Imagine living in a world ruled by dihydrogen oxide, a compound with no taste or smell and so changeable that it is usually benign but at other times quickly fatal. It can burn or freeze you. It can form carbonic acids so nasty that it strips leaves from trees and eats faces off statues. Even for those who live with it, it is often murderous. We call it water.
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Last updated
Sun, 30-Jun-2024
Water and the Science of Oceanography
Imagine living in a world ruled by dihydrogen oxide, a compound with no taste or smell and so changeable that it is usually benign but at other times quickly fatal. It can burn or freeze you. It can form carbonic acids so nasty that it strips leaves from trees and eats faces off statues. Even for those who live with it, it is often murderous. We call it water.
Water is everywhere. A cow is 74%, a bacterium about the same and a tomato, at 95%, is little but water. Even humans are 65% water, making us more liquid than solid by almost two to one. Water is strange. It is shapeless and transparent. It has no taste and yet we like drinking it. We travel long distances to see it. And even though it drowns tens of thousands every year, we swim in it.
Because water is everywhere, we can easily forget what an extraordinary substance it is. Almost nothing about it is the same as other liquids. If you knew nothing of water and based your ideas on the behaviour of other compounds chemically similar to it, you’d expect it to boil at -135 degrees Fahrenheit and to be a gas at room temperature.
Most liquids when cooled contract by about 10%. Water does too, but only down to a point. When it is near freezing, it begins – improbably – to expand. By the time it’s solid, it has a tenth more volume than before. Because it expands, ice floats on water. If it didn’t, ice would sink, and lakes and oceans would freeze from the bottom up. Without surface ice to hold heat in, the water’s warmth would radiate away, leaving it even colder and creating more ice. Soon the oceans would freeze and certainly stay like that forever and there’d be no life on Earth. Luckily for us, water seems unaware of the rules of chemistry or laws of physics.
Everyone knows that water’s chemical formula is H2O, which means that it consists of one largish oxygen atom with two smaller hydrogen atoms attached to it. Hydrogen atoms stick to their oxygen host, but also make casual bonds with other water molecules. A water molecule does a dance with others, briefly pairing and then moving on. A glass of water may not appear lively, but every molecule in it is changing partners billions of times a second. That’s why water molecules stick together to form puddles and lakes, but not so tightly that they can’t easily separate like, for instance, when you dive into a pool of them. At any moment, only 15% of them are actually touching.
In one sense, the bond is very strong. That’s why water molecules can flow uphill and why water drops on a car link up with their partners. It’s also why water has surface tension. The molecules at the surface are attracted more powerfully to ones beneath and beside them than to air molecules above. This creates a membrane strong enough for insects to walk on.
With no water, the body falls apart. Within days, the lips vanish, the gums blacken, the nose shrinks to half its length, and the skin gets so tight around the eyes that we can’t blink. Water is so vital to us we forget that all except the tiniest fraction on Earth is poisonous – deadly poisonous – because of its salts.
We need salt to live, but only in very small amounts, and seawater contains way more – about seventy times more – than we can metabolize. A litre of seawater contains only 2.5 teaspoons of common salt, the kind we sprinkle on food, but much larger amounts of other elements, collectively known as salts. The proportion of these salts and minerals in our tissues is similar to seawater: we sweat and cry seawater, but we cannot swallow it. Take a lot of salt into your body and your metabolism quickly goes into crisis. From every cell, water molecules rush to dilute the sudden salt intake. This leaves cells dangerously short of the water they need for normal functions. They become dehydrated. In extreme situations, dehydration will lead to unconsciousness and brain damage. Meanwhile, the overworked blood cells carry the salt to the kidneys, which eventually shut down. Without working kidneys you die. That’s why we don’t drink seawater.
There are 320 million cubic miles of water on Earth and that’s all we’re ever going to get. The system is closed: nothing can be added or subtracted. The water you drink has been there since the Earth was young 3.8 billion years ago. Dinosaurs drank it.
The water around us is overwhelmingly oceanic. 97% of all the water on Earth is in the seas, most in the Pacific, which covers half the planet, is bigger than all the land put together, and holds over half of all ocean water (51.6% to be precise); the Atlantic has 23.6% and the Indian Ocean 21.2, leaving just 3.6% for all the other seas. The average depth of the ocean is 2.4 miles, with the Pacific on average about a thousand feet deeper than the Atlantic and Indian Oceans.
