Temperature and salinity double in Mediterranean

The Mediterranean is responding very quickly to global warming and the rate of evaporation is higher than precipitation and fluvial supply. Temperatures and salinity is also increasing at two and a half times the rate at the midway point in the twentieth century and higher than that of the oceans, according to research published in Scientific Reports by a team of oceanographers from the marine sciences institute of the Italian national research center (ISMAR-CNR), the National Oceanography Centre di Southampton (UK) and the Institut National des Sciences et Technologies de la Mer di Salamboo (Tunisia).

”The Mediterranean Sea,” says Katrin Schroeder, a CNR researcher and author of the research, ”is one of the regions that is most susceptible to an increase in temperatures and a reduction in rainfall, where the effects of global warming are seen more rapidly than in the oceans, in part because the turnover of the waters happens in a relatively brief span of time compared with that of an ocean. In the Mediterranean, evaporation is the higher than precipitation and fluvial supply and, in the eastern basin, aridity and temperatures have recently reached their highest points in the past 500 years.” ISMAR-CNR has for over 20 years been analyzing the characteristics of the water transiting through the Strait of Sicily, a point of contact between the eastern and western basins of the Mediterranean.

”The data of the study show that since the end of 1993 until today, the temperature and salinity of the water coming from the eastern Mediterranean, between 300 and 600 meters below sea level, have experienced significant variations. In particular, the rapidity with which they are increasing is two and a half times that seen in the eastern Mediterranean in the second half of the twentieth century and is much higher than that seen in oceans,” the researcher added. ”The Mediterranean can be compared to a machine that imports surface water with low salinity and density from the Atlantic Ocean and transforms it within itself through complex processes that involve the production of hotter, saltier water, to then export it towards the Atlantic, from the depths to the Strait of Gibraltar.” In the Strait of Sicily, the flow of water from the two basins is on two levels: the water of Atlantic origins, saltier and lighter, on the surface level and which moves towards the east, and the intermediate one generated by the intense evaporation in the eastern than is heavier and that moves towards the western basin in the lower level. ”The physical properties of the intermediate water determine the quantity, temperature and salinity of the deep water generated in the northwestern Mediterranean.

These two characteristics of the deeper level are very stable and have always been considered an important benchmark to quantify every single, minimal effect of climate change,” Schroeder said. ”We hold that for about half a century, their salinity and temperature has increased gradually, while since 2005, these parameters have been rising at double the speed compared with the period between 1960 and 2005,” she said. Large volumes of deep water that is very hot and salty are thus being generated. ”These data,” the researcher said, ”suggest that a rapid transition is underway towards a new equilibrium that reverberates on the ecosystem of the deep sea.”


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