I’m guessing the tub is on an exterior wall which is pulling out in the winter time. It is cracking because the upper tile”surround” looks like it was not installed correctly on to the tub flange. Most likely the upper surround will need to be removed and installed correctly otherwise this will continue every winter.
This, the tile walls are not installed correctly and not overhanging the tub flange which itself can cause water issues behind the wall. I would also be curious as to what waterproofing method was used. Lots of reasons why tile is not overhanging, from improper tub install to improper tile install or both.