Carbon cycling dynamics in the seasonal sea-ice zone of East Antarctica

The carbon cycle of the seasonally ice covered region of the southwest Indian Ocean sector of East Antarctica (30°–80°E, 60°–69°S) was investigated during austral summer (January–March 2006). Large variability in the drivers and timing of carbon cycling dynamics were observed and indicated that the study site was a weak net source of carbon dioxide (CO₂) to the atmosphere of 0.8 ± 1.6 g C m⁻² during the ice-free period, with narrow bands of CO₂ uptake observed near the continental margin and north of the Southern Antarctic Circumpolar Current Front. Continuous surface measurements of dissolved oxygen and the fugacity of CO₂ were combined with net community production estimates from oxygen/argon ratios to show that surface heat gain and photosynthesis were responsible for the majority of observed surface water variability. On seasonal timescales, winter sea-ice cover reduced the flux of CO₂ to the atmosphere in the study area, followed by biologically driven drawdown of CO₂ as the ice retreated in spring-summer highlighting the important role that sea-ice formation and retreat has on the biogeochemical cycling of the region.