The first of its kind involving ship-based dispersal in open ocean waters. Scientists released approximately 65,000 liters (about 17,000 gallons) of sodium hydroxide (NaOH, a strong alkaline substance, often called caustic soda or lye) into the Gulf of Maine over an area of roughly 1 km².

They also added a smaller amount (760 liters) of fluorescent rhodamine dye to track the dispersion of the alkaline plume across a larger monitoring zone of about 3,600 km².

This is an example of ocean alkalinity enhancement (OAE), a proposed marine carbon dioxide removal (mCDR) geoengineering technique.

The ocean naturally absorbs CO₂ from the atmosphere, forming carbonic acid that contributes to ocean acidification (lowering pH).

Over geological timescales, weathering of rocks adds alkalinity, helping the ocean draw down and store more CO₂ as stable bicarbonate ions (essentially dissolved baking soda).

OAE accelerates this by deliberately adding alkaline materials to increase ocean pH in targeted areas, forcing additional CO₂ uptake from the air without relying on slow natural processes.

The goal is scalable carbon removal to help mitigate climate change, alongside emissions reductions, not a complete “fix” or replacement for cutting greenhouse gases.

Results presented at the Ocean Sciences Meeting in February 2026:

• The addition led to measurable extra CO₂ drawdown from the atmosphere: between 2–10 tonnes confirmed in the first few days after release, with estimates up to around 50 tonnes total over time.
• Monitoring showed no evidence of harm to marine life or ecosystems in the affected area, based on biological and chemical assessments.
• The “bright red” appearance mentioned in some reports likely comes from the rhodamine dye used for tracking (not the sodium hydroxide itself, which is typically clear or white in solution).

Context and ControversyWhile the trial was small-scale and controlled (equivalent to a tiny fraction of natural ocean processes), it has drawn attention and criticism:

• Supporters see it as promising proof-of-concept data for a potential large-scale CDR tool.
• Critics (including some in skeptical or alternative media) highlight risks of unintended ecological impacts from scaling up, questions about energy costs of producing sodium hydroxide, or broader concerns about “playing God” with geoengineering.

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This experiment tested ocean alkalinity enhancement (OAE), a geoengineering approach to marine carbon dioxide removal (mCDR).

Oceans naturally absorb CO₂, but human emissions have acidified them (dropping average pH from ~8.2 pre-industrial to ~8.1 today).

OAE mimics natural rock weathering by adding alkaline substances to raise pH locally, enabling the ocean to pull in more CO₂ from the atmosphere and store it as stable bicarbonate.

Chemistry World

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Controversial geoengineering project sees scientists pump 65,000 litres of chemicals into the ocean to stop global warming

Last August, 65,000 litres of bright red chemicals were pumped into the Gulf of Maine – yet this wasn’t an enormous industrial disaster. The Daily Mail Online has the story.

Instead, it was a controversial geoengineering experiment that scientists claim could help to slow down global warming.

The oceans already hold around 38,000 billion tonnes of CO2, trapped as dissolved sodium bicarbonate, or baking soda.

The geoengineering method known as Ocean Alkalinity Enhancement (OAE) aims to speed up this natural process by resetting the ocean’s pH.

Over four days, scientists added vast quantities of sodium hydroxide – an alkaline chemical tagged with a red dye – to the waters off the coast of Boston. 

Making the ocean more alkaline should encourage it to absorb even more CO2 from the atmosphere.

However, critics have warned that the potential effects on marine life remain uncertain.

Gareth Cunningham, Director of Conservation and Policy at the Marine Conservation Society, told the Daily Mail: ‘These approaches are resource–intensive and their ecological impacts are still poorly understood.’

For years, scientists have put forward OAE as one of the leading potential solutions to climate change.

In theory, the novel approach could solve two problems at once by locking away excess CO2 from the atmosphere and fixing the oceans’ rising acidity.

Without an ‘antacid’ like sodium hydroxide to react with, CO2 dissolving in the oceans forms a mild acid that has slowly but surely reduced the pH level.

This is already having catastrophic effects on sea life, as the acid dissolves marine creatures’ shells, damages coral, and even wears away sharks’ teeth.

The LOC–NESS (Locking Ocean Carbon in the Northeast Shelf and Slope) project is the first large–scale experiment to test the impact of OAE in an open water setting.

With approval from the US Environmental Protection Agency and engagement with local fishers, scientists from the Woods Hole Oceanographic Institution poured alkaline chemicals into the ocean 50 miles (80 km) off the Massachusetts coast.

They then used cutting–edge technology, including autonomous gliders, long–range autonomous underwater vehicles and shipboard sensors to track the spreading chemicals.

Over the next few days, the scientists measured 10 tonnes of carbon entering the water as the pH increased from 7.95 to 8.3 – matching pre–industrial levels.

In the best–case scenario, the researchers estimate that the sodium hydroxide would absorb about 50 tonnes of carbon over the next year, equivalent to the average yearly emissions of five UK citizens.

Principal investigator Adam Subhas, of the Woods Hole Oceanographic Institute, says: ‘These early results demonstrate that small–scale OAE deployments can be engineered, tracked, and monitored with high precision.

Read the full story here.