[TonyG (OP)]

I read on other topics that the melting of the polar caps should not affect the Earth's
rotation, and would like to know why - The Earth spins through space like a giant gyroscope; presently a large mass is located at the poles (the Polar ice caps) which
will be evenly distributed around the Earth as the Polar caps melt: surely this redistribution of mass should have some effect on the Earth's rotation?

[yor_on]

I think you are right, the ice transforms into free flowing water getting distributed all over the world.
And it is happening quite abruptly too historically seen.
As well as the world is wobbling, not only rotating:)
http://www.time.com/time/magazine/article/0,9171,891454,00.html

And then we have the magnet field, will that be affected too if Earth change its angle?
On the other hand, if the ice disappears, chances are good(?) that we'll have 'bigger stuff' to worry about.
Like not getting 'wiped out' from this Earth.

Check out CO2 and Methane-Cycles as well as Methane deposits.