Trend analysis of significant wave height and energy period in southern Italy

The Mediterranean Sea is subject to significant and variable climatic changes. In this work, an analysis of a 39-year-long wave time series was performed in order to identify ongoing trends of two synthetic parameters, significant wave height and energy period, along the coasts of the Calabria region (southern Italy). First, wave data were acquired from the global atmospheric reanalysis data set European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim) and were processed in order to check their quality. Then, the data were subject to a geographical transposition method in order to transfer the wave parameters at a representative water depth of 100 m. Finally, trend analyses have been performed using the nonparametric Mann-Kendall (MK) test and a graphical technique, the Innovative Trend Analysis (ITA), which allows to identify trends in the several values of a series. At annual and seasonal scale, the results deduced from MK test mainly evidenced a slight or null increase of the significant wave height and a relevant increase of the energy period, influencing the magnitude of the wave power by the occurrence of longer waves. Moreover, the ITA method highlights a general increase in the highest values of the involved wave parameters. For the studied area, these aspects have a significant impact on the retreating of the beaches and on the future field installations of wave energy converters (WECs) for electricity purposes.