Environment: From ENEA new model to estimate Mediterranean sea-level change

17 March 2022 Last Updated: 14 September 2022

ENEA climate modeling researchers have developed an advanced mathematical model, called MED16, capable of reproducing as faithfully as possible the VARIABILITY of Mediterranean Sea LEVEL, from the past to the future. "The latest 2021 IPCC report points out that average projections of sea level rise are not accurate enough for marginal basins like the Mediterranean, which require specific models. Our study finally fills this scientific gap ", explained Gianmaria Sannino, head of the ENEA laboratory of Climate Modeling and Impacts and author of the new study .

"For the first time we will have a reliable database to track the change in our sea which, since 1980, has been warming faster than the global ocean and where, therefore, the effects of climate change will be amplified, a serious threat for coastal communities ”, continued Sannino.

The level of the Mediterranean Sea varies from site to site and is the result of local tectonic movements, a complex dynamics of water masses, even on a small scale, and exchanges with the Atlantic Ocean through the Strait of Gibraltar. The connection with the Black Sea, a collection point for the waters of Europe's major rivers also influences the characteristics of the basin, correlating them with the hydrological cycle of a large portion of continental Europe.

The new ENEA climate model has a spatial resolution never before achieved. "Current global models represent the Mediterranean as a lake, isolated from the Atlantic, and for this reason they are not sufficient to provide realistic estimates of its level variations. Now, thanks to MED16, we are able to cover the entire 'Mediterranean-Black Sea' system, and a small part of the Atlantic Ocean west of the Strait of Gibraltar, with a uniform spatial resolution of 1/16 °, equal to about 7 km ”, pointed out Sannino, who continued:“ We have also considerably increased the detail in correspondence of the straits, to reliably represent the local dynamics of water exchanges; we are therefore talking about 200 meters for the Strait of Gibraltar and 550 meters for the Dardanelles and the Bosphorus ".

Anthropogenic climate change has helped raise the average level of our seas by more than 25 centimeters over the past 130 years. But what will happen to the Mediterranean in the next few years? “The future holds no good news. If we fail to reverse the current global temperature rise, at the turn of the century, in 80 years, the sea level will be about 60 centimeters higher than today. These VALUES should not be underestimated. A few centimeters of elevation can lead to flooding of several square kilometers of coasts ", explained Sannino.

In the last decades, sea rise has not been homogeneous in the Mediterranean: from 1993-2017 data, the increase goes from a minimum of 1.95 mm / year in the Ionian Sea to a maximum of 3.73 mm / year in the Aegean Sea. The western Mediterranean shows a more regular trend, largely induced by the signal coming from the Atlantic Ocean. The eastern basin shows a more complex behavior, with a marked internal variability.

"With the model MED16 we simulated the past evolution of the Mediterranean circulation and the future one up to 2100. The comparison with the observed data confirmed the capability of our new model to correctly reproduce the characteristics of the basin. These simulations constitute the reference basis for future projections not only for the long time span they cover and for the high spatial resolution, but also because they explicitly take into account the tides and their interactions with the circulation ", concluded Sannino.

According to the ENEA projection to 2100, considering the most pessimistic scenario of the IPCC (high emission and high value of the radiative forcing, equal to 8.5 W / m2), the temperature of the Mediterranean Sea will continue to increase, and the surface salinity decrease in the western part of the basin, affected by the Atlantic current. In addition to sea level rise, the warming of waters will partly inhibit the formation of deep waters which, by transporting oxygen to the deep layers, allow the sea to 'breathe', creating the conditions for the survival of natural habitats.