Because it's a totally new thing for the ocean to grow warmer as one progresses southward from the Arctic.
He needs a companion for the trip. Maybe send a polar bear with him........ or worse, send algore.
This is an idiotic idea. Icebergs don’t just melt, they deteoriate. This means that an iceberg is not a solid block of ice but a bunch of ice pieces pressed together. As the berg moves south pieces of ice fall off. Under the right conditions, it will roll over. May the Lord have mercy on his soul.
Some times you could pull a ship up close to a berg, blow the ships horn, and a large chunk of ice would fall off the berg.