An important paradigm that guided the biological oceanographic community
over the last three decades is that new production can be equated with
export production when averaged over appropriate spatial and temporal scales.
This allows to use estimates of new production as a substitute for the
often more difficult measurements of export production. The fundamental
assumption is that horizontal transport of organic matter is negligible
compared to vertical export. We investigate the relationship between new
and export production for the central Californian upwelling system using
an eddy-resolving coupled physical-ecosystem-biogeochemical ocean model.
We find that lateral transport leads to substantial spatial decoupling
of export from new production even when averaged over the annual cycle,
with a length-scale of decoupling on the order of 300 km. The decoupling
is largely caused by mean horizontal fluxes induced by persistent meso-
and submesoscale circulation structures and to lesser degree by the mean
lateral offshore transport induced by Ekman transport. This indicates that
the concept of numerically equal new and export production has to be used
with great care, particularly in dynamic oceanic environments.
Presented at ASLO Summer Meeting 2005, Santiago de
Compostela/Spain, June 20, 2005 (Session: SS08 - Carbon and Carbonate Fluxes
in the Coastal Ocean)