Sea level rise has something to do with seawater expansion? Scientists: The future rising limit may reach 55 meters

2020-01-07 | Theory of Quantum Science original |

The ocean not only breeds hundreds of millions of lives, but also brings us beautiful beaches. Maybe your favorite time to go to the seaside on weekends, the waves beating against the shore, the sun shining on the sea, and there are wavesThe sea breeze coming.

But currently your favorite beach is slowly disappearing. Because the sea level is rising, the coastline will move hundreds of kilometers inland, flooding the previous coastline.

Climate change scientists believe that there is overwhelming evidence that sea levels are indeed rising, and that the rate of rise is fast. So how high will sea levels rise if they continue to do so? Coastal areas will pay for thisWhat is the price?

Cause of sea level rise, is there any factor of thermal expansion

1941: Geophysicist Beno Gutenberg analyzed data from a tide gauge an instrument that measures sea levels along the coastline and found some strange phenomena. For about 100 years,Sea level has been rising.

Tide measurement data was always considered unreliable at that time, and people did not believe that the water in the ocean would increase, but in 1993, NASA and the French Space Agency launched spaceborne radar altimeters into space. Therefore, we are nowGlobal sea level data has been more accurately understood. Satellite observations have confirmed that sea level is indeed rising.

And now we know that climate warming is the culprit behind this change. For example, simple physics tells us that when water warms, it swells. In the past century, seawater occurred due to warming.Thermal expansion is one of the biggest causes of global sea level rise.

This thermal expansion will continue in the future, but there is another more serious problem that may cause real dramatic changes in sea levels in the future: global temperatures will rise, and the melting of world glaciers and ice sheets will be released to the oceanA lot of single water.

Past sea level changes

One way to answer this question is to study changes in past sea levels. At present, our best estimate of the mid-Pliocene beginning 5.3 million years ago and ending 2.588 million years ago is 10 to 40 meters..

Geologists can determine the location of past coastlines by observing sedimentary rocks, and effectively look for fossil beaches, thereby telling us the height of the ocean at that time. Scientists have studied the ancient biological shells found in marine sediments and salt marshes.Clues about past sea levels. The middle Pliocene is an ancient period of particular interest, about 3 million years ago. It is estimated that the global temperature of the Pliocene was 2 to 3 degrees Celsius higher than before industrialization, and 1 to 2 degrees higher than it is now.2 degrees Celsius.

Scientists' most accurate estimate of sea level in the middle Pliocene is 10 to 40 meters higher than it is now. That is, geological records indicate that global warming will cause sea levels to rise significantly.

Back to the present. We should not only worry about the magnitude of sea level change, but the speed of change. A study published in March 2016 found that sea level rise in the 20th century is faster than any in the past 27 centuries.Fast for a century.

This study is unique in that scientists have combined statistics and high-precision sea-level record data developed over the past decade to form the first high-precision global sea-level database in nearly 3000 years.

This record shows that there is a 95% probability that sea levels have been rising at least since 800 BC or 2800 years ago. But in the past 20 years, the rate of global sea level rise was 20th centuryMore than twice.

by 2100, global sea level may rise by 2 meters

We currently know that the earth is experiencing unprecedented sea level rise. However, this study does not tell us how high sea levels will rise in the future. This information is vital if we want to plan defenses along the coast.

Another paper published at the same time examined the second issue. Researchers predicted the rise in sea level. If greenhouse gas emissions do not decrease rapidly, global sea levels are expected to rise by 50% by the end of this century.Up to 130 cm.

These data are also in line with the United Nations Climate Change Commission ’s forecast that sea levels will rise by 50 to 100 cm by 2100.

These predictions have a certain range, because many different emission scenarios are used in the calculations, and there is great uncertainty about when and how quickly the ice sheet will melt.

A study published in March 2016 also showed that this uncertainty is very large. Two researchers considered how climate warming can damage the ice cliffs around Antarctica and accelerate the speed of glaciers loss. They said that hereIn the process, by the end of this century, Antarctica alone will contribute up to 1 meter to sea level rise, which means that by 2100, global sea level will rise by about 2 meters in total.

