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The melting of sea ice samples is acknowledged to be deleterious to sympagic microorganisms due to the hypo-osmotic shock undergone by the organism when released from high salinity brine inclusions into the sample melt. Because melting of sea ice samples was also anticipated to modify the initial proportions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), three sample treatments were tested on an Antarctic sea ice sample, with the aim of identifying an efficient procedure that could routinely be applied for the determination of DMSO in sea ice. Herein, it was demonstrated that purging the melted sample before the determination of DMSO in the sample via an enzyme-linked method produced reliable DMSO results (215.8 +/- 8.9 nmol L-1, precision 4.1%). However, analysis revealed that the unintentional enzymatic cleavage of DMSP through the subsequent production of interfering DMS during melting caused an overestimation of the DMSO content in the sample by more than 59% and concurrently an underestimation of the DMSP content by approximately 9%. The sequential determination of DMSP after the DMSO determination by the enzyme-linked method was shown to be problematic. To circumvent all of these issues, we recommend an analytical procedure for the sequential determination of DMS, DMSP, and DMSO in sea ice. Ultimately, the first depth profile of DMSO at high resolution in sea ice was produced. The depth-integrated DMSO concentration in sea ice was determined to be 718 µmol m-2, which indicated that Antarctic sea ice is a potentially important source of DMSO for the Southern Ocean.

The Sea Ice Mass Balance in the Antarctic (SIMBA) experiment was conducted from the RVIB N.B. Palmer in September and October 2007 in the Bellingshausen Sea in an area recently experiencing considerable changes in both climate and sea ice cover. Snow and ice properties were observed at 3 short-term stations and a 27-day drift station (Ice Station Belgica, ISB) during the winter-spring transition. Repeat measurements were performed on sea ice and snow cover at 5 ISB sites, each having different physical characteristics, with mean ice (snow) thicknesses varying from 0.6 m (0.1 m) to 2.3 m (0.7 m). Ice cores retrieved every five days from 2 sites and measured for physical, biological, and chemical properties. Three ice mass-balance buoys (IMBs) provided continuous records of snow and ice thickness and temperature. Meteorological conditions changed from warm fronts with high winds and precipitation followed by cold and calm periods through four cycles during ISB. The snow cover regulated temperature flux and controlled the physical regime in which sea ice morphology changed. Level thin ice areas had little snow accumulation and experienced greater thermal fluctuations resulting in brine salinity and volume changes, and winter maximum thermodynamic growth of similar to 0.6 m in this region. Flooding and snow-ice formation occurred during cold spells in ice and snow of intermediate thickness. In contrast, little snow-ice formed in flooded areas with thicker ice and snow cover, instead nearly isothermal, highly permeable ice persisted. In spring, short-lived cold air episodes did not effectively penetrate the sea ice nor overcome the effect of ocean heat flux, thus favoring net ice thinning from bottom melt over ice thickening from snow-ice growth, in all cases. These warm ice conditions were consistent with regional remote sensing observations of earlier ice breakup and a shorter sea ice season, more recently observed in the Bellingshausen Sea.

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ������800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.