What do we know about the origin of the earth's oceans? Is it more likely that they derive from icy comets that struck the young earth or from material released from the earth's interior during volcanic activity? - Scientific American
How Did Earth Get Its Ocean? – Woods Hole Oceanographic Institution
In the early days of our solar system, when Earth and other planets were still taking shape, the dashed white line represents the “snow line”—the transition from the hotter inner solar system, where water ice was not stable (brown), to the outer solar system, where water ice could exist (blue). Encircling the inner edge of the snow line was a belt of asteroids that included a large one called Vesta. There are three hypotheses for how the inner solar system received water: 1) water molecules stuck to dust grains inside the snow line (inset), 2) meteoritic material was flung into the inner solar system by the effect of gravity from protoJupiter, and 3) comets brought water to the inner solar system after the planets were formed. Ph.D. student Adam Sarafian’s research showed that the second scenario most likely occurred within the first 14 million years of the solar system’s history.
(Illustration by Jack Cook, WHOI Graphic Services)
How Did Earth Get Its Ocean?
A student’s quest to learn the origin of our planet’s water
Adam Sarafian came to Woods Hole Oceanographic Institution (WHOI) as a graduate student to learn how Earth got its ocean in the first place.“The big question is, how and when did the planet get its water?” said Horst Marschall, one of Sarafian’s Ph.D. advisors at WHOI. “All peoples have myths about where water came from. In Genesis in the Old Testament, in Norse myths, and Greek myths too—it’s an old question.”
Indeed, it’s one of the oldest questions in the solar system, and there are two possible answers, Sarafian said: “Either the Earth was formed and dry, sitting there, waiting for water, and the water came from comets or other wet bodies hitting Earth relatively late in history. Or, the water came from inside Earth—meaning Earth got its water while the Earth was still forming, and then volcanoes out-gassed steam and other water-containing compounds to the surface.”
Ironically, answers to the mystery lay not in liquid water but in solid rocks. Sarafian and colleagues pursued a painstaking path to extract evidence from rare samples of ancient meteorites that had fallen to Earth.
But Sarafian was no stranger to persistence. He overcame a learning disability that makes it hard for him to read and surmounted heights as a an All-American pole-vaulter—all before launching a scientific career that has now allowed him to hurtle across the universe and back through time to the period when Earth was still forming.
In the beginning
The question about the origin of Earth’s water first arose in Sarafian’s undergraduate classes and continued as he pursued a master’s degree at Georgia. “The answer was always ‘we don’t know!’ ” he said.
In the nascent days of our solar system some 4.6 billion years ago, Earth and other protoplanets were still taking shape, Sarafian explained. Within a certain distance from the sun, it was too hot for water to remain stable, and any vapor would have been blown out by solar winds. Beyond a distance far enough from the sun, called the “snow line,” water could exist in the form of ice. Encircling the inner edge of the snow line was a belt of asteroids that included a large one called Vesta. “It’s almost like a planet that didn’t fully form,” he said.
About 15 years ago, “scientists began thinking that maybe Earth’s water came from carbonaceous chondrites,” Sarafian said. These are a type of meteorite that contains lots of water. The hypothesis was that the orbit of the vast protoJupiter began migrating closer toward the sun. “Jupiter said, ‘Get out of my way’ and all these water-rich carbonaceous chondrites outside the snow line got flung toward the sun, and all the inner planets, Mercury, Venus, Earth, and Mars. They would slam into Vesta or even the Earth and get incorporated into rocks in the inner planets within the first 20 million years of solar system formation.”
So scientists began comparing Earth’s water with the water in carbonaceous chondrites. The key is hydrogen, the most abundant element in the universe. Hydrogen has two isotopes—normal hydrogen, with a mass of one, and deuterium or “heavy hydrogen,” with a mass of two. The ratio of these isotopes differs in different parts of the solar system. The sun is made mostly of normal hydrogen. But comets, made mostly of rock and ice, formed much farther from the sun and are richer in deuterium. The hydrogen in Earth’s water is somewhere in between the sun and comets.
Measurements of hydrogen isotopes in carbonaceous chondrites matched very well with Earth’s water. That gave credence to the idea that Earth’s water came from chondrites. But when did this occur? The problem was that chondrites could have brought in water early, slamming into the growing planet, or late, pelting Earth after it formed. To know, scientists needed to find water in rocks that formed very early on, in the same region and time as Earth.
A promising source was a type of rock called eucrites. These are pieces of the asteroid Vesta that have fallen to Earth in the form of meteorites.
“Vesta completely froze and locked up about 14 million years after the start of the solar system, so it got all its water before then,” Sarafian said. “At the time, the Earth was one-quarter to one-half its size and still growing.”
