Ever asked the question: How much of the ocean has been explored? There is an unending curiosity about the world beneath the enormous blue water expanse covering the earth's surface. We have five oceans: the Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean, and Southern Ocean.
These oceans cover 70% of the earth's surface, making it one of the largest ecosystems on the planet. It is home to a lot of marine life, like coral reefs, marine mammals, fishes, birds, and plants. Despite how the information we have about the ocean seems enormous, we have yet to scratch the surface of the oceanic world.
This article aims to answer a major question: How much of the ocean have we explored? We shall explore the history of modern oceanography, recent exploration discoveries, and oceanography technology. Also, we'll examine some limitations of ocean exploration.
We have five ocean bodies in the world. They are the Atlantic, Indian, Arctic, Southern, and Pacific Oceans. However, we are yet to explore more than eighty percent of our ocean. We rely a lot on this body of water for transportation, trade, and food. But we need to learn about the world beyond the water's surface.
About 35% of the ocean and coastal waters have been explored in the United States. And globally, recent numbers say it is 24.9%.
Satellite imaging only helps with ocean surface exploration. It only checks the ocean’s surface temperatures, water levels, and surface marine life. Satellites are better at mapping out outer space.
Ocean exploration hasn’t seen more progress because of the unbearable conditions of the ocean’s deepest point. The sunlight zone refers to ocean areas that receive sunlight3. Light can’t pass through the deep ocean because water absorbs light. Sunlight can only reach water depths of 656 ft (200 m).
As you go deeper, you’ll only meet complete darkness. Ocean exploration can be challenging in total darkness because you can't see the ocean floor clearly, therefore missing out on essential details.
Humans began ocean exploration long before the 20th century. Ancient civilizations observed the rise and fall of the ocean tides to aid their traveling and hunting activities.
Between 7250 BC and 4000 BC, humans recorded one of the earliest sea voyages in history. During this period, the Polynesians migrated and settled on islands around the Pacific. Also, the Egyptians developed the art of shipbuilding and ocean exploration schemes.
From 4000 BC to 500 BC, Polynesians constructed large ships. They used these ships to travel and colonize neighboring islands around the Pacific Ocean. Shipbuilders, sailors, and traders ruled the Mediterranean area following the end of the Egyptian empire.
Ancient humans discovered a Greek map in 450 BC that shows the Mediterranean coast. However, they referred to it by its old name, Thalassa. They referred to the Mediterranean Sea as Oceanus.
Scholars offered ocean features and atmospheric processes between 384 BC and 322 BC. One of these scholars is Aristotle. Aristotle established a direct relationship between evaporation and precipitation. He also started the habit of cataloging marine life. By 300 B.C., navigators used the pole star to recognize latitude.
Venerable B.D., an English historian, discovered that the moon controls the ocean tides between 673 and 735 A.D.
Prince Henry, the navigator, founded a navigation school and sent ships out to explore the ocean in 1418 AD.
In 1529 AD, a Portuguese cartographer created the map of the world. In this map, he correctly highlighted the largeness of the Pacific Ocean, China, India, South and North poles.
Lippershey of the Netherlands invented the telescope. In 1643 AD, Torricelli of Italy invented a barometer and forecasted storms.
In 1735 AD, John Harrison of England invented the chronometer. It was the first clock that kept time within a few seconds over the course of a year-long sea journey.
Benjamin Franklin published the map of the Gulf Stream in 1769 A.D. Six years later, Perier of France invented the steamship.
From the years 1768 to 1779, Captain James Cook embarked on three great voyages to explore and chart the Pacific.
Bushnell of America created the first workable submarine in 1776. Companies started the development of commercial steamships 11 years later.
In 1828, J. Vaughan Thomson studied marine plankton from the Irish Coast. He was also the first researcher to describe the planktonic stages of crabs.
Charles Darwin collected and studied several marine life forms between 1831 and 1836 A.D. during his voyage around the world. His research led to the creation of his famous subsidence theory of coral reef formation and the classification of barnacles.
Joseph Hooker discovered planktonic diatoms were plants in 1847 A.D. He claimed they have similar ecological functions in the sea as green plants on land.
Oceanography further expanded as German zoologist Anton Dohrn established one of the first marine biological stations to accept visiting scientists from other countries. He established the marine biological station, Stazione Zoologica de Napoli, in 1872 AD.
Luis Agassiz established the first marine biological laboratory called the Anderson School in 1873. In the same year, Charles Wyville Thomson, a professor of natural philosophy at the University of Edinburgh, published one of the first oceanography textbooks. Its title was The Depths of the Sea.
The first ocean explorations to circumnavigate the world happened between 1872 and 1876 A.D. It surveyed all of Earth’s oceans except the Arctic Ocean. Most considered this exploration of modern oceanography because it used standard methods to collect data.
Also, it investigated several aspects of physics, chemistry, geology, and biology. It was one of the oceanographic expeditions that established the existence of life at extreme ocean depths.
