Sailors' tales of monster waves were dismissed as myths until 1995.
For centuries sailors described sudden walls of water far bigger than the surrounding sea, and scientists mostly waved them away. Then, on New Year's Day 1995, a laser on a North Sea gas platform measured a wave 25.6 metres high in seas averaging about 12. Rogue waves were real.
Oceanographers define a rogue wave as one more than twice the significant wave height, the average of the highest third of waves in a given sea. For generations, ship designers relied on a statistical model in which wave heights cluster tightly around that average. In a storm with 12-metre significant waves, it predicted a 30-metre wave only once in 10,000 years. In 1826 the French naval officer Jules Dumont d'Urville reported 33-metre waves in the Indian Ocean and was publicly ridiculed; the prevailing view held that no wave could exceed about 9 metres.
The Draupner platform, about 160 kilometres south-west of Norway, changed that. At 15:24 on 1 January 1995, its downward-pointing laser recorded a wave with a maximum height of 25.6 metres and a crest 18.5 metres above still water, backed up by other sensors and by damage to the platform. Research surged. In 2000 the research ship RRS Discovery measured individual waves up to 29.1 metres west of Scotland that no forecast had predicted, and in 2004 European satellites found more than ten waves over 25 metres in three weeks in part of the South Atlantic. Rogue waves are now thought to occur somewhere in the oceans many times a day.
Their causes are still debated, and there may be several. Currents running against the waves can squeeze them together, as off South Africa's Cape Agulhas. Coastlines and seabeds can focus waves. Wave trains crossing from different directions can combine; in 2019 researchers recreated a Draupner-like wave in a lab using waves meeting at 120 degrees. Nonlinear effects may let one wave steal energy from its neighbours. Some researchers argue many 'rogues' are simply rare but expected outcomes of ordinary wave statistics, though whether that explains the very largest is unknown.
The stakes are practical. The freighter MS München vanished in 1978 with signs of a wave strike more than 20 metres above the waterline, and a 2001 analysis concluded the bulk carrier Derbyshire, lost in 1980, was almost certainly destroyed by a rogue wave. A NOAA catalogue lists more than 50 historical incidents probably linked to them. Yet as of 2016, one of the world's largest ship-certification bodies still made no explicit allowance for them in its design principles.
Source: Wikipedia — Rogue wave · Text summarised from Wikipedia (CC BY-SA 4.0)
