Theory 04/Oceanography & Deep Sea/Biological pump
Sequestration Is a Sinking Ratio
Carbon export is measured at the surface. What matters is whether the particles outrun the bacteria eating them.
The carbon sequestered by the biological pump is set by the ratio of particle sinking speed to remineralisation rate rather than by export flux, so doubling export with slow particles sequesters nothing extra.
01The evidence
Carbon flux declines steeply with depth, and the attenuation varies widely between regions at similar surface export.
02The tension
Models scale sequestration with export production, treating attenuation as a fixed exponent. That predicts more export means more storage, which the regional variation contradicts.
03The mechanism
A sinking particle is consumed as it falls. The fraction that reaches depth depends on how long it takes to fall a given distance relative to how fast it is respired, which is a ratio of two rates.
That makes sinking speed a first-order control. Faster particles of the same composition sequester more; slow particles are consumed in the upper layer regardless of how many are produced.
04What this is not
That model scales with production. This scales with the ratio, which explains why high-export regions can store little.
05Predictions
- P1Sequestration should track the sinking-to-remineralisation ratio.
- P2High export with slow particles should store no more than low export with fast ones.
- P3Ballasting should raise sequestration without raising export.
06Refutation
Sequestration tracking export at controlled sinking speed would restore the production model.
07What it changes
It would change how ocean carbon storage is projected and engineered.