Airbus Defence and Space

The mystery of the monsters from the deep

Tall tales from the sea are not a mariners’ myth, satellites reveal

For centuries, sailors – those that survived to make it back to port – have told terrifying tales of gigantic waves, massive ‘walls of water’ as tall as multi-storey buildings that rise up inexplicably from relatively calm seas and sweeping ships hopelessly into their murderous vortex.

Their claims of towering beasts, however, have always attracted plenty of scepticism from marine scientists, who dismissed these accounts as fantasy, embellished products of the fevered imagination of lonely seafarers just like putative sightings of mermaids or the Kraken (which themselves, let us not forget, do actually have their roots in truth …).

Huge wave south of Durban © Philippe Lijour

Oceanographers pointed to statistical models showing that monstrous deviations from the surrounding sea state are a rarity, occurring once every 1,000 years. They did have in reserve the term ‘rogue waves’, again implying a kind of freakish rarity. All-too-frequent sinkings of often very large ships in unexplained circumstances on the high seas were simply put down to ‘bad weather’. 

Huge wave south of Durban, South Africa © Philippe Lijour

Then, on 1 January 1995, a laser instrument on the rock-steady Draupner oil rig in the North Sea recorded a hit by a giant wave of 26 metres (85 feet) in height, while the highest waves around it measured only 12 metres (30 feet). This objective evidence galvanised oceanographers into paying more rigorous attention to this force of nature. To prove the phenomenon or lay the rumours to rest, in December 2000 the European Union initiated a programme called MaxWave to study these monsters, investigate how widespread might be their occurrence, and to model their genesis and behaviour. As part of the project, the European Space Agency (ESA) tasked two of its Earth-scanning satellites, ERS-1 and ERS-2, designed and built by Airbus Defence and Space, to survey the oceans with their radar and carry out a global rogue wave census.

When they were launched, in 1991 and 1995 respectively, the twin ERS (European Remote Sensing) satellites, built by Airbus Defence and Space, were the most advanced of their time

When they were launched, in 1991 and 1995 respectively, the twin ERS (European Remote Sensing) satellites, built by Airbus Defence and Space, were the most advanced of their time © Airbus Defence and Space

On the look-out for monsters

Freak Wave © NOAA

Freak wave © NOAA

Only radar satellites can provide the truly global data sampling needed for statistical analysis of the oceans, because they can see through clouds and darkness. In stormy weather, radar images are thus the only relevant information available. When they were launched, in 1991 and 1995 respectively, the twin ERS (European Remote Sensing) satellites were the most advanced of their time, putting Europe firmly at the forefront of Earth observation. They both had a synthetic aperture radar (SAR) as their main instrument, which sent back ‘imagettes’ – pictures of the sea surface in a rectangle measuring 10 km by 5 km (6 x 2.5 miles), taken every 200 km (120 miles). These small imagettes – around 30,000 were produced by the two satellites – were then mathematically analysed into averaged-out breakdowns of wave energy and direction, called ocean-wave spectra. The results they produced were startling – during the three-week investigation more than 10 individual giant waves around the globe above 25 metres (81 feet) in height were detected using the ERS satellite technology.

These monster waves are distinct from tsunamis, or tidal waves, which are huge volumes of seawater triggered into motion by earthquakes, tectonic movements or landslides, rolling practically unnoticeably along the surface of the ocean and only unleashing their devastating fury once they reach land coasts. The monster waves scrutinised by the MaxWave project and the ERS satellites are single, monumental walls of water that rise up from apparently calm seas, seeming to suck the energy from the comparative tiddler waves around them, and then shrink back into the ocean as suddenly as they appeared.

It’s official: not fiction but fact

The behemoth waves exist in higher numbers than anyone expected. The satellites had confirmed their existence and widespread incidence. Why they occur is still the subject of much study, and one where satellite technology, with its incredibly precise measuring capability and global overview, makes a crucial contribution.

 

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