Influence of Particle Sinking Velocities on Carbon Flux Attenuation and
Export Efficiency
Abstract
Particle sinking velocity is an important determinant of carbon
transport and sequestration to the deep-sea. It is however technically
challenging to measure in situ particle sinking velocities. Recently,
methods based on the radioactive pairs, (234Th-238U and 210Po-210Pb)
were developed to estimate average sinking velocity (ASV), along the
classical carbon export flux estimates. The influence of ASVs on key
metrics of the biological carbon pump such as (i) the particle export
efficiency (defined as the proportion of PP being exported below the
surface ocean) (ii) carbon export fluxes and attenuation, still remain
uncertain and need to be further evaluated. ASVs are calculated in five
biogeochemically contrasting sites: high latitude (Irminger Basin;
Scotia Sea), temperate (PAP site) and oligotrophic (BATS, Equator) North
Atlantic. ASVs are also calculated for different bloom stages (bloom -
post bloom) in the North Atlantic and at the start of the bloom in two
contrasting sites in the Southern Ocean (Scotia Sea). A systematic
increase of ASVs with depth, inversely correlated to carbon flux
attenuation, is detected. We assess whether the increase in ASV with
depth is correlated with either temperature or community structure
(phytoplankton and/or zooplankton). Evidences of ASV correlation with
carbon export efficiency are detected, but they vary strongly with
season and location, e.g. very distinct relationships are found for the
results from Scotia Sea, likely driven by zooplankton abundance.