Earlier this week there was embarrassment in Donegal. Three hundred surfers had arrived for the prestigious Surfing Championships, and unusually for Donegal, there was no surf. The Atlantic, it seems, was like a mill pond, and resembled the scene in Alice Through the Looking Glass:
The sun was shining on the sea, shining with all his might;
He did his very best to make the billows smooth and bright.
Looking at the weather map, the immediate cause of this inconvenience was not difficult to find. An anticyclone lurked nearby, which meant that there was very little wind, and any wind there was, was blowing from the east offshore, with insufficient "fetch" to have any significant effect upon the water. And the weather over the ocean to the west was quiet, too, so no swell came rolling from the Atlantic. Of course the organisers were unlucky. September is often quite a windy month - and where there is a wind there must be waves. And they were doubly unlucky when one considers that over the past 30 years or so, the Atlantic, for reasons still as yet unknown, has been becoming wavier.
It is common experience that there is a link between the wind and waves. When the winds are light or calm, the sea is often smooth, or nearly so. If the breeze increases, small ripples or "cats-paws" appear, and with a strengthening wind regime the waves gradually but steadily increase in size. Another factor which determines wave-height is what we call the fetch - the distance available for waves to form. Over the open sea waves grow and grow over hundreds of miles as they are pulled along the surface by the wind that generates them; in an enclosed area like the Irish Sea, on the other hand, there is insufficient space for waves to reach their full potential. And finally the duration of the wind is critical; the longer a spate of stormy winds persists over a given stretch of water, the bigger grow the waves.
Now observations show that since the early 1970s, the average height of North Atlantic waves has increased to 25 per cent above its previous value. But what is more extraordinary, is that that the waves have waxed without any corresponding rise in average wind speed. One possible reason being explored is that North Atlantic winds over the last three decades, while showing little variation from normal in their average strength, may have blown more consistently from certain directions, allowing them time and opportunity to build waves of more substantial height. But no one really knows.