The Seasonal Cycle of the Eastern Boundary Currents of the North Atlantic Subtropical Gyre

Abstract

At the eastern region of the North Atlantic Subtropical Gyre, the Canary Current (CC) connects the Azores Current with the North Equatorial Current (Hernández-Guerra et al., 2005;Pérez-Hernández et al., 2013) (Figure 1a). The first studies carried out in the region used historical hydrographic data to determine the existence of a seasonal change in the structure of the eastern subtropical gyre. These studies found a CC flowing closer to the African coast in summer and through the western islands in winter (Stramma & Isemer, 1988;Stramma & Müller, 1989). Using one hydrographic cruise per season carried out between Madeira and north of the Canary Islands (at 28-32°N) in and 1998, Machín et al. (2006 reported that the CC presents a seasonal cycle characterized by a southward mass transport of −1.7 ± 1.0 Sv in winter, −2.8 ± 1.0 Sv in spring, −2.9 ± 1.1 Sv in summer, and −4.5 ± 1.2 Sv in fall with a shift westward from spring to fall. Pérez-Hernández et al. (2013) confirmed that CC migrates west of the Canary Islands in fall and described a mass transport of −5.8 ± 0.2 Sv southward. In addition, both Fraile-Nuez and Hernández-Guerra (2006) using Argo data, and Mason et al. (2011)