How many oceans exist on Earth? Nowadays, there are two possible answers to this question. The first is five: this is the answer given in encyclopaedias and on knowledge platforms. It is usually accompanied by a world map of the type familiar to most of us from our school days, showing the continents as great land masses that separate four of the five oceans from each other. On the left- and right-hand margins of the map, there is the vast Pacific. The Atlantic takes pride of place in the centre, while the Indian Ocean is shown on Africa’s eastern seaboard and the Southern Ocean encircles the Antarctic. That just leaves the Arctic Ocean, squeezed in right at the top.
But this is not the only way to think about the Earth’s basic geography. There are other, very different options, such as that described by American geophysicist and oceanographer Athelstan F. Spilhaus in an article for Smithsonian Magazine in November 1979. In it, Spilhaus published a world map in the form of a square, with the five oceans and their respective seas depicted as one collective body of water, one ocean, in the centre, framed and delineated by the continental coastlines.
Spilhaus’s world ocean map fell into oblivion for almost four decades after its publication, known only to a handful of ocean enthusiasts, who dusted it off whenever they wanted to show that a change of perspective and a new holistic understanding were required for effective marine conservation. Nowadays, however, Spilhaus’s concept has the backing of ocean researchers and is steadily gaining in appeal. International organizations such as the United Nations increasingly refer, in their special reports, to one ocean whose water masses circulate in four ocean basins. Manufacturers of geographic information systems now offer the Spilhaus projection as a map template and the latest specialist publications on ocean management urge their readers, from the first chapter onwards, to think differently about the world, away from their preconceptions formed by life on land.
The rationale is as follows: the structure and functions of the ocean are so unique that attempts to manage the ocean with the same, often small-scale, methods and strategies that work on land are bound to fail. Unlike the land masses, the ocean has virtually no boundaries or barriers. When a tsunami inundated the Fukushima nuclear plant in Japan in March 2011, radioactive water escaped into the sea. Over the next three years, ocean currents carried this water from the coast of Japan all the way across the northern Pacific, with nothing – neither an army nor a deep-sea trench – to stand in their way. Likewise, plastic litter and other debris are transported freely around the world on the ocean currents. And of course, human-defined boundaries between areas pose no obstacles to shoals of fish or migrating whales. As its name suggests, the World Ocean Review sees the world’s oceans and seas as a single entity, the ocean. Nevertheless, as before, this latest edition uses a variety of terms – ocean, oceans and world’s seas – interchangeably.
fig. 1.10 > The world map in the form of a square (left): Designed by American geophysicist and oceanographer Athelstan F. Spilhaus, this depicts the five oceans as one collective body of water, one ocean, with the Antarctic in the centre. Most people are more familiar with the conventional type of world map (right), which shows the continents as great land masses separating the Pacific, Atlantic and Indian Oceans.