And you still don't have the answer?
The weather can get cold and windy. The key to such vacations is to always take clothes you can layer. Long sleeve sweaters over t-shirts, with a thin but waterproof windbreaker on top. Add in a long-sleeve t-shirt in case it gets really chilly.
But normally on a cruise you should not have to pack a jacket or a sweatshirt, because layering works just as well as gives you more options.