The Atlantic Ocean covers approximately 106.46 million square kilometers, representing about 23.5% of the world’s total ocean surface area. It plays a significant role in Earth’s systems, influencing climate, supporting diverse life, and connecting continents.
Unique Properties of Atlantic Water
Atlantic water has distinct physical and chemical characteristics. Its average salinity is around 35.4 to 36.01 parts per thousand, higher than other oceans. Salinity varies geographically, being lowest in equatorial and polar regions and highest in subtropical latitudes, reaching over 37 parts per thousand in the North Atlantic.
Ocean temperatures in the Atlantic vary widely from the surface to the deep and from tropical to polar regions. Surface waters in the tropics can exceed 30°C, while near the poles, temperatures can drop to about -2°C. Below 200 meters, the deep ocean is consistently cold, with temperatures ranging from 0-3°C.
The interplay of temperature and salinity determines water density, a fundamental property influencing ocean circulation. The average depth of the Atlantic Ocean is about 3,646 meters, with the deepest point being the Puerto Rico Trench at approximately 8,380 meters. This depth impacts pressure and the penetration of sunlight, shaping the habitats within.
The Atlantic’s Role in Global Currents
Atlantic water is an integral part of the global ocean circulation system. Major surface currents, such as the Gulf Stream and the North Atlantic Current, transport warm water from the tropics towards higher latitudes. The Gulf Stream flows along the eastern coast of North America before extending across the Atlantic, moderating the climate of Western Europe and the eastern United States, leading to milder winter temperatures in Western Europe.
The Atlantic Meridional Overturning Circulation (AMOC) is a large-scale system that acts as a “conveyor belt” for heat and nutrients. It transports warm, salty surface waters poleward from the tropics. As these waters cool and become denser in the North Atlantic, they sink to deeper layers. This cold, dense water then flows equatorward along the ocean floor, eventually resurfacing to complete the cycle. The AMOC plays a significant role in redistributing heat globally and transporting dissolved oxygen, carbon, and other nutrients, which supports marine ecosystems and acts as a carbon sink.
Life Within the Atlantic
The Atlantic Ocean supports a vast array of marine life across diverse ecosystems. Productive continental shelf areas, such as the U.S. Northeast Shelf and South Atlantic, are home to commercially important fish species. The Sargasso Sea, a region in the North Atlantic, is characterized by free-floating Sargassum seaweed that provides shelter and nursery grounds for many species, including the Sargassum fish and juvenile sea turtles.
Deep-sea environments, including hydrothermal vents and cold-water coral reefs, also flourish in the Atlantic. Cold-water coral reefs, unlike their tropical counterparts, do not rely on sunlight and can be found at depths between 200 and 2,000 meters. Species like Lophelia pertusa form complex structures that provide habitat for over 1,300 associated species, including sponges, worms, and deep-sea fish. The Atlantic is also a habitat for migratory species such as bluefin tuna, which undertake extensive trans-Atlantic migrations, and leatherback sea turtles, which travel thousands of kilometers annually between tropical nesting beaches and colder foraging grounds.
Changing Atlantic Water
Atlantic water is currently experiencing significant environmental changes, largely driven by rising global temperatures. Ocean warming is a major concern, as the Atlantic Ocean, particularly the upper layers, is absorbing a substantial amount of excess heat from the atmosphere. This warming leads to thermal expansion of seawater, contributing to rising sea levels, which threaten coastal communities and ecosystems. Warmer waters also cause marine species to shift their geographic distributions, impacting food webs and fishing patterns as species shift their ranges.
Ocean acidification, another issue, occurs as the ocean absorbs excess carbon dioxide from the atmosphere. This absorption changes seawater chemistry, reducing pH levels and making the water more acidic. Ocean acidification particularly affects marine organisms that build shells or skeletons from calcium carbonate, such as corals, oysters, clams, and pteropods, making it difficult for them to grow and maintain their structures. This can have ripple effects throughout the food chain and impact important ecosystems like coral reefs.
Pollution, including plastic accumulation and chemical runoff, further impacts Atlantic water quality and ecosystems. Over 8 million metric tons of plastic waste enter oceans annually, with the Atlantic estimated to hold significantly more plastic pollution than previously believed. This plastic debris, along with chemical additives and absorbed pollutants, poses physical and chemical threats to marine life through ingestion and entanglement, disrupting food chains and affecting species from microscopic plankton to large mammals.