oceanen

The oceans are vast, interconnected bodies of saltwater that cover about 71% of Earth's surface and contain roughly 1.33 billion cubic kilometers of water. They are conventionally divided into five named basins: the Pacific, Atlantic, Indian, Southern, and Arctic Oceans. The global ocean spans about 361 million square kilometers, with an average depth near 3,700 meters and areas of extreme depths in submarine trenches. The salinity of seawater averages about 35 practical salinity units.

Ocean circulation is driven by wind, differences in temperature and salinity, and Earth's rotation. These forces create major surface currents and a global overturning circulation that redistributes heat and nutrients, influencing climate and weather patterns. The oceans host diverse life and ecosystems, from sunlit coral reefs and kelp forests to the dark, high-pressure realms of the deep sea. Phytoplankton and other microorganisms form the base of most marine food webs, supporting a wide range of marine animals and human fisheries.

Humans depend on the oceans for food, transport, energy, and climate regulation. However, they face threats from overfishing, habitat loss, plastic pollution, and rapid ocean warming and acidification due to greenhouse gas emissions. Sustainable management and mitigation are pursued through science, international law, marine protected areas, and the United Nations Sustainable Development Goal 14.

Historically, oceanography emerged from coastal navigation and exploration and progressed with sonar, satellites, and deep-sea drilling. Ongoing research aims to map biodiversity, chemistry, and topography to support conservation and resilient coastal communities.