The State Meteorological Agency (Aemet) has activated the alert for a meteotsunami on Ibiza and Formentera. The arrival of the Ciril storm, a polar air mass will lower temperatures from this Friday and this drop temperatures will cause a meteotsunami, or ‘rissaga’ in the western Mediterranean that will affect the Balearic Islands, Almeria and Granada, the Valencian Community and Melilla.
The meteotsunami is a meteorological term that defines what is known as ‘rissaga‘ on Menorca, where it is very common. It is related to variations in atmospheric pressure.
What is a meteotsunami?
A meteotsunami is a sudden rise in sea level. Usually, the sea recedes temporarily and then rises several meters in height in a matter of minutes. It is usual for the sea level to rise a few centimeters, but there are occasions when it can rise several meters.
The Aemet defines a meteotsunami as “destructive ocean waves that have the same temporal and spatial scales as ordinary tsunami waves”. In other words, the air pushes the water mass of the seas and oceans, generating in turn a movement of the water, in the form of oscillations in the sea level.
This is the reason for the rise and fall of the sea level. This type of tsunami is caused by a very sudden change in atmospheric pressure.
Meteotsunamis can reach an amplitude of two meters in a few minutes. But normally, sea level oscillations are 60 to 120 centimeters, with periods of 10 minutes, but oscillations of up to four meters have been reached.
This phenomenon is most common on Menorca.
In the Canary Islands the ‘rissagas’ are known as ‘Mareas del Pino’ as they occur every year coinciding with the feast of the Virgen del Pino around September 8th. In Italy, especially in the Gulf of Trieste, it is known as ‘marrubio’ and in the Gulf of Gabes, it affects the riparian countries of Tunisia and Malta.
In many other parts of the globe, such as the Sea of Japan and the East China Sea, the phenomenon is known as ‘abiki’.
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