I am not an ocean scientist but from what I read, the water in the deep Pacific has seen sunlight last when Charlemagne was Holy Roman emperor, the Song dynasty ruled China and – coincidentally – the Medieval Warm Period started. We are measuring the warmer waters from a Warm Period from about 1000 years ago. And the world goes bonkers. It pays to read up on mixing patterns in the deep oceans.
The ocean is heating up faster than previously thought, according to new research out this week, and that might help explain the recent spate of historic hurricanes and decline in a number of marine species.