Speaker: William Young (Scripps Institution of Oceanography , UC San Diego)

Title: “Long-range propagation of ocean swell”

Abstract: The global propagation of ocean surface waves is a happy example in which a linear theory (almost) explains ocean observations. I’ll review the history of this problem, starting with early  work on wave prediction in World War II. The most conspicuous failure in the classic work  is  that  wave sources inferred by great-circle backtracking  are often as much as 1000 kilometers away from the storms reported on weather maps; a few sources seem to  fall on the Antarctic continent. We have reproduced these old observations  using modern recordings of swell from deep-water pitch and roll buoys and  find  that the modern observations are most often in excellent agreement with the location of large storms on weather  maps of the Southern Ocean. However there are still a few puzzling  failures of great-circle backtracking  e.g., in one case,  the direct  great-circle route is blocked by the Tuamotu Islands and  the inferred source falls on New Zealand. I’ll explain the frequent  mirages in the old observations, and the occasional mirages in the modern observations,  as resulting from  refraction of ocean surface waves by currents. [Background Reading]