Deep Adriatic temperatures already hit end-of-century estimates

For centuries, the Adriatic Sea has cooled the Mediterranean, but today it is sending warmer waters down south as it heats up much faster than projected. Deep water temperatures forecast for the end of the century are already being recorded, threatening ecosystems, the climate, and coastal communities, according to a study by scientists from Croatia, Italy, and Slovenia.

Data collected in the South Adriatic Pit, the deepest part of the Adriatic Sea, suggest the seawater temperature at a depth of 1,000 meters has increased 0.8°C over the past decade, with salinity rising by 0.2 PSU (Practical Salinity Units), according to Croatia’s Ruđer Bošković Institute (RBI).

This may signal a permanent shift in the region’s climate patterns, RBI said. Importantly, the trend is accelerating: deep-water warming rates were once around 0.2°C per century, but between 2012 and 2024 they jumped to 0.8°C per decade, it stressed.

The Adriatic drives currents that ensure stability and oxygen supply to the depths of the Mediterranean

RBI explains that the Adriatic Sea acts as a natural “thermostat,” regulating temperature patterns throughout the Mediterranean basin. In winter, cold, dense waters in the shallow northern Adriatic sink to the seafloor and then flow through the Strait of Otranto into the deep Mediterranean. This process drives currents that ensure stability and oxygen supply to the depths of the Mediterranean Sea.

Today, however, the traditionally cold water formed along the Croatian coast is becoming increasingly warm and salty before beginning its southward journey. Instead of cooling the deep Mediterranean, the Adriatic now sends warmer waters that further heat the entire system, RBI explains.

Warmer waters threaten deep-sea fish and attract species from the eastern Mediterranean

The changes are already affecting biodiversity, particularly species adapted to life in deep, cold waters. Unlike terrestrial animals that can migrate north as the climate warms, deep-sea species remain stuck on the seafloor, according to Dr. Ivica Vilibić, co-author of a study based on the international research project.

At the same time, the warmer waters are attracting tropical species from the eastern Mediterranean, altering the entire ecosystem, he warns.

The problem is not just local – it could affect all of Europe

Moreover, these changes are not just a local Adriatic issue. They could affect the entire European climate system while contributing an additional 3.3 millimeters of sea-level rise per year, scientists estimate.

“Nature is warning us that something significant is happening,” says Vilibić, adding that scientists’ task is to understand these processes and help society prepare for the changes ahead.