『Abstract
The IRONEX II in situ fertilization experiment showed decisively
that availability of iron limits the growth of phytoplankton in
equatorial Pacific surface waters. High-nutrient low-chlorophyll
(HNLC) surface waters, potentially iron limited, are also found
in the North Pacific and the Southern Ocean. A model of seawater
iron geochemistry has been incorporated into a global ocean circulation
and carbon cycle model and tuned to match the observed ocean Fe
distribution. The model reproduces the observed HNCL areas in
the equatorial Pacific and Southern Ocean but predicts nutrient
depletion in the North Pacific (a region of high dust fluxes from
Asia). The model is based on the idea that the concentrations
of organic iron-binding ligands in seawater control the subsurface
Fe concentration and predicts that a majority (70-80％) of the
global carbon export production can be sustained by upwelling
of dissolved iron in seawater rather than by atmospheric depositions.
The ocean iron cycle increases the efficiency of iron utilization
in the biological pump, buffers new production against interannual
fluctuations in iron deposition, and contributes several new intrinsic
timescales to the ocean carbon cycle: several hundred years for
the ocean iron concentration and perhaps several thousand for
the concentration of ligand in the deep sea. Ocean recycling of
Fe appears to play a major role in determining the strength of
the biological pump in the ocean and the p CO2
of the atmosphere.』
1. Introduction
2. Model description
3. Results
3.1. Fe distribution and cycling
3.2. Distribution of sea surface PO43-
3.3. Importance of iron complexation
3.4. Sensitivity to the distribution of iron deposition
3.5. Timescale of ocean responses to iron deposition
4. Summary
Acknowledgements
References