The Mediterranean Sea is warming and becoming saltier at an increasingly rapid pace, with changes observed even thousands of meters below the surface. A new study published in Geophysical Research Letters reveals that temperature and salinity increases are happening almost everywhere in the basin, and the rate of change has been accelerating over time. This acceleration is most noticeable in the central and eastern parts of the Mediterranean, particularly in the Adriatic Sea, where changes have been detected all the way down to the sea floor. Since the beginning of the 21st century, Mediterranean surface waters have warmed by about 0.5 degrees Celsius per decade. That is two to three times faster than the global ocean surface warming rate. This is a significant increase compared to the less than 0.1 degrees Celsius per decade observed in most of the Mediterranean during the second half of the 20th century. The warming and increased salinity are statistically significant even at depths of 3,000 to 4,000 meters, with the acceleration reaching down to about 2,500 meters. The study compiled temperature and salinity data from research cruises and robotic floats across the Mediterranean from 1950 to 2025. It shows that these changes are not limited to the surface but extend to great depths, with the Adriatic Sea showing particularly notable changes. The Adriatic is unique in the Mediterranean because cold winter winds make surface water dense enough to sink, forming deep water that spreads into the central and eastern parts of the basin. However, since 2000, the deep waters of the southern Adriatic have warmed about six times faster than typical Mediterranean waters. The study's authors, Elena Terzić and Ivica Vilibić from the Ruđer Bošković Institute, warn that the rapid changes are having significant impacts on marine ecosystems. Warmer waters can encourage the movement and establishment of new species, such as the rabbitfish, which can damage seagrass meadows. Marine heatwaves, like the one that hit the Mediterranean this summer with temperatures approaching 30°C in some areas, can lead to mass mortality, especially among gorgonians—important "engineers" of the marine ecosystem that provide habitat for other species. The study also raises concerns about the future of deep water formation in the Adriatic. Increased salinity might counteract the effects of warming, potentially changing how dense water forms and sinks. The authors note that warmer water holds less oxygen, and oxygen levels have already declined in parts of the Mediterranean. Additionally, marine species trying to escape the warming are running out of refuges, as the sea is closed to the north and the deep water is also warming. The Mediterranean's rapid response to climate change is due to its faster circulation rates compared to the open ocean, making it an early indicator of how larger ocean basins might change under a warming climate. The study's authors plan to investigate the factors driving this acceleration, including atmospheric conditions, evaporation, rainfall, river discharge, and Atlantic inflow through the Strait of Gibraltar. They also aim to determine whether current climate models accurately capture the speed of these changes, which is crucial for reliable future projections in the region.