The Atlantic Ocean is the world’s second-largest oceanic division, stretching across an S-shaped basin separating the Americas from Europe and Africa. Covering approximately 20% of Earth’s surface, its depth varies dramatically from shallow coastal shelves to deep-sea trenches. Determining the average depth provides a foundational figure for understanding the ocean’s total volume and topography.
Defining the Average Depth
The standard accepted average depth of the Atlantic Ocean, including its marginal seas, is approximately 3,646 meters (11,962 feet). This value represents the mean depth calculated by dividing the total volume of water by the total surface area of the basin. The calculation must account for every contour and feature of the Atlantic seafloor.
The average depth is derived through bathymetry, the scientific discipline of mapping the ocean floor. Modern measurements use advanced technologies to create detailed topographic maps of the seabed. Ships use multibeam sonar systems, which emit sound waves and measure the echo return time.
Another method involves satellite radar altimetry, which measures the height of the sea surface from space. Changes in sea surface height can indicate underwater features, such as the gravitational pull of a large underwater mountain causing the water surface above it to bulge slightly. By integrating these precise measurements, scientists calculate the Atlantic’s total volume.
Geographic Scope and Basins
Calculating the average depth requires a clear definition of the Atlantic’s geographic boundaries. The ocean extends from the Arctic Ocean in the north to the Southern Ocean at the 60° South latitude parallel. Its lateral boundaries are defined by the coastlines of the Americas to the west and Europe and Africa to the east.
For measurement purposes, the Atlantic is commonly divided into the North and South Atlantic basins, separated roughly by the Equatorial Counter Current. The topography of the ocean floor significantly influences the average depth. The most prominent feature is the Mid-Atlantic Ridge, a massive submarine mountain range running down the center of the ocean.
The ridge creates areas of shallower water, often less than 2,700 meters deep, where new crust is formed. Flanking the ridge are the abyssal plains, which are vast, flat regions lying at depths between 3,700 and 5,500 meters. The presence of the ridge elevates the overall seafloor, contributing to a shallower average depth.
The Deepest Points of the Atlantic
While the average depth is under 4,000 meters, the Atlantic Ocean contains certain areas that plunge far deeper. The single deepest point in the entire basin is the Milwaukee Deep, located within the Puerto Rico Trench in the western North Atlantic.
The Milwaukee Deep has been precisely measured at approximately 8,376 meters (27,480 feet), a figure confirmed by recent deep-sea expeditions. This location is situated about 120 kilometers north of Puerto Rico. The Puerto Rico Trench itself is a massive underwater chasm, extending over 1,750 kilometers, formed by the complex boundary between the North American and Caribbean tectonic plates.
Trenches are created where one tectonic plate slides beneath another, forming a deep, narrow depression on the seafloor. This maximum depth point is more than twice the overall Atlantic average. Such localized, extreme depths contribute to the total volume calculation but do not dramatically skew the final average depth because the deep trenches cover a relatively small area.