Rogue Waves by Bloomsbury Publishing

Rogue Waves.indd 2

14/02/2017 17:59

ROGUE WAVES ANATOMY OF A MONSTER

Michel Olagnon Janette Kerr Translated by Roger D Taylor

Rogue Waves.indd 3

14/02/2017 17:59

Adlard Coles Nautical An imprint of Bloomsbury Publishing Plc 50 Bedford Square London WC1B 3DP UK

1385 Broadway New York NY 10018 USA

www.bloomsbury.com www.adlardcoles.com ADLARD COLES, ADLARD COLES NAUTICAL and the Buoy logo are trademarks of Bloomsbury Publishing Plc This electronic edition published in 2017 by Bloomsbury Publishing Plc First published as Anatomie curieuse des vagues scélérates by Éditions Quæ 2015 First published in English by Bloomsbury 2017 Text © Michel Olagnon, 2015 Artwork © Janette Kerr, 2015 English translation © Roger D Taylor, 2017 Michel Olagnon and Janette Kerr have asserted their rights under the Copyright, Designs and Patents Act, 1988, to be identified as Authors of this work. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without prior permission in writing from the publishers. No responsibility for loss caused to any individual or organization acting on or refraining from action as a result of the material in this publication can be accepted by Bloomsbury or the author. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloguing-in-Publication data has been applied for. ISBN: PB: ePDF: ePub:

978-1-4729-3621-9 978-1-4729-4441-2 978-1-4729-4442-9

To find out more about our authors and books visit www.bloomsbury.com. Here you will find extracts, author interviews, details of forthcoming events and the option to sign up for our newsletters.

Rogue Waves.indd 4

14/02/2017 17:59

CONTENTS

Foreword

Preface

The Life of a Wave

Rogue Waves and Honest Waves

An Extended Family of Unlikely Waves

Legends and True Stories

It’s the Wave’s Effects That Count

Getting the Measure of the Measurements

Rogue Statistics

The Scientific Analysis

Managing Without Forecasts

114

Raising Sea Snakes

136

Epilogue

146

Glossary

153

Acknowledgements

155

Index

159

Rogue Waves.indd 5

14/02/2017 17:59

Rogue Waves.indd 6

14/02/2017 17:59

Foreword

ESEARCH INTO ROGUE WAVES is carried out at the highest scientific level, and is of such complexity that it could scare the mariner as much as, if not more than, the waves themselves. However, the world presented to us in this book is not so much one of science and equations, but one of men and women confronted by the sea. To save a mariner exposed to danger, he must understand what exactly is happening around him. The authors’ aim is to enhance this understanding by means of analogies, anecdotes and a demystification of the rogue wave, a phenomenon that many find supernatural and overwhelming. The history, the legends and the basis of scientific research as recounted by the author, along with the power of the elements as evoked by the illustrations, will enable readers to absorb a great cauldron of boiling seas, will help them prepare for encounters they hope never to have, and will satisfy their natural curiosity. They will meet Christopher Columbus; the hero of Antarctic expeditions, Sir Ernest Shackleton; Captain ‘Stay-put’ Carlsen

of the Flying Enterprise and his rescuer Dancy; and the ship’s boy Parker who drew the short straw and was eaten. They will discover a wave more than 500 metres high and the witnesses who survived it, the storm surges which drown holiday-makers on shores around the world, the Three Glories that impressed a whole intake of trainee naval officers, the rollers of the Cape of Good Hope, the tragic end of the Derbyshire, and the desperate ascent of his mast by Alain Gerbault when confronted by a huge wave in good weather. They will accompany the best oceanographers and professors of hydrodynamics in their research, their hopes and their disappointments. And they will learn to love and respect the sea just as I love and respect it.

Charles ‘Carlos’ Claden Retired Tug Captain and Senior Salvage Master

Strong waves pound the cargo ship TK Bremen after it ran aground at Erdeven, on the Brittany coast.

