Carbon export fluxes and export efficiency in the central Arctic during the record sea-ice minimum in 2012 : a joint 234Th/238U and 210Po/210Pb study
Roca Martí, Montserrat (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Puigcorbé Lacueva, Viena (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Rutgers van der Loeff, Michiel M. (Alfred-Wegener-Institut für Polar- und Meeresforschung)
Katlein, Christian (Alfred-Wegener-Institut für Polar- und Meeresforschung)
Fernández Méndez, Mar (Alfred-Wegener-Institut für Polar- und Meeresforschung)
Peeken, Ilka (Alfred-Wegener-Institut für Polar- und Meeresforschung)
Masqué Barri, Pere (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)

Data:	2016
Resum:	The Arctic sea-ice extent reached a record minimum in September 2012. Sea-ice decline increases the absorption of solar energy in the Arctic Ocean, affecting primary production and the plankton community. How this will modulate the sinking of particulate organic carbon (POC) from the ocean surface remains a key question. We use the 234Th/238U and 210Po/210Pb radionuclide pairs to estimate the magnitude of the POC export fluxes in the upper ocean of the central Arctic in summer 2012, covering time scales from weeks to months. The 234Th/238U proxy reveals that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m−2 d−1) in late summer. Relationships obtained between the 234Th export fluxes and the phytoplankton community suggest that prasinophytes contributed significantly to the downward fluxes, likely via incorporation into sea-ice algal aggregates and zooplankton-derived material. The magnitude of the depletion of 210Po in the upper water column over the entire study area indicates that particle export fluxes were higher before July/August than later in the season. 210Po fluxes and 210Po-derived POC fluxes correlated positively with sea-ice concentration, showing that particle sinking was greater under heavy sea-ice conditions than under partially ice-covered regions. Although the POC fluxes were low, a large fraction of primary production (>30%) was exported at the base of the euphotic zone in most of the study area during summer 2012, indicating a high export efficiency of the biological pump in the central Arctic.
Ajuts:	Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-1356 Ministerio de Ciencia e Innovación CTM2011-2845-2 Ministerio de Educación, Cultura y Deporte AP2010-2510 Ministerio de Educación, Cultura y Deporte AP2009-4733
Nota:	Unidad de excelencia María de Maeztu MdM-2015-0552
Nota:	Altres ajuts: M.R.-M. and V.P. were supported by Spanish PhD fellowships (AP2010-2510 and AP2009-4733, respectively).
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Publicat a:	Journal of geophysical research: oceans, Vol. 121 issue 7 (July 2016) , p. 5030-5049, ISSN 2169-9291

DOI: 10.1002/2016JC011816

20 p, 3.1 MB

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