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FeCycle: attempting an iron biogeochemical budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters


Boyd, PW and Law, CS and Hutchins, DA and Abraham, ER and Croot, PL and Ellwood, M and Frew, RD and Hadfield, M and Hall, J and Handy, S and Hare, C and Higgins, J and Hill, P and Hunter, KA and LeBlanc, K and Maldonado, MT and McKay, RM and Mioni, C and Oliver, M and Pickmere, S and Pinkerton, M and Safi, K and Sander, S and Sanudo-Wilhelmy, SA and Smith, M and Strzepek, R and Tovar-Sanchez, A and Wilhelm, SW, FeCycle: attempting an iron biogeochemical budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters, Global Biogeochemical Cycles, 19, (4) Article GB4S20. ISSN 0886-6236 (2005) [Refereed Article]

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Copyright Statement

Copyright 2005 by the American Geophysical Union

DOI: doi:10.1029/2005GB002494


[1] An improved knowledge of iron biogeochemistry is needed to better understand key controls on the functioning of high-nitrate low-chlorophyll (HNLC) oceanic regions. Iron budgets for HNLC waters have been constructed using data from disparate sources ranging from laboratory algal cultures to ocean physics. In summer 2003 we conducted FeCycle, a 10-day mesoscale tracer release in HNLC waters SE of New Zealand, and measured concurrently all sources (with the exception of aerosol deposition) to, sinks of iron from, and rates of iron recycling within, the surface mixed layer. A pelagic iron budget (timescale of days) indicated that oceanic supply terms (lateral advection and vertical diffusion) were relatively small compared to the main sink (downward particulate export). Remote sensing and terrestrial monitoring reveal 13 dust or wildfire events in Australia, prior to and during FeCycle, one of which may have deposited iron at the study location. However, iron deposition rates cannot be derived from such observations, illustrating the difficulties in closing iron budgets without quantification of episodic atmospheric supply. Despite the threefold uncertainties reported for rates of aerosol deposition (Duce et al., 1991), published atmospheric iron supply for the New Zealand region is ∼50-fold (i.e., 7- to 150-fold) greater than the oceanic iron supply measured in our budget, and thus was comparable (i.e., a third to threefold) to our estimates of downward export of particulate iron. During FeCycle, the fluxes due to short term (hours) biological iron uptake and regeneration were indicative of rapid recycling and were tenfold greater than for new iron (i.e. estimated atmospheric and measured oceanic supply), giving an "fe" ratio (uptake of new iron/uptake of new + regenerated iron) of 0.17 (i.e., a range of 0.06 to 0.51 due to uncertainties on aerosol iron supply), and an "Fe" ratio (biogenic Fe export/uptake of new + regenerated iron) of 0.09 (i.e., 0.03 to 0.24).

Item Details

Item Type:Refereed Article
Keywords:biogeochemistry, iron cycle, dust deposition
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Boyd, PW (Professor Philip Boyd)
UTAS Author:Strzepek, R (Dr Robert Strzepek)
ID Code:147713
Year Published:2005
Web of Science® Times Cited:96
Deposited By:Australian Antarctic Program Partnership
Deposited On:2021-11-11
Last Modified:2021-12-03
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