Much of the ocean depths discoveries occurred from 1886 to 1922 A.D. through expeditions like Princesse Alice I & II and Hirondelle I & II. Between 1887 and 1925, expeditions on the U.S. ship Albatross made many collections in the Indian Ocean and Pacific.
In 1888, the Anderson School, established by Luis Agassiz, became the Marine Biological Laboratory (MBL). It started with two instructors, eight students, and seven investigators. Also, in the same year, the Marine Biological Association of the United Kingdom established a marine biological laboratory in Plymouth.
The National Expedition made several plankton collections in 1889. In 1898 to 1899, Valdiva's German expedition made several deep-sea explorations. They collected various deep sea life and studied the vertical distribution of pelagic organisms.
King Oscar Ⅱ of Sweden established the International Council for the Exploration of the Sea (ICES) in 1902. From 1904 to 1913, the Michael Sara Expedition from Norway made several collections from the North Atlantic Ocean.
The year 1906 saw the establishment of the oceanographic museum and aquarium. Prince Albert Ⅰ created the museum and aquarium to store his marine species collections from his sea voyages.
A research organization established by William Ritter founded the Scripps Institution of Oceanography in La Jolla in 1924. He was a student of Alexander Agassiz. Discovery Ⅰ & Ⅱ expeditions studied Antarctic ecology from 1925 to 1939.
In 1934, zoologists William Beebe and Otis Barton were the first people to study the deep sea floor and marine species directly from the bathysphere. They reached 3,072 ft (936 m) in the ocean with the bathysphere connected to the ship.
The Galathea Denmark expedition made deep sea collections from all the world’s oceans from 1950 to 1952. They collected specimens from an ocean depth of 6.2 mi (10 km).
The Vitiaz expedition from the USSR studied the biological aspect of deep-sea trenches between 1957 and 1960.
In 1960, a United States and Swiss team made the deepest manned dive, reaching 6.78 mi (10.92 km) in the Mariana Trench. They also created the Loran navigation system that used radio signals in 1960. Additionally, they started using drill ships to collect rock and sediment samples in 1967.
Robert Ballard of WHOI found the benthic community in the mid-oceanic ridge hydrothermal vent in 1977. Two years later, a Mexican-French-American research program known as the Riviera Submersible Experiment investigated the sea floor hot springs near the tip of Baja California.
The Joint Air-Sea Monsoon Interaction Experiment (JASMINE) conducted scientific research in the Indian Ocean region and the southern Bay of Bengal in 1999. Scientists used two research vessels: the NOAA research vessel Ronald H. Brown and the Australian research vessel Franklin.
Between 1998 and 2002, they conducted an acoustic survey around the Peruvian coast. The survey was to understand how oceanographic conditions influence anchovy distribution and behavior.
In 2000, they conducted a survey that used satellite-monitored radio tags on the North Atlantic whales using the NOAA ship Delaware Ⅱ. The purpose of the survey was to record the fall emigration of whales from their summer feeding grounds and discover the wintering areas.
In 2003, scientists from 4 marine organizations conducted a 4-day cruise in the northern regions of southeastern Alaska. The organizations are Auke Bay Laboratory, the Alaska Fisheries Science Center, the National Marine Fisheries Service, and the NOAA Fishery Unit. They wanted to gather information on the ecology and distribution of juvenile Pacific salmon.
Steward Johnson conducted deep sea exploration in 2004. In 2005, scientists from the University of Puerto Rico undertook an expedition to observe mesoscale eddies. Mesoscale eddies are large oceanic whirlpools that occur from the east Caribbean to the west Caribbean2.
Most of the plant life and marine animals we’ve discovered are around the sunlight zone. The sunlight zone covers about 3% of the ocean. Here are some recent discoveries about Earth’s oceans:
Ocean exploration is nearly impossible without technological tools assisting us. As we all know, the global ocean is so vast, with multiple deep points. Even with ocean exploration technology, we have yet to reach the ocean’s deepest point. Here are some ocean exploration technologies:
Underwater vehicles, unlike ships, can access the deep sea floor. Ocean scientists use it to access ocean areas divers can’t reach. There are various types of underwater vehicles. They are:
Autonomous underwater vehicles aid deep-sea exploration because of their ability to collect data. They are robotic vehicles programmed by scientists to operate on their own. AUVs allow scientists to multitask during an expedition.
Remotely operated vehicles are robots connected to the surface ship. Scientists control the robot from the ocean’s surface to observe and collect data and samples. The tether sends and receives control signals that target specific data and carry out specific experiments on deep ocean floors.
Hybrid remotely operated vehicles are a mix of autonomous and remotely operated underwater robots. An HROV operates as an autonomous underwater vehicle that can collect data, samples, and experiments on its own. Scientists can also control it through its micro-thin, fiber-optic connection to a surface vessel.
Human-occupied vehicles are deep-sea submarines. They transport small groups of scientists, pilots, divers, and their equipment to the ocean floor. It improves environmental evaluation and sensory surveillance.
