The biological carbon pump consists of a collection of coupled physical and biogeochemical processes, which together transport large quantities of carbon from the ocean surface to the interior.

The efficiency of this transport can vary geographically, and understanding this variation and its causes is paramount, since it impacts how much carbon dioxide is sequestered by the ocean. The variability in this transfer efficiency is still poorly constrained, and there is no current consensus for its cause, with previous global compilations being inconclusive on whether it is higher at higher latitudes than in the tropics or vice versa. Here, we use a global ocean-biogeochemical model to show that seasonal variability in a spatially uniform flux attenuation can lead to spatial variability emerging in annual mean transfer efficiency that matches observations of being higher at high latitudes than in low latitudes. We also show that this approach can explain the differences between different transfer efficiency compilations, as being due to the time and duration of sampling, as well as the methodology used to derive the results. Our results suggest caution in the mechanistic interpretation of annual-mean patterns in transfer efficiency and demonstrates the need for consistent sampling in time to generate accurate estimates of the biological carbon pump that can be used to constrain our understanding.

It also suggests that incorporating a mechanistic model for sinking and attenuation that reproduces observed seasonal cycles is necessary to understand how the biological carbon pump will impact the carbon cycle in response to climate change.

Francisco de Melo Viríssimo, Adrian P. Martin, Stephanie A. Henson, Jamie D. Wilson. Seasonal variability in particle flux attenuation in the global ocean generates spatial variability in annual transfer efficiency. EarthArXiv Preprint, (2023). 


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