Putting it in the sun is a good method. Resist the urge to chip at it with something hard - that will likely just damage the interior plastic.

Also, it’s possible that the fridge seal is not the problem. There should be a vent where cold air from the freezer enters the lower fridge area. Make sure that’s clear. Otherwise the cold air is just staying in the freezer, so you turn up the cooling to make your fridge cold and the freezer gets extra cold. If that’s what is happening then this is the time to rectify that.