Ocean Turbulence

New York Times, April 19, 1988

British scientists are making waves by measuring them. Their unsettling conclusion: at least part of the Atlantic Ocean is getting rougher. Researchers at the Government's Institute of Oceanographic Sciences have found that wave heights in the northeast Atlantic have increased more than 20 percent since the 1960's. Their analysis, published in a recent issue of Nature, a British science journal, raises the possibility of some significant climatic phenomenon in the Atlantic. However, it is not clear from the British wave measurements whether a similar long-term trend is occurring in the rest of the ocean. Britain is a leader in wave-gauging techniques and in its commitment to the practice. Dr. Ledolph Baer, a wave specialist for the United States National Oceanographic and Atmospheric Administration, said American records generally do not have the longevity or reliability to determine long-term trends. "This is an intriguing observation by researchers who are well known in the field," Dr. Baer said. "It could be very significant. And it's certainly worth looking into and trying to think about."

The Nature article, by David Carter and Laurence Draper, marine physicists at the Institute of Oceanographic Sciences, offers no definitive explanation for the bigger waves. "We really haven't been able to solve this mystery yet," Mr. Carter said. "We're hoping someone else can come up with the answer." The British scientists' study cites wave research done by others in the north Atlantic and the North Sea, but it relies mainly on the institute's wave ship, which is permanently moored off Land's End, the southwesternmost finger of the British mainland. The vessel has been measuring wave heights every three hours, with only a few interruptions, since 1962. It is believed to be the longest running wave recording effort at a single site in the world. Since the 1960's, the biggest waves have risen to 57 feet, from 39 feet. More significantly, the average wave height over the same period has increased to 9 feet, from 7.4 feet. Because their measurements have been made over more than two decades, the scientists are confident their findings reflect a long-term trend that cannot be explained away by seasonal or yearly variations.

Other scientific studies, though not based on as extensive on-site measurement, have also found wave sizes growing in the north Atlantic and in the North Sea. Atmospheric depressions, the main wave producers, often extend more than a thousand miles over the ocean and can generate waves hundreds of miles from where winds are gusting. Accordingly, the British scientists do not believe their measurements are an isolated fluke. At the least, they say, the higher-wave trend is probably similar over a sizable slice of the north Atlantic. "It must be a fairly large-scale phenomenon because the generating mechanism for waves is fairly large scale," Mr. Carter said. ... There is some anecdotal support for the institute's conclusion that the Atlantic is getting rougher. Des Hannigan, a commercial fisherman off the Cornish coast from 1966 to 1980, recalls that the waves did seem to get bigger during the late 1970's. "And my last year out there was the roughest," said Mr. Hannigan, who is now the nature correspondent for the Cornishman, a weekly newspaper in Penzance. "Just talking about it makes me seasick."