Temporal variability in winter wave conditions and storminess in the northwest of Ireland

Abstract

Winter storms have significant morphological impacts in coastal areas, often leading to extensive infrastructure damage and socio-economic disruption. While storm-dominated coastal environments, such as the northwest coast of Ireland, are generally attuned to highly energetic wave conditions, morphological impacts can be intensified by changes in the frequency and sequencing of storm events, particularly during storm-groups or exceptional winter seasons. Aiming to assess the variability in frequency and sequencing of wintertime wave conditions and storms in the northwest of Ireland, we combine observational records (M4 buoy) with data from two independent wave reanalyses (ERA-Interim and WAVEWATCH III) and perform a statistical analysis of wave conditions over the past six decades. Both reanalyses represent observed wave heights with very good skill. Excellent agreement between modelled data and observations was identified up to the 99th percentile, despite a slight underestimation/overestimation by ERA-Interim/WAVEWATCH III for waves above the 90% exceedance level. The winter of 2014/15 was the most energetic on record (67 years), but not the stormiest. The results show that highly energetic and stormy winters occur in clusters during positive phases of the North Atlantic Oscillation. Significant positive temporal trends for winter wave height, number of storms per winter and average winter storm wave height, suggest that winters are becoming more energetic and stormier, with potential implications for the erosion and recovery of coastal systems in the northwest of Ireland.