Geoengineering The Gulf Of Maine

Woods Hole begins field tests of ocean alkalinity enhancement off Cape Cod

Scientists at the Woods Hole Oceanographic Institution have launched LOC-NESS — “Locking Ocean Carbon in the Northeast Shelf and Slope” — to test ocean alkalinity enhancement (OAE) as a tool to reduce ocean acidification and draw down atmospheric carbon dioxide. During a four-day field test last August near Cape Cod the team released 65,000 liters (17,000 gallons) of sodium hydroxide over a 1 km2 area and 760 liters (200 gallons) of fluorescent rhodamine dye, monitored by three vessels, four autonomous underwater vehicles and a suite of sensors, with NASA’s PACE satellite providing an aerial view. The group reported that 2 to 10 tonnes of atmospheric CO2 were absorbed during the four-day monitoring period, with modeling suggesting this could rise to about 50 tonnes over a year.

"These early results demonstrate that small scale OAE deployments can be engineered, tracked, and monitored with high precision," said Adam Subhas, a Woods Hole marine chemist and LOC-NESS principal investigator.

Study details and reactions

• Concept: add alkaline materials to seawater to increase alkalinity so the ocean draws down more CO2; dissolved bicarbonate is the primary oceanic carbon sink.
• Field work: 65,000 liters of sodium hydroxide released over 1 km²; 760 liters of rhodamine dye used for dispersion tracking; three vessels and four AUVs deployed.
• Early results: 2–10 tonnes CO2 removed in four days; modeled to ~50 tonnes over a year; NOAA cost estimate for OAE cited at roughly $160 per tonne CO2 removed.
• Monitoring: the team tracked pH, partial pressure of CO2 and biological indicators including phytoplankton, zooplankton, fish and lobster larvae.

The LOC-NESS team says the field tests found no measurable reductions in phytoplankton or zooplankton and "no impacts on organisms higher up the marine food chain." Rachel Davitt of Rutgers University stressed the importance of those checks: "It was really important for us to measure the fish and lobster larvae, after concerns of local fishermen," she said.

Researchers acknowledge monitoring and verification remain major hurdles. In presenting provisional findings, the group noted that "The community of OAE practitioners has little experience deploying and tracking alkalinity plumes in the ocean, and we lack proven methodologies for quantifying the carbon stored by OAE," and said such methodologies will be "crucial for the monitoring, reporting, and verification of OAE technologies."

Pushback and the path ahead

The program has drawn criticism from environmental groups. Friends Of The Earth warned about the risks of putting caustic chemicals in coastal waters: "Sodium hydroxide is a dangerous, caustic chemical that causes chemical burns on contact with skin," the group said, noting waters affected are frequented by endangered species including North Atlantic right whales and leatherback turtles. Eesha Rangani, Marine Working Group Coordinator at HOME, added, "Elevated pH levels caused by sodium hydroxide can severely impact the hatching and development of eggs of endangered species like Atlantic sturgeon and Atlantic salmon in this region."

Opponents also reacted to proposed scale-up plans. LOC-NESS's next phase would increase chemical additions by a factor of ten, prompting Benjamin Day, senior campaigner for the Climate and Energy Justice team at Friends Of The Earth, to urge opposition: "We should not be dumping dangerous chemicals into thriving marine ecosystems."

Researchers and funders — with interest from companies such as Microsoft and Google to purchase credits if the approach scales — face scientific and governance questions: how much durable carbon is offset, the energy and costs of producing and distributing alkalinity, and how to robustly monitor ecological impacts. As LOC-NESS moves toward larger tests, the team says rigorous instrumentation and transparency will be essential to determine whether OAE can be a verifiable climate tool without unacceptable ecological harm.