The central Atlantic Ocean is the stretch of water between the eastern seaboard of the Americas and the western coast of Africa, roughly spanning from the tropics to the mid-latitudes. It sits atop one of the youngest ocean floors on Earth, a basin that only began forming when the supercontinent Pangaea split apart around 200 million years ago. That origin story set the stage for nearly everything interesting about the region today, from the volcanic ridge that still runs down its center to the currents that steer hurricanes, the dust plumes that fertilize its surface waters, and the deep-sea ecosystems that thrive on chemical energy where sunlight never reaches.
How the Central Atlantic Was Born
The central Atlantic did not exist before the breakup of Pangaea. Around 230 million years ago, during the late Triassic, the landmass that would become North America was pressed directly against what is now northwest Africa. Rifting began along the eastern margin of North America and the northwest African margin, stretching and thinning the continental crust over tens of millions of years. By about 200 million years ago, the rift had progressed to the point where true oceanic crust started forming between the two separating continents.1Geophysical Journal International. Breakup of Pangaea and plate kinematics of the central Atlantic and Atlas regions The process was not a clean, symmetric split. A small Moroccan microplate formed at the boundary between the two great landmasses of Gondwana and Laurasia, complicating the picture. A second phase of spreading, lasting until roughly 185 million years ago, produced new ocean floor while the Atlas mountain chain in North Africa continued to rift. A third phase then extended the spreading system further north, linking the central Atlantic to the ancient Tethys Ocean.
Patterns in the volcanic crust and seismic data along the margins suggest that while the initial rifting was roughly symmetric, the actual creation of new ocean floor became lopsided. On the Canadian side, the lithosphere was pulled apart largely by faulting, while on the Moroccan side, fresh magmatic crust formed alongside pockets of serpentinite, a mineral created when seawater reacts with mantle rock.2Tectonics. Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup That asymmetry left a lasting imprint on the shape and structure of the ocean basin.
The Volcanic Province That Helped Trigger a Mass Extinction
Right around the time the central Atlantic began to open, one of the largest volcanic events in Earth’s history was underway. The Central Atlantic Magmatic Province, or CAMP, erupted enormous volumes of lava across what are now four continents. Its remnants can be found in eastern North America, western Africa, southwestern Europe, and northern South America. The eruptions coincided almost exactly with the end-Triassic mass extinction, roughly 201 million years ago, which wiped out a large share of life on land and in the sea and cleared ecological space for the dinosaurs to dominate.
The killing mechanism was not just lava covering the landscape. When magma intruded into sedimentary rocks as horizontal sheets called sills, the heat baked surrounding organic-rich sediments and released massive quantities of carbon into the atmosphere. Isotopic data from sediments deposited at the time show large negative swings in carbon isotope ratios, a fingerprint of light carbon flooding the ocean-atmosphere system. Research has concluded that the thermogenic carbon generated from the contact zones around these sills is a credible source for those carbon cycle disturbances.3PubMed Central. Thermogenic carbon release from the Central Atlantic magmatic province caused major end-Triassic carbon cycle perturbations In other words, the volcanism destabilized Earth’s climate not just by erupting gas directly but by cooking carbon out of buried organic matter, a process with uncomfortable parallels to modern fossil fuel combustion.
The Mid-Atlantic Ridge and What Lives on It
Running roughly north to south through the center of the Atlantic is the Mid-Atlantic Ridge, a submarine mountain chain where tectonic plates are still pulling apart and new ocean floor is being created. In the central Atlantic, the ridge rises several kilometers above the abyssal plain, occasionally breaking the surface as islands like the Azores and Ascension Island. The spreading rate here is slow compared to the Pacific, typically a few centimeters per year, and that slow pace has consequences for the geology and biology of the ridge.