Of the 3% of Earth’s water that is fresh, most is ice. Only the tiniest amount – 0.036% - is in lakes and rivers, and an even smaller part – 0.001% - is in clouds. Nearly 90% of the planet’s ice is in Antarctica, and most of the rest is in Greenland. At the South Pole, you’re standing on nearly two miles of ice, at the North Pole just fifteen feet. Antarctica alone has six million cubic miles of ice, enough to raise the oceans by two hundred feet if it all melted. But if all the water in the atmosphere fell as rain the oceans would deepen by only an inch.
Considering the importance of the seas, it is odd how long it took us to be interested in them. Until well into the nineteenth century, most knowledge about the oceans was based on what washed ashore or came up in fishing nets, and nearly all that was written was stories and guesswork. In the 1830s, the British naturalist, Edward Forbes, surveyed ocean beds throughout the Atlantic and Mediterranean and declared there was no life at all below 2,000 feet. It seemed reasonable. There was no light at that depth, so no plant life, and the pressure of water was extreme. So it came as a surprise when, in 1860, one of the first transatlantic telegraph cables was pulled up for repairs from more than two miles down, and it was covered with corals, seafood, and other living organisms.
The first organized investigation of the seas didn’t come until 1872, when an old warship left the English southern coast. For three and a half years it sailed the world, sampling waters, catching fish, and pulling up sand. It was boring work. But it sailed across 70,000 nautical miles, collected over 4,700 new species, gathered enough information to create a fifty-volume report, and gave the world the name of a new discipline: oceanography. It also discovered that there appeared to be mountains in the mid-Atlantic.
Because the seas were ignored by scientists, a few amateurs explored what was down there. Modern deep-water exploration begins with Charles William Beebe and Otis Barton in 1930. Although they were equal partners, the colourful Beebe has always received far more attention. Born in 1877 in New York, he decided on the life of an adventurer and, for the next 25 years, traveled through Asia and South America with always-changing but equally attractive female assistants. He paid for this by writing popular books with titles like Edge of the Jungle, though he also produced respectable books on wildlife and ornithology.
In the mid-1920s, on a trip to the Galápagos Islands, he discovered deep-sea diving. Soon afterward he teamed up with Barton, who also came from NYC and longed for adventure. Although Beebe nearly always gets the credit, it was in fact Barton who designed the first bathysphere and funded the $12,000 cost of building it. It was a tiny and strong chamber, made of iron 1.5 inches thick and with two small windows containing quartz blocks three inches thick. It held two men, but very uncomfortably. Even at that time, the technology wasn’t advanced. The sphere simply hung on the end of a long cable and had only the most primitive breathing system.
But the little bathysphere did the job it was intended to do. On the first dive, in June 1930 in the Bahamas, Barton and Beebe set a world record by descending to 600 feet. By 1934, they had pushed the record to 3,028 feet, where it would stay until after the war. Barton was confident the device was safe to a depth of 4,500 feet. At any depth though, it was risky. At 3,000 feet, their porthole was in nineteen tons of pressure per square inch. Death would have been immediate, as Beebe always mentioned in his many books, articles, and radio broadcasts. Their main concern, however, was that the steel cable would break and send the men to the seafloor. Nothing could have saved them.
The one thing their trips didn’t produce though was useful science. Although they saw many unknown creatures, visibility and the fact that neither man was an oceanographer meant they couldn’t describe their findings in detail. The sphere didn’t have an external light, only a 250-watt bulb they could hold up to the window, but the water below 500 feet was impossible to see through anyway, and they were looking into it through three inches of quartz. About all they could report was that there were a lot of strange things down there.
