Daily sunspot area is anti-alias filtered with a 732d low-pass and re-sampled at annual intervals to match the Jevrejava mean sea level reconstruction. Rate of change of MSL was taken as the annual difference.
The the power spectrum is derived from the chirp-z analysis of the cross-correlation.
The annotations are approximate cursor readings. More accurate values were found to be:
The long period is not accurately detected by Fourier techniques since it is close to the length of the available data. It maybe more accurate to read it from the cross-correlation.