To pursue his quest, Sarafian needed to jump two obstacles: He needed to get rare samples of eucrites, and he needed to find a way to measure the water in them.
An appetite for apatites
To get eucrites, Sarafian petitioned institutions that collect meteorite samples, such as NASA, the Smithsonian Institution, and the American Museum of Natural History.
“It’s not that easy,” Marschall said. “You have to convince them that what you want to do is worth doing. He convinced them, as a student, without even the backing of an institution. I really appreciate Adam’s drive and motivation.”
Next came the measurement. Unlike chondrites, which are water-rich sedimentary rocks, Vesta and eucrites are made of basalt, much like the rock making up the seafloor.
Sarafian learned that WHOI geologist Nobu Shimizu had developed a technique to measure water trapped in glass pockets in basaltic seafloor rocks, using the Northeast National Ion Microprobe Facility at WHOI. Sarafian wanted to measure water in another mineral common in both seafloor rocks and meteorites: apatite. So he asked Shimizu and WHOI geologist Henry Dick if he could spend the summer at WHOI as a guest student working with them “to take the technique they already had and shape it toward measuring water in apatites.”
“A lot of people in the planetary field probably would have said, ‘You shouldn’t measure that—eucrites don’t have any water in them,’ ” Sarafian said. But for his master’s degree research at Georgia, he reported for the first time the presence of water in eucrites.
That feat inexorably led him to the next question: What is the source of the water? Which led to another high bar to hurdle: measuring hydrogen isotopes in extremely low concentrations of water.
Water, water everywhere
After his master’s degree, Sarafian naturally headed back to WHOI. While here, he met Marschall and another WHOI geologist, Sune Nielsen. They took him on as a guest student, for another summer and then a year, to continue his research while he applied to enter the MIT-WHOI Joint Program. The two are now Sarafian’s co-advisors for his Ph.D. research.
“We also have an awesome lab tech at the ion microprobe facility named Brian Monteleone,” Sarafian said, “and we began figuring out how we were going to do the measurements. Brian always says his favorite projects are where we’re pushing our machine to its very limits.”
There are two problems. First, “we’re measuring a minute amount of meteorite water, and we have to make sure we’re measuring nothing else. We’re constantly thinking that we do not want to be measuring any Earth water. And there’s water everywhere on Earth. We have to decontaminate the machine as best we can.”
They put the samples under a powerful vacuum for a week or two to suck away water. Then the samples go into the ion microprobe under ultrahigh-vacuum conditions that suck out virtually all air and water. Virtually all. The researchers still have to take meticulous measurements of extremely low concentrations of any residual hydrogen, calculating a baseline hydrogen standard in the machine and then subtracting it out of their final calculations.
The good news is that the mineral structure of apatite prevents Earthly water from diffusing in. So any water locked inside is meteoric. But rock surfaces can still have infinitesimal cracks that can trap infinitesimal amounts of terrestrial water.
“We polish the samples perfectly flat with the minimum of cracks possible, and that takes a lot of polishing,” he said.
Ready, aim, fire. Repeat.
The ion microprobe focuses a beam of ions on a very small area of a sample, about 10 microns wide by 10 microns long by 1 micron deep.
The beam sputters out ions from the sample, which are propelled through a mass spectrometer. It detects and distinguishes the ions based on their mass and charge—in this case, the ratio of normal to heavy hydrogen ions.
“We specifically analyze the cracks also, to know how much water might be in them and what its isotopic ratio is,” he said. “So it’s a lot of focusing, aligning, and re-running our standards, and if the beam is off by a little bit, it’s trouble. We’re running a lot of standards and running a lot of cracks. And each crack that we run takes an hour. Each standard we run is an hour, and every once in a while we get a data point. It’s painstaking, and we have to throw out quite a few analyses because we don’t think they are rigorous enough.”
In the end, the hydrogen isotope ratio in the eucrites looked just like Earth’s. “This means the water in the very early solar system, when eucrites were formed, was just like the water on Earth today.”
The study, published October 2014 in the prestigious
journal Science, “shows that Earth’s water most likely
accreted at the same time as the rock forming the planet,” Marschall said. “The planet formed as a wet planet with water on the surface.”
“The answer is that our oceans were always here,” Sarafian said.
Reading and writing
Sarafian was lead author of the Science paper, with co-authors Nielsen, Marschall, Monteleone, and Francis McCubbin of the University of New Mexico Institute of Meteoritics. That made him recall his college days when reading a scientific paper was still a travail.
“Once I started focusing on geology, I said, ‘I really need to be able to read.’ There was a lot of re-reading papers, highlighting, notating on the side—hours and hours and hours of that. At first I just looked at the figures and the captions. I looked up a lot of words.
