Top-roping using 2 ropes tied together - is ice climbing any different from rock climbing ?

I have never been ice climbing, but my friend who has says the following does not work in ice climbing.  My friend cannot remember the reason, and I'm puzzled.

Their claim is that, when top-roping a long route using 2 ropes tied together, it is not possible to avoid having the belayer pass a knot.

In rock climbing the knot passing is easy to avoid by having the climber tie into the right spot on the rope.  E.g. if top-roping a 40m climb using two 50m ropes tied together, tying in 10 meters from the rope's end avoids the need to pass a knot.

This won't work if the belayer is positioned higher than the start of the climb, but my friend says that is not the problem (the belayer is usually lower in ice climbing).

It also won't work if using e.g. 70+30 for a 50m climb, but if my experience with rock climbers is any indication, people happily buy longer ropes to avoid having to do tricks.

So does anyone know what about ice climbing makes it necessary to pass knots when TRing long routes ?

I don't see any reason why a particular TR setup would work for rock climbing and not ice climbing.

You and your friend should go to a crag and set up the ropes like normal. Then hand the climber ice tools and crampons and see what happens. =)

One thing I forgot - letting the 10m end dangle below the climber is more of a problem in ice climbing, since it will get stepped on with crampons...   But surely (?) a Kiwi Coil is easier than passing a knot..

To clarify, my friend's claim is that the belayer must pass a knot.  They don't claim that tying ropes together doesn't work.

Like others have said, there's no reason why Ice vs Rock you'd "have to pass the knot".  My guess is the folk he was climbing with were concerned with "crampons into rope" if there was a "tail", and didn't think about coiling it up and tieing it off.....but as Serge said..just coil it up and tie it (the tail) off to the climber. 

Serge Smirnov wrote:

To clarify, my friend's claim is that the belayer must pass a knot.  

But they don't.