Multi-decadal assessment of wave power and variability from satellite altimetry observations in Ireland

Thirty years of observations from a calibrated multi-mission satellite altimetry dataset are employed to assess the Irish wave power density (energy flux) as well as its long-term variability. The significant wave height and the back-scatter coefficient measured by the altimeters, together with Irish moored buoy observations, are utilized to estimate the zero-crossing wave period from satellite observations via an inversion model. The relationship between the zero-crossing period and the wave energy period, known as the wave period ratio, is estimated within the study area based on previous research utilizing spectral moments from a satellite-borne wave scatterometer. Decadal and seasonal wave power maps are subsequently calculated for the period from 1995 to 2024. Wave power density variation is computed via the coefficient of variation , seasonal variation, and long-term trends. The results are compared to previous studies relying on numerical wave modelling and yield strong agreement, demonstrating the utility of the rapidly growing repository of satellite altimeter measurements in the context of wave energy resource assessment. Notably, seasonal Mann Kendall test reveals an increasing trend in wave power density which is statistically significant along the south-west coast of Ireland ranging from 0.3 to 0.45 kW/m per year. The seasonal variation index has also increased slightly over recent decades.