Author: IOC-UNESCO
Our Blue Planet
The ocean is one massive body of water, connected throughout the globe, also known as the Global Ocean, covering almost 71% of Earth’s surface and containing more than 97% of the planet’s total amount of water. It is also the largest ecosystem on Earth: it represents 99% of all the planet’s biosphere. It is from the ocean that 50-80% of the oxygen we breathe thanks to the Process of photosynthesis that tiny marine algae known as phytoplankton produce.
Oceans regulate the global climate by moving warm and cold masses of sea waters around the planet. Warm currents move to the Poles along the surface, and as they reach the Poles they cool down, and sink, circling back from the depths towards the equator; this regulates the global climate and maintains the balance of marine and land ecosystems.
The ocean provides humans with millions of jobs, goods, and services all around the world, but also absorbs huge amounts of CO2 that we produce, which is one of the major causes of climate change.
Due to cultural, geographical, and historical factors, human beings have divided the ocean into five recognized ocean basins: the Pacific, Atlantic, Indian, Arctic and Southern Ocean basins.
In this article, we will focus on the largest ocean basin on the planet, and find out all its details and characteristics.
Which is the largest Ocean basin?
The largest ocean basin is, by far, the Pacific. It stretches from the Western coasts of North and South America to Oceania, Asia and Russia in the North.
Its name comes from the fact that Portuguese explorer Ferdinand Magellan, during his journey to the Philippines, found the Ocean to be quite peaceful, thus “pacific”.
The Pacific Ocean basin has twice the area and more than two times the water volume of the Atlantic, which comes next in terms of size. One curious fact is that the area of the Pacific exceeds the land of all continents put together.
Occupying almost 32% of the Earth’s surface, the Pacific covers 165,250,000 square kilometers (63,800,000 sq. mi), roughly 46% of the water surface on Earth. The vast ocean contains approximately 30,000 islands divided between the Polynesia, Melanesia, and Micronesia regions.
The Pacific also connects to the Indian Ocean basin close to the Strait of Malacca, Sumatra, and to the Atlantic by the Strait of Magellan and the Drake Passage. Its greatest latitudinal extent reaches 19,000 km (12,000 miles) between the coast of Colombia and the Malay Peninsula.
Ocean circulation (caused by the Coriolis effect) subdivides it into two largely independent volumes of water, which meet at the equator: the North(ern) Pacific Ocean and South(ern) Pacific Ocean. The Galápagos and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific.
The North Pacific is the part of the Pacific Ocean basin that lies North of the Equator. It stretches from the Eastern coasts of Asia to the Western Coasts of North and South America (until the Equator) and extends northward to the Arctic region. The South Pacific lies South of the Equator, covering a major part of the Southern Hemisphere (SH) and plays an important role in the global climate system.
Temperature
The ocean is stratified, and one of the main factors of this stratification is temperature: the bottom waters, which contain about 80% of the ocean’s volume, are very cold, with stable temperatures just above freezing, usually around 3.5 °C (38.3 °F). In the surface zone, on the other hand, up to a depth of around 300 meters (1,000 feet) temperatures vary greatly. Usually, water temperatures in the North Pacific are slightly higher than those in the South Pacific. This is due to land to sea ratio, and to Antarctica’s and the Southern Ocean basin’s influence.
Salinity
The highest surface salinities in the open Pacific occur in the southern Pacific area, where they reach 37 parts per thousand; in the corresponding trade-wind belt in the North Pacific, the maximum salinity seldom reaches 36 parts per thousand.
The low salinity can inhibit deep-water formation at high latitudes and may limit heat transport towards the pole. Since there are no major rivers draining to the North Pacific, the source of the low surface salinity can be traced back, at least in part, to the heavy rainfall of the Intertropical Convergence Zone (ITCZ).
Climate
The climate patterns of the Northern and Southern hemispheres generally mirror each other. In the North Pacific, conditions are not as uniform as they are in the southern part of this massive body of water.
Specifically, in the North, there are considerable differences between the eastern and western regions in the same latitude: the extreme temperatures that characterize the winters off the east coast of Russia, for instance, contrasts sharply with the relative mildness of winters in British Columbia.
