Lateral transports of mass, inorganic nutrients and dissolved oxygen in the Cape Verde Frontal Zone in summer 2017

Abstract

Abstract. The circulation patterns in the confluence of the North Atlantic Subtropical and Tropical gyres delimited by the Cape Verde Frontal Zone (CVFZ) in summer 2017 were examined. Hydrology, dissolved oxygen (O2) and inorganic nutrients data collected in a closed box embracing the CVFZ allowed estimating transports of water masses, O2 and inorganic nutrients for the first time. Higher transports occurred mainly at the surface and central waters, and were moderately affected by the Cape Verde Front located in the southeastern part of the domain. Thus, the front conditioned the meridional transports, acting as a barrier between North and South Atlantic Central waters. Specifically, −3.2±1.7 Sv entered through north and east and 6.7±1.7 Sv left through west and south transects. At intermediate levels, the most important source came from the south with −2.2±1.5 Sv of modified Antarctic Intermediate water, moderately affected by the circulation pattern above. The transports of O2 and inorganic nutrients conditioned by their distributions behaved quite similar to mass transports. The most intense and important transports of O2 and inorganic nutrients occurred in the deepest layer of central waters and in the shallowest two layers of intermediate waters where inorganic nutrients accumulated and large differences in concentrations of O2 were found, especially in the deepest layer of central waters between the northeast and southeast zones. In these three layers, transports of O2 and inorganic nutrients came from the east and south and they left northward and westward. This circulation pattern delivers inorganic nutrient from east and south to oligotrophic waters of north and west of CVFZ. Nevertheless, it can also hinders the ventilation of the deepest layer of central waters and the shallowest two layers of intermediate waters.