There are thousands of variables needed to create a precise prediction
But why do you need precise, or even accurate? What you need is believable.
So, start with the current world's map including the ice pack. As you shift Greenland (etc.), shift the pack above it along with it (the ground is acting like an anchor for the ice, so it would move). As it moves, it's opening up space that the current would whittle into. Not a ton, because currents are only one of the proverbial thousands of variables, but some.
Bear in mind that ice grows and shrinks over the year (and decade, and century, there are many cycles). So you might consider asking what time of year you want to base your ice pack on.
Result? A completely believable map.
I think that sometimes we authors get too caught up in the pursuit of technical perfection when, realistically, that level of perfection won't benefit a story, or a game, or anything else at all. If you need a better answer than this, please explain why it's that important. Cheers.