As a reference point — if only I could find the reference — it has been asserted that there is a detectible somewhat less than 1% variation in tectonic activity correlated to lunar (distance and) position.
The tidal pull of the moon produces somewhat more than 15 cm rise in sea level, and tidal pull itself on the mantle must be at least as great as that on the oceans in some measure, so it is likely that the tidal effect is some orders of magnitude greater than any current weight of ocean due climate effect.
As oceans are much nearer to the mantle than is the moon, though the difference in weight between oceans a century or more ago and now are vanishingly small compared to the mass of the moon, the inverse square of distance implies not just the weight but also the pull of oceans (like the pull of the moon) could be a factor. Still, it has to be tiny.
So, could global climate shifts resulting in redistribution of the weight of the waters in the seas also result in tectonic changes?
The odds are strongly against this being significant, perhaps astronomically so; however, they are not zero if the lunar correlation to tectonic activities is verifiable.
As the odds are not zero, and there are so many uncertainties, this remains in interesting intellectual puzzle especially due the immense costs involved.
Any puzzlers want to take on the challenges of scoping weight and effect of moon vs weight and effect of water, and finding the lunar-tectonic correlations research for reference, might be edutaining.
