Particle fluxes associated with mesoscale eddies in the Sargasso Sea
Date
2007-09-25Author
Buesseler, Ken O.
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Lamborg, Carl H.
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Cai, Pinghe
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Escoube, Raphaelle
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Johnson, Rodney J.
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Pike, Steven M.
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Masqué, Pere
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McGillicuddy, Dennis J.
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Verdeny, Elisabet
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https://hdl.handle.net/1912/2349As published
https://doi.org/10.1016/j.dsr2.2008.02.007Keyword
Oceanic eddies; Particle flux; Thorium-234Abstract
We examined the impact of a cyclonic eddy and mode-water eddy on particle flux in the
Sargasso Sea. The primary method used to quantify flux was based upon measurements of the
natural radionuclide, 234Th, and these flux estimates were compared to results from sediment
traps in both eddies, and a 210Po/210Pb flux method in the mode-water eddy. Particulate organic
carbon (POC) fluxes at 150m ranged from 1 to 4 mmol C m-2 d-1 and were comparable between
methods, especially considering differences in integration times scales of each approach. Our
main conclusion is that relative to summer mean conditions at the Bermuda Atlantic Time-series
Study (BATS) site, eddy-driven changes in biogeochemistry did not enhance local POC fluxes
during this later, more mature stage of the eddy life cycle (>6 months old). The absence of an
enhancement in POC flux puts a constraint on the timing of higher POC flux events, which are
thought to have caused the local O2 minima below each eddy, and must have taken place >2
months prior to our arrival. The mode-water eddy did enhance preferentially diatom biomass in
its center where we estimated a factor of 3 times higher biogenic Si flux than the BATS summer
average. An unexpected finding in the highly depth resolved 234Th data sets are narrow layers of
particle export and remineralization within the eddy. In particular, a strong excess 234Th signal is
seen below the deep chlorophyll maxima which we attribute to remineralization of 234Th bearing
particles. At this depth below the euphotic zone, de novo particle production in the euphotic
zone has stopped, yet particle remineralization continues via consumption of labile sinking
material by bacteria and/or zooplankton. These data suggest that further study of processes in
ocean layers is warranted not only within, but below the euphotic zone.
Description
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1426-1444, doi:10.1016/j.dsr2.2008.02.007.
Suggested Citation
Preprint: Buesseler, Ken O., Lamborg, Carl H., Cai, Pinghe, Escoube, Raphaelle, Johnson, Rodney J., Pike, Steven M., Masqué, Pere, McGillicuddy, Dennis J., Verdeny, Elisabet, "Particle fluxes associated with mesoscale eddies in the Sargasso Sea", 2007-09-25, https://doi.org/10.1016/j.dsr2.2008.02.007, https://hdl.handle.net/1912/2349Related items
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