Long-Term Trends in Significant Wave Heights in The Mediterranean as an Indicator of Climate Change

Abstract

The Mediterranean coastal zones, particularly along the Nile Delta, are increasingly vulnerable to the impacts of climate change. This study examines the historical changes in the significant wave height along the Nile Delta coast over the past 84 years (1940-2023) at a depth of 20 meters. By synthesizing a comprehensive long-term wave data series using ERA5 reanalysis data and the MIKE21-SW model, the study establishes a robust foundation for analysis. To ensure accuracy, the observed wind data were contrasted against ERA5 data, and they were found to be similar to a great extent. Furthermore, the model's accuracy was rigorously validated against the observational data, ensuring the reliability of the results. Three methods were used to obtain the trends for the maximum wave height to ensure robust and reliable trend assessments (i.e., linear regression, Theil-Sen, and ElasticNet). The results were obtained and analyzed, revealing a statistically significant increase in the maximum wave heights during the study period. Particularly, seasonal analysis revealed a positive trend in maximum wave heights during winter and spring (0.15 to 0.67 cm/year respectively). Furthermore, the monthly analysis showed a positive trend in the wave heights for all months except July, August, and September. Specifically, there were notable increases from September to December, ranging from 0.24 to 0.92 cm/year. These findings are consistent with the global trends of increasing wave heights due to climate change. It is essential for developing adaptive coastal management strategies and designing resilient structures. Consequently, the results will assist coastal authorities in mitigating the impacts of climate change on coastal zones.