Ozeanen

The oceans are vast, interconnected saltwater basins that cover about 71 percent of Earth's surface and contain the majority of its biomass. They are conventionally divided into five named oceans—the Pacific, Atlantic, Indian, Southern, and Arctic—though scientists emphasize their connectedness as a single global ocean governed by shared circulation patterns.

Physically, the oceans vary in depth from shallow continental shelves to the deep trenches, with a mean depth around 3,700 meters. The deepest point, the Challenger Deep in the Mariana Trench, reaches about 10,900 meters. The oceans have an average salinity of about 35 parts per thousand and exhibit complex vertical structure, with surface currents driven by winds and deep currents driven by density differences (thermohaline circulation).

The oceans play a central role in climate and weather, absorbing most of the excess heat from the atmosphere and a substantial portion of anthropogenic carbon dioxide. They drive climate patterns through currents and upwelling and influence regional weather, rainfall, and the intensity of storms.

Marine life is diverse, from microscopic plankton to large whales, with important habitats including coral reefs, kelp forests, mangroves, and the deep sea. Human activities rely on the oceans for transportation, food, energy, and minerals, but overfishing, pollution, habitat destruction, and ocean acidification threaten many ecosystems.

Governance includes international law, notably UNCLOS, and measures such as marine protected areas and pollution controls. Ongoing scientific programs monitor ocean processes, track changes, and support sustainable use, as part of initiatives like the United Nations Decade of Ocean Science for Sustainable Development.