One consequence is the exposure of mantle rock, called peridotite, at and near the seafloor. When seawater seeps into this rock, it drives a chemical reaction called serpentinization, which transforms the minerals, releases heat, and produces hydrogen gas. The Lost City hydrothermal field, located on the flanks of the Mid-Atlantic Ridge near 30°N, runs entirely on this process rather than on the volcanic heat that powers the more famous “black smoker” vents. Isotopic dating shows that Lost City has been active for at least 30,000 years, and the underlying serpentinization process could sustain such a system for hundreds of thousands or even millions of years.4PubMed. 30,000 years of hydrothermal activity at the lost city vent field The fluids venting at Lost City are highly alkaline, with temperatures around 250°C at depth in the subsurface reaction zone, and they build towering white carbonate chimneys rather than the dark sulfide structures found at volcanic vents.5Geochimica et Cosmochimica Acta. Chemical and isotopic constraints on water/rock interactions at the Lost City hydrothermal field, 30°N Mid-Atlantic Ridge
The ecosystems on the Mid-Atlantic Ridge’s hydrothermal vents are built on chemosynthesis rather than photosynthesis. Microbes at vent sites along the ridge fix carbon using energy from oxidizing sulfides and other reduced chemicals in the vent fluid.6Journal of Geophysical Research: Solid Earth. Chemosynthetic microbial activity at Mid‐Atlantic Ridge hydrothermal vent sites Dense swarms of eyeless shrimp, particularly the species Rimicaris exoculata, cluster near warm water emissions, feeding on bacteria that grow as filaments on their own bodies and as mats on the mineral deposits. The fauna at Atlantic vents is largely made up of invertebrate types also found in other chemosynthetic environments, though often as distinct species or genera.7Geological Society, London, Special Publications. Ecology of Mid-Atlantic Ridge hydrothermal vents
Away from the vents, the ridge’s contribution to overall biodiversity is less dramatic than you might expect. A study of soft-sediment fauna along the Mid-Atlantic Ridge found that the communities there are composed mainly of species already known from continental margins, with no evidence that the ridge itself enhances biodiversity.8PubMed Central. Does presence of a mid-ocean ridge enhance biomass and biodiversity? Surveys of the tropical portion of the ridge have documented diverse but small-bodied communities, with hermit crabs and brittle stars among the most common animals at depths between roughly 2,300 and 3,900 meters.9Deep Sea Research Part II: Topical Studies in Oceanography. First data on benthic and fish communities from the Mid-Atlantic Ridge, 16°40′− 17°14′N
Currents, Heat Transport, and the Equatorial Cold Tongue
The central Atlantic is a critical corridor for the global movement of heat. The Atlantic as a whole is unusual among ocean basins in transporting heat northward in both hemispheres. At 26°N, the northward ocean heat transport is estimated at roughly 1.0 to 1.2 petawatts, depending on the resolution of the ocean model used, with higher-resolution models that capture ocean eddies producing values closer to what instruments in the water actually measure.10Journal of Geophysical Research: Oceans. Increasing Atlantic Ocean Heat Transport in the Latest Generation Coupled Ocean‐Atmosphere Models: The Role of Air‐Sea Interaction This heat delivery to the North Atlantic helps keep Western Europe significantly warmer than other regions at the same latitude.
Near the equator, the central Atlantic has its own distinctive circulation. The Equatorial Undercurrent, a ribbon of water flowing eastward beneath the surface, supplies the upwelling that brings cold, nutrient-rich water to the surface in the eastern equatorial Atlantic. Estimated transport of this undercurrent is about 20 Sv (a unit equal to a million cubic meters per second) at 35°W and about 14 Sv at 23°W.11Journal of Geophysical Research: Oceans. Atlantic Equatorial Undercurrent and associated cold tongue variability The upwelling in the western equatorial Atlantic is driven mainly by wind-driven surface water being pushed away from the equator, while in the east it is dominated by the rise and fall of the thermocline associated with equatorial ocean waves.12Geophysical Research Letters. Dynamics of upwelling annual cycle in the equatorial Atlantic Ocean The result is the Atlantic cold tongue, a patch of anomalously cool surface water that appears seasonally in the eastern equatorial Atlantic and profoundly influences rainfall patterns on the surrounding continents.
Variability in the cold tongue and in tropical Atlantic sea surface temperatures more broadly has far-reaching effects on climate. Changes in equatorial Atlantic temperatures influence rainfall over the Gulf of Guinea and northeastern South America.13WIREs Climate Change. Equatorial Atlantic variability—Modes, mechanisms, and global teleconnections The dynamic is sometimes compared to El Niño in the Pacific but operates on different timescales and with somewhat different mechanics.
