The export flux of particulate organic carbon derived from 210Po/210Pb disequilibria along the North Atlantic GEOTRACES GA01 transect : GEOVIDE cruise
Tang, Yi (City University of New York. Queens College (USA))
Lemaitre, Nolwenn (ETH Zürich. Institute of Geochemistry and Petrology)
Castrillejo, Maxi (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Roca Martí, Montserrat (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Masqué Barri, Pere (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Stewart, G. (City University of New York. Queens College (USA))
Universitat Autònoma de Barcelona. Departament de Física

Fecha:	2019
Resumen:	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 (>1µm) 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 mmolCm−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.
Ayudas:	Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1588 Ministerio de Economía y Competitividad MDM2015-0552 Ministerio de Educación, Cultura y Deporte FPU/AP-2012-2901 Ministerio de Educación, Cultura y Deporte FPU/AP-2010-2510
Nota:	Unidad de excelencia María de Maeztu MdM-2015-0552
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Publicado en:	Biogeosciences, Vol. 16, Issue 2 (January 2019) , p. 309-327, ISSN 1726-4189

DOI: 10.5194/bg-16-309-2019

19 p, 4.0 MB

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