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The Ocean: A Detailed Overview

The ocean covers approximately 70.8% of the Earth and contains 97% of Earth's water.
The ocean is divided into five different areas: Pacific, Atlantic, Indian, Southern, and Arctic.
The ocean is the principal component of Earth's hydrosphere and influences climate, weather patterns, the carbon cycle, and the water cycle.
The photic zone includes water from the surface to a depth of 1% of the surface light, where photosynthesis can occur. This zone is the origin of the food supply for most of the ocean ecosystem and creates 50% of the oxygen in the Earth's atmosphere.
Ocean temperatures depend on the amount of solar radiation reaching the ocean surface and are influenced by ocean currents generated by forces acting upon the water, including temperature differences, atmospheric circulation (wind), the Coriolis effect, and differences in salinity.
The ocean water contains large quantities of dissolved gases, including oxygen, carbon dioxide, and nitrogen. The increasing concentration of carbon dioxide in the atmosphere leads to higher concentrations in ocean water, resulting in ocean acidification.
The ocean provides society with important environmental services, including climate regulation, trade and transport, and access to food and other resources. It is also the habitat of over 230,000 species.
The ocean is subject to numerous human-caused environmental threats, including marine pollution, overfishing, and effects of climate change on oceans, such as ocean warming, ocean acidification, and sea level rise.
The ocean is shaped irregularly, allowing the discernment of Earth's surface into a water and land hemisphere, as well as the division of the ocean into particular oceans.
The major oceanic divisions are Atlantic, Pacific, Indian, Southern, and Arctic. Oceans are fringed with coastlines that run for 360,000 kilometers in total distance.
Every ocean basin has a mid-ocean ridge, which creates a long mountain range beneath the ocean. Together they form the global mid-oceanic ridge system that features the longest mountain range in the world.
Ocean water represents the largest body of water within the global water cycle, and oceans have a significant effect on the biosphere. Oceanic evaporation, as a phase of the water cycle, is the source of most rainfall.
The motions of the ocean surface, known as undulations or wind waves, profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from sea sickness. Waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind.Overview of the Earth's Oceans
The ocean's surface plays a crucial role in oceanic and atmospheric processes, allowing for the interchange of particles and fertilizing life in the ocean, on land, and in the air.
Tsunamis can occur in coastal areas due to waves caused by earthquakes, volcanic eruptions, or other major geological disturbances.
Tides are the regular rise and fall in water level experienced by oceans in response to gravitational influences, and can vary greatly in tidal range and frequency in different coastal areas.
The average depth of the oceans is about 4 km, with the deepest point being the Mariana Trench at a maximum depth of 10,971 meters.
Oceanographers divide the ocean into different vertical and horizontal zones defined by physical and biological conditions, including the pelagic zone and the intertidal zone.
Ocean currents, including tidal, surface, and deep currents, are driven by various forces such as winds and temperature and salinity differences, and play a significant role in moving water and heat around the globe and affecting Earth's climate.
The thermohaline circulation is part of a global ocean circulation driven by the cooling of surface waters at polar latitudes and has important impacts on global climate and the uptake and redistribution of pollutants.
Oceans moderate the climate of locations where prevailing winds blow in from the ocean, and warmer ocean currents yield warmer climates in the long term.
Salinity is a measure of the total amounts of dissolved salts in seawater and can be calculated using chlorinity, which is a measure of the total mass of halogen ions.Overview of Earth's Oceans: Salinity, Dissolved Gases, pH, Alkalinity, Residence Times, Nutrients, Marine Life, Human Uses, Threats and Protection
Salinity is the measure of the amount of dissolved salts (such as sodium, chloride, and iodine) in seawater and has a major influence on the density of seawater.
The average ocean water chlorinity is about 19.2‰, and the average salinity is around 34.7‰.
Ocean water contains large quantities of dissolved gases, including oxygen, carbon dioxide, and nitrogen, which dissolve into ocean water via gas exchange at the ocean surface.
The process of photosynthesis in the surface ocean releases oxygen and consumes carbon dioxide, and this cycling of carbon dioxide in oceans is an important part of the global carbon cycle.
Seawater pH is slightly alkaline and had an average pH of about 8.2 over the past 300 million years; however, between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05 due to human activities.
Seawater alkalinity provides the chemical buffer that regulates the pH of seawater, and the carbonate and bicarbonate ions contribute more than 95% of this alkalinity.
Elements dissolved in ocean waters have a wide range of concentrations, and their concentration depends on their rate of supply to the ocean and their rate of removal.
A few elements such as nitrogen, phosphorus, iron, and potassium are essential for life, are major components of biological material, and are commonly called "nutrients".
The ocean has immense biodiversity, including phytoplankton, zooplankton, fish, mammals, and other organisms.
The ocean has been linked to human activity throughout history, serving a wide variety of purposes, including navigation, travel, shipping, food production, leisure, power generation, extractive industries, freshwater production, and more.
Human activities affect marine life and habitats through many negative influences, such as marine pollution, overfishing, ocean acidification, and other effects of climate change on oceans.
Protecting Earth's oceans ecosystem/s against its recognized threats is a major component of environmental protection and is closely related to sustainable development, and one of its main techniques is the creation and enforcement of marine protected areas (MPAs).Summary: Protecting Oceans on Earth and Beyond
A High Seas Treaty was signed in March 2023 allowing for the creation of marine protected areas in international waters, which could help reach the goal of protecting 30% of the oceans by 2030.
The new treaty is a significant conservation victory, according to Greenpeace.
Extraterrestrial oceans may be composed of water or other elements and compounds, with the only confirmed bodies of extraterrestrial surface liquids being the lakes of Titan.
There is strong evidence for subsurface water oceans on Jupiter's moons Europa, Ganymede, and Callisto, and Saturn's moons Enceladus and Titan.
NASA scientists reported in 2020 that exoplanets with oceans may be common in the Milky Way galaxy based on mathematical modeling studies.
The inner structure of gas giants is still not well understood, but it is suspected that oceans of liquid hydrogen may exist deep in the interior of gas giants like Jupiter.
Oceans of liquid carbon are hypothesized to exist on ice giants, such as Neptune and Uranus.