HOW can Atlantis sink?

Hello my brethren,

Has anyone ever posted about HOW Atlantis can submerge itself? Its been done at least twice In Canon, so much so that McKay says there's an existing subroutine in place to execute the submersion, but how does it work?

Open to discussion, but I personally believe it's a form of low level thrusters, scattered about the city, that operate as almost gravity engines. Like anti inertial-dampeners, RCS thrusters, as we've seen the City can manoeuvre and turn in a vacuum.

If these thrusters can fire upwards, and negate the buoyancy of the city, than it would naturally sink under its own weight. And a small pulse from the Stardrive can lift it again.

I think it makes sense, and it's cool. Thoughts?