Ron Smith continues Yale's Atmosphere, the Ocean and Environmental Change course with a lecture on what makes ocean water stable and how the atmosphere reshapes it. He explains that stability requires density to increase with depth, and that density itself depends on temperature and salinity, with cold salty water sinking below warmer, fresher water. The lecture works through ocean depth profiles, salinity patterns, and the physics of stability before turning to atmospheric forcing: how heat gain and loss, precipitation and evaporation, and wind stress push and reshape surface waters. Chapters move from depth profiles and salinity through density and stability calculations to three specific forcing mechanisms, heat exchange, moisture balance, and wind-driven stress. Recorded in Fall 2011 as part of Yale's open course GG 140, the talk is built for students already following the course but stands on its own as a clear walkthrough of ocean physics fundamentals.