A model of the iron cycle in the ocean

• Published in: Global biogeochemical cycles Vol. 14; no. 1; pp. 269 - 279
• Main Authors: Archer, D. E., Johnson, K.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01-03-2000; American Geophysical Union
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Geochemistry; Mineralogy; Physical and chemical properties of sea water; Physics of the oceans; Silicates; Water geochemistry; Equatorial Pacific; North Pacific; IS, Equatorial Pacific; PS, Antarctic Ocean; INW, Asia; IN, North Pacific; depletion; air-sea interface; spatial distribution; hydrochemistry; upwelling; partial pressure; phytoplankton; plankton; dissolved materials; dust; sea water; carbon dioxide; models; wind transport; geochemical cycle; fertilization; chlorophyll; recycling; carbon cycle; speciation; surface water; Asia; phosphates; Antarctic Ocean; iron; Pacific Ocean; ocean circulation
• ISSN: 0886-6236; 1944-9224
• DOI: 10.1029/1999GB900053

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 HNLC 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 deposition. 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 pCO2 of the atmosphere.