Covering about 70% of the earth's surface, the oceans are a highly productive system which continuously recycles chemicals, nutrients and water through the 'hydrological cycle', which powers climate and weather, and which regulates global temperature by acting as a giant heat reservoir from the sun. The oceans contain a rich array of plant and animal life. About two-thirds of the world's population live within 60 kilometres of the coast, and almost half of the world's cities with more than one million people are sited in and around the tide-washed river mouths known as estuaries. From a human point of view, oceans are also a major source of food and employment, and provide natural routes for communication, transportation and trade.
The About section was sourced from Man and the Ocean, a product of the Russian Head Department of Navigation and Oceanography (HDNO), and from the National Oceanic and Atmospheric Administration (NOAA), both foundation partners of the UN Atlas of the Oceans. It is now managed by the UN-Oceans agencies.