Measuring ocean currents is fundamental in ocean exploration. It helps scientists determine the transportation methods of ocean life, nutrients, and biological and chemical compounds.
The acoustic Doppler current profiler is an instrument that uses sound waves to calculate the speed and direction of ocean currents. It uses a series of acoustic transducers to receive and produce sound pings from various directions. Scientists usually mount them on stationary objects like the ocean floor, mooring buoys, or moving vehicles.
CTD is an electronic device package containing a series of small probes. It helps ocean scientists identify the changes in ocean temperatures and conductivity at various levels of ocean depths.
They can use it independently or attach it to observing platforms, i.e., remotely operated vehicles and fixed observing buoys. Some CTD devices transmit real-time data back to the ship, while some just store data until scientists retrieve it from the ocean.
Measuring the ocean’s surface temperatures and salinity aids helps us understand the biological processes of marine life. For instance, it helps us understand the growth of algae. It also helps us understand the distribution of fish that need specific ocean temperatures and salinity to survive.
Sonar stands for Sound Navigation and ranging. It is an instrument that uses sound waves for deep ocean exploration. Oceanographers use sonar technology to create nautical charts and locate dangerous underwater objects. They also use it to search for and detect objects on the ocean floor. They even use it to map out sea routes and ocean depths.
There are two forms of sonar. They are active sonar and passive sonar. Active sonar produces its sound signal into the water, returning an echo whenever it bounces off an object on the ocean floor. It can measure the strength of the echo it receives. With this, it can determine the range and orientation of the thing. Examples of active sonar are multi-beam, side-scan, synthetic aperture, and split-beam sonar.
Passive sonar does not produce its own sound signal. It can only detect the sound signals coming from objects around it. Also, it can’t measure the range of the object it receives signals from unless it uses it with other listening devices. Scientists mostly use it to detect sounds from submarines, ships, and marine life, i.e., whales.
There are reasons we haven't done much ocean exploration as a human species. We have mostly explored most of the global ocean’s surface, but there are vast areas of the deep ocean floor we haven’t explored. The most common limitation that stops us from exploring the deepest points in the global ocean is its cost.
It is costly to explore the deep ocean floor. Another limitation we face is technological advancement. Ocean exploration technologies have limitations. They can’t explore the deepest ocean point yet. Other limitations apart from these two limitations are:
The world's oceans have great depths that humans cannot explore, with the average depth of the ocean being 12,100 ft away from the surface. The ocean's deepest point is known as the Challenger Deep. It is approximately 36,876 ft deep.
The water pressure at these points is greater than the one on the ocean's surface. At the surface sea level, the pressure is about 14.6 pounds. However, the pressure increases about 500 times as you swim further into the ocean. The furthest an average diver can reach before losing oxygen is 250 feet.
The ocean's pressure causes oxygen and nitrogen to dissolve in the blood, often leading to nitrogen narcosis. Nitrogen narcosis makes the diver dizzy and reduces the capacity to make simple mental reasoning. You need special instruments like underwater vehicles to get past 100 ft in the water. Some submersibles built improperly can't withstand the pressure, so they implode after reaching a certain level in the ocean1.
An example of submersible implosion is OceanGate's Titan submarine. Submersibles should maintain the pressure a human body can withstand. To make this possible, most submersibles have a controlled pressure hull. However, this limits the capabilities of the machine because the hull is about one-third of its weight.
Another problem that limits how much of the ocean we can explore is seawater damage. Seawater has strong chemical properties that can degrade ocean exploration tools. Saltwater corrodes mechanical components, which could lead to electrical fire and electrocution.
A limited amount of diving period affects both humans and oceanographic instruments. It takes a lot of time for an underwater vehicle to reach and explore its required depth. It can only stay for a required amount of time before it has to surface again for maintenance.
An example of this is the Alvin human-occupied vehicle (HOV). It can stay underwater for 30 days at a depth of 6,500 meters. After 30 days, it must come aboard to the surface shop for a single-day maintenance schedule before it can dive again.
Remote-operated vehicles (ROV) last longer underwater than human-operated vehicles. They last three hours longer than a HOV. It is advisable to send an ROV to a required depth to collect data before sending an HOV.
The ocean covers a large majority of the earth’s surface. We benefit from the numerous ocean resources, and our curiosity makes us wonder about how much of the ocean we are yet to discover. We have only discovered a small percentage of the ocean.
Throughout ocean exploration history, we witnessed gradual growth and developments in oceanography. We hope to make more advancements with oceanography technologies and discover all that lies on the ocean floor.
Maxouris, C., & Yan, H. (2023, June 29). ‘Presumed human remains’ from the Titan submersible wreck will be analyzed as investigators try to unravel how the disaster unfolded. CNN. Retrieved September 6, 2023
Mitra, Abhijit. (2014, March 9). HISTORY OF OCEANOGRAPHY. ResearchGate.
Woods Hole Oceanographic Institution. (n.d.). Sunlit zone.
Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.
Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.