Atlantic Ocean

The Atlantic Ocean is the second largest of the world's five oceanic divisions, covering about 85 million square kilometers. It makes up around 17% of Earth's surface and about 24% of its water area. This vast body of water separates the New World of the Americas, including North America and South America, from the Old World of Afro-Eurasia, which includes Africa, Asia, and Europe.

Because of its position between these major landmasses, the Atlantic Ocean has been very important in human history. During the Age of Discovery, crossings of the Atlantic led to new connections between continents. The expedition of Christopher Columbus in 1492 was especially significant, beginning an age of exploration and later the colonization of the Americas by European powers such as Portugal, Spain, France, and the United Kingdom.

The Atlantic Ocean’s climate changes from place to place. The South Atlantic stays warm all year because it touches tropical lands, while the North Atlantic has milder temperatures with noticeable seasons. As part of the connected World Ocean, the Atlantic links to the Arctic Ocean to the north, the Pacific Ocean to the southwest, the Indian Ocean to the southeast, and the Southern Ocean to the south. Some definitions say it reaches all the way to Antarctica. The ocean is split into northern and southern parts by the Equator.

Names

The name "Atlantic" comes from ancient times. Around 450 BC, the writer Herodotus called it the "Sea of Atlas," referring to the sea near the Strait of Gibraltar and the Atlas Mountains. People in ancient Greece thought the Atlantic was part of a huge sea called the Oceanus, which they believed surrounded all land.

During the Age of Discovery, the Atlantic was also called the Great Western Ocean by English mapmakers. Today, some people, especially in Britain and America, call the northern Atlantic "the pond," a friendly way to talk about the ocean that connects their countries.

Extent and data

The International Hydrographic Organization has defined the limits of the Atlantic Ocean, though some countries have different ideas about these borders. The Atlantic is bounded on the west by North America and South America. To the east, it is bordered by Europe and Africa. It connects to the Arctic Ocean through several seas and straits, including the Labrador Sea, Denmark Strait, and Norwegian Sea.

In the southeast, the Atlantic meets the Indian Ocean. It also has many bays, gulfs, and seas along its coasts, such as the Caribbean Sea, Gulf of Mexico, and Mediterranean Sea. Including these smaller seas, the Atlantic covers a large area of the Earth's surface.

Bathymetry

The bathymetry of the Atlantic Ocean is shaped by a huge underwater mountain range called the Mid-Atlantic Ridge. This ridge stretches from near the North Pole to close to Bouvet Island, dividing the ocean into two parts. It rises over two kilometers above the ocean floor and creates valleys and volcanoes, including those in Iceland.

The ocean floor has wide areas called continental shelves near Newfoundland, southern South America, and north-eastern Europe. Deep trenches, like the Puerto Rico Trench, mark places where the floor drops very deep. The deepest part of the Atlantic reaches more than eight thousand meters below the surface.

Water characteristics

Surface water temperatures in the Atlantic Ocean vary from below −2 °C (28 °F) to over 30 °C (86 °F), depending on location and season. Warmer temperatures are found north of the equator, while colder temperatures occur in polar regions. In the middle latitudes, temperatures can change by about 7–8 °C (13–14 °F).

From October to June, the surface of the Labrador Sea, Denmark Strait, and Baltic Sea is often covered with sea ice. The Coriolis effect causes North Atlantic water to circulate clockwise, while South Atlantic water moves counter-clockwise. The Atlantic also experiences tides, with two high tides occurring every 24 lunar hours. In areas north of 40° North, there is an east–west movement of air and water known as the North Atlantic oscillation.

The Atlantic is the saltiest of the world's major oceans, with surface water salinity ranging from 33 to 37 parts per thousand (3.3–3.7%) by mass. Salinity is influenced by evaporation, precipitation, river inflow, and sea ice melting. The lowest salinity is found near the equator due to heavy rainfall, while the highest salinity occurs around 25° north and south, where there is little rain and high evaporation.

The Atlantic Ocean has four main types of upper water masses, each with different temperature and salinity. These water masses flow and mix, influencing the ocean's overall characteristics. The North Atlantic deep water is formed in the northern parts of the ocean and plays a role in the global climate by transporting warm water northward. The Atlantic's currents, such as the warm-water North Atlantic Gyre and South Atlantic Gyre, help move heat around the planet.

The Gulf Stream is a major current that flows northeast from the North American coast, bringing warm water to the North Atlantic. This warm water helps keep temperatures in Europe milder than they would otherwise be. The North Atlantic Subpolar Gyre, located north of the North Atlantic Gyre, is important for climate variability and is influenced by ocean currents and regional features.

