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Sea Ice CO2 Dynamics Across Seasons: Impact of Processes at the Interfaces

F. van Der Linden 1 Jean-Louis Tison 2 W. Champenois 1 S. Moreau 3 Gautiher Carnat 2 M. Kotovitch 1, 2 François Fripiat 2 F. Deman 1, 4 A. Roukaerts 4 F. Dehairs 4 S. Wauthy 2 Antonio Lourenço 5 Frédéric Vivier 6 T. Haskell 7 Bruno Delille 1 
1 Unité d'Océanographie Chimique
MARE - Interfacultary Center for Marine Research
5 DITM - Développement Instrumental et Techniques Marines
LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
6 PROTEO - Processus et interactions de fine échelle océanique
LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
Abstract : Winter to summer CO2 dynamics within landfast sea ice in McMurdo Sound (Antarctica) were investigated using bulk ice pCO2 measurements, air‐snow‐ice CO2 fluxes, dissolved inorganic carbon (DIC), total alkalinity (TA), and ikaite saturation state. Our results suggest depth‐dependent biotic and abiotic controls that led us to discriminate the ice column in three layers. At the surface, winter pCO2 supersaturation drove CO2 release to the atmosphere while spring‐summer pCO2 undersaturation led to CO2 uptake most of the time. CO2 fluxes showed a diel pattern superimposed upon this seasonal pattern which was potentially assigned to either ice skin freeze‐thaw cycles or diel changes in net community production. In the ice interior, the pCO2 decrease across the season was driven by physical processes, mainly independent of the autotrophic and heterotrophic phases. Bottom sea ice was characterized by a massive biomass build‐up counterintuitively associated with transient heterotrophic activity and nitrate plus nitrite accumulation. This inconsistency is likely related to the formation of a biofilm. This biofilm hosts both autotrophic and heterotrophic activities at the bottom of the ice during spring and may promote calcium carbonate precipitation.
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https://hal.archives-ouvertes.fr/hal-03035303
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Submitted on : Wednesday, June 22, 2022 - 4:39:42 PM
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F. van Der Linden, Jean-Louis Tison, W. Champenois, S. Moreau, Gautiher Carnat, et al.. Sea Ice CO2 Dynamics Across Seasons: Impact of Processes at the Interfaces. Journal of Geophysical Research. Oceans, Wiley-Blackwell, 2020, 125 (6), ⟨10.1029/2019jc015807⟩. ⟨hal-03035303⟩

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