Sea level rise of 2 meters does not sound much. Compared with the Pliocene, sea level at that time was considered to be 40 meters higher than the present. The reason for this difference is due to the difference in reviewing the past and predicting the future.Certainty.

So far, thermal expansion and melting of high mountains and glaciers have been the main causes of sea level rise. In the future, the melting of Greenland and Antarctic ice will play an increasing role, but these changes may change over the centuries.Time scale.

So how high can sea levels be in the future?

Theoretically, if all the ice on the earth has melted, the sea level will rise by about 55 meters. But this will not happen in the short term.

The last time this happened about 40 million years ago on Earth. According to the latest research, the carbon dioxide content in the atmosphere at that time may be as high as 1000 parts per million. At present, the carbon dioxide concentration is just over 400ppm.

However, even if the highest rise in sea level rise at the end of this century will not exceed the global average of 2 meters, it will be enough to flood many low-lying coastal areas, increase the risk of floods, and displace millions of people, except in these areas.Place builds expensive seawall.

Besides that, it is also important to note that local sea level changes may deviate from the global average, so sea levels in some places will be higher.

A paper published in 2016 illustrates this regional difference, which found that sea level rises between the Atlantic and Pacific Oceans differ in degree. Atlantic sea level rises faster than the Pacific Ocean. Therefore, Atlantic townsAffected by rising sea levels will be greater than Pacific Coast towns.

Can we slow down sea level rise? Can we pump seawater to the center of Antarctica and freeze it?

Theoretically yes, but only if countries and individuals around the world start to take action. In order to slow sea level rise, we need to stop the temperature rise, which means we need to gradually stop using carbon-emitting energy technologies.

Most scientists think that this is our only feasible option. However, there are other ideas. One of them is to pump seawater from the ocean to Antarctica and freeze it for storage again.

Can we pump seawater to the center of Antarctica and freeze it?

In a study published in March 2016, scientists studied this weird geoengineering. They found that the pumped water would freeze into solid ice as expected, but the weight it adds to the Antarctic ice sheet may beAccelerates the flow of ice into the ocean.

And to store this water in the form of ice for a thousand years, it needs to exceed one tenth of the current annual global energy supply to balance the current rate of sea level rise. Therefore, this is not a feasible solution.

If we continue to discharge in large quantities as usual, even storing water in Antarctica will not be enough to limit long-term sea level rise.

So, whatever happens, reducing greenhouse gas emissions is crucial if sea level rise is to be controlled. In addition, substantial investment in local coastal protection is required.

If we gradually abandon coastal areas in the future, it will lead to a large number of people being displaced, because 44% of the world's population lives within 150 kilometers from the coast.

Earth has also flooded the coastline in large areas

At the end of the last Ice Age, humans also faced a similar situation. We know that Britain used to be connected to the European continent, but it was not until the rise of sea levels that it drowned human settlements: Douglas.

In the last Ice Age, 20,000 years ago, the sea level was about 120 meters lower than it is now, when a lot of seawater was locked in glaciers and ice sheets.

As the ice melts, sea levels rise rapidly again. Until about 8,000 years ago, sea levels began to stabilize. By then, the coastlines in some places had receded by more than 100 kilometers.

In Australian Aboriginal culture, there are many legends about floods from that era. They tell about submerged coastlines and lost hunting grounds.

Not far from the British coast, there is a lost world that was once home to thousands of Stone Age settlers. Dougland is a low-lying area that is now located below the North Sea and the English Channel.

Anthropogenic climate change and the resulting rise in sea level are changing our coastline again. The impact will be felt by future generations.


Special statement

This article is uploaded and published by the media, authors, etc. on Baidu Know Daily. It only represents the author ’s point of view, and does not mean that Baidu knows the views or positions of the daily newspaper. It is known that the daily newspaper only provides an information publishing platform. For cooperation and contributions, please contact zdribao@baidu.com.

+1 Like it Like

Follow the author

Theory of Quantum Science
A piece of cosmic dust

I know the daily hot articles

www.knowledge-daily.com e-mail: k@knowledge-daily.com