In August last year, scientists pumped 65,000 litres of sodium hydroxide mixed with red dye into the Gulf of Maine, creating a maroon slick that resembled a toxic red tide. The experiment, part of the Loc-Ness project led by the Woods Hole Oceanographic Institution, aimed to test ocean alkalinity enhancement (OAE) as a method to combat global heating and ocean acidification.
OAE mimics natural weathering processes but on human timescales. By increasing the ocean's alkalinity, the technique encourages greater absorption of atmospheric carbon dioxide. The ocean already holds 38,000 billion tonnes of carbon as dissolved bicarbonate, and boosting this natural alkalinity could help prevent global temperatures exceeding 2°C above preindustrial levels, while reducing local acidity that threatens marine life.
The experiment, licensed by the US Environmental Protection Agency, took place 50 miles off Massachusetts in a fishing area. Over five days, autonomous gliders, underwater vehicles, and shipboard sensors tracked the dispersal of the chemical. Early results, presented at the AGU Ocean Sciences Meeting in Glasgow, showed up to 10 tonnes of carbon entering the ocean and local pH rising from 7.95 to 8.3—returning to preindustrial levels. No significant harm was observed to plankton, fish, or lobster larvae, though adult fish and marine mammals were not studied.
Critics, including Benjamin Day of Friends of the Earth US, express concern about unforeseen environmental impacts at scale. However, Phil Renforth of Heriot-Watt University notes that humanity is already experimenting with the climate by adding CO2 to the atmosphere, and proactive management of ocean carbon uptake may be necessary. OAE has historical parallels in liming, used by Greek farmers 2,000 years ago and in Scandinavian rivers to counteract acid rain in the 1980s.
The team now plans to model how the chemical plume continues to absorb CO2 over time, with a best-case estimate of about 50 tonnes of carbon dioxide uptake over a year. The study has yet to undergo peer review.
