Beschreibung:
<jats:p>Abstract. The biological pump of the ocean has changed over Earth's history, from one dominated by prokaryotes to one involving a mixture of prokaryotes
and eukaryotes with trophic structure. Changes in the biological pump
are in turn hypothesized to have caused important changes in the
nutrient and redox properties of the ocean. To explore these hypotheses, we
present here a new box model including oxygen (O), phosphorus (P) and
a dynamical biological pump. Our Biological Pump, Oxygen and
Phosphorus (BPOP) model accounts for two – small and large – organic
matter species generated by production and coagulation,
respectively. Export and burial of these particles are regulated by
a remineralization length (zrem) scheme. We independently
vary zrem of small and large particles in order to study
how changes in sinking speeds and remineralization rates affect the
major biogeochemical fluxes and O and P ocean concentrations.
Modeled O and P budgets and fluxes lie reasonably close to present
estimates for zrem in the range of currently measured
values. Our results highlight that relatively small changes in
zrem of the large particles can have important impacts on
the O and P ocean availability and support the idea that an early
ocean dominated by small particles was nutrient rich due to the
inefficient removal of P to sediments. The results also suggest that
extremely low oxygen concentrations in the shelf can coexist with an
oxygenated deep open ocean for realistic values of zrem,
especially for large values of the small-particle
zrem. This could challenge conventional interpretations
that the Proterozoic deep ocean was anoxic, which are derived from
shelf and slope sediment redox data. This simple and computationally
inexpensive model is a promising tool to investigate the impact of
changes in the organic matter sinking and remineralization rates as
well as changes in physical processes coupled with the biological pump
in a variety of case studies.
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