Even before you lose speed, the torque will go up as the drag on the blades increases.
Sikorsky has a very good video on blade icing (starring Pprune's resident ace from space, Nick Lappos) which I saw at FSI recently. Dunno where else you could see it.
It was enough to give me a scare, having always been told to watch for the first signs of ice on the Huey's wiper blades. By the time you see it there, you are already in deep 5h1t.