“I locked myself in my room or my office and just stayed up long hours rereading papers. I had a sleeping bag and a toaster oven in the office, and I was there quite a bit. I viewed that as me catching up to everybody else, because I felt so behind.
“It took a considerable amount of time and a lot of people helping to be able to read a scientific paper and get anything out of it. Eventually, I could read scientific papers quickly and thoroughly to get all the information out. But I still can’t really read fiction at all. I guess I am unwilling to put that much time into fiction.”
History Of The Ocean ~ MarineBio Conservation Society
When the Earth formed about 4.5 billion years ago...
The ocean is not just where the land happens to be covered by water. The sea floor is geologically distinct from the continents. It is locked in a perpetual cycle of birth and destruction that shapes the ocean and controls much of the geology and geological history of the continents.
Geological processes that occur beneath the waters of the sea affect not only marine life, but dry land as well. The processes that mold ocean basins occur slowly, over tens and hundreds of millions of years. On this timescale, where a human lifetime is but the blink of an eye, solid rocks flow like liquid, entire continents move across the face of the earth and mountains grow from flat plains. To understand the sea floor, we must learn to adopt the unfamiliar point of view of geological time. Geology is very important to marine biology. Habitats, or the places where organisms live, are directly shaped by geological processes. The form of coastlines; the depth of the water; whether the bottom is muddy, sandy, or rocky; and many other features of a marine habitat are determined by this geology. The geologic history of life is also called Paleontology.
The presence of large amounts of liquid water makes our planet unique. Most other planets have very little water, and on those that do, the water exists only as perpetually frozen ice or as vapor in the atmosphere. The earth, on the other hand, is very much a water planet. The ocean covers most of the globe and plays a crucial role in regulating our climate and atmosphere. Without water, life itself would be impossible.
Our ocean covers 72% of the earth’s surface. It is not distributed equally with respect to the Equator. About two-thirds of the earth’s land area is found in the Northern Hemisphere, which is only 61% ocean. About 80% of the Southern Hemisphere is ocean.
The ocean is traditionally classified into four large basins. The Pacific is the deepest and largest, almost as large as all the others combined. The Atlantic “Ocean” is a little larger than the Indian “Ocean”, but the two are similar in average depth. The Arctic is the smallest and shallowest. Connected or marginal to the main ocean basins are various shallow seas, such as the Mediterranean Sea, the Gulf of Mexico and the South China Sea.
Though we usually treat the oceans as four separate entities, they are actually interconnected. This can be seen most easily by looking at a map of the world as seen from the South Pole. From this view it is clear that the Pacific, the Atlantic and Indian oceans are large branches of one vast ocean system. The connections among the major basins allow seawater, materials, and some organisms to move from one “ocean” to another. Because the “oceans” are actually one great interconnected system, oceanographers often speak of a single world ocean. They also refer to the continuous body of water that surrounds Antarctic as the Southern Ocean.
The earth and the rest of the solar system are thought to have originated about 4.5 billion years ago from a cloud or clouds of dust. This dust was debris remaining from a huge cosmic explosion called the big bang, which astrophysicists estimate occurred about 15 billion years ago. The dust particles collided with each other, merging into larger particles. These larger particles collided in turn, joining into pebble-sized rocks that collided to form larger rocks, and so on. The process continued, eventually building up the earth and other planets.
So much heat was produced as the early earth formed that the planet was probably molten. This allowed materials to settle within the planet according to their density. Density is the weight, or more correctly, the mass, of a given volume of a substance. Obviously, a pound of styrofoam weighs more than an ounce of lead, but most people think of lead as “heavier” than styrofoam. This is because lead weighs more than styrofoam if equal volumes of the two are compared. In other words, lead is denser than styrofoam. The density of a substance is calculated by dividing its mass by its volume. If two substances are mixed, the denser material will tend to sink and the less dense will float.
During the time that the young earth was molten, the densest material tended to flow toward the center of the planet, while lighter materials floated toward the surface. The light surface material cooled to make a thin crust. Eventually, the atmosphere and oceans began to form. If the earth had settled into orbit only slightly closer to the sun, the planet would have been so hot that all the water would have evaporated into the atmosphere. With an orbit only slightly farther from the sun, all the water would be perpetually frozen. Fortunately for us, our planet orbits the sun in a narrow zone in which liquid water can exist. Without liquid water, there would be no life on earth.
The earth is composed of three main layers: the iron-rich core, the semiplastic mantle and the thin outer crust. The crust is the most familiar layer of earth. Compared to the deeper layers it is extremely thin, like a rigid skin floating on top of the mantle. The composition and characteristics of the crust differs greatly between the oceans and the continents.
The geological distinction between ocean and continents is caused by the physical and chemical differences in the rocks themselves, rather than whether or not the rocks happen to be covered with water. The part of earth covered with water, the ocean, is covered because of the nature of the underlying rock.