After their record-breaking descent of 1934, Beebe lost interest and Barton was eclipsed by a father-and-son team from Switzerland, Auguste and Jacques Piccard, who were designing a new type of probe called a bathyscaphe. On one of its first dives, in early 1954, it descended to below 13,287 feet, nearly three times Barton’s record-breaking dive of six years earlier. But deep-sea dives required a great deal of costly support, and the Piccards were gradually going broke. In 1958, they did a deal with the U.S. Navy, which gave the Navy ownership but left them in control. Now with a real budget, the Piccards rebuilt the vessel, giving it walls five inches thick and shrinking the windows to just two inches. But it was now strong enough for enormous pressures, and in January 1960 Jacques Piccard and Don Walsh of the U.S. Navy sank slowly to the bottom of the ocean’s deepest canyon, the Mariana Trench, in the western Pacific. It took just under four hours to fall 35,820 feet, or almost seven miles. Although the pressure at that depth was nearly 17,000 pounds per square inch, they noticed with surprise that they disturbed a flatfish just as they touched down. They had no facilities for taking photographs, so there is no visual record. After just twenty minutes at the world’s deepest point, they returned to the surface.
Forty years later, the obvious question is: Why has no one gone back since? To begin with, space travel was now a priority but it also didn’t actually achieve much. As a Navy official explained years later: “We didn’t learn a hell of a lot from it, other than that we could do it. Why do it again?”
When underwater researchers realized that the Navy would not carry out a promised exploration program, there was an outcry. Partly to silence its critics, the Navy provided funding for a maneuverable mini-submarine, though it wouldn’t go as deep as before.
About what else was down there, people really had no idea. Well into the 1950s, the best maps available to oceanographers were based on a little detail from a few surveys going back to 1929 and guesswork. The Navy had excellent charts to guide submarines, but it didn’t wish this information to fall into Soviet hands, so it kept its knowledge classified. Academics therefore had to make do with sketchy and antique surveys. Even today our knowledge of the ocean floors remains tiny. We have better maps of Mars than we do of our seabeds.
Investigative techniques have also been a bit random. In 1994, 34,000 ice hockey gloves were swept overboard from a ship during a storm in the Pacific. The gloves washed up all over, from Canada to Vietnam, helping oceanographers to trace currents more accurately than they ever had before.
Today the bathyscaphe is fifty years old, but it remains America’s best research vessel. A typical submersible costs about $40,000 a day to operate, so they are not put into the sea in the hope that they will come across something interesting. Humans may have seen perhaps a millionth or a billionth of the sea’s darkness. Maybe less. Maybe much less.
But oceanographers are hard-working and have made important discoveries with their limited resources – including, in 1977, one of the most important biological discoveries of the twentieth century. In that year, they found colonies of large organisms living on and around deep-sea vents off the Galápagos Islands – shrimps a foot long. They survived due to colonies of bacteria getting their energy and food from hydrogen sulfides – toxic to surface creatures – pouring from the vents. It was a world with no sunlight, oxygen, or anything else. Heat and energy flow from these vents. Two dozen together produce as much energy as a large power station, and the range of temperatures around them is enormous. It can be as much as 760 degrees Fahrenheit, while a few feet away the water may be only two or three degrees above freezing. A worm was found living right on the edges, with the water temperature 140 degrees warmer at its head than at its tail. The discovery transformed our understanding of the requirements for life.
It also answered a puzzle of oceanography – why the oceans don’t grow saltier with time. There is a lot of salt in the sea – enough to cover all the land on the planet to five hundred feet. Millions of gallons of fresh water evaporate from the ocean daily, leaving all their salts behind, so logically the seas ought to grow more salty with the passing years, but they don’t. Something takes the same amount of salt out of the water as put in. But what’s doing this?
The discovery of the deep-sea vents provided the answer. The vents were acting like filters in a fish tank. As water is taken down into the crust, salts are stripped from it, and eventually clean water is blown out again through the chimneys. The process is not quick – it can take ten million years to clean an ocean – but it is efficient if you are not in a hurry.
Perhaps nothing speaks more clearly of our lack of interest in our oceans than that the main goal for oceanographers in 1957–58 was to study “the use of ocean depths for the dumping of radioactive wastes.” This wasn’t a secret assignment, you understand. In fact, though it wasn’t much publicized, by 1957–58 the dumping of radioactive wastes had already been going on for over a decade. Since 1946, the US had been dumping 55-gallon drums of radioactive waste thirty miles off San Francisco, where it simply threw them overboard. Most of the drums were like those in gas stations or outside factories, with no protective lining. When they didn’t sink, which was usually, gunners shot them full of bullets to let water in (and, of course, plutonium, uranium, and strontium out).
