In situ Particle Measurements Deemphasize the Role of Size in Governing
Particle Sinking Velocity
Sinking particles are important in delivering carbon to the deep ocean
where it may be stored out of contact with the atmosphere. Particle
sinking velocity strongly influences the amount of carbon reaching the
deep ocean, and is thought to be strongly affected by particle size.
Here we carried out an extensive literature review (62 datasets) into
the size-sinking velocity relationship, and find the relationship is
much weaker for studies examining particles in situ (median
R2 = 0.03) compared with ex situ studies (median
R2 = 0.35). This may be because particles examined in
the laboratory have more uniform properties than those studied in situ,
and represent only a subset of particles from the natural environment.
Our findings suggest a simple relationship between size and sinking
velocity may be insufficient when calculating sinking particulate fluxes
in the ocean; considering different particle types individually will
enable more accurate calculations of particulate fluxes.