Older waters have more silicate, therefore.
The movie loop shows the location of waters at 3000 m depth with progressively higher Si concentrations. The lowest values are found in the North Atlantic, where cold, low Si waters sink into the deep sea. These are the youngest deep waters. Increasing Si concentrations are found through the South Atlantic, around Antarctica and up into the Indian and South Pacific Oceans. Waters with the highest Si are found in the North Pacific.