Ocean Carbon Cycle

The ocean’s biological pump is a natural process by which photosynthesizing marine organisms sink to the ocean floor, thereby moving carbon from the surface layers (fast carbon) to the deep ocean (slow carbon).

Depth and location are critical factors for how effective the biological carbon pump is at moving carbon from fast to slow. Significant anthropogenic CO₂ emissions have resulted in devastating levels of ocean acidification and myriad distressed ecosystems. Ocean acidification and warming also threaten to disrupt the biological carbon pump itself.

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Running Tide aims to preserve and sustainably amplify the rate of the biological carbon pump, while simultaneously reducing the pH of the surface ocean and restoring natural ecosystems. Since only a small fraction of phytoplankton actually sinks to the deep ocean, removing carbon, one way we can improve the efficiency of the biological carbon pump is by using a material that has a better ratio of fast carbon sinking to surface remineralization, like macroalgae or terrestrial biomass residues. Utilizing a combination of ocean modeling and in-situ data collection, we also aim to ensure that our carbon-rich material sinks in parts of the ocean that are sufficiently deep for durable removal.

The ocean is dynamic and is in constant motion. These motions range in time scales from seconds to millennia, and in spatial scales from millimeters to the globe. Our current research identifies several ocean dynamics that we’ve identified as the most pertinent to Running Tide’s carbon removal pathways. These include:

How does our introduced biomass compete with local phytoplankton populations for nutrients? How variable are baseline estimates of global NPP, and how much additional carbon are we sequestering on top of the biological carbon pump? What are the nutrient concentrations at the ocean surface, and how do they evolve over time?
How do ocean surface conditions affect Running Tide’s deployed system? Since the ocean surface has a multitude of affects, this question is multifold:

Where do surface currents and waves transport carbon substrates?
What is the efficiency of novel carbon drawdown into the ocean surface? How is this efficiency dependent on the time and location of deployment? What is the long term role that mixed-layer deepening and restratification plays in transporting carbon-poor water from the surface ocean to the deep ocean?

Where are the best deployment locations for slow carbon durability based on the ocean’s general overturning circulation?

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