South Atlantic Ocean conveyor

South Atlantic Ocean conveyor
Name	South Atlantic Ocean conveyor
Type	ocean current system
Location	South Atlantic Ocean
Status	active

South Atlantic Ocean conveyor The South Atlantic Ocean conveyor is a component of large-scale oceanic circulation linking the South Atlantic Ocean, Southern Ocean, and North Atlantic Ocean through wind-driven and density-driven flows. It connects boundary currents such as the Benguela Current, Brazil Current, and Malvinas Current with basin-scale overturning in the Atlantic Meridional Overturning Circulation and interacts with atmospheric systems like the South Atlantic Convergence Zone and the Intertropical Convergence Zone. Research on this conveyor integrates observations from programs including WOCE, Argo floats, and the Global Ocean Observing System alongside climate projections from the Coupled Model Intercomparison Project.

Overview

The conveyor comprises interlinked currents and density fronts that route heat, salt, and momentum between the Southern Ocean, the Equatorial Atlantic, and the North Atlantic Drift region via pathways such as the South Equatorial Current and the Antarctic Circumpolar Current. Surface branches influence coastal systems off Brazil, Argentina, and South Africa and modulate climate teleconnections with the Amazon Basin, the Patagonia region, and the Iberian Peninsula. Historical programs like IGBP and contemporary initiatives such as the Pacific Decadal Oscillation studies provide contextual frameworks for long-term variability detection.

Physical Mechanisms and Circulation Pathways

The conveyor integrates wind-driven gyres, boundary currents, and thermohaline processes. Western boundary currents—Brazil Current—transport warm, saline waters southward, while eastern boundary currents—Benguela Current—carry cooler waters northward influenced by upwelling near the Angola Current and Namibia shelf. Southward exchange across the equator involves the North Brazil Current retroflection and water mass transformation near the Equatorial Atlantic. Deep pathways connect to the Antarctic Intermediate Water and North Atlantic Deep Water formation zones via mixing in the Cape Basin and interactions with the Mid-Atlantic Ridge bathymetry. Wind stress from the South Atlantic Subtropical High and eddy fluxes generated near the Brazil–Malvinas Confluence shape mesoscale transport and cross-frontal exchange.

Role in Global Thermohaline Circulation

As a conduit between the Southern Ocean and the North Atlantic Ocean, the South Atlantic conveyor contributes to global heat redistribution and the maintenance of the Atlantic Meridional Overturning Circulation. It mediates the northward transport of heat associated with the Gulf Stream system and the southward return of cold deep waters, influencing climate regimes over Europe, West Africa, and South America. Variations in salinity and stratification linked to the conveyor affect formation rates of North Atlantic Deep Water and modification of Antarctic Intermediate Water, with implications for transient responses seen in paleo-records from sites like Benguela Upwelling cores and Saharan dust deposition.

Interaction with Climate Variability and Change

The conveyor responds to and modulates modes of climate variability including the El Niño–Southern Oscillation, the North Atlantic Oscillation, and multidecadal variability such as the Atlantic Multidecadal Variability. Anthropogenic forcing tied to the Paris Agreement-era emissions scenarios alters surface buoyancy through freshwater input from Amazon River, Patagonia meltwater, and changes in precipitation over the Sahel, modifying stratification and overturning strength. Model intercomparisons from CMIP6 indicate potential shifts in the conveyor's pathways and vigor under high-emission scenarios, with nonlinear feedbacks involving sea ice changes near Weddell Sea and altered wind stress in the Southern Hemisphere.

Biogeochemical and Ecological Impacts

By transporting nutrients, oxygen, and carbon, the conveyor influences primary productivity in regions such as the Benguela Upwelling System, the Brazil-Malvinas Confluence, and the Equatorial Atlantic. Changes in circulation modify hypoxia events along continental shelves of Namibia and Brazil and affect fisheries targeting species like anchoveta-analog populations and migratory pelagics exploited by fleets from Spain, Japan, and South Africa. The conveyor also mediates sequestration of anthropogenic carbon into the deep ocean, relevant to assessments by the Intergovernmental Panel on Climate Change and biogeochemical surveys from research vessels such as RRS Sir David Attenborough and RV Pelagia.

Observations and Modeling Studies

Empirical constraints derive from hydrographic sections, moored arrays at strategic locations like the Cape Basin and Río de la Plata mouth, satellite altimetry missions including TOPEX/Poseidon, Jason series, and profiling networks such as Argo. Numerical experiments using ocean general circulation models within coupled frameworks—examples include models from NOAA, UK Met Office, and ECMWF—explore sensitivity to freshwater anomalies, wind stress shifts, and mesoscale eddy parameterizations. Paleoclimate reconstructions using sediment cores, radiocarbon dating tied to IntCal chronologies, and isotope proxies from ODP sites complement modern observations.

Regional Human and Societal Implications

Variability of the conveyor affects regional climate hazards—droughts in the Northeast Brazil region, floods in the La Plata Basin, and shifts in marine resources critical to economies of Angola, Namibia, Brazil, and Argentina. Fisheries management under frameworks like the South Atlantic Fisheries Commission and coastal adaptation planning coordinated by entities such as the United Nations Environment Programme rely on improved projections of circulation-driven change. Infrastructure risks for ports in Cape Town, Montevideo, and Rio de Janeiro are influenced by sea-level anomalies and storm surge patterns modulated in part by conveyor variability.

Category:Ocean currents