Understanding uncertainties in contemporary and future extreme wave events for broad-scale impact and adaptation planning

Understanding uncertainties in extreme wind-wave events is essential for offshore/coastal risk and adaptation estimates. Despite this, uncertainties in contemporary extreme wave events have not been assessed, and projections are still limited. Here, we quantify, at global scale, the uncertainties in contemporary extreme wave estimates across an ensemble of widely used global wave reanalyses/hindcasts supported by observations. We find that contemporary uncertainties in 50-year return period wave heights (H-s(50)) reach (on average) similar to 2.5 m in regions adjacent to coastlines and are primarily driven by atmospheric forcing. Furthermore, we show that uncertainties in contemporary H-s(50) estimates dominate projected 21st-century changes in H-s(50) across similar to 80% of global ocean and coastlines. When translated into broad-scale coastal risk analysis, these uncertainties are comparable to those from storm surges and projected sea level rise. Thus, uncertainties in contemporary extreme wave events need to be combined with those of projections to fully assess potential impacts.

Automated summary

Understanding uncertainties in contemporary extreme wave events is crucial for assessing offshore/coastal risk and adaptation estimates. In this study, we quantify the uncertainties in contemporary extreme wave estimates at a global scale and find that they are driven by atmospheric forcing. These uncertainties dominate the projected changes in wave heights across the majority of global ocean and coastlines, highlighting the need to combine contemporary uncertainties with future projections to fully assess potential impacts.