The Atlantic Subtropical Front/Current Systems of Azores and St. Helena

Abstract

A large-scale climatic ocean circulation model was used to study the Atlantic Ocean circulation. This inverse model is an extension of the β-spiral formulation presented in papers by Stommel and Schott with a more complete version of the vorticity equation, including relative vorticity in addition to planetary vorticity. Also, a more complete database for hydrological measurements in the Atlantic Ocean was used, including not only the National Oceanographic Data Center database but also World Ocean Circulation Experiment data and cruises near the Azores, Angola, and Guinea-Bissau. A detailed analysis of the Northern Hemisphere Azores Current and Front shows that this new database and the model results were able to capture all major features reported previously. In the Southern Hemisphere, the authors have identified fully and described the subtropical front that is the counterpart to the Azores Current, which they call the St. Helena Current and Front. Both current systems of both hemispheres have similar intensities, depth penetration, volume transports, and zonal flow. Both have associated subsurface adjacent countercurrent flows, and their main cores flow at similar latitudes (∼34°N for the Azores Current and 34°S for the St. Helena Current). It is argued that both current systems and associated fronts are the poleward 18°C Mode Water discontinuities of the two Atlantic subtropical gyres and that both originate at the corresponding hemisphere western boundary current systems from which they penetrate into the open ocean interior. Thus, both currents should have a similar forcing source, and their origin should not be linked to any geographical peculiarities.

Population Structure and Dispersal Patterns within and between Atlantic and Mediterranean Populations of a Large-Range Pelagic Seabird

“…We suggest that a possible cause of the close genetic similarities between Berlenga-Canaries and Selvagem-Azores populations may lie in extensive recruitment from one of these colonies after recent human persecution. Another non exclusive explanation would be that greater connectivity due, for example to different wind patterns, may have allowed birds to move easily between these colonies (see [14], [73]). Interestingly, the stronger population structure in the Atlantic subspecies was noted when analyzing DNA fingerprinting [18], and led these authors to suggest that the Mediterranean subspecies had only recently radiated from a founder group of Atlantic individuals.…”

“…However, it would seem that differences in vocalizations would not act as a reproductive barrier as a male with Atlantic accent mated with a Mediterranean female on a Mediterranean colony [29]. Additionally, also at a lower scale, vocalizations differ between archipelagos and islands [73], showing the existence of a geographic variation of acoustics parameters [35], [75].…”

A century of research on the larval distributions of the Atlantic eels: a re‐examination of the data

“…24). The Azores Current is usually located between latitudes of 33 and 35 • N and can often be a strong jet-like current (Siedler, Zenk & Emery, 1985;Klein & Siedler, 1989;Alves et al, 2002;Juliano & Alves, 2007), so the leptocephali that remain in the southern part of the Gulf Stream flow could enter this current and experience rapid transport across much of the basin (Fig. The Azores Current is usually located between latitudes of 33 and 35 • N and can often be a strong jet-like current (Siedler, Zenk & Emery, 1985;Klein & Siedler, 1989;Alves et al, 2002;Juliano & Alves, 2007), so the leptocephali that remain in the southern part of the Gulf Stream flow could enter this current and experience rapid transport across much of the basin (Fig.…”

The Azores Confluence Zone

“…The oceanographic conditions in the Mid-Atlantic Ridge (MAR) region adjacent to the Azores Archipelago has been the subject of many scientific studies (e.g., Gould, 1985;Mailly et al, 1997;Alves and Verdière, 1999;Pingree et al, 1999;Alves et al, 2002;Juliano and Alves, 2007;Søliland et al, 2008;Barbosa et al, 2011;Lázaro et al, 2013). Fewer studies however, center on the oceanographic processes affecting the Azores Islands per se.…”