Tidal Curiosities – The Whirlpool of Corryvreckan

Judith Wolf, 1 Sep 2016.

Most people know that the tide rises and falls periodically at the coast but not everyone is as aware of the periodic flood and ebb of tidal currents. These are of particular importance for mariners and need to be taken into account for navigation. Where currents become particularly strong, they can become known as a ‘tidal race’, which can be unnavigable at certain states of the tide.

Around the coast of the British Isles are many locations where a tidal race forms, usually in a constricted channel between two islands or an island and the mainland. In Scotland, between the islands of Jura and Scarba is the famous ‘Whirlpool of Corryvreckan’ – possibly the third largest whirlpool in the world (after Saltstraumen and Moskstraumen, off the coast of Norway). The Gulf of Corryvreckan, also called the Strait of Corryvreckan, is a narrow strait between the islands of Jura and Scarba, in Argyll and Bute, off the west coast of mainland Scotland.

The name ‘Corryvreckan’ probably derives from two words ‘Coire’ which in Irish means cauldron and ‘Breccán’ or ‘Breacan’, which may be a proper noun i.e. the name of an individual called Breccán, although this has also been translated as ‘speckled’ from the adjective brecc ‘spotted, speckled’ etc. combined with the suffix of place – an.

There is an Old Irish text known as Cormac’s Glossary written by the King and Bishop of Cashel, Cormac mac Cuilennáin who died in the year 908. The text is written in the form of a dictionary combined with an encyclopaedia. In it are various attempts at providing explanations, meanings and the significances of various words. At entry 323 it provides probably the fullest description of the Coire Breccáin of the early Irish material:

‘a great whirlpool which is between Ireland and Scotland to the north, in the meeting of various seas, viz., the sea which encompasses Ireland at the north-west, and the sea which encompasses Scotland at the north-east, and the sea to the south between Ireland and Scotland. They whirl around like moulding compasses, each of them taking the place of the other, like the paddles… of a millwheel, until they are sucked into the depths so that the cauldron remains with its mouth wide open; and it would suck even the whole of Ireland into its yawning gullet. It vomits iterum {again & again} that draught up, so that its thunderous eructation and its bursting and its roaring are heard among the clouds, like the steam boiling of a cauldron of fire.’

Corryvreckan is also very close to the island of Iona, famous for St Columba, and some of the tales about the whirlpool relate to this saint and his companions, praying to be spared from falling into it, while sailing from Ireland. In one story St Columba is supposed to have encountered and recognised the bones of one Brecan, supposed to have drowned in the whirlpool with his ship and crew, years before. However, there is some dispute as to whether the location of this event was off Scotland or in another whirlpool off northern Ireland.

More recently, in mid-August 1947, the author George Orwell nearly drowned in the Corryvreckan whirlpool. Orwell had fled the distractions of London in April 1947 and taken up temporary residence to write on the isolated island of Jura. On the return leg of a boating daytrip, Orwell seems to have misread the local tide tables and steered into rough seas that drove his boat near to the whirlpool. When the boat’s small engine suddenly sheared off from its mounts and dropped into the sea, Orwell’s party resorted to oars and was saved from drowning only when the whirlpool began to recede and the group managed to paddle to a rocky outcrop about a mile off the Jura coastline. The boat capsized as the group tried to disembark, leaving Orwell, his two companions, and his three-year-old son stranded on the uninhabited outcrop with no supplies or means of escape. They were rescued only when passing lobstermen noticed a fire the party had lit in an effort to keep warm. Orwell’s one-legged brother-in-law Bill Dunn was reputedly the first person to swim across the 300ft deep, mile-wide channel. Nowadays there are regular boat trips and diving trips for tourists.

As the flood tide enters the narrow area between the islands of Jura and Scarba it speeds up to 8.5 knots (>4m/s) and meets a variety of underwater seabed features including a deep hole and a pyramid-shaped basalt pinnacle that rises from depths of 70 m to 29 m at its rounded top. These features combine to create eddies, standing waves and a variety of other surface effects. Flood tides and inflow from the Firth of Lorne to the west can drive the waters of Corryvreckan into waves of more than 30 feet, and the roar of the resulting whirlpool can be heard ten miles away.

Although dangerous when the flood or ebb tide is running and particularly when the wind is blowing ‘against the tide’ (when choppy seas make it very dangerous), it can be safely crossed at slack water when the weather is calm. This is where accurate tidal predictions come into their own, to identify the safe passage times of slack water, although detailed modelling of these areas of complex bathymetry is still a challenge.