The article is about how much above or below the plane, specifically the central plane of the galaxy we are. Spoiler: We're currently above (north) of the central galactic plane by tens of light years, and still traveling upwards, but it's cyclical and we'll be below the plane again in a few million years.
The Arctic sea floor is releasing Methane Clathrates, i.e. the so-called Methane Clathrates Gun is firing.
As for the two instances of "permafrost", both are melting en mass and that is leading to organic matter that has been frozen and accumulating for millenia to now be decomposed by bacteria, leading to massive methane releases.