Observational and numerical modeling constraints on the global ocean
biological carbon pump
Abstract
This study characterized ocean biological carbon pump metrics in the
second iteration of the REgional Carbon Cycle Assessment and Processes
(RECCAP2) project, a coordinated, international effort to constrain
contemporary ocean carbon air-sea fluxes and interior carbon storage
trends using a combination of observation-based estimates, inverse
models, and global ocean biogeochemical models. The analysis here
focused on comparisons of global and biome-scale regional patterns in
particulate organic carbon production and sinking flux from the RECCAP2
model ensemble against observational products derived from satellite
remote sensing, sediment traps, and geochemical methods. There was
generally encouraging model-data agreement in large-scale spatial
patterns, though with substantial spread across the model ensemble and
observational products. The global-integrated, model ensemble-mean
export production, taken as the sinking particulate organic carbon flux
at 100 m (6.41 ± 1.52 Pg C yr–1), and export ratio defined as sinking
flux divided by net primary production (0.154 ± 0.026) both fell at the
lower end of observational estimates. Comparison with observational
constraints also suggested that the model ensemble may have
underestimated regional biological CO2 drawdown and air-sea CO2 flux in
high productivity regions. Reasonable model-data agreement was found for
global-integrated, ensemble-mean sinking particulate organic carbon flux
into the deep ocean at 1000 m (0.95 ± 0.64 Pg C yr–1) and the transfer
efficiency defined as flux at 1000m divided by flux at 100m (0.121 ±
0.035), with both variables exhibiting considerable regional
variability. Future modeling studies are needed to improve system-level
simulation of interaction between model ocean physics and biogeochemical
response.