Ijaz Durrani

The disappearance of the Arctic sea ice would be irreversible without global tempeatures dropping below those of today, which would be difficult to achieve because the without the sea ice the global albedo would be reduced by ~5% causing warming. This will happen abruptly due to ice albedo positive feedback.

This has been explored in extensive detail elsewhere, start at https://en.wikipedia.org/wiki/Tipping_points_in_the_climate_system and then work your way backwards for specific pieces of relevant information.