public meeting gaeilge Inis Meáin

Halla Naomh Eoin Public Meeting (Inis Meain)
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26/11/2019 00:00:00

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).

On 2 October 2019, Professor Frédéric Dias gave an official presentation of the ERC project HIGHWAVE. There was a variety of guests including the UCD VP for Research, Orla Feely, the head of the School of Mathematics and Statistics, Brendan Murphy, and representatives of the following institutions: Met Eireann, Commissioners of Irish Lights, Royal Irish Academy, Irish Air Corps, Marine Institute, ICHEC, The Office of Public Works. Several members of UCD College of Engineering and Architecture, as well as the Wave Group led by Professor Dias, also attended.

presentation 021019Professor Dias explaining the occurrence of wave breaking.

Professor Frédéric Dias spent a couple days on Inis Mór on 17/18 September to give the first official presentation of the HIGHWAVE project. The presentation took place at Halla Rónáin, Inis Mór. The project was very well received. The audience showed strong interest and offered support. The project will bring a lot of benefits to the islanders. Together with Arnaud Disant, the CTO of the project, Professor Dias continued the recon work for the future deployment of environmental sensors. Arnaud and Frédéric had a meeting with the harbourmaster. Later in the fall, Frédéric will also present the project on Inis Meáin and Inis Oirr.

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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.

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Marine Forecasts blog articles are community restricted articles, aimed to researchers, students, lecturers but also the community of the Aran Islands.