No. 113: Sep-Oct 1997
We have touched on this subject before. (SF#84/279) We now have more precise data.
Wave-height measurements at the Seven Stone Light Vessel, anchored in the northeastern Atlantic, show that wave heights have increased 2.4 centimeters/year during the period 1960-1985. This is not a trivial amount. At this rate, waves a century from now would be 2.4 meters (about 8 feet) higher. Many existing coastal structures will be smashed to bits. All this is over and above any effects from rising sea levels.
The records from the Seven Stone Light Vessel are corroborated by an analysis of more then 20,000 wave charts of the North Atlantic drawn between 1960 and 1988.
It therefore seems clear that something unusual is going on in the North Atlantic. One would suspect increased winds, but velocities measured at Seven Stone have remained constant while wave heights rose. It is concluded that the bigger waves are not generated by local winds; rather, they are swells that have been created thousands of miles away. The cause of these larger swells now affecting the entire North Atlantic is not known. The authors of this paper are forced to conclude with:
"It should be noted that so far it has not been possible to attribute the observed change to either an anthropogenic cause or to natural climate variability on decadal time scales."
(Bouws, E., et al; "The Increasing Wave Height in the North Atlantic Ocean," American Meteorological Society, Bulletin, 77:2275, 1996.)
Reference. Other unusual wave phenomena are cataloged in Chapter GHW in our Earthquakes, Tides. For information on this volume, go here.
Atlantic wave heights, 1960-1988.|
1, 10, 50 percentiles.
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