Mallorca sea turns warmer, saltier down to 4,000m

The Mediterranean sea around Mallorca is growing warmer and saltier as far down as 3,000 to 4,000 metres, researchers report on 16 September. The change is being recorded across every basin of the Mediterranean, with the sharpest acceleration in its central and eastern waters and in the Adriatic. Scientists at Croatia’s Ruder Boskovic Institute drew on measurements taken between 1950 and 2025.

For Mallorca, the finding points to change far below the surface as well as in the water people see from the coast. Elena Terzic, the study’s lead author, said significant shifts were showing up in every region and at great depths.

Surface water is heating faster

The team combined temperature and salt-content measurements from research voyages and robotic floats. In some areas, warming is speeding up by as much as 0.3 degrees Celsius per decade. Each kilogram of water is also gaining about one tenth of a gram of salt per decade.

In recent years, the top 100 metres of the Mediterranean have been about two degrees Celsius warmer than the 1950-1999 average. Since 2000, surface water has warmed by roughly half a degree Celsius per decade — two to three times the rate of the global ocean surface.

The warming and rising salt content are statistically clear down to 3,000-4,000 metres, the researchers found. The acceleration reaches about 2,500 metres deep.

A changing flow to the deep sea

Heat makes seawater less dense, while extra salt makes it denser. Across most of the Mediterranean, warming has the stronger effect at the surface, making the water less able to mix with the layers below.

The Adriatic is different. There, added salt still helps make water heavy enough to sink. It then spreads through the central and eastern Mediterranean, carrying oxygen into deep waters. But since 2000, deep water in the southern Adriatic has warmed about six times faster than in a typical Mediterranean basin.

The study did not measure oxygen itself. However, warmer water holds less oxygen, and falling oxygen levels have already been documented in parts of the Mediterranean. That leaves fewer cooler deep-water refuges for marine species trying to escape warming.

The researchers will now examine the roles of the atmosphere, evaporation, rain, river flow and Atlantic water entering through the Strait of Gibraltar. They also plan to test whether climate models are capturing the faster pace of change.

Source: Europa Press / Mallorca.com