Oceanic crustal rocks, which make up the sea floor, consists of minerals collectively called basalt that have a dark color. Most continental rocks are of general type called granite, which has a different mineral composition than basalt and is generally lighter in color. Ocean crust is denser than continental crust, though both are less dense than the underlying mantle. The continents can be thought of as thick blocks of crust “floating” on the mantle, much as icebergs float on water. Oceanic crust floats on the mantle too, but because it is denser it doesn’t float as high as continental crust. This is why the continents lie high and dry above sea level and oceanic crust lies below sea level and is covered by water. Oceanic crust and continental crust also differ in geological age. The oldest oceanic crust is less 200 million years old, quite young by geological standards. Continental rocks, on the other hand, can be very old, as old as 3.8 billion years…!
In the years after World War II, sonar allowed the first detailed surveys of large areas of the sea floor. These surveys resulted in the discovery of the mid-oceanic ridge system, a 40,000 mile continuous chain of volcanic submarine mountains and valleys that encircle the globe like the seams of a baseball. The mid-oceanic ridge system is the largest geological feature on the planet. At regular intervals the mid-ocean ridge is displaced to one side or the other by cracks in the earth’s crust known as transform faults. Occasionally the submarine mountains of the ridge rise so high that they break the surface to form islands, such as Iceland and the Azores.
The portion of the mid-ocean ridge in the Atlantic, known as the Mid-Atlantic Ridge, runs right down the center of the Atlantic Ocean, closely following the curves of the opposing coastlines. The ridge forms an inverted Y in the Indian Ocean and runs up the eastern side of the Pacific. The main section of ridge in the eastern Pacific is called the East Pacific Rise. Surveys also revealed the existence of a system of deep depressions in the sea floor called trenches. Trenches are especially common in the Pacific.
When the mid-ocean ridge system and trenches were discovered, geologists wanted to know how they were formed and began intensively studying them. They found that there’s a great deal of geological activity around these features. Earthquakes are clustered at the ridges, for example, and volcanoes are especially common near trenches. The characteristics of sea floor rocks are also related to the mid-oceanic ridges. Beginning in 1968, a deep-sea drilling ship, the Glomar Challenger, obtained samples of the actual sea floor rock. It was found that the farther rocks are from the ridge crest the older they are. One of the most important findings came from the studying the magnetism of rocks on the sea floor. Bands of rock alternating between normal and reversed magnetism parallel the ridge.
It was the discovery of the magnetic anomalies on the sea floor, together with other evidence, that finally led to an understanding of plate tectonics. The earth surface is broken up into a number of plates. These plates, composed of the crust and the top parts of the mantle, make up the lithosphere. The plates are about 100 km thick. As new lithosphere is created, old lithosphere is destroyed somewhere else. Otherwise, the earth would have to constantly expand to make room for the new lithosphere. Lithosphere is destroyed at the trenches. A trench is formed when two plates collide and one plate dips below the other and slides back down in to the mantle. This downwards movement of the plate into the mantle is called subduction. Because subduction occurs at the trenches, trenches are often called subduction zones. Subduction is the process that produces earthquakes and volcanoes, also underwater. The volcanoes may rise from the sea floor to create chains of volcanic islands.
We now realize that the earth’s surface has undergone dramatic alterations. The continents have been carried long distances by the moving sea floor, and the ocean basins have changed in size and shape. In fact, new oceans have been born. Knowledge of the process of plate tectonics has allowed scientists to reconstruct much of the history of these changes. Scientists have discovered, for example, that the continents were once united in a single supercontinent called Pangaea that began to break up about 180 million years ago. The continents have since moved to their present position.
The characteristics of seawater are due both to the nature of pure water and to the materials dissolved in it. The solids dissolved in seawater come from two main sources. Some are produced by the chemical weathering of rocks on land and are carried to sea by rivers. Other materials come from the earth’s interior. Most of these are released into the ocean at hydrothermal vents. Some are released into the atmosphere from volcanoes and enter the ocean in rain and snow. Seawater contains at least a little of almost everything, but most of the solutes or dissolved materials, are made up of a surprisingly small group of ions. In fact, only six ions compose over 98% of the solids in seawater. Sodium and chloride account for about 85% of the solids, which is why seawater tastes like table salt. The salinity of the water strongly affects the organisms that live in it. Most marine organisms, for instance, will die in fresh water. Even slight changes in salinity will harm some organisms.
Marine Biology, Peter Castro, Ph.D. and Michael E. Huber, Ph.D., Part one.
