Southern Ocean CO2 sink: The contribution of the sea ice

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Delille, Bruno, Vancoppenolle, M, Geilfus, N.-X., Tilbrook, B., Lannuzel, D., Schoemann, V., Becquevort, S., Carnat, G., Delille, D., Lancelot, C., Chou, L., Dieckmann, G., Tison, J.-L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Antarc*; Antarctic; Sea ice; Southern Ocean
• Online Access: https://orbi.uliege.be/handle/2268/171561; https://orbi.uliege.be/bitstream/2268/171561/1/Sea-ice%205.2.pdf; https://doi.org/10.1002/2014JC009941

peer reviewed We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large over-saturation, relative to the atmosphere, to a marked under-saturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate minerals crystals and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea-icesea ice cover using the NEMO-LIM3 large-scale sea ice-ocean, and provide first estimates of spring and summer CO2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea-icesea ice cover is a net sink of atmospheric CO2 of 0.029 PgC, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean. Belcanto - Bigsouth