The production of ozone-depleting bromocarbon gases in near-shore Antarctic waters

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There is a continual two-way exchange of chemicals between the sea-surface and the atmosphere. The bromocarbons are a group of volatile compounds that are produced naturally in seawater and carry the element, bromine from the ocean reservoir in to the atmosphere. Once in the atmosphere bromine has an important influence on the chemistry taking place there. The major impact of this flux is a reduction in the amount of ozone in the air, which can reduce the potential for the breakdown of harmful greenhouse gases and lead to an increase in the amount of harmful UV light reaching the Earth's surface. Understanding how, when and where these bromocarbon compounds are produced in the marine environment is essential to allow us to predict their impact on the Earth's system. Results from our recent study in the Antarctic show that the bromocarbon compounds bromoform (CHBr3) and dibromomethane (CH2Br2) are produced during a phytoplankton bloom that occurs as the sea-ice breaks up during the summer months (October to May). Blooms such as the one we studied occur all along the area of the Antarctic known as the Western Antractic Peninsula during the summer. If bromocarbon production occurs in all of these blooms, there could be a large sea-to-air flux of bromine during the Antarctic summer which could have an important influence on atmospheric chemistry. In this study, we propose to identify the main biological, chemical and physical processes influencing bromocarbon concentrations in the sea-ice edge phytoplankton blooms and use this knowledge to estimate the potential impact of sea-air bromine flux using mathematical models.