Advancing the yard-stick on that paper
> "ocean dynamics is essential to explain the equatorial SST variations, while air‐sea fluxes control the off‐equatorial SST anomalies. "

Here is a chart supporting an annual impulse driving AMO. An example of [double-sideband carrier suppressed modulation]( It's not quite as obvious as for ENSO or PNA, but the long-period sidebands are distinct.


The way to read the chart is to fold the frequency spectrum from 0 to 0.5/year onto the reversed spectrum from 1.0 down to 0.5 year. Across the range, the correlation coefficient is above 0.5 which is highly significant.