A Natural History of the Oceans (BBC)
Also know as the “Dymaxion Map,” the Fuller Projection Map is the only flat map of the entire surface of the Earth which reveals our planet as one island in one ocean, without any visually obvious distortion of the relative shapes and sizes of the land areas, and without splitting any continents. It was developed by R. Buckminster Fuller who “By 1954, after working on the map for several decades,” finally realized a “satisfactory deck plan of the six and one half sextillion tons Spaceship Earth.”
Traditional world maps reinforce the elements that separate humanity and fail to highlight the patterns and relationships emerging from the ever evolving and accelerating process of globalization. Instead of serving as “a precise means for seeing the world from the dynamic, cosmic and comprehensive viewpoint,” the maps we use still cause humanity to “appear inherently disassociated, remote, self-interestedly preoccupied with the political concept of its got to be you or me; there is not enough for both.”
All flat world map representations of the spherical globe contain some amount of distortion either in shape, area, distance or direction measurements. On the well-known Mercator world map, Greenland appears to be three times its relative globe size and Antarctica appears as a long thin white strip along the bottom edge of the map. Even the popular Robinson Projection, now used in many schools, still contains a large amount of area distortion with Greenland appearing 60 percent larger than its relative globe size.
Fuller’s view was that given a way to visualize the whole planet with greater accuracy, we humans will be better equipped to address challenges as we face our common future aboard Spaceship Earth.
An ocean is a large area of water between continents. Oceans are very big and they join smaller seas together. Oceans (or marine biomes) cover 72% of Earth. There are five main oceans together. They are: 1. Pacific Ocean 2. Atlantic Ocean 3. Indian Ocean 4. Southern Ocean 5. Arctic Ocean The largest ocean is the Pacific Ocean. The smallest ocean is the Arctic Ocean. Many types of animals live in oceans, such as carp, crabs, starfish, sharks, and whales. Different water movements separate the Southern Ocean from the Atlantic, Pacific and Indian Oceans. The Southern Ocean is also called the Antarctic Ocean, because it covers the area around Antarctica.
The deepest ocean is the Pacific Ocean. The deep ocean is characterised by cold temperatures, high pressure, and complete darkness. Some very unusual organisms live in this part of the ocean. They do not require energy from the sun to survive, because they use chemicals from deep inside the Earth.
Although many people believe that the oceans are blue because the water reflects the blue sky, this is actually not true. Water has a very slight blue color that can only be seen when there is a lot of water. However, the main cause of the blue or blue/green color of the oceans is that water absorbs the red part of the incoming light, and reflects the green and blue part of the light. We then see the reflected light as the color of water.
Plants and animals
Many organisms live in oceans. Organisms that live in oceans can live in salt water. They are affected by sunlight, temperature, water pressure, and water movement. Different ocean organisms live near the surface, in shallow waters, and in deep waters. Small plant organisms that live near the surface and use sunlight to produce food are called phytoplankton. Almost all animals in the ocean depend directly or indirectly on these plants. In shallow water, you may find lobsters and crabs. In deeper water, marine animals of many different shapes and sizes swim through the ocean. These include many types of fish, such as tuna, swordfish and marine mammals like dolphins and whales. The skies above the open ocean are home to large sea birds, such as the albatross.
Harvesting the ocean
Nations like Russia and Japan have lots of huge ships that go to some of the world’s best fishing areas for many months. These large ships have libraries, hospitals, schools, repair (fixing) shops and other things that are needed for fishermen and their families.
Many people look at the sea as a source of food, minerals and energy.
According to the FishBase.org website, there are 33,200 known species of fish, and many of them live in the oceans Many of these fish are a fine source of protein, so many people eat them. Fishing industries are very important because they make jobs and give food to millions of people. Today, usually through ocean fishing, the ocean supplies about 2% of the calories needed by people. Tuna, anchovies, and herring are harvested close to the surface of the ocean. Pollock, flounder and cod are caught near the ocean floor. More than a million tons of herring are caught every year in the North Pacific and North Atlantic, and almost eight fish out of ten fish are eaten as food for humans. The other fish are used as fertilizer, glue, and pet and other animal food.
There are many different ocean temperatures in the open ocean, both vertically (from top to bottom) and horizontally. Icebergs are made over very cold waters at either pole, while waters at the equator are pretty warm. Water cools and warms more slowly than land does, so land influenced by the ocean has later and milder seasons than land that is farther away from the ocean.
The surface part of the ocean, also called the mixed layer, is not much colder even when we go deeper down. Below this surface zone is a layer of sudden temperature difference, called a thermocline. This is a middle layer hat is from the surface zone down to about 2,600 feet (800 m). Thermoclines may happen only at seasons or permanently, and may change depending on where and how deep it is. As evaporation happens, it begins cooling, and if the water evaporates very quickly, the water becomes saltier. The salty, cold water is denser, so it sinks. This is why warm and cold waters do not easily mix. Most animals and plants live in the warm upper layer. Below the thermocline, temperature in the deep zone is so cold it is just above freezing – between 32–37.4 °F (0–3 °C).
