Note: The Spilhaus projection is centered on Antarctica and displays all the world’s oceans as a single continuous body of water.
There is potentially an infinite number of maritime shipping routes that can be used for maritime shipping, but the configuration of the global system is relatively simple. The main axis is a circum-equatorial corridor linking North America, Europe, and Pacific Asia through the Suez Canal, the Strait of Malacca, and the Panama Canal. These routes support the bulk of the traffic, but numerous other routes exist (namely for coastal shipping), depending on the origin and the destination of the maritime shipment. Transatlantic and transpacific traffic concerns a wide variety of ports, so there are numerous routes, most of them having a path along the great circle. Trans-Indian ocean traffic is dominantly intermediary traffic between Pacific Asia and Europe, implying a series of clearly defined routes between the Strait of Malacca and Bab el-Mandab.
Maritime routes are shaped by obligatory points of passage, which are strategic locations that act as chokepoints. Physical constraints (coasts, winds, marine currents, depth, reefs, ice) and political borders also play an essential role in shaping maritime routes. As a result, maritime routes try to follow the great circle distance. Core routes are those supporting the most important commercial shipping flows servicing major markets, and secondary routes are mostly connectors between smaller markets.
Due to geography, geopolitics, and trade flows, specific locations play a strategic role in the global maritime network. They are labeled as chokepoints and can be classified into two main categories:
- Primary chokepoints. The most important since they offer limited cost-effective maritime shipping alternatives, which would seriously impair global trade if disrupted. The first type of chokepoints concerns connectors along major oceans and seas. Among those are the Panama Canal, the Suez Canal, and the Strait of Malacca, which are key locations in the global trade of goods and commodities. The closure of these bottlenecks would force the diversion of maritime traffic over long distances with the associated loss of time and capacity. The Suez Canal blockage of 2021 is such an example. A second type of chokepoints concerns those connecting to maritime deadends with substantial resource and commercial potential, such as the Strait of Hormuz granting access to the Persian Gulf and the Strait of Bosporus granting access to the Black Sea. The Strait of Oresund is also of particular importance as it is the only access to the Baltic and Russia’s main ports. The closure of these bottlenecks would force the use of alternative overland routes unlikely to have the capacity to handle the volumes.
- Secondary chokepoints. Support maritime routes that have alternatives but would still involve a notable detour. These include the Magellan Passage, the Dover Strait, the Sunda Strait, and the Taiwan Strait.
Not depicted are the chokepoints granting access to major river systems having commercial navigation with a single point of access to the ocean. The most salient chokepoints are the Yangtse, the Rhine, the Mississippi, and the St. Lawrence.