The impact of patch size and duration on the efficiency of
iron fertilization: results from an eddy-permitting model
Xin Jin, Nicolas Gruber, and Hartmut Frenzel
Fertilization efficiency, i.e., the amount of atmospheric CO2
draw-down per unit of iron added, is an important criterion to assess
ocean iron fertilization, which has been considered as a means to
enhance the net oceanic uptake of CO$_2$ from the atmosphere to slow
down the buildup of atmospheric CO$_2$. Field experiments in which
high iron concentrations are maintained in a relatively small patch of
surface water have resulted in increases in biomass and draw-down of
surface nutrients and CO$_2$. Yet little is known about the increase
in export and the net effect of the air-sea CO$_2$ flux. The sizes of these in-situ experiments
were small, typically 10 by 10 km, and they usually lasted only a few
weeks. Most models of fertilization experiments have been
done at coarse
resolution, creating a gap
between in-situ and global-scale model studies. To bridge this gap, we
use a Pacific Ocean setup of ROMS (the
Regional Oceanic Modeling System) at an
eddy-permitting resolution of 0.5 degrees. By
coupling an ecosystem model to this circulation model and performing
experiments in scale ranging from the same patch size of the in-situ
experiments to the several 100 km size of the coarse resolution model,
we can establish a connection
between these model studies and the many insights emerging from the
very small-scale patch fertilization studies. The biogeochemical model
features three phytoplankton functional groups and multiple nutrient
limitation (N, P, Si, Fe). We will calculate iron fertilization efficiency based on a
series of iron fertilization experiments, including different iron
flux levels, different locations, different durations, and different patch sizes.
For citations, please use:
Jin, X. N. Gruber, and H. Frenzel (2006), The impact of patch size and
duration on the efficiency of
iron fertilization: results from an eddy-permitting model, Eos
Trans. AGU, 87(36), Ocean Sci. Meet. Suppl., Abstract OS34F-02