2023-08-07 15:15:24
The climate crisis is seriously affecting marine ecosystems around the world and the Mediterranean is no exception. The marine heat waves associated with this crisis have caused and are causing mass mortality events throughout the basin. Given this scenario, its correct definition and characterization become a key element to define possible future scenarios.
Now, a new study from the ICM (Institut de Ciències del Mar) of the Higher Council for Scientific Research (CSIC) in Spain and the Institute of Marine Sciences of the National Research Council of Italy has revealed how separating the warming trend affects when defining the characteristics of marine heat waves. According to the authors of the study, this would be the cause of an apparent magnification of the frequency and intensity of this type of extreme events.
For the preparation of the work, the researchers analyzed a set of data corresponding to the surface temperature of the Mediterranean Sea collected during the last 41 years (1982-2022) by the Copernicus Marine Surveillance Service (CMEMS).
“Our results show that when the temperature data is analyzed without correcting the trend during the study period, marine heat waves are not adequately detected and their characteristics, such as frequency, intensity or duration, are biased,” explains Justino Martínez, ICM researcher and first author of the paper.
Thus, analyzing surface temperature anomalies without correcting the trend produces an increase in the frequency and intensity of marine heat waves in recent years of any time series studied, which ends up underestimating the marine heat waves that occurred longer ago. According to the authors of the study, this would be linked to a warming trend in the region and not to the actual change in the characteristics of heat waves.
“The fact of correcting the series by subtracting the trend from the data makes it possible to distinguish and separate between what is long-term warming and the transient and abrupt changes in surface temperature (heat waves), obtaining a more accurate description of the properties of marine heat waves”, adds Martínez in this regard.
Map of the surface temperatures of the Mediterranean Sea on July 24. (Image: Copernicus / ICM / CSIC)
Major heat waves in the Mediterranean
The study also publishes a catalog of the main heat waves that have occurred in the Mediterranean since 1982. In total, during the period analyzed, 15 marine heat waves classified as severe and 5 as extreme were detected (1989, 1993, 1999, 2001 and 2007).
Among them, it is worth highlighting the events of 1999, with the highest percentage of surface area affected in the entire series, and the event of 2003, which affected all the Mediterranean sub-basins with high values of average and maximum intensity (up to 7 degrees Celsius). more than usual) for 94 days. This event also coincided with an atmospheric heat wave across the European continent. Finally, the authors of the paper highlight an event that occurred last year that lasted from May to December -131 days-, although with less intensities than the 2003 event.
However, the work shows the influence of climate change on the warming of the Mediterranean, which makes marine heat waves have greater effects. “This represents a significant challenge for the management and conservation of the region’s marine ecosystems, although it is very valuable information for future studies on the impact of the climate crisis on the ocean at a time of particularly alarming sustained warming,” conclude the study authors.
The study is entitled “Evolution of marine heatwaves in warming seas: the Mediterranean Sea case study”. And it has been published in the academic journal Frontiers in Marine Science. (Source: CSIC)
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