The debate is over: The oceans are in hot, hot water
More than any other region on Earth, the oceans hold the answers for our planet’s future. And right now, their health is spectacularly failing.
The Earth’s surface is 70 percent water, but even that underestimates how vital ocean health is to our planet’s ability to maintain life. Recent results from scientists around the world only further confirm that our waterworld is in serious danger.
Last week, a bombshell study confirmed that the oceans are warming 40 percent faster than many scientists had previously estimated. The finding partially resolved a long-running debate between climate modelers and oceanographers. By measuring the oceans more directly, scientists again came to a now-familiar conclusion: Yes, things really are as bad as we feared.
The ocean stores more than 90 percent of all excess heat energy due to the buildup of greenhouse gases in the atmosphere. From the standpoint of heat, global warming is almost entirely a story of how rapidly the oceans are changing.
Warming oceans work to melt polar ice, of course, thereby raising sea levels. But hotter oceans change how the atmosphere works, too. More heat energy in the oceans means more heat energy is available for extreme weather: Downpours of rainfall are happening more often, hurricanes are shifting in frequency and growing in intensity, freak ocean heat waves are spilling over into temperature records on land. Melting Arctic and Antarctic sea ice is also increasing wave height, which is accelerating coastal erosion — worsening the effects of sea-level rise.
The now-inevitable loss of nearly all coral reefs — home to a quarter of the ocean’s biodiversity — is the most charismatic of the impacts. The changes to the world’s oceans are shifting marine ecosystems on a grand scale, all the way down to phytoplankton, the base of the planet’s food web.
Last month, a study found that the “Great Dying,” the worst mass extinction in Earth history, was triggered by a period of global warming comparable to what’s predicted for us under business-as-usual conditions. The study asked: Could we be on a similar path as 252 million years ago, when most marine life was snuffed out after the warming seas lost most of their oxygen?
The answer, almost entirely, comes down to what we collectively decide to do in the next decade or so.
CO2 sticks around in the atmosphere for about 100 years. The lag time of ocean heating — the amount of time it takes for the energy of a particularly warm day at the sea’s surface to reach all the way to its deepest depths — is about 2,000 years. Oceans act as a massive storage system to retain that heat over very long timescales.
It’s why, if we’re going to limit warming to less than 1.5 degrees C (2.7 degrees F), the IPCC says that not only do we need to cut emissions immediately — with a 50 percent reduction globally by 2030 — but we also need to work to draw down the greenhouse gases that are already in the atmosphere, through massive reforestation and other means. We simply don’t have time to wait for them to dwindle on their own.
By changing the atmosphere to capture more of the sun’s energy, we’re adding the equivalent of four Hiroshima bombs of heat energy every second to the oceans. In 2018, the oceans gained about 9 zettajoules of heat energy. (For reference, annual energy use for all of human civilization is about 0.5 zettajoules.) There’s just no way to remove that heat once it’s there. It will inevitably end up leaking into the atmosphere, intensifying our experience of a warming planet even further.
Even if a future human civilization decided to embark on a geoengineering project to offset the atmospheric effects of climate change, there is no practical physical mechanism to cool down the 325 million cubic miles of ocean water on the planet.
Combined with other stressors like overfishing, acidification, plastic pollution, and nutrient runoff, the oceans are already experiencing geological-scale changes. This is the grandest of possible wake-up calls: We are in the emergency phase of climate change. In order for things to get back on track and avoid further radical changes to our planetary life-support system, we have to make radical changes to our culture and society.
In a remote region of Antarctica known as Pine Island Bay, 2,500 miles from the tip of South America, two glaciers hold human civilization hostage.
Stretching across a frozen plain more than 150 miles long, these glaciers, named Pine Island and Thwaites, have marched steadily for millennia toward the Amundsen Sea, part of the vast Southern Ocean. Further inland, the glaciers widen into a two-mile-thick reserve of ice covering an area the size of Texas.
There’s no doubt this ice will melt as the world warms. The vital question is when.
The glaciers of Pine Island Bay are two of the largest and fastest-melting in Antarctica. (A Rolling Stone feature earlier this year dubbed Thwaites “The Doomsday Glacier.”) Together, they act as a plug holding back enough ice to pour 11 feet of sea-level rise into the world’s oceans — an amount that would submerge every coastal city on the planet. For that reason, finding out how fast these glaciers will collapse is one of the most important scientific questions in the world today.
To figure that out, scientists have been looking back to the end of the last ice age, about 11,000 years ago, when global temperatures stood at roughly their current levels. The bad news? There’s growing evidence that the Pine Island Bay glaciers collapsed rapidly back then, flooding the world’s coastlines — partially the result of something called “marine ice-cliff instability.”
