The export flux of particulate organic carbon derived from 210Po∕210Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise

Type Article
Date 2019-01
Language English
Author(s) Tang Yi1, 2, Lemaitre Nolwenn3, Castrillejo Maxi4, 5, Roca-Martí Montserrat5, 6, Masqué Pere5, 7, Stewart Gillian1, 2
Affiliation(s) 1 : Earth and Environmental Sciences, the Graduate Center, City University of New York, New York, USA
2 : School of Earth and Environmental Sciences, Queens College, City University of New York, Flushing, USA
3 : Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH-Zürich, Zürich, Switzerland
4 : Laboratory of Ion Beam Physics, ETH-Zürich, Otto Stern Weg 5, Zürich, 8093, Switzerland
5 : Institut de Ciència i Tecnologia Ambientals and Departament de Física, Universitat Autònoma de Barcelona, Barcelona, Spain
6 : Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
7 : School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, Western Australia, Australia
Source Biogeosciences (1726-4170) (Copernicus GmbH), 2019-01 , Vol. 16 , N. 2 , P. 309-327
DOI 10.5194/bg-16-309-2019
WOS© Times Cited 10
Note Special issue GEOVIDE, an international GEOTRACES study along the OVIDE section in the North Atlantic and in the Labrador Sea (GA01) Editor(s): G. Henderson, C. Jeandel, M. Lohan, G. Reverdin, and L. Bopp
Abstract

The disequilibrium between 210Po activity and 210Pb activity in seawater samples was determined along the GEOTRACES GA01 transect in the North Atlantic during the GEOVIDE cruise (May–June 2014). A steady-state model was used to quantify vertical export of particulate 210Po. Vertical advection was incorporated into one version of the model using time-averaged vertical velocity, which had substantial variance. This resulted in large uncertainties for the 210Po export flux in this model, suggesting that those calculations of 210Po export fluxes should be used with great care. Despite the large uncertainties, there is no question that the deficits of 210Po in the Iberian Basin and at the Greenland Shelf have been strongly affected by vertical advection. Using the export flux of 210Po and the particulate organic carbon (POC) to 210Po ratio of total (> 1 µm) particles, we determined the POC export fluxes along the transect. Both the magnitude and efficiency of the estimated POC export flux from the surface ocean varied spatially within our study region. Export fluxes of POC ranged from negligible to 10 mmol C m−2 d−1, with enhanced POC export in the Labrador Sea. The cruise track was characterized by overall low POC export relative to net primary production (export efficiency < 1 %–15 %), but relatively high export efficiencies were seen in the basins where diatoms dominated the phytoplankton community. The particularly low export efficiencies in the Iberian Basin, on the other hand, were explained by the dominance of smaller phytoplankton, such as cyanobacteria or coccolithophores. POC fluxes estimated from the 210Po∕210Pb and 234Th∕238U disequilibria agreed within a factor of 3 along the transect, with higher POC estimates generally derived from 234Th. The differences were attributed to integration timescales and the history of bloom events.

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How to cite 

Tang Yi, Lemaitre Nolwenn, Castrillejo Maxi, Roca-Martí Montserrat, Masqué Pere, Stewart Gillian (2019). The export flux of particulate organic carbon derived from 210Po∕210Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise. Biogeosciences, 16(2), 309-327. Publisher's official version : https://doi.org/10.5194/bg-16-309-2019 , Open Access version : https://archimer.ifremer.fr/doc/00485/59668/