On the concordance of 21st century wind-wave climate projections

Understanding anticipated climate-induced changes in the global wind-wave climate is paramount for sustainable development of coastal and ocean industry-operations, resources, ecosystems and for the mitigation of potential impacts on coastal settlements. Intensive research has been placed into global and regional wave climate projections over the past 10 years, but no systematic review has been conducted to date. Here, we present a consensus-based analysis of 91 published global and regional scale wind-wave climate projection studies to establish consistent patterns of impacts of global warming on the wind-wave climate across the globe. Furthermore, we critically discuss research efforts, current limitations and identify opportunities within the existing community ensemble of projections to resolve various sources of uncertainty amongst the sparsely sampled set of future scenarios. We find consensus amongst studies regarding an increase of the mean significant wave height (H) over bar (S) across the Southern Ocean, tropical eastern Pacific and Baltic Sea, and conversely, a decrease of (H) over bar (S) over the North Atlantic and Mediterranean Sea. Furthermore, we observe that projections of (H) over bar (S) over the eastern north Pacific and southern Indian and Atlantic Oceans lack consensus. Similarly, future projections of extreme H, lack consensus everywhere, except for the Southern Ocean and North Atlantic. We note a distinct lack of research regarding projected changes in wave direction which is of critical importance particularly for the mitigation of coastal hazards. Furthermore, we observe that the projection uncertainty surrounding wind-wave climate projections has been poorly sampled. Subsequently, we identify sets of coordinated experiments within existing studies that can be used as a basis to systematically quantify these uncertainties. Lastly, we recommend a shift towards a systematic, community-based framework (as propose by the COWCLIP) to foster concerted efforts and to better inform the wide range of relevant decisions across ocean and coastal adaption and mitigation assessments.