Task 3: Global Wind-Wave Projections

Community ensemble of 21st Century wind-wave climate projections

A long-term objective of COWCLIP is to establish robust 21st Century projections of global wave climate change. A series of experiments are being conducted based on CMIP-generated wind data.

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Phase 2 (CMIP-5 generation)

COWCLIP phase 2 is a designed experiment, aiming to overcome limitations of phase 1. The experiment is designed to ensure overlap in sample space between different contributing studies.

Currently nine research groups have contributed data to these experiments. The following table below summarizes statistics from 145 projected change simulations using the RCP8.5 scenario for the time-slice 2080-2099. In addition, a further 69 RCP4.5 scenario simulations have been provided, along with all corresponding historical time-slice simulations.

 
Work on this phase is currently ongoing and will be updated accordingly.

Morim, J., M.A. Hemer, N. Cartwright, D. Strauss, & F. Andutta (2018). On the concordance of 21st century wind-wave climate projections. Global and Planetary Change, 167, 160-171. DOI: https://doi.org/10.1016/j.gloplacha.2018.05.005

Abstract: 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 Hs across the Southern Ocean, tropical eastern Pacific and Baltic Sea, and conversely, a decrease of Hs over the North Atlantic and Mediterranean Sea. Furthermore, we observe that projections of H¯s over the eastern north Pacific and southern Indian and Atlantic Oceans lack consensus. Similarly, future projections of extreme Hs 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.

Contributing Studies

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Phase 1 (CMIP-3 generation)

COWCLIP provided the first community projection of global wave climate change. The assessment is based on an ensemble of opportunity with little overlap in sample space by which to assess sources of variance in projected signal.

Hemer, M.A., Y. Fan, N. Mori, A. Semedo & X.L. Wang (2013). Projected Changes in wave climate from a multi-model ensemble. Nature Climate Change. DOI: 10.1038/nclimate1791.
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1791.html

Abstract: Future changes in wind-wave climate have broad implications for the operation and design of coastal, near- and off-shore industries and ecosystems, and may further exacerbate the anticipated vulnerabilities of coastal regions to projected sea-level rise^{1, 2}. However, wind waves have received little attention in global assessments of projected future climate change. We present results from the first community-derived multi-model ensemble of wave-climate projections. We find an agreed projected decrease in annual mean significant wave height (HS) over 25.8% of the global ocean area. The area of projected decrease is greater during boreal winter (January–March, mean; 38.5% of the global ocean area) than austral winter (July–September, mean; 8.4%). A projected increase in annual mean HS is found over 7.1% of the global ocean, predominantly in the Southern Ocean, which is greater during austral winter (July–September; 8.8%). Increased Southern Ocean wave activity influences a larger proportion of the global ocean as swell propagates northwards into the other ocean basins, observed as an increase in annual mean wave period (TM) over 30.2% of the global ocean and associated rotation of the annual mean wave direction (θM). The multi-model ensemble is too limited to systematically sample total uncertainty associated with wave-climate projections. However, variance of wave-climate projections associated with study methodology dominates other sources of uncertainty (for example, climate scenario and model uncertainties).

Contributing Studies