Upwelling refers to an oceanographic phenomenon where deep, cold and nutrient-rich water rises to the surface, often in response to changes in wind patterns or tidal movements. This process can lead to increased primary productivity as the upwelled waters provide a source of nutrients for phytoplankton growth. Upwelling also plays an important role in regulating global climate by transporting heat and carbon from the surface to deeper layers of the ocean, thus helping to mitigate the effects of climate change.