system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: If the bottom of an iceberg is surrounded by water, shouldn't the iceberg slowly melt? Isn't water warmer than ice?
gpt
Where icebergs form, there is no or almost no temperature gradient between the water and the iceberg, so they can last in those waters for centuries.  Once they float a bit further south (or north) from their formation point, they encounter slightly warmer water and melt.  But some icebergs are enormous - so large that it can take months or even years to melt even in (relatively speaking) toasty water.  The largest icebergs can weigh more than 10 million tons.