Saharan Dust and Sea Surface Temperatures
Every year, hundreds of millions of tons of mineral dust blow off the Sahara Desert and out over the central Atlantic. This dust is not just a visual curiosity visible in satellite images. It actively shapes the ocean’s temperature, its nutrient chemistry, and even the behavior of hurricanes.
The most direct effect is on surface solar radiation. Dust absorbs and scatters sunlight, reducing the energy reaching the ocean surface. Modeling studies have found that Saharan dust reduces surface downward radiation over the ocean by as much as 20 to 30 watts per square meter beneath heavy plumes.14PubMed Central. Impacts of Saharan Mineral Dust on Air-Sea Interaction over North Atlantic Ocean Using a Fully Coupled Regional Model The dust cools sea surface temperatures near the West African coast, but the response is not uniform. In the western tropical Atlantic, dust can paradoxically warm sea surface temperatures through changes in atmospheric circulation. The dust plume creates a low-pressure anomaly and cyclonic wind pattern that alters ocean mixing, and the resulting temperature changes differ depending on location relative to the plume.15PubMed Central. Impacts of Saharan Mineral Dust on Air-Sea Interaction over North Atlantic Ocean Using a Fully Coupled Regional Model
Looking at broader patterns, Saharan dust accounts for roughly 30 to 40 percent of the observed change in Atlantic sea surface temperatures during the early hurricane season, with more dust associated with cooler water and less dust with warmer water.16Geophysical Research Letters. Cooling of the Atlantic by Saharan dust General circulation models confirm this pattern: dust cools the land surface and eastern Atlantic through its shortwave absorption while producing warming in the western Atlantic and Caribbean through changes in surface energy fluxes and atmospheric circulation.17Annales Geophysicae. A GCM study of the response of the atmospheric water cycle of West Africa and the Atlantic to Saharan dust radiative forcing
Why Sea Surface Temperatures Matter for Hurricanes
The central Atlantic’s main development region for hurricanes runs roughly from 10°N to 20°N and from 20°W to 80°W. Warm sea surface temperatures in this zone provide the energy that fuels tropical cyclones, and positive temperature anomalies in the region are a precursor to active hurricane seasons.18Nature Communications. Ocean precursors to the extreme Atlantic 2017 hurricane season The connection has a surprisingly long memory. Unusually warm wintertime temperatures in the main development region can persist into the following summer, explaining roughly 42 percent of the variance in hurricane-season sea surface temperatures over several decades of records.19Geophysical Research Letters. Persistent influence of tropical North Atlantic wintertime sea surface temperature on the subsequent Atlantic hurricane season In practice, this means that conditions set months before the first storm forms help determine how active the season will be.
The Saharan dust connection comes into play here too. Because heavy dust years cool the ocean surface in the development region, they tend to suppress hurricane activity. Low-dust years leave the ocean warmer and more favorable for storm formation. Forecasters track Saharan dust plumes as one input among several when estimating seasonal hurricane risk.
Dust as Ocean Fertilizer
Beyond its effects on temperature and hurricanes, Saharan dust delivers nutrients to the open ocean. Mineral dust carries iron, nitrogen, and phosphorus, all of which are needed by the microscopic plants (phytoplankton) at the base of the marine food web. In the nutrient-poor waters of the central and western tropical Atlantic, atmospheric deposition is a relatively large source of these nutrients compared to what upwelling or river runoff can supply.20Global Biogeochemical Cycles. Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados
The fertilization story is not as simple as “more dust, more life,” though. Experiments off Barbados showed that Saharan dust delivers nitrogen and iron in far greater proportion than phosphorus, and the phosphorus it does carry dissolves poorly in seawater. The result is that dust deposition can actually push the ecosystem into phosphorus limitation, favoring certain phytoplankton like Prochlorococcus that have evolved extremely efficient phosphorus uptake and low phosphorus requirements.21Global Biogeochemical Cycles. Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados So the dust shifts the community composition in subtle ways rather than simply boosting overall productivity. Wet deposition, when rain washes dust particles out of the atmosphere and into the ocean, may enhance the release and bioavailability of dust-derived nutrients compared to dry fallout.22Geophysical Research Letters. Tropical Rains Controlling Deposition of Saharan Dust Across the North Atlantic Ocean
The Sargasso Sea and the Great Atlantic Sargassum Belt
The central Atlantic is home to a phenomenon found nowhere else on Earth: enormous floating mats of Sargassum, a brown seaweed that lives its entire life cycle on the ocean surface. Historically, the Sargasso Sea in the western central Atlantic was known as the primary home of this seaweed. Since 2011, however, satellite data have revealed a massive new accumulation zone stretching from West Africa to the Caribbean and the Gulf of Mexico, now called the Great Atlantic Sargassum Belt.
