Ocean Alkalinity Enhancement Experiments Explore Carbon Absorption

Efforts to address ocean acidification have led to new research on ocean alkalinity enhancement, a method that involves adding alkaline substances to seawater to raise pH and improve carbon dioxide absorption.

In August 2025, a team from Woods Hole Oceanographic Institution carried out an experiment in Wilkinson Basin, located about 50 miles from Massachusetts. The researchers dispersed sodium hydroxide into the sea, increasing the local pH from approximately 7.95 to 8.3 over an area as large as six miles across. To track the dispersion, they mixed about 16,200 gallons of sodium hydroxide with red dye before releasing it into the water.

Following the experiment, the elevated pH levels returned to their original state, and the dye used for tracking dissipated within five days. This approach is one of several being tested to determine the effectiveness and environmental impact of raising ocean alkalinity.

Other research initiatives have explored different methods and locations. In Sequim Bay, Washington, scientists used electrochemical techniques to release alkalinity-enhanced seawater in two separate trials. The first trial in November 2024 involved 7,000 gallons, while the second in February 2025 used 47,000 gallons. Monitoring indicated that there were no detectable environmental changes beyond about eight feet from the point of release.

What the numbers show

• About 16,200 gallons of sodium hydroxide were used in the Massachusetts experiment
• Surface seawater pH declined from 8.2 to 8.04 between the Industrial Revolution and 2024
• In Sequim Bay, 7,000 and 47,000 gallons of alkalinity-enhanced seawater were released in two trials
• A North Atlantic experiment saw a 10 percent decline in added alkalinity and sequestered CO₂ within 25 days

Planetary Technologies has adopted a different approach by using magnesium hydroxide, a compound found in common antacids, to increase ocean alkalinity. The company introduces this substance through wastewater treatment facilities and power plants, providing another pathway to enhance the ocean’s ability to absorb carbon dioxide.

Long-term studies are also underway to assess the persistence of alkalinity changes and their effects on carbon sequestration. A mesocosm experiment in the North Atlantic that doubled the ambient alkalinity found that both the added alkalinity and the amount of chemically stored carbon dioxide decreased by about 10 percent within 25 days, with further reduction observed over a 90-day period.

Research has also examined the potential ecological effects of these interventions. A study by GEOMAR reported that moderate increases in ocean alkalinity had minimal impact on zooplankton and overall food-web stability in a nutrient-poor subtropical environment.

Ocean alkalinity enhancement continues to be studied as a possible method to counteract the increase in ocean acidity, which has risen by roughly 40 percent since the Industrial Revolution. Ongoing experiments and monitoring are providing data on environmental safety and the durability of pH changes in various marine settings.

* This article is based on publicly available information at the time of writing.