The unit of the power spectrum in the document

[mini-DONG]

Hi,

Nice package! And, I've recently been working on power spectral analysis of ocean data.
While reading the document, I noticed that the units of the two power spectrum density are different:

This image is copied from the Realistic example using outputs from MITgcm section of the document.
They're all power spectrum density, so the units should be the same, should they all be $m^3s^{-2}$?