Trends in ocean waves climate within the Mediterranean Sea: a review

The interest for the impact of climate change on ocean waves within the Mediterranean Sea has motivated a number of studies aimed at identifying trends in sea states parameters from historical multi-decadal wave records. In the last two decades progress in computing and the availability of suitable time series from observations further supported research on this topic. With the aim of identifying consensus among previous research on the Mediterranean Sea and its sub-basins, this review analysed the results presented in peer reviewed articles researching historical ocean waves trends published after the year 2000. Most studies focused on the significant wave height trends, while direction and wave period appear to be under-studied in this context. We analysed trends in mean wave climate and extreme sea states. We divided the Mediterranean basin in 12 sub-basins and analysed the results available in the literature from a wide range of data sources, such as satellite altimetry and numerical models, among others. The consensus on the significant wave height mean climate trends is limited, while statistically significant trends in extreme values are detected in the western Mediterranean Sea, in particular in the Gulf of Lion and in the Tyrrhenian Sea, with complex spatial distributions. Negative extreme sea state trends in the sub-basins, although frequently identified, are mostly not significant. We discuss the sources of uncertainty in results introduced by the data used, statistics employed to characterise mean or extreme conditions, length of the time period used for the analysis, and thresholds used to prove trends statistical significance. The reduction of such uncertainties, and the relationship between trends in sea states and weather processes are identified as priority for future research.