The Ocean's Carbon Conveyor
Every year, microscopic phytoplankton in the sunlit ocean surface fix approximately 50 billion tonnes of carbon through photosynthesis — rivaling all terrestrial plants combined. When these organisms die or are consumed, a fraction of this carbon sinks into the deep ocean as a steady rain of organic particles. This biological carbon pump is one of Earth's most important carbon sequestration mechanisms, keeping atmospheric CO₂ roughly 200 ppm lower than it would be otherwise.
Sinking Into the Dark
Only 10-15% of surface production escapes the upper ocean as 'export production' — the rest is recycled by bacteria and grazers in the euphotic zone. The particles that do sink — dead phytoplankton, zooplankton fecal pellets, and mucous aggregates called marine snow — are progressively consumed by mesopelagic organisms. The Martin curve describes this attenuation: flux decreases as a power law with depth, F(z) ∝ z^(−0.86).
Deep Ocean Sequestration
Carbon remineralized below the permanent thermocline (~1000m) is effectively isolated from the atmosphere for centuries to millennia — the time required for deep ocean water to return to the surface through thermohaline overturning circulation. The depth at which organic matter is remineralized therefore determines the sequestration timescale. Large, fast-sinking particles like diatom aggregates and salp fecal pellets reach greater depths, making them disproportionately important for long-term carbon storage.
Climate Feedbacks
Climate change threatens to weaken the biological pump. Warming increases ocean stratification, reducing the upward nutrient supply that fuels phytoplankton growth. Shifts from large diatoms to small picoplankton reduce export efficiency. However, ice retreat and changing wind patterns may enhance productivity in some regions. Understanding these competing feedbacks is critical for predicting future ocean carbon uptake — and this simulation lets you explore how changes in productivity, export efficiency, and circulation affect carbon sequestration.