Rogue Waves and Freak Waves

I just finished reading Susan Casey's "The Wave," a very good book that mostly describes the big wave surfing community of Laird Hamilton and others, and the quest to surf a 100-foot wave. This part of the book is pretty good, and I enjoyed meeting the characters who risk their lives for that giant wave.

The rest of the book focuses on large waves in the ocean that cripple and sink huge ships. These are truly the rogue waves that can form from seemingly out of nowhere. Their source is not really that strange, but the equations that govern fluid waves are non linear, and therefore are very difficult to predict. It is for the exact same reason that the weather in the atmosphere is so difficult to predict more than a week ahead.

Chapter 3, Schrödinger's Wave, is a nice description of some of the NOAA scientists who study these waves. In the ocean, one of the best mathematical descriptions of these waves is the nonlinear Schrödinger equation, or NLS, whose solutions include so-called "solitary" waves that don't exist as part of a wave "train" like you would see at the beach as the sets roll in. These solitary waves also exist in space, and I have recently investigated how they manifest themselves in oscillations of the magnetic field in the solar win (here). A group in Nice, France, has shown that rogue waves appear in plasmas that are randomly driven and dissipative. And a physicist at the University of Sheffield, in England, Michael Ruderman, has investigated how these freak waves can arise in plasmas.

The only criticism that I have is that Casey tends to get too hyped up about the sizes of these waves. It is true that they are large, but in certain situations, she exaggerates. For example, in the chapter on Lituya Bay, an elliptically shaped bay in Alaska, there was an earthquake in 1958 that triggered a landslide and a large wave. The shape of the bay focused the water, causing it to rise up to a great height, which Casey claims was a 1,740-foot wave. However, while it is true that debris from this wave was found 1,740 feet up the hillside of the bay, it does not mean that a coherent wave was actually that high. A geophysics blog at the American Geophysical Union web site (here) describes it like this

The wave had a maximum run-up height (this is the vertical distance that it ran up the valley wall) of 530 metres. Whilst this sounds extreme, there is clear evidence that this was the case from sediments left by the wave and from the removal of trees by the water. This is the highest coastal wave ever recorded, although this very high run-up zone might be considered to be more of a splash than a coherent wave.

 Casey repeats several times the height of this "wave," but doesn't point out that the wave wasn't really this high. It was still spectacular, though.

I recommend this book to anyone interested in being an armchair big-wave surfer!