Upwelling is the process of cold, nutrient-rich water moving up from the deep ocean to the surface. This can occur when wind blowing over the surface of the ocean pushes surface water away, causing the deeper, colder water to rise up to replace it. Upwelling is important because it brings nutrients from the deep ocean to the surface, where they can be used by phytoplankton and other primary producers to support the growth of other marine organisms. Upwelling is a major factor in the productivity of marine ecosystems and plays a key role in the global climate system.