The corals reveal: the sea will rise, and quickly

Sea level rise may sound like something we have a lot of time to prepare for, as it will happen gradually over years. But coral fossils reveal that a sharp rise in sea level likely occurred all at once

By Maya Falah, Angle, Science and Environment News Agency

New York is flooded, Amsterdam is submerged under water and entire islands in oceans disappear as if they were not there. Estimates from the last year and a half warn that the sea level is rising as a result of global warming will happen sooner than was estimated until recently, and will be sharper: an increase of several meters even before the end of this century.

study New A recent publication reinforces these estimates. Researchers from Rice University in Houston, Texas discovered that the last time a significant rise in sea level occurred, it did not happen gradually - but in a series of sharp increases that occurred over a short period of several decades. This happened the last time the Earth warmed, with the end of the last ice age, about 20 years ago. And those who helped the researchers discover this figure were, surprisingly, actually corals that died tens of thousands of years ago.

Coral grows tall

So why, in fact, should we care what happened 20 thousand years ago? Well, understanding the patterns of sea level rise in the past can help us understand today what we are facing, and prepare accordingly. At the end of the last ice age, with the warming of the earth's temperature, a massive melting of ice occurred in the glaciers and poles, which caused a significant rise in sea level. Even today, due to climate change, a similar mass is occurring at an increasing rate. And so, the same scenario that the researchers learned from the ancient corals could indicate what will happen to the sea surface nowadays, as the Earth continues to warm.

Most of the corals that build coral reefs need sunlight to survive, because they live in partnership with microscopic algae that grow inside the coral tissue and provide it with much of the energy it needs to grow and build its calcareous skeleton. Those algae need sunlight to sustain the photosynthesis process, therefore most types of corals can only exist at depths where sunlight penetrates, that is, at a depth of up to several tens of meters below sea level. As the sea level rises, the corals try to get closer to the surface and start growing vertically to try and get closer to the sunlight.

Using sonar, the scientists were able to map in the Gulf of Mexico - some distance from the coast of Texas - terraces of coral fossils at a depth of about 60 meters below sea level. According to the researchers, these corals grew vertically at the end of the last ice age, about 20 thousand years ago. The findings indicate that the rise of the sea level then occurred in a series of sharp rises, which each time manifested in a sharp vertical growth of the corals. Eventually, the rate of upwelling became so high that the corals could no longer keep up with the receding sea surface, and without enough sunlight they died; But their remains - the coral skeletons - remained to tell the story of their lives.

This study stands in contrast to most previous predictions, which presented a scenario of gradual sea level rise. The assessment of the Intergovernmental Panel on Climate Change (IPCC) It predicted an increase of less than a meter until the end of this century, with a constant and gradual increase of several millimeters to centimeters per year. but A study published last year Led by renowned climate researcher and former NASA Chief Scientist James Hansen, he argued that we must prepare for the fact that beyond a certain point, sea level rise will occur suddenly and sharply.

Hansen's research concluded that the moderate process of melting ice on land and its flow into the sea - a process that occurs relatively slowly - has a kind of peak point, after which massive pieces of land ice will break off and melt into the sea, and then a sharper rise in sea level will occur. Additions of such masses of ice can raise the level more suddenly, especially if the processes of ice breaking occur simultaneously and in an increased manner in Greenland and Antarctica. Hansen's research was met with skepticism in the scientific community, but the current study confirms his hypothesis.

What to do? are being prepared

Such a rise in sea level would be devastating not only for communities living in coastal areas or for islands that are already almost at sea level; This is a disaster on a global scale that will affect the entire population of the world, who will be forced to crowd in areas that remain above water and out of the range of frequent flooding. Most of the world's population lives near the coasts, and therefore the effect of a rise in sea level will be extensive in scope. A good example of this is Australia, where almost the entire population is located along the west and east coasts. In the immediate time frame, it will be the destruction of facilities and infrastructure such as roads, electrical infrastructure, power plants and desalination facilities, which is expected to cost billions. Later, this could also lead to political instability and wars over food, clean water and land.

Such studies should remind us that it is impossible to continue treating this issue of sea level rise as something that might happen in the distant future, and that we should try to stop reaching this peak point. The purpose of agreement Paris signed in December 2015 is to limit the warming of the earth below 2 degrees Celsius above the temperature values ​​before the industrial revolution period and thereby slow down the rate of sea level rise. But the island countries - including Fiji, which managed the Annual Climate Conference This month in Bonn, Germany - they claim that in order to keep them from drowning below sea level, it is necessary to limit the warming by a degree and a half at most. According to the new study, it seems to be in the interest of all of us to do so, and at the same time to prepare now for scenarios of significant sea level rise. Proper preparation will not only save billions of dollars in the long run, but will also save many lives and help maintain our quality of life for decades to come.

And what about Israel? Currently sea level rise is not one of our priorities, or even in a good place in the middle of the list. This is despite the fact that the Mediterranean region is considered to have increased climatic sensitivity, and according to the forecasts, it is expected that in the next decades there will be warming, in the form and decrease of precipitation, and also - not surprisingly - a rise in the sea level. Some forecasts suggest that they are expected to rise even faster than the global average.

Despite this, the national action plan for preparing for and adapting to climate change in Israel has not yet been published, and today there is no blanket guidance on how to prepare for the issue from any governmental or planning body - even when it comes to the planning and construction of buildings and infrastructure in areas close to the coastline. If the corals are to be believed, it seems that the government should start preparing, or at the very least - subsidize advanced swimming lessons for the general public.

See more on the subject on the science website:

• Prepare for sea level rise (and save billions)
• The damages of the warming will remain with us for at least ten thousand years
• Climate warming will increase the movement of rain storms towards the poles
• Climate warming will bring the Earth to an unprecedented 420 million year high
• The summers are warmer - not just what we think