Scientists from the National Oceanography Centre (NOC) have evaluated a potential new way to remove CO2 from the atmosphere, by adding a common mineral called olivine to the ocean.
In a paper published in Earth’s Future journal, scientists found that adding olivine helped to absorb additional CO2 as it dissolved on the bottom of the ocean, ultimately increasing the uptake of CO2 by 8% over the 21st century. This increase equates to approximately two years’ worth of present-day global CO2 emissions.
NOC scientists, Dr. Julien Palmiéri and Dr. Andrew Yool, employed a state-of-the-art climate model to simulate the benefits of depositing olivine, a bright green mineral, on the seafloor to change the chemical make-up of the ocean—increasing its capacity to act as a carbon sink. This process is known as ocean alkalinity enhancement (OAE) and could be a future approach for increasing CO2 uptake by the ocean and reducing the impact of ocean acidification.
The team ran a future projection simulation which spanned 2020 to 2100 and involved depositing 81 billion metric tonnes of olivine into shallow areas of the ocean. Shallow waters are important since the chemical products of the dissolving olivine need to be near the ocean’s surface so that the extra CO2 is successfully absorbed from the atmosphere.
Dr. Andrew Yool, an Ocean Biogeochemistry Modeler and co-lead of the study, said: “What this research shows is that there is potential in utilizing the ocean to absorb CO2 and help support the drive to reach net zero. However, the research also makes clear that this is not a silver bullet and there are limitations on the scale it can be deployed at. Keeping global temperature rise below 2°C as specified by the Paris Agreement will still require a significant reduction in emissions.”
Significantly, while the olivine was added only to coastal and shallow ocean areas during the simulation, the paper found that around half of all the extra CO2 absorption occurred away from the areas where the olivine was being added. This finding means that significant field work would likely be needed in order to effectively monitor and verify its efficiency.
Speaking further on the study, Dr. Yool, added: “More research will need to be commissioned to understand some of the wider impacts of OAE, such as the carbon impact of mining the additional olivine that would be needed. Additionally, any practical deployment of olivine in the ocean will need to carefully monitor the impact on sea life.”
The paper, titled “Global-scale evaluation of coastal ocean alkalinity enhancement in a fully-coupled Earth system model”, used UKESM1, the UK’s Earth system model, for its future simulations. The ocean carbon cycle of UKESM1 makes use of MEDUSA, the marine biogeochemistry submodel developed and operated by the National Oceanography Centre. MEDUSA simulates the ocean side of the wider carbon cycle, including the atmosphere and land, and permits the full climate effects of the olivine scheme to be examined.
