Research progress in artificial upwelling and its potential environmental effects

Artificial upwelling, as a geoengineering tool, has received worldwide attention because it may actualize ocean fertilization in a sustainable way, which could potentially alleviate the pressures on the fish stocks and human-driven climate change in the ocean. We reviewed the current knowledge on the development of an artificial upwelling system and its potential environmental effects. Special attention was given to the research progress on the air-lift concept artificial upwelling by Zhejiang University. The research on artificial upwelling over the past few decades has generated a range of devices that have been successfully applied in the field for months. Based on field experiments and the associated modeling results, part of them reported positive effects on increasing primary production and enhancing CO2 sequestration. However, as a significant disturbance to the environment, especially for large-scale applications, the uncertainties related to the potential effects on ecosystem remain unsolved. Zhejiang University has overcome the technical challenges in designing and fabricating a robust and high efficiency artificial upwelling device which has been examined in two field experiments in Qiandao Lake and one sea trial in the East China Sea. It was investigated that cold and hypoxic deep ocean water (DOW) could be uplifted to the euphotic layer, which could potentially change the nutrient distribution and adjust the N/P ratio. Both simulation and field experiments results confirmed that utilizing self-powered energy to inject compressed air to uplift DOW was a valid and efficient method. Therefore, further field-based research on artificial upwelling, especially for long-term field research is required to test the scientific hypothesis.