The Spectrum of Sea Level from 4 to 40 Years

Maximum entropy spectrum analysis of 33 tide-gauge records spanning the late 19th and 20th centuries yields persuasive evidence for the 18.6-yr lunar-nodal term and a heretofore undetected solar-cycle signal in sea level. The mean period and standard deviation (sd) of the observations are TL= 18.5±1.1 and Ts= 10.9±0.6 yr, respectively, and each has an average amplitude of roughly 9 mm. Additionally, an apparent signal of unknown origin with Tu= 6.3 yr and Au= 14 mm is evidenced.