Researchers at the Woods Hole Oceanographic Institution will test a strategy this summer to combat climate change by manually raising the alkalinity of ocean water in a small area of the Gulf of Maine.

The project, called LOC-NESS (Locking away Ocean Carbon in the Northeast Shelf and Slope) and started in 2023, is intended to test the effectiveness of a process known as “ocean alkalinity enhancement.”

In the largest field test to date, Woods Hole researchers plan to release 16,000 gallons of a liquid sodium hydroxide solution, commonly known as lye or caustic soda, into a 0.2-square-mile (128-acre) area of ocean southeast of Portland called Wilkinson Basin.

The high-alkaline solution will dilute quickly but is expected to slightly increase the pH in a tiny area of a global water system that has been gradually becoming more acidic over the last two centuries as a result of human activity.

Oceans account for the majority of carbon sequestration on Earth, absorbing about 30 percent of carbon dioxide released into the atmosphere, Adam Subhas, lead researcher on the project, said. When sea water and carbon dioxide mix, they create carbonic acid that needs to be balanced to prevent the oceans from gradually becoming more acidic.

“The natural response of the ocean earth system to this acidification is that alkaline minerals, like limestone and the shells of organisms, will re-dissolve in response to that acidity and add that alkalinity back into sea water, and this neutralizes that acidity,” Subhas said.

But with the excess CO2 from human industry, this natural process hasn’t kept up. As a result, the pH of surface ocean waters has fallen by 0.1 pH units in the last 200 years to a current level of 8.1, according to the National Oceanic and Atmospheric Administration.

The pH scale runs from 0 to 14. Anything greater than seven is basic, or alkaline, and anything less than seven is acidic. While today’s ocean water remains basic, the pH scale is logarithmic and the drop of 0.1 units translates to about a 30 percent increase in acidity.

More acidic sea water affects shell-forming species such as mussels, lobsters and oysters, which grow thinner shells under the corrosive conditions.

The increased acidity also hinders the oceans’ ability to absorb CO2, leaving the excess human-produced emissions in the atmosphere where they contribute to global warming.

Ocean alkaline enhancement, as the process being tested by the Wood Hole researchers is known, aims to be part of the answer to that problem.

“The idea is that it basically offsets that acidification, and then it makes more room for carbon storage in seawater,” Subhas said.

If oceans are returned to pre-industrial pH levels, it’s estimated that they could sequester more than a gigaton of carbon dioxide per year and hold it for 1,000 years. That’s about one-tenth of what is generally thought to be needed, Subhas said.

The sodium hydroxide solution released into the Gulf of Maine this summer will be dyed so that its dispersal can be tracked. The researchers plan to monitor a 22-mile-radius area for CO2 absorption effects on the marine ecosystem.

The U.S. Environmental Protection Agency said the test is “not expected to result in unacceptable impacts,” but the agency’s permit requires the boat dispensing the solution to steer clear of North Atlantic right whales and schools of fish, if seen.

The plan has been criticized by environmental and fishing groups, particularly in an earlier iteration that would have released 66,000 gallons of the solution into gulf waters.

Friends of the Earth US and the Hands Off Mother Earth Alliance continue to oppose the scaled-back project and “geoengineering” of the oceans on grounds that adding a large amount of a highly caustic solution into the marine environment will be more harmful to sea life than has been advertised.

Friends of the Earth has previously said that the production of sodium hydroxide produces “similar or even higher levels of greenhouse gasses than they remove upon being dumped into the ocean.”

Sodium hydroxide is produced by passing an electric current through brine that can be derived from sea water. The process creates hydrochloric acid as a byproduct, which might have human applications, Subhas said, but would need to be dealt with one way or another. And the electricity for the process would have to come from somewhere.

“Obviously you’d want to use non-fossil energy, renewable energy, to run this reaction and produce alkalinity in this way,” Subhas said. “These processes do need to be overall removing more CO2 than they’re producing.”

A life cycle analysis, as it’s known, lies outside of the bounds of the Woods Hole study, Subhas said, but will need to be considered if the treatment is going to be used on a larger scale.

Even if it works as planned, Subhas stressed that ocean alkalinity enhancement won’t magically reverse climate change and will have to be combined with other strategies.

“I think it’s important to recognize here that the number one thing that we can do in terms of mitigating the effects of climate change, and this includes the effects in the oceans,” Subhas said, “is to just stop emitting so much CO2.”