Professor Walter Munk, ‘The Grandfather of Wave Forecasting’, arguably the greatest oceanographer who ever lived, passed away on February 8 2019 at the age of 101. You may not have heard of Walter Munk. That is, unless you have ever read anything about surf science or wave forecasting, in which case his name will be more than familiar.

“His work influenced many thousands of scientists and, of course, most surfers throughout the world.”

Walter Munk was born in Vienna, Austria around 1920. His parents divorced when he was a child and the family moved to New York. Laster in life he started studying physics at the California Institute of Technology, where he graduated in 1938. He then got a summer job at the Scripps Institution of Oceanography and was accepted for a PhD under the legendary Norwegian oceanographer, Harald Sverdrup.

With the rise of World War II, Munk started working with the U.S. Navy Radio and Sound Laboratory, developing methods for amphibious invasions.

While observing training sessions for amphibious landings in South Carolina, he noticed that the waves were severely interfering with the landing craft as they tried to get onto the beach. Munk convinced Sverdrup to help him develop a method for predicting surf conditions so that allied invasions could have a better chance of succeeding. The Sverdrup and Munk wave prediction technique worked so well that it was used in the 1944 D-Day landings at Normandy, the largest naval invasion in history!

This was, of course, also the first time anybody had devised a way to predict surf, and it paved the way for the research over the following decades that led to the models we all use nowadays. In fact, if it wasn’t for Walter Munk, MSW might not even exist.

In 1947, after all the distractions of World War II were over, he obtained his PhD, and continued to make more ground-breaking discoveries in oceanography. In 1954 he became a full professor of geophysics at Scripps, and continued to work there until his death.

Walter Munk never retired; he kept working as Professor of Geophysics at Scripps Institute until the day he died.

Munk truly was the “Grandfather of Wave Forecasting”. After his work during World War II, he continued his research on wave prediction techniques, with Harald Sverdrup and later with coastal engineer Charles Bretschneider.

Around the late 1940 and early 1950s they developed a really elegant way to predict the waves using the technology available at the time. It was an empirical model, based on hundreds of observations of the resulting wave heights and periods in different combinations of the strength of the wind, the distance over which that wind blows (fetch) and the duration of time it blows. The model comprises a set of equations through which you can calculate the wave height and period by inputting values of windspeed, fetch and duration. It is called SMB theory, after its inventors. Crucially, it laid down the foundations for the research that led to the sophisticated models we all use today.

He made some of the first observations of wave grouping (sets) decades before most people knew anything about surfing. Closely related, he was the first to study those long, tsunami-like surges of water that hit the coast during large swells and storms and that we now know are so important for coastal erosion. He was the first to name them: infragravity waves.

He made some ground-breaking discoveries about the propagation of oceanic swell. In 1963, he headed a group of scientists from Scripps in a fascinating experiment to track swells. They set up a system of six wave-measuring stations in the Pacific over a 10,000-km great-circle route between New Zealand and Alaska. They tracked 12 major swell events from storms in the Southern Ocean all the way up to Alaska. One of the most important findings of that seminal experiment was that the total wave energy in long-travelled swells is attenuated very little. Also, the changing signature of the swell as it progressively arrived at each point clearly demonstrated how the longer-period waves in a swell gradually outrun the short ones – a principle called radial dispersion. All these details and more are explained in the classic film Waves Across the Pacific.

Walter Munk’s amazing career, and his work influenced many thousands of scientists and, of course, most surfers throughout the world.