[Thrymr]

The parent post is correct about the slowing. The land ice is (mostly) at high latitudes, and the meltwater tends to raise sea level, which moves the mass to lower latitudes, hence farther from the axis of rotation. Thus warming slows the Earth's rotation as its moment of inertia increases.

The parent post is incorrect about getting it "back" however; leap seconds are added because the rotation is slowing (a "day" is getting longer). More ice caps melting will lead to more leap seconds, not fewer (or negative).