What is the role of decreasing river runoff in future Adriatic water stratification and sea level rise? A new study, led by CMCC researcher Giorgia Verri, uses a climate downscaling approach to predict the Adriatic water cycle up to 2050 in what is one of the first attempts to provide a comprehensive and high-resolution climate modelling of the basin’s coastal water cycle.

Although the Adriatic Sea is part of the Mediterranean, it is characterized by unique local features which make it particularly vulnerable to climate change. In fact, the basin’s long-term evolution of physical and biogeochemical processes is only partially explained by global ocean trends, whereby local climate-related hazards may be amplified or even diverge from global averages, leading to distinct and intensified impacts in this area.

A new study led by CMCC within the AdriaClim project, provides novel evidence that a reduction in river discharge by about 35%, considering over 140 rivers flowing into the Adriatic Sea, will have a significant impact on future Adriatic water stratification and sea level rise, with significant differences between the Northern and Southern sub-basins.

The findings contained in the paper suggest that a decrease of the river release in coastal and marginal seas may act in the opposite direction to global heating by weakening the density stratification, increasing the dense water formation, and reducing total sea level rise.

Sketch of the main catchments, among the 145 ones prognostically solved by the hydrology model WRF-Hydro, which provide river release to the marine hydrodynamics model NEMO and marine biogeochemistry model BFM. Source: Verri et al, 2024.

These findings are crucial for advancing knowledge of the present and future climate of the Adriatic, as well as supporting coastal vulnerability studies such as those related to shoreline retreat, the evolution of coastal eutrophic zones, salt-wedge intrusion and the salinization of inland waters.

“A message for the climate scientific community is that trustable climate projections at the coastal scale cannot overlook a detailed representation of the multi-physics, multi-scale and cross-scale processes that make up the coastal water cycle,” says lead author of the paper and CMCC researcher Giorgia Verri, who led the AdriaClim project modelling activities for this research and has co-authored other companion papers based on these modelling results. “In particular, non-seasonal river discharge is a key piece of information to correctly predict and project sea surface salinity and sea surface height on multiple timescales, from a daily basis to a decadal range.”

By focusing on a climate downscaling approach, concentrating on the Adriatic water cycle, the study encompasses integrated modelling at the mesoscale, covering the atmosphere, hydrology, and marine general circulation and biogeochemistry. Analyzing a period spanning from 1992 to 2050, using high emission scenario RCP8.5, it evaluates how river release projection affects the local density stratification and sea level rise.

The study is the first to provide evidence of how decreasing river discharge, jointly with increasing evaporation, can reduce density stratification locally, increase dense water and mitigate sea level rise, thus acting contrary to the effects of global warming on the Northern Adriatic water column. This modeling result contributes to enhancing our knowledge of the Adriatic climate dynamics at local scales and is crucial for conducting reliable coastal vulnerability studies.

Additional information:

Verri Giorgia , Furnari Luca , Gunduz Murat , Senatore Alfonso , Santos da Costa Vladimir , De Lorenzis Alessandro , Fedele Giusy , Manco Ilenia , Mentaschi Lorenzo , Clementi Emanuela , Coppini Giovanni , Mercogliano Paola , Mendicino Giuseppe , Pinardi Nadia; Climate projections of the Adriatic Sea: role of river release; Frontiers in Climate; 6; 2024; DOI=10.3389/fclim.2024.1368413

The climate simulation datasets analyzed in these studies is freely downloadable from the AdriaClim Project repository on ERDDAP Server