Rogue Waves.indd 7

14/02/2017 17:59

Rogue Waves.indd 8

14/02/2017 17:59

Preface

HIS BOOK IS THE RESULT of a collaboration between a research engineer and an artist, drawing together accounts, analyses and tangible proofs which reduce the gulf between the terra incognita – the unknown land our ancestors filled with monsters – and the everyday world of ocean waves. You will not find here any certainties, only open questions and proposed theories. In fact, confronted with such extremes, we are at the very frontier of knowledge, with no well-marked passage through the questions the subject poses: have the mariners who have met such waves been witness to, or perhaps victims of, an abnormal event, or of a rare but perfectly natural occurrence? Can science explain what we see, or must it be content only to describe it? Experienced pilots sometimes say they fly ‘by the seat of their pants’: all their senses, combined in equal measure with their experience and their knowledge of aerodynamics, help

them to anticipate and correct any deviations off course. The ancient fishermen of the Shetlands, when caught out in fog, put their faith in the moder dy, the wave-mother, an alteration of the wave-train caused by the presence of an island, to find their way home without a compass. The ordinary wave is the one familiar to the mariner. An extreme wave should not be a danger to him; it is only a rogue wave if and because it is unexpected. Our intention is to explore the concept of extreme and rogue waves, to examine how they spring out of the ranks of normal waves, and with what frequency. We hope to acquaint the reader with the culture and knowledge of extreme waves, so that he or she can better understand their mechanisms.

Michel Olagnon and Janette Kerr

A mountainous wave, high enough to overwhelm this harbour wall – yet still not a rogue.

Rogue Waves.indd 9

14/02/2017 17:59

Rogue Waves.indd 10

14/02/2017 17:59

1 The Life of a

Wave

Rogue Waves.indd 11

14/02/2017 17:59

Rogue Waves

nowhere to engulf walkers on a cliff or beach, to fill and sink fishing boats while their crews still work on deck, to smash into the lower decks of oil rigs, to cripple the biggest cargo ships or even break them in two? Everyone knows what constitutes a ‘freak’ phenomenon, but as far as waves are concerned we are only familiar with their external appearance: foam, spray, the powerful movement of water. We can ask a scientist, who may have a few equations to describe the mechanics of a wave or to model extreme cases, but for the layman all this does is replace one mystery with another.

T IS NOT FOR NOTHING that the word ‘vague’ (the French word for ‘wave’) means indefinite, uncertain, indeterminate: any ocean wave, let alone a rare rogue wave, which those on land only see at the moment of its death, is a poorly understood phenomenon. What exactly is a wave?

WHAT ARE WAVES? Watching rollers breaking regularly on the beautiful palm-shaded sand of a surfers’ beach, it is easy to accept that they were created by an invisible storm far across the ocean. But when a winter gale lashes the rocks and scours the navigational marks and lighthouses of the coast, the sea lacks any sense of order. Waves throw themselves around in confusion, climb up on each other, merge and tangle. Here, then, is a mystery: how is it that waves, left to their own devices, are able to order themselves systematically, while everything else, from garden plants to children’s toys, tends towards disorder? There is an even more intriguing puzzle: even at the height of a storm, waves maintain a certain regularity. The largest is only marginally bigger than its little sisters. How can it be, then, that there are rogue waves, looming out of

Rogue Waves.indd 12

He said: ‘You’re really disgusting.’ ‘What does that mean, disgusting?’ Cult reply at the end of Breathless, the emblematic New Wave ﬁlm of Jean-Luc Godard We will begin, then, with an attempt to explain the nature of a wave, and all its varieties, before presenting the whole family, from the best-behaved to the most unruly. We will then have a look at the history of the rogue wave, using anecdotes and first-hand accounts. We will The apparent chaos of a wave breaking on a shore belies the order of the system that created it.

14/02/2017 17:59

The Life of a Wave

go into detail on their effect on ships and marine structures, without which the most extreme waves would no doubt go unnoticed as they range across the ocean. We will then consider the fundamental question: to what extent is the risk of encountering a rogue wave predictable or calculable – can we master the science? To do this we will invite the reader to think about extremes, statistics, theory and probability, while ensuring that everything is straightforward and understandable. We will see how engineers and builders take account of rogue waves, how meteorologists try to alert mariners, and we will ask whether lives can be saved. Finally, we will try to put various popular conceptions into proportion, and suggest several avenues for future research.

A WAVE IS LIKE EVERY OTHER WAVE An ocean wave is like a human being: it is born, takes shape, lives a relatively short life and dies. It is aided by the medium in which it lives: the surface

Rogue Waves.indd 13

When fast-moving waves are forced to break, their energy only has one direction to go – up. of the sea undulates at the slightest stimulus, needing only the smallest encouragement to create a series of oscillations around a point of rest, oscillations which radiate out and only die slowly. The usual stimulus is the wind, but it can also be a sudden movement of the sea bottom, a coastal landslide, something falling from the sky, or an object moving along the surface. Apart from the exceptions, which we will look at later, it is the wind which creates waves. By exerting friction on the surface of the ocean it pushes particles of water away from their point of rest, driven first by the capillary attraction of neighbouring particles, when the movement is very slight, and then by gravity – which tries to maintain a flat, horizontal surface – when the movement is more pronounced. Rather like a pendulum or a satellite, the particles overshoot their point of rest, or revolve around it, unable to stop or rejoin it without a frictional force to slow them down.