The ocean floor gets deeper toward the center of this part of Antarctica, so each new iceberg that breaks away exposes taller and taller cliffs. Ice gets so heavy that these taller cliffs can’t support their own weight. Once they start to crumble, the destruction would be unstoppable.
“Ice is only so strong, so it will collapse if these cliffs reach a certain height,” explains Kristin Poinar, a glaciologist at NASA’s Goddard Space Flight Center. “We need to know how fast it’s going to happen.”
In the past few years, scientists have identified marine ice-cliff instability as a feedback loop that could kickstart the disintegration of the entire West Antarctic ice sheet this century — much more quickly than previously thought.
Minute-by-minute, huge skyscraper-sized shards of ice cliffs would crumble into the sea, as tall as the Statue of Liberty and as deep underwater as the height of the Empire State Building. The result: a global catastrophe the likes of which we’ve never seen.
Ice comes in many forms, with different consequences when it melts. Floating ice, like the kind that covers the Arctic Ocean in wintertime and comprises ice shelves, doesn’t raise sea levels. (Think of a melting ice cube, which won’t cause a drink to spill over.)
Land-based ice, on the other hand, is much more troublesome. When it falls into the ocean, it adds to the overall volume of liquid in the seas. Thus, sea-level rise.
Antarctica is a giant landmass — about half the size of Africa — and the ice that covers it averages more than a mile thick. Before human burning of fossil fuels triggered global warming, the continent’s ice was in relative balance: The snows in the interior of the continent roughly matched the icebergs that broke away from glaciers at its edges.
Now, as carbon dioxide traps more heat in the atmosphere and warms the planet, the scales have tipped.
A wholesale collapse of Pine Island and Thwaites would set off a catastrophe. Giant icebergs would stream away from Antarctica like a parade of frozen soldiers. All over the world, high tides would creep higher, slowly burying every shoreline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees.
All this could play out in a mere 20 to 50 years — much too quickly for humanity to adapt.
“With marine ice cliff instability, sea-level rise for the next century is potentially much larger than we thought it might be five or 10 years ago,” Poinar says.
A lot of this newfound concern is driven by the research of two climatologists: Rob DeConto at the University of Massachusetts-Amherst and David Pollard at Penn State University. A study they published last year was the first to incorporate the latest understanding of marine ice-cliff instability into a continent-scale model of Antarctica.
Their results drove estimates for how high the seas could rise this century sharply higher. “Antarctic model raises prospect of unstoppable ice collapse,” read the headline in the scientific journal Nature, a publication not known for hyperbole.
Instead of a three-foot increase in ocean levels by the end of the century, six feet was more likely, according to DeConto and Pollard’s findings. But if carbon emissions continue to track on something resembling a worst-case scenario, the full 11 feet of ice locked in West Antarctica might be freed up, their study showed.
Three feet of sea-level rise would be bad, leading to more frequent flooding of U.S. cities such as New Orleans, Houston, New York, and Miami. Pacific Island nations, like the Marshall Islands, would lose most of their territory. Unfortunately, it now seems like three feet is possible only under the rosiest of scenarios.
At six feet, though, around 12 million people in the United States would be displaced, and the world’s most vulnerable megacities, like Shanghai, Mumbai, and Ho Chi Minh City, could be wiped off the map.
At 11 feet, land currently inhabited by hundreds of millions of people worldwide would wind up underwater. South Florida would be largely uninhabitable; floods on the scale of Hurricane Sandy would strike twice a month in New York and New Jersey, as the tug of the moon alone would be enough to send tidewaters into homes and buildings.
DeConto and Pollard’s breakthrough came from trying to match observations of ancient sea levels at shorelines around the world with current ice sheet behavior.
Around 3 million years ago, when global temperatures were about as warm as they’re expected to be later this century, oceans were dozens of feet higher than today.
Previous models suggested that it would take hundreds or thousands of years for sea-level rise of that magnitude to occur. But once they accounted for marine ice-cliff instability, DeConto and Pollard’s model pointed toward a catastrophe if the world maintains a “business as usual” path — meaning we don’t dramatically reduce carbon emissions.
Rapid cuts in greenhouse gases, however, showed Antarctica remaining almost completely intact for hundreds of years.
Pollard and DeConto are the first to admit that their model is still crude, but its results have pushed the entire scientific community into emergency mode.
“It could happen faster or slower, I don’t think we really know yet,” says Jeremy Bassis, a leading ice sheet scientist at the University of Michigan. “But it’s within the realm of possibility, and that’s kind of a scary thing.”
Scientists used to think that ice sheets could take millennia to respond to changing climates. These are, after all, mile-thick chunks of ice.
