Southern Ocean CO 2 sink: the contribution of the sea ice

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Delille, B, Vancoppenolle, M, Geilfus, N-X, Tilbrook, B, Lannuzel, D, Schoemann, V, Becquevort, S, Carnat, G, Delille, D, Lancelot, C, Chou, L, Dieckmann, GS, Tison, J-L
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley-Blackwell Publishing, Inc. 2014
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; Antarctic; Southern Ocean; The Antarctic; Antarc*; Sea ice
• Online Access: https://doi.org/10.1002/2014JC009941; http://ecite.utas.edu.au/100403

We report first direct measurements of the partial pressure of CO 2 (pCO 2 ) within Antarctic pack sea ice brines and related CO 2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO 2 large oversaturation, relative to the atmosphere, to a marked undersaturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO 2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals, and net primary production. As the ice warms, its permeability increases, allowing CO 2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO 2 . We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean and provide first estimates of spring and summer CO 2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea ice cover is a net sink of atmospheric CO 2 of 0.029 Pg C, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO 2 of the Southern Ocean.