Ocean stratification refers to the layering of water in the ocean, primarily due to differences in temperature and salinity. The upper layer, known as the mixed layer, is warmed by the sun and mixed by wind, while the deeper layers, or thermocline and deep ocean, are colder and denser. This stratification affects marine life and ocean currents. The variations in density create distinct layers that can influence nutrient distribution and the movement of marine organisms. Upwelling and downwelling are processes that can disrupt these layers, bringing nutrients from the deep ocean to the surface or vice versa, impacting ecosystems and fisheries.