Climate: Hot Mediterranean, +4° above seasonal averages

Increasingly hot temperatures in the Mediterranean are setting off alarms in the region: since 10 May the mare nostrum has been hit by a heat wave[1] that has raised the sea surface temperature by around 4°C compared to the average for the period 1985-2005, with peaks of over 23°C. This is what emerged from the first results of the CAREHeat (deteCtion and threAts of maRinE Heat waves) project financed by the European Space Agency (ESA), in which ENEA and CNR are participating for Italy, CNR in the role of coordinator.  Specifically, the project aims to develop new methods to predict and identify heat waves, understand their propagation and impacts on the environment, biodiversity and businesses such as fishing and aquaculture.

"The term Marine Heat Wave (MHW) refers to situations in which the difference between the measured sea surface temperature and the climatological value, i.e. expected for that particular region at that specific time of year, exceeds a critical threshold for at least five days in a sufficiently large area of the sea", explained Salvatore Marullo of the ENEA Laboratory for Climate Modelling and Impacts. “The research”, he added, “began with the study of the heat wave currently affecting the Mediterranean Sea, starting with the analysis of the available satellite data that first detected the thermal anomaly, with values comparable to the 2003 heat wave. Temperatures well above the seasonal average have been recorded in the Mediterranean area since the beginning of May, and the first half of June was also characterised by weather that was more typical of the later stages of the summer”.

Starting with a description of the state of the art on the detection of MHWs, the project aims to define current knowledge gaps and proposed methods for overcoming them, considering climate variability and driving meteorological events, i.e. heat waves in the atmosphere fostered by favourable meteorological conditions, such as for example the persistence of an African anticyclone, without neglecting the analysis of available data sources and biological impacts reported in the literature. Subsequently, numerical models and data from automatic profilers of physical and biochemical parameters (ARGO and BIOARGO) operating in the Mediterranean will help assess the impact of this thermal anomaly in the deeper layers of the sea and thus on a marine ecosystem struggling with the difficulties associated with a rapid temperature change.

“Understanding what exactly is happening to the current climate is becoming increasingly important because the changes are starting to concretely affect everyday life and economic activities down to the individual citizen, including the exacerbation of migration”, pointed out Gianmaria Sannino, head of the ENEA Climate Modelling and Impacts Laboratory. "So", he continued, "it’s appropriate to quantitatively define the these phenomena in order to understand their causes and predict their developments, focusing on the oceans that cover about 70% of the Earth's surface in order to plan and manage ecosystem services and sustainable development”.

As part of the project, starting in July researchers will launch the phase that involves the use of state-of-the-art models, including those based on neural networks, to automatically detect MHWs, assess their impact on the marine ecosystem, and define the concept of a heat wave in the current context of global warming.

The study will begin with the analysis of main events by areas of interest, also considering the needs of users who will be able to take advantage of the results of this research. To this end, stakeholders in the sector (fish farming, fishing and protected marine areas) responded to a questionnaire also aimed at defining the objectives of the project.

In addition to ENEA and CNR, the French research institutes CLS (Collect Locatisation Satellites) and IFREMER (Institut Français de Recherche pour l'Exploitation de la Mer) as well as the non-profit Mercator Ocean International (France) and +ATLANTIC CoLAB (Portugal) are participating in the CAREHeat project, financed by ESA as part of the European Commission's “flagship actions”.

For more information:

Salvatore Marullo, ENEA - Climate Modelling and Impacts Laboratory, 

[1] The term sea heatwave refers to situations in which the difference between the measured surface water temperature and the “expected” climatological value exceeds the critical threshold for at least five days over a sufficiently large area.