Abstract
The availability of dissolved iron (dFe) exerts an important control on
primary production. Recent ocean observation programs have provided
information on dFe in many parts of the ocean, but knowledge is still
limited concerning the rates of processes that control the
concentrations and cycling of dFe in the ocean and hence the role of dFe
as a determinant of global primary production. We constructed a
three-dimensional gridded dataset of oceanic dFe concentrations by using
both observations and a simple model of the iron cycle, and estimated
the difference of processes among the ocean basins in controlling the
dFe distributions. A Green’s function approach was used to integrate the
observations and the model. The reproduced three-dimensional dFe
distribution indicated that iron influx from aeolian dust and from shelf
sediment were 7.6 Gmol yr and 4.4 Gmol yr in the Atlantic Ocean and 0.4
Gmol yr and 4.1 Gmol yr in the Pacific Ocean. The residence times were
estimated to be 12.2 years in the Atlantic and 80.4 years in the
Pacific. These estimates imply large differences in the cycling of dFe
between the two ocean basins that would need to be taken into
consideration when projecting future iron biogeochemical cycling under
different climate change scenarios. Although there is some uncertainty
in our estimates, global estimates of iron cycle characteristics based
on this approach can be expected to enhance our understanding of the
material cycle and hence of the current and future rates of marine
primary production.