The Ocean

Geography & Processes

70 per cent of the earth's surface is covered by the oceans. These vast reservoirs, together with inland waters, ice, snow and water vapour, form what is known as the hydrosphere. The ocean covers a total area of 361,253,200 square kilometres and has an average depth of between three and five kilometres. The Marinas Trench in the Pacific, where a sounding of 11,040 metres has been made, is believed to be the deepest part of the ocean.

Ninety-three per cent of the earth's water is stored in the oceans and polar sea ice, while most of the remainder is stored as underground water (four per cent). All the rivers, lakes, snow caps, glaciers and clouds together contain less water than is stored underground. Only a tiny proportion of the earth's fluid mass is contained in living organisms but all these forms of life have a high proportion of water in their bodies.

The life cycle of the ocean, as that of the earth, is the closest one can ever get to the greatest of all inventions, perpetuum mobile, the perpetual motion machine. And the secret is that nothing was composed by nature that could not be recomposed by nature that could not be recomposed, recycled and brought back into service again in another useful wheel in a smooth running global machine.
Robbie Newman, op. cit.

The ocean is constantly moving and so is the air. The two are inextricably linked. The ocean's surface circulation is driven by wind and by density differences. The atmospheric heat engine, powered by the sun, is also driven by the sea.

The polar nature of the water molecule causes it to form polymer-like chains of up to eight molecules. A certain amount of energy goes into linking the molecules in these chains. This explains the ocean's ability to absorb and retain heat energy that then may be transported by ocean currents. The molecular chains of up to eight molecules occur for about 90 per cent of all of the molecules. As a consequence, water has the highest heat capacity of all liquids except ammonia. Again this is due to the energy that goes into the chain formation. This high heat capacity is the primary reason that the ocean is so important in the world climate system. Unlike the land, the ocean stores large amounts of the heat energy that it receives from the sun. This heat is carried by ocean currents, thereby exporting or importing heat to various regions. This aspect of the ocean plays an important role in the interaction between the sea and atmosphere and the determination of global climate.
Pickard and Emery, The Physical Properties of Seawater (Ch. 3), University of California

The sea in motion represents the essence of life. Alternately focused and dispersed, swelling and receding, the tremendous energy of the atmosphere and the ocean combine to form some of the most spectacular of nature's physical interplays.

Another important effect of the chainlike molecular structure is the high surface tension of water. This is due to its high viscosity for its atomic weight due to the chains resisting shear. In the ocean, one effect of this can be seen in the formation of surface capillary waves with wavelengths on the order of centimetres and whose restoring force includes surface tension as well as gravity. Such capillary waves, despite their small size, are important in determining the friction between wind and water which is responsible for the generation of larger waves and for the frictionally-driven circulation of the surface layer of the ocean.
Pickard and Emery, op. cit.