The tropical and subtropical areas of the Pacific ocean are periodically affected by weather oscillations known as El Niño and La Niña Southern Oscillations. These two represent periodic climate patterns that cause, respectively, heating and cooling processes of ocean waters. The timeframe of these atmospheric phenomena lasts about three-months and it is determined by the average sea-surface temperature of the southeast area of Hawaii: if it is more that 0.5 °C (0.9 °F) above or below normal for that period, then an El Niño or La Niña is considered in progress.
The Pacific ocean comprises further climate phenomena, known as tropical cyclone basins. Among these, we recognize the Pacific hurricanes that normally originate in the Gulf of Mexico and, sometimes, hit the United States’ coasts between June and October. On the other hand, typhoons form in the northwestern area of the Pacific, hitting southeast Asia from May to December. Pacific islands are occasionally subject to tropical cyclones that form in the southern Pacific basin.
Biodiversity
Of all the world’s oceans, the Pacific boasts the most diverse marine biodiversity. This is because the currents that connect the southern and northern polar waters of the Pacific allow the mixing of life forms coming from other oceanic regions.
One of the main features of this variety is given by the kelp beds found on the rocky cold-water coasts of North and South America. These forest-like environments are home to a great range of marine life, from invertebrates to fishes, and have an animal biodiversity almost as varied as that of the rainforests.
In the tropical climates of the Western Pacific, the wealth of marine animals obviously increases exponentially, and here we can find the richest and most extensive coral reefs of the planet. The coral reefs of the South Pacific are low-lying structures that have built up on basaltic lava flows under the ocean’s surface. One of the most dramatic is the Great Barrier Reef off northeastern Australia with chains of reef patches.
Whales, sea turtles, sea otters, and sea lions are a prominent and spectacular component of Pacific marine life.
Geology
Research has shown that all the major features of the Pacific Ocean basin floor and the land that surrounds it originate in plate tectonics.
Another well known feature of the Pacific is the “Ring of Fire”, where most of the world’s active volcanoes lie underwater. The Ring of Fire is an arc of volcanic islands and deep trenches in the Western part of the Pacific where two tectonic plates are colliding (convergent zone), forcing one under the other. Due to this, the Pacific Ocean basin is currently shrinking by roughly 2.5 cm (1 in) per year on three sides, roughly averaging 0.52 km2 (0.20 sq mi) a year. By contrast, the Atlantic Ocean is increasing in size.
As tectonic plates move abruptly, earthquakes are felt all around the Ring of Fire. It is no news that the strongest earthquakes ever recorded have happened around the Ring of fire; The earthquake that struck near Valdivia, Chile, in 1960 was the most powerful temblor in recorded history 9.5 magnitude; in 1964 the Great Alaska Earthquake 9.2 magnitude and in 2011, Tohoku Earthquake, Japan 9.1 magnitude.
On the other hand, the East Pacific Rise is an active spreading center, which is where new crust is created, and in the south-eastern Pacific, the Nazca Plate and the South American Plate collide to form the Andes Mountains and, a short distance offshore, the Peru-Chile Trench. The floor of the north-eastern Pacific is known for its various fracture zones, which, in some cases, are identifiable over great distances.
The deepest spot in the Pacific Ocean basin is known as the Challenger Deep in the Mariana Trench, at a depth of 11,034 m (36,201 ft). It is the deepest recorded point in the world, located east of the Philippines. It is so deep that Mount Everest would fit in the Challenger Deep with over a mile to spare!
Mineral resources
The Pacific Ocean basin contains enormous mineral resources of which only a few have been exploited, like salt, bromine, and magnesium. Minerals can be extracted from the seawater itself, from alluvial deposits, or from the continental shelf. Underwater exploration for oil has also occurred near Vietnam, the Philippines, Indonesia, California, Russia, and China. There are also known deposits of natural gas in the continental shelf of both the northern and southern hemispheres.
Threats
As the whole Pacific Ocean basin, the North Pacific is under threat. One of the main issues, as it is now clear, is marine pollution, mainly plastic and other debris.
In the Pacific, we find the largest garbage patch, also known as the “Great Pacific Garbage Patch”, which is a huge plastic accumulation area found at the center of both Northern and Southern Pacific gyres.
Pollution is mainly caused by littering, maritime transportation (90% of global htrade currently uses sea routes), mining and drilling, oil spills and ocean dumping (the direct discharge of pollutants in the ocean from industries, ships, or sewage plants).
Other serious threats to the balance of the Pacific Ocean basin are overfishing and illegal fishing practices, which destroy marine ecosystems and leave behind an incredible number of harmful debris.
