Projected changes in significant wave height toward the end of the 21st century: Northeast Atlantic

Abstract

Wind field ensembles from six CMIP5 models force wave model time slices of the northeast Atlantic over the last three decades of the 20th and the 21st centuries. The future wave climate is investigated by considering the RCP4.5 and RCP8.5 emission scenarios. The CMIP5 model selection is based on their ability to reconstruct the present (1971–2000) extratropical cyclone activity, but increased spatial resolution has also been emphasized. In total, the study comprises 35 wave model integrations, each about 30 years long, in total more than 1000 years. Here annual statistics of significant wave height are analyzed, including mean parameters and upper percentiles. There is general agreement among all models considered that the mean significant wave height is expected to decrease by the end of the 21st century. This signal is statistically significant also for higher percentiles, but less evident for annual maxima. The RCP8.5 scenario yields the strongest reduction in wave height. The exception to this is the north western part of the Norwegian Sea and the Barents Sea, where receding ice cover gives longer fetch and higher waves. The upper percentiles are reduced less than the mean wave height, suggesting that the future wave climate has higher variance than the historical period.

Future Wave Conditions of Europe, in Response to High‐End Climate Change Scenarios

“…Our work shows an overall reduction in the mean wave height but with increased extreme waves on (1) west of Portugal and (2) north of 60°N (related to retreating sea ice). Although only a single model is used in our work, it shows results consistent with the multimodel analysis of other authors (e.g., Aarnes et al, ). Gallagher et al () also projected an overall decrease in annual and seasonal mean SWH around Ireland.…”

“…A reduction in mean SWH is not incompatible with an increase in extremes, rather, these results suggest that the PDF of wave heights may be widening (leading to longer tails in the distributions). Aarnes et al () also project a decrease in mean SWH of the order of 10% in the Central North Atlantic by the end of the century. They also note that the upper percentiles of future wave height have a higher variance than the mean climate, which is consistent with our findings here.…”

“…They also predict that there will be increased uncertainty in extreme wave climate in the future. Aarnes et al (2017) evaluate changing wave conditions in the Northeast Atlantic, forced by six different climate models (including EC-Earth, used here). Our work has elements in common with this approach, and we would like to acknowledge their contribution as informative to this study.…”

Contributions to 21st century projections of extreme sea-level change around the UK

“…Our projection of a decrease in mean SWH agrees with the results of Aarnes et al (2017), who also note a smaller reduction in higher percentiles of SWH, suggesting an increase in the variance. Bricheno and Wolf (2018) discuss an alternative metric of wave changes, based on the mean of twenty annual maxima in SWH at the beginning and end of the 21st century.…”

Increased Winter‐Mean Wave Height, Variability, and Periodicity in the Northeast Atlantic Over 1949–2017

“…the next decades, with more extreme winters as described in Figures 4b, 4c, 4e, and 4f. However, most of the existing climate models indicate that there will be no increase in winter Hs in the northeast Atlantic or even a decrease as stated in Hemer et al (2013), in the frame of climate change even for the worst-case emission scenario (e.g., Aarnes et al, 2017;Wang et al, 2014). A notable exception is the study of Zappa et al (2013) who showed a systematic increase in the number of European extratropical cyclones with increasing emission.…”