Like an air of Brittany on the Mediterranean coast. Unaccustomed to high tides, residents of the coast have seen an impressive decline in their sea for ten days, reports Var Matin. From France to Algeria, many are those who share the photos of beaches from a new angle and wonder. The sea level has dropped: by about 30 centimeters, since about February 9, confirms the hydrographic and oceanographic service of the Navy (Shom). A rare situation, due to a combination of factors. Explanations.
There is already a seasonal cycle, the minimum of which is reached in February or March. “Every year, we observe a drop of about 10 centimeters at this time,” notes Gaël André, tide expert at Shom. A usual setback due to the temperature of the water in winter, “which contracts when it is cold”. But this is not enough to explain the significant drop in level observed at the start of 2023.
Saint Florent, high Corsica, never seen the sea so low! pic.twitter.com/og7K50hRVr
“The main factor is the high atmospheric pressure, due to the strong anticyclone over the Mediterranean. Each additional hectopascal of pressure is one centimeter less water for sea level, recalls the expert, who estimates that the current situation causes another 20 centimeters to be lost. “1,035 hectopascals, as observed at the peak, you don’t see that often. Added to this is the very low rainfall on the land, also partly due to the anticyclone, which leads to “a deficit in fresh water supply” in the sea.
A surprising drop in level, while we tend to worry about the rising waters caused by global warming. “The rise in sea level is observed over the long term, nuance Gaël André. There are occasional decreases, but overall, there is a clear increase. Similarly, the rise in average temperatures observed over the long term does not prevent the persistence of a few occasional cold spells. In the Mediterranean, the episode should soon come to an end. “The level has already started to rise. »