The warmer oceans cause more storms to form, thus dumping more snow than usual in the polar regions. All this snow takes longer and longer to melt until eventually it starts sticking year round and the ice caps start to grow.
That's the theory anyhow. Could very well be a bunch of bunk but just wanted to put that out there.
But it would seem to me to be self-regulating. Warming climate causes polar ice caps to melt, causing more storms, causing more snow to fall on the ice caps.
Maybe our planet is smarter than we are.