Ireland's Atlantic nearshore coastal waters experience storms several times every year. Over the last few Winters/Springs, the UCD Wave Group has deployed a Teledyne Sentinel V acoustic Doppler current profiler (ADCP) device into these waters to measure the sea state over a period of months, in the hope of observing these stormy conditions.
In our new paper in Scientific Reports, we present results from two such storms. One was from our 2015 measuring campaign off Killard Point, and the other from the 2017 campaign off the Aran Islands. We analyze the non-stationary surface-elevation series and compare the distributions of crest and wave heights observed with theoretical predictions based on the Forristall, Tayfun, and Boccotti models. Adapting and applying these models in the nearshore, and compensating for the significant variability of both sea states in time, was a novel approach.
The largest nearshore waves observed during the two storms do not exceed the rogue thresholds as the Draupner, Andrea, Killard or El Faro rogue waves do in intermediate or deep-water depths. However, the story does not end here. Our analysis reveals that modulational instabilities are ineffective, third-order resonances negligible and the largest waves observed here have characteristics quite similar to those displayed by rogue waves for which second order bound nonlinearities are the principal factor that enhances the linear dispersive focusing of extreme waves.
Wave measurements and statistics in the nearshore is a challenging topic, with many new and exciting results yet to be discovered!

Giant rogue waves on the ocean are a mysterious phenomenon as much the stuff of legend as of science. Despite much anecdotal evidence of their destructive power, their scientific study has proven elusive, mainly because of the danger and difficulty of making measurements in the natural environment of the open sea. This changed dramatically in 2007, however, when researchers showed that injecting powerful ultrafast laser pulses into an optical fibre could generate similar large amplitude waves – but waves of light and not of water.

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Figure above: Timeline illustrating the parallel developments in fibre optics (top) and hydrodynamics (bottom).

A storm in 1953 halted the construction of the slipway at Gort Na gCapall on the Aran Islands and also sank the Princess Victoria in the Irish Sea when “the stern gates to the car deck were forced open in heavy seas”, with the loss of 132 people (The Irish Times, 5 June 2003, and BBC News, 1 January 1953).

Williams and Hall (2004) document eyewitness accounts from Gort Na gCapall. The storm caused the total destruction of the construction machinery and a large number of megaclasts (up to 2 m in length and 15 m above sea level) were transported so that there was no longer access to the slipway for boat launching. Waves reached breaking heights of approximately 12 to 15 m.

On 16 August 1852 a “Melancholy Accident” occurred at the Glasson Rocks on Inis Mór resulting in the loss of fifteen lives. A group were fishing on the cliffs when “ a sudden swell of the Atlantic swept them off, when they perished before the slightest assistance could be rendered” (The Galway Vindicator, 18 August 1852).

Academia Europaea was founded in 1988 as an international, nongovernmental association of individual scientists and scholars from all disciplines, who are experts and leaders in their own subject areas as recognised by their peers. Today Professor Dias has delivered a lecture on waves...

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The lecture entitled “The fascination of ocean waves” was delivered at 2.00 p.m. in the Congress Centre of WUST (building D-20).