Bringing the Ocean to Society
26 May 2020
Mediterranean temperature increases one degree every 100 years
EurOcean Member IEO confirms the trend and warns of the serious effects that it may have on ecosystems.

A report published by the Mediterranean Climate Change Group of the Spanish Institute of Oceanography (IEO), which compiles the information obtained during nearly 30 years of oceanographic campaigns in the Mediterranean, confirms the increase in temperature and salinity of its waters and alerts on the serious effects that this trend will have on ecosystems.

IEO scientists have published, in the series “Themes of Oceanography”, the report entitled “The current state of marine ecosystems in the Spanish Mediterranean in a context of climate change”, a work that collects data from about a hundred oceanographic surveys carried out over the past 30 years.

In the current context of climate crisis it is of vital importance to know what the current state of our marine ecosystems is, a knowledge that is only possible from the continuous monitoring over time of fundamental properties of the seas such as temperature, salinity, the content of oxygen, nutrients or the abundance and diversity of phytoplankton, among others. This report aims to establish a starting point for rigorous knowledge of the state of Mediterranean marine ecosystems that allows detecting the changes that may occur in the future, as well as evaluating those that have already occurred today.

At what rate are the waters of the Mediterranean warming? How is salinity varying? How much has the sea level rise? Are these changes affecting marine ecosystems? Has the oxygen content or the abundance of algae in the Mediterranean been reduced? These are some of the questions this new publication tries to answer, which can be downloaded here.

"The threats that hang over the planet's oceans due to the current climate crisis are multiple," explains Manuel Vargas, a physicist at the IEO Oceanographic Centre in Malaga and first author of the report. The variations in temperature and salinity of the Mediterranean could alter the intensity and position of its currents. The increase in temperatures can cause the displacement of different marine species, change the laying seasons or the duration of these periods depending on each species. The stratification of the waters, that is, the contrast between the warm surface waters and the colder deep waters, could be accentuated as a consequence of the warming of the sea. This increase in stratification entails greater difficulty for the mixing that the wind performs between the surface waters and those that are below them, producing a decrease in the contribution of nutrients to the well-lit surface layers where photosynthesis occurs, the base of the food chain and oxygen-producing mechanism that also helps CO2 sequestration. Likewise, this increase in the temperature of the superficial layers could inhibit the convection processes, by means of which the superficial waters mix with the deep ones until depths to which the action of the wind does not reach. The decrease in the intensity of these convective processes, or even their absence, could drastically reduce the oxygenation of deep waters with very negative consequences for marine fauna.

However, it is difficult to know to what extent these processes have advanced in seas such as the Mediterranean. "In a constantly changing environment such as the sea, the detection of long-term variations that show the effects of the climate crisis is only possible from a deep knowledge of the current state of the state of its ecosystems and the evaluation of those changes, which they are produced slowly but inexorably over time, it requires constant and costly work such as that carried out by the IEO Mediterranean Group on Climate Change, over more than 25 years, ”says Vargas.

Original news article on IEO's website