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Photos, publications, scenarios that speak of ecological disaster and much more that we have heard in recent days about seas not only in Greece but also in the Mediterranean in general. The reason; The retreat of the waters, the fall of the level and the pieces of land that emerge as a “foreign body”.
Impressive images are circulating the Internet as scientists emphasize that this is a normal thing that we should not worry about.
The professor of Oceanography at the National and Kapodistrian University of Athens, Serafeim Poulos speaks on newsbeast.gr analyzing the phenomenon of the decrease in sea level while explaining that the coasts of our country have been affected by Climate Change.
“We have a drop in sea level. Because we always compare sea level to land, we see that we have a relative change based on land. In Kavouri, which we all have in Athens, for example, we suddenly saw an island that joined the other side because the part that connects it was revealed by the sea. Many considered that due to the seismic activity of the last days, the wasteland could rise, which was impossible. The University of Athens and specifically the geophysics laboratory observe the movements made by the Ionian Islands due to earthquakes, registering that the changes are only a few millimeters ”, he characteristically points out.
Why can sea level drop?
Sea level, as Seraphim Poulos explains, can be affected by the tide, which is divided into two categories, astronomical and meteorological. The astronomical tide is due to the eclipse of the Sun and Moon and the other planets while the meteorological Meteorological phenomena.
“In this case, the question is whether we have an astronomical or meteorological tide or both,” said the EKPA professor.
“If we had astronomy, twice a day we should have maximum percentages and twice a day minimum, so in 24 hours the sea level should rise and fall. But we do not observe such a thing because we only see a drop. Also in astronomy tide the range of the level change does not exceed 20 cm. So this case again cannot be astronomical because we have a drop of about 45 to 50 cm. We know that the range of astronomy is so great because, for example, in Thrace, our colleague George Sylaios has measured it with the weighbridge they have ”, he explains.
“Some people got carried away because on February 27 we had a full moon and on March 2 we had the periphery, that is, the phase in which the Moon approaches the Earth, so the astronomical phase is strengthened. In order to put the two elements together again, we cannot exceed these 20 cm ”, he states and clarifies that“ this is how we are left with the meteorological, which is responsible for what we see ”.
What factors affect the meteorological tide?
There are two factors that affect it. “It just came to our notice then. For example, colleagues in Thessaloniki measured on February 25 that it was 1,034 ectopascals, on February 28 it went down to 1,021 and it rose again on March 2 to 1,032 when an average value is 1,013. That is, we have a difference of 20 to 30 ectopascals of increased atmospheric pressure which means that they push the surface of the sea down and there is a correspondence of approximately, not exactly one ectopascal per centimeter. So 20 ectopascals gives us an additional decrease of 20 cm level ”, says the professor of Oceanography at the National and Kapodistrian University of Athens.
«But we have more than the other 20 to 30 cm. These have been given to us by the north wind that blew from February 28 to early March as it pushed the sea down with surface friction. Essentially, the water bodies come from the Aegean of the Cretan Strait and go to the eastern Mediterranean. The Eastern Mediterranean, however, is currently experiencing a drop in level with the water going to the western and central Mediterranean ”, he adds, noting that“ Venice has the same fall of the sea at the moment ”.
When will sea level rise again?
Seraphim Poulos, Professor of Oceanography at EKPA, explains that the phenomena responsible for the drop in sea level in mid-March will have receded and the coasts will return to the way they were before. «This will happen when atmospheric pressures return to normal levels around 1,100 ectopascals and the recovery will be significantly faster if we have winds from the south.. “If we do not have new meteorological phenomena in the next few days, we will return to normal levels,” he says.
“As a phenomenon it occurs often but not to this extent,” he points out, however, stating that we did not pay as much attention to it as such extensive parts of the coast were not revealed and we did not notice it.
“People were worried this time because the fall was big and a lot of people combined it with the strong earthquakes that shook our country, which is wrong,” he said.
“There is no absolute value of the level, it is something that is constantly changing but we are studying the range of change,” he added.
Because it is not low tide but low level
“Low tide is a phase of the astronomical tide. That is why we emphasize that this phenomenon is not something like that, but is called a decrease in sea level”, responds the professor of Oceanography.
How climate change has affected the Greek coast
“THE Climate change it has to do with two things. With a gradual increase in sea level due to overheating and with the change in the intensity and frequency of extreme meteorological phenomena. In the first case we say that we are facing an increase that is probably around three millimeters a year during the last 10 to 15 years. One millimeter to emphasize that it is a normal increase, however the level would rise one millimeter per year. This millimeter in the last 20 years has changed (also in our country) and in the last five years in measurements in the eastern Mediterranean it was found that the level has risen from three to millimeters. Some argue that it is Climate Change and that is why we call it Climate Variability. Of course, all this is under investigation and we will be able to speak with certainty when a sufficient period of time has passed (at least 30 years) because in nature not everything is normal but it depends, ”explains Seraphim Poulos.
Finally, he emphasizes that due to Climate Change we have more winds from the north but also with more winds not only in Greece but throughout the world.
