Lecture 4: density, convection, and ocean structure (chapter 6) Convection is one way of transferring heat. Pushing the crust left and right: forming plates. Diverging plates = two plates moving apart. Converging plates = two plates moving together. The region where two plates collide is called a ___. Convection in the earth"s atmosphere drives local to global circulation. During the daytime coastal winds are usually from the sea towards land. Gulf stream = warm water current flowing north off the east coast of us. Heated at the equator (80 degree fahrenheit) Evaporated off the further north it travels. Maximum density b/c cold and salty (north atlantic deep water) Temperature: thermal expansion, cold water denser than warm. Salinity: evaporation/precipitation, ice formation and melting, river water, salty water denser than fresh. Where most of photosynthesis occurs in the ocean. The pycnocline is a region where the density rapidly changes. The thermocline is where the ocean water rapidly changes temperature and density.