As a body is brought from the equator at sea level to the north or south pole, what is the effect on its m?

I don't think that its m will change very much, however its volume may increase due to decomposition and bloating. Unless you plan on keeping the body refrigerated the whole time. It may start to smell a bit. You may loose some fluids by seeping out of the body bag which will decrease the m slightly. You do have a body bag dont you?