Artificial Upwelling and Mixing (AUMIX)

Around the globe there are certain regions of natural upwelling where nutrient-rich deep ocean water (DOW) flows continuously to the ocean surface. These areas are the world¼s most productive fishing grounds. For example the rich fishing grounds along the west coast of North America and South America exist primarily because of the upwelling in these regions. The nutrients brought to the surface by this upwelling increase biological production at the primary and secondary levels.

Researchers have looked into the possibility of a cost-effective means of raising nutrient-rich DOW and distributing it in surface waters to increase the ocean's primary productivity as a means of enhancing open ocean mariculture. A complete realization of open ocean mariculture using nutrient-rich DOW depends on technological advances in physical oceanography/ocean engineering and marine biology.

With funding from the U.S. National Science Foundation and the Pacific International Center for High Technology Research Dr. Liu and his graduate students have conducted research on artificial upwelling and mixing (AUMIX) for the last six years. A wave-driven artificial upwelling device was developed and has been tested in a hydraulic laboratory and in the open ocean off the south coast of Oahu. Model simulation indicates that a single device with a buoy 4.0 meters in diameter and a tail pipe 300 meters long and 1.3 meters in diameter could generate a flow of about 1.0 cubic meter per second in random waves. This rate is sufficient to develop DOW-enhanced open ocean mariculture.

The research team also investigated the mixing and transport of DOW effluent at the surface. It was found that, with proper effluent contol, desirable nutrient-rich plumes of DOW can be established and maintained within the biologically productive zone near the ocean surface. The research also revealed that wave effects on near-field mixing of a buoyant jet can be simulated by an extension of the entrainment hypothesis that relates the rate of inflow of diluting water to the local velocity. This finding was used to modify the popular US Environmental Protection Agency KERNEL model for simulating ocean outfall effluent plume mixing.

Further research is being proposed to study bio-productivity and CO2 transfer in DOW-enriched marine water. Enhanced bio-productivity could help pave the way for commercially viable open ocean mariculture. The study of CO2 transfer across the air-sea interface will provide valuable information on the possible impact of large-scale artificial upwelling on atmospheric CO2 concentration and potential alleviation of global warming.