Global and hemispheric marine temperatures for 1856--1986 have been subjected to harmonic analysis. We investigated a prominent 22-year peak in the Fourier Transform by subtracting from the raw data the inverse transform of the periods longer than 26.2 years (the fifth harmonic). The shorter periods that remain are dominated by the 22-year period the approximate amplitude and phase of which we determined with a 10-year running mean filter. We suggest that this period may be related to the solar magnetic cycle. The low frequency data show a major dip centered around the period 1905--1910. The results should be considered in any analysis of global marine temperature for trends. ¿ American Geophysical Union 1989