Mid-depth Lagrangian pathways in the North Atlantic and their impact on the salinity of the eastern subpolar gyre

• Published in: Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2011-12, Vol.58 (12), p.1196-1204
• Main Authors: Burkholder, Kristin C., Lozier, M. Susan
• Format: Article
• Language: English
• Subjects: Anomalies; Density; Dynamics of the ocean (upper and deep oceans); Earth, ocean, space; Eastern North Atlantic; Exact sciences and technology; External geophysics; Fresh water; Gyres; Lagrangian pathways; Latitude; Marine; Mediterranean overflow water; Ocean currents; Oceanography; Pathway variability; Pathways; Physical oceanography; Physics of the oceans; Salinity; Trajectories; Transport
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2011.08.007

The role of Mediterranean Overflow Water (MOW) in creating subsurface salinity anomalies within the Rockall Trough, a gateway to high latitude areas of deep convection, has been examined closely in recent years. Eulerian investigations of high latitude property fields have suggested that these subsurface anomalies are likely the result of variability in the zonal extent of the eastern limb of the subpolar gyre: when expanded into the eastern North Atlantic, the gyre is presumed to limit the extent to which MOW is able to penetrate northward to subpolar latitudes. However, though the depth of the subsurface salinity anomalies in the Rockall Trough supports the hypothesis that the intermittent presence of MOW is involved in creating the anomalies, MOW pathways to the Rockall Trough have not yet been established. Here, Lagrangian trajectories from floats released in the eastern North Atlantic between 1996 and 1997 and synthetic trajectories launched within an eddy-resolving ocean general circulation model are used to demonstrate that two main density neutral transport pathways lead to the Rockall Trough. One pathway involves the transport of relatively fresh waters as part of the North Atlantic Current and the other involves the transport of relatively salty waters from the eastern reaches of the subtropical North Atlantic. The results from this study indicate that changes in these pathways over time can explain the subsurface salinity variability in the Rockall Trough. ► 2 density neutral transport pathways lead to mid-depths in the Rockall Trough. ► Changes in the contribution of pathways produce salinity changes in the Trough. ► A coherent eastern boundary current is not evident in the Lagrangian frame.