SOFeX Proposal Abstracts

Contributed: February 2006 by cchandler (OCB DMO, WHOI)
downloaded from NSF Web site http://www.nsf.gov

Collaborative Research: Southern Ocean Iron Experiments (SOFeX)
PI: Kenneth Coale

Program Manager	Donald L. Rice OCE Division of Ocean Sciences GEO Directorate for Geosciences
Start Date	January 1, 2001
Investigator(s)	Kenneth Coale coale@mlml.calstate.edu (Principal Investigator)
Sponsor	San Jose State University Foundation Post Office Box 720130 San Jose, CA 95172 408/924-1400
NSF Program(s)	CHEMICAL OCEANOGRAPHY

Abstract:  OCE-9911481, OCE-0000364, OCE-0000365, OCE-0000363, OCE-0000362, OCE-0000361

In 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.

 

Particle Export during the Southern Ocean Iron Experiment (SOFeX)
PI: Ken Buesseler

Program Manager	Donald L. Rice OCE Division of Ocean Sciences GEO Directorate for Geosciences
Start Date	August 1, 2001
Investigator(s)	Ken Buesseler kbuesseler@whoi.edu (Principal Investigator)
Sponsor	Woods Hole Oceanographic Institution
NSF Program(s)	CHEMICAL OCEANOGRAPHY

Abstract:  OCE-9987501

While it has been shown that the addition of Fe can stimulate phytoplankton growth and alter upper ocean biogeochemistry, little is know about the net effect of Fe availability on sinking particle fluxes. If Fe played an important role in past variations in CO2 or if there will be long term effects of Fe on CO2 due to deliberate manipulation of ocean ecosystems, then it becomes essential to quantify the net change in export fluxes of carbon and associated elements in response to Fe loading. For this reason, the PI will quantify changes in particulate organic carbon and particulate organic nitrogen export during the Southern Ocean Iron Experiment (SOFeX) using the naturally occurring radionuclide thorium-234. Using time-series profiles of 234Th obtained both inside and outside of the SOFeX study area, the PI will be able to study the export response to changes in Fe loading and community structure, as well as assist in the calculation of the carbon and nutrient fluxes in response to the Fe additions. Information on the export response of the upper ocean to Fe enrichment will be used to understand past oceanic responses to Fe/dust inputs and assess future impacts of deliberate Fe fertilization proposed to offset carbon dioxide emissions.