Impact of extratropical cyclone intensity and speed on the extreme wave trends in the Atlantic Ocean

This work analyses the extratropical cyclone-related extreme waves in the ocean surface and their trends in the North and South Atlantic Oceans. Atmospheric and ocean wave products are obtained from ERA5, from 1979 to 2020 with 1-hourly outputs, covering 42 years with the present climate changes evaluated by the difference between the two 21-years-time slices. The cyclones are tracked through the relative vorticity at 850 hPa and then associated with extreme wave events using an automated scheme that searches for an extreme wave region 1500 km from the centre of the cyclone, following criteria that exclude possible swell dominated events. The hot spot regions of cyclone-related waves occurrence found by the method agree with previous studies and relate to the cyclogenesis region, and storm track orientation. Most cyclones associated with extreme wave events are generated in the western boundary of the domains. The east-poleward side of the ocean basins presents the highest density of occurrences related to the higher density of cyclone track and the dominance of more mature stage cyclones while in the west side prevail systems on developing stages, with notable propagating fronts and consequently, lower wind persistence. The storm track variations alone cannot explain the observed changes in the wave occurrence during the period due to the lack of statistical confidence. However, the wave occurrence responds to changes in the cyclone intensity, modulated by cyclone displacement speed. Regions with an increase of extreme waves are related to the effect of more intense cyclones or cyclones with slower propagation, being the last associated with a longer interaction of winds with the ocean surface.