| Summary: | We studied the temporal variations of CO 2 , O 2 , and dimethylsulfide (DMS) concentrations within three environments (sea-ice brine, platelet ice-like layer, and underlying water) in the coastal area of Adelie Land, Antarctica, during spring 1999 before ice breakup. Temporal changes were different among the three environments, while similar temporal trends were observed within each environment at all stations. The underlying water was always undersaturated in O 2 (around 85%) and oversaturated in CO 2 at the deepest stations. O 2 concentrations increased in sea-ice brine as it melted, reaching oversaturation up to 160% due to the primary production by the sea-ice algae community (chlorophyll a in the bottom ice reached concentrations up to 160 µg L -1 of bulk ice). In parallel, DMS concentrations increased up to 60 nmol L -1 within sea- ice brine and the platelet ice- like layer. High biological activity consumed CO 2 and promoted the decrease of partial pressure of CO 2 (pCO 2 ). In addition, melting of pure ice crystals and calcium carbonate (CaCO 3 ) dissolution promoted the shift from a state of CO 2 oversaturation to a state of marked CO 2 undersaturation (pCO 2 < 30 dPa). On the whole, our results suggest that late spring land fast sea ice can potentially act as a sink of CO 2 and a source of DMS for the neighbouring environments, i.e., the underlying water or/ and the atmosphere.
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