516 / 2024-09-18 10:02:26

A global biological carbon pump estimate constrained from hydrographic tracer observations

Biological carbon pump,Nutrients,Inverse Model

We analyzed multiple decades of hydrographic observations to estimate the strength of the biological carbon pump. These observations included dissolved organic and inorganic carbon, dissolved oxygen, phosphate, and alkalinity. Our analysis, which is based on an inverse model, produces a top-down estimate that implicitly accounts for all export pathways.  Our analysis reveals that the organic carbon export at a depth of 73.4 m is 15.00 Pg C / yr with only two-thirds of this reaching a depth of 100 m because of rapid remineralization in the upper water column. Analternative perspective of this depth sensitivity is provided by distribution functions for the sequestration time, τ, of organic carbon production and for the stock of regenerated carbon.  We estimate that the total organic carbon production with τ > 3 months is 11.09 ± 1.02 Pg C yr−1. For τ > 1 year, the total export flux decreases to 8.25 ± 0.30 Pg C yr−1 and for τ > 3 years, it is only 6.30 ± 0.09 Pg C yr−1. The distribution reveals the dominance of small residence-time export in the total flux. Yet, this small residence-time flux contributes negligibly to the standing stock of regenerated dissolved inorganic carbon, underscoring the rapid recycling of a significant portion of the organic matter production.