreading pattern of LSW trajectories differs markedly from the apparent pathway of LSW salinity anomalies: a cross correlation map of observational salinity anomalies in the Labrador Sea with those across the entire North Atlantic, reveals a direct and relatively fast propagation pathway along the western boundary, which takes 10-12 years to reach 30°N. Ongoing research to understand the mechanisms of LSW trajectory and property pathways will be discussed.