"Czerski... frames the ocean as a , the blue machine, driven by the difference in solar heating between the equator and North and South poles, with complications from tidal forces, wind, differences in salinity—which, like temperature, affects density—and shape of continental land masses and undersea crust. They generate complex effects... in a great, layered mass of water that is in constant motion. ...It all adds up to a persuasive case that Earth-dwellers need to understand the ocean and work with it..."