And what effect might all this have had on life beneath the seas? Well, we actually have no idea. We are absolutely ignorant of life beneath the seas. Even the largest ocean creatures are little known, including the blue whale, whose tongue weighs as much as an elephant, whose heart is the size of a car and some of whose blood vessels are so wide that you could swim down them. Yet blue whales are a mystery to us. Much of the time we have no idea where they are – where they go to breed, for instance. What little we know comes almost entirely from their songs, but even these are a mystery. Blue whales will sometimes break off a song, then pick it up again at the same spot six months later. Sometimes they start a new song, which no member has heard before but which each already knows. How they do this is not understood. And these are animals that often come to the surface to breathe.
What about animals that never surface, like the giant squid? It weighs nearly a ton and is Earth’s largest invertebrate. If you put one in a swimming pool, there would be no room for anything else. Yet no-one has ever seen a giant squid alive. Zoologists have spent careers trying to capture living giant squid and have always failed. They are mostly washed up on beaches – particularly, for unknown reasons, the beaches of the South Island of New Zealand. They must exist in large numbers because they are the main diet of the sperm whale, and sperm whales take a lot of feeding.
There could be as many as thirty million species of animals living in the sea, most still undiscovered. The first idea of how much life there is in deep seas came in the 1960s with a dredging device that captures organisms not just on the seafloor but also buried in it. In a single one-hour dredge at about a mile deep, oceanographers netted over 25,000 creatures, or 365 species. Even at three miles, they found some 3,700 creatures and 200 species. But the dredge could only capture things that were too slow or stupid to get out of the way. In the late 1960s, a marine biologist lowered a camera with bait on it, and found still more, including swarms of fish. Where a good food source is suddenly available – for instance, when a whale dies and sinks to the bottom – as many as 390 species have been found eating it. Interestingly, many of these came from vents up to a thousand miles away.
So why, if the seas are so vast, do we so easily overtax them? Well, to begin with, the world’s seas are not full of food everywhere. Less than a tenth of the ocean is naturally productive. Most aquatic species like to be in shallow waters where there is warmth and light. Coral reefs, for instance, are under 1% of the ocean’s space but are home to about 25% of its fish.
Even where life thrives, it is often Life is also often extremely sensitive to disturbance. In the 1970s, fishermen discovered shoals of a little-known fish living about half a mile deep. They were known as orange roughy, they were delicious, and they existed in huge numbers. Soon, fishing fleets were catching forty thousand metric tons a year. Then biologists made some alarming discoveries. Roughy are extremely long lived and slow to grow. Some may be 150 years old. Roughy have adopted this unhurried lifestyle because their waters are so resource-poor. There, some fish spawn just once in a lifetime. Unfortunately, by the time this was realized the stocks had been severely depleted. Even with careful management it will be decades before the populations recover, if they ever do.
Elsewhere, however, the misuse of the oceans has been deliberate, not just accidental. Many fishermen “fin” sharks – that is, slice their fins off, then dump them back into the water to die. The World Wildlife Fund estimates the number of sharks killed each year is between 40 and 70 million.
As of 2005, 37,000 industrial-sized fishing ships, plus about a million smaller boats, were taking twice as many fish from the sea as they had just twenty-five years earlier. It is estimated that about a quarter of every fishing net hauled up contains ‘by –catch’ – fish that can’t be landed because they are too small or of the wrong type or caught in the wrong season. We just drop a net down and see what comes up. Perhaps twenty-two million metric tons of unwanted fish are dumped in the sea each year, mostly dead. For every kilo of shrimp caught, about four kilos of fish and other marine creatures are destroyed.
Nothing, however, compares with the cod. In the late fifteenth century, the explorer John Cabot found cod in incredible numbers on the eastern banks of North America. They were thought inexhaustible. Of course they were not. By 1960, the number of cod in the north Atlantic had fallen to an estimated 1.6 million metric tons. By 1990 this had sunk to 22,000 metric tons. In commercial terms, cod were extinct.
All this is a very roundabout way of saying that we know very little about Earth’s biggest system.
If you want to watch some videos on this topic, you can click on the links to YouTube videos below.
If you want to answer questions on this article to test how much you understand, you can click on the green box: Finished Reading?
Videos :
8. Walsh and Jacques Piccard (5:00)
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