14/02/2017 17:59

The action of one bird in isolation does not explain this formation – the same is true of the relation of waves to each other.

The presence of wavelets increases the turbulence of the wind around them, which in turn encourages the growth and coalescing of ridges of water into bigger and bigger waves. The more strongly and the longer the wind blows, the more the waves it generates grow, not only in height but also in wavelength and period. However, an ocean wave cannot grow higher beyond a certain steepness – the ratio of the height of a wave to its length – without either lengthening or breaking. As soon as they are created, waves begin propagating. For every wave, its medium – in this case water – oscillates on the same spot. It is only the movement back and forth, the oscillatory force, which advances. It is just like sound, which obviously does not carry the air itself from the source to the hearer. In much the same way the sound waves themselves remain invisible. As long as the ocean waves remain in an area subject to wind, the process of growth is likely to continue. The extent of this area, the fetch, influences the size as much as the wave length, or spacing, of the waves generated. A wave stops growing either when it leaves the area of fetch and arrives at a part of the ocean where the wind is insufficient to maintain the growth, or else when the dissipation forces – escape from

Rogue Waves.indd 14

Rogue Waves

the fetch and wave-breaking – equal the energy input of the wind. For ocean waves within the fetch zone, specialists talk of a wind sea, while for those which have exited the fetch zone they use the term swell. A swell weakens only slightly as it crosses the ocean. Not only does one see, therefore, swells from the Furious Fifties arriving at Réunion Island, near the Tropic of Capricorn, but in New Zealand one can even measure swells emanating from Alaska. Waves only expire when they break on a coastline, when they lose their energy trying to shift pack-ice, or when they are dispersed by winds, currents or other waves.

WAVES AND WINGS What we actually see of the ocean wave is only one particular aspect of what we cannot see: the primary wave motion. This primary wave motion, which is born in a storm and dies hitting a distant shore however many days later, is, to the visible ocean wave which everyone can identify, what an individual starling is to the shape formed by a flight of birds in the sky: the basic component which only a detailed analysis can isolate among all the other birds. It is necessary to understand it in order to explain what we see, but it takes no account of that individual bird or the one that precedes or follows it. As with this analogy, we do not see The Great Wave (Hokusai).

14/02/2017 17:59

The Life of a Wave

each of the individual undulations caused by the wind, but only the combination of all those which happen to be at the same spot at the same moment. The more homogenous all the primary wave motions, the quicker the ocean waveâ&#x20AC;&#x2122;s formation and movement. Similarly, the ocean wave as seen by an observer will have a lifespan and spatial extent which are longer or shorter, although never particularly extensive. The orders of magnitude here are in the region of a few minutes and several nautical miles, a far cry from the ocean crossings which are the preserve of the primary wave motions themselves. And just like the brief and amazing shapes created by a flight of starlings, an individual ocean wave, for example a rogue wave, will quickly disappear. Only a swell coming from a long distance, or one initiated in shallow water, and whose components have become separated or have adopted a fixed configuration and stopped their endless combining and recombining, show some stability in time and space.

Rogue Waves.indd 15

FENG SHUI (WIND AND WATER) We have described the way wind creates waves. The longer and stronger the wind, over a large area, the higher and longer the waves it generates. However, some ocean waves move out of the area in which they were formed, while the energy of the remaining waves is dissipated by their breaking and tumbling; and so, after a while, in a constant wind, a point of saturation is reached, a kind of equilibrium. In order for the wave height and period to continue increasing, the wind must strengthen. If the storm eases, breaking waves and white horses disappear and the ocean waves continue to propagate in the direction that the wind has sent them. Since there are scarcely any intrinsic factors which will deaden the wave, the energy will continue to propagate until it meets an obstacle, such as a coastline. Ocean waves may be born in a storm and only lose that energy days later â&#x20AC;&#x201C; and thousands of miles away â&#x20AC;&#x201C; when they meet an obstacle, such as a shoreline.

14/02/2017 17:59

This groundbreaking book demystifies the terrifying phenomenon of rogue waves, revealing what causes them, what can be learned from past encounters, and how to cope with them.

Buy Now www.bloomsbury.com