The bloom’s distribution is shaped mostly by ocean circulation. Research points to nutrient inputs from the Amazon River during spring and summer, and from upwelling off West Africa during boreal winter, as the primary drivers. The initial 2011 bloom may have been seeded by high Amazon discharge in prior years, but the recurrence and growth of the belt since then suggest a possible regime shift, raising the prospect that massive tropical Atlantic Sargassum blooms could become a regular occurrence.23PubMed. The great Atlantic Sargassum belt For Caribbean and West African coastal communities, these blooms mean rotting seaweed on beaches, fouled fishing gear, and threats to coral reefs and sea turtle nesting habitat.
Wildlife Corridors and Fisheries
The central Atlantic functions as a vast highway for migratory species. Sea turtles hatching on South American beaches make remarkable trans-equatorial journeys through the central Atlantic. Satellite tracking of juvenile green turtles released from breeding beaches in the South Atlantic showed that all turtles released at the end of the hatching season moved quickly northward along the continental shelf, crossing the equator within a few weeks and traveling as far as 13°N, just east of Barbados.24PubMed Central. First satellite tracks of South Atlantic sea turtle ‘lost years’: seasonal variation in trans-equatorial movement These journeys through the central Atlantic’s current systems represent the poorly understood “lost years” of juvenile sea turtle life history.
The equatorial central Atlantic also supports commercially valuable fisheries, particularly for yellowfin tuna. Catch data show that the highest concentrations of yellowfin tuna in the region are strongly associated with the position and seasonal movement of the Intertropical Convergence Zone, the atmospheric belt where trade winds from the northern and southern hemispheres meet. The most productive fishing period runs from roughly March to May, with about 5°S marking the southern limit for large concentrations during that window.25Remote Sensing of Environment. Remote sensing data and longline catches of yellowfin tuna (Thunnus albacares) in the equatorial Atlantic In the open ocean, mesoscale eddies, swirling bodies of water tens to hundreds of kilometers across, play a role in pumping nutrients upward and sustaining the productivity that supports these fish populations.26Nature. Influence of mesoscale eddies on new production in the Sargasso Sea
An Ancient Ocean That Periodically Suffocated
The central Atlantic has not always been the well-oxygenated ocean we know today. During the Cretaceous period, roughly 145 to 66 million years ago, when the Atlantic was younger and narrower, repeated episodes of widespread oxygen depletion struck the world’s oceans, including this basin. Known as oceanic anoxic events, these intervals produced the dark, carbon-rich sediments that now form some of the world’s petroleum source rocks. Three major time windows stand out: the late Barremian through Albian, the Cenomanian-Turonian boundary, and to a lesser degree the Coniacian-Santonian, each correlating with periods of sea level rise.27GeoScienceWorld (Journal of the Geological Society). Cretaceous anoxic events: from continents to oceans Organic matter from both marine plankton and terrestrial sources accumulated in the oxygen-starved waters and was eventually buried, locking away vast quantities of carbon.
During the Last Glacial Maximum, roughly 20,000 years ago, the central Atlantic looked very different from today. Modeling of water masses at that time shows that the upper ocean in the North Atlantic was 2 to 3°C colder than the present, while the South Atlantic was 4 to 5°C colder in some estimates.28Paleoceanography. Modeling the water masses of the Atlantic Ocean at the Last Glacial Maximum The circulation patterns that drive modern heat transport were substantially weaker, with consequences for climate across the surrounding continents.