Early winter barium excess in the southern Indian Ocean as an annual remineralisation proxy (GEOTRACES GIPr07 cruise)

International audience The Southern Ocean (SO) is of global importance to the carbon cycle, and processes such as mesopelagic remineralisation that impact the efficiency of the biological carbon pump in this region need to be better constrained. During this study early austral winter barium excess (...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: René van Horsten, Natasha, Planquette, Hélène, Sarthou, Géraldine, James, Thomas, Lemaitre, Nolwenn, Mtshali, Nicholas, Roychoudhury, Alakendra, Bucciarelli, Eva
Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-17-EURE-0015,ISBlue,Interdisciplinary Graduate School for the Blue planet(2017)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2022
Subjects:
barium
biological pump
mesopelagic zone
primary production
remineralization
remote sensing
winter
[SDE]Environmental Sciences
Austral
Indian
Southern Ocean
Online Access:https://hal.science/hal-04159458
https://hal.science/hal-04159458/document
https://hal.science/hal-04159458/file/Early%20winter%20barium%20excess%20in%20the%20southern%20Indian%20Ocean.pdf
https://doi.org/10.3389/fmars.2022.902772
Description
Summary:International audience The Southern Ocean (SO) is of global importance to the carbon cycle, and processes such as mesopelagic remineralisation that impact the efficiency of the biological carbon pump in this region need to be better constrained. During this study early austral winter barium excess (Baxs) concentrations were measured for the first time, along 30gE in the southern Indian Ocean. Winter Baxs concentrations of 59 to 684gpmolg L-1 were comparable to those observed throughout other seasons. The expected decline of the mesopelagic Baxs signal to background values during winter was not observed, supporting the hypothesis that this remineralisation proxy likely has a longer timescale than previously reported. A compilation of available SO mesopelagic Baxs data, including data from this study, shows an accumulation rate of g1/40.9g molgm-2g d-1 from September to July that correlates with temporally integrated remotely sensed primary productivity (PP) throughout the SO from data spanning g1/420 years, advocating for a possible annual timescale of this proxy. The percentage of mesopelagic particulate organic carbon (POC) remineralisation as calculated from estimated POC remineralisation fluxes over integrated remotely sensed PP was g1/42-fold higher south of the polar front (19g 15g%, nCombining double low line39) than north of the polar front (10g 10g%, nCombining double low line29), revealing the higher surface carbon export efficiency further south. By linking integrated remotely sensed PP to mesopelagic Baxs stock, we could obtain better estimates of carbon export and remineralisation signals within the SO on annual and basin scales. © Author(s) 2022.

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