Citation: Vásquez-Bedoya, L. F., A. L. Cohen, D. W. Oppo, and P. Blanchon (2012), Corals record persistent multidecadal SST variability in the Atlantic Warm Pool since 1775AD, Paleoceanography, doi:10.1029/2012PA002313, in press.
[updated post 27th Oct, clarification of plot, see comments, was not intended as a formal work]
Read a little on the net, noticing Rog had posted a link to GWPF giving a link to a dataset
On looking GWPF, broken link, figured and reported it, pulled the small dataset. Odd moment thing is tell software here to go do a quick look, only takes a few seconds, and see what gives.
The results tweaked my interest when I looked at the structure. I decided to try a couple of daft things, never know what insight will fall out. This was a case of keep on simplifying.
Second try… definite boggle at the result, never seen this before and is curious enough to warrant an article, quicker anyway that than trying to put plots in a comment.
(note: I am not saying this is a fixed entity, this is pondering, something like this might appear often)
The match is no big deal except for one thing, this has mimicked what seems to be a ~55y wave, perhaps akin to the much vaunted 60y and yes it matches that more or less.
A twist, you are seeing pure modulation products. It is actually a pair of closely spaced sines producing a product. This is what the software did when told to use just one generator but allowed to use modulation. There is no 55 year at all.
It is a pair of ~110 year producing sum and difference product, one being 55y. The other one? This will create some interest
Pasting, 54.9 and 8229.9, comes from 110.53 and 109.07
Maybe, needs some digging
“The ~3 m cycle corresponds to individual paleosols, with a period of 7–8 k.y. This period is similar to millennial-scale sub-Milankovitch cycles found in marine and lacustrine successions of Pliocene–Pleistocene age.”
Whether such a thing could be found in such a tiny dataset (in time) seems unlikely. Might just be noise playing games.
We know there is circa 100 year in many datasets so that is not a great surprise however it is worth keeping in mind deVries is a loose spectral construct out to very long periods. A commonly mentioned one is ~200y so these ~110y could be to do with the second harmonic.
There seem to be many of these weak-strong-weak-strong waveforms around so having one produced by modulation might be an area ripe for something to have a good think and look. Keep in mind though there has to be mechanism, can’t have effect without a rational way it could happen.
zip archive contain an .ods spreadsheet is here Yucatan-coral (model is live and can be extended to see the longer waveform, change output sample rate or extend by copy/fill)