Because of its volume and carbon storage potential, the ocean is really the only arrow in our quiver that has the ability to take up and store carbon at the scale and urgency required.

A 2022 report by the national academies outlined a research strategy for ocean carbon dioxide removal. The three most promising methods all explore ways to enhance the ocean’s natural ability to take up more carbon.

The first is ocean alkalinity enhancement. The oceans are salty – they’re naturally alkaline, with a pH of about 8.1. Increasing alkalinity by dissolving certain powdered rocks and minerals makes the ocean a chemical sponge for atmospheric CO2.

A second method adds micronutrients to the surface ocean, particularly soluble iron. Very small amounts of soluble iron can stimulate greater productivity, or algae growth, which drives a more vigorous biologic pump. Over a dozen of these experiments have been done, so we know it works.

Third is perhaps the easiest to understand – grow kelp in the ocean, which captures carbon at the surface through photosynthesis, then bale it and sink it to the deep ocean.

But all of these methods have drawbacks for large-scale use, including cost and unanticipated consequences.

I’m not advocating for any one of these, or for ocean CDR more generally. But I do believe accelerating research to understand the impacts of these methods is essential. The ocean is essential for everything humans depend on – food, water, shelter, crops, climate stability. It’s the lungs of the planet. So we need to know if these ocean-based technologies to reduce carbon dioxide and climate risk are viable, safe and scalable.

The ocean is changing rapidly, and it is the single biggest cog in Earth’s climate engine, yet we have almost no observations of the subsurface ocean to understand how these changes are affecting the things we care about. We’re basically flying blind at a time when we most need observations. Moreover, if we were to try any of these carbon removal technologies at any scale right now, we wouldn’t be able to measure or verify their effectiveness or assess impacts on ocean health and ecosystems.

So, we are leading an initiative at Woods Hole Oceanographic Institution to build the world’s first internet for the ocean, called the Ocean Vital Signs Network. It’s a large network of moorings and sensors that provides 4D eyes on the oceans – the fourth dimension being time – that are always on, always connected to monitor these carbon cycling processes and ocean health.

Right now, there is about one ocean sensor in the global Argo program for every patch of ocean the size of Texas. These go up and down like pogo sticks, mostly measuring temperature and salinity.

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