The new evidence, though, says that once a certain temperature threshold is reached, ice shelves of glaciers that extend into the sea, like those near Pine Island Bay, will begin to melt from both above and below, weakening their structure and hastening their demise, and paving the way for ice-cliff instability to kick in.
In a new study out last month in the journal Nature, a team of scientists from Cambridge and Sweden point to evidence from thousands of scratches left by ancient icebergs on the ocean floor, indicating that Pine Island’s glaciers shattered in a relatively short amount of time at the end of the last ice age.
The only place in the world where you can see ice-cliff instability in action today is at Jakobshavn glacier in Greenland, one of the fastest-collapsing glaciers in the world. DeConto says that to construct their model, they took the collapse rate of Jakobshavn, cut it in half to be extra conservative, then applied it to Thwaites and Pine Island.
But there’s reason to think Thwaites and Pine Island could go even faster than Jakobshavn.
Right now, there’s a floating ice shelf protecting the two glaciers, helping to hold back the flow of ice into the sea. But recent examples from other regions, like the rapidly collapsing Larsen B ice shelf on the Antarctic Peninsula, show that once ice shelves break apart as a result of warming, their parent glaciers start to flow faster toward the sea, an effect that can weaken the stability of ice further inland, too.
“If you remove the ice shelf, there’s a potential that not just ice-cliff instabilities will start occurring, but a process called marine ice-sheet instabilities,” says Matthew Wise, a polar scientist at the University of Cambridge.
This signals the possible rapid destabilization of the entire West Antarctic ice sheet in this century. “Once the stresses exceed the strength of the ice,” Wise says, “it just falls off.”
And, it’s not just Pine Island Bay. On our current course, other glaciers around Antarctica will be similarly vulnerable. And then there’s Greenland, which could contribute as much as 20 feet of sea-level rise if it melts.
Next to a meteor strike, rapid sea-level rise from collapsing ice cliffs is one of the quickest ways our world can remake itself. This is about as fast as climate change gets.
Still, some scientists aren’t fully convinced the alarm is warranted. Ted Scambos, lead scientist at the National Snow and Ice Data Center in Colorado, says the new research by Wise and his colleagues, which identified ice-cliff instabilities in Pine Island Bay 11,000 years ago, is “tantalizing evidence.” But he says that research doesn’t establish how quickly it happened.
“There’s a whole lot more to understand if we’re going to use this mechanism to predict how far Thwaites glacier and the other glaciers are going to retreat,” he says. “The question boils down to, what are the brakes on this process?”
Scambos thinks it is unlikely that Thwaites or Pine Island would collapse all at once. For one thing, if rapid collapse did happen, it would produce a pile of icebergs that could act like a temporary ice shelf, slowing down the rate of retreat.
Despite the differences of opinion, however, there’s growing agreement within the scientific community that we need to do much more to determine the risk of rapid sea-level rise. In 2015, the U.S. and U.K. governments began to plan a rare and urgent joint research program to study Thwaites glacier. Called “How much, how fast?,” the effort is set to begin early next year and run for five years.
Seeing the two governments pooling their resources is “really a sign of the importance of research like this,” NASA’s Poinar says.
Given what’s at stake, the research program at Thwaites isn’t enough, but it might be the most researchers can get. “Realistically, it’s probably all that can be done in the next five years in the current funding environment,” says Pollard.
He’s referring, of course, to the Trump administration’s disregard for science and adequate scientific funding; the White House’s 2018 budget proposal includes the first-ever cut to the National Science Foundation, which typically funds research in Antarctica.
“It would be sensible to put a huge effort into this, from my perspective,” Pollard says. Structural engineers need to study Antarctica’s key glaciers as though they were analyzing a building, he says, probing for weak spots and understanding how exactly they might fail. “If you vastly increase the research now, [the cost] would still be trivial compared to the losses that might happen.”
Bassis, the ice sheet scientist at the University of Michigan, first described the theoretical process of marine ice-cliff instability in research published only a few years ago.
He’s 40 years old, but his field has already changed enormously over the course of his career. In 2002, when Bassis was conducting his PhD research in a different region of Antarctica, he was shocked to return to his base camp and learn that the Larsen B ice shelf had vanished practically overnight.
“Every revision to our understanding has said that ice sheets can change faster than we thought,” he says. “We didn’t predict that Pine Island was going to retreat, we didn’t predict that Larsen B was going to disintegrate. We tend to look at these things after they’ve happened.”
There’s a recurring theme throughout these scientists’ findings in Antarctica: What we do now will determine how quickly Pine Island and Thwaites collapse. A fast transition away from fossil fuels in the next few decades could be enough to put off rapid sea-level rise for centuries. That’s a decision worth countless trillions of dollars and millions of lives.