Description: Aerosol particle number concentrations have been measured at Halley and Neumayer on the Antarctic coast, since 2004 and 1984, respectively. Sulphur compounds known to be implicated in particle formation and growth were independently measured: sulphate ions and methane sulphonic acid in filtered aerosol samples and gas phase dimethyl sulphide for limited periods. Iodine oxide, IO, was determined by a satellite sensor from 2003 to 2009 and by different ground-based sensors at Halley in 2004 and 2007. Previous model results and midlatitude observations show that iodine compounds consistent with the large values of IO observed may be responsible for an increase in number concentrations of small particles. Coastal Antarctica is useful for investigating correlations between particles, sulphur, and iodine compounds, because of their large annual cycles and the source of iodine compounds in sea ice. After smoothing all the measured data by several days, the shapes of the annual cycles in particle concentration at Halley and Neumayer are approximated by linear combinations of the shapes of sulphur compounds and IO but not by sulphur compounds alone. However, there is no short-term correlation between IO and particle concentration. The apparent correlation by eye after smoothing but not in the short term suggests that iodine compounds and particles are sourced some distance offshore. This suggests that new particles formed from iodine compounds are viable, i.e., they can last long enough to grow to the larger particles that contribute to cloud condensation nuclei, rather than being simply collected by existing particles. If so, there is significant potential for climate feedback near the sea ice zone via the aerosol indirect effect.

Description: Halogens are highly efficient at destroying ozone in the stratosphere, and rising concentrations from human activities has led to depletion of global stratospheric ozone over the last three decades, and formation of the Antarctic “ozone hole”. It is also known that ozone depleting substances (ODSs) enter the stratosphere principally in the tropics, where ascending warm air carries them aloft. The EU-project SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) aims to reduce uncertainties in the amount of halogen-containing ODSs reaching the stratosphere, and the resulting ozone depletion, in a climate that is changing now, and which will change in the future. During the SHIVA field campaign on board RV Sonne in the South China Sea and Sulu Sea in November 2011, we investigated the potential of phytoplankton being a source for halocarbons emissions in detail by comparing collocated field samples. Phytoplankton parameters such as pigment concentration, functional group type, and PSII efficiency were undergoing a detailed analysis to investigate the relationship between phytoplankton and different halocarbon species. Significant (p 〈 0.05) relationships were observed between the cyanobacterial marker pigment zeaxanthin, the group of cyanobacteria without Prochlorococcus and methyl iodide (CH3I). In the vertical profiles, high concentration of bromoform was found to correspond to maximum chl a concentration (indicator of total phytoplankton biomass) and maximum 19-hexanoyl-fucoxanthin (the marker pigments for haptophytes) layers observed in depth between 20 to 60 m. These findings are based on statistical analysis based on Kendall’s rank correlations which examine the relationship between halocarbons, phytoplankton groups’ marker pigments and total chl a concentration. Also the relationship of phytoplankton groups and pigments to water temperature, salinity and surface winds only showed for salinity an inverse correlation to total chl-a and especially to cyanobacteria, but a bit weaker also to the other phytoplankton groups.