Artificial upwelling is a geoengineering climate solution with a long history. The concept: mimic natural ocean upwelling by pumping cold, nutrient-rich seawater up from ocean depths via pipes to the surface. There it can cause a growth surge in CO2-absorbing plankton, nourishing aquaculture and tackling climate change. Closer to shore, the technique could even protect coral reefs from marine heat waves. But as simple as this idea sounds in theory, it has faced complex technological challenges, high costs and failed experiments, though it continues to garner interest. Whether marine upwelling will ever break through as a solution for fisheries or the climate is unclear. Bleached coral reef off Lizard Island, Australia. Researchers there studied the use of “cool water injections” to protect coral reefs from heatwaves and bleaching in 2020 and found that doing so would incur huge energy costs, limiting feasibility. Image courtesy of The Ocean Agency/Ocean Image Bank. Upwelling isn’t a new idea. First proposed in the 1970s as a method to feed fish farms and grow seaweed, it has seen waves of testing come and go. Over past decades, trials have operated with mixed success. In 2008, one test near Hawai‘i pumped cold, nutrient-rich water from a depth of 300 meters (nearly 1,000 feet). But that trial lasted just 17 hours before the pump failed. By contrast, tests in a semi-closed embayment in Aoshan Bay, China, between 2018 and 2020, proved more successful in prompting macroalgae growth. Starting in the 1990s, artificial upwelling was proposed as a…This article was originally published on Mongabay