Collaborative Research: Southern Ocean Iron Experiments (SOFeX)

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ABSTRACTOCE-9911481, OCE-0000364, OCE-0000365, OCE-0000363, OCE-0000362, OCE-0000361In recent years, studies of dissolved iron in the ocean and the results of open-ocean iron enrichments experiments have demonstrated that the growth and biomass of phytoplankton are limited by low concentrations of available iron in waters characterized by high concentrations of dissolved nitrate and low standing stocks of chlorophyll ("HNLC waters"). The seminal open-water iron fertilization experiments were done in the early 1990's in the eastern equatorial Pacific Ocean. Since that time, abundant new evidence has come to light that an even more extensive, and globally significant, HNLS region exists in the broad eastwardly flowing Southern Ocean surrounding Antarctica.In this project, researchers at the Moss Landing Marine Laboratory, Rutgers University, Oregon State University, University of Miami, and Lamont-Dougherty Earth Observatory will perform an open-water iron fertilization experiment in the Southern Ocean in regions just north of and just south of the Antarctic Polar Frontal Zone (APFZ) along 170W, an area characterized by high major nutrients and extremely low dissolved iron concentrations. The team will investigate (1) the role of iron on the biological pump in silicate-rich versus silicate-poor HNLC waters, (2) iron mediation of differential drawdown of major nutrients, (3) iron limitation of carbon fixation and export from surface waters, (4) the biophysical response to added iron, and (5) the potential effect of iron-induced carbon export on midwater remineralization and denitrification. The underlying hypothesis driving this field study is that the rate of phytoplankton production and the quantity of plant biomass in the Southern Ocean are differentially limited across the APFZ by iton and silicate availability during the major growth season and are responsible for the persistence of the HNLC condition. The results of this work are expected to contribute significantly to our understanding of important biogeochemical processes in the Southern Ocean. Factors that control the rate of new production bear directly on the global carbon cycle, atmospheric carbon dioxide concentration, and climate control.This Southern Ocean Iron Experiment (SOFeX), north and south of the APFZ, will be carried out in a single field expedition in the austral summer of 2001-2002.