The South Atlantic Ocean separates South America and Africa. This vast ocean basin influences global climate patterns and hosts diverse marine life. Its immense size and deep waters make it a dynamic part of the world ocean system.
Geographic Scope
The South Atlantic Ocean extends south from the equator, dividing the eastern coast of South America from the western coast of Africa. Its southern boundary is the 60° South parallel, where it meets the Southern Ocean. The eastern limit runs south from Cape Agulhas, Africa, along the 20° East meridian, while the western limit is Cape Horn. This ocean basin spans approximately 40,270,000 square kilometers, making it the second largest ocean.
The South Atlantic is deeper and holds a greater volume of water than its northern counterpart. Its seabed features various depths, including the Romanche Trench, which reaches 7,758 meters and is one of the deepest points in the Atlantic. Several islands and archipelagos emerge, such as Tristan da Cunha, Ascension Island, Saint Helena, Gough Island, and the Brazilian islands of Fernando de Noronha and Rocas Atoll. The continental shelf along the South American coast varies in width, being wider near the Amazon and southern Argentina, and narrower along parts of the eastern Brazilian coast.
Oceanographic Dynamics
The South Atlantic Ocean is characterized by a prominent counterclockwise central subtropical gyre, influencing its major current systems. The Brazil Current, a warm, southward-flowing current, forms the western limb of this gyre along the eastern coast of South America. It transports warm, tropical waters, moderating coastal temperatures and contributing to increased humidity and rainfall in adjacent land areas. It has warm temperatures (19 to 27°C) and high salinity (35 to 37 parts per thousand).
As the Brazil Current flows southward, it converges with the cold, northward-flowing Falkland (Malvinas) Current near the Argentine Sea, forming the Brazil-Falkland Confluence. This interaction creates mixed water temperatures and generates nutrient-rich waters that support diverse marine ecosystems. On the eastern side, the cold Benguela Current flows northward along the western coast of southern Africa. Driven by southeasterly trade winds, the Benguela Current induces coastal upwelling, bringing cold, nutrient-rich waters to the surface. This upwelling influences arid conditions along the African coast and contributes to global thermohaline circulation.
Marine Ecosystems
The South Atlantic Ocean harbors a wide array of marine life and ecosystems, from coastal zones to the open ocean and deep-sea environments. Coastal habitats include sandy beaches, mangrove forests, rocky shores, and coral reefs, particularly along the Brazilian coast. Microscopic plankton forms the foundation of these diverse ecosystems, thriving in nutrient-rich areas and supporting a complex food web.
The rich waters sustain numerous fish species, including commercially important hake, pilchard, anchovy, and squid. Marine mammals like southern right whales, humpback whales, seals, dolphins, and penguins are abundant. Sea turtles (leatherback, green, loggerhead) utilize beaches for nesting, and seabirds such as albatrosses are observed. Productive biodiversity hotspots include the Benguela Upwelling System, the Patagonian Shelf, and Brazil’s Abrolhos Bank, influenced by oceanographic processes and freshwater discharge from major rivers.
Submarine Geology
The South Atlantic Ocean seabed is shaped by dynamic geological processes, dominated by the Mid-Atlantic Ridge (MAR). This extensive underwater mountain range is a divergent tectonic plate boundary, where the South American and African plates are moving apart. The MAR extends northward from approximately 58° South, exhibiting a rift valley at its crest that marks active seafloor spreading.
Seafloor spreading occurs at a relatively slow rate, about 2.5 centimeters per year. As the plates separate, magma from the Earth’s mantle rises to the seafloor, forming new oceanic crust. This process has gradually widened the ocean basin since the Triassic period. Beyond the central ridge, the ocean floor features vast abyssal plains, isolated seamounts, and deep trenches, with transverse ridges segmenting the MAR and creating distinct basins.
Human Significance
The South Atlantic Ocean holds considerable importance for human societies, serving as a corridor for global shipping and trade. Major maritime routes connect South American and African ports with Europe and North America, facilitating the transport of diverse goods. This oceanic connection has been historically significant for exploration and commerce.
Fishing industries rely on the South Atlantic’s productive waters, particularly in nutrient-rich upwelling zones like the Benguela Current system and the Brazil-Falkland Confluence. Key commercial species are harvested, supporting economies in coastal nations. The ocean also contains natural resources, with petroleum exploration and extraction occurring in various areas. However, human activities, including overfishing, pollution, and climate change, present challenges to the basin’s health and sustainability.