The Sargasso Sea, located in the western North Atlantic, is encircled by the Gulf Stream, North Atlantic Drift, and North Equatorial Current. It is known for its floating seaweed, Sargassum, which provides a habitat for various marine life, including the sargassum fish. The Sargasso Sea is also the spawning ground for both European eels and American eels, which travel thousands of kilometers to reach their adult habitats in North America, Europe, and northern Africa.

Climate

The climate of the Atlantic Ocean is shaped by the temperatures of its surface waters, water currents, and winds. Because the ocean can store and release a lot of heat, areas near it have milder climates with smaller changes between seasons compared to areas far inland. The ocean provides much of the moisture in the air through evaporation, and its currents move warm and cold water to different parts of the world, affecting nearby lands.

The Gulf Stream and the North Atlantic Drift help keep temperatures milder in places like southeastern North America and northwestern Europe. However, cold currents can create fog near eastern Canada and northwestern Africa. Every winter, the Icelandic Low brings storms, and icebergs can be found near the Grand Banks of Newfoundland. Hurricanes sometimes occur in the western North Atlantic during summer and autumn.

Geology and plate tectonics

The Atlantic Ocean sits on dense rock made of materials like basalt and gabbro. Near the edges, where it meets the land, the ocean floor is covered with fine clay, silt, and other small particles. The oldest parts of the ocean floor in the Atlantic are found far from the shorelines, near Africa and North America, and are about 145 million years old.

The Atlantic Ocean formed when the huge ancient landmass called Pangaea broke apart. This happened mainly in the central part of the ocean, between what is now North America and Africa. As the continents moved apart, new ocean floor formed in between them. This process also created many volcanoes and lava flows, leaving behind layers of rock that we can still see today.

Future of the Atlantic

Scientists are studying how the Atlantic Ocean might change in the very distant future. One idea is that a new subduction system, where one part of Earth’s crust moves under another, could form near the Gibraltar Arc. This might eventually lead to the Atlantic Ocean closing up.

Another theory suggests that instead, the Atlantic might keep getting wider while the Pacific Ocean closes first. If this happens, the continents could come together to form a new supercontinent called Amasia in about 200 to 300 million years.

History

Main category: History of the Atlantic Ocean

The Atlantic Ocean has a long and rich history, shaped by human movements and discoveries over thousands of years. Early humans spread from Africa into Europe, Asia, and Australia, leaving traces along Atlantic coasts. As they settled, they developed new ways to use marine resources, creating large piles of shells called shell middens. These show how people lived and used the ocean long ago.

Later, during a cold period called the Last Glacial Maximum, ice covered much of North America, and people lived in places like Beringia, connecting Siberia to Alaska. When the ice melted, people moved south. The Norse Vikings were among the first Europeans to reach places like the Faroe Islands, Iceland, and Greenland, though these settlements faced many challenges.

The Atlantic Ocean also played a big role during the Age of Discovery. Explorers like Christopher Columbus reached the Americas in 1492, and Vasco da Gama found a sea route to India around Africa. These voyages led to European colonization of the Americas, which brought big changes to the world, including new trade routes and the movement of many people across the ocean.

Economy

The Atlantic Ocean plays a big role in the economies of countries around it. It helps with transportation and communication between continents. The ocean also holds many natural resources, like fish and oil, which people use every day.

Fisheries are very important along the Atlantic coasts. Areas like the Grand Banks of Newfoundland and the waters near Iceland are rich in fish. Over time, some fish populations have gone down because people have caught too many fish. Scientists and governments work together to help fish populations recover. Today, many people depend on these fisheries for food and jobs.

Environmental issues

The Atlantic Ocean faces several environmental challenges that affect its wildlife and ecosystems. Many marine species, such as manatees, seals, sea lions, turtles, and whales, are endangered. Fishing practices like drift net fishing can harm dolphins, albatrosses, and other seabirds, which also speeds up the decline of fish populations.

Pollution is another major issue. Rivers carry agricultural fertilizer chemicals, livestock waste, and human waste into the ocean, creating areas with very low oxygen levels called hypoxia and dead zones. Human-made waste, known as marine debris or marine litter, often collects in ocean areas called gyres and can wash up on beaches. One well-known area of pollution is the North Atlantic garbage patch, which spans hundreds of kilometers.

Climate change also impacts the Atlantic Ocean. Rising sea surface temperatures can lead to more frequent and intense hurricanes. The ocean absorbs a lot of heat, which causes the water to expand and contributes to sea level rise. Over time, melting ice, such as from the Greenland ice sheet, is expected to raise sea levels even more.