Abstract
AbstractThe sinking of carbon fixed via net primary production (NPP) into the ocean interior is an important part of marine biogeochemical cycles. NPP measurements follow a log‐normal probability distribution, meaning NPP variations can be simply described by two parameters despite NPP's complexity. By analyzing a global database of open ocean particle fluxes, we show that this log‐normal probability distribution propagates into the variations of near‐seafloor fluxes of particulate organic carbon (POC), calcium carbonate, and opal. Deep‐sea particle fluxes at subtropical and temperate time‐series sites follow the same log‐normal probability distribution, strongly suggesting the log‐normal description is robust and applies on multiple scales. This log‐normality implies that 29% of the highest measurements are responsible for 71% of the total near‐seafloor POC flux. We discuss possible causes for the dampening of variability from NPP to deep‐sea POC flux, and present an updated relationship predicting POC flux from mineral flux and depth.
Highlights
Ocean biogeochemical cycles have much to do with vertical transport of carbon and other elements via particle sinking and other processes (Boyd et al, 2019)
Net primary production (NPP) by phytoplankton largely controls how much carbon is available to the rest of the ecosystem (Osmond, 1989); most of this sustains the heterotrophic communities living in the euphotic zone, but a fraction is transported to deeper depths
The difference in measurement scales should reduce deep-sea relative to shallow, and shallow relative to σ for NPP (σNPP); regardless of this measurement-produced offset, the coherence in the differences between σ values in Figure 4 does imply a consistent relationship between the variability in NPP and the variability in deep-sea particulate organic carbon (POC) flux across scales and locations
Summary
The log-normal probability distribution is a robust description of variability in net primary production and particulate organic carbon (POC) flux in both the upper open ocean and the deep sea. We present an updated flux relationship for organic carbon, calcium carbonate, and opal. ∼70% of the POC deposition to the deep seafloor occurs during highflux periods which cover only ∼30% of the time. Cael , Kelsey Bisson , Maureen Conte, Manon T. Mouw , Frank Muller-Karger , Corinne A. Supporting Information: Supporting Information may be found in the online version of this article
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