The Caltech Alum Trying to Combat Ocean Acidification
Adam Subhas. Photo: Woods Hole
by Andrew Moseman
To fight ocean acidification, Adam Subhas (PhD ’17) is dumping lye into the sea. The New York Times recently profiled the alumnus who, along with his team at Woods Hole Oceanographic Institution, has been experimenting with a geoengineering solution for climate change by attempting to alter the pH of the ocean.
The ocean grows more acidic as it absorbs excess carbon dioxide from the atmosphere. As a result of carbon emissions from humanity’s burning of fossil fuels, surface seawater’s pH has lowered from 8.2 in preindustrial times to 8.02 in 2024, the Times reports, a 40 percent increase in acidity. Its report goes on to note:
As a graduate student in geochemistry at the California Institute of Technology in Pasadena, Subhas became fascinated by Earth’s long-term carbon cycle, which regulates climate and balances the pH of the ocean. Carbon continually cycles between air, sea and land. Throughout Earth’s history, huge injections of carbon into the atmosphere—from, say, increased volcanic activity—have resulted in a sweltering climate, a more acidic ocean and, in some cases, mass extinction of marine life.
As seawater becomes more acidic, it interferes with the physiology of ocean creatures in numerous ways, disrupting processes as diverse as metabolism, sensory perception, reproduction and communication. Extreme acidification is especially disastrous for a group of organisms known as calcifiers, which include corals, mollusks, crustaceans and many types of plankton. Calcifiers construct their shells and skeletons from alkaline minerals present in seawater, in particular calcium and carbonate. As pH drops, carbonate becomes less available and calcifiers struggle to build and maintain their armor. If the ocean becomes too acidic, they begin to dissolve.
Subhas and his colleagues’ most recent experiment involved releasing 16,200 gallons of sodium hydroxide into a part of the Atlantic Ocean about 50 miles off the Massachusetts coast. This extremely alkaline chemical, also known as caustic soda or lye, was dyed red so it could be seen as it spread over an area 6 miles across. Within the test patch, the researchers found areas in which the sodium hydroxide has lifted surface pH from 7.95 to 8.3, making it much more alkaline. The Woods Hole experiment was meant to demonstrate that the treatment could affect pH without causing significant harm to marine wildlife within the test area, and researchers told the Times that their data show it is indeed safe. Subhas hopes a large-scale deployment of sodium hydroxide could push back against ocean acidification and allow more carbon from the atmosphere to be sequestered at sea.
Audacious as it may sound, tinkering with the sea’s chemistry has become a popular topic for finding new ways to mitigate climate change. In 2023, Caltech magazine wrote about pathbreaking work being done by Caltech-affiliated startups Calcarea and Captura, both of which are working on carbon capture in the ocean, either by removing CO2 directly from the waters or by cleaning the flue gas emanating from cargo ships.