What Is the Atlantic Ocean?

The Atlantic Ocean is the second largest of Earth's ocean basins, covering roughly 106 million square kilometers, about a fifth of the planet's surface, in an elongated S-shaped trough between the Americas to the west and Europe and Africa to the east. It connects to the Arctic Ocean through the Greenland and Norwegian seas, to the Pacific through the Drake Passage, and to the Indian Ocean south of Africa, and its major marginal seas include the Caribbean, the Gulf of Mexico, the Mediterranean, the North Sea, and the Baltic. Mean depth is close to 3,600 meters, with the deepest point in the Puerto Rico Trench at roughly 8,400 meters. For geoscience and ocean engineering the basin is significant less for its size than for the disproportionate role it plays in global heat transport.

Basin Structure and Seafloor Geology

The dominant seafloor feature is the Mid-Atlantic Ridge, a divergent plate boundary running the length of the basin from the Arctic to the Southern Ocean. New oceanic crust forms there at a slow spreading rate of a few centimeters per year, and the resulting symmetric magnetic anomaly stripes on either side of the ridge axis supplied some of the earliest quantitative evidence for seafloor spreading and plate tectonics. Hydrothermal vent fields along the ridge, including Lucky Strike and the Trans-Atlantic Geotraverse site, host chemosynthetic ecosystems and metal sulfide deposits. Away from the ridge the basin has broad continental margins, extensive abyssal plains built by turbidity currents, and salt tectonic provinces off Brazil and West Africa that host major hydrocarbon reservoirs.

Circulation and the Meridional Overturning

The Atlantic is the only ocean basin with a fully developed pole-to-pole overturning cell. Warm, salty surface water moves northward in the Gulf Stream and the North Atlantic Current, loses heat to the atmosphere at high latitudes, becomes dense enough to sink in the Labrador and Nordic seas, and returns southward at depth as North Atlantic Deep Water. This circulation, described by the National Oceanography Centre's account of the Atlantic Meridional Overturning Circulation, carries on the order of a petawatt of heat northward and is the reason northwestern Europe is far milder than its latitude would suggest. Wind-driven subtropical and subpolar gyres, the equatorial current system, and Mediterranean outflow set the upper-ocean structure superimposed on this overturning.

Observation and Remote Sensing

Sustained measurement of the Atlantic combines moored arrays, autonomous platforms, and satellites. The RAPID-MOCHA-WBTS mooring line at 26 degrees north spans the basin from Florida to Morocco and has produced a continuous record of overturning transport since 2004; the NOAA Atlantic Oceanographic and Meteorological Laboratory account of that record describes how it revealed variability on daily to decadal timescales that earlier theory did not anticipate. Complementary arrays operate at other latitudes, and the RAPID program documents the instrument design and data products. Argo profiling floats supply temperature and salinity to two thousand meters, satellite altimetry and scatterometry provide sea surface height and wind stress, and multibeam echo sounding underpins bathymetric charting. A synthesis of observed AMOC transport and variability compares the estimates these systems produce.

Applications

Study of the Atlantic Ocean supports work in a range of fields, including:

• Climate modeling and long-range prediction, where overturning strength is a key uncertainty
• Hurricane forecasting, which depends on tropical Atlantic sea surface temperature and shear
• Submarine telecommunications cable routing and repair
• Offshore energy, including deepwater hydrocarbons and floating wind
• Marine navigation, search and rescue, and operational oceanography
• Fisheries management and marine ecosystem monitoring
• Underwater acoustics and autonomous vehicle operations