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Biogeochemical impact of tropical instability waves in the equatorial Pacific

Abstract : Tropical Instability Waves (TIW) have been suggested to fertilize the equatorial Pacific in iron leading to enhanced ecosystem activity. Using a coupled dynamical-biogeochemical model, we show that contrary to this suggestion, TIWs induce a decrease of iron concentration by 20% at the equator and by about 3% over the "TIW box" [90°W- 180, 5°N-5°S]. Chlorophyll decreases by 10% at the equator and 1% over the "TIW box". This leads to a decrease of new production up to 10% at the equator (4% over the "TIW box"). TIW-induced horizontal advection brings more iron-depleted water to the equator than it exports iron-rich equatorial water to the north. Additional iron decrease is caused by TIW-induced iron vertical diffusion. These two mechanisms are partly counter balanced by a decrease of iron biological uptake, driven by weaker phytoplankton concentration, and to a lesser extend by TIW- induced iron vertical advection.
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Submitted on : Monday, March 26, 2007 - 5:13:33 PM
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Thomas Gorgues, Christophe E. Menkès, Olivier Aumont, Jérôme Vialard, Yves Dandonneau, et al.. Biogeochemical impact of tropical instability waves in the equatorial Pacific. Geophysical Research Letters, American Geophysical Union, 2005, 32, pp.L24615. ⟨10.1029/2005GL024110⟩. ⟨hal-00122343⟩



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