Artificial upwelling is a proposed marine geoengineering technique that involves bringing cooler, nutrient-rich water from the deep ocean to the surface. This process aims to stimulate the growth of microscopic marine organisms, primarily phytoplankton, which form the base of the ocean’s food web. The goal is to enhance natural biological processes, potentially influencing atmospheric carbon dioxide levels.
The Ocean’s Natural Upwelling Process
Natural upwelling is an oceanographic phenomenon where dense, cooler, nutrient-rich water from deeper parts of the ocean moves towards the surface. This upward movement replaces warmer, nutrient-depleted surface water. It occurs in specific regions of the ocean, driven by surface winds, the Coriolis effect (due to Earth’s rotation), and ocean currents.
Coastal upwelling, the most recognized type, happens when winds blow parallel to the coastline, pushing surface water away from the shore. This creates a void that is then filled by colder, denser water rising from below. Equatorial upwelling occurs near the equator as trade winds and ocean currents diverge, causing deep water to ascend. The influx of nutrients like nitrates, phosphates, and silicates “fertilizes” the sunlit surface waters, leading to a surge in phytoplankton growth. These highly productive upwelling zones, though occupying only about 5% of the total ocean area, account for approximately 25% of the global marine fish catch.
Methods of Artificial Upwelling
Various techniques have been proposed and tested to induce artificial upwelling. One common approach involves pump systems that physically transport deep ocean water to the surface through pipes. These systems can be powered by electricity, though electrical pumps have been deemed too expensive for large-scale deployment.
More recent and often self-sustaining methods include air-lift pumps, which use compressed air to create bubbles that lift deep water upwards, or systems powered by wind or waves. These methods involve long plastic pipes, potentially hundreds of meters deep, connected to floating or submersible platforms. While some early trials faced technical challenges like pump failure, more recent tests in semi-enclosed bays have shown success in promoting macroalgae growth.
Applications and Potential Benefits
Artificial upwelling is explored for several applications, focused on enhancing marine productivity and addressing climate challenges. A primary goal is to stimulate the growth of phytoplankton, which absorb atmospheric carbon dioxide (CO2) during photosynthesis. When these microscopic organisms die and sink, the carbon they contain can be sequestered in the deep ocean, potentially for decades to centuries.
The increased marine productivity from artificial upwelling could also support fisheries and aquaculture. By bringing nutrient-rich deep water to the surface, it can create more abundant food sources for marine life, potentially alleviating pressure on wild fish stocks and enhancing the yield of farmed seafood. Artificial upwelling has also been investigated for its potential to aid in the restoration of marine ecosystems, such as coral reefs. Introducing cooler, deep water can help mitigate the thermal stress that leads to coral bleaching, offering a localized protective measure against rising ocean temperatures.
Environmental Considerations
The broader environmental implications of artificial upwelling are a subject of ongoing research and discussion, encompassing both potential co-benefits and important concerns. One potential co-benefit is localized cooling of surface waters, which could help protect sensitive ecosystems like coral reefs from heat stress. Increased primary production could also lead to enhanced biodiversity in targeted areas, supporting a more robust food web.
Important concerns exist regarding the large-scale implementation of artificial upwelling. Altering local ocean chemistry by bringing up water with different nutrient and carbon profiles could have unintended impacts on existing marine food webs and ecosystems. There is a risk of deoxygenation in surface waters if the upwelled deep water has low oxygen content and the stimulated biological processes consume too much oxygen. The introduction of dissolved inorganic carbon from deep water could, under certain conditions, lead to a net outgassing of CO2 rather than sequestration, counteracting the intended climate benefit. The physical presence of large structures like pipes and platforms could also interfere with marine life, shipping, and fisheries, and contribute to marine debris if damaged.