When I was in Antarctica, I saw a few icebergs that had linear voids where ice melted out. These were typically icebergs that flipped or tipped on their side. The sections melted when that part of the iceberg was underwater. These voids can fill up with sea water that's rich in algae, creating the striped effect you see in this image.
For more information, see Snopes on Striped Icebergs.
Thanks to The Wanderer for this tip!