Artificial upwelling is a geoengineering strategy that involves bringing relatively nutrient-rich waters from depth up to the surface ocean to stimulate phytoplankton activity and draw down atmospheric CO2.
This strategy involves the use of wave-powered ocean pumps to bring nutrient-rich deep water to the surface to stimulate plankton blooms (Karl and Letelier, 2008). Initial experiments with the wave-powered pumps were performed at Station ALOHA ~80 miles off the coast of Oahu.
This strategy proposed by Lovelock and Rapley (2007) involves the deployment of thousands of plastic tubes (~300-600 feet long and ~30 feet in diameter) in the oceans, bridging nutrient-poor surface waters with colder, nutrient-rich waters at depth. In addition to mixing via natural wave motion, a one-way valve would pump nutrient-rich deep water through the tubes to the ocean